CA2092495C - Communication system - Google Patents

Abstract

At the transmitter side, carrier waves are modulated according to an input signal for producing relevant signal points in a signal space diagram. The input signal is divided into, two, first and second, data streams. The signal points are divided into signal point groups to which data of the first data stream are assigned. Also, data of the second data stream are assigned to the signal points of each signal point group. A difference in the transmission error rate between first and second data streams is developed by shifting the signal points to other positions in the space diagram. At the receiver side, the first and/or second data streams can be reconstructed from a received signal. In TV
broadcast service, a TV signal is divided by a transmitter into, low and high, frequency band components which are designated as a first and a second data stream respectively.
Upon receiving the TV signal, a receiver can reproduce only the low frequency band component or both the low and high frequency band components, depending on its capability.

Description

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SPECIFiCATION
TITLE OF T~ INVENTION
Communication SYstem ~ ACKGRI~I)N~ OF T~ V~NTION
1. Field of the I~vention:
The pressnt invention rslates to a communic~tion system for transmission/receptlon of a di~ital 6ignal through modulation of itB carrier wave and demodulation of the modu~ ted si gnal.
1~ 2. Deecription of the Prior Art:
Digi.tal c~ tn jcati~n sy8tems have been used in va~ious fialds. Particularly, digital video signal tran6Lis6ion techniques have ~een improved re~arkably.
Among them is a dlgital TV si~nal trans~ission ~ethod.
So fur, such digital TV sign~l transmission system are in particular use for e.~. tra~smission betwe~n TV stations.
They will soon be utilized for terrestrial and/~r satellite broadca~t ~ervice in every country of thc world.
The TY bro~dcast systems including HDTV. PCM music, FAX, and other info~mation 6ervice aro now de~anded to increase desired datR in guantity and quality for satisfying m~ llions of sophisticated viewers. In particular, th~ data has to be incressed in a given band~idth of frequency allocated for TV
broadcast service. The data to be ~ran~mitted is always 2~ abundant snd provided as ~uch as haJldled with up-to-date techniques of the time. Lt is ideal to modify or change the e~isting signal transmi6sion system corr~spordi~g to an 209249~i increase in the data amount wi~h ~ime.
However, the T~ broadcast service is a publlc business and rannot go f~rther without consi~ering the intere6ts and benefits of viewer~, It is essential to have an~ new service 5 ~ppreri~ble with e~isting TV recei~er6 ard ~i8pl~y6. More partic~larly, the compatibility o~ a system i~ much desired for provlding both old and new se~vices simultaneously or one new 6ervice which can be intercepted by either of the P,~i6ti~g and adva~ced recei~ers, It i8 understood that any ne~ digital rv broadcast system to be introduced has to bs arranged fDr data e~tension in order to respond to future de~andc and techllological advanta~es and al80, for compatible action to ~llow the e~ist;ing receivers to receive ~rans~issions, The e~pansion capability ~nd compatible performance o~
prior art digital TV sy6tem will be e~plained.
A digltal satellite TV system i~ ~nown in which NTSC TV
signals co~pressed to an about 6 Mbps are multiple~ed by time division ~odulation of 4 PSK and tran6mitted on 4 to 20 chsnnels whi~e HDTV signals are carried on B single channel, ,~nothrr digitQl HDTV s~6tem is provided in which HDTV video data compres~ed to as small a9 1~ M~s are transmitted on a 16 or 32 Q~M signal thro~gh ground stations.
Such a known satellite system permits ~DTV signals to be carried on one channel by a conve~tional manner, thus occupying a band of frequencies equivalent to s~me channels of ~TSC sign~ls. This causes the correspon~ing ~TSC ch.annels . .~ ~,~ ~3 ~ 7~ ~t~
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to be unav~ilable during tran~mission of the ~DTV signal.
~lso, the co~patibility between NTSC and HDTV recelvers or displays is hardly concerned and data ~pansion capability needed for matching a future advAnc~d mode is utterly disregarded.
Suc.h a common terr~strial HDTV system offers a~ HDTV
service on conventional 16 or 32 QAM signals without any modification. In any analogue T~broadcast servicel there are d~veloped a lot of ~i.gnal attenuating or sha~ow regions within its ~ervl~e area due to structural obstacle~, geographical inconveniences, or signul interferen~e from a neighbor Bt~tion, When the T~ signal is an analogue form, it can be i~ltercepted more or le~s at such signal attenuatir.
regions althou~h it~ reproduced picture is low in quality. if TV signal is A digital form, it can rarely be reproduced at an acceptable level within the regions. Thi~ disadvantage is critically hostile to the devslopment of any digital T~r system.
This problem is caused due to the fact that the cor~ventional modulation ~ystem~ such ~AM arran8e the signal points at constant intervals. There have been no such systems that can change or modulate the arrangement of si~nal points.

SUM~ARY OF ~HE INVE~TION
It is ~n object of the present invention, for solving the foregoing di~Qdvantages, to provide a communication system arranged for co~patible use for both the existing ~TSC

ar~ introducin~ HDTV broadcast ser~ices, particularly vla satellite and also, for mini~i~i~g signal attenuatin~ or shadow regio~s of it6 service area on the grounds.
A co~uniration syste~ according to the present invent~on intentionally varie~ signal points, which used to be disposed at uniform intervals, to perform the signal trans~ission~reception For ex~mpl~, if applied to a QAM
signal, the communication ByStem comprises two major section~: a $ran~mitter havi~g a signal in~ut clrcuit, modulator circuit for producing m numbers o~ ~ignal points, in a signal vector field through modulation of a plurality of out-of-~hase carrier waves using an input ~i~nal supplied from the l~put circuit, and a transmit~er cir~uit for transmittin~ a resulta~t modul3ted signal; and a receiver having an input circuit for recelving the modulated signal, a demoduls~or circuit for demodulating one-hit signal points of a QAM carrier ~ave, and an output circuit.
In oper~tion, the inp~t signal containing a first data stream of n values ~nd a second data stream is fed to the modulator circult of the transmitter where a modified m-bit QAM carrier wave is produccd repre~enting m sig~al points in a vector ~ield. The ~ signQl po;nts are divided into n sign~l point groups to which th~ n v~lues Gf thP first data stream are assi~ned respec~ively. Also, d~ta of the second data stre~m ar~ assigned to m~r sign~1 points or sub gl'OUpS ol each signal point group. Thcn, a res~ltan~ transmission sign~l is transmit~ed ~rom the tr~n~ltter cir~uit.

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Similarly, a third dsta stre~m can ~e Fropagated.
At th~ p-bit demodulator circuit, p>m, of the receiver.
the first data str~a~ of the transmission signal is first demodulated through dividi~g p signal points in a signal sp~ce diagram into n si~nal point groups. Then, the second . data strea~ is demodulated through assigning p/n values ta p~n sign~l points of each correspondi~g qignal point group for reconstruction of both the f~rst and second data streams.
If the receiver is at P=n, the n signal point groups are reclaimed and aqsigned the n value~ for demodulation ~nd reconstructlon of the first datn stream.
Upon receiving the same trans~ission s~nul from the trans~itter, a recelver equipped with a large sized antenna sDd capable of large-~ata modulation can reproduce both the 16 first and second data s~reams. A receiver equipped with a ~all si~ed antenna and càpable of s~all-data modulation can reproduce the first data stream onlY. Accordirlgly, the compatibility of the signal tr~nsmis6ion syst2m will be ensured. When the fir~t data s~ream is An NTSC TV si~nal Dr low frequency band co~ponent of an HDTV sig~l and the second data strea~ i9 a hi~h frequency ba~d component of the ~DTV
signQl, the emall-data ~odulation receiv&r can reconstruct the NTSC TV si~nal and the large-data modulation receiver can reco~struct the HDTV signal, As understood, a digital 2S ~TSCJHD~V si~ultaneo~sly broadcast service will be feQsible using the compatibility OI th~ signal transmission system of the present lnvention.

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More ~pecifically, the co~munication syste~ of the pre~ent invention comprise~: a transmitter having a signal input circuit, a modulator cirouit for producing ~ signal point~, in a signal ve~tor fie]d through modul~tion of a plurnlity o~ out-of-phaRe carrier wave6 using an input signal supplied fro~ the input, and a trans~itter cirr.uit for trans~itting a resultant modulated signal, in which the main procedure includes re-eiving an inp~t signal contalning a first dat~ stream of n values and a second data stream, dividin~ the m signal points of ti-e ~ignal i~}to n signal point groups, assigning the n values of the f-rst data stream ~o the n 8ignal point groups respectively, ASSigning dat~ of tha second data stream to the slgnal point6 of each signal po.nt ~roup refipectively~ and transLitting the re~ultant 1~ modulated signal; and a receiver having an lnput clrcuit for receivin~ the modulated signal, a demodulator circuit for demodulatin~ p signal points of a QAN carrier wave, and an ou~ut circuit, in which the main procedure includes dividing the p ~ignal points into n ~ignal point groups, demodulati~
th~ fir~t dat~ streAm of which n values are assigned to the n sl~nal point ~roups respectively, and demodulating the second ~ata stream of which p/n values are assi~ned to p/n signal points of each sign~l point group respectively. For e~ample, a transmitter 1 produces a modified m-bi~ QAM sig~al of which first, second. a~d third data strea~s, each carrying n val~es~ are assigned to relevart 6ignal point groups with a modulator 4. The signal can be intercepted and repruduced ~ ~9~ 3.~ 5 ~ 1 ?6', 1 9'} j r;~ u.; 3~ ' J-209249~
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the first data strea~ only by a first receiver 23, both the f iret and second data streams by a second receiver 33, and all the f;r~t, second, and third ~treams by a third receiver 43.
More partieularly, a receiver capable of demodulation of n-bit data can reproduce n bits fro~ a ~ultiple-bit modulated earrier ~ave carrying arl m-bit d~ta where m>n, thu~ allowin~
the co~m~nication system to have compatlbility and capability of future e~ten~ion~ Al~o, a multi-level signa1 transmission will be po~sible by ~h~fting the signal points of QAM ~o that a nearest ~ignal point to the origi~ point ~f I~axi~ an~ Q-a~is coordinate~ paced nf ~rom the origin where f is the di6tance of the nearest point f~om eaeh axis and n i8 mor0 than 1.
Accordingl~, a co~patible digitsl satellite broadcast service for both the NTSC and ~DTV s~stem6 will be fe~sible whe~ the first data stream carries an NTSC 6ignal and the second data ~tream carries a diffErence sign~l bstween ~TSC
and HDTV. Hence, the capability of corresponding to an increase in the data amount to be transmitted will be e~sured. Also, at the ~round, its service area will be increased while si~nal attenuating areas are decreased.

B~IEI' ~ESC~IPTION OF THE ~RAWINGS
Fig. 1 is a sche~atic Yiew o~ the entire arran~ement of a signal transmission system showing a first embodiment of the present in~ention;

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Fi~. 2 is a block diagram of a transmitter of the fir8t e~bodimer~t;
Fig. 3 is a vector diaera~ 6howing a transmi~sion signal of the first e~bodiment;
Fig. 4 i5 Q vector di~gram showing a trans~is6ion 6ignal of the fir6t e~bodiment;
Fig. 5 i9 B view showing ar. afisignment of bin~ry codes to ~ignal points ~ccording to the Lirst embodi~e~t;
Fig. 6 i~ a view showing an a~signment of binary ~odPs to si~nal poirt groups according to the first embodi~ent;
~ ig. 7 iB d view showing an assigDment of binary codes to 6ignal points in each signal point group accor~ing to the first e~bodiment;
Fig. ~ is a vlew showi~g another assignme~t of binary codes to signal point groups and their signal points a~cording to the fir~t embDdiment;
~ ig. 9 i5 a view 6howing threshold valuefi of the signal point groups accordiI~g to the first ~mbodiment;
~ ig. 10 is a vector dia~ram of a modified 16 QAM signal of tne first embodime~t;
Fig. 11 i~ a graphic diagram showing the rel~tion betwean antenna radius r2 and trans~lssio~ enPrgy ratio n according to the first e~bodiment;
Fig. 12 is a view s~,owing the signal points of a modified 64 QAM signa1 o~ the fir~t ~mbodiment;
Fig. 13 is a graphic diagr~ sho~i~g the relation b~tween antennfi radius r3 and transmission energy ratio n 1 9 ~ r~ otD~ . ' 3 4 ~ , 3 !' ~
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accordi~g to the first embodiment;
Fig. 14 is a vector diagram showing signal point groups and their signal poi~ts of the modified ~ QAM signal nf the first ombodime~t;
~ 5 Fig. 15 is an explanatory vi~w ~howing tho relation betweerl Al and A~ o~ th~ ~od fi~d 64 CA~l signal oY the first embodimellt;
Fig. 16 is Q graph diagram sho~ing the relatlon betwecn antenna radius rz, r3 a~d tran6missio~ energy ratio nl6, n~
respecti~e~y according to the fir~t cmbodiment;
Fig~ 17 is a block diagram of a digital transmitter of the f i rst e~bodiment;
Fig. 18 is a signal space diagram of a 4 PSK mndulated signal of the first embodiment;
Fig. 19 is a block dia~ram o~ a fir~t recelver oP khe fir6t e~bodiment;
Fig. 20 is a signal space diagra~ of ~ 4 PS~ modulated signal of the first e~bodiment;
Fig. 21 is a block diagram of a second receiver of the first eIbodiment;
Fi~. 22 i~ a v~ctor diagra~ of a modified 16 QAM si~nRl of the first e~bodiment;
Fig. 23 is a vcctor diagram of a modifi~d 64 QAM si~nal of the first embodiment;
~ig. 2~ is a flow chart showing an aetion of the first embodiment;
Figs. 25(a) and 25(b) are vector diagrams showing an 8 3¢ q 5~ , .. ?~1~
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~nd a 16 QA~S signal of the f irst embodiment respectivel~;
Fig. 26 is a block diagram of a third rece~ver of the first em~odiment;
~ ig. 27 is a view 6ho~ing signal points of the modified 64 4AM signa~ oE the fir~t embodiment:
Fig. 28 i6 ~ flow chart showing another action of the first embodi~ent;
Fig. 29 is a ~chematic view o~ the entire arr~nge~ent of a ~ign~l transmis~ion syste~ showin~ a third embodiment of the pre~ent irventlon;
Fig. 30 is a block diagra~ of a first vidco e.ncoder of the third embodiment;
~ ig. 31 is a blooX diagram of a first ~ideo d~coder of the third embodim~r.t, Fig 32 is a block diagram of a second video decod~r of the third embodiment;
Fig. 33 i~ ~ block diagram of a third video decoder of the third embodiment;
Fig. 34 is ~n expl~natory ~iew ~howin~ a time multiplexing of D1, Dz, and D3 signals according to the third em~odiment;
Fig. 35 is al~ explanatory view sho~-ing an~h~r time multiple~ing of the Dl, D2, and D3 signals according to the third e~bodimemt;
Fig. 36 i~ an explanatory vlew showing a further time multi~lexing of the D1, D2, and D3 signals accordi~g to the ~hird e~bodiment;

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F.g. 37 is a schematic view of the entire arr~nge~ent of a signal transmission system showing a fourth embodi~Pn-b of the pI~sent inventiun;
Fig. 38 is a vect~r dia8ram of a modified 16 QAM 6ignal 5 o~ the third e~bDdiment;
Fi8. 39 is a vector di~ram of the modified 1~ QAM
6i~nal of the third e~bodiment;
F.ig. 40 is a vsctor disgram of a modifled 64 ~AM signal oF the third e~bodiment;
Fig. 41 is a diagr~m of as6ignment o~ data component~ on a time base according to the third embodlment;
Fig. 42 is a diagram of ~ssignment of data c~mponents un a time base in TDMA a~tion accordin~ to the third embodi~ent;
Fig. 43 is a block diagram of a c~rriar reproducing circuit of the third embodi~ent;
~ig. 44 is a diagram shDwing the princlple of carrier wav~ reproduction according to the third embodimerlt;
Fig. 45 is a bl~ck di~gram of A rarrier reprodu~ing circuit for reverse modulation of ths third embodi~ent;
Fig. 46 is a dingram showing an assignment of signal point6 of tho 16 QAM sign~l of the third embodimsnt;
Fig. 47 is a di~gram showing An aBsi~n~lent of ~ig~al poin~s of the ~4 QAM signAl of the third embodiment;
Fig. 48 is ~ block diagram of a c~rrier reprodu~ing circu't for 1~x ~ultipiication of the third embudiment;
Fig. 49 i~ an explanatory view showing a time multiplexing of D~ Dv2. D~, DV3, and D~ sign~ls According . ~ 3 ~~ L 1 a ~ M ~ . u ~ . ! . 3 u ~
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to the third embodi.ment;
Fig. 50 is an expl~Datory view showlng a TD~A time P ng of ~1' DHI~ Dy2- D~ D~3, ~lld D~3 signQls according Lo the third embodimell-t;
Fig. 51 is an explanatory view showing arlother T~MA time ~ultiplexi~g of th~ D~l, Dhl, DV2, D~, ~3, and 0~ 6ignals according to the third e-mbodiment;
Fig. 52 is a diagram showlng a sig~al interfercnce region in a known trans~lseion method arcording to the fourth em~odiment;
Fig. 53 is ~ dia~ram showing signal i~terference regions in a multi-level ~ignal transmis6ion ~ethod according ~o the fourth embodlmant;
Fig. 54 is a diagram showing signal attenuating regions in the known tra~smission m~thod acoordi~ to the fourth embodimerlt;
Fig. 55 i~ a dia~ram showing sig~al attenuating re~ion6 in the multi-level sig~lal tr~nsmission method according to the fourth embodiment;
Fig. 56 is a diagram showing a signsl interference re~ian between two digltal TY stations accordin~ tn the fourth e~bodiment;
Fig~ 57 i6 a diagram showing an assignment of signal points of a modified 4 ~S~ signal of the fifth embodiment;
Fi~. 58 is a diagran~ showing another assign~ent of signal points of the modified 4 ASK signal Gr the ~ifth embodiment;

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Figs. 59(a) And 59~b) are diagr~m~ showi~g asRignment of signal points of the ~odified 4 AS~C signal of the fifth embodiment;
Fig. 60 is a diagram showing another assign~ert of 5 9ignal point~ of the medified 4 AS~ signal of the fifth embodiment when the C/N rate i6 low;
Fig. 61 is a bloc~ diagram of a ~ransmitter of the fifth e~nbod imerlt;
~ Figs. fi2(a) and 62~,b) are diagr~ms showing frequeIlcY
distribution proflles of an ASK modulated sig~al of the fifth embodiment;
Fig. 63 iB a bloo~ diagra~ of a roceiver of the fifth e~bodlment;
Fig. 64 is a block diagram of a video signal trans~ltter 15 of the f ifth embodi~ent;
Fig. ô5 i~ a block diagram of a TV receiver of ~he -fifth embodiment;
Fig. ~6 is a block diagram of another '~V receiver of the fi$tb embodiment;
Fig. 67 is a bloc~ diagra~l of a satellit~ to-~ro~nd TV
recffiver of the fifth embodlment;
Fig. 68 is a diagram showirlg an assignmellt of signal points of an 6 ASK sign~l of the fifth emhodlment;
Fig. 69 is a block diagram of a ~-ideo encoder o~ ~he fifth e~bodiment;
Fig. 70 is a block diagr~m of a vid~o encoder of the fifth e~bodiment conLaini~g one divider circuit;

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Fig. 71 is a block diagram of a video decoder of the fifth embodiment;
Fig. 72 is a block diagram of a video decoder OT the fifth embodiment containing on~ mixcr circuit.;
Fig. 73 is a diagra~ showing Q time assignment of data components of ~ transmission signal according to the fifth embodiment;
Fig. 74(a) is a block diagram of a video decoder of the f i fth em~odiment;
Fig. 74~b~ is a dlagram ~howing anothor time a6signment of data components of the transmlssion ~lgnal accordin~ to the fifth embodiment;
Fig. 75 is a diagr~m showing a time assignment of d&ta components of a transmisslon signal according to the fifth.
embodiment;
Fig. 76 is a diagram showing a time assignment of data components of a transmis~ion signal accordi~g to the f ifth embodiment;
Fig. 77 is a diagram showing a time as~ignment of dat~
components of ~ transmission si~nal accDrding to the fifth embodim~nt;
~ i~. 78 i~ a block dl~gram of a video decoder uf the fifth embndiment;
Fig. 79 is a diagram showing a time ~ssigDmert of dat~
2~ components of a three-level tr~nsmission signal ~ccording to the fif~h embodiment;
Fig. B0 is a bloch dia~raLI of another ~-ideo decoder of .9',~ E . ~2~ t~ 3 ', ~ h ,. .
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the fif th embodiment;
Fig. 8~ i6 B diagra~ showing a time asslgnment uf da',a components Df B transmission signal aceording to the fifth embod,iment;
Fig. 82 i~ a block diagram of a video decoder for D~
,. sign~1 of the ~ifth embodiment;
Fig. 83 is ~ ~raphic dlsgram showing the relat,ion between frequency and time of a frequency ~odulated sigrlal according to the flfth e~bodi~ent;
Fig. a4 iB Q block diagr~m of a magnetic record/pl~ybsCk apparatus of the fifth embodiment;
Plg. 85 is a ~raphic diagram showing the relation between C/N and le~el according to ~he secoud embodiment;
Fig. B6 is a graphlc diagram ~howi~g the rel&tion between C/N ~nd transmission distance according to the second cmbodiment;
Pig. 87 i9 ~ block diagram of ~ trans~ission of the 6 econd embodiment;
Flg. 8~ :lc ~ block diagram of a receiver of the oecond embodiment;
Fig. ~9 is a graphic diagram shDwing the relation between C~N and erro~ rate accordlng to the second embodiment;
Fig. 90 is ~ diagram showing cignal atte~uating regions in the thre~-level tra~sml~sion of the iifth e~bodiment;
Fig. 91 i6 a diagraD showirlg signal attenuatir~g region~
in the ~our-level transmission of a sixth embodiment;

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Fig. 92 is a diagram ~h~wing the four-level transmissivn o~ the aixth embodiment;
Fig. 93 i~ a bloc:k diagram of a divider o~ the sixth er~bod iment;
Fig. ~4 is a block diagram oE a mixer of the si~th embodiment;
Fig. 95 is a diagram ~llOWiDg another four~ vel transmi~ion oE the siYth e~bodiment;
Fig. 96 is a view of signal propagation of ~ ~nown di~it~1 TV bro~dcsst cy6tem;
Fig. 97 is a view of signal propagation of a digit~l TV
broadcast system according to the sixth embodimellt;
Fig. 98 ls a diagram showing a four-level transmission of the sixth embo~iment;
lS Fig. 9~ is a vector diagram of a 16 SRQAM signal of the third embodiment;
Fig. 100 i~ ~ vector diagram of a 32 SRQAM signal of ~he third e~bodiment;
Fig. 101 is a Rraphi~ diagrarl showing the relation between C/N ~nd error rate ac~ording to the third embodiment;
Fig. 102 is a graphic diag~a~ showin~ the relation between C/~ and error rate according to the third e~bodiment;
Fig. }03 is a ~raphic diagram showin~ the relation bet~een shi~t distance n ~nd C/N i~eeded for tr~ns~is~ion : 25 according to the third embcdi~erlt;
Fi~. 104 is a graphir diagram showi~g the relation bet~een shift distanoe n and C~N needed for transmisslon 1~

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according to the ~hird embudiment;
Fig. 105 is a graphic diagram .show-ng the relation between 8ignal level and distanc~ fro~ a trans~itter antenna in terrestrial brnadcast service aceording to the third embodi~ent;
Fig. 106 is a di~gram ~howing a service area of the 32 SRQAM signnl of th~ tbird embodi~enti Fig. ~07 is a diagr~m showing a ~erv~.ce ar~a of the 32 SRaAM sigIIal of the third ~mbodiment;
Fig. 108 i~ a diagram showing a frequency distribution profile of a TV signal of the thlrd embcdime~t;
Fig. lO9 is a di~gram showing a time ~ssignment of the TV sign~l of the third Qmbodi~ent;
Fig. llO is a diagram showing a yrinciple of C-CDM of the third embodiment;
Fig. 111 is a view showing ~n aisi~nment of codes according to the th_rd embodiment;
Fig. 112 i8 a ~-iew showing an usMig~nent of an e~tended 3~ QAM accvrding to th~ third embodiment;
Fig. 1;3 i~ 8 view chowin~ a frequency assig~nent nf a modulatiorl ~ignal according to the fif-th embodiment;
Fig. 114 is a block diagra~ showing a magnetic recordlng/piayback apparatus according to the ~ifth embodiment;
Fig. 115 is ~ ~lock diagra~ showiflg a trans~ittcrJreceiver oi a portable telepho~e according to the eighth e~bodiment;

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Fig. 116 is a block dia8ra~ showing ba~e stations ~ccording to the eig~th embodiment;
FLg. 117 is a view ill~strating communication capacities and traffic di~tributio~ u:E a conv~ntional system;
Fig. lla is a view illu6tratin~ ~om~unication capacities and traffic distribution according to the ~igh~h embodimentj Fig. ll9(a) ~s a dia~ram sho~-ing a time slot a6~ignment of a conventional syste~;
Fi~ (b~ is a diagram showing a time slot assignment according to the ~ighth embodiment;
Fig. 120~a) is a diagram showing a time slot assignment of a convention~l TDMA system;
Flg. 120(b) is a dia~ram ~howing a time 610t assignment according to a TD~A ~ystem of the eighth embodimsnt;
Fig. 121 is a block diagr~m showing a o~e-level tranomitter/rQc~iver according to the eighth embo~iment;
Fig. 122 is a block diagram s~owlng a two-level transmitter/receiver according to the ~ighth embodiment;
Fig. 123 i8 a block diagram sho~ing an OFDM type transmitter~receiver according to the ninth embodiment;
- Fig. 124 is a vie~ illustr~ting a principle of the OFDM
system according to the ninth embodiment;
- Fig. 125(a) i~ a view showiIIg a frequency as~ignment of a modulation signal of a conventional system;
Fis. 125(b) is a view showing a frequencY assi~nment of a modulati~n signal according to the ninth embodimeut;
Fig. 126(a) is a view showin~ a frequency assignmerlt oi q ~-' J ~ J q 2l3 ~ to~

20924~5 a tran~mis~ion signal of the ninth embodi~ent;
Fig. 126(b) is a view showing a frequency assignment of Q receivi~ signal accordin~ to the ninth embodiment;
Fig. 127 is a block diagra~ showing a - 5 trans~itter/recsi.~er according to the nlnth ombodiment;
Fig. 128 is a block diagram showing a Trellis sncoder according to the fifth. embodime~t;
~ ig. 129 is a view showln~ a time assignment of effective symbol periods and guard interval~ acoording to the ninth embodi~ent;
Fig. 130 is a graphic di~gram shuwi~g a relation between C/N rate ~nd error rate according to the ~inth e~bodiment;
Fig. 131 is a bloc~ dia~r~m showing a magnetic rscording~playbAck apparatus ac~ording to the ~ifth 1~ embodiment;
FiB. 132 iB a view showin~ ~ recordin~ ~rmat of track on the magnetic tape and a tra~elling of ~ he~d;
Fi~. 133 is a block diagrarl ~howing a transmitter/receiver according to the third 0mbodiment;
Fig. 134 is a diagram ~howi~g a frequency asRignment of a conventional ~roadca~ting;
~ig. 135 i6 a dia~ra~ showin~ ~ relation b~tween service area and picture quality in a three-level si~nAl tr~llsmission 6ystem according to the third embodiment;
Fig. 136 is a diagram showi~g a ~requency assignment in case the multi-level signal transmission 6ysterl according to the third e~bodime~t i9 combined with an FDM;

i3G3~ ,J~ '?3~ N~ U ~ rJJ

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Fi~ 137 is a block dlagram ~howing a trans~itter/receiver according to the thir~ embodi~ent, in which Trellis encoding is adopted; and Fi~ 138 is a bloek diagram ~howing a 5 tr~nsmitter/receiver according to the ninth embodiment, in which a part of low frequency band si~nal i5 transmitted by OFDM.

DETAI~ED DE6CRIPTION OF TN~ PR~ K~ E~BODI~F~TS
10 E~o~ rlt One embodiment o~ the present invelltion will be described referrlng to the relevant drawings Fig. 1 shows the entire arran~em~nt of a 6ignal transmission system according to the present invention. A
tr&nsmitter 1 com~rises an inp~t unit 2, a divider circuLt 3, modulator 4, and a transmitter unit S. I~ action, each lnput ~ultiple~ signal is divided by the divider circuit 3 iDto three groups, a first dsta stream Dl, a second data stre~ D2, a third data stream D3, which are then modulated Z0 by the ~odulator 4 beFore Srans~itted from the transmitter unit S. The modulated sigral is sent up from an antennal 6 through an uplink 7 to a satellite lO where it, iS intercepted by an uplink antenn~ 11 and amplified by a transponder 12 before transmitted ~rom a downlink antenna 13 towards the grouI~d The transmission sign~l is then sent down throu~h three dow~links ~1, 32 and 41 to a first 23, a secorld 33, ard a I~C3~ 3,q25~ . 34Q ~. 22'~0~
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third re_eiv~r 4~ respectively. II1 the Eirst receiv~r 23, th~
signal intere~pted by an a~teDna 22 is fed through an input unit ~ to a demodulator 25 where its first data strea~ only ls demod~lated, while the second and third data streama sre not reeovered, b~fore transmitted further from an output unit 26.
Si~ilarly, the ~eeond re~eiver 33 allow8 the firY~ and second data streams of the sign~l intercepted ~y an antenna 32 arl~ fed f~om an i~put unit 34 to b~ d~odulat~d by a demodulator 35 and then, su~ed by a su~er 37 tn a sl~gle data strea~ which îs then transmitted further fro~ an output unit ~.
The thlrd receiver 43 allows all the ~irst, secorld~ and third data ~treams of the si~nal intercepted ~y an anter~a 42 : 15 and fed from an input unit 44 to be demodulsted by a demodulator 45 and then, summed by a summer 47 to a si~gle d~ta stre~m whlch is then tra~s~itted further f.rom an output ur,i~ 46.
As understood, the three dis~rete receivers 23, 33, and 43 have their respective de~odul~tor6 of di~fere~t characteristics such that their outputs demodulated from the s~me frequency bar,d ~ignal of the tr~n6mitter 1 ContQin data of different ~izes. More particul~rly, three different but rompa~ible d~ta can simultaneously be carried on ~ ~iven frequPncy band signal to their respective receiver~. For ex~pls, ~aeh of three, exi~tir.g NTSC, HDTV, and super HDTV, digital Si~ll&ls i9 divided into a low, a high, a~d a ~uper 3f~- q?~5 ~ ? ~
' 2~92~95 .
high frequency band co~ponent8 which repre~ent the first, the second, and the third data strea~ respecti~ely. Accordingly, the three different TV signals can be transmitted on a one-channel frequency band carrier for simultaneous reproduction of a mediu~, a high, and a super high resolution TV imdge r~speeti~ely.
ln service, the N~6C TV s~gnal is intereepted by a recei~er acco~panied with ~ small antens-a for demodulation of a small sized data, the HDT~ signal is intercepted by a receiver ac~ompanied with a medium antenna for demodulation of ~edium-sized data, and the super ~Drr~ si~nal i8 int~rcepted by a receiv~r acco~panied with a l~rge antenna for ~emod~lation of large-sized data. Also, as illustrated in Fig. 1, a digital NTSC TV signal containin~ only the firfit data stresm for digital NTSC TV broaacasting service is fed to a digital transmitter 51 whers it is received by an input ~ni~ S2 and mod~lated by ~ demodulator 54 be~ore tr~nsmitted further ~rom a tr~smitter urit 55. The de~odulated signal i9 then sent up ~rom an antennal 56 through an uplink ~7 to the 2~ satellite 10 which in turn transmit~ the sa~e through a downlink 58 to the firs~ receiver 2~ on the grou~d.
The first receiver 23 demodulates with its demodula~or 25 the modulated digital 6ignal supplied from the digital trans~itter 51 to the original first data str~am signal.
2~ Si~ilarly, the same modulated di~it~l signal can be intercepte.d and de~odul~ted by the second 33 or third receiver 42 to the first data stream or N'rSC TV sign~ n I ~ r~ 7~L i~ r~ ? ' . ' O ~
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summary, the three discrete receivers 23, 33, and 43 al.l c~n intercept and process a digital ~ignal of the e~isting TV
syste~ for reproduction.
The arran~ement of the 9ignal tran6~ission ~y~tem will be described irl ~ore ~etail.
Fig. 2 is a block diagram of the transmitter 1, in which an i~put signal i.s fed Acro~s the input unit 2 and di~ided by the divider circuit 3 into thre~ di~ital sign~ls cont~inin~
a first, a s~cond, &nd a third data stream respectively.
Assuming thQt the input signal i5 a video si~nal, its low frequency band compo~ent is assigned to the first data stre~m, its high frequency bar.d component to the second data stream, its super-high ~requency band component to the third data stream. The three diffsrent freque~cy band ~i~nals ~re 1~ fed to a modu].ator inpu.t 61 o~ the modulator ~ re, a signal point modulating/changing circuit 67 modulates or changes the positions o~ t.he signal points accordi~g to an e~ernally given signal. The modulator 4 is arranged for a~plitude ~odulstion on two ~OD-out-of-phase carriers respectively which are then s7l~mRd to A multiple QAM signal.
More sperifically, the signal from the modul~tor input 61 is fed So both a first 62 and a s~co~d AM mo~ulator 63. Also, a carrier wave of cos~2~f~t) produ~ed by A carrier generator 64 is directly fed to the first ~M modulator 62 and alsn, to a ~/2 phase shi~ter 86 where it is 50~ sl~ifted in phase to a sin~2~fct) form prior to tran~mit~ed to the se~ond ~I
modulator 63. The two amplitude modulated si~nals from the 2~

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first and second A~S modula~ors 62, 63 are summed by a su~er 65 to a transmission signal which is then transferrsd to the t.ra~s~itter ~~nit 5 for output. The procedure is well known and will no ~urther be e~plained.
The ~ signal will now be describ~d in a commoII 8x8 or 16 state constellation re~errin~ ~o th~ first q~adrant oE a sp~ce diagra~ in Fig. 3. The output 6ignal of the ~odulhtor 4 is expressed by ~ sum vector of two, Acos~ct und Bcos21~fct, vectors B1, 82 ~hich represent the two 90~-out-o~-phase carriers respectively. When the dist~l poi~t of a sum vector ~rom the ~ero point represent.s a signal point, the 16 QAM signal has 16 signal points determined by a combination o~ four hori~ont~l amplitude values a1, a2, a3, a4 and four vertical ~mplitude values b1, b2, b3, b4. The ~i~st quadrant ~5 i~ ~ig. 3 contain6 four signal points 83 at Cll, 84 at Cl2, 85 at C22, and 86 at C21-Cll is 8 SU~ vector of a v~tor 0-al and a vector 0-b and thus, e~prc6sed B8 C11 = a1cos2~frt-blsin2~fct Acos~2~fct+d~/2).
It is now assumes that the distance betweer~ 0 ~nd a1 in the ortho~onal cu~rdinates of Fi~. 3 iB A1, be~ween al and az is A2, between 0 and bl is B1, and bet~-een bl and b2 is Bz.
~s shown in Fig. 4, the 16 6ignal points are allocated in a vector coordinate, 1I1 which each point represerrt6 a four-bit patter~l thus to allow tne traDsmis6ion of rour bit data per perlod or ti~o alot.
Fi~. ~ illustrates a com~on assign~en.t of t~o-~it '~ ~ S 3 ~r 3 ~ ~3~ J ~ O ' 2092~

patternB tO the 16 signal point~.
When the distanre betw~en two adjacent si~nal points is great, it will be identified by the receiver with ~ueh ease~
Henoe, lt is de~ired to ~pace t~e sigD~l point~ at greater interv~l~. If two Darticular sig~al poihts ~re allocat~d near to each other, -the~ are r~rel-~ distin~uished and error rate will be i~creased. Therefore, it i~ most preferred to have the si~nal poin~s spaced at e~al inter-vals a6 shown in Pig.

5, in which the 16 ~ signal i6 defined by Al-A2/2.
~h~ trans~itter l of the embodiment is arranged to divide an input digital 6ignal into a fir~t, a second~ ~nd a Shir~ data or bit stream. The 16 signal points or ~roups of signal points are di~ided into ~our groups. Then, 4 two-bit pattorns o~ the first data stream are assigned to the four slgnal point groups respectively, as shown in Fig. 6. More particularly, wh~n the two-bit p&ttern of the first data stream is ll, one of four signal points of the first signal point grcup ~l in the first quadrant is selected dependi~g on the content of ~he sec~nd dat~ stream for tr~nsmissicn.
Similarly, ~hen Ol, one signsl point of the second signal point ~ro1~p 92 in the second qu~dra~t iB selected and transmitted. W~en 00, one sign~l point of the third signa~
point group ~3 in the t~lrd quadr~nt is tr~nsmit~ed and wh~n lO, one signal point of the fourth signal point ~roup 94 in the fourth ~uad~ant is ~ransmitted. A}Y~, 4 two-bit patterns in the second daSa strea~ uf the l6 QAM Bignal, or e.~. 16 four-bit patterns in the second data stIeam of a 64-state QAM

! 9 S 3 ~ 2 7 '~ t~ ? ,r/3!J~
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sign~, are a~signed to four 6ignal points or ~b sig~al point ~roups o~ each of the four signal point groups 9l, 92, 93, ~4 respectively, aE shown i~ Fig. ~. It should be under~to~d that the assignment is sy~etrical between any two S quadrants. The assigr~nent of the sigr~al points to the four groups 91, 92, 93, ~4 iB determined by priority to the two-bit data o~ the fir~t data st~eam. As the result, two-bit data of the fir6t data strea~ and two-bit data of the second dat~ stream can be transmitted independently. A1~, ths first data strea~ will be demodulated with the use o~ a common 4 PSK receiver havir,g ~ ~iven antenna s~nsitivity. If the artenna sensitivity is higher, a modified type of the 16 4AM
receiver of the present invention will intercept ar~d demodulate both the first and second data stream with equal 15 Bucce8s~
Pig. 8 shows an e~ample of the assignment of ~he first ar,d ~econd d~ta streQms in two-~it patterns.
When the low freqllency band component of an HDTV video signal is a6signed to the first data stream and the high frequency componert to the second data stIeam, the 4 PSK
receiver ~an produce an NTSC-lcvel picture from the first data s~re~m and the 16- or 64-state QAM rereiver can produce an HDTY pi-~ture ~rom a ~ompo~ite reproduct~on ~ig~al of the first and secorld dat~ stream~.
~5 Since the signal poi~t~ are allocated at ~qual intervals, there is developed in the 4 PS~ receiver threshold distance betweell the coordinate axes and the snQded ~c~ q ~ ll.. ,4~ .... 0~
' 2092~95 . .
area o~ the ~irst quadrant, as shvw~ in Fi~. 3. If the threshald distance is ~ , a PSK sig~al havin~ an a~plitude o~ ~0 will ~ucce~fuily be intercepted. Howeve., the amplitud~ hds to be i~creased to a three times greater value 5 or 3 ~ for transmission of a 16 ~AM signal while the thre~hol~ distance A~ bein~ ~aintain2d. More particul~rly, the energy for transmi.tti~g tlle 16 QAM signdl i~ needed nine times 6reater than that for sending the 4 PS~ signal. Also, whe~ the 4 PSX signal is transmitted in a 16 QA~I ~ode, energy waste will be hi~h ~nd reproduction vf a ~arrier signal will be troublesome. Above all, the energy availabie for satell.ite tran6mltting is rot abundant but strietlY li~ited to mini~um use. Hence, no large-energy-consumirg 91gnal tr~mitting ~ystem will be put into ~r~ctice until more energy for aatelli~e transmission i~ available. It is e~pected that a ~reat number of the 4 PSK receivers are introduced into the ~arket as digit~l TV broadcasting is 600n in service. After introduction to the market, the 4 PSK receivers will hardly be shifted to higher sensitivity models because a fiignal ~0 ir~tercepting charaoteristic gap between the t~o, old and new, mod~ls i~ high. Therefore, the tra~smission of the 4 PS~
signal 5 must not be abandoned.
In this respect, a new system is despera~ly needed for trans~itting t~e 6ignal point data of A qua8i ~ PSK ~igna1 in the lB QAM mode with the use of less e~ergr. Otherwise, the limited energy at a satellite station will degrade the entire transmission syste~.

. .
209~495 The ~rese~t invention resi~es in Q ~iti~le signal levcl arrangement in which the four signal p~int groups 91, 9Z, 93 94 are ~llocated at a greater clistance fro~ each other, as shown in Fig. 10, f~r minimizin~ the energy consumption S required ~or 16 ~AM modulation af quasi 4 PSK sigrl~lfi.
F'or clenring Ihe relation between the signal recei~ing sensitivity and the tr~nsmitting energy, the arrangement o~
the di~itnl trans~itter 51 and the ~ir~ receiver 23 will be described in more detail referring to Fl~. 1.
Bot~ the digital transmitter 51 and the first receiver 23 are formed o~ known typss for ~ata transmission or video signal tra~s~ission e.g. in TV broadcasting servicc. As shown in Fig. 17~ ths digital tra~s~itter 51 is a 4 PS~ transmi~ter equivalent to the multiple-bit QAM transmitter 1, shown in Fig. 2, without AM modulation capablllty. I~ operation, nn input ~ignQl iB fed throug~. an in~ut unit 52 ~o a ~odulator 54 ~here it i9 diYided ~y a modulator input 121 to two components. The two components are then transferre~ to a ~i.rst two-phase modulator circui~ 122 for ph~se modulat.on of a ~ase carrier ~nd a second two-phuse modulAtor circuit 123 for phase modulation of a cnr~ier which is 9G~ out of phase with the base carrier respecti~ y. Two outputs of the firs~
and second two-phase modu1ator circuits 122, 123 are then summed by a su~er 65 to a c07~posite modulated signal which is further trans~Ditted fr~ a trnns7~littel unit 55.
'rhe resultallt modulated ~ignal ls shown ln the space diagram of Fig. 18.

I S '~ 3~ ~ ~ 5 ~ ; ~ 2 . 7~ . ~ 4 ? . . ~ ~ O

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. .
It is known that the four signal poi~,s are ~llocated ~t e~ual distances fur ~chievin~ optimum energy utilizatior~.
Fig. 18 illustrHtes nn example where the four signal pOiIlt6 125, 126, 127, 12,B represent 4 two-~it patterns, 11, O1, 00, ~ and lO respecti~ely. It is al~o desired ~or succefisful data - .~ transler from the digltal tran~mitter 51 to the fir6t recelver 23 than the 4 PS~ signal from the digit~l transmitter Sl hus an amplitude of not leos than A given level. More specificall~, whe~ the minimum ~mplitude of the 4 PSK signal needed for transmission from the digital trans~itter 51 to the fir~t receiver 23 of 4 PSK mode, or the distance. between 0 and al in Fig. 18 iB ~, the first re~eiver 23 e~cces~fully in~ercept any 4 PSK signsl having an amplitude of ~ore than ~ .
The first receiver 23 ie arranged to receive at its small-di~meter antenna 22 a desired or 4 PSK ~lgnal which is tr~ncmitted from ~he trsnsmitter 1 or digital traDsmitter 51 re~p~r.tively through the trallsponder 12 of the satellite lO
and de~odulate lt with the demodul~tor 24. In ~ore par~icular, the first receiver 23 is substantially ds6igned for interception of a digital T~ or data co~municstion~
signal of 4 PSK or 2 PSK mode.
Fi~. 19 is a block diagram of the fir~t receiY~r 23 in which an input signal received by ~he antenna 22 ~rom the satellLte l2 i9 fed through the input unit 24 to a carrier reproducirlg circuit 131 where a carrier waYe is demodulated and to a ~/2 phase shifter 132 ~here a 9O~ pha~c c~rri~r w~ve 1 9 L ~ 5~ P 3 ~'OJ
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iB demodulated. ~lso, two 90~-out-of-phase component~ of the input signal ~re ~etected by a first 133 and a s~cond phase detector circ~it 134 respectivel~ and tran6ferred t~ a first 136 and a ~er~ond discrimination~demodulation circuit 137 re~pectirely. ~wo demodulated components from their respective di6~rimination/demodulation circuits l36 and 137, which have separately been dis~rimirlated at unita of time slot by means of timing signals from a timing wave e~tracting circuit 135, are ~ed te a first data stre~m ~eprodueing unit 232 where they are summed to a ~irst data stream sign~l which Is then deliverad as an output ~rom the output unlt 26.
The inpuc ~i~nal to the first receiver 23 wi~l now be explained in more detail referring to the vector diagram of Fig. 20. The 4 PS~ signal received by the first receiver 23 from the digital transmitter 51 is expre6~ed in an ideal iorm without tran6mission distortio~ and noiee, usine four ~ignal poirts 151, 152, 1~9, 154 shown ln Fig. 20.
In practice, the real four signal points appear in particuL~r e.~t~nded areas about the ideal &ignal po~itions 2~ 151, 152, 153, 154 respeetively due to noise, amplitude dlstortion, and phase error developed during transmission. I~
one signal point is uniavorably displaced from it~ original position, it will hardly be distinguished from its neighbor signal point nnd the error rate will thus be increased. As the error rate increases to a ~ritical level, the reproduction of data beco~es less accurate. ~'or enabling the data reproduction at a ~axim~m accept~ble level of the error r ~ t ~ 2 ? ~ 30 2Q9249~3 rate, the distance between any two signal points ~bould be far e~ough to be distin8uished from ea~h other, If the di~tarlce is lA~, the signal point 15$ o~ ~ 4 PS~ ~ignal at clo6e to a critical error level has to stay in a rirst di~criminsting area 155 denoted by the hatching of Fig. 25 and determined by ¦O-a~¦~A~ and ¦O-b~¦~A~. This allow6 the sLgnal tran~mission syste~ to reproduce carrler waves and thus, de~odu1a-te a wante~ signal. When the ~ini~um radiue of the antenn~ 2~ ls set to rO, the transmisF:ion ~ignal of ~ore than a give~ level can be int.ercepted by any receivcr o~ the eystem. The amplit~de of ~ 4 PSX signal o~ the dlgltal transmitter ~1 shown in ~ig. 18 is mlni~um at ~ and thus, the minimum amplitude ~ of a 4 PSK signal to be received by the first receiver 23 i6 deter~ined equal to ~ . As the result, tne first rec~iver 23 can intercept and de~odulate the 4 PSK signsi from the digital tran6mittsr 51 at the ma~imum acceptable level oE the error rate when the radius of the Antenna 2Z is ~ore than rO. lf th~ trans~ission signal is of modified 16- or 64-state QAM mode, the first recciver 23 ~0 may find difficult ~o reproduce its carrier wave. For compensatioIl, thc sig~al points are irlcreased to ~ight which are ~llocated at angles o~ (~t4+n~2) as sllown in Fig. 25~a) and its carrier wave will be reproduced by a 16~
multiplication technique. Also, i~ t.he signal point6 are assigned tn 16 locations at angles o~ n-~8 aF~ shown in F'ig.
25(b), th~ carrier o~ a qua~i 4 PS~ mode 16 ~AM ~odulated signal can be reproduced with th~ carrier reproducin~ circuit ~ 3 ~ 5 ~ t ~ , 34~ [l~

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131 which is mo~i~ied for pe~forming 16~ ~requency multiplication. Al the time, the si~naL points in the transmitter I ~hould be arranged to sati~fy A~ Az)=~a~(~/8).
Here, ~ case ef rec~iving a QPS~ signal will be co~sidered. Similarly to the manner performed by the signal point modulati~g/changing circuit 67 in the transmitt~r shown i~ Flg. 2, it is also posaible to ~od~late the positions Or the sign~1 points of the QPS~ s~gnal showr, in Fig. 18 (amplitude-modulation, pulse-modulation, or the like). 1 this cQse, the signal point demodulating unit 138 ln the first receiver 23 demodulates the posi~io~ modulatQd or position changed signal. The dem~dulated signal is cutpatted together with the first data stream.
The 16 PS~ sig~al of the transmitter 1 will now ~e explained referring to the vector di~gram of Fig. ~. Wh0r.
the horizontal vector distance A1 of the signal point 83 is greater than ~ of the mi~imum ~mplitude of the 4 PSK ~lgnal of the digital transmitter 51, the four signal points B3, 84, 85, 86 in tbe first quadrant of ~i~. 9 stay in the shaded or fir~t 4 PS~ ~ignal receivable are~ 87. When received by the first rec~ er 23, the four points of the signal ~ppear in the first disori~in~ting area of the vcotor field shown in Flg. 20. Hence, a~Y of the ~ignal points 83, 8~, 8~, a6 of Fi~. 9 Can b~ translated into the sign~l level .I.51 ol Fig. 20 by the ~irst receiver 23 so that the two-bit pattern of 11 is a~sigDed to a correspunding time slot. The two-bit pattern ~2 I9~ '5~ .7~ 0~ .......................................... 3~ J

2092~95 v of 11 is identical to 11 of the fir~t signQ1 point group ~1 or first data stre~ of a signal from the tr~nsmitter 1.
Equally, the ~irst data 6tream will be reproduced at the second, third, or fourth quadrant. As the result, the $irst receiver 23 reproduces two-bit data o~ the first data stream out of the plurality of data streams in a 16--, 32-, or 64-state Q~M sign~l transmitted fro~ t~e trQnsmittsr 1. The second and third data ~tream6 ~re containod in four ~eg~ent6 of the signal point group 91 and thus, will not affuct on the demod~lation of the fir~t data 6tream. They may however affect the reprodu~tion oî a carrier wave arld an adjuotme~t, described l~ter, wi].1 be needed.
If the transponder of a satellite supplies an sbundance of energy, the forgoing techni~ue of 16 to 64-state QAM mode transmission will be feasible. Howeverl the tran6ponder of the ~at~llite in any existing satellite transmis~ion system i8 strictly limited in the power supply due to its compact size and the capability of solar batteries. If the transponder or satellite is ncrea6ed in 6ize thus weight, its launching cost ~-ill soar. This disadvantage will rarely be eliminated by traditional techniques ~nless the COfit cf launching a satellite r~cket i5 raduced to a considerable level. In the existlng Cystem~ a co~mon co~munications satellite pro~ides a5 low as 20 W of power supply and a comm~n ~r~adcast satellite offers 100 W to 200 W at ~est. For tran6~i6sior~ of such a 4 PSK sig~al in the symmetrical 16-state QAM mode as shown i~ ~ig. 9, the minimum signal pcint distance i8 neede~ 3 ~ as the 16 ~ amplitude is e~pres6ed by 2.Al-A2 . Thus, the energy needed fGr the purpose is nirle times greater than that for transmission of a CO~ilnOII 4 PSK
sig~al, in order to maintain compatibi1ity~ Also, ary conventio~al satellite transponder can h~rdly pro-~ide a power for enabling such H B~ll antenna Df the 4 PSK first receiver to intercept a traIl~mit;ted signal therefrom. F'or e~ample, in the e~isting 40W Bystem~ 360-hl i8 needed for ~ppropriate signal transmission and will be unre~listic in the respe~t of c06t.
It would be -~nder stood that the s~metrical signal state QA~ technique is most effecti~e when the receiverY
equipped with the 6ame sized antennas ~re empl~yed corresponding to a given trans~itting power. Another novel technique will however be preferred ~or use with the receivers equipped with different sized ante~rlas.
In more detail, while the 4 PS~ sisnal can be intercepted by a common low cost roceiver sYgtem having smsll antenna, the 16 Q~M signal i~ intended to be received by a high cost, hi~h ~u~lity, ~ultiple-bit modulating receiver s~stem with a medium or l~rge sized anter~ whi~h is desig~ed for pro~iding hi~hly valu~ble services, e.g. HDTV
entertaiI~nt6, to a p~rticular person who invests more money. This allD~s both 4 PSK and 16 QAM signals, if desired, ~5 with a 64 DMA, to be transmitted siml~ltaneously with the help of a s~al1 irlerea~e in th~ transmitiing power.
For example, the trans~litting power can be maintained !CS~ 3,q2,"h 73~ r~ h~ d '' r/~0 ' 2092d~9~j low when the signa~ points are alloca~ed at Al- A2 as shown in Fig. 10. The amplitude A~4) for tran6mi~sien of 4 PS~ dats iB e~pressed by a vector ~6 equivalent to a squ~re root of ( Al+A2 ) 2+ ( Bl t B2) 2 . Then, ~ A ( 4 ); ~A1 +B1 ~ 2A~O
¦A(16) ~(A1+A2)2~(BI~B2)~4A~O2+4A~8n1Z
¦ A~ A(4 ) ¦ =2 A~cordingly, the 1~ QAN ~ignal can be tran~itted at a t~o time~ greater amplitude and a four times ~reater tran~mitting energy than those needed for the 4 P9K sig~al.
A ~odified 16 QAM ~ignal according to the pre~ent invention will not be demodulated by a com~on receiver deeigned $or symmetrical, equally dista~ced si~nal point ~AM. However, it can be de~od~lated with the second receiver 33 when e~o threshold A1 and A2 ~re predetermined to appropriate valtles, ~t Fig. 10~ the minimum distance betweel~ two 8ignal pOiIltC }n the first segment of the signal point group gl is Al and A2~2A1 i9 e~tabli~hed as compared with t.he di8tance 2Al of 4 PSK~ Then, as A1=A~, the distance becomes 1~2. Thi~ sxplair,.s that the ~ignal receiviIIg sensitivity h~6 to be two ti~es greater Eor the same error r~te and four times ~reater for the aame si~nal level. For havlng a fo~r times ~reater value of sensitivity, the r~dius r2 ~~ the ante~a 32 of the s2cond receiver'33 has to be two timeR grea~er than the radi~s r1 of the antenna 22 of the first receiver 23 thus satisfying r2-2rl. ~or exa~ple, the antenna 32 of the second receiver 33 is 60 cm dia~eter when the antenna 22 if the first receiver ~5 ~U~ 5E ~ t~ 3~ ? ~r G~
~092~9~

23 i~ 30 c~. In this manr~ex, the seco-nd ~ta stream representing the high fr~quency com~onent o~ an HDTV will be carried on a signal chanrAel and demodulate~ successfully. A6 the second recei~er 33 intercepts the second data stream or a higher data si~nal, its owner can e~joy a return of high inve6tme~t. Hence, the se~ond recEiver 33 of a high prtce ~y . .
be ucceptad. As the minimum energy for tr&n~mission of 4 PSK
data i9 predeter~ined, the ratl~ nl6 of modified 16 AP~K
transmitting energy t~ 4 PSX transm~tting energy will be calculated to the antenna radius r2 of the second receiver 33 u~ing a ratio between Al and A2 ~hown in l-~ig. 10.
~ n particular, rl6 is expre~6ed by ~(Al+A2~/A1)2 which i~
the minimum energy for tran6missior, of 4 PS~ d~ta. As the signal point dlstance suited for m~diiisd 16 Q~M inter~option is Az, the cignal point distance for 4 PS~ lnterception i8 2Al, arld the signal point distance ratio i_ Az/2Al, the antenna radius r2 i_ determined as shown in Fig. ll, in which the curve lOl represents the relation between the tr~r.6mittin~ ener~y ratio nl6 and the rsdi~s ~2 of the ~ntenn~
Z2 of the ~econd receiver 23.
Also, the poir,t 102 irdicates transmi6~ion of co~mon 1~
~M at the equ~l diatan~e 6ig~al 6tate mode where the transmitting erergy is nine times greater and thuq will no more be practical. As apparent from the graph of Fig. 11, the antenna radiu~ r2 of the seco~d receiver 23 cannot be reduced further even if nl6 is i~crea6ed more than 5 times.
The transmitting energy dt the satellite i~ li~ited to ~6 ~ I- C ~ r u ~ Q ~ , / 7 0 ~
- 2 0 9 2 4 9 ~

a small value ~nd thus, nl6 preferably stays uot more tha~ 5 times the value, as denoted by the hatching of Fig. 11. The point 104 within the hat~hin~ area 103 indi~ates, for example, that the antenn~ radius r2 of a two ti~es greater value is matched with a 4~ value of the transmittin~ energy.
Also, the point 105 represents that the transmis~ion energy sho~ld be doubled when rz is about 5~ greater. Those values nre all within a fe~sible ran~e.
The v~lue of nl6 not 8re~ter than 5x value i~ expressed using A1 and A2 as:
nl~ = ( (Al+A2) Hence, A251.23Al.
If the distance between any two ~ign~l point group segments shown in ~ig. lD ls 2A(4) and the maxi~um a~plitude 15is 2A(16), A~4) and A(1~)-A(4) ~re propurtional to A1 and A2 respectively. Hence, (A(l6))2cs(A(l4))2 is established.
The sction of a modified 64 ASPK transmission will be described as the third receiver 43 can perform 64-state QAM
demodulation.
20Fi~. 12 is a vector dia~ram in which each ~ignal point group ~egment contains 16 signal points as compared with 4 sign~. points of Fig. 10. The first signal point group ~egme~t 91 in Fig~ 12 has A 4x4 matrix o~ 16 signal points allocated at equal interval~ c;udi~g the point 170. Fer providing compatibili.ty with ~l PSK, Al> ~ has to be satisfied. If the radius of the ante~a 42 of t~e third receiver 43 is r3 and the transmit~i~g e~er~y i~ n~, the y5,~ 9 ~ 3~ 3~ i3~1~
' 209249~

equation is e~pressed afi:
r32 = ~62/(n~l)~rl2 Thi6 relation hetweer. r3 a~d n of ~ 64 Q~M ~igr.al is al60 shown i~ the grHphic repres~ntation of Fig. 13.
It is undar stood th~t the sign~l point assign~ent shown in Fig. 12 allows the 6eco~d receiver 33 to demodul~te only two-bit patterns of 4 PSK da~a. Henc~! it i~ de6ired for having compatibility between the fir~t. secQna, and third receivers that the seco~d receiv~r 33 i9 arrarlged capable of demodulating a modified 16 ~M form from the 64 QAM modulated signal.
The comp~tibility between the thr~e dis~rete receivers can be implemented by three-level grouping o~ signal points, as illu6trated in Fig. 14. The description will ~e made referrir,g to the first quadrant ln which the first sigr~al point groùp segment ~ represents the two-bit pattern 11 of the ~irst data stream.
In particular, a first sub seg~ent 181 in the ~ir~t signal point ~roup segment 91 is assigned the two-bit pattern 20 11 of the second data stream. Equally, a second 182, a third 183, and a fourth sub segment 184 are assigned 01, 00, and 10 of the same respectively~ This assig~ment is identicnl to that shown in Fig. ~.
The si~nal point allocation of the third data stream Z5 will now be e~plained referring to the vector diagram of Fig.
15 which ~hows the firsL quadrant. As shown, the f~ur signal pOilltS 201, 205, 209, 213 represe~lt th~ two-bit pattern of 3E~

I 9 ~ 3 . '.' ,~ L 5 ~ . ?~ LT~

2~9~49~
"

11, the ~ign~l points 202, 206, 210, Z14 represent ~1, the ~i~nal poi~ts 203, 207. 211, 215 represent 00, and s gnal point~ 2041 20~, 232, 216 represent l~. Accordingly, the two-bit patterns of the third data strca~l can be trans~itted Eeparately of t~e ~irst and second data streams. In other words, two-bit data Gf the t.hreu diffPrent sign~l levels can be tr~rlsmitte~ respectivel~.
As understo~d, the present invention pe~mits not only trans~is6ion of si~-bit data but also interception of -three, two-bit, four-bit, ~rd ~i~-bit, different bit length data with their respective recei~ers ~hile the signal co~patibility remains between three ievel5.
The signal point allocation for providing compatibility bet~een the three levelQ wi~l be de~cribed.
As shown in Fig. 15, Al2 ~ is es~ential for allowin~ the fir6t receiver 23 to receiva the first d~ta stream~
It iB needed to space any two sigual point~ from each ~ther by ~uch ~ di~tance that the sub segment signal points, e.g. lB2, 183, 184, of the second data stream shown in Fi~.
15 can be distiDgui~he~ from the signal point 91 ~hown in Fi~. 10.
~ ig. 15 shows that they are spaced by 2~3A2. ln this case, the distance be~ween the two signal points 201 and 202 in the ~lrst sub segment 181 i9 A2/6. The tra~6~ittin~ energy needed for signal interception with ~he third receiver 43 is no~T c~lculated. If the r~dius of the antenn~ ~2 is r3 and ths needed t~arlsmitting erlergy is n~ ti~e~ the 4 PS~ transmitting ~9 l3~3~ 3,~ v. 3l~ ?

energy, the ~quation is expressed as;
r3~=(12rl)2~
This reLation is also denoted by the curve 211 in ~ig. 16.
For e~a~ple, if the transmitting energy is 6 or 9 tlmes greater than that for 4 PSK tr~smission at the point 223 or ~22, the antenna 3~ having a radius of 8x or 6x value respectively can intercept the fir~t, second, and third d~ta strea~u for demodulation. As the signal poi~t distunce of the second data stream is close ~o Z/3A2, the relstlon bctween rl and r2 is e~preo~ed by:
r22=(3r1~2~(n-1) Therefore, the antenn~ 3~ of the second receiver 33 has to be a little bit increased in radiui as denoted by the curve Z23.
As under6to~d, w~lle the first and second d~t~ streams ~re transmitted trough a traditioral satellite which provides a small si~Dal trans~itting energy, the third data stream can also be trans~it.ted through a future satellite which provides a greater ~ign~l transmitting energy without interrupting the action of the first and second r~ceivers 23, 33 or with no need of modification of the same and thus, bDth the comp~tibi;ity ~nd the advancement ~i.ll highly bP ensured.
The signal receiving action of the seco~d receiver 33 will first be described. As compared with the fi~st receiver 23 arranged for int~rception with a small radius r1 antenna ~lld demodulatior. of the 4 PSK modulated sign~l cf the digital trans~itter 51 or the ~ir~t data ~tream of the ~ignal of the transmitter 1, ~he seco~ld recci~er 33 is adopted for '~53 3,~ 1$ ~;t 2~92~9~

perfectly de~o~ulating the lff signal state tw~-bit data, ~hown in Fig. 10, or seeo~d data stream of the 16 QhM signal from the trans~it~er 1. In to~al, four-bit data i.ncluding also the first dat~ stream cAn be demodulated. The ratio betwe~n ~l a~d A2 i8 however dif4erent in the two trans~ittPrs. The two different dat~ are loaded to Q
demodulation c.n~troller 231 of the second recei~er 33, shown 1~ Fig. 21, which in turn ~uppli~s their respectiv~ threshold values to the demodulating circuit for AM demodulation.
The bloc~ diagram of the second receiver 33 in F'ig. 21 is similar in b~sic construction to that vf the first receiver 23 9hOWn in Fig. 19. The dlf~erence is that tha radius r2 of the antenna 32 i6 greater than rl of the antenna 22. This allows the second receiver 33 to identify a sl~nal co~ponent involvin~ a smaller fiignal point distanc~. The demodulator 35 of the second reeeiver 3~ also cont~ins a first 232 and a second data Str~Bm reprodncing unit 233 in addition to the demod~lation controller 231. There i9 provided a fir6t discri~ination/reproduction circuit 1~6 for AM demodulation of modlfied 16 QAM signals. Ag understood, each carrier is a four-bit signal havi~g two, positive and neg~tive, threshold values about the zero level. ~s apparent from the vector diagram, of Fig. 22, th~ threqho1d values are varied depending on the transmitting energy of a transmitter ~5 since the ~ransmitting signal of the embodiment i~ a modified 16 QAM signal. When the reference thr~shold is THl~, it is determined by, as shown in Fi~. 2~:

c, 3~ 3 6 ~ /, r~ 3 2092,49S

'rH~ Al~A2/ 2 ) / ( A1+A2 ) 'rhe variou~ data for demodulation including Al and A2 or 1~5, and the value m for ~ultiple-bit modulation are al90 transmitted from the transmittcr 1 us c~rried in the fir6t S daLa stream. The ~l~modula~ion control ler 231 may be ~rr~n~ed for r~-overing ~uch de~odulation dat~ through statistic prvcess of -the received signal.
A way o~ determi~ing the shift factor Al/A2 will described with reference to Fig 26. ,~ change of the ~hi~t factor Al/A2 causefi a change of ~he threshold ~alue. Increaee of a difference of a value of A1jA2 set at the rec~iver side from a value of Al/Az set at the tr~ns~itter side will incre~se the error rate. Referrin8 to Fig. 26, the demodulated oignsl from the second data stream reproducing 1~ unit ~33 ~ay be fed back to the demodulation controller 231 to change t.he shift factor Al/A2 in a direction to increase the error rate. By thi 9 arrangement, the third receiver 43 may not demodulat~ the ~hift factor Al/A2, so that tho circ~it constr~ction can be s1mplified. F~rther, the transmitter ~ay not trans~it the shift factor Al/A2, 60 that the transmission capacity car, be increased. This tec~nique can be applied also to the second receiv~r 33.
Th~ d~modul~tion controlle r 2 31 has a memory 23la for storirg therein different threshold value~ (i.e., the shift f~otors, the number of signal point~, the synchrorizatio rules, etc.) which corre~pond to different channels of TV
breadcaQt. When receiving one of the rhannel~ again, the ~2 ~ 3 q ' ~1 E . ~ F,~ 4'~ . ~- 30v~
2~2~9~

valuec crirresponding to the recei~ing cha~el wili be read out of the ~e~or~ to there~ stabili~e the reCepLion quickly .
If ~he demodul~t~on data is lost, the demodulatLon Of the ~econl d~ta st~ea~ will hardly b~ e~ecuted. ~his will be e~plained referring to a flow chart ~ho~n in Fig. 24.
Eveli if the demu~llatio~ d~ta ;8 not available, demodul~tlon nf the 4 PSE at Step 313 and of the first data ~tream a-~ Step 301 can be implemented. At Step 302, the demodulation data retr.ieved by the first da~a stream reproducir!~ unit 232 is trancferre~ to the de~od~lation controller ~1. If m is 4 01- 2 at Step 303, the de~odulation contr~ller 231 trlggers demodulation of 4 PS~ or 2 PSK at Step 31~. If ~ot, the proced-ur~ ~oves to Step 31~. At Step 30c, two threshold valùes TH8 and TH16 are cal~ul~ted. The thresho]d value T~1~ for A~ demodu'ation i~ fed at Step 306 from the de~odulution ~ontr~lle~ 231 to both the fir~t 136 and the sec~nd discr-i~ination/re~roduction ci~cnit 137.
Hence, de~odulation of ~he modi~ied 16 QAM signal and reproductio~ of th~ 6eco~d dat~ stream can be carricd Otlt at Steps 307 ~rld 316 respeetively. At Stap 30B, the error rate is exa~ined and if high, the procedure returns to Step 31 for repeating the 4 PS~ demod~laticn.
As shown in Fi~. 22, the signal points 85, 8~. are aligned on ~ line at An angle of cos~t+rn/2) w~i.Le B~ and a6 are of~ the line. He~lce, the feedback o~ a serond data stream tran~mitting carrier wave dAta from t~e cecond d~ta stream reproducing unit 253 to a carrier reproducl~g circuit 4~

.~S3 3,~ ~ .?~ ;, i, 4, ~. .,,30, 2 0 3 2 4 9 ~

131 iB carried out so that no carrier ~leeds -~o be e~tract~d at the ti~ing of the ~ig~al points 84 and 86.
The tr~nsmitter 1 i6 arranged to transmit carrier timirlg sign~ls at interval~ of R given time with the first data S stream ~or th~ purpo~e of compensation for no demodulation of the second data ~tream. The carrier timing ~ign~l enables to identify the signal points 83 and 85 of the first d~ta ~tream regardle66 of demodul~tion of the second data ~tream. Hence, the reprodu~tion of carrier Ylave can be triggered by the tr~ns~itting carrier ~at~ to the carri~r r~producing circuit 131.
It is then ex~mined at Step 30~ of the flow chart of Fig. 24 whether m i~ 16 or not upon receipt of such a modi~i~d 64 Q~M sign~l as shown in Fig. 23. At Step 310, it is al90 e~amined whether m is more than 64 or not. If it is determined ~t St,ep 311 that the receivQd signa] has no equal dist~nce signal point constellution, the proced~re goe6 to Step 312. The sign~l point dlstance TH~ of the modified 64 QAM signal is calculated from:
TH~ = ~Al+A2/2)/(Al+A2) This calculation is equivalent to that of T~16 but its resultant distanc~ between slgnal poi~t8 i8 a~aller.
If the signal point distaDce ln the fir~t ~ub segment 181 is A3, the di&tance between the fir~'~ 181 and ~he second 25 sub ~egment 182 is ~xpressed ~y (~2~2A3). ~hen, the ~ver~ge dist~nce is ~A2-2A3)/(Al+A2) which is designated as d~. When d~ is ~maller than T2 which represents the signal point 4~

-- 2~9~

discri~ln~tion espability of the second receiver 33, arly two sign~l points in th~, se2ment will hardly be di~tinguished fro~ each other. 'rhis judge~ent i8 e~ecute~ at Step 313. I$
d~ ~e out of a p~r~issi~e ran~e, the procedur~ ~oves back to S Step 313 ~OI' 4 PSK mode demodL11ation. If d~ is within the ra~lge, the procedure advar~ce~ to Step 3~5 for Rllowing the d~modulation of 16 QAM at ~tep 307. If it is d~termined at Step 308 t~aG the error rate is too hi~h, the procedurP goes back to 5tep 313 for 4 PSK mode d~odulation.
10When the transmitter 1 supplied a modifi~d 8 QAM signal such &s ~ho~n in Fig. 25(a) in ~hich all t.he sigTlal points are at angles of ~os(2~f+n ~/4~, the carrier waves of the signal are lengthened to the same ph~se and will thus be reproduced with much ease. At the time, two-bit dat~ of the first dat~ stre~m are demodulated with the 4-PS~ receiver while one-bi' data ~f the second data stream is demodulated with -the second receiver 33 and the total of three-bit d~ta can be reproduced.
The third rec~iv~r 43 will b~ described in more detsil.
Fig. 26 shows a block diagram of the third receiver 43 simil~r to thut of the second rcc~ver 33 ln Fig. 21. ~he dlfference 1~ that ~ third data stream reproducin~ unit 234 is added a~d also, the discri~inationJreproduction circuit has a capa~ility of identifying eight-bit dsta. The antenna 254Z of the tnird recei~er 43 ha~ B radius r3 greater Ihun r2 thus allowlng smaller distanc~ ~tat.e signals, e.g. 32- or 64-stat~ QAM signals, to be demodulated For demodula~ion ol the ; 3 U 3~ v ; 73~ tI ~ J ''', '' ' ;' ' I~J :' ~ 2~9249~

64 QAM signal, the first discri~inationJreproduction oircuit 13B has to identify 8 digital levels of the detected signal in which ~even dif~erent thre~hold levels &re involved. As or~e of the threshoi.d values is zero, throe are ~ontained in 5 th~ f irst quadrant.
Fig. 27 ahows a space diagram of the sign~l in which the -~jrst qu~drant contalns three diff~rent threshold values.
Ae shows in Fig. 27, when the three normalized threshold values are THl~, TH2~, ~nd TH3~, they are expressed by:
1~ THl~ = (Al+A3~2)/(Al+A2) TH2~ = (Al~A2~2~/(Al+Az~ ~nd TH3~ - (Al~A2-A3f2)/(~l+A~)-Through AM demodulation of a ph&se detected signal usingthe three threshold values, the third data stream can be reproduced li~e the first and second data stream explained with Fig. 21. The third data stream contains e.~. four signal points 201, ao2, 203, 204 at t~e first sub seg~ent 1~1 s~own in Fig. 29 which repreYent 4 valuec of two-bit pattern.
Hen~e, ~i~. digits or modified 64 QAM signals can be demodu!ated.
The demodul~tion co~troller 231 detects the value m, Al, A2, and A3 from th~ de~odulatio~ dat~ cor~tained in the first data str~m de~odulated at the first data s~re~m reproducing uuit 232 ~d calcu~ates the three thrashold value6 THl~, T~2~, ~nd TH3~ which are the~ fed to the first ~36 and the second discrimination/reproduction clrcuit 13~7 s~ that the mod~fied &4 4A~ signhl is de~odulated with certairt7. Also, ~6 . ~ S 3~ ~ ~ 2 ~l a . 7~ t j~

' 20~2~9~

if the demodulation data have beer. scrambled, the mo~lfied 64 4AM si~nal can be demodulcted only with a specific or subscriber r~ceiver Fig. 28 is a flow chart showing the action of the demod~lation controller 23i for modi~ied 64 QAM
~ignQl~. Thc differen~e from the flow ehitrt Eor de~odulatior nf 16 Q~M shown in Fig. 24 will be explained. The procedure moves fr~m ,Step 304 to Step 320 where it i9 examined whether m=32 or ~ot. I~ m=32, demodulation of 32 Q~M signals is ex~cuted at Step 322. If not, the procedure ~oves to St~p 3~1 ~here it i~ e~amined ~hether m=6~ r not. If ~-e~, A3 ic exami~ed at Step 323. If A3 is B~l Ler than a p~ede-cermined value, the ~rocedure ~oves to Step 3Q5 and the sa~e sequenc~
as of ~ig. 24 i~ implemented. If it ..s jud~e~i a~ ~tep 323 that A3 is not sm~ller than the predetermined value, the procedure goee to Stcp 324 where t.he threshold vaiues are calculated. At ~tep 325, the calculated threshold valuee arc fed to the ~irst and second discrimln~tion~repr~duction circuits and at St~p 326, tha de~odulation of the ~odified 64 QAM 6ignaL i~ cArried ~ut. Then, the fi.rst, ~econd, and third data stream~ are reproduced at Stqp 3Z7. At Step 328, the error rate is examined. If the error ratQ is high, the proe~dure moves to Step 305 where the 16 QA~ de~odul~tion is repe~ed and if low, the ~emudulation o~ the 64 QAM is co~tlnued.
The action of carrier wave reproductiu~ needed for e~acution of a satls~c-t.ory de~ollulati~g procedur~ will now ~e described. *he scope o~ the preaent inventiol~ iaclude~

~7 ~ r ~ ~ 3 ~ 2, ~ D~ 3~

~'092~

reproduction of the first data strea~ of a ~odi~ied 1~ or 64 QAM sign~l with the use of a 4 PSh receiver. However, com~on 4 PS~ receiver rarely reConstlUCtS carrier waves, thus faili~g to perform a correct demodulation. For compensatior., some arr~n~ement~ are necessary at bol.h the trans~itter and recaiver 6ides~
Two techniquefi for the co~.pens~tio~ are provid~d according to the present invention. A first techniq~e relates to trans~is6ion of signal points aLigned at angles ~f (~n-1)~/4 at i~tervals of Q ~i~en time. A ~eoond technique o~ferstransmlssioJl of ~ign~l points ar~anged at intervals of an angle of n~/8.
According to the first technique, the eight signal pointa including 83 an~ B5 are aligned at ~ngles of ~/4, 3~/4, 6~/4, and 7~/4, as snown in Fig. 3R. In ~ction, at leaBt one of the eight signal points is transmitted during sync time slot periods 452, 453, 454, 455 arrsnBed at equal irtervals of a time ln a time slot gap 451 shown in the time chart of Fig. 38. Any desirQd signal points are tranfimitted during the other time slots. The transmitter 1 is al~o arran~ed to assign ~ data for the ti~e slot interval to the sync timing dat~ region 499 ~f a sync d~ta block, as shown in Fig. 41.
The content of a trangmit~ing sig~al will be e~pla~ned in ~orc detail referr~ng to Fig. 41. ~he time ~lot group 451 containing the ~ync time ~lots 452, 453, 454, 455 repres~nts a urit data ~tream or block 491 carrying a data of DI~.

i3S3~ 3~ ~9 ~ @~ D ~ I ~ . . . 4~ 30, 2~2~9~

I'h~ ~ync ti~e 610ts in the si~nal are arranged at equal inter~alR of ~ given time determined by the time ~lot int~rval or sync timing ~ta. Her~ce, when thP arrangement of the sync time slots is detected, reproduction of carrier wave~ will be ~xecllted slot by slot thro~gh e~tracting the sync ti~ing d~ta i'ro~ th~ir respective time 910ts.
Such a sync timing datA S is contai~ed in a sync block 493 accompani~d ~t the :front end of a dat~ frame 492, which i8 consisted of a rlumber of the ~ync time slots deno~ed by the 1~ hatching in Fig. 41. Accordinglyl the data to be extra~ted for carrier w~ve reproduc-tion are increased, thus alLowing the 4 PSK rec~iver to reproduce de~ired carrier w~ves at hi.gher ac~uracy and effic3.e~cy.
The ~ync block 493 comprises SyDc data regions 496, 497, 15 498,---contairling sync data Sl, S~, S3,---resPectivel~ which include unique words and demodulation d~ta. '~he phase sync clgnal as~ign~eDt region 499 is accompanied at the e~d of the sync block 493, which holds a data of IT including infor~ation about interval arrangement and sssignment o~ the 20 OEync ti.me ~lots.
The ~ig~al point da~a in the phase cync time 510t has a parti CulAr ph~se and can thus be reproduced by th~ 4 PSK
receiver. Accordingly, JT in the pha~e sync signal u~si~nment regiorl 499 can be re~rie~ed w~thcut error thu~ ensurin~ the reproductlon of c~rrier wave~ at accuracy.
As sho~n in Fig. 41, the 6y~c block 493 is ~'ollowed by a dcmodul~tioD data block 501 which contuins demodulation v ~ J ~ 5" ! 7 ~ S~ 3 0 1 - 2~92495 ':
data about threshold voltages needed for de~odulation of the ~odified ~ulti~le-bit QAM si~nal. ~his data ls esse~tial for demodulation of the multiple-bit QAM 6 ignal and may preferably be contained in ~ re~ion 532 which is a part of 5 the sync block k93 ~or ease of ret.riHv~l.
Fi~. 42 shows the as~ign~ent of sigrl~l data for trans~issiorl of burst form fiignals through ~ TDMA method.
The a~slgnment i8 di~tingui6hed from that of Fig. 41 by the fact that a ~uard period 521 is lnserte~ b~tween ~ny two adjacent Dn data blocks ~1, 491 ~or interruption of the 6ignal transmission. Also, each data bloc~ 491 accompanied at front erld a sync region 522 thus formlng a data block 492. During the sync region 522, the si~nal points at a ph~6e of ~2n~ /4 are only transmitted.
Ac~ordingly1 tha carrier w8ve reproduction will be feasible with the 4 PS~ raceiver. More specificPlly, the ~ync signal and carrier waves can be reproduced through the TDMA method.
~ h~ earrier wave reproduetion of th~ f irst recei~er 23 ~hown in Fig. lg will ~e e~plained in more detail referring to Figs. 43 and 44. As shown in P'ig. 43, an i~put signal is fed through the input unit 24 to a synr detector circuit 541 where it is s~nc detected. A de~odulated ~ignal from the sync de~ertor 541 is tr~nsferred to an output circuit 542 for reproduction o~ tne first data ~crea~. A data of the phase ~5 sync ~ignal ~s~igr~ent data region 499 (shown in F'ig. 41) is retrieved with an extracting timing controller clrcuit 543 so th~t thc ti.ming of sync signals of (2n~ 4 data can be ' ~S~rr ~ 3 'I~t~ r'!;i~ o ~ ~t' .V~ ?
2~49~

arkllowledged and ~r~nsfe~red bs a phasf~ sync c oJ~trol pulse 561 showr. in E'ig. 44 to a carr er reprod~lctiorl rorltroLIing circuit 544. Also, the demodulated signal of the sync detector ~iI'CUit 541 is fed to ~ frequ~ney ~ultiplier circuit 545 where it l~ 4x ~ultiplied prior to transmitted t~ the carrier reproduction contro' ling circuit $44. The r~-ulta~t ~ignal denoted by 562 in Fig. 44 contuil~s a true pha~ data 563 aud other data. As illustrated .n a time ch~rt 5~4 of Fig. 44, the ph~se Syl-c tl~e slGt~ 452 c~rrying the (2u~ J~
d~t~ ar0 slso cont~ired at equal inter~ . At tha carrier reproducing controllir.g circuit 544, the ~ignal 562 i8 sampled by the pha6e sync control pulse $61 to produce a phase sa~ple ~i~rlal 56S which i s then converted through sQm~le-hold action to A phase signal 566. The phase signal ~66 of the carrier reproducti~n controlling circuit 544 ~s fed across H locp f ilter ~46 to d VCO 547 where its relevant carrisr war,e ls reproduced. Th~ raproduced rarrier is ther sent to the BynC detector circuit 54~.
In this manner, the signal point d~t~ of th~ (2n~ /4 phase denoted ~y the shaded area~ in Fig. 3~ is recovered and utilized BO that a correct carrier wave can be reproduced by 4x or 16x frequency ~ulti~lication. Althou~h a pl~lrality of Ph~9es are repro~uced at the ti~e, the absolu~e phases of the carrier Can be succest~fullJr be l~enti~ied with the used o$ a 2~ UniquQ w~rd ass~tgned to Lhe sy~c re~lon 496 shor,-~n in Fig. 41.
~ 'or transsnlssloTl of ~ modifietl ~4 QAM r ignal such ~.s shown in ~ig. 4n ~ signa1 points ir. the phase synr areas 471 ! 9 9 3 ~ ' rl ~ 7~ t .. ~ t~ t~ N Q, ! ~ 4 2 ~ ~ 3/ 3 0 ~

. 2092495 at the (2n~ /4 phase denoted b~ the hat~h~g are a~signed to the sync time slot6 452, 452b, etc. Its carrier can be reproduced hardly with a common 4 P9K receiver but successfully with the first receiver 23 of 4 PSR mode provided with th~s c.arrier reproducinz circuit of the embodiment.
The foregoing carrier reproducing ci~cuit is of COSTAS
type. A cnrrier reproducing circuit of reverse modulation type will now bs explained according to the embodiment.
Fig. 45 shows a rever~e modulation ty~e carrier reproducir~g circuit according to the present invention, in which a received signal is fed from the i~put ~it 24 to a sync detector circuit 541 for producing a demodulated ~ignal.
A1BO, the input ~ignal is delayed by a first delay circuit 591 to a delay sienal. The delaY signal i8 then tranq~erred to a qu~drature phase modulator circuit 592 where it i~
rever~e demodulated by the demodulated signal from the sY~c detector circuit 541 to a carrier signal. The carrier signal is fed through a r~rrier reproduction controller circuit 544 to 8 phase comparntor 593. A carrier wave produced by ~ VCO
547 iB delaycd by a second delay circuit 594 to n delay sign~l whieh iOE also fed to the phnse comparator 593. At the phase comparator 594, tbe reverse demodulated c~rrier si~nal i6 compared i~ phase with the delaY signal thua produci~g a phase di~ference signal. ~he phase differenc~s si~nal aent through ~ loop filter 546 to the YCO ~47 which in turn producea a carrier wave arranged in phase with the received 2~9249~

carrler wave. I~ the same marlner as uf the COSl'AS carrler reproducing cir~uit shown irl Fig. 43, an e~tracti~g timing eontroller cireuit 543 parfor~s sampling of signal points eorltained i.n the h~tching area& of Fig. 3~. Accordingly, the carrier wave of a 16 or 64 Q~ signa1 can be repr~duced with the 4 P8~ demGdulator o~ the first r~ceiver 23.
The reproductiorl of a carri~r wave ~y lBx frequen~y multiyiicatior will be e~plained~ The transmitter 1 shown in Fi~. 1 is arranged to llodulate and transmit a modified 16 QAM
si6~al with as~igr~ent of its signal points at n~8 phase as shown in Fig. A6. At the ~irst receivar 23 sho~ in Fig. 19, the carr~er wave can ~e reproduced with it~ COSTAS carrier reproduction controller circuit containing a 16x multiplier circuit 661 sho~n in Fig. 4~. The signal points at e~ch n~t8 lS phase shown in Fig. 46 are processe~ at the first quadrant the action of t~e 16~ ~ultiplier circuit 661, whereby the carrier will be reproduced by the combination of a loop filter 546 a~d a VCO 541. Also, the ~bsolute phase may be determined ~rom 16 dlfferent pha~es by assigning a unique word to the sync region.
Th~ arra~geme~t of Lhe 16x multiplier circuit will be e~plained referrirg to Fig. 48. A sum signal and a difference signal are produced from the demodul~ted slgral by an adder circuit 6ff2 and a s~tracter circuit 663 respectively ~nd then, multiplied ea~h other by a mul~iplier 664 to a c09 2 ~ignal. Also, a mul~iplier 665 produces a siu ~ signal. I'he two sig~al~ are then ~ultiplied by a multiplier 66ff to a sin ~3 2 5 ~ t,~ N ~ 3 P. ~ 5 ~
209249~

4~ signal.
Si~il~rly, a sin sa si~nal is produced from the two, sin 2~ and c03 2~, ~ignals by the combination o~ sn adder rircuit ~6~, a fiubtracter circuit 668, and a Lultiplier 670.
5 Further~ore, a ~in 16~ signal is produced by the combination o~ ar. adder circuit 671, a ~ubtracter ci~cuit 672, and a m~ltiplier 673. Then, the 16I multip~ication is co~pleted.
~ hrough th~ foregoing 16~ mult~plication, the carrier wave of all the sig~al poir.ts of ~he ~odified 1~ QAM sigllal sho~n in Fig. 46 will gucce6~ullY be reproduced without extracting particular ignal polnts.
~ owever, reproduction of the carrier wave of the modif ied 64 QAM signal shown in ~'ig. 47 can involve an increase in the error rate due to di~locat1on of some s~gnal poirlts from the sync areas 471.
Two techniques are known for compen~ation for the consequences. One iB inhibiting trans~is~ion o~ the sign~l pgirt6 dislocated from the sync sreas. ~his cause~ the total amourLt of tran~mitt~d dAta to be reduced but allows th~
arrange~ent to be facilitated. The other i6 providing the SylIr ti~e slots ar descrlbed in Fig. 3~. In more particular, the sig~al point~ in the n~8 eync phe~e areas, e.~. 471 and 4~1a, are tr~nsmitted during the period o~ the correspondin~
~ync time slots in the time slot gro~p 4~1. This triggers an ~S accurat~ ~ynchronizing action during the period thus minlmizing phase error.
As r.o~ understood, the 16x ml~ltiplicatio~ allows the - 2~924~

simpl~ 4 PSK receiver to reproduce the carrier wave of a ~odified '6 or 64 QAM signal. Also, the insertion of the sync tir~e slots causes the phasic accuracy to be increa~ed during the reproduction of carrier waves fro~ a m~dified 64 ~AM ~ignal.
A~ set forth Above, the signal ~ransmi6eion ~ystem of the preG~nt invention is cap~le of transmitting a plurali~y of dat~ on a .sin~le carrier wave simult~neously in the mult,ipl~ signal level arrangement.
More s~ecifically, three diffese,nt level r~ceivers which have discr~te characteri6tics of sign~l intercepting sensitivity and ~emo~ulating capabilit~ are provided in relation to one single transmitter ~o th~t any one of the~
c~n be ~ele~t~d depending ~n a want~d data size to 'oe demodulatsd whi~h is propnrtior~al to tha price. When the first receiver of low resolution quality a~d low price i~
Acqulred together with a sm~ll antenna, its owner can intercept and reproduce t~1e first dat~ streem of a transmi~ion signal. Whel1 the second re~eiver of ~edium resolution quality and mediu~ price is acquired tegether with a m~di~m ant~nna, its owner can in-tcrcept alld reprod~ce both the fir~t and second data strea~s of the ~igna~. When the third receiv~r of hi~h resolutio:1 ~u~.lity ~nd hi~h prlr,e is acquire~ with a large anteIma, its owner can interrept ~nd reproduce al] the fi.rst, second, and third data streams of the sigDal.
If the .~i.rst receiver is a ho~e-use digital satellite iu~3~ '5~ l @~ ~'4~ 5 '~0~

2~9%~

broadcait receiver of low price, it will overwhel~ing1y be welcome by a majority of viewers. The second receiver acco~panied with the medium antenna cost~ more a1ld will be accepted by not co~mon viewers bnt particular people who wants to enjoy HDTV services. The third recei~er acc~ ~nied with the large anteslna at l~ast before the fiat~l~ite output is increaeed, is not appropriated Ior home use and will po~sibly be used in relevant industries. For example, the third data stream carrying super HDTV signals is transmitted via a s~tellite to subscriber cinemas which can thus play video tapes rather than traditiou~l movie films and ~un movies buslness at low cost.
When the present invention is applied to ~ TV sign~l transmi66ion service, three differen~ quality pictures are carried on one signal chaDnel wave ~nd will offer compatibility with each othsr. Although the first e~bodiment refers to a 4 PSK, A modified 8 QAM, a modified 16 QAM, aDd a modified ~4 QAM slgnal, other ~ignals will al60 be e~ployed with equal success including a 3~ QA~, a 256 QAM, an 8 PSK, a 16 PSX, a 32 PSK signal. It would be understood th~t the present inventioI~ is not li~ited to a satellite tran~mi~sion sy~tem and will oe applied to a terrestrial communicatiou6 sy~tem or a cable transmis6ion system.
~mh~di~e~-t 2 A second e~bodiment of the present invention is featured in which the ph~sical multi-level arrangerlent of the first embodiment is divided into small levels through e.g.

~c3~ 33 ~5 7~ ; É~ " . 3~ 3~
2~24~

disc~ri~ination in error correction eapability, thus forming a logic ~ult;--level construction In the first embodiment, each ~nlti-level channel has different 'evels in the electric sign~l Amplitude or ph~sical de~dulating capability The ~eeond embodim~nt of~ers different levels irl the logic reprod~ction capability such ~s error correction Fcr example, the data Dlin a multl-level channel is divided into two, D]_l and Dl_2, eomponents And Dll is msre increased in the error sorrectlon ~ap~bility th~n Dl_2 for di~cri~ination ~0 Accordingly, as the error detection and correction capability is differerlt between Dl_l and Dl_2 et demodulation, Dl_l can suecessfully be re~roduced ~ithin a given error rute when the C/N level of an origln~l transmitting signal is as lo-w as dise~a~lin~ the reproduetion of Dl2~ Thi~ w~l1 be implemented uBin~ the l~gic multi-lavel arrangement More specifically, the logie multi-level arrangement is consist~d uf dividing data of a modul~ted ~ulti-level channel and discriminating dis~ances between error correet on eodss by mixing error eorrectio~ codes with product codes for varyin~ error correcti~Jl c~pability. He~ce, a more multi-level signal ~an be transmitte~
ln fact, ~ Dl channel is divided irto two sub ebannels D~ nd D~2 ~nd a D2 channel is divided into ~wo sub channels D2~l and D2-2 This will be explained in more detail re~arrinK to Fig 8~ in which Dll is reproduced ~rom a lowest C~N fiignal If the C/N rate is d at ~inimum, three co~ponents Dl_~, D2_l and 2~9~49~

D~-2 cannot be reproduced while Di1 is reproduced. I~ C/~ is not less than c, D12 e~n also be reproduced. Equslly, when C/N is b, Dz_l is reprodu-:ed and when C/~ is a, Dz_z is reproduced. As the CtN rute incre~sas, the reproducihl~
signal levels ~re increased in number. The lower the CJ~, the fewer the reproducibie sigr,al levels. This will be explained in the form of relation between tran~mittinB distance and reproducible C/N value referring to Fig. 86. In co~mon, the C/N value of a received signal is decressed in proportion to the dis~ance of transmis610n as expr~sed by the real line 8B1 in Fig. B6. It is ~ow assumed that the distance from a transmitter antenna t~ a receiver antenna is La when C~N=a, Lb whe~l C/~=b, ~c when C/~=c, Ld when C/N=~, and Le when C/N=e. If the distance from the trans~itter antenna is greater than Ld, V11 can be reproduced as sho~n ln Fig. 85 ~here the receiva~le urea B62 is d~noted by the hatching. In otller ~ords, D1_1 can be reproduced within a most e~tendsd area. Si~ilarly, Dl2 ean be reproduced in ~n ~rea 863 wher.
the distAnce is not more th~n Lc. In this area 863 containing the are~ 8~2, D1_1 can with no doubt ba reprvdured. In a small ~reA 8~4, D2_1 can be reproduced And in a smallest area 865, DZ-2 can be reproduceci. As und~r~tood, the different data lsvels of a chan~el can be reproduced corresponding to degree~ Or declination ln the C/~ rute. The logic multi-level Arrallgement of the signal transmission sy~tem of the prese~t invention can provide the sa~e effect as of a traditional ~n~logue transmission s~stem 1ll which th amount of receiv~ble .S~J~ l~2~ 3~ L~ 3 - Ar ~-2092~9~

data i~ gradually lowered as the C~ rate decreQse~.
The constru~tion of the logic multi-level arrangement will be described in whlch th~re are provided t~o physical levels and two l~gic le~el~. Fig. 87 is a ~lock dia~ram of a S transmitt~r l which is su~ctar.ciaily identïcal in construccion to that shown ir Fig. ~ and des~ribed previously in the fir~t ernbodime~lt and wil~ no further be explained in detail. The only dl~rersrlce is tha~ error correction code encoders are adde~ ~6 ~bbrevi~t~d to ECC ~c~er~ The div;der cir~uit 3 has fcur outputs 1~ 2, 2-1, and 2-2 through which four ~ignals Dl~, Dl2, D2_~, and D2_~ dividcd from an input ~ignAl are del'vered. 1'~e two ~ignals D1_1 and Di_2 are fed to two, mair. and sub, ECC encoders 872a, a73a of a fir~t EC~ encoder 871a respectively ~or cnn-~erti~g to error correction code forms.
The ~in ECC sncoder 87'a ha~ ~ bigher errcr correetion capability than that o~ the sub ECC encnder ~73a. Hence, D1_ can be raproduced at a lower rate of 5/N than Dl2 Ps apparent fro~ the CN-level dia~ram of Fig. 8~. Mure p~rticul~rly, the logic level of Dl_1 is le~s affected by dEclillation o~ the C/~
th~n th~t of Dl2. After error corr~ction code e~coding, Dl1 and Dl_~ Qre ~ummed by a summer 87~a to a Dl signal which is th~n transrerred t,c the ~odulacor 4. rh~ olher t~o slgnalfi ~2-1 and D2, of the divider CiI'C.~lt 3 are errur corr~tion encoded by t~o, mai~ and su~, ECC encoders 872b, 8~3b of a second ~CC encoder 871b respectivelY and then, su~led by sum~er 874b to a l~2 slgna. whlch i~ trallsmitted to th~
_g ~3''. ~q2~ i7~ T~ . .34~ . S ~0~

..
modulator 4. The main ECC encoder 872b i6 hi~her in the error correction capability thar, the sub ECC enco~er B73b.
The modul~tor 4 ir, turn produces from the two, D1 and D2, iTlpUt si~nal6 a ~ulti-level ~odulated ~ignal which is further transmitted from the transmitter Ullit 5. As understood, the output signal from the transmitter 1 ha~ two physical levels D1 and D2 and al~o, four logic levels ~ D1_2. D2_1, and D22 baged OTl the two physical levels for providing dif.f~rent error correction capabillties.
The reception of such a multi-level signal will be e~plained. ~ig. 88 is a block diagram of a secorld receiver 33 which i~ almost identical in con~truction to that shown in Fi8. 21 and described in the f~rst embodiment. The second receiver 33 arr~ng~d for iD~erceptin~ multi-level sig~al~
from the transmitter 1 shown in Fig. 87 further comprises a first 87aa and a ~econd ECC decodsr 876b, in which the demodulation of QAM, or any of ASK, PSX, and FSK if desired, is e~ec~lted.
As shown in Fig. 8&, a receiver si~nal is deTuodulated by the demodulator 35 to *he two, D1 and Dz, 6ignal~ which are then fed to two dividerfi 3a and 3b respectively where they are divided into four logic levels D11, D~2, Dz_l, and D2_2. Th~
four ~ign~ls are transferred to thP first 878a and the second ECC decoder 876b in which Dl_1 i5 error ~orrected by a ~ain 25 ECC decoder 877a, Dl2 by a 6ub ~C~ decoder 878a, D21 ~Y a main ~C de~oder 877b, D22 b~ a sub ECC decoder 878b before all sent to ths summer 37. At the su~er 37, the four, D

~''3 .~2~ +~ 2~fl~

2~9249~

D~2, Dzt~ and D22, ~rror correctPd signal~ are ~u~med to a 5ignal ~hlch i~ t~nen ~elivered fro~ the output unit 36.
Since Dl1 arLd n~-l are higher in the urror ccrrection capability than Dl.. ~-ld D2_2 respectively, tbe error rate 5 remairl6 les6 than ' giveli value although C/N i9 fairl~ low as ~hown in Fig. 85 and thus, an original signal will be repro~ueed success~ully.
The ~ctlon uf dLscrimirLating t~e error correction capabi.lity between th~ ~in EC~ decoders 877a, 877b and the sub ECC decodQr~ 878a, 87~b will now be described in ~ore detail. IL i~ a good idea for having a difference in the error correction capability to use ln the sub ECC decoder a coTnmon coding technique, e.g. Reed-Soiomon or BCH method, ha~in~ a st~nd~rd code distance and in the main ECC decoder, an~ther encodin~ ~chnique in which the distance be~ween correction codes i9 increa6ed using Reed-Solomon code6, thelr product code~, or other long-len~th codes. A variety of known techniques Por increasing the error correction code distance have been ilLtroduced ~nd will no moro e~plained. The present in~entiun can be associated with any known technique ~or h~vin~ the logic ~lti-level arran~ement.
The logic multi-le~el arrarLgement will be ex~lained i~
conjunction ~ h a diagram OT- Fig. 89 showing the relation between C/N and error rate after eIror correction. As shown, the stralght line 881 Iepresents ~1-l at the C~N and error rate reLation an~ the line 882 represents Dl_2 at same.
Ai th0 C/N rate of an input sigual decre~Lses, t}le error 2 ~ .~J~OT~Y~ li ~, ; j ~ ~ ., '~, i ' il;
2'092~95 rate increases aEter error correctlon. If C/N is lower than a ~iverl value, the error rate exceed~ a reference value Eth determi~ed by the Byete~ design ~tandards and no original data wlll normally be reconstru~ted. When C/N is lowered to le~s than el the Dl Rlgnal fails to he reproduced ~8 expre~3s~d by the line 881 of ~l-l in ~ig. 8~. When eSC~N~d, ~1-l ~~ the Dl ~ig~al e~hibits a higher error rate than Eth and will not bs reproduced.
When C/N is d at the poi~t 485d, Dl_l having a hi~her error eorrectioA cap~bi1ity than Dl~ becomes not higher in the error rate than Eth and can ~e reProduced. At the time, the error r~te of ~12 remains higher than Eth a~ter error correction Qnd will no lo~er be reproduced.
When C/~ ls increased up to c at the point 88~c, Dl2 1~ becomes not higher in the error rate th~n Eth and can be reproduced. At the time, D21 and D22 re~ain in no demodulatiou ~tate. After the C~N rAte i9 increa~ed further to b', the D2 sign~1 become~ ready to be de~odulated.
~hen CJN is increased to b B~ the point 885b, D2l of the D2 signal becomes not hi~her in the error rate than Eth and ca~ be reproduced. At the time, the error ra~e of Dz_2 remains hi~her than E~ and will not ~e reproduced. When C/N is incre~sed up to a at the point 8~5a, D22 beco~es not higher than Eth a~d can be reproduced.
2~ As described above, the four differen~ signal logic level~ divid0d ~ro~ two, Dl and D2, physical levels through discrimirlation ~f the error ~orrection cap~bility bet~-een the ~2 : 2Q924~

level~ can be tr~nsritted simultanenusly.
Usi~ the loKic Lulti-level arrangemeDt of the pr~6ent invention in accompnny with a ~ulti~l~vel construetion in which at lsast a part of the ori~inal signnl is reproduced even if data in a higher level i8 lo~t, digital signal tran6mi~sion will succe~6fully be e~ecuted without losing the advnntageoua e~fect of an analogue signal ~ran~mission in which tra~smitting d~tn is grndually decres6ed as the C~N
rate becomes low.
Thanking to up-to-dat~ im~g8 data compres~ien tech~ique~, co~pressed i~rge datQ can ~e transmitted in the logic multi-level arr~ngement for er,abling n re~eiver station to reproduce a higher quality i~age than that of ~n nralogue sy6tem and also, with not ~harply bu~ at StP,p~ deelining the 6ignal l~vel for en~uring signal interception in ~ wider area. The present invention can provide an e~tra ee~ect of the m~lti l~y~r ar~ange~ent which iR hardly imple~ented by a ~nown digital signal transmission 6ystem without deterioratlng high quality image data.
Embodi~lent 3 A third embodiment of the present ln~eIltio~ will be described re~erri~g to the rele-art drawings.
~ ig. 29 is n schematic tGts! view i]lustrating tne third embodiment ln the form of a digital T~ broadcastir.g system.
An lnput video signal 402 of super high resolutioIl T~7 image is ~ed to Rn input unit 403 oE a first vide~ eneodLsr 401.
Then, the signal is divided by a divider circuit IQ4 into . 3 5 3 ~ 5 ~ zl~ li . . 3 ~

~Q92495 three, first, second, and third, dat~ streams whieh sre trans~itted to a compresfiing cir~uit 405 for data compresslon before further delivered.
Equally, other three input video signals 406, 407, and 408 are fed to a second 409, a third 410, and a fo~rth video encoder 411 re~pectively ~hich all are arranged identical in construction to the first video encoder 401 for data compressio~.
The ~our first data strea~s from their respective encoders 401, 409, 410, ~11 are transferred to a first multiplexer 413 of a multiplexer 412 where they are time multiplexed by TD~ process to a first data stream multiple~
signal which is fed to a trarlsmitter 1.
A part or all of the ~our se~ond data streams from their re~pective encod0rs 401, 409, 410, 411 are transferred to a second multiple~er ~14 of the multiple~er 412 where they are time multiple~ed to a second data stream multiplex signal which is then fed to the transmitter 1. Also, a part or all of the four thlrd dsta ~tre~ms are transferred to a third ~0 multiplexer 415 where they are time multiplexed t~ a third data strea~ multiple~ slgnal wkich i~ then fed to the transmitter 1.
The transmitter 1 perfor~ m~dulation of the three data stream signals with its modulator 4 by thP sa~e marmer as described in the ~irst e~bodimerlt. The modulated sign~l6 are sent frnm A transmitter unit 5 through an antenna 6 and an uplink 7 to a tr~nsponder 12 of B satellite 10 which in turn 2~9~49S

trans~its it to three different rec~ivers including ~ first reoeiver 23.
The modulated signal transmitted through a downlink 21 i~ intercepted by a ~all antenna 22 having 8 radius r1 and fed ~o a ~irst d~ta 6tr~am reprodu~ing unit 232 of the ~irst receiv2r ~3 where j~R fir~t data stre~ o~ly i8 demodula.ted.
The demod:llnted f~rst dat~ ~tream is ther, converted by a first video decoder 421 to ~ traditlonal 425 or wide-picture NTSC or video output si~ral 426 of low i~ge r~s~lution.
Also, the ~odulated signa! transmitted through a downlink 31 is intercepted by a medium antenna 32 h~vi~g a radlus r2 and fed to a first Z3~ and ~ Recond dat~ ~tresm reproduci~g ~Dit Z33 of a second receiver 33 where its first and second data streams are demodulated respectively. The demodulated first and secorld data strea~s are then summed and converted by a 8econd video decoder 422 to an HnTV or vidso output ~i~nal 427 of high image resolution and~or to the video output ~ignals 425 and 426.
Also, the modulated ~i~nal tran~mitted through a downlin~ A1 i~ int.ereepted by a large antenna 4Z having P
radius r3 and fed to a ~irst 232, a 6e~0nd 23S, and a third data otre~m reproducin~ unit 234 of a third receiver 43 where ~ts first, secon~, and third data streams are de~odulated re~pectively. The ~em~dulated first, ~eeond, and third dAts streams ~re then summed and converted hy a third video de~oder 4~3 to a super HDTV or video output signal 42B of sùper high image resolution for use in ~ video theater or n , ~ h7~ . ! 3 ~ ~ ? i ~
2~9.~49S~
cirlema 'rlle video output signals 425, 4~6, and 427 can also be .cproduced if dasired A common digital TV ~ignal is transmitted from a conventional digital transmitter 51 and when intercepted by the first receiver 23, will be converted 5 to t~L~ video output signal 426 such aR a low reRolution NTSC
TV signal Th~ ~irst video encoder 401 wlll now be explained in mor~ d~tail referri~g to the block di~gram of Fig 30. ~n i~put video si~nal o~ supcr high resolution is fed thr~ugh 10 the irput unit 403 to the divlder circuit 4~4 wherc it is divided into four compo~ents by sub-band cvding pro~ess. In ~or~ particular, the input video sigDal i~ separated through p~ssin~ a horizontal lowpass filer 451 ~nd a horizontal highpass filter 452 of e g. qMF mode t~ two, low and high, horizortal frequency componerts which are then ~ubsampled to a half of their quantities by two subsamplers 453 and 454 re~pectively. The low horizontal co~ponent i 8 filtered by a ~ertical lowpass filter 455 and A vertical highpass filter 456 to a low horizontal low vertical co~ponent or HLVL signal and a low horizont~l high vertical component or HlV~ sienal recpectively~ The two, HLVL and HLVR, signal6 are then subsa~pled to a half by two subs~mplers 457 ~nd 458 respectively and transferred to the compressing circuit 40~
The high horizontal component i~ filtered by a vertical 25 10WPBSS filter 459 ard a vertical highp~ss filter 460 to a high hori20ntal low v~rtical comporent or H~VL sign~l and a bigh horizontal high ~Jertical compor~ent or ~HV~ signal 2~92~3a respectivelg. The two, ~VL and H~V~, signals are then subsampled to a hal~ by two subsampl~rs 461 Hnd 462 respectively and transferred to the compre~sing circuit 435.
HLVL signal i~ pre~erably DCT comPre~q6ed by ~ fi.rst compressor 471 of the ~o~p~essing circuit 405 and fed to a flrst output 472 as the fir6t d~ta stream.
Also, HLV~ ~ignal ia compre~sed by a second compre~sor 473 and fed to a second o~tput 464 H~Y~ 31~nal i9 co~pressed by a third compre6sor 463 and fed to the seco~d output 464.
~aV~ ~ignal is d~vided by a divide-. 4~5 into twu, high resolution (HuV~l) and suFer high resolutlon (H~V~2), video sig~als which are then tra~ferred to the second output 464 and a thlrd output 468 respecti~ely-.
The first video decoder 4Zl wlll now be explail~ed in ~ore detail referring to Fig. ~1. The first data stream or signal of the firqt receiver 23 i9 fed through an input unit 501 to a descrambler ~02 of the first ~ideo decoder 421 w.here it is d~scrambled. The descrRmbled D~ signal i6 e~panded bY
an e~pander 5~3 to H~L which is t~en fed to an QSpect ratio changing circuit 504. Thus, HL~L signal can be delivered through an output unit 505 as a 3tandard 500, letterbox format 507, wide-screen 50B, or sidepanel format NTSC signal 509. The scanning format may be of non-interlace or interlace type a~d i~s NT~C mode lirA2s may be 525 or doubl~ tu 10~0 by double tru~l~g. When the received ~ignal from the digital transmltter ~1 ig Q digital TV signal of l PSK ~ode, it can also be converted by the first receiver 23 and the ~irst , 3~ q 17~' ?sj ~ ~o;~ Cl~
- 20~2~9~

video decoder 421 to H T~ pictur~. The second vLden decoder 42~ will be e~P~ined in more detaii referring to the ~lock diagram of Fig. 32. T~e Dl signal of the second receiver 33 is fed through ~ first input ~21 to a fi~st exparlder 522 for data expansion and then, transferred to an oversampler 523 where it i9 sampled at 2~. The oversamplad signal is filtered by a vertic~l lowp~ss ~ilter 524 to }IlVL. Also, the D2 signal of the second receiver 33 ie fed through ~ second input 530 to a divider 531 where it is divided into three components which are then transferred to a second 532, a third 533, and fourth e~pander 534 respectively ~or data e~p~nsion. The three expanded components are sampled ~t 2~ by three over~amplers 535, 536, 537 and filtered by a vertical highpaes 538, a vertical lowpass 539, and a vertical high-1~ pass filter S40 respectively. Then, HLV~ from the vertical lowpass fiiter 524 and HL~ from the vertieal highpass filter B3B are 6ummed by an ndder 525, sampled by an oversampler 541, and filtered by ~ horizontal lowp~ss filter 542 to a low frequency horizontal video signal. H~L fro~ the vertical lowpass filter 53~ and ~HV~l from the vertical highpass filter 540 are su~med by an ad~er 526, samplPd by an oversampler 544, and filtered by a horizorrtal highpass filter 545 to a hi~h frequency horizontal video sigr.a]. The two, high and low frequency, hori~ont~l video signal are then summed by an adder 543 t~ ~ high resolution video signal HD which i~
further transmitted through an OU~p'lt unit 546 ~s n video output 547 of e.g. HDTV format. If defiired a traditio~al ~TSC

; L f;i ~ r ~ L ~ 3 7~7~ ~g~ ~30~
209249~

video output c~n be reconstructed with ~qual succes6.
Fig. 33 is a block diagra~ of the third video deeoder 423 in which khe Dl and D2 signals are fed through a first 521 and A second illpUt 530 respectively to a high frequency band video decoder eircuit 627 where they are converted to an HD
signal by the sa~e ~m1er as above described. The D3 signal is fed through a third input 5Sl to a ~uper high frequeucy band video decoder circuit 5~2 where it i6 e~panded, descrambled, and composed to H~V~2 signal. The HD signal of the high freque~cy ba~d vldeo decoder circuit 527 and the H~V8Z sig~al of the super hlgh frequency band video decoder circuit 552 are summed by a ~ummer 553 to a super hlgh resoluti~n rv er S-E~ sign~l which i~ then deiivered through an output ur,it 554 a~ a sup~r resolution video output 555.
Th~ ~ctior~ of multiplexing in the multip]exer 412 shown in Fig. 2~ will be e~plained in ~ore detail. ~ig. 34 illustr~tes a d~ta ess;gnment in which the thre~, fir6t, seco~d, ~nd thirdI dat~ streams Dl, D2, D3 cont~in In a period of T si~ ~TSC cha~nel data Ll, L2, L3, L4, L5, L6, 9iX HDTV
chan~el data ~l, M2, M3, M4, M5, M6 and ~ix S-HDTV cha~nel data H1, H~J ~3 ~ H4, H5, ~ff re~pectively. In a~tior~, the ~TSC
or Dl signal dsta Ll to L6 are time ~ultiplexed by TDM
process duri~g the period T. ~or~ p~rticul~rly, HLVL of Dl i9 assigned to ~ domain 601 for the first chaDnel. The~, a differeilce dat~ ~1 bet~een HDTV and ~TSC or a sum ~f HLV~, H~VL. and H~VN1 is assig~ed to a domain ~0~ for the flrst Cha~QI. A1~OJ a difference data ~1 between HDTV and super 2 ~ t~ 1~ r, ~ . 7 . 3 i!
2~92~9~

HDT~ or ~V~ tSee Fig. 3~ Ps~igned to ~ domain 503 for the ~irst channel.
The selection of the first charmel TV signal will now ~e described When intercepted by the first receiver 23 with a small antenna collpled to the first video decoder 421, the f;rBt Challllel r~i8Ilal iB converted to ~ standArd or widescreen NTSC TV ~ignal ~s 6hown i~ Fig. 31. When intercepted by the second reeeiver 33 with ~ medi~m anten~a coupled to the second video decoder 422, the signal i~ converted by summing L1 of the flrst data 6tream D~ aLhigned to the dom~i~ 601 and Ml ~f the second data stream D2 assigned to the domain 602 to Bn HDTV sig~al of the first c~nne] equiv~lent ln program to the NTSC signal.
When intercepted by the third receiver 13 wl~h ~ large sntenna coupled to the third video decoder 423, the signal i8 converted ~y 6 ~ng L~ of Dl a6~igned to the domain 601, M1 of D2 assigned to the domain 6~2, and Hl o~ D3 assigned to the domain 603 to ~ super HDTV signal of the first chan~el equivalant in program to the NTSC signal. The other channel signals can be reproduced in an equal manner.
Fig. 35 6hows another data assignmen-t L1 of a first chann~l ~TSC signal is asslgned to a first domain 601. The domain 601 which is allocated ~t the Eront end Or the first d~ta ~tream ~1~ also contains at front a data S11 incl~ding a descrAmbling data snd the demodulation dat~ d~oI-ibed in the first embodiment. A firs* chanuel ~DTV signal is transmitted as L1 and ~I1. Ml which is thu6 ~ di~ference data l 3 ~ ~,rs, ~ 2 5 F~ ; 7 ?~ 3; ~r;)~ , 3 d,~ : 1 2 .l ~

21092~9a bst~een NTSC and ~DTV Is assigned to twn do~ain~ 602 nnd 611 of D2. If Ll i9 a compre~sed NTSC eomponent of 8 Mbps, M1 is es two times higher as 12 M~ps. Hence, the total of L1 and M1 can be de~odulated at 18 Mbps with the seco~d reeeiver 33 and the ~eco~d video decoder 423. Aeeording to ~urrent data compression technlques, HDTV compressed signals can be reprodueed at about 15 ~bps. This allow8 the data assign~ent shown in Fig. 35 to en~ble simultaneous reprod~ction of an NTSC and ~DTV first char~el signal. However, this as~ignment ~llows no seeond ehannel HDTV signal to be earried. S21 is a descr~mb1ing datH in the HDTV signal. A first channel super HDTV signal eomponent comprises Ll, M1, and Hl. The di~ferenee duta Hl is assi~ned to three domain~ ~03, 612, and 613 of D~,. If th~ NTSC signal is 6 Mbps, the ~uper HDTV is earried at as high as 36 Mbp6. When a eompressed rate i6 inereased, ~uper HDTV vidao data o~ about 20no seanning line for reproduetion o~ a einema 6ize pieture for eo~mereial use can be transmitted ~ith an equal manner.
Fig. 36 shows a further data HSsi~nment in whieh Hl of 20 H ~uper HDTV ~ignal i~ ~sei~ed to 8i~ ti~e~ dem~ins. If a NTSC eompr~ssed signal is 6 Mbps, this assigD~ent can earry as nine times higher as 54 Nbp~ of D3 data. Accordin~lY, super ~DTV data of higher picture quality ean ~e tran6mitted.
The foregoing data assigr~ent ~a~es the use of one of two, horizontal and vertleal, polarizativn plane~ of a tr~nsmission wave. When both the hcrizontai and vertical polHrizatioI~ plHnes are used, the frequency utilization will I~.v 3~-59 ~ t~ , ~ 4 u . . ~ / 3 0 5 ' 209249~

be doubled. This ~ill be e~plained below.
Fig. 49 6hows a data assignmert in which ~Yl and D~l are a -~ertic~l and a horizontal polarization signal of the first data stream respectively, ~2 ar,d D~ ara a vertical and 8 horizontal polarization signal of the second data stream respectively, and ~3 and D~3 are a verticsl and a horiz~ntal pol~ri~ation signal of the third data stream reRpectivoly.
The vertical polarization si~n~l D~l of the fir6t data stream carries a low frequency baud or NTSC TV data and thc horizontal polarizàtion signal D81 carries a high frequency band or H~TV data. When the fir~t recelver 23 is equipped with ~ vertical polari~ation artenna, it can reproduce ouly the NTSC signal. When the first receiver 23 is equipped with an Hntenna for both horizontallY and vertically polarized waves, it can reproduce the HDT~ signal through summlng Ll and Ml. More specifically, the first receiv~r 23 can prov~de compatibility between ~TSC and HDTV with the use of a particular type antann~.
Fig. 50 illustrates a TDMA method in which each data burst 721 is accompanied at front a ~ync data 731 ~nd a card data 741. Also, a frame sync data 720 i6 provided at the ~ront of ~ Xale. Like charnels are as~ignsd to like time 910t8. For example~ a Xirst ti~e sl~t 760 c~rries NTSC, HDTV, and super HDTV data of the first cha~nel simultaneously. ~he BiX time slo~s 750, 750a, 750b, 750c, 750d, 750e are arrang~d independent from each other. Xence, each station ca~ offer NTSC, HDTV, ~nd~or s~pper HDTV services independently o~ the r ~ 2 ~1 ~ 7~ 4 ~ ?. 1 ' '~, Q ~

209249~
-ether ~tat,ion~ through selecting a particular chan~el of the time slots. A160, the ~irst receiver 23 can reproduce an NTSC
signal when equipped with a horizontal p~larization anter~a and both NTSC and FIDTV signals when equipped with compatible pol~rization antenna. In this respect, the qecond receiver 33 cQn reproduce a ~uper HDTV at lower resolu4 iorA
while the third receiver 43 can reproduce a full super KDTV
6ign~1. According to the third embodiment, a co~patible cign~l tr~n~mi~sion ~ystem will be constructed. It i~
under~tood th~t the data a~signmer~t i8 ~ot limited to the burst mode TDMA method shown in Fig. 50 and another method such as time division multiplexing of contlnu~us sign~l~ as shown in Fig. 4~ will be employed with e~ual ~uccess. Aleo, a data as6ign~ent shown iII Fig. 51 will per~it a HD~V signal to be reproduc~d at high resolution.
A~ 6et forth ~bove, the compatible digltal TV ~ignal trnnsmission system of the third embodiment can offer three, ~uper HDT~r, KDTV, and conventional NTSC, T~ broadca~t service6 ~imultAnoou~ly. In addition, a video signal intercepted by a commercial station or cine~a ~an be electronized.
The modified oAM of the em~od~merts is nnw termed as SRQAM and it~ arror rate will be examined.
First, the error rate in 1~ SR4AM will be calculated.
~i~. 99 shows a ~ect.or diagram of 16 SRQAM signa] points. A~
apparent from the first qu~drant, the 16 si~nal points of ~tandard 16 Q~M including 83a, 83~1 84a, 83a are allocated at j J C ,, ~;~ L
2092~95 equal intervals of 28.
The signal point 83a i9 spaced 8 frnm both the I-a~is and the Q-a~is of the coordinate. It is ~ow assumed that n is a shift value of the 16 SRQAM. In 16 SRQAM, the si~nal point 5 83a nf 16 QAM i9 shifted to a signal point 83 where the distance from each axis is n8. The shift value n is thus ~pre~sed as:
O<nC3, The other signal points 84a and 86a are also shifted to two points 84 and 86 respectively.
If the error rate of the first data stream i6 Pe1, it is obtained from:
Pel-l6= 4 ~ eJfC ( ~ )+erfc (,~ ) = 8 er~c ~;~,~ ) Also, the error rate Pe2 of the second data stre~m is obtained from:

Pe216~ 2 erfc ( ~

= 4 c~c (2 ~ ~ ) The error rate of 36 or 32 S~Q~ will be calculated.
Fig. 100 is a vector diagram of a 36 SRQAM signal in which the distance between any two 36 QAM signal points is 28.
The signal poin~ 83a of 36 Q~ is spaced 8 from each a~is of the coordinate. It is now ~ssumed that n is a shift vaiue og the 16 SRQhM. In 36 SRQ~M, the signal point 83a is ~hift~d to a signal point 83 where the distance from each ~4 r~ ir ~ 5 ,~5~ ?. ,~v~30~

a~is is n~. Similarly, the nine 36 QAM signal points in the first quadr~nt are shifted to points 83. 84, 85t 86, 97, ~a, 8~, 100, lOl respectively. If a signal point group 90 comprising the nine signal points is regarded as a single signal point~ the error rate Pe~ in reproduction Df only the first data stream Di with a modified 4 PSX recei~er and the errcr rate Pe2 in reprod~ction of the second data stream D2 after discs~iminAting the nine signal points of tne group 90 from each uther, are obtained respectively from:
Pel-;2~ 1 ofc ( n~

c ( ~ ~n ~2n~
5-n Pe~-32- 3 erfc ( 4 ~ p = ~ erfc ~ f n~+~n~S
~ig. 101 8hows the relation between errar rate Pe and C/N rate in transmission in whLch the curve 900 represents a conventional or not ~odified 32 QAM .signal. The straight line 905 represents a sign~l having 101-5 o~ the error rate. The curve 901a represents a Dl level 32 SR~AM signal of the present invention at the shifL rate n of 1.5. As shown, the CJN rate of the 32 SRQAM slgnal ls 5 ~B luwer at the error rate of lOl5 than that of the conventional 32 Q~. This mean6 that the present invention allows a Dl signal to bu 2~ reprod~ced at a given error rate when its CfN rate is relatively low.
The curve ~OZa represents a D2 level SRQAYl signal a~

3S ~¢ 3,~2 5r~ ' 73~F ~ r.~k 13~t~ ,; 34~ ?. l 7 i 30~
209~495 ~=l.5 which can b0 reproduced at ths error rate of lO-l5 only when it~ C/N rate is 2.~ dB higher than that of the ~ co~veDtional 32 Q~Y of the curve 900. Also, thc curves 901b ~nd 902b represent Dl and D2 SRQAM si~llals at n=2.0 S respectively. The curves 902c represent~ a D2 SRQAM sign~l at n=2.5. It is apparent that the C/N rate of the SRQAM signal at the error rate of lO1-5 is 5d~, 8dB, ~nd lOdB higher at n=1.5, 2.0, and 2.5 re~pectively in the D1 levol and 2.5 dB
lower in the D2 level than th~t ~f a com~on 32 QAM si~n~l.
Shown ln Fig. 103 is thc C~N r~te o~ the first and sec~nd data streams Dl, D2 of a 32 SRQAM sig~al which is n~eded for maintai~ing a constant error rate against variatio~ of the shift n. As apparent, when the shift n i9 ~ore than 0.8, there is developed a clesr difference between two C/N rates of their respective D1 and D2 levels so that the multi-level signal, na~ely first and second data, transmission can be im~lemented 3uccessfully. In brief, n>0.85 is essential for ~ulti-level dats trA~smi6sion of the 32 SRQAM sign~l of the pre B ent invention.
Fig. 102 sho~s the relation b~tw~en the C~N rate a~d the error rate ~or 16 SRQAM signals. The curve 900 repre6enis a commo~ 16 QAM signal. The curves 901a, 90lb, 90lc and ~1 level or first data strea~ 16 SRQAM signals at ~-1.2, 1.5, and 1.8 re~pectively. The curves ~02a, 902b, 902c are D2 25 le~el or second d~ta stre~m 16 S~Q~M ~i~nals ~t n=1.2, 1.~, and 1.8 respectively.
The C/N rate of the first a~ld second data streams D1) D2 3~) 3 _ ~ ~51~ ~~~ 3 4 ~ ' r ~ ~ 0 ~
- 209249~

oX a ~6 SRQ~M 6igr~al is shown in Fig. 104, which i5 needed for maintaiuing a constant e~ror rate against variation of the fihlft r.. As apparent, wheD the shift ~ is ~ore than 0.9 (n>O.9), the multi-level data transmission of the 16 SRQAM
signal will be ~ecuted.
One e~a~ple of ~ropagation of SRQAM signals of the present irlven~ior. will ~ow bZ described for use with a digital TV ~errestrial broadcast service. Fig. 105 fihows the relation between the signal level a~d the distan~e between a tr~ns~itter artenn~ and Q receiver antenna in the terrestrial broad cast service. The curve 911 represenSs a tr~n9~itted signal fro~ the transmitter antenna o~ 1250 feet high. It is assumed that ~he error rate essential for reproduction of an ~pplicable digital TV signal i9 10 1-5. The hatchin~ area 912 represents a noise interruption. The point 9lO representc a signal recsption limit of a conventional 32 QAM signal at C~N=l5 dB where the distance L is 60 miles and a digital HDTV
8ig~1 can be intercepted at mini~um.
The C~N rate varies 5 dB under ~ worse receiving ~ondition such a9 bad weather. lf a chanKe in the r~levant conditlon, e.g. weather. attenuatas the CfN r~te, the interception of an HDTV signal will hardly be ensured. Al60, geotraphi.~cl conditions largely aff~ct the propagation of signals and a decrease of about 10 dB at least will be u~avoida~le. Hence, successful signal interception hithin 60 ~iles will never be guaranteed and above all, a digital signal will be propagated harder ~han an analogue signal. It , jC,J~ ~q2~b :7~5 ~ ~-'U ~ t~ 2092495 ~; !34~ .- ?~ ~0~

would be understood that the service area of a conventional digital TV broadcast service is less dependable.
In case of the ~2 SRQAM si~nal of the prs6ent invention.
thr~e-level sign~l transmission syctem is constituted as S shown in Figs. i33 and ~37. This permit~ a low resolution NTSC ~ignal of MPEG level to be csrried on the 1-1 data stream Dl1, a medium resolution TV data of e.g. NTSC syste~
to be carried on the 1-2 d~ta stresm Dl_2, and n hlgh frequency component o~ HDTV dsta to be c~rried on the second dsta stream D2. Accordingly, the service are~ of the 1-2 dats stream of the SRQAM signal is increased to a 70 mile point ~lDa while o~ the second data stream remains within a 5~ mile poin* 910b, as shown in Flg. 10~. Fig. 10~ i}lustrates a co~pu~er simulation result of the ~ervice srea o~ the 32 SRQAM signal of the present invention, which is ~imilar to Fig. 5~ but e~plains in more detail. As shown, the regions 708, 703c, 703a, 703b, 712 represent a conventional 32 QAM
recoivable area, a 1-1 data level ~l-l receivable area, a 1-2 data level D1_a receivable area, ~ second data level D2 recei~sble area, and ~ service area of a neighbor analo~ue TV
station recpQctively. The conventional 32 QAM signal data used in this drawin~ is bssed on a ~onventionally diselosed oIle .
For common 32 QAM signal, the 60-mile-radius service area caD be est~blished theoretically. The sign~1 level will howevir be attemlat~d by geographical OI' weather conditionc aIld particularly, considerably declined at near the limit of l9S~¢ 3,~ ,]~4~ -, 31i .' ~
; 2~92~L35 the service area.
If the low frequency band TV component of MPEGl grade is carried on the 1-1 level Dl_l d~ta and the med.um frequency band TV component of NTSC grade on the 1-2 level Dlz dsta an~
high frequency band TV component of EIDTV OII the second level D2 dat~, the ~ervice area of the 32 SRaAM signal of the present i.nvention i8 increased by 10 ~il~ in radiu~9 for reception of an EDTV signal of mediu~ resoll2tion grade and 18 mile~ for reception of an LDTV signal of low resolution ~rade alth¢ug~ decre~sed by 5 miles for rec~ption of an ~DTV signal of high resolutlon grade, as shown in F1g. 106. Fig. 107 6hows a service ar~a i~ case of a shift f-sActor n or B = 1.8.
Fig. 135 ~hows the service area of Fi~, 107 in terms of area.
More particularly, the medium resolutlon co~lponent of a digit~l TV broadc~st signal of the S~AM mode of the preset invention can successfully be intcrcepted in ar. unfavorable service region or shadow area where a convsntional mediu~
frequ~ncy band T~ signal is hardly propagated and attenuated due to obstacles. Wlthin at lsast the predetermined eervice area, the NTSC TV signal of the SR~M mcdP can be intdrcepted by any traditional TV receiver. As the shado~ or signal attenuati.ng area developed by building structures and other obstacies or by interference of a neighb~r analoguc TV signal or produced in a low land i~ ds~creased to ~ ~ini~us~, TV
2S viewers or sub~cribers will be increased ln nu~ber.
Also9 thc HDT~ service can be appreciated by only ~ few viewers who s~f~ord to h~ve a set of high cos~ HDTV reeeiver 7~

~ t ~2~ 52~ ;T~ ~i r ~ ~ J ~ ~ v . / v O v 2092~

and display, according to the conventional syste~. The syste~
of the present lnvention A.l10~6 a traditional N~SC, PAL, or ~ECAM receiver to intercept a medium resolution component of ~he ~igital HD~V signal with the use of sn addition~l digital tuner. ~ majority of ~rv viewers can hence enjoy the ~ervice at less cost and will be lnc~eased in number. Th;s will encourage the TV broadcast busin~s~ and create an extra social benefit.
Furthermore, the signal receivable are~ for medium re~olution or NTSC TV service according to the present invention i~ increased about 36X at n=2.5, as compared ~ith the conventional 6ystem, As the service srea thus the number of TV vlewers i~ increased, the TV broadcast bu6iness enjoys an i~creasing profit. This reduce6 a risk i~ the development of a new digital TV business which will thu~ be encouraged to put into practice.
Fig. 107 shows the service area of a 32 SRQAM signal of the present invention in which the sa~e effect will be ensured at n=1.8. Two service areas 703a, 703b of Dl ~nd D2 signals respectively can be det~rmined in extension for optim~m signal propag~tion by varying the shift n co~sidering a profile of ~DTV arLd NTSC receiver distribution or geographic~l features. Accordingly, TV viewers will sQtisfy ~he service and a supplier st~tion will enjoy a maximum of viewe.rs.
Th~is ~dvantage is given when:
n>l.0 ~0 . 9 . ~ 2 ~ ? ~ ?~ . 3 . . L / 3 [1, 2~92~9~

~ence, if the 3~ SRGA~I signal is selected, the shlft n is determined hy:
l~n<5 Also, if the 16 SRQ~M signal is employed, n is determined by:
1<n<3 In the S~QAM ~ode signal terlestrial broadcast service in which the first and second data levels are created by shiftin~ corresponding signal points as showr. in Figs. 99 alld 100, the advantage of the present invention ~ill be given when the shift n in a 16, 32, or 64 SRQAM signal is more than 1 .0 .
In the above e~bodiments, the low and high frequency band co~ponents of a video ~ignal are trans~itted ~s the first und ~econd data ~tre~ms. However, the transmitted cignal may bu an audio signal. In this case, low frequency or low resolution components of an audio signal IDay be transmitted as the ~irst d.&ta stream, and high frcquency or high resolution components of the &udio slgnal may be transmitted as the second data stre~. Accordingly, it is possible to receive high C/N portion in high sourld quality, and low C~N portion in lo~ sound quality. Thi~ can be utilL~ed in PCM broadcas~, radi~, portable telephone and the like. In this case, the broadcasting area or communicatio~
distance can be expanded &S co~lpared with ~he conv~rtional systems.
Furthermore, the third e~bodiment can incorporate a time division multiplexing ~M) sys~.eDI as 6hown in ~i~. 133.

i~ ¢ ~2~3 ~~ 3~ t~ 4~
- 2092~95 I~tilizaticn of the TDM ma~es it possible to inCreQse the number of subchannels. An ECC encoder 743a and ar. ECC encoder 743b, provided in two su~channels, differentiate ECC code ~ains so as to make a difference between thresholds of these two 6ubchanrels. Whereby, an increa~e of channel number of the ~ultl-level 6lgnal transmission can be realized. In thi case, it i6 also possible to provide two ~rellis encoders 743a, 743b as shown in Fig. 137 and differentiate their code gains. ~he e~planation of this block diagram i8 substantially identical to thnt of later described block diagr~m of Fi~, 131 which shows the sixth embodiment of the present invention and, therefore, will not described here.
In a simulation of ~ig. 106, ther~ is provided 5 dB
difference of a coding gain between 1-1 subchannel Dll and 1-2 subchannel Dl2.
An SRQAM is the system applying a C-CDM (Constellation-Cod~ Division Multiplex) of the present invention to a rectangle-QAM~ A C-C~M, which is a multiplexing method independent of TDM or FDM, carl obt~in sub~hannels by dividing a constellation-code corresponding a code. An incre~se of the num~er of codes will bring a~l expansion of transmission capacity, which is not attai~ed by TDM or FD~ alone, while maint~ining almost perfect compatibility with conventional ~ommunication apparatus. Thus C-CDM can br.i.ng e~cellent effects.
A]though above embodi~ent co~bines the C--CDM and the TDM, it is also possible to com~ina the C~CDM with the FDM

i ~ ~ 3 ' 1 ~ T~ 3 ? ~ '', ' ', IJ ~
2092~95 (Frequer~cy Division Multiplex~ to obtain ~imil~r ~odulation effect of threshold values. Such a syste~ can be used for a TV broadcasting, and Fig. lOB shows a frequencY distribution of a TV ~ignal. A spectrum 7Z5 r~presents ~ freq~ency distrib~tion of a conventional analogue, e.g. NTSC.
broadca6ting sLgnal. The large~t signal is a video carrier 722. A color c~rrier 723 and a sourd carrier 724 are n~t so large. There i9 ~nown a method of using an FDM for dividlng a dlgital broadcasting signal into two frequencies. In this ca~e, a carrier is ~ivided intD a first carrier 726 and a second carrier 727 to tr~n6mit a fir~t 720 and a second signal 721 respectivPly. An interIerence can be lowered by placing first and 6econd carriers 72~, 7Z7 sufficiently ~ar from the video carrier 7Z2. The first sigrlal 720 serves to l~ tra~smit a low recolutio~ ~V signal at a large outyut level, while the second ~ign~l 721 serves to trans~it a high resolution T~' sig~al at a ~all output level. ConsequentlY, the multi-level signal tran6mission making use of an FDM can be realized without being bothered by obstruction.
Fig. 134 shows an exs~ple of a conventional method using a 32 QAM system. As the subchannel A has a larger o~tput than the subchan~el ~, u threshold value for the subchannel A, i.e. a threshold l, can bc set small 4~5 dB than a threshold value for the subchan~el B, i.e. ~ ~hr~sh~d 2.
Accordillgly, a two-level broadcafiting having 4~~ d~ threshold difference can be reali~ed. In this case, however, a lurge reduction of slgrlal reception amount will occur i~ the ?~e i~5~* ~ ~t~ N~. :3~ ?. 3,/3(~
2~249~

.
rece vin~ signal levol decrea~es be~ow the threshold 2.
Because the second signal 721a, having ~ large information amount as shaded in ~he drawing, cannot be received in such a case a~ld only the first signal 720q, having ~ small informatiorl amoun~, lS received. Collsequent~y, a picture quality brou~ht by the second level will be extremely ~orse.
Howf3~er, the preseDt invention resolvec thi~ problem.
According to the prssent invention, tk.e first slgnal 720 is given by 32 SRQ~M mode which is obtained through C-CDM
modulQtion so that the subchannel A is divided into two subchannels 1 of A and 2 of A. The newly added subchannel 1 of A, havlng a lowest threshold value, carries a low resolution component. The second signal 721 is also given by 32 SRQAM ~ode, cnd a threshold value for the subcha~nel 1 of B is equslized with the thre~hold 2.
With this arrangement, the region in which a transmitted signal i9 not recelved when the signAl le~el decrea~es below the threshold 2 is reduced to a shaded portion of the second sign~l 721a in ~lg. 108. AB the subcha~lel 1 of B and the subchanrel A are both receivQble, the transmission a~ount i8 not 80 much re~uced in total. Acrordingly, ~ better picture quality i9 reproduced oveu in the second level Ht the ~ignal lev~l of the threahold 2.
By transmitting Q norm~l resolut'on component in one subchan~el, it becomes possible to increase the number of multiple level and e~pand a low resolution s~rvice area.
This lcw-threshold subchannel is utili~ed for ~ransmittin~

~ ~ 3~ y i ~3~55~t ~$~ ?. v~ O~
~9249~
:
important information such as sound in~ormation, sync infor~ation, header~ of re~pective data, because these information carried o~l this low-threshold subchannel can be surely received. ~hus stable reception is feasible. If a subchannel is newly ~dded n the second signal 721 in the same manner, the level nu~ber of multi-level transmission can be increased in the service ar0a. In the case where an HD'FV
signal has 1050 scanning lines, an new servlce area eguivale~t to 775 lines c~n be provided in addition to 52$
lines.
hccordingly, the combination of the F~M and the C-CDM
realizes an increase of service area. Although above embodiment divides a subchannel into two, it is needless to say it will al80 b~ preferable to divide it into three or more.
Ne~t, a method of avoiding obstruction by combining the TDM and the C~CD~ will be ex~lained. As shown in Fig. 109, an analogue TV signal ineludes a horizontal retrace line portion 732 and a video signal porticn 731. This method utilizes a low slgnal level o~ the h.ori~ontal retrace line portion 732 and non-display of obstruction on a picture plane during this period. By synchronizing a digital TV signal with an analogue TV signal, hori~ontal rctrace line sync slots 733, 733a of the hori~ont~l retrace line portion 732 can be used for trans~ission of an important, e.g. a sync, ~ignal or rumerous data at a high output iev~l. Thus, it becomes possible to increa~e data amount or output level without ~5 .3~ 5.~ t~ ~; 5, ~

2~9249~

increasing obstruction. The similar effect will be exp~cted even if vertical retrace line sync slots 737, 737~ are pr~vided synchronously with vertical retrace line portions 735, 735a.
FiB. llO shows a pri~lciple of the C-CDM. Furthermore, Fi~. 111 shows a code as6ign~ent of thc C-CDM ~quivalent to an e~panded 16 QAM. Fig. 112 shows a code assi~nment Df the C-CDM equivalent to an expanded 36 ~AM. As shown in Figs.
110 and 111, a 256 Q~M signal is divided into four, 740a, 740b, 740c, 740d, levels which have 4, 16, 64, 256 segments, respectively. A signal code word 742d of 256 QAM on the fourth level 740d is "11111111" of 8 bit. This is split into four code words 741BJ 741b, 741c, and 741d of 2-bit ---- i.e.
"11", "11", "11", "11", ~hich are then allocated on signal point regions 74~a, 742b, 742c, 742d of first, second, third, fourth levels 740a, 740b, 740c, 74~d, respectively. As a result, subchannels 1, 2, 3, 4 of 2 bit are created. This i6 termed ~s C-CDM (Constellation-Code Divislon Multiplex). Fig.
111 6hows A detailed code assignment of the C-CDM equiv~lent to e~panded 16 ~ , and Fig. 112 shows a det~iled code assignment of the C-CDM equivalent to e~pande~ 36 QAM. As the C-CDM is an independent multiple~ing system, lt can be combined wlth the convention~l FDM (Frequency Division Multiplex) or TDM (Time Division Multiple~) to further increa6e the number of subcha~nels. In this manner, the C-CDM system realizes a novcl multiplexing system. Although the C-CDM i5 e~piained ~y usine a rectangle 6~M, other ~3~13r ~ J~ '* ~ @~ . !'4~
'' 2~924g~

modulation system having signal points, e.g. QAM, PSK, ASE, and eVQn FSK if frequency region6 are regarded ag ~ignal points, c~n be al~o used for this multiple~ing in the same manner.
E~hodi~ent 4 A fourth embodiment of the ~resent invention will be described referring to the relevant drawings.
Fig. 37 illustrates the entire arrangement of a signal tr~nsmission syste~ of the fourth embodiment, whieh i8 10 urranged for terrestrial service and similar in both construction and ~ctior. tu that of the third embodiment shown in Fig. 29. The difference is that the transmitter antenna 6 is repl~ced with a terrestrial antenna 6a and the receiver antennas 22, 23, 24 ars replaced with also three terres-trial antennas 22a, 23a, 24a. The ~tion of the system i6 identical to that of the third embodiment and will no more be explained. The terrestrial broadcast service unlike a satellite service depends much on the distance between the tranomitter antenna 6a to the receiver antennas 22~, 3Z~, 42a. If a receiver i9 located far from the transmitter, the level of a received si~nal is low. Particularly, a c~m~lon multi-level QAM ~ignal c~n h~rdly be demodulated by the receiver which thus reproduces no TV progr~m.
The signal tran~mission system of the present inve~ltion allows the first receiver 23 equipped with the anten~a 22a, which is located a~ a far distance as shown in Fi~. 37, to intercept ~ ~odified 16 or 64 QAM s-gnal ~nd demodulaie at 4 v~3~ 3~2,3 . ~ L~ t~ ~ 7~ 5 i v ~ ~ . ~ i / ~ O ~
2109%49~

PSK mDde the first data stream or Dl co~ponent of the received signal t~ an NT~C video signal so that a TV program picture of medium resolution can be displayed even if the level of the received signal is relatively low.
Also, ths ~econd receiver 33 ~ith the arltenna 32A is located ~t a medium dist~nce from the antenna 6a ~nd can thu6 intercept and demodulate both the first and second data stream6 or Dl aud D2 components of the ~odified 16 or 64 QAM
sign~l to an HDTV video signal which in turn produces an HDTV
pro~r~m picture.
The third receiver 43 with the antenr~a 42a is loc~ted at a near distance and can intercept and demodulate the first, second, and third data streams or Dl, D2, and D3 compo~ents of the modified 16 or 64 QAM signal to ~ supér ~DTV video sigral which in turn produces a super HD~V picture in qu~lity to a common movie picture.
The as6i8nment of frequencies i9 determined by the same man~er as of the time division ~ultiple~ing shown in Fi~.
34, 35, and 36. Like ~ig. 34, when the frequencies are assigned t first to si~th ch~nnel~, L1 of the D1 component carrie~ an NTSC data ~f the first char~nel, Ml of ths D2 component carries an HDTY differsnce data of the first channel, and H1 of the D3 comp~nent carrles ~ supeI HDTV
differencP data of the first cha~nel. Accordingly, NTSC, HDTV, and super XDTV data all c~n be carried on the same chsnnel. If D2 and D~ of the other cha~els ars utilized ~s show~ in Figs. 3~ and 36, more data of HDTV and ~uper ~DTV

ag~¢ 3~ S7~ c :~4~ ? r~O~?lJ~
209~9~

respectively can be transmitted for higher resolution display.
As understood, the syste~ allows three different but compatible digital TV xignals to be carried on a single channel or usirg D2 and D3 re~ions of other c~annels. Al60, the ~edium resolution TV- pict~re data of each ch~nnel can be intercepted in a wider service ~rea ~ccording to the present invention.
A variety of terrestrial digital TV broadcast systems employing a 16 aAM ~DTV signal of 6 MHz bandwidth ha-~e been proposed. Those are however not compatible with the existing NTSC ~ystem and thus, have to be associated with a simulcast technique for transmitting NTSC signals of the s~me program on another channel. Also, such a common 16 QAM signal limits a serYice area. The terrs~trial service system of the present invention allows ~ receiver located at a relatively far dist~nce to intercept successfully a medium resolution TV
signal with no use of an additiu~al device nor ~n e~tra channel.
Fig. 52. shows an int,erference region of t~e service area 702 of a conventiollal terrestrial digital HDTV ~roadcast station 701. As shown, the service are~ 702 of the conventional HDTV station 701 is intersec~ed with the service area 712 of a neighbor analogue TV station 711. At the in~ersecting region ~13, an HDTV si~nal i6 attenuated by slgnal interference from the analogue TV sta~ion 711 and will th~s be intercepted with less consistency.

~C~ ?~ ~ @;~'~0;~ 4 ~ r 2092~95 "

~ 'ig. 53 sh~ws an interference region associ~ted with the multi--le~el signal transmi6sion sy6tem of the present inYention. The syste~ i~ low in the energy utili~atior. as co~pared wi th e conveI~tional syste~ d it.A service area 703 for HDTV signal propagation is smaller than the area 702 of the cDnvention~l syste~l~ In contrary, the serYiCe ~re 704 for digital NTSC or medium resolution TV 3igna] propagation is lar~er than the ~onventi~nal area 702. The level o~ signal interference from a digital TV stAtion 701 of the sy~tem to 1~ a neighbor analogue TV station 711 i5 eq~ivalent to that from a conventionai digital TV st~tion, such as ~hown in Fig. 52.
In the ser~ice area of the digital TV station 701, -there are three inte~ference ~egions deveioped by signal interference from the analogue TV station 711. Both HDTV and NTSC signals can hardly be intercepted in the f irst region 105. Aithough fairly interfered, an NTSC signal may be intercepted at an e~ual level in th~ second region 706 denoted by the left down hatching. The NTSC signal is c~rried on the ~irst data strea~ which can be reproduced at a relatively low C/N rnte and will thus be ~irlimu~ ~ffected whe~ the C/N ra~e i~ declined by signal interference fro~ the analogue TV station 711.
A~ the third region 707 denoted by the ri~ht down hatchin~, an HDTV signal can ~lso be intercepted when si~ral interference is abseJ~t while the ~TSC signal c~n con~tantly be intercepte~ at a low level.
Accordingly, the overall signal receivable area of the . _ .. J ~ ~ , ? ~ }~ 3~ 30~
' 2092~9~

syate~ will be increased although the service area of HDTV
~ignals becomes a little bit smaller than that of the convention~l syste~. Also, at the signal a-ttenuating regions produced by interference from a neighbor analo~ue T~ station, NTSC level signa]~ of an ~DTV program can successfully be intercepted as compcred with the conventional system where no HDTV program is viewed in the sa~e area. The syste~ of the pre~ent invention much reduces the size of signal attenuating area and whsn increases the energy of signal transmission at a transmitter or transponder stati.on, can e~tend the HDTV
sign~l service area to Bn equal size to the conventional syste~. Also, NTSC level signals of a TV program can be intercepted morc or less in a far distance arsa where no service is given by the conventional system or a signal interference area caused by an adja~ent analog~e TV station.
Although the e~bodiment em~lDys ~ two-level signal transmission method, a three-level method such aB shown in Fig. 78 will be used with equal succes~. If ~n HDTV signal i5 divided into three picture levels-HDTV, ~TC, and low resolution NTSC, the service nrea shown in Fig. 53 will be increased fro~ two levels to three levels where the signal propagation is extended radially and o~twardly. Also, low re~ol~tion NTSC signals can be received at an acceptable le~el at the first sig~al interference region 705 where NTSC
signals are har~ly be iutercepted in ths two-level system. As ~nderstood, the signal inter~erence is also involved fro~ a digital TV station to an analo~ue TV station.

1~9'~ 5~ ia~ ,,,34'~ 3i3','5 ~ 2as24s~
:' The description will now be continued, provided that no digital TV station should ~nuse a signal interfere~ce to any neighbor analogue TV station. Acc~rding to a novel ~yste~
under consideratlon in U.S.A., no-u6e channels of th,e existing service cha~nels are utilized for HDTV and thus, digital signals must not interfere with analogue signals.
~or the pur~ose, the transmitting level of a digital signal has to be decreased lower than that shown in Fig. 53. If tbe digital signal i~ of conventiona1 l~ Q~ or 4 PSK mode, its ~DTV 6ervice area 7~8 becomes decreased as the signal interference region 713 denoted by the cross hatching is ~airly large as shown in Fig. 54. This results in a less numbar of viewer~ and sponsors, whereby such a digital 6ystem wlll havs ~uch difficulty to operate for profitable business.
Fig. 55 ~hows a similar result according to the system of the present invention. As apparent, the HDTV signal receivQble 703 is a little bit smaller than the equal area 708 of the conventional system. However, the lower resolution or NTSC TV signal receivable area 704 will b~ increased a~
compared with the convertio~al syste~. The h~tching area represents Q region where the NTSC level signal o~ a program can be received while the ~DTV sig~al of the same is hardly intercepted. At the first interference re&ion 705, both HDTY
and NTSC signals cannot be interr~epted due to signal interference from an analogue station 711.
When the level of signals is Pqual, the mlllti-level transmission syst~m o~ the present invention provides a i9~J~ 53 . ~3~ '$~ ............................ 343 ~ ,OJ
2092~

smaller HDTV service area and a greater NT~C sPrvice area for inter.ception of an HD~V program at an NTSC signal level.
Accordingly, the over~ll service area of each station is incr~ased and more view~r~ can enjoy its TV broadcasting iervice. Further~ore, HDTV/~TSC c~mpatible TV business can be operated wlth economical advantages and consistency. It i6 also intended that the level of a transmitting sigrLal i6 lncreased when the cont~ol on averting signal intcrference to neighbor ~nalogue TV stations is lessened corresponding to a sharp increase in the number of ho~e-use digital receiver~.
Hence, the service area of ~DT~ signals will be i~creased and in this res~ect, the two different regions for interception of HDTV/NTSC and NTSC digltal TV signal levels resp~ctively, 6hown in Fi6. 55, can be adjusted in proportion by varying lS the 6ignal point distance in the fi.rst and/or ~econd data strea~. As the first data stream carries information about the signal point distance, a multi-level signal can be received with more certainty.
Fig. 56 illustrat~s signal interf~rence between two digital TV stations in which a neighbor TV station 701a also provides a digital TV broadcast service, as compared with an analogue ~tation in Fig. 52. Since the l~vel of a transmitting ~ignal becomes hign, the HDTV service or high resolution l~V signal receivable area 703 in increased to an extension equal to the service area 702 oi~ an a~alogue TV
system.
At the lntersecting r~giun 714 between two SeJYiCe area~

l39~ 2~ ; n, , ~, g Q ~, ~5/~0~
- 2~92~9~

of their rebpsrtive statio~6, th~ received signal can be reproduced not to an H~TV level picture with th~ use of a co~mon direction~l antenna dua to signal interference but to an ~TSC level picture with a particular directional antenra directed towards a desired TV station. If a highly directional antenna i6 used, the recei~ed signal from ~
target StQtiOn will be raproduced to an HDTV pict~re. The low resolutiun sign~l receivable area 704 is increa6ed l~rger than the a~alogue T~ system service area 702 and a couple of 10 intersecting regions 715, 716 developed by the two low resolution signal receivable areas 70~ and 704a of their respective d~gital TV stations 701 and 701a permlt the received signal from antenna directed one of t~.e two statio~s to be reproduced to an NTSC level pictllre.
The HDTV service area of the ~ulti-level signal transmission system of the present invention it~elf will be much increased wher. applicable signal restriction rules are withdrawn in a coming digital TV broadcast fiervice maturity time.
At the ti~e, the system of the present invention also provides as a wide HDTV signal recelvable area as of the conventional sy6tem and ~arti~ularly, ailows its tran~mitting signal to be reproduced at an NTSC level in a f~rther distance or i~tersecting areas wherc TV signals of the conventional system are hardly intercepted. Accordingly, signal ~ttenuating or shadow regions in the Rervice ar~a will be mini~ized.

~ 25E .7~ '. 3t'~
20~24~S

~ndi~nt 5 A first embodimert of the present invention resides in a~plitu~e modulation or ASE procedure. Fig. ~7 illustrates the assig~ment of signal points of a 4-level ASK signal S according to the fifth embodiment, in which four ~ignal poi~ts are denoted by 721, 722, 723, and 724. l'he four-level tran~isjion permits a 2-bit data to be transmitt~d in every cycle period. It is assumed that the four signal points 721, 722, 72S, 724 represent two-bit patterns 00, 01, 1~, 11 r-espectively.
For ease of four-level signal tran6mission of the embodiment, th~ two slg~al points 721, 722 are de~ignated a5 a fir~t ~ignal point group 725 ~nd the other two 723, 724 are defiignated as a second si~nal point group 72B. rhe distance 15 between the two Btgnal pDint groups 725 ~nd 726 ls then determined wider than that between any two adjacent signal pointR. More specifieally, the distance L~ between the two ~ignals 722 and 723 is arranged wider tha~ th~ distance L
between the two adJacent points 721 and 722 or 723 and 724.
This is expressed as:
Lo>~
Hence, the ~ulti-level sign~l IranSmiSsiOn s~tem of the embodiment is based on Lo~L. The embodiment is however not limited to Lo>L and L-Lo will be employed temporarily or permar.Pntly depending on the requirements o~ design, condi~ion, and ~et~ing.
The two signal point groups are assigned one-bit 9:, 209249~i patterns o~ the first data stream Dl, as shown in Fig. 59(a).
More particularly, a ~it O of binary system is ~ssigned to the first signal point ~roup 725 and another bit 1 to the second sign~l point group 72~. Then, a one-bit pattern of the second data stream D2 is assigned to each signal point. For example,the two signal points 721, 723 are asqigned D2=0 and the other two signAl points 722 and 724 are assigned D2=1.
Those are thus e~pressed by two bit~ per symbol.
The ~ulti-level sign~l trans~ission of tn~ present invention oan be i~plemented in an AS~ mode with the ~1se of the foregoing si~nal point assignmert. The system cf the present invention ~orks in the same m~nner as of a conventional equa} signal point distance technique when the signal to ~oise ratio or C~ rate i9 high If the C~N rate b~co~es low and no data can be reproduced by the conventio~al techni~ue, the present system ensures reproduction of the first data stream Dl but not the second data streAm D~. In ~ore detail, the ~tate at a low C/N is shown in Fig. 6~. ~he signal points transmitted are displaced by a Gaussian distribution to r~nges 721~, 722a, 723a, 724~ respectively at the receiver side due to noise and transmiq~ion distortion.
Therefore, the distinclion ~etween the two ~ignals 721 and 722 or 723 and 724 will hardly be e~ecuted. In other words, the error rate in the secor~d data stream D2 will be increased. As app~rent from Fig. 60, the two signal points 721, 722 are easily distin~uisbed fro~ the other two signal points 723, 724. The disti~ction between the two signal point ~6 3 ~ 2 r) 3 r~ i". ~ N ~ 4 ~ ? . ~ ~ ? ~1 ~
2~92495 groups 725 and 7Z6 can thus be carried ou~ with ease. As the ~sult, the fir~t ~ata stream Dl will be reproduced at a low error rate.
Accordingly, ~he two different levsl data Dl and D2 can be transmitted simultalleously. More particulnrly~ boSh the fir~t and r~econd data sLre~m6 Dl and D2 of a given signal trQnsmitted through the multi-l~vel trans~ission syste~ can be reproduced at the area where the C/~ rate i~ high and the first data stream Dl only can be r~produced in the area where ~he C/N rate is low.
Fig. 61 is a block diagram of a trans~itter 741 in which an input unit 742 comprises a first data stre~m input 743 and a second data stream input 744. A carrier wave from a carrier generator 64 is amplltude modu'ated by a multiplier 7g~ using an input signnl fed across a proce3sor 745 fro~ the input unit 743. The mo~uiated signal is ~hen band limited by a filter 747 to an AS~ signal of e.g. VSB ~ode which is then delivered from an output unit 74~.
The w~veform of the ASK ~ignal after filtering will now be e~amined. Fig. 62(a) shows a frequencY spectrum of the AS~
modulated signal in which two side~ands are provided on both sides o~ the carrier frequency bar,d. One of the ~wo sidebands is eliminated with the filter 474 to produce a si~nal 749 which conta~ns a carrier component a8 shown in Fig. 6Z(b).
~5 The sign~l 74~ is a VSB signal and if the modulation frequency band is f0, will be transmitted in a frequency band of about foJ2~ Henrel the f~equency utilization becomes high.

!5S3~ 3,~'~ a 3~ ~T~ 4~ ?. ~
2 ~ 5 : .
Using vs~ ~o~0 transmission, the ASK signal of two bit per sy~bol shown in Fig. 60 can thus carry ir, the frequency ba~d an umount of data equal to th~t of 16 QhM ~ode at four b1ts per sy~bol.
Fig. 63 i~ a block diAgram of a ~ecoiver 751 in which an input si~nal intcrcepted by a terrestrial antenn~ 32a is transferred through an input unit 752 to a mixer 753 where it i9 mixed with a sig~al fro~ q variable oscillator 754 controlled by channel eelection to a lower mediu~ frequency sig~al. The sigral fro~ the mixer 753 is then detected by a detector 75~ and filtered by an l,PF 756 to a baseband signal which is transferred to a discriminating/reproduction cir~ui~
757. ~he discrimination~reprod~ction circuit 757 reproduces two, first Dl and seco~d D2, da~a streams from the baseb~nd si~al and transmit them ~ul~her through a first 758 and second d~ta stream output 75~ respectively.
~ he transmission of a TV sigDal using such a transmitter and a receiver will be e~plained. Fi~. 64 is a block diagrsm of a video signal tr~l~s~itter 774 ir. which a high resolution TV 6ignal, e.g. an HDTV si~nal, is fed throu~h an input unit 403 to a divider circuit ~04 of a first video encoder 401 where it is divided i~to four highjlow Prequency TV signal co~ponents denoted by e.g. H VL, HLvH, H~V~I and HHVH. This action i~ identical to that of the third embodiment previously described reierring to Flg. 30 ~lld will no ~.ore be explained in detail. The four separate Tv signals are enooded respectively by a compressor 40S ~sing a known 9 ~r 3~2 J ~ I :J ~ C; ~ OT~ 34 lil/3~

- 2092~9~
DPCMDCT variable length code encoding technique whi-h is co~mo~ly used e.g. in MPEG. Meanwhile, the motion compensation of the si~nRl i6 carried out at the input unit 403. The ~ompre&sed signals are su~med by ~ summer 771 to two, first and oecond, data ~treams Dl, D2. The low frequency video ~ign~1 componznt or HLVL signal i9 co~tained in the ~irst data stre~m ~1 The two dats ~tream signals D1, D2 are then t~ansferred to A first 74~ ar.d a second data stream input 744 of a tr~n~itter unit 741 where they are amplit~d~
modulated and summed to an AS~ sign~l of e.~. VSB mode which is propagated from a terrestrial antenna for bro~dcast service.
Fig. 65 i~ a block diagram of ~ 'rv receiver for such ~
digit31 TV broadcast system. A digital TV signal intercepted by a terrestrial ante~n~ 32a is fed to an input 752 ol a receiver ?81. The OEignal is then transferred to a detection~demodulatlon circuit 760 where a desired channel signa] 16 selected and demodulated to two, first ~nd ~econd, data streR~s ~1~ D~ which are then fed to a first 758 and second data stream output 75~ re~pectively. The action in the receiver unit 751 ic similQr to that described previou~ly and will uo more be e~plained in detail. The two data ~tre~ms Dl, D2 are sent to a divider urit 77~ in which ~l is divided by a divider 777 into two components; ~ne or compressed HLVL
is transferred to a first input 521 of a second video decDder 42~ aIld the other is fed to a su~mer 778 where it is ~ummed with D2 prior to transfer to a ~econd input 5~1 of tho second 9~

.9~9~ 33'?9 ~ ............................................. 3~ J, ~

2~92~95 video decoder 422. Compres~ed HL~L is then sent fro~ the fir~t input 521 to a fir6t e~.pander 523 where it i~ e~panded to HIVL
of the original length which is the~ transferred to B vidao ~ixer 548 and an aspect ratio changing circuit 779. When the illpUt TV signal is an HDT~ signal, HLVL represents a wide-~cree~ NTSC ~ignal. WheD the same is un NTSC signal, HLVL
repre~ents a lower re~olution video signal, e.~. MPEGl, that An NTsC level.
Th0 input TV 6ignal of the embodiment i6 ~n HDTV signal and HLVL becomes B wide-screen NTSC 6ignal. If the aspect ratio of an svailable display is 16:9, HLVL is directly delivered throu~h an output unit a~ Q 16:9 vidao cutput 426.
If the display has an aspect ratio of 4:3, HlV~ is shifted by the aspect ratio changing circuit 779 to a letterbos or sidepanel for~at and then, delivered ~rom the output unit 780 as a corresponding format video output 4Z5.
The second data stream Dz fed from the second daka stream o~tput 759 to the sum~er 778 is su~med with the output o~ the divider 777 to a sum signal which is then fed to the 20 second input 531 of the second video decoder 422. The 8Um signal is furthe~ tran~ferred to a divider circuit 531 while it iB divided into three com~re~sed forms of H~, H~VL, and HHV~. The three compressed signals are then fecl to a second 535, a third 536, and a fourth expander 537 respect1vely for converting ~y exp~nsion to HLV~, HHVL, a~d HHVH of the original length. T~le three sign~ls are summed wi-th HLVL by the video mixer 548 to a co~posite ~DTV signal which i6 fed thro~gh an !9C3L ~ 5 ~ 4~ /3~

2~92~9~

o~tput 546 of the second video decoder to She output u~it ~80. ~inally~ the ~DTV ~ignal ls del~vered from the output urit 7BO a~ an HDT~ video signal 427.
The output unit 7~0 is arranged for detecting ar, error rate in the second data sSream of the second data stream out~ut 759 through an error rate detector 78a and if the error rate j.B high, delivering HLVL of low recolution video data system~tically.
Accordingly, the ~ulti-level signal transmi6sion sy6tem ~or digital TV signal transmission and reception becomes feasible. For e~ample, i~ a TV slgnal transmitter statlon i9 near, both the fir6t and second ~ata ~troa~s of a received signal can ~cces6fully ~e reprodllced to exhibit an HDTV
quality picture. If the trans~itter station is far, tha first data ~tream can be reproduced to H~VL which is c~nverted to a low resolution TV plcture. ~ence, ~ny T~ progra~ will be intercept~d in a wider area and displayed at a picture quality ranging ~rom HDTV to NTSC level.
Fig. 66 is a block diagram showing ~nother arrangeme~t of the TV receiver. As shown, the r~ceiver urit 751 contains on1y ~ first dsta stream OUtp~lt 768 and thu~, the processing of the ~econd d~ta stream or HDTV data is not ~,eeded ge that the over~ll construction can be ~inimized. It is a ~ood idea to hAve the first vidèo decoder 421 sho~n in Fig. ~1 as a Z5 video decoder of the receiver. Accordingly, an NTSC level picture will be reproducsd. The re~eiver is fabricated ~t much less cost as having no capabilitY to receive ~ny HDTV
lDl 1393~ ~2~ iy~ t~ ?. 11;3 3~
2~92~9~

level signal and will widely b8 accepted in the mar~et. In brief, the receiver can be used as an adapter tuner for intercepti~n of a di~ital TV signal with givin~ no modification to the existing T~' syste~ including a displ~y.
The TV recelver 781 may have a further arrangement ~own in Fig. 67, whi~h ~erves a6 both ~ satellite broadcast recei~er for d~modulation of P6~ signal~ and a terrestrial broadcast receiver for demodulation of ASK ~ig~ n action, a PSK ~ig~al received by a ~atellite ante~na 32 i~
mixed by d mi~er 786 with a sign~1 from an oscill~tor 787 to a low frequency s;gual which i6 then fed through an input unit 34 to a mi~er 753 similar to one shDwn in Fig. 63. The low frequency signal of PSK or QAM ~ode in a gi~en ch~nnel of the ~atellite TV system is transferred to a modulAtor 35 where two dnta streams Dl and D2 are reproduced from the signal. D1 Hnd ~2 ~re sent through a divider 78a to a second video decodar 422 where they are converted to ~ video signal which is then delivered fro~ ~n output unit 7~0. Also, a digitsl or analogue terrestrial TV signal intercepted by a terrestrial antenna 3Za i9 fed through an input unit 752 to the mi~er 753 where one desired channel i~ selected by the sa~e manner as deccribed in Fig. 63 and detected to ~ low frequency base band signal. The signal of ana;ogue for~ is sent directly to the demodulutor 35 for demodulatlon. The signal of digita~ ~orm is then ~ed to a di~crimination~reproducing circuit 7a7 ~here two data ~tre~ms D1 and D2 are reprodu~ed fro~ the sign~l. D1 and D2 are ~ 3¢ 3 ~ F~ 5 ~ ?,~ ,tt, ~ 3 ~ ~-,3~1~
2092~95 converted bY the fiecond ~ideo decvder 422 to a video ~ignal which i~ then delivored furth0r. A satellite analogue TV
signal is transferred to a video demodulator 7~B where it is AN modulated to an analogue ~ideo signal which is then delivcred from the output unit 7~0. A~ undorstood, the mi~er 753 of th~ TV receiver 781 shown in Fig. 67 is arranged compatible between two, satellite and terre3trial, brosdcast service6. Al~o, a receiver circuit including a detector 765 and an LPF 766 for AM modulation of an analogue signal can be utilized oompatible with 8 di~ital ASE signal of the terrestrial TV service. The ~a~or part of the arrangement shown in Fig. 67 is arranged for compatible uRs, thus minimizing Q circuitry construction.
According to the e~odlment, a 4-level AS~ slgnal is divided into two, Dl and D2, level co~ponent~ for e~ecution of the o~e-bit mode multi-level signal tran~mission. I~ an ~-level AS~ signal i8 uAed as shown in Fig~ 68, lt can be trQnsmltted in a one-bit mode thres-l~vel, Dl, D2, and D3, arran~ement. A shown in ~ 68, Dl is assign~d to eight 20 sign~l points 721a, 721b, 7Z2a, 722b, 723Q, 723b, 724a, 724b, each palr representing a two-bit pattern, D2 is assigned to four small sign~l point groups 721, 722, 723, 724, sach two groups representing ~ two-bit pattern, and ~3 is assigned to two large sig~l point group6 725 and 726 represonting a two-Z5 bit p~ttern. More particularly, this is equiv~lent to a ~o~m in whic~ each of the four si~n~l points 721, 722, 723, 72~
shown in Fig. 57 is divided into two co~ponents thus i 3 ~ . ~ ~ 2 5 ~ i ~ ~ 0 4 h ~ . 1 3~ ? I~J J~ r producing three differ~nt level data.
The three-level si~,~al tr~nsmission 1~ identical to that described in the third embDdiment and wi 11 no furtheI be explained in detail.
In p~rticular, the arran~ement of the video encoder 401 of the third embodiment shown in Fi~. 30 is replaced with Q
modification of which block diagram i~ Fig. 69. The operation of the modified arrangement i9 similar and will no longer be e~plained in dstail. Two video 9ignal divider circuits 404 and 404a which may be sub-bar.d filters are provided forming a divid~r unit 794. The divider unit 794 may also be arranged more simple a shown in the bloc~ diagram of Fig. 70, in which a signal passes across one signal di~ider clrcuit two times at time di~ision mode. More specifically, a video signal of e.g. HDTV or super HDTV from the in~ut unit 403 is time-base compre~ed by a time-base compressor 795 and fed to the divider circuit 404 where it is divided into four components, H~8-H, H~IVL-H, and HLV~-II, and HLVL-H at ~ first cycle. At the time, four switches 765, 765a, 76~b, 765c remain turned to the position 1 eo that H~V~-~, H~VL-H, and HLV~-H are transmitted to a compressin~ circuit 405. Meanwhile, ~LVL-H
is fed back through the terminal 1 of the switch 765c to the time-base compressor 795. At a ~econd cycle, the four switches 765, 765a, 765b, 76~c turned to the poBition 2 and all the four components of the di~ider circuit 404 are si~ul~aneously transferred to the compre~6ing circuit 405.
Accordingly, the divider unit 796 of Fig. 70 arranged for l ~ S ~ r 3 11 2 ~ r~ N j 1 3 ~ ~ ? I 1 ~/ 3 C r~
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time division processing of aIl input signal can be con6tructed in a simpler dividing circuit form.
At the receiver ~ide, such a video decoder as described in the third embodime~t and shown in ~ig. 30 is needed for thrse-level transmiseion of A video sixnal. More particularly. a third video decoder 423 i~ provided which contains two mi~ers 556 and 556a of different processing capability Qg shown in the block diagram of Fig. 71.
Also, the third video decoder 423 may be modified in ~0 which tbe same action is e~ecuted with one sing1e mi~er 556 as showr in Fig. 72. At the first timin~, five switches 765, 765a, 765b, 765c, 765d remains turne~ to the position 1.
~ence, H~VL, HLV~, HHV" and H~V~ are fed from a first 52~, a second S22a, a third 522b and a fourth expander 522c to through their respective switches to the ~ixer 55B where they are mixed to a cingle video signal. The video slgnal which represents HLVL-H of an input high resolution video si~nal i8 then ied back throu~h the terminal 1 of the switch 765d to the ter~inal 2 of the switch 765c. At the second timing, the ~our swltche~ 765, 765a, 765b, 765c are turned to the point 2. Thus, H~V~-~, H~L-H, HLV~-H, and }ILVL-H are transferred t~
the mi~er 556 where they are mixed to n single ~ideo signal w~ich is then sent across the ter~inal 2 of the ~witeh 765d to the output unit 554 for further d~livery.
In this m~nner of time division proc~ssing of a three-level signal, two mlxers can be replaced with one mixer.
More particularly, four c~mponents HLVL, HLVU, H~VL, }lHVN

~ J .3~C ~ D ~ r~ t 20924~

are fed to produce HLVL~H at the fir~L timing. Then, HLV~-H, HDVL-H, and HRV~-H are fed at the second timing delayed from th first timing a~d ~ixed with H~L-H to a target video ~ign~l. It is thus essential to perform the two actions at an iaterval ~f ti~e.
If the fo~r componentc are overlapped ~ach other or supplied in a variable sequenco, they have to be time-bn6e adj~sted to a given sequence through u~ing ~e~ories accompanied with their re~pective switches 765, 76~a, 7~5b, 765c. In the foregoing manner, a signal iB tra~s~i~ted ~ro~
the transmltter at two different timing periods as shown ln Fig. 73 ~o that no time-base controlling circuit i~ needed in the r~ceiver which is thu~ ~rrauged more compact.
As shown in Fig. 73, Dl iB the Iirst data stream of a tr~nsmitting signal snd HLVL, HLV~, H~L, cnd H~V9 are tra~smitted on D1 char~cl at the period o~ ~irst timing.
Then, at the period of second timing, HLV~, H~VL, and H~V~ are transmitted on D2 channel. A~ the signal i~ trar~smitted in a time division seguence, the encoder in th~ receiver can be Z0 arranged more ~i~ple.
The technique of reduci~g the number of the e~panders in ~ the decoder will now be explained. Fig. 74(b) Phows a time-base sssigDment of ~o~r d~ta cDmponents 810, 81Ca, 810b, 810c of a signal. ~'hen other four data co~pQn~nts 811, 811a, 811b, 811c are inserted between the four data components 81l, 811a, Bl1b, Bllc respectively, the latter c~n be tran~mitted at intervals of time. In action~ the second video decoder 422 ' ~ 3 ~ . 3~ f~ ~ ~ . .J~3 . .C~

-~hown in Fig. 74(a~ receives the four components of the first data stream Dl at a ~irst input 521 and transfers them throug~ a switch 812 to 8n e~ander 503 one after another.
More particulsrly, the component 810 fir~t fed is e~panded during the feedlng o~ the ~omponent 811 a~d after completion of proc~sing ~he component 810, the succeeding component 810e. i~ fed. Hence, the e~pander 503 can proce6s a row nf the component6 at time interval~ by the same time division m~nner as o~ the ~ixer, thus substituting the simultaneous action of a number of oxpanders.
Fig. 75 is a time-base asoigr~ent of data components of an HDTll signal, in which HLV~(l) of an NTSC component o~ the first channel si~nal for a TV progra~ i6 ~l~ocated to a d~ta domain B21 of Dl signal. Al~o, HL~, H~VL, ~nd H~V~ carrylng ~DTV additional c~ ~on~nts o~ the first channel signal are alloc~ted to three domain6 821a, 821b, 821c of ~2 sig~al respectively. There are provided other data components 822, 822a, B22b, BZ2c betw~en the data components of the fir~t channel signal which can ~hu~ be e~panded with an e~pander circult d~rlng tr~lsmissiDn o~ the other data. ~ence, all the data components of one chaDnel signal will be proces~ed by a single expander capa~le of operating at a highar speed.
Similar effects will be ensured by assi~nment cf th~
~ata components to othe~ domains 821, B21a, 821b, 821c as shown in Fig~ 76. This b~come6 more effectiva in transmisslon and reception of a com~on 4 PS~ or ASK 6ignal havin~ no different digital level~.

;5 3:3~ C6'~ 3 ~ v9 ~
20~2~9~

Fig. 77 6hows a time-base ~signment of data comp~nents during physical two-level tran6mission of thre~ different sig~al level data: e.g. NTSC, HDT~ and ~uper HDTV or low resolution NTSC, ~tandard resolution NTSC, and HDTV. For e~mple, for transmiss~on of three data co~ponent~ of low resol~tion NTSC, st~ndard NTSC, and HDTV, the low resolution NTSC or ~IVL is aliocated to the data domain 8~1 of Dl slgnal.
Al~o, H~u, H~VI, and ~V~ of the standard NTSC cc ,on~nt ~re allocated to three do~uins 821a, 821b, B21c respectively.
HlV~ NVL-H, and H~V~-H o~ the HDTV component are allocatcd to domainfi 823, 823a, and 823b respectively.
The foregoing assignment i9 associated with such a logic ievel arrange~ent bssed on discrimination in the error correction capability as descril3ed in the second embodiment.
More particulnrly, HiVL is carried on Dll channel of the Dl signal. The Dll chanrel iB higher in the error correctlon capability than Dla channel, as describod ir. the second embodiment. The Dl_l channel is higher in the redundancy but lower in the error rate than the ~1-2 chaImel and the date 821 can be recon~tructed at a lower CJN rate tharl that oi the other d~ta 821a, 821b, ~21c. ~ore specifi~ally, a low resolution NTSC comporle~t will be reproduced at a far loc~tion from the transmitter antenna or in a signal attenu~ting or sh~dow area, e.g. the interior of a vehicle.
In view oi the error rate, the d~ta 821 of Dll chanrAel is less sffected by signal interfer~nce than the oth~r data 821~, 821~, h21~ ~f D1~2 channel. while bein~ specifically ~~ 3~ H , 3~ 4; . ~
2~92~9~

di~criminated and stayed in a different logic level, as described in the second e~bodiment. While Dl ard D2 are dlvided into two physlcall~ dif~erent levels, the levels det~rm5ned by discri~ination of the distan~e between error correcting cod~ are arrRnged differ~nt in the logic level.
The demodulation uf D2 data requlre~ a higher C/N rate than th~-t for Dl data. In actio~, HLVL or low resa1ution NTSC
~igns1 can at least be reproduced in a diLtant or 10wer C/N
service area. HL~ VI, and H~V~ can in addition be lD reproduced at a lower C/N area. Then, at a high CJN area, HIV~-~, H~VL-H, and ~RV~-~ co~pone~ts can al~o be reproduced to develop an HDTV signal. Accordingly, three dif~erent level broadcast signals can be played back. This method allows the ~igna1 receivable area shown in Fig. 53 to increase from a double regi~n to B triple region, as shown in Fig. 90, thus en~uring hiBher opportunity for enjoying TV progra~s Fig~. 78 ic a block diagra~ of the third video de~oder arr&nged for the time-base a~siLn~ent of data shown 1n Fig.
77, which is 6imilar to that shown in Fig. 7Z except that the ZO third input 5~1 for D3 signal is el~minated and the arrangement shown in Fig. 74(a) is added.
In operatio~, both the Dl and D2 signals ~re f~d through two i~put u~its 521, 530 respectively to a switch ~l2 at the first 'iming. A~ thelr cump~nents including HLVL ar~ tim~
25 di~id~d, they ~re transferred in a s~quence by tha swi~ch 812 to an expander ~03. This sequence will now be e~pl~ined referring to the time~base assigrlment o~ Fig. 77. A

' ~ 'i 3 - ~ ,q ' 5 b ; ~ 8 2~92~

compres~ed form o~ ~LVL of the first cha~nel is first fed to the expander 503 wherc it i~ e~pa~ded. Then, HLV~, H~VL, and H~V~ are e~panded. All tha four e~panded components a~e ~eDt through a switch B12a to a mi~er 556 where they are mi~ed to produce HLVL-H. HLVL-H i8 t~en fed back from the terminal 1 of d switch 7~5a through tha input 2 of a switch 765 to the H~VL
input of the mixer 556.
At the secor~d timing, HLV~-~, H~VI-H, and ~V~-H of the D2 signal shown in Flg. 77 are fPd to the ~p~der 503 where they ~re e~p~nded before transferred through the ~wi~ch 821a to the mi~er 55~. They are mixed by the mixer 556 to An HDTV
signal which is fed through the ter~inal 2 of the switch 7~5a to the output unlt S21 for further delivery. The time-base assignment of data components for transmis6ion> shown in Fig.
77, contributes to the simplest arrangement of the expa~der and mixer. Although Fig. 77 shows two, Dl and D2, sign~l levels, four-level tran~mi~ion of a TV signal wlll be feasible ~sing the addition of a D3 signal and a super resolutioII HDTV signal.
Fig. 7~ strates a time-base ~ssignment of data co~ponents o~ a physical three-level, Dl, D2, D3, TV 8ignal, in which dcta c~ ~n~ts of the sam~ channel are so arranged as not to overlap with one a~other with time. Fi~. 80 is a block diagram of a modified video decoder 423, si~ilar to Fig. ~8, in which a third irLput 521a is added. The time-base a~sigr~ent of data componerts shown in Fi~. 79 also contributes to the simple constructiun of the decoder.

'9~ h~5~ 7~ ~~ / 3~
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The action of thc ~odifi0d decoder 423 is almost identical to that ~hown in Fig. 78 and associated with the time-base assignment shown in Fig. ~7 and will no more be expl3ined. It is also possible to m~ltiplex data componsnts on the Dl slgnal as shown in Fig. 81. Ho~ever, two data 821 and B22 ~re increased higher in the error correetion ~apability than other data components 821a, 812b, 812c, thus ~taying at a higher signal level. More particularly, the data as~ignment for transmission ie m~de in one physlcal level but two logic level rel~tionship. Also, each data compo~erlt of the ~econd channel i~ inserted between two adjacent data components of the first channel 60 that 6erlal processin~ can be. e~ec~ted at the receiver side ~nd the same effects as of the time-base assignment shown in Fig. 79 will thus be l6 obtained.
The time-base assignment of data components 6hown in ~i~. 81 iB based on the logic level mode and can also be carried in ths physical level mode ~hen the bit tr~ns~i6sion rate of the two data components 821 and 822 i~ decreased to 20 1/2 or lf3 thus to lower the error rate. The physical level arrangement is consisted of thrsc different le~els.
Fig. 82 is a blork diagr&m of ~nother modified video decoder 423 for decoding of the Dl signal time-base arranged as showll in ~ig. 81~ which is simpl~r in con~t:ruction than ~5 that shown ln ~ig. 80. Its action is identical to that of the ~ecoder shown in Fig B~ and will be no more explained.
~s understood, the time-base assignment of data ,'!~;~¢ ~:9~3 :~Ci3i ~ 3~3 ~ 1 3 J~
2~9~4~

components ~hown in Fig. ~1 also ~ontributes to the.similar arr.angement of the expander a~d ~ixer. Also, four data components of the Dl sign~l are fed at respective time slices to a ~ixer 556. ~ence, the circuitry arrangement of thP mix~r 656 or a plurality of circuit blocks such as provided in the video ~ixar 548 of Fig. 32 may be arranged for changing the connection therebetween corresponding to each data component so that tAey beco~e compatible in time division a~tion and thus, mi~imiz~d in circuitry construction.
Accordingly, the receiver can be mir... imized in the overall construction.
It would be understood that the fifth embodiment is not limited to ASE modulation and the other methods inr~ludin~ PSK
and QAM modulation, such a~ described in the first, second, and third embodi~ents, will be employed with equQl euccess.
Also, FSK modulation will ~e eligible in any of the embodiments. For example, the signal Points of a multiple-level ~S~ 6ignal consisting o~ four frequency component~ fl, f~, f3, f4 are divided into groups ~9 shown in Fi~. 58 and when the distance betwee~ any two ~roups are spaced from each other for e~se uf discri~in~ti~n, the multl-ievel tr~n~misr~ion of the FSK signal cAn be imple~ented, a~
illustr~t~d in Fig. 83.
More particularly, it is assumed that lhe frequancy group B41 of fl ~nd f2 is assigred Dl=0 and the group B42 of f3 and ~4 i9 assigned Dl=l. If fl and fB represent 0 at D2 and f2 and f4 represent 1 at D2, two-bit data transmission, one ~;, .. ....

.~3~ C~ 3 . .34~ . I.4 i~.
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bit at Dl or D2, will be possibl~ as shown in Fi~. 83. When the C/N rate i8 high, a combination of D~=0 and D2=1 i6 reconstructed at t-t3 and ~ co~bination of D1=1 Qnd D~0 at t=t4. When the C/N rate is low, D1=0 only is repr~duced at g t=t3 and D1=1 at t=t4. In this manTIQr~ the-FSK signal can be transmltted in the ~ulti-level arrangement. This multi-state FSK signal transmi~sio~ is applicable t~ each of ~l}e third, fourth, And ~ifth embodiments.
~he fi~th embodiment may also be implemented ln the form of a magnetic recordfplayback spparatus of which block diagram shown in Fig. 84 because its ASK mode action is appropriate to magnetic record and pl~yb~ck operation.
Embodiment 6 A si~th embodiment of the pres~nt invention is applicable to a magnetic recording and playback Qpparatus.
Although the above-described fifth embodiment applies the present invention to a multiple-level recording ASK data transmission system, it is also fcasible in the same manneI
to adopt thie invention in a magnetic recording Qnd playb~ck appar~tus o~ a multi-level ASE recordin~ sy6tem. A multi-level ~agnetic recording can be re~lized by incorpor~ting the C-CDM system o~ -the pre6ent invention to PSX, FCK, and QAM, as well as ASE.
First of all, the method of re~llzing a multi-level recording in a 16 QAM ~r 32 QAM mngnetic recording playback apparatus will be e~plained with reference to the C-CDM
system of the pre6ent invention. Fig. 84 is a circuit block ~c~ ,32;3 .3~ ti ~
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diagram showing a QAM syste~ incorporQting C-CDM modulator.
~nreinafter, a QAM system being multiplexed by the C-CDM
mod~lator is termed as SRQAM.
As shown in Fig. 84, an input video signal, e.g. ar. ~DTV
signal, to a magnetic record~playback apparatus 851 i5 divided and compressed by a video encoder 401 i~to a low frequency band signal through n first video encoder 40la and a high frequency band ~ignal through a ~econd video encoder 401b re~pectively. Then, a low frequency ba~d ru~ponent, e.g. HLVL, of the video signal i9 fed to a first data stream input 743 of an input section 742 and a high frequency band component lncluding ~VR is fed to ~ second data strea~ input 744 of the same. The two component~ are further trQ~sferr~d to a modulator 749 of a modulator/demodulator unit a52. The fir6t data stream input 743 adds an error correcting c~de to the low frequency band signal in an ECC 743a. On the other hand, the second d~ta str~a~ fed into the second data stream input 74~ 2 bit in ca4e of 16 S~Q~M, 3 bit in case of 36 SRQAM, and 4 bit in ca~e of 64 ~RQ~M. After an error correcting code being encoded ln an EC.C 744a, this ~ignal is supplied to a Trelli6 encoder 744b in which a-~rellis encoded signal having a r~tio 1~2 in csse of 16 SRQAM, 2/3 in ~a6e of 32 S~QAM, and 3/4 in case of 64 SRQAM i 6 produ~ed. A 64 SRQAM 6ignal, for e~a~ple, ~.B8 a first data stream of ~ bit and a second data stream of 4 bit. A Trellis encoder of Fig.
128 allows this 64 SRQAM sig~al to perform ~ Trel~is encoding of ratio 3~4 wherain 3 bit data is ~onverted into 4 bit d~ta.

~ c ~ : q , -- . 33~
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Th~s redundancy increases and ~ d~ta rate decreases, while error correcting capability ircreases. This results in the reduction of an error rate in the same data rate.
Accordingly, transmittable information smount of the recording/playbac~ s~st~m or trans~ission syst~m will i~crea~e substantially.
It is however, pos~ible ~o constitute the first data stream input 743 to exclude a Tre}li~ encoder as shown in Fig. 84 o~ this si~th embodiment bec~use the first data stream has low error rate inherently. This will be advantageou~ in view of simplification of circuit configuratlon. The secorld data stream, however, has ~ narrow inter-code distance a~ compared with the first data strea~
and/ thereforel has a worse error rate. ~he Trellis encoding 15 of the second dat~ stream improves such a worse error rate.
It is no doubt that an overall circuit cDnfiguration becomes simple if the Trelli6 encoding of the fir~t datQ strea~ is eliminated. An opuration for modulation is almost identical to that of the trQnsmitter of the fi~th embodiment shown in Fig. 64 and will ~e no more e~plAined. A modulated signal of the modul~tor 74~ i~ fed into a recording/playback circuit 853 in which lt is AC biased by a bias generator 856 and ~mplified by an amplifier 85~a. ThPreafter, the sigIlal is fed to a ~agnetic head ~54 for recording onto a magnetic tape 855.
A fnrmat of the recording signal is shown in a recording signal frequency assignment of Fig. 113. A main, e.g. 16 ~ ;15 ~

. 3 i~ J ? I 3 J 5 209249~

SRQAM, signal 859 ha~ing a carrier of fre~uency fc rerords information, and also a pilot fp signal 85~a having a frequency ~fc is recorded simult~neou~ly. Distortion in the recording operation is lowered as a bias signal 859b having a frequency ~I~ add6 AC bias fo~ ~agn~tic r~cording. Two of three-level ~ignal9 shown in Fig. 113 are recorded in ~ultiple st~te. In order to reproduce these re~orded signals, two thresholdY Th-1-2, Th-2 aru given. A signal 859 will reproduce ~ll of two levcl~ while a stgnal 86~c will reproduce ~l data onlyt dependirg on the C/N level of the recording/playback.
A ~ain signal o~ 16 SRQAM will have a si~nal point as~ignment shown in Fig. 10. Furthermore, H main signal of 36 SRQAM will h~e a signal pDint assignment shown in Fig. 100.
In rcproduction of this sig~al, both ths main sigllal 85~ and the pilot ~ignal 859a nre reproduced through the magnetic head 8S4 and a~plified by an amplifier 857b. An output signal of the amplifier 857b i~ fed to a carrier reproduction circuit 85~ in which ~ filter 858a soparate~ the frequen~y of the pilot signal fp having a frequency 2fO and a 1/2 ~requency dividsr 858b reproduces ~ carrier of froquency eo to tranofer it to a demodulator 760~ ~hi~ reproduced c~rier is used to demodulate the ~ain signal in the demodulator 760.
Assuming that ~ ma~netic recording tape 855, e~g. HDTV tupe, 25 i9 of high C/~ rate, 16 sign~l points are discriminatabl~ and thus both Dl ùnd D2 are demodulated in thP demodulator 760.
~ubsequently, a video decoder 40Z reproduce all the ~ignals.

~-J .~ L ~ s~ 3J
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An HDTV VCR can reproduce a high bit-rate TV signal such as a 1~ Mbps H~TV signnl. The low the C/N rate, the cheaper the cost of a video tape. So far, ~ VHS tape in the m~rket i6 inferior mor~ than 10 dB in the C~N rate to a ful1-6cale broadea~t tape. If a video tape 85~ is of low CtN rate, it will ~ot be ~ble to di~criminate all the 16 or 32 v~lued signal points. Therefore the first dat~ stream Dl can be reproduced, while a 2 bit, 3 bit, or 4 bit data stream of the second dat~ stream D2 car~ot be reproduced. Only 2 bit data stream of the first data stream is reproduced. If a two-level HDTV vldeo signal is recorded and repr~duced, a low C/N
tape having insufficient c~pability of reproducing a hign frequency band video signal can output only a low rate low frequen~y band video signal of the first data stream, 6pecifically e.g. a 7 Mbps wide NTSC TV ~ignal.
As shown in a block diagram of Fig. 114, the ~econd data 6tream output 7~9, the second data stream input 744, snd the second video decoder 402a can be eliminated in order to provide customers one aspect of lower grade products. In this case, a recordi~g/playback apparatus 851, dedicated to a low bit rate, will inciude ~ r~odulator such a8 a ~odified QP~K which ~odulates and demodulate~ the ~irst data stream only. T~is apparstus allows only the first dats ~tream ~o be recorded and reproduced. SpecificallY, a wide NTSC grade video sigllal can be recorded and repr~duced Above-d~scribed high C/N rate video tape B55 capable of recording a hlgh bit-rate signal, e.g. HDT~ si~r~al, will be 3~ 3 r~ h l~r\j~ T~ No v~ P. 1 ;3i3 ~

able to ~se in such a low bit-rate dedicated ma~netic rccording/ylayback appnratus but will reproduc~ the first data strea~ D1 only That i~, the wide NTSC signal is outputted, while the secord data stre~ is not reproducecl. In other words, on~ recording~playback apparatus having a complicated configuration can reproduce a HDTV ~l~nal and the other recording/playback apparatus having a si~ple configuration ran reproduce a wide NTSC signal if ~ given video tape B55 i~cludes the same multi-level HDTV signal.
10 ACCOIding1Y in ca6e of two-level multiple state, four co~binations will be realized with perfect compatibility amo~g two tapes having different C/N rates an~ two recording/playback apparatus having different recordin~/playback data rates. This will bring remarkable effect. In this case, an NTSC dedicated apparatus will be simple in construction aS compared with an HDTV dedi~ated apparatus. In more detail, a circuit scale of ED~V decoder will ~e 1~6 of that of RDTV decode~. Thar~irore, ~ low function apparatus can be realized at fairlY low cost.
Realizati~n of two, HDTV and EDTV, types recordin~/playback apparatus having di~ierent recordinx~reproducing capability of picture quality will provide various type products ranging in a wide price range. ~sers can freely select a tape a~org a plurality of tapes, from an e~pPnsi~e high C~N rate tape to a cheaper low C/N rat.e tape, ~s occasion dem~nds so as to satisfy required picture quality. Not only ~aintaining perfect compatibility but obtaining e~pandable capability llS

.~q3¢ 3~ 3 .~ 3, !~
2092~

~ill ba attained and further compatibility with a future syctem will be e~sured. Conse4uently, it will be possible to establish long-lasting 6tandards for recording/playback apparatu~. Other reco~ding methods will be used in the ~ame manner. For example, a multi-]evel recording will be realized b~ use of phase modulation explained in the first and third embodiments~ A recording using ASR e~plained in the fifth e~bodimont will also be poseible. A multiple ~tate will be reali~ed ~y converting preAsent recording from two-level to four-level and dividin~ into two groups a~ shown in Figs. 59(~ nd 59(d~.
A circuit block diagram for ASE i~ identical t~ that disclosed in Flg. B4. Besides embodiments already described, a multi-level recording will be also realized by use of 1~ multiple tracks on a magnetic tape. Further~ore, theoretical multi-lsvel recording will be fe~sible by differentiatin~ the error correcting capability 90 as to discrimin~te respective data.
Compatibility with f~ture standards will be described below. A setting of standards for recording/playback appar~tus such as VC~ is normally e~ecu~ed by takin~ account of the ~ost hi6he~t C~N rate ~ape ~ailable in practice. The recording characteristics of tapes progresses rapidly. For e~ample~ the C~N rate has been impr-oved more than 10 dB
co~pared with the tape used 10 years ago. If supposed that new standards will be establishe~ after 10 to ZO years due to an adval~c~ent of tape property, a converltional method will ~ ~ " ~.A l '3~3~2-1a ~ ~0~ <~ '3'~
2092~9~

encounter with difficulty in maintaining compatibility with older standards. NBW and old ~tandards, in Eact, uced to be one-way compatible or non-compatible with each other. ~ ~E
contrary, in arcordance with the present invention, the standards are first o~ all e~t~.blished for recording and/or reproducing the firfit data ctream and/or second data ~tream on present day tapes. Subsequently, if the C/N rate is improved magnificently in future, sn upper level data Rtream, e.g. a third dat~ stream, will be added without any difficulty a~ long as the precent invention i5 incorporated in the ~y~tem. For exa~ple, a super HDTV VCR capable of recording or reproducing a three-level 64 SRQAM signal will be realized hhile maintaining perfect compatibility wi~h the conventional s~andards. A ma~netic tape, recording first to third data streams in compli~nce with new standards, will be able to use, of cause, in the older two-level magnetic recording/playbac~ apparatus capuble of recording snd~or reproducing only first and ~econd dat~ streams. In this case, first and ~econd data streams can be reproduced perfectly although the third data ~tream is left non-reproduc*d.
Therefore, an HDTV ~ignal can be reproduoed. For the~e reasons, the merit o~ expanding recording data amount while maintaining compatibility between new and old standards is e~pected.
Returning to the explanation of reproducing operation of Fig. 84, the maglletic head 8~4 and the magnetic reproduction circuit 853 reproduce a reproducing signal fro~ the ma~netic !~93- .i~''3 .3~ ; . 13~ ?. 12' 3~
20~2~S

tape 855 and feeds it to the modulation/demodulation circuit 852. The demodulating operation is ~l~ost ideDtical with that of first, third, and fourth e~bodim~nts and will no further ~e e~plained~ The demodulator 760 reproduces the first and ~econd data streams Dl and Dz. The second data ~tre~m D2 i9 error corrected with high code gain i~ a Trellis-decoder 759b such ~9 ~ Vitabi decoder, ~o ag to be low error rate. The video decoder 402 dPmod~l~tes Dl and Da sign~ls to output an HDTV videc sign~l.
Fig. 131 is a block diagram #h~wing a three-levcl magnetic recording/playback apparatus in ~ccordance with the present invention which includes one theoretical level in addition to two physicsl levels. This system is substantially the same as that of Fig. 84. The di~ference ls that the first data ~tream is further divided into two subchannels by use o~
a TDM in order to realiza a three-level constructior..
Ac shown in Fig. 131, an HDrV signal is sepRr&tod first of all into two, medium and low frequency band video signals Dl-l and Dl2, through a 1-1 video encoder 401c and a 1-2 video encoder 401d and, thereafter, fed into a first data ~tream input 743 of an in~ut section 742. The data stream Dl_l having ~ picture quality of MPEG grade is error correcting coded with high code gain in an ECC encoder 743a, while the d~ta stream .Dl_2 ls error correctlng roded with nor~al code g~ in an ECC encoder 743~. Dl~ and Dl~2 are time multiple~ed togeth~r in a TDM 743c to be on~ dat~ stre~m Dl.
Dl and D2 are modulated into two-level signal in a C~-CDM 749 135. ~q253 .~ J . L ~ 3~31J.
2~92~

and then recorded on the magnetic tape 855 through the magnetic head 854.
In playback operatior., a recording signal reprod-~ced through the magnetic head 8~4 is demodulated inte D1 and D2 by the C-CDM demodulator 760 in the same manner as in the e~planation cf Fig. 84. The fir~t datQ ctream D1 i~
demodulated into two, D1_1 and Dl_2, subchannels through the TDM 75~c provided in the first data stream output 75B. D1_1 data i~ erro~ corrected in an ECC decoder 7~8a having high code gain. Therefore, Dl_1 data can be demodulated at a lower C/~ rate a9 compared with Dl2 data. A 1-1 video decoder 402a decode~ the D11 data and outputs an LDTV signal. On the other hand, D12 data is error corrected in aII ECC decoder 758b havin~ nor~al code gain. Therefore, D1_2 data has a threshold value of high C~N rate compared with D1_1 data and thus will not be demodulated when a signal level is rot large. D12 ~ata le tnen aemoaulat~ ln ~ v~deo do~der ~O~d ~
sum~ed ~ith Dl_l data to output an EDTV eignal of wide NTSC
grade.
The second data stream D2 is Vitabi d~odulated in Trellis d~coder 75~b and error c~rrected at an ECC decoder 769a. Thereafter, D2 data i~ converted into a high .requency band video signal through a second video decoder 402b and, then, summed with Dil and Dl2 data to ou~p~t an HDTV sig~
In this case, a threshDld value of the C/N rate of D2 data i6 9et larger than that of C/N rate of Dl2 data. ~ccording~y, D11 data, i~e. an LDTV signal, will be reproduced from a tape 3~ ~''.3 13~;37~ t~o;~ llc. ' ~Q ?. 12~3~
~, 2~92~g~i 855 having a ~maller C/N rate. D11 and D12 data, i.e. an EDTV
signal, will be reproduced from a tape B55 having a normal C~N rate~ And, D1_l, D12~ and D2 data, i.e. an HDTV signal, will be reproduced from a tap~ 855 having a high C/N rate.
Three-levelmagnetic recording/playbac~ apparatus c~n b~
realized in thi~ manner. As described in the foregoing description, the tape 855 ha~ an interrelation between C/N
rate and cost. The present invention allows u6ers to 6elect a grade of tape in accordance with a content of TV program they want to record because video signal~ having picture qualitiee of three grades can be recorded andtor reproduced in accord~nre with tape cost.
Ne~t, an effect of multi-level recording will be described with r~cpect to fa6t feed pla~back. A~ shown in a recording track dia~ram of Fig. 13~, a recording track 855a having ~n azimuth angle A and a recording track 855b having an o~posite azi~uth angle B are alternately ~rr~yed on the magnetic tape 855. The recording track 855a has a recordlng region B55c at its central portion and the remai~der a~ Dl_2 recording region~ 855d, as denoted in t~e drawing. Thi6 unique r~cordlng pattern is provided on at least o~e of several recording track~. The recording region 855c record6 one fr~me of LDTV 6ignal~ A high frequency band ~ignal Dz i6 recorded on a D2 recording region ~55e corre~ponding to an entire recording region of the r~cording track 855a. ~his rerordiug format cau~es no no~-el ef~ect again6t a normal speed recording/playback operation.

~ 2~ 3~ l; 3~8 ~ J/J'5 , 20g24~5i A fast feed reproduction in a reverse direction does not allow a magnetic head trace 855f havin~ an azi~uth anOEle A to coincide with the magnetic track as ohown in the dr~wing. Afi the present invention provides the Dl_l recordin~ region 855c at a central narrow region of the magnetic tape a8 shown in Fig. 132, thi6 region only i8 surely reproduced although it occurs with a predeter~ined probabllity. Thus reproduced Dl 1 signal can demodulate an entire picture plane of the s~me time although its picture quu~ity i~ an LDTV of MPEGl level.
In this ~Qnner several to sev~ral tens LDTV ~ignals per ~econd can be reproduced with perfect pict~re images during the fast feed ~layback operation, thereby enabling user~ to surely confirm picture images during the fast feed operation.
A head trace 855g corre6ponds to a head trace Ln the reverse playback operation, from which it is understood only a p~rt of the magnetic track i6 traced in the rever.~e playback operation. The recording/playback f~rmat shown in ~ig. 132 how-ever allow~, even in surh a reverse plarback operation, to reproduce ~l~1 recording region a~d, therefore, un animation of LDTV grade is outputted intermittently.
Accurdingly, the pre~ent inventi~n m~kes it possible to record a picture image of LDTV gr~de within a narrow region on the recording track, which res~lts in inter~ittent quality of LDTV grade durin~ normal and reverse fa6t fe~d pl~ybuck operations. Thus, the useIs can easily confirm picture imaged ~ven in high-6peed se~rchin~.

~ ,q~~se ~J~'4~ 4~ 3iv~5 Next, another method ~ill be dascri~ed to respond a higher ~peed fast fesd pl~yback operstien. A Dl_l recording region 8~5c iB provided as shown at ;ower right of Fig. 132, so that one frame of LD*V signal is recorded thereon.
Furthermore, a narrow Dl_l Dq recording reglon 855h i6 provided at a part of the ~l-l recording region ~5c. A
subchannel D1_1 in this region record~ a part of information reluting to the one fr~me of LDTV signal. The rem~inder of the LDTV iniormRtion i~ recorded ~l the D2 recording region ~55j of the Dl_1 D2 recording region B55h in a duplicated manner. The subchannel D2 has a data recording c~pncity 3 to tl~e~ as much as the subchP~Inel Dl_l. Therefore, subchannel B D1_l and D2 can record oDe frame information of LDTV signal on a smaller, 1~3~1/5, area oE the reoording tape. As the head trace can be recorded in a ~urther narrower regions 855h, 85Sj, both time and area are decreased into 1~3 1~5 as compared with a head trace tiGe TSl. Even if the trace of head is further inclined by increasing the fa~t feed speed a~ount, the prooability o~ entirely tracing this region will be increased. Accordingly, ~erfect LDTV picture i~Hge~
will be irltermittently reproduced even if the fa6t feed s~eed i~ increased up to 3 to 5 time6 as fast as the case of the ~ubchannel ~1-1 only.
In case of a two~level VCR, this method iB useless in reproducing the Vz recording region 855j and therefore this region ~ill not be reproduced ~n ~ high~speed fast feed playback operation. On the other hand, a three-level high .~J< 3~Z~ 4T ~ 1.; 3J5 -2~9~

performance VCR will allow users to confirm a pictu,e image even if a fast feed playback operation is e~ecuted at a faster, 3 to S as fsst a~ the t~o-level VCR, speed. In other word~, not on~y excellent picture quality is obtnined in accordance with cost but a ~aximum fa~t i'eed speed c~pable of reproducing picture images can be increased in accordance with the C06 t .
Although this embodiment utilizes a multi-level modulatior~ system, it i9 needle~6 to say that a norma]., e.g.
16 QAM, modulation 6ystem can also be adopted to realize the fast feed playback oPeration in accordance with the present invention as long as an encoding of picture i~ages is of multiple type.
A recording method of a conve~tional non~multiple ~igital VCR, in whi~h picture images are highly co~pressed, disper6es video ~ata uniformly. Therefore, it was not po6sible i~ a fast feed playback operatinn to reproduce all the picture image~ on a picture plane of the ca~ tim~. The picture reproduced was the one con6isti~g of plurality of picture image blocks having non-coincided time bases with each other. The prese~t irvenLion, however, provides a multi-level ~TV VCR which can reproduce picture image blocks having coincided time bsses on an entire picture plane during a ~ast feed playback operatior. although it~ plcture qu~lity 25 is of LDTV gra~e.
The three-level recording in accordance with the present inve~tion will be able to reproduce a high resolution TV

!3'~ 2~ 3~15~ c ~4<
209%~9~

signQl surh as ~DTV signal when the r~curding~playback system h~s a high CJN r~te. Meanwhile, B TV ~igral of ED~V grade, e.g. ~ wide ~TSC signal, or a TV signsl of LDTV grade, e.g.
a low resol~tion NT8C ~ignal, will be reproduced wherl the recording/playback syste~ has a low C/N r~te or poor function.
A6 ie d~scribed in the foregoing de6cription, the magnetic recording/playback apparatus in arcordance with the present invontion can reproduce picture image~ consi~ting of the same content even if the C/N rate iB low or an error rate is high, although the resolution or the picture quality i8 relatively low.
odiment 7 A 6eventh embodiment of the present inventlon will be de~cribed for execution of four-level video 6ignal transmission. A co~bination Df the four-level signal trancmission snd th~ four-level video dats construction will creAte a four-level slgnal 6ervice area a~ shown in Fig. 91.
Th~ f~ur-level ~ervice are~ is consisted of, from innermost, a first B~OA~ a serond 890b, a third B90c, ~nd a fourth signal receivl~g area 890d. The method of ~eveloping such a four-level service are~ will be explained in m~re detail.
The four-level arrangement c~n be i~plemented by using fo~r phy~ically dif~erent levels determined through modulation or four lo~ic le~el~ defined by data discrimina~ion in the error correction c~pability. The former provides a large difference in the C~N rate between two 1;~7 i~.3 .~ 5L. I~9~l5, ~ L ~ ~ ., . 3i~ . . 9 33~
2~9~9~

~djacent levels and the C/N rate has to ~e increased to discriminate all the four level~ from each other. The latter .6 based on the ~ction of demodulation and a diff~rencs in the CJN rate between two adjdcent levels should stay at minimum. Hence, the four-level al~rangement is be~t constructed using a combination of two phyciral levels and two logic level~. The division of a video signal lnto four signal level6 wlll be e~plained.
Fig. 93 is ~ block diagram of a divider circuit 3 which comprise6 ~ video divider B~5 and four compre~ors 405a, 405b, 405c, 405d. The video divider 895 contains three dividers 404a, 404b, 404c wh~ch are arranged identical to the divider circuit 404 of the first video encoder 401 shown in Fi~. 30 and wlll be no more explaired. An input video signal is divided by the dividers into four components, HLVL of ~ow resolution data, H~V8 of high reso]ution data, and HLV~ and L for medium rseolution dat~. The recolution of HLV~ i6 a half that of the origlnal input ~ignal.
The i~put video sign~l iR first dividad b~ the divider 404a into two, high an~ low, frequency band components, each component being divided into two, horizontal and vertical, ~eg~ents. The intermediate between tb~ high and low frequency range6 i~ a dividing point according to the embodiment.
Hence, if the in~ut video ~ignal is an HD~V signal of 1000-line vertical resolution, ~LVL ha~ a vertical resolution of500 lines and a horizontal resolution of a half value.
Each of two, hori~ontal and vertical, d~ta of the low 12~

13~ t~ ~;,,. !343 ? 1~ 5 20~9~
,:
frequenc~- co~ponent HL~L i~ further divided ~y th~ divider 4~4c into two frequ~ncy b~nd segments. Hence, ~rl HLVL 6egment output i9 250 ]ine~ iD the vertical resolution and l~4 Or the original hori~ontal resolution. T~is o~tput of the divider S 404c which i~ termed as an LL signal is then compressed by the compressor 405a to a Di_l signal.
The other three higher f~equency ~egments of HLVL are mixed by a ~ixer 772c to an LH signal which i~ then compressed by the compr~ssor 405b to a Dl_a signal. The compressor 405b may be replaced wi~h three compressorY
provided between the divider 404c and the mixer 772c.
N~V3, HyVL,and H~V~ form the divider 404a are mi~ed by a mi~er 772a to an HBV~-H signal. If the input signal is as high as lO00 lines in both horizontal and vertical resolution, 15 ~V~-H has 500 to lO00 lines of a horizontal and a vertical re~olution. H~VH-H is fed to the divider 404b where it iB
divided again into four co~ponents.
Similarly, HLVL from the divider 404b has 500 to 750 lines of a horizontal ard a vertical resolution and trans$erred as an ~L si~nai to the compressor 405c. The other three components, XLV~, H~VL, and HEV~, from the divider 404b have 750 to loOo llnes of a horizontal and a vertical resolution and ~r~ ~ixed by a mixer 772b to an HH signal which iB then compressed by the co~pressor 40~d and delivered ~5 &s a D~02 si~nal. After cGmpression, the HL sigral is delivered as a D2_l signal. As the result J LL or Dl_l carries a frequency data of 0 to 250 lines, LH or Dl_2 carries a 12g 1 3 ~ . "~ ~ 3 . ~ 3 ~ . . 3 4 3 ~ . I . J 5 .
209249~

frequency data from more tha~ 250 lines up to 500 line~, HL
or Dz_l carries a frequency data of more than 500 lines up to 750 line6, and ~ or D2_2 carries a frequency data of more than 750 lines to 1000 lires so tha~ the divider circuit 3 can provide a four-level signal. Accordingly, whe~ the divid~r circuit 3 nf the transmitter 1 shown in Fig. B7 i~
replaced with the divider circuit of Fig. 03, the tr~nsmisiion o~ a four-level sign~l will be i~plemented.
The cu~bination o~ multi-levcl d~ta and ~ulti-level transmission allows a video sign~l to be at Rteps declined in the p~cture quality in proportion to the C/N rate during transmission, thus contributing to the ~nlargement of the TV
broadca6t service area. At the receiving side, the action of demodulation and recon~truction is identic~l to that of ~he secoud receiver of the 6econd embodiment shown in Fig. 88 ~nd will be no more expl~ined. In particular, the mixer 37 is modified for video sig~ldl transmission rather than data communication6 and will now be explained in more detail As described in the second embodiment, a received signal ~0 after demodulated ard error corrected, is ~ed a~ a set of four comporlent6 Dl_l, D12, D2l, D~2 to the mi~er 37 of the second receiver 33 of Fig. 88.
Fig. 94 is a block di~ram of a modiEied ~ixer 33 in which Dll~ Dl-2~ D2-l~ D~2 are explained by their respective expa~ders ~23a, 523b, 5~3c, 523d to an LL, and LH, Qr~ HL, and an HH signal respectively which are equivalent to those described with Fi~. 93. If the bandwidth of thP input 6ign~1 CA 0209249~ 1998-03-23 iS 1, LL has a bandwidth of 1/4, LL+LH has a bandwidth of 1/2, LL+LH+HL has a bandwidth of 3/4, and LL+LH+HL+HH has a bandwidth of 1. The LH signal is then divided by a divider 531a and mixed by a video mixer 548a with the LL signal. An output of the video mixer 548a is transferred to an HLVL
terminal of a video mixer 548c. The video mixer 53la is identical to that of the second decoder 527 of Fig. 32 and will be no more explained. Also, the HH signal is divided by a divider 531b and fed to a video mixer 548b. At the video mixer 548b, the HH signal is mixed with the HL signal to an HHVH-H signal which is then divided by a divider 531c and sent to the video mixer 548c. At the video mixer 548c, HHVH-H is combined with the sum signal of LH and LL to a video output.
The video output of the mixer 33 is then transferred to the output unit 36 of the second receiver shown in Fig. 88 where it is converted to a TV signal for delivery. If the original signal has 1050 lines of vertical resolution or is an HDTV
signal of about 1000-line resolution, its four different signal level components can be intercepted in their respective signal receiving areas shown in Fig. 91.
The picture quality of the four different components will be described in more detail. The illustration of Fig. 92 represents a combination of Figs. 86 and 91. As apparent, when the C/N rate increases, the overall signal level of amount of data is increased from 862d to 862a by steps of four signal levels D11, D12, D21, D2-2.
Also, as shown in Fig. 95, the four different level .3~3~ 3,~ ~- .3~ . 343 .. l.~.3~

20~2~9~

components LL, LH, HL, and HH are accu~ulated in proportioQ
to the C/N ~ate. More speci~ically, the quality of a reproduced picture will be increaced as the distance fron~ a transmitter antemla becomes s~all. When L=Ld, LL component is reproduced. When L=Lc, LL~LH signal is reproduced. When L=Lb, LL+LH~L signal i5 repro~uced~ When L-La, LL~LH~L+HX slgnal is reproduced. As the result, if the bandwidth of the original signal is 1, the picture quality is enhanced at 1/4 increments of bandwidth from 1/4 to 1 depending on the receiving area. If the original sign~1 is an HDTV o~ 1000-linc vertical resolution, a reproduced TV signal is 250, 500, 750, and lO00 line~ ln the resolution at their respective receiving areas. The picture quality will thus be varied at steps depending or the level of a signal. Fig. 96 show~ the signal propagation of a conventio~al digital HDTV sig~al tra~emission systsm, in which no signal reproduction will be ~06sible when the C~ rate is less than V0. Also, signal interception will hardly b~ gusranteed at signal interference regions, shadow regions, and other signal attenuating regions, denoted by the ~nbol ~, of the service area. ~ig.
97 shows the elgnal propasation of an HDTV signal transmissi~n system of the ~resent invention. As shown, the picture quality will be a full 1000-line grade at the distance La where C~N=a, a 750-line grade at the dist~llce Lb where CtN=~ a 500-line grade at the distance Lc where C/N-c, and a 2~0-line grade at the distanre Ld where C/N=d. Within the distance La, there a~e shown unfavora~le regions where CA 0209249~ 1998-03-23 the C/N rate drops sharply and no HDTV quality picture will be reproduced. As understood, a lower picture quality signal can however be intercepted and reproduced according to the multi-level signal transmission system of the present invention.
For example, the picture quality will be a 750-line grade at the point B in a building shadow area, a 250-line grade at the point D in a running train, a 750-line grade at the point F in a ghost developing area, a 250-line grade at the point G in a running car, a 250-line grade at the point L in a neighbour signal interference area. As set forth above, the signal transmission system of the present invention allows a TV
signal to be successfully received at a grade in the area where the conventional system is poorly qualified, thus increasing its service area. Fig. 98 shows an example of simultaneous broadcasting of four different TV programs, in which three quality programs C, B, A are transmitted on their respective channels Dl2, D2l, D22 while a program D identical to that of a local analogue TV station is propagated on the Dll channel. Accordingly, while the program D is kept available at simulcast service, the other three programs can also be distributed on air for offering a multiple program broadcast service.

Embodiment 8 Hereinafter, an eighth embodiment of the present invention will be explained referring to the drawings. The eighth embodiment employs a multi-level signal transmission system of the present invention for transmission/reception in U 3 ~ L 3 1 ~ ~ 5 . ~ ~ ! 2 j '~ V ?, ~ / 3 v 5 2~92~9~

a cellular telephone 6ystem.
Fig. 115 is a block diagram showing transmitter/receiver of a portable telephone, in which a telephone conversation sound inputted across a microphone 762 is compres6ed and coded in a co~pre~sor 405 into multi-level, Dl~ ~a~ Bnd D3, dnta previously described. These Dl, D2, and D3 data are time divided in a time d~vision circuit 765 into predetermined ti~e slots and, then, modulated in a modulator 4 into a multi-level, e.g. SRQAM, signAl previously described. There~fter, an antenna shari~g unit 764 a~d an antennQ Z~ trans~it B csrrier wave carrying a modulated signal~ which will be irtercepted by a base st~tion later described and further transmitted to other ba~e stations or a central teleph~n~ e~changer so as tv com~unicate wlth other telephones.
~n the contrary, the antenna 22 receives transmission radio wave~ from other base stations as communication signals from o~her telephones. A roceived signal i.s demodulated in a multiple-level, e.g. SRQAM~ type demodulator 4S into Dl, D2, and ~3 data. A timing circuii 767 d~ects timin8 siguals on the basis of demodulated signals. These timing signals are fed into the time division circuit 765. Demodulated signals Dl, Dz, and D3 are fed lnto an e~pander 503 and expanded into a sound signal, which is then trars~itted to a speaker 763 2~ and converted into sound.
Fig. 116 show6 ~ block diagra~ e~e~plari~y showing an arrangement of base stations, ili which three base stations I 9 9 ~ P ' ~ @~ .; o . . ~ I P . , ~ / 3 1J
209249~

771, 77Z, and 773 locate at ce~ter of respective receiving cells 768, 76~, snd 770 of hexagon or circle. Thess base stations 771, 772, and 773 re~pectively has a plurality of transmitter/receiver ~nits 761a~761j each simil~r to that of Fig. 115 so as to have data communication channels equivalent to the nu~ber uf these transmitter/receiver units. A bQse ~tation controller 774 is connected to all the base station3 and always monitors a co~murication traf~ic amount of each base ~tation. Based on the ~onitoring result, the base station controller 774 carries out a~ overall system control includïng allocation of channel frequencies to respective base station8 or control of receiving cells of respective base ~tations.
Fig. 117 is a Vie~- showing a traffic distribution of communication amount in a conventional, e.~ QPSK, system.
A diagram d=A 6hows data 774a and 774b haviD~ frequency utilization efficiency 2 bit/H~, and a diagra~ d=B shows data 774c having frequency utilization efficie~cy 2 bitJHz. A
summation of these dsta 774a, 774b, and 774c becomes a data 774d, which represents a transmission amount of Ach co~sisting of receiving cells 76B and 770. ~requency utilization efflciency of 2 bit~Hz is unifor~ly distributed.
However, density of population in an actual urban area is locally high in several crowded areas 775a, 775b, and 775c 2~ which include buildings concentrated. A data 774e representing a co~u~ication traffic amount shows several peaks at locatioI~s ~ust corresponding to these crowded areas 13~

3 ~ 2 5 ~ i q~ 3 4 ~ -V 1 3 ?/', C 5 209%49~

775a, '775b, and 775c, in contrast with other area having small co~munication a~ount. A capacity of a conventional cell~lar telephone was uniformly set to 2 bit/H~ freq~ency efflciency at entire region as shown by the d~tA 774d irrespective of actual traffic amount TF shown by the datn 774e. It is not effective to ~ive the Lame frequency efficie~cy regardless of actual traffic amount. In order to compensQte this ineffeetiveneYa, the conventional systems have allocated many frequen~ies to the ~egions having a large traffic ~mount, increased channel number, or decrea6ed the recelving cell of the same. However, an increase of channel number is restricted by the frequencY spectrum. Furthermore, corlventional multi-level, e.g. 16 QAM or ~4 QAM, mode trQnsmission 6ystems increase transmission power. A
reduction of receiving cell will induce an increase in number of base stations, whlch will increaee installation cost.
It is ideal for the improvement of an overall system efficiency to increase the frequency efficiency of the region havin~ ~ larger traffic amount and decrease the frequency efficiency of the region having a sma11er traffic amount. A
multi-l~vel ~iKna1 transmission system in accordance with the present invention realizes this id~al modifieation. This will be explained with reference to Fig. 118 showing a communic~tion amount & traffic distribution in accordance with the eighth embodiment of the present invention.
More speci~ically, Fig. 118 shows communication amounts of respective receiving cells 770b, 768, 769, 770, and 770a fi L ~ N ~ 3 ~ 8 ~. 3 ~/ ~ 0 5 209~

takan along a linz A-A'. The receiving cells 768 and 770 utilize 4requencie6 of a chan~el group A, while the receiving cells 770b, 769, and 770~ utilize frequencies of a channel group B which does not overl~p wi~h the charmel ~roup A. The base station controller 774 shD~n in Fig. 116 increase~ or decreases channel number of these channels in accordance with the traffic ~mount of respective receiving cells. In Fi~.
118, a diagram d=A repre~ents a distrlbution of a communication amount of the A channel. A diagram d=B
repres~nts a distribution of a communication amount of the channel. A diagram d=A+~ represents n distribution of a com~unication a~ount of all the channels. A diagr~m TF
represents a communication traffic amount, and a diagram P
shows a distrib~tion of buildings and population.
The receiving cells 768, 769, aDd 770 employ the multi-level, e.g. SRQAM, ~ignal tr~nsmission sy~tem. Therefore, it i~ possible to obtain a frequency utilization ef~iciency of B bit/Hz, three times as large as 2 bit~Hz of QPSK, in the vicinity of the base stat~ons as denoted by d~ta 776a, 776b, and 776c. Mean~hile, the frequency utiliz~tion efficiency dscre~6es at steps from 6 bit~z to 4 bit~Hz, and 4 bit/Hz to 2 bit/~z, ~s it goe6 to suburban area. If the transmission pow~r is insuf~icient, 2 bit/Hz areas ~ecome narrower than the receiving cell~, denoted by dotted li~es 777~, 777b, 777c, of QPSK. However, an equivalent receiving cell will be easily obtained by slightly increasing the ~ran~mission power of the base stations.

'393~ 3,~25~ !3~20~ 4~ ? I,3,~
2092~95 Transmitting/receiving operation of ~ mobile ~tation capa~le of re~ponding to a 64 S~QAM signal is carried out by use of modified QPSK, which is obtained by set a shift amount of S~QAM to S=L, at the pl~ce far from the ba~e station, by use of 1~ SRQAM at the place ~ot ~o fsr from thc s~me, and 64 SRQAM ~t the nearest place. Accordingly, the ma~imu~
transmission pcwer does not lncrease a6 compared with QPSK.
Furthermore, 4 SRQAM type tr~nsmitter/receiver, whose circuit configuration iY si~plified ~8 shown irl a block diagr~m of Fig. 121, will be able to communicate with ~ther telephones while maintainirlg compatibility. That will be ths same in 16 SRQAM type transmitter/receiver shown in a block diagram of Fig. 12Z~ AB a result, three different type telephones having different modul~tion systems will be provided. Small in size and light in weight is important for portable telephone~. In this regard, the 4 S~QAM system having a 6imple circuit configur~tion will be sultable for the user6 who w~nt a small ~nd li~ht telephone although it6 frequency utilizatlon efficiency is low ar~d therefore cost of 20 call may increase. In thi~ manner, the present invention system can s4it f~r a wide varie~y of usage.
AB is explained above, the transmission system having a distribution like d=A+B of Fig. 118, whoYe cap~ci~y is locally altered, is accomplished. Therefore, an overall Z5 frequency utilization efficiency will be much effec~ively improved if layout of base ststion~ is determined to fit for the actual traffic amount denoted by TF. Especially, effect i593 3q25~ 18~'0~ 3, .3~3 .~ ,'33~
2092~9~
.
of the present invention will be ]arge in B ~icro cell system, whose receiving cells are smaller and therefore numerous sub base stations are required. Because a large number of sub base stations can be easily installed at the place having a large traffic amount.
Ne~t, data assign~ent of each time slot will be explained refsrring to Fig, 11~, wherein Fig. ll9(a) shows a conventional time slot a~d Fig. ll9(b) shows a ti~e slot sccording to the eighth embodiment. The conventional system performs a down, i.e. fro~ a base station to a mobile station, transmiss.on aY shown in Fig 119(a), in which a BynC signal S i6 transmitted by a time slot 780a and transmission signals to re6pective portable phones of A, B, C chan~els by time slot~ 7ROb, 78~c, 780d respectively at A
1~ frequency A. On the other hand, an up, i.e. from the mobile station to the bage ~tation, transmiesio~ is performed in such a manner that a sync signal 9, And transmission signals of a, b, c channels are trarl6mitted by time slots 781a, 781b, 781c, 781d at a ~requency B.
The present invention, which is characterized by a multi-level, e.g. 64 SRQAM, si~nal transmisSiOD sy6tem, allows to have three-level data consisting of Dl, D2, ~3 of 2 bit~z as shown in Fig ll9(b). As both of Al and A2 data are transmitted by 16 SRQAM, their time sl~ts have two ti~es data 25 rate as ~hown by slots 782b, 782c and 783b, 783c. It ~eans the sa~ne quality sound can be transmitted by a half time.
Accordingly, a time width of respective ti~e slots 782b, 782c ~!~3~ ~?~ 5 '~ 3~5 2~92495 becomefi a half. In this manner, two times transmi~sion capacity can be ac~uired at the two-level region 776c shown in Fig. llB, i.e. in the vicinity of the base station.
In the same way, time 910t~ 782g, 783g carry out the S transmis~ion~reception nf E1 data by use of a 64 SRQAM
signnl. As the transmission capacity is three times, one time slot can be used for three ch~nnels of El, E2, E3. This would be u~ed for a region further close to the base station.
Thus, up to three times co~m~nication capacity c~n be obtained at the same frequency band. An actu~l trsnsmission efficiency, however, would oe reduced to ~0%. It is desirable for enhancing the effect of the present invention to coincide the transmlssion amount distribution according to the present inventioD with the regional distributiDn of the actual traffic amount as perfect as possible.
In f~ct, an actual urban area consists of a crowded building district and a greenbelt zone surrounding t.his building area. Even an actual suburb area consists of a residential district and fields or a foreet aurroundi~g this Z0 re6idential district. These urban and suburb areas resembl~
the distrib~tion of the TF diagram. Thus, the application of the present invention will be effective.
Fig. 120 i6 a dlagram showing time slots by ~he TDMA
method, wherein Fig. 120(a) shows a convention~l method and Fig. 120(b) shows the present invcntion. The cor~ventional method uses time slots 786a, 786b for transmission to port~ble phones of A, B channel6 at the same frequency and ~40 9v~ 2lE ~ N;,.'34~ ?. ~ 3~
2092~95 time slot~ 787a, 7R7b for transmission fro~ the same, as shown in Fi~. 120(a).
On the contrary, 16 SRQAM mode of the present invention uses a time slot 7~8a for reception of Al channel and a time slot 788c for transmission to Al channel as shown in Fig.
120(b). A width of the time slot becomes nppro~imately 1/2.
In case of ~4 SP.QAM mode, a time s10t 788i is used for reception of Dl cha~nsl and a time slot 7881 i6 used i'or transmission to Dl channel. A width of the time 810t beCO~eB
appro~imately 1/3.
In order to save electric power, a transmis6ion of E1 channel i8 e~ecuted by use of a normal 4 SRUAM time slot 7~8r while reception of El channel ls e~ecuted by use of a lff SRQAM time slot 788p being a l/2 time slot. Trans~is6ion power i5 surely eu~pres6ed, although communication cost may increase due to a long occupation ti~e. This will be effective for a s~all and light portable telephone equipped with a small battery or when the battery is almost worn out.
As is described l~ the i'ore~oin~ description, the present invention makes it possible to determine tbe distributior. of tran6mission capacity so as to coincide with an act~al traf.fic distributior., tAereby lncreasing 6ubstantial trans~issio~l caparity. ~urthermore, the present invention allow6 base stations or ~obile sta~ions ~o freely select one among two or three tra~smission capacities. I~ the frequency utillzation efficiencY is selected lower, power consumption will be decreased. If t~e fre~uency utilization i 3 S 3 ~ r ~ 4 ~ P . 1 3 / 3 ~ 5 efficiency is selected higher, communication cost will be saved. Moreover, adoption of ~q 4 SRQAM mode h&ving sm~ller cqpacity will simplify the circuitry and reduce the size and CGSt of the telephone. As explained in the previous embodimerts, one characteristics oi' the present invent on i6 that compstibility is maintained amon~ all of associated stations. In this mar~er, the prese~t inve~tion not only increases tran~mission capacity but allow~ to provide customer6 a wide v&riety of serie~ fro~ a super mini l~ telephone to a high performance t~lephon~.
Embodiment 9 Hereinafter, a ninth embodiment of the present inverltion will be described referring to the drawings. The ninth embodiment employs this inventian in an OFDM transmission sy~tem. Fig. 123 is a block diagram of an OFDM
transmitter/receiver, and Fig. 124 is a diagram showing a ; principle of an OFDM action. An OFDM is o~e of FDM and ha~
a better effi~iency in frequency utilization ns compared with a ~eneral FDM, because an OFDM eets adjRcent two carriers t~
be quadrature with each other. Furthermore, an OFDM can bear multipath obstruction such as ghost and, ther~ore, ~ay be applied in the future to the digital music broadcasting or digital rv broadcasting.
As shown in the princip~e diagr~ of Fi~. 124, an OFDM
converts an input signal by a serial to parallel converter 791 into a data bein~ disposed on a frequency a~is 7~3 at intervals of 1/ts, so &Q to produce subchannels 794a~794e.

~ 5~ 25~ ;3~ ~T~ N ~4~ ?. 14~3S5 2(~92495 .
This sigral is inversely FFT converted by a modulator 4 having an lnverse FFT 40 into a signal on B time a~is 799 to produce a transmission signnl 7~5. This in~erse FFT signal is transmitted during a~ effective symbol period 7~6 of the time period ts. A guard interval 797 having an amount tg i8 provided betwe~n respective symbol periods.
A trsnsmitting/receiving action of an HDTV signal in accordance ~ith this ninth embodi~ent will be expl~ined referring to the block diagram of Fig. 123, which 6hows a hybrid OFDM-CCDM ey6te~. An inputted HDTV signal is separated by a video encoder 401 into three-level, a low frequency band D~_l, a medium-low frequency band Dl_2, and a high-medium-low frequency band D2, video signals, and fed into an input section 742.
In a fir6t data struam input 743, a Dll signal is ECC
encoded with high code gain and a Dl_2 signsl is ECC encoded with nor~al code gain. A TDM 743 performs time division multiple~ing of Dl1 and D1_2 signals to produce a Dl signsl, which is then fed to a Dl serial to parallel converter 791d in a modulator 852a~ The D1 si~nal consists of n pieces of parsllel data, which are inputted into flrst inputs of n pieces of C-CDM ~odulator 4a, 4b,---respectively.
On the other hand, the high frequency ~and signal D2 is fed into a second data stream lnput 744 of the input section 742, in which the D2 si~nal i~ ECC (Error Corre~tion Code) encoded in an ECC 744a and then Trellis encoded in a Trellis encoder 744b. ThereafterJ the D., signal i6 supplied to B D2 i J i 3~ t ~ 43 p ; J~

2Q92~9~

serial to parallsl corverter 791b of the modul~.tor 8~2a and converted l~to n pi~c~s of p~r~llel d~ta, which are inputted into second in~uts o~ the n pieces of C-CDM modul~tor 4a, 4b,---respectively.
The C-C~M modulators 4a, 4b, 4c-~-re6pectively produces 16 SRQAM signal on the basi~ of the Dl data of the first data stream input and the D2 data of the ~econd data stream input.
These D pieces of C-CDM modulator respectively h~s a carrier dlfferent fro~ each other. As shown in Fig. 124, carriers 10 794a, 7~4b, 794c,---are nrrayed on the fre~uency a~is 793 so that adjacent two cQrriers are 90~-out-oP-phase with each other. Thus C-CDM modulated n pieces of modulated signal are fed into the inverse FFT circuit 40 and ~apped from the frequency axis dimension 793 to the time axis dim~n~ion 7gO.
15 Thus, time sig~als 796a, 796b ---, having an effective ~ymbol length ts, are produced. There is provided a guard interval ~one 797a of Tg second~ between the effective symbol time zones 796a and 796b, in order to reduce multipath ohstruction. Flg. 129 ls a graph showing a relationship between time axis and ~lgnal level. The guard time Tg of the guard interval band 797a is determined by taking ~ccount of multipath af~ection and usage of sign~l. By 6etting the guard time l'g longer than the multipath affection time, s.g. TV
ghDst, ~odulat~d signals from the inverse FFT circuit 40 are 2~ converted by a p~rallel tD serial ~onverter 4e into one signal and, th~n, transmitted from a transmitting circuit 5 as ~n ~F signal.

.31i3 3~25e ;~2~ t~ i34~ r la~ 5 2~92~95 ~ e~t, an ~ction of a receiver 43 will be described. A
received 9ignal, shown as time-base symbol signal 796e of Fi~. 124, is fed into ~n lnput circuit 24 of Fig. 123. Then, the received signal i~ converted into a digital 6i~nal in a demodulator ~62b and further changed into Fourier coefficie~ts in an FFT 40a. Thus, the ~ignal i~ mapped from the time ~xis 799 to the frequency a~is 7~3a a~ ~hown in Fig.
124. That i6, the time-ba~e symbol signal i~ converted into frequency-~ase c~rrler6 7~4a, 794b,---. As these carriers are in quadrQture relationship with ea~h other, it i6 possible to sepurate re6pective modulsted signals. Fig.
125(b) shows thus de~odulated 1~ SRQAM ~ignal, which is then fed to respective C-CDM demodulators 45a, 45b,--of a C-CDM
demodulator 45, in which demodulated 16 SRQAM ~i~nal is demodulated into multi-level sub signals Dl, D2. These sub signals Dl a~d D2 ~re further demodulated by a Dl parallel to ser~al converter 852a and a D2 parallel to serial converter 8~2b into the origlnal D1 and D2 signals.
Since the signal transmis6ior system is of C-CDM multi-level ~hown in 125(b), both D1 and D2 6ig~als will be demodulated under ~ettur receiving condition hut only D
signal will oe demodulated under worse, e.g. low C~N rate, receiving condition. Demodul~ted D1 signal is demodulated in an output section 757. As the Dl_l signal has higher ECC code gain as compared with the D12 signal, an error slgnal of the Dl_l signal is reproduced even under worse receiving condition.

~3~2~ ~ 2~ i3i i~ /3~
2092~9~

The D1l signal is converted by A 1-1 video decoder 402c into a low fre~uency band ~ignal and outputted as an ~DTV, and the D12 signal i5 converted by a 1-2 video decoder 402d into a medium frequency band signal and outputted as EDTV.
The D2 ~ignal is Trellis dec~ded by a Trellis decoder 759b and converted by a se~ond video decoder 402b into a high freque~cy band oignal and outputted as an H~TV signAl.
Namely, an LDTV 6ignal is o~tputted in ease Df the low frequency band signal only. An EDTV ~ignal ~r wide NTSC
grade is outputted if the medium frequency ba~d signal i8 added to the low frequency band sign~l, and an HDTV signal i9 produced by adding low, medium, and high freque~cy band signalc. As well as the previous embodiment, a TV signal having a picture quality depending on a receiving C~N rate 16 c~n be re~eived. Thus, th~ ninth embodiment realizes a novel multi-level ~ignal transmis6ion sy6tem by combining an OFDM
and a C-CDM, which was not obtainsd by the OFDM alone.
An OF~M i8 certainly strong against multipath such a9 TV
ghost because the gu~rd time Tg can abs~rb an interference signal of multipath. Accordingly, the OFDM i6 applic~ble to the digital TV broudcasting for automotive vehicle TV
receivers. Meanwhil~, no OFD~ oignal is recaived when the C/N
rate is less than ~ predeterml~ed value because its signal transmission pattern i~ not of a multi-level type.
However the pr~6ent invention ~an solve this disadvantage by combining the OFDM with the C-CDM, thus reali~ing a graditional degradallon depending on the C/N rate 14~

. 9 S ~ L 3,~5~ i3~24~ 3 ~ l~8/3i~.
20~2~95 -in a video sigral reception without being disturbed by mu~tipnth.
When n TV signal i9 receiv~d in a co~partment of a ~ehicle, not only the reception i6 disturbed by ~ultipath but the C~N rate i6 deteriorated. Therefore, the broadcnst service area of a TV bro~dcnst station will not be e~panded a6 expectsd if the counterme~sure is only for multipath.
On the other hnnd, a reception of TV signal of at least LDTV grade will be ensured by the co~bination with the multi-level transmi6sion C-CDM even if the C/N rate is fairly deteriorated. A~ a picture plane size of an automotive vehicle TV is normally less than 100 inches, a TV signal of an LDTV grade will provide a sati6factory picture qu~lity.
Thu~, the L~TV grade service area of automotive vehicle TV
will lareely e~panded. If an OFDM is used in an e~tire frequency band of HDTV signnl, the present ~emiconductor technologies cannot preve~t circu~t scale from increasing 90 far.
N~w, an OFDM method of transmittin~ only ~ f low frequency band TV signnl will be e~plained below. A~ shown in a block diagram in Fig. 138, a medium frequency band component D12 and a high frequency band component D2 of an HDTV ~ignal are multiple~ed in a C-CDM modulntor 4a, a~d then trans~itted at a frequency band A through an FDM 40d.
On the other hand, a si~nal received by a receiver 43 i~
first of all frequency separated by 4n FDM 40e and, then, demodulated by a C-CDM demodulator 4b of the pre~en~

iJ'.~ 'J~ .d~ P 1-3 .~i~
2092~9~

invention. Thereafter, thus C-CDM demodulated si~nal is reproduced into medium and high frequency components of HDTY
in the same way as in Fi~. 123. An operation of a video decoder 40Z is identical to that of embodiment8 1, 2, and 3 and will no more be e~plained.
Me~nwhile, th~ Dll signal, a low freQuency band signal nf MPEG 1 grade of HDT~, is converted by a seri*l to parAllel converter 791 into a pnr~llel signAl and fed to a~ OFDM
modulator 852c, which e~ecutes a QPSK or 16 QAM modulation.
Subsequently, the D1_l signal is converted by an inverse FFT
40 into a time-base signal and tran6mitted at a frequency band B through the FDM 4~d.
On the other hard, a signal received by the receiver 43 is frequency separated in the FDM 40e and, then, converted into a number of frequency-base siRnals in an FFT 40a of the OFDM modulator 852d. ~hereafter, frequency-base sign~1~ are demodu1ated in respective demodulators 4a, 4b,---and are fed into a parallel to serial converter 882a, wherein a Dl_ signal is demoduiated. Thus, a D1l signal of LD~ grade is outputted from the receiver 43.
In this manner, only an LDTV signal is OFDM modulated in the multi-level signal transmission. The s~tem of Fig. 13B
makes it possi~le to provlde a complicated OFDM cir~uit only for ~n LDTV signal. A bit ratc of LDTV signal is l~ZO of that ~5 of an ~DTV Therefore, the circuit scale of th~ OFDM will be reduc~d to 1/201 which results in an outstanding reduction of overall circuit scale.

5 ~ 1 ~ r ~ ~ 4, . . ! ~ J ~ ~
2092~95 A~ OFDM signal transmission sYstem is strong against multipath and will soon be applied to a mobile station, such as a portable TV, an automotive vehicle TV, or a digital music broadcast receiver, which i8 exposed under strong and variable multipath cbstruction. For such u~ages a small picture ~ize of less than 10 inches, 4 to 8 inches, is the m~in~tream. It will be thus guessed that the OFDM modulation of a h;gh resolution TV signal such as HDTV or EDTV will brin~ less effect. In other words, the reception of a TV
signal of LDTV grade would be suff1cient for an auto~otive vehicle TV.
On the rontrary, multipath is constant at a fi~ed station ~uch as a home TV. Therefore, a countermea~ure against multipath is relatively e~sy. Less effect will be brought to such a fixed station by OFDM unle~s it is in a ghost area. U6ing OFDM for medium and high frequency band components of HDTV is not adv~nt~geous in view of preseDt circuit scale of OFDM which is still large.
Accordingly, the method of ths present invention, in ~hich O~DM is used only for a low frequency b~nd TV sign~l as shown in Fig. 138, can widely reduce the circuit scale of the OFDM to less ~han 1/1~ without losing inherent OFDM effect capable of largely reducing multiple obstruction of LDTV when re~eived at a mobile station such as an automotive vehicle.
Although She OFDM modulation ~f Fig. 138 is performed only for D1l ~ignal, it i8 also possible to modulate both D
and D1_~ by O~DM. In such ~ c~se, ~ C-CDM two-level signal ' 3 4 3 :1~ 2 ~ ~ 1 8~ ~t~ N ,, ' 3 4 ~' ? 1~ ! ~ 3 '~ ~
- 20~24~

tr~n~mi66ion is used for transmission of D1_1 an~ D1_2. Thu~, B multi-level broadcastin~ being strong against multipath will be reali~ed for a vehicle such as an automotive vehicle.
Even in a vehicle, the graditional gr~duation will be realized in such a marner that LDTV and SDTV ~ignals are received wlth picture qualities depending on receiving sigral level or antenna sensitivity.
The multi-level signal transmi6sion according to the present invention is feasible in this maDner and produ~es various effect~ Qs previously de6cribed. Furthermore, if the multi-level signal tran~mission of the present invention i~
incorporated with an CFDM, it will become po6sible to provide a system strong against multipsth and ~o alter data tran6mission grede in accordance with receivable signal level changs.
The multi-level signal transmission method of the present invertion i9 interded to increase the utilization of frequencies but may be suited for not all the tran6mis6ion systems since causing some type receivers to be decline~ in the energy utilization. It is a good idea for use with a satellite communica~ions system for ~elected sub6criber6 to employ mos~ advanced transmitters and receivers designed for best utilization oP applicable frequencie~ and ener~y. Such a speci~ic purpose signal transmission system will ~ot be bo~nd by the present invention.
The pre6ent irvention will be advantageous for use with a satellite or terrestrial broadcast service which i9 q 2 5 9 ! i3~L h7~ ~o~ N 3. i ' ~ 8 . . I, ~ ~ 3 ~ 5 2~392~g5 e6sential to run in the sHme standards for as long as 50 years. During the service period, the broQdcast standard6 must not be ~ltered bnt improvements will be provided time to time corresponding to up-to-d~te technologic~l achievements.

6 Particul~rly, the energy for signal transmi~sion will OEurely be increased on any satellite. Eac~ TV station 6hould provide a compatible service for guaranteeing TV program signal reception to any type receivers ranging from today's common ones to future advanced ones. The sign~l transmission system of the present invention can provide a ~cmpatible broadcast service of both the e~isting NTSC and ~DTV systems and ~lso, ensure a future extension to match mass dat& transmis6ion.
The prefient invention concerns much on the frequency utilization than the energy utilization. The si~n&l receivin~
sensitivity of e~ch receiver i9 arranged di~ferent depending on a sign~l state level to be received so that the transmitting power of a transmitter needs not be ircreQ6ed LarEely. Hence, e~isting sutellites which offer a small energy for reception and tran6mission of ~ signal can best be used with the sy6tem of the present lnvention. The ~ystem i~
also arranged for performing the same standards corresponding to an increase in the transmis6ion ener~y in the ~uture and offering the compatlbility between ~ld and new type receivers. In addition, the present lnvention will be ~ore advantageous for use wlth the sQtellite broadcast standard6.
The multi-level signal transmission ~ethod of the present invention i~ more preferably employed for terrestrial 33~ 7~ . . 3 4 ~, ? . I 3i 3;
2~92~95 TV broadcast service in which the energy ut~lization is not cruc;al, a9 compared with s~tellite broadcast service. The results are such that the signal attenuating regions in a serYice area which are attributed to a conventio~al digital 6 ~DTV broadcast system are considerably reduced iD exten~ion and also, the compatibility of an ~DTV receiver or display with the e~isting NTS~ 6ystem is obtained. Furthermore, the service area is ~ubstantially increased so that program suppliers and 6ponsors can appreciaee more viewer~. Although the embodi~ento of the pre6ent invention refer to 1~ and 32 QAM procedures, other modulation techniques ineluding 84, 128, and 2S6 QAM wlll be employed with equal sucees6. Also, multiple PSK, ASK, and FSR techniques will be applicable as described witb the embodiments.
A combination o~ the TDM with the SRQAM of the present invention has been described in the above. However, the SRQAM
of thu present inventi~n can be combined also with any of the FDM, CDMA and frequency dispersal communicatio~s systems.

Claims (9)

1. An OFDM (Orthogonal Frequency Division Multiplex)-type TV
receiver comprising:
a Fast Fourier transformer (FFT; 40a) for converting a received signal into a group of modulation signals of a plurality of carriers (794; f1, f2, f3---) by applying a Fourier transformation;
a demodulator (45a, 45b, 45c---) for demodulating said modulation signals;
an error correcting section (757) for error correcting the demodulation signals demodulated by said demodulator; and a video decoder (402) for decoding error-corrected signals into TV
signals, wherein said modulation signal is demodulated as a signal consisting of n signal points in a constellation into n-value signal to reproduce a first datastream in a first mode, while said modulated signal is demodulated as a signal consisting of m signal points in the constellation into m-value signal to reproduce a second data stream in a second mode, where m is an integer larger than another integer n, and one of said first mode and said second mode is selected depending on information included in said received signal.

2. The OFDM-type TV receiver in accordance with claim 1, wherein a signal point group (91 in Figs. 6-9) is defined so as to form a group of signal points (83-86, 83a-86a, 83b-86b in Fig. 99) on the constellation of each modulation signal (794 in Fig. 125) of the modulation signal group, and said modulation signal is demodulated considering the signal allocation that a first distance (2n.delta.) between signal points (83) in said signal point group (91) is larger than a second distance (2.delta.) between signal points (83a, 83b) disposed at equal intervals.

3. The OFDM-type TV receiver in accordance with claim 1, wherein said received signal is a demodulated as a signal having n signal points in a certain time domain while said received signal is demodulated as a signal having m signal points in another time domain.

4. The OFDM-type TV receiver in accordance with claim 1, wherein the data carrier (f1, f2, f3---) in an OFDM symbol is regarded as a QPSK or n-value QAM in the demodulation according to information included in the received signal.

5. The OFDM-type TV receiver in accordance with claim 1, wherein demodulation or output of the information relating to the second data stream is stopped when a code error rate is increased, thereby demodulating only the information of the first data stream.

6. The OFDM-type TV receiver in accordance with claim 1, wherein high priority information is demodulated as said first data stream, while low priority information is demodulated as said second data stream.

7. The OFDM-type TV receiver in accordance with claim 1, wherein the information relating to low-resolution video signal is demodulated as said first data stream and the information relating to high-resolution video signal is demodulated as said second data stream.

8. The OFDM-type TV receiver in accordance with claim 1, wherein the demodulation signal is decoded in a convolutional decoder (759b), and the decoded signal is then error corrected and decoded into the video signal through the video decoder (402).

9. The OFDM-type TV receiver in accordance with claim 8, wherein said demodulation signal is a signal encoded by a convolutional encoder (744b in Fig. 128) in a corresponding transmitter (1).