CA2168888A1

CA2168888A1 - Local isdn radio transmission system

Info

Publication number: CA2168888A1
Application number: CA002168888A
Authority: CA
Inventors: Reinhard Schiffel; Klaus Jackel; Bruno Stadler; Holger Vogel
Original assignee: Individual
Current assignee: ADC GmbH
Priority date: 1993-08-05
Filing date: 1994-07-28
Publication date: 1995-02-16
Also published as: AU7262794A; DE4326749A1; CZ33496A3; HUT74330A; ES2118423T3; HU9600253D0; FI960508A; FI960508A0; HU216554B; WO1995005053A1; EP0712561B1; EP0712561A1; DE4326749C2; AU714192B2; DE59406422D1; NO960443L; JPH09501550A; US5774460A; NO960443D0

Abstract

A local ISDN radio transmission system is organized as a local radio cell that consists of a central stationary radio station and of a plurality of decentralized subscriber radio sets. The radio transmission system is connected to the access connection elements (ISDN base access ports) of a local central office, subcentre or private branch exchange.
The number of radio subscribers is larger than the number of used duplex radio channels. The invention ensures to the radio subscribers a connection with a So-interface. The radio transmission in the subscriber area allows covering and propagation time problems encountered in the case of wire transmission. According to the invention, the radio transmission arrangement is inserted into a ISDN two-wire access connection circuit with an intermediate repeater, in the section that extends between the intermediate repeater and the network termination. After an activation request, a radio channel is allocated within the carency and monitoring times for activating the ISDN two-wire access connection circuit. In order to ensure an efficient use of the available transmission bandwidth, an independent radio channel for control, organization and monitoring purposes is dispensed with. The required instructions and information are transmitted in the free radio channels. The subscriber radio sets recognize free channels thanks to a special arrangement of the synchronization word that differs from that of the ISDN transmission.

Description

2168~88 ~o~ ~N ~ ioTrar~cm;.~sion ~ystem Technical Pield The invention relates to a local ISDN transmission ~n w~ich is organized as a loca~ radio oell, ~onsisting of a <æn~l fixed radio station and a plurali~y of sl1bs~h~ radio t~llunals and is connected to the suhs~ber ports (ISDN base conn~ion~) of a local swit~.h~g center, store-and-forward ~ or private branch ~ n~e, and provides s~lbs~;h~ ith access to the public ISDN telephone s~ys~n through an No inte~ e by the use of wireless tran~ sion, and in which, for the o~ AI;on of the- ~rs~u~
in the case of a n~er of s~bs~rihPrs 81~ than the n m~hPr of the duplex radio c~annels (hereinafter called c~llu~ ir~tion ~nels) in use, a radio colnl~ nic~tio~ ~y~ is pr~e~lt in a central fixed radio station (base station BS) wlli~h, in the event of an activation request (PH- -~CTI~TE REQ~ST), opens to the sllbscnh~r radio ~ nal (T~), by means of a special-radio ~ ni~tion ~ccss, any one of the available and free ~ ullunication ~hannels for r~mm-lnication.
SUBSTITUT~ SHEET

-~t~tP of the ~rt The invention relates to a local ISDN radio transmission system according to the preamble of claim 1. It is organized- as a local radio cell wh~ch consists of a ~t~al fixed radio station (BS base station) and a pluralit~r of outside s1lbs~her radio t~nul~als. The object is to use wild~ss transmission in order to provide amess to the public ISDN telephone ne~w~k through an SO int~, r~e for sl~hs~ who for a great variety of r~sons cannot be connected to a ~n~ mications S,~S~ via standardiæd subscriber lines.
Multi-user ~slems for radio-s.~ o~Le~l cor~llec~ion of telephone suhs~ibers to the public telephone ne~wu~k~ are in wide use. They Gome under mainly the following categories: -1. Mobile r~1io ne~These are ~r~c(~ mainly by ~v~ g and handover (ov~rlo~
fa~ilities vnth all of the r~1t~nt conse~uences for the n~ k control and the ~l~om~n~ for the ability to use mobile equipment at high road sp~s of up to 200 kn~h and the r~s~.1t~nt demands placed on the radio tran~mis~ion prooess.

2. Tr~lnk;r~g n~Lwolk.c - These have roaming and handover like the mobile radio n~Lv~/olks, but as regards subs~ ril~r ~ m, tc~ ial ~nt, func~ionalit~r and es~ lly access to the public ncLwol~s th~y are subject to the limitations I~ferl~d to above.

3. Ne~wo~k~ h~l on cordless t~lephone t~nology Ihese l~e~WV~ i are intended tO break the connection of the co~dless telephone to a specific main line and to e~ctend the terdtorial range of use to the range of a PAB~ by inserting a handover.
. n~ (wirel~ Ioop) These are characterized b~ wireless connection of stationary S~ i SHEET

~lG388~

sl.bs.-rihers in the case of a connfflion of the ~adio transmission ~ystem that is ~qual for all sl.hs~ nbers. This means that in the telecommunication ~y~"~ each radio sl~bs. riher has a subscriber line of its own, and the radio translni~ is inserted L~ these subscnber connections and the radio sllhsrriher.
5. Rl~l ne~orks These are char3~ ~ r; ~f J by the fac~ that, from a central node exchange or secondary acchange, they make a point~ multipoint connection in t~ ia~ly ve~y ranote areas, and radio ~onnections are used. Chanrlel gl~s are transmitted w~ich can be split up into several planes en rollte and are sent to several end points. From these end points the sl-hs~ribers are connected usually via cable, and if radio is used, equal~hannel connection is usuall~ rol~ed. In the rural n~w~lhs no swit~hing fimctioIl.c are ~rolllled.
These systems offOE the sllhs~iher in gene~al an a/b conn~ction or adeqllate ~unctions as rega~ds speech communication and modem and fax transmission. To some e~ctent, special connections are offered for data ~ansrnission (data terminals). The data rates can amount to up to 64 kbit/s. These ~ S(~nS are designed for conne~ion to the ISDN and sometimes they provide a few select functions of the ISDN to the S11hSCr;her. The pr~p~r~tion of an llnlimited SO int~ ce, h~ ~, is not one of the ~fG~ anoe fe~tu~es of this ~ L~

So a process is ~esrnh~tl in (1) for offe~ing GSM s~lhs~rs ~c~ess to pelro~ ance features of the ISDN. The process ~f~s~ted~ h~ r, is linuted by the fact that the ISDN sllhs~ih~r plane with 2B+D (2 x 64 kbi~/s) cannot be transl~itted 1:1 to the GSM subscnber plane ~vith Bm Dm (3 or 12 or 9.6 kbit/s) (see (13, Figure 3 and page 1, lines 10 to 19).
So-called D~l (wireless sllhsrriher line) ~y~L~ S are already widely in use and under the a~o~r~gival pr~mi~es th~y have ~lo~ thdr right to ~CiSt.
The sy-stems up to now, h~w~,~, offer the radio sllbs~rihe~ onl~ one sllbsrr;ber }ine with an a/b int~ce. F.y~mrles are given in (2) and (3).

SUB~ ; SEIEE:T

1 6 ~

In (4) a solution is ~e.c- rihed which ;s based on the DECT standard and by using a TDMtIDMA/TDD process ~its the wireless conne~tion of sllhs~ s to PABX's or PSTN s. ~n the system a ~igit~l trar sInission at 32 kbit/s per channel is used, 8 channels being tI~lS~ ~d with an RF
~rnPr, requinng a total gross data rate of 640 kbit/s. This sys~.ll would be suitable if several channels w~e to be ~-ssign~ to one s~ s~her for the pr~essing of SO lines by the sl-hs~ r, but it has two basic consequences.
1. A-rDMAframe ~nth a ~ ~tion of 16 ms is divided into 8 channel pulse frames for the direc~on from the base station to t~ae sl.~s-riber ~....i.~l and 8 channel pulsc frames for the direc~on from the sllbs~riher t~~ aal to the base station, r~ in~ in a duration of 1 ms for the indi~ndual c~annd fr~rn~c Thus, there are no ~ves for propagation ~me compensation (different distances l~h.~l the s~hS~nt~r t~lninal and the base st~ n), and the S.YS~ S limited to Ye~ short distanaes of up to 300 meters.
For the quantification of these sl~tf..~ ts: The a~ievement of a serv~ce range of 30 km radius calls for intermissions of 0.2 ms between the t~ansmissions of two s~lcc~ss;.~ly transmifflng subscriber terminals.

2. The t~nc.nission of 8 ~hannels in ~upl~ operation occupies a radiofrequenc~y band ~ndth of 1 MHz, w~i~h is a~ptable onl~r at the minin~ anges and ~he low t~n~mi~s;on ~o.Y~s of 80 mW which they entail.
Rrief nescription of the Illvel tion.

The invention fl~ ribed herein offers the radio sl-hse~iber a subscriber line with an S0 interface in order to be able to use all of the power features of this modern coI~ullunications technology. In addition tO the premises set forth above which appear to make the use of radio transmission for s~lbsrnhers pr~ctir~l~ there is also the fact for the ISDN sllhst~riher line that SURS~ ; SHEET

radio transmission o~,c~lnes dis~ance limitations which arise due to attenuation problems in transmission over wires. Furthermore, limita~ions of distance due to transit time problems are o~co~e by radio transmission, since the SO int~rf~ce is not used for radio transmission.

A concrete enibodiment of the ill~ntion is les~ribe~l wi~h refc~ ce to the ISDN tvvo-vnre s~lb~i~r line with a UKO in~rf~. The principles of the solution, hon,~l.~, are valid for all other ISDN two-wire ~hs~nher lines with U interfaoes ;f it is adapted to the adequate signals used in them.

Details of the invendon are f~er ~ 1 wi~ the aid of the cirwmstances ~ ~ in ~he d~awil~gs.
Fig. 1 shows ~he prirleirle of the conr,c-tiQn of ISDN sllbs~ribers by radio;
- Fig. 2 the s~n~l~rd ~ro~ ce of thewalGe-up pr~ u~e for an incoming call;
Fig. 3 the m~if;~ ~Ço~lnanoe of the wake-up prooe~ re for an incoming call;
Fig. 4 the fl~w diagram of the base station of an ISDN-DAL
~ystem;
Fig. 5 the standar~ wake-up ~ ure for an inGoming call jnt~ltl-lin~ display of the IOM int~ace;
Fig. 6 the ma~ifi~ walGe-up ~ .~ upon an incoming call in~luding ~lisplzy of t~e IOM ;n~f . r~ce;
Fig. 7 the ~.~i~ ~iagr~nl of the base st~ of an ISDN-DAI.
system upon int~ Lion ;nto the IOM il~te~ r~e according to Figu~e 6;
Fig. 8 the ci~cuit ~ of a s~bscril~r tenninal of an ISDN-~)AL
s~s~ upon intervention into the SO interf~ce;
Fig. 9 the drcuit diagram of a sl~hs~ nber tc~nullal of an ISDN-DAL
~ystem upon intervention into the IOM interf~re;
Fig. 10 the dat~ frame for radio co~ununication in an ISDN-DAL
s~stem.

It is another important aim of the invention to provide for a high frequency _5_ SUBSTITUTE SHEET

- ~163888 economy of the radio transmission :~ys~ . This requirement has a high priority since the net bit rate of the ISDN sllhs~her line, at (Bl + B2 ~
D) = 144 l~bit/s, no matter how the channel is formed, results in vnde-band radio channels. -This requirement is met by maldng the number of radio channelssubstantially lower than the number of r~dio s ~hs~r hers, and the ratio must be made vaxiable in order to ~nu~ adaptation to different traffic levels acco~ g to the s1lbsrriber stmcture.
~or this purpose a solution is used in which the ISDN two-wire s~lbs~riher line be ~ line t~llu~lation (Ll~) in the ISDN c~nu~wl~ication and ne-wolk t~n illation (N I~) at ~e sl~ riher's is dh~ided into two pa~-s by the use of an illt~ te gen~t~ (ZW~), and in the ZWR-NT part the wired t~nc~ sl~n is replaGed l~y radio tr~n~;~ion. I~c ZW~ is a component of the base station (BS) of the local radio oell and the NT a component of the s~ r termir~ . Both are so made up that, when an activate request (PH ACIIVATE REQUEST) is ~S~It~ the assignment of a ooln~ tion channel [is p~rc . .~ ?l wi~ the waiting and monitoring period for the activation of the ISDN two-wire s~lbs~riber line.

~est W~ys of F.~nllol1yiT~g ~e l..~ ion.
The schematic diagram of a connection made to a s~bs~ih~or is roIlt~ined in Figure 1. The diagram abstracts from all sets of units w~ich are not functionally involved in a radio conrlerti~n.

The U~60 sllhs~rih~r connection 1.1 created by the ISDN-TVSt is made to a channel group of the base station 1.2, which consists of a UK0 repeater (ZWR) 1.3 and the transmit group 1.4 and ~;v~ group 1.5. The U,~D
repeater is conventionally constructed with a U~ao transmitter 1.6, hybrid 1.7, and two IEC-T circuits connected through an IOM int~rface. The coupling of the U~ epeater to the rad~o system is made to separate downstream and ~l~s~am lines, omitting the hybrid. The xadio system can, if neeeSs~ also ~~ groups for code c~l-v~ion, insertion of S~ u l~s SEIEET

~-` 2163888 redund~ncy for e~ror ~lçtection and error ooll~cl;~n, and ~y~ographic processing of the signal.
l'he sllbs~her radio tw~ al 1.10 (see Fig. 1) ~ncic~c of the r~iving gxoup 1.12 and the tr~ns ~ g group 1.13 which are coupled to sep~r~te downstream and u~s~am L;nes, o~ ;ng the hybrid, to a ne~ k termination (N'I') 1.11. The NT is c~n~ qlly con~ l of an IEC-T
circuit in the NT mode 1.14 and ciralit SBC or SBC~ 1.15, w~ich are connected through an IOM int~ce, and an S0 ~ans~o,~ f 1.16. The subscriber radio tc~uullal yi~lts an S0 int~r~ 1.17 at its OU~.lt.
A design of this kind can be wired only as a fixed line without additional measures, w~ich would require a radio ~hannel for each radio stlbs~ rihPr, but it had to be a ~oided as far as the aims are r~n~rn~, To achie~e the esta~lished aim it is n~c~ to ~llo~te a free radio ~hannel for every call request (always ~1~1 to he~einafter as radio æn~ wi~ ). The con~ unication intanal to the ~y~n that is ~i~rcd for radio service switc~ing be~l the channel ocln~nent of the base sy~ and the 5llhs~riher radio telminal, and the operation of st-hs~nh~ tf~hing units, transmitting and receiving units, etc, calls for a finite time ~ich, according to the invention, has tO be ins~ed into the wal~-up pr~erlllre of the UE~0 circuit such that it is not thereby impa~red and can be p~Çolllled on-line after the wal~e-up proc~,lule.

This is a~hieved acsording to the i~ ion for an incoming call for a radio sl~bsrriher (activation by the L~ ne c~ ication) by d~ying 1:he INFO U2W signa1s. The starting poin~ is ~he S~:1~3~ ~vllon of the wake-up procedure of the UKD section ~y the interm~li~te gen~r~tor (see ~ig. 2). As part of this pro~ re, after a PH-ACTIVATE R~QU~ST, the line termination (LT)2. 1 emits the wake-up signal INFO U~W 2.4 to the int~ te generator 2.2, whereupon acknowledgment is giv~n by the intermediate generator with INFO UlW 2.5. In the standard tinung, 5.31 ms after the emission of 2.4 staxts, the acknowledgment QE 2.6 is given.
QE 2.6 is recognized as being in good order if it takes place before the end of the wake-up repeat time Tu13 = 12 ms 2.7, which was s~L~1 at the beginning of the emission of 2.4 in the line h....;l.~l LT. This signifies that SU3~ u.-~i S~IEET

QE2.6 may be dela~ed by no more than 6.68 ms from the standard timing (wa~ting period) uithout any disturbance of the wake-up procedure. The same conditions as for the U~O section LT-ZWR apply to the U~ section ZWR-NT 2.3. Paralld to the .~mics;oI~ of-the a<~knowl~gJn~nt 2.5 to the LT ~he ZWR tr~n~nits to the NT the activation call INFO U2W 2.8 and simultaneously sta~ts the wa~ up re~at time 'ru 13 = 12 ms 2.11. Thus the a~ f ,~t INFO UlW 2.9 of dle NT and Q2.10 in the ZWR
can be del~ l (w~ , ~no~l) by a ~ in~ of 6.68 ms from the standard timing also on the secon~ .U~ao see ion ZWR- NTwithout any distur~ance of the activation of the U~6D se~ tion. The ~ waiting ~iods can be used t~ er or in~pçn~lPntly of one another.
Using the waiting p~n~s of the wal~-up p~ n~ results in the ~ro~ nce of the U~0 section co~r~ ing to Figure 3. The INPO
U2W 3.4 ~ J t~om the LT 3.1 (see Figure 3) is ~stc~l by a system of its own with a delay ~o the ~T input of the ZWR 3.2, and the INFO
U2W 3.6 gener~t~d by the ZWR is sentwith dela~ by a system of its own to the sPr ~nd U~a~ se~ion- At the moment 3.8 of the beglnning of this sending the radio coll-nulnication must be shut o~ so that 3.6 can be t~ans~l~l to the NT 3.3 and the activation of the U~60 section can be continued ~ly.
These functions a~e ~ro~ ed in the ~ase s~ation by channel units 4.0 (see Figure 4), w~ich are ~-~so~:qt~l with each U~D s-~bs~ber corlner~i~n 4.1.
The inconung line signal is divided in a ~ qtion hybrid 4.2 into a downsL~ and an ~am. Int~ the downsL~ line a delay ~y~m 4.3 and 4~ is inserted at ~he input and OU4nl~ of the ZWR 4.4 and ar~
controlled by the ~h~nnel c~ oller 4.6. When ~he U~0 section is in the deac~iv~ state the delay ~l s 4.3 and 4.5 cons~itute an inte~uption of the line. Awake-up signal entering OII the up side of the delay Sy~

4.3 is recognized by the channel controller 4.6, whi~h thc.e.~ starts the process of the radio colful~unication, and after the ~ um pe~ussible delay or after the radio communication is complete it feeds the same wake-up signal on the down side of the delay sys~n and then cancels the d;vision of the line (on this, see also Figure 3 and the ~esc~irtion corresponding to Figure 3). If after the n~ n allowable delay time of SlJBS l 1~1 u ~i SHEET

~

the delay ~ystem 4.3 the radio c~llull~nication is not yet corn~l~te~, the same process can be ~ated at the deL~y system 4~. The base station is completed, in a manner known in mobile telephone technolo~y, by a radio communicaffon C(~lY~ el 4.7 which controls ~ll channel ur~its 4.0 and the switching JnAt~CeS of the tr~n-~ission direc~on 4.9 and l~cep~ion direction 4.10 through a oentral bus 4.8. T~mis~ion units 4.11 and ~;Vi~lg units 4.12, w~ h o~atÆ through a switching nc~wu~k 4.13 on a co~unon antenna 4.14, a~ ed to the swit~g mq~iY units 4.12.
A~cording to ~e i~v~-ion, in anothe~variant PmkP~i~nent, when a call a~n~es for a xadio s~ r (activation ~r the tdephonc cx~ u~ t~on) the time need~ for the radio conne~;on is obt~ined thxough the delayed transfP~ of the a_Liva~ion request be~ the LT-side input circuit and s.~bs~ r-side output arcuit of the ZWR. For ~his purpose, one must first consider the st~n~?rd ~ I;on of the activation of the Uxr, se~isn with ZWR as represented in Figure 5. Comprised in ~is ~Yer-ltion is that, after ently of an INFO U2W 5.4 ~m the line t~ stion 5.1 the input circuit 5.5 of the ZWR 5.2 sends the Info RSYD 5.6 to the OULy~lL c~c~ 5.7.
The output C,l~it 5.7 acknowledges with the Info ARU 5.8 and b~
e~I~iLLLIlg Info U2W 5.9 initiates the ac8vation of the s~on-l sPc~iQn of ZWR 5.1 to the NT 5.3. The ~cchange of the signals ARN 5.10 and AIU
5.1 1 completes the activatdon through the IOM hltc- r~ of ZWR 5.12.
For the e~odiment of the invention, an inte~c~ pr~essor UPC 6.14 is inserted into the IOM in~ ace as ~ es~lted in Figure 6 and the IOM
interf~e is thus dn~ided into two sections 6.12 and 6.13. After receiving an IN~O U2W 6.4 f~om the line t~ don 6.1, the input ~;~cuit of the ZWR 6.2 en~its the Info RSYD 6.6, whi~h is ~o~l by the UPC. The UPC 6.14 acknowledges ~nth the signal ARU 6.8 and tpn~rnits the activation instruction ~RX 6.16 to the radio Swit~ng system RPX 6.15.
After the radio connection is made to the desired sul~s~riher Iadio ~c~;ver the RP~ 6.15 sends the ac~vation acknowledgement AIX 6.17 is sent to ~e UPC. Not until then does the UPC 6.14 send the signa~ RSYD 6.18 delayed to the output arcuit 6.7 of ZWR 6.2. The OutpUt circuit 6.7 of ZWR 6.2 ac~nowledges ~nth the info A~U 6.19 and now, by issuing the INFO U2W 6.9, it acLi~at~s the second section of the ZWR 6.2 to NT 6.3.
g SUBS ~ ~ SEIEET

- Z1~8888 This procedure runs over the already activated radio connection to the desired s~lbs~ riher te~minal. After the Info A~U 6.19 is received, UPC 6.14 also sends the Info ARN 6.20 delayed to the output Cif~l~it 6.7 of the ZVVR

6.2. From this moment VPC 6.14 switches the connect~on ~L~v~l input ci~ 6.5 and Ou~Ut ara~it 6.7 of ZWR 6.2 to tr~nsr~rent and all subsequerlt si~ e translu,-~l ~nthout v~ on or delay.
These variants of the in~ ion are ~ise made in the base S~tion ~r channel ~lll~llents 7.1 (see Fi~e 7), w~ich are ~ l with each Ul60 5~lh5~r oonnection 7.2. It is an ~l~nt fca~ that in ZWR 73 the IOM bus IJCl ~ the cir~ts IEC 7.4 and EC 7.5 is enffrely or partially interrupced and bus poffion 7.6 of IEC 7.4 as well as bus portion 7.8 of IEC 7.5 are connecte~l ea~h to the channel controller ~RPX 7.9. The line signal ani~nng f~om the LT is di~nded in a ~ ination hybrid 7.10 into downs~ and u~h~u and and the latter are r~nnect~ di~c~ to IEC

7.4. When an activation request of the LT (INFO U2W) is ~C~It7 the activation request i~le~ from t~e IEC 7.4 thnbugh the IOM in~r~ 7.6 is reco~ed by the ~hannd a)~ oller/~PX 7.9 which t~l~U~ll starts the process of radio ~ l~ing (see also Figure 6 and the lcs~ on rdating thereto). After s~ c~s-crul radio ~wi~ g, the ~hannel co,lLIvller transfers the activation request through the IOM in~rf~e 7.8 for the secQn~ UE ~
section tO the IEC 7.5. Thc base station is c~ kt~d in a manner known in mobile telcphone ~nology and identical to the .~ese~ tion in Figure 4 and ~~ onding desc~i~(ion.
According to the invention, in the case of an OUL~Oil~g call by a radio subs~ riher (activation request b~ al equipment) thc time for the ~adio sw~hing is achieved ~y the delay of the signal INFO S 1. The starting point is the standard ~ ;on of the wake-up procedl-re of the S0 sec~ion which sets no time limit for the emission of the acknowledgement INFO S2 by the NT after ~etection of the INFO S1 (~c~t for the total supervision ~ime Ts1 = 30 ... 35 s for completion of the activation in the TE with PH-ACI I~ATE ~NDIGATION).
The ~mplementation takcs place in the sllbs~her's radio apparatus (see Figure 8), since in the NT 8.2 be~en the S0 transro~ll~ 8.3 and ci~cuit SU8~-1 1'1'U 1~; SEIEET

` - 21~8888 SBC (SBC~) 8.5 in the upstream branch a switch element 8.4 is disposed which can be operated by the link controller 8.7 through a control line. The link controllOE 8.7 is connected to the ups~n br~n~ beLw.,e.ll So transro~ ~ 8.3 and switch means 8.4. The switch means 8.4 in the deactivated state of the SO section constitutcs an interruption of the conduction train. Asignal INFO Sl cntering on the downside of the switch means 8.4 is dete~3 by the link controller 8.7 w~ich then starts the p~oess of radio ~..;L~I~ing and, afta the radio ~vit~ing is finis~d, switches the switch ~o~n~ 8.4 to ONn so that INFO Sl is applied to the NT and ir~iti~es the activation of the ISDN s~ connertior In another va~ialnt of the il~,tion, the same problem is solved in the s-lbs~ riber radio t~lninal as well (see Figure 9). ~n ~ o,~nt feature is that in NT 9.2 the IOM bus ~ the ~its SBC (SB~ 9.4 and IEC
9.7 is w~o~ or partially interrupted and the bus portion 9.5 of the SBC
9.4 as wel~ he bus por~ion EC 9.7 are corme~e~l each to ~he l~nk con~xoller 9.8. The S0 signal 9.1 is swit~hed t~wgh an SO transrull~ 93 to the circl~it SBC (SBCX) 9.4 of NT 9.2. When an ac8~ration request from a TE (INFO S l) is p esent, the ac8vation request ~i~l by the SBC
(SBC~ 9.4 through the IOM int~ e 9.5 is 1~tce~c~1 by the link controller 9.8 w~ich then starts the ~lu~SS of radio swi~lung. After s~1cccssrul radio swit~ g the ac~dvation request is transrc~i to the circuit IEC 9.7 through the IOM int~e 9.6, thereby starting the activation of the ISD~ ~1hs~ ~r ~onnection.
In order to achieve the most crræ~ivc possible uti~ation of the available transmission ~andwidth, an independent radio channel for operation, organization and control p~poses is dispensed with, in aordanGe with claim 7. ~11 of the corlul~lLc and il~ro~u,ation required for this purpose a~e translni~e~ in the free radio channels. To reduce complications, data rates, block lengths and synchronization words are chosen to be identical with the par~cular U int~ c~ standard. To make it possible for a radio channel to be recogni7~ as free in the s~lbsrnh~r ~ al, the synchronizing words are inserted into the transrniccion in ~ rse o~der (beginning and end in~led), so that it can be <:learly disting-ich~rl whether radio ~wi~li~ng or ISDN tran~cmi.cc;on is involved. A data frame SUB~ U-l~; S~IEET

- 21S8~

corresponding to these sperifi~tions is rep~sented in Figure 10. The data frame begins with 5 ternary o" steps as lead~r. This is followed by 11 tOEnar~r steps of synchronizing word 10.2. An 11-place Barker code is used as the syn~ron~i~ng word which is transmitted from the BS to the radio sllbs~ nh~r in the fonn of:
+ +~+ + +.
In the direction away from the s~bsrrih~, the transmission is in the form:
+ + + + +

In ISDN tr~n~mission the bar Godes are inserted backwards into the data streams. The ~ in this case is of no in~ nce, sinoe the lCI~Vi lg arcwts ~.~ l an at~ ic polarity~ct~c~o, . 16 ternary steps follow, the command part 10.3, sin~ BCH (B.4) ~ng 8 data bits can contain 256 ncls. Another 16 tema~y steps, address part 10.4, followwhich in BCH (8.4) coding can contain 8 data bits equal to 256 addl~ss~s. The remaining 72 ternary steps 10.5 are used as the data part and on the same basis as in 10.3 and 104 can transmit 36 data bits. As an ex~mple, free/busy messages for 36 channels can be contained in it as one-bit information.
Prom the technical radio r~ ..ication point of view, it is pr~c~;~l todistribute inactive s~ r radio t~~ als evenly to the free ~adio channels, in order to have as few ~wilChi~lg V~ AI;ons as possible in a desired connection set-up and reduce the probability of a r~ndom signal hazard. This prohl~-n is solved in that the s~tl~ih~r radio ~ . I~;r~l contain a r~rldom generator w~ich before any ~hannel change lPt~ ines an evenly distributed i~ ;~ random number, which can l~ . een 1 and 16, for example, depending on the size of the ~y~", and which tells the num~er of the free cham~el that is to be used in yclical sc~nning.
The channel changes are aul~n~atically ~ro.llled by the s~1bs~riber radio terminal at variable time intervals, also OII instructions from the radio switching system, or if the channel ~ y in use is assigned to another sllbs~riber tenninal for active use.
When a call ar~ives the radio switching a~s~ allocates a free radio channel SUBSTITUTE S~IEET

- ~16888~

to the sllhs~her, ac~or~lh~g to claim 8, by t~an~ g an add~sed inquiry into all free radio channds. This is necess~y if the~e is no a pdori knowledge in the radio ~wi~l~ing sys~ regarding the radio channel occupied at that time by the slJbs~nher radio t~ ;Qql If this inquiry is acknowledged ~y the s1~bserib~r radio te~
acknowled~ t is sen~ which ~ IllCP-C the radio swi~lling system to allocate to the s~1hs~riher the radio charu~el cu~ tlr used by the s~lhsrriber radio ~ illal, and to set up a connection to the called s~bs~ber, so that there will be no fur*ler losses of time due to channd changing etc. It is on~y on ~c~ nt of time-n~r~lhl pr<resses or signal hazards that departures from this proe~ can oacur, in whi~h case a dis~ lglernent is p~ro~d in that, after a radio ~hannel has been ~llo~A to a specific sll1osrrih~Pr radio ~nal. all other ~lhçrrihPr radio t~al leave t}~s radio channPI.
Inquiries and acknowledg~~ s are ~ontrolled nt~ally by the rad~o :~WitCIling system on the master-slave princip~e.
When a s~.hs~riber tries to ma~e a call (ouLgoing call~, a request to that effect is ~rc,n~ed by the s~1bs~ r's radio apparatus in the radio ~hannel that is free at that m~ If this call is s1lc( ~s-~l11y ~ this radio channel, a~,ding to c~laim 7, releases the base station to the s~-hs~riher radio ~ll~irlal for active ISDN information t~n~n;ttal. The pr~ r~
and rrst~ ons of this ~ clu~e are as ~ nh~l above. To ~tail1 a time-flPfine~ ~eaction of the s~hs~nhP~r ~~ lal, the radio switch~ng ~~
ernits f~ee calls to which answ~r can be made ~y a ~11 a~np~ from a subsrnl~r ~nal. If a snhst~r~her t~ lal is not assigned the rad~o channel after the call aL~l~t is made, according to ~laim 10 an evenly distributed random illt~Y number is genelat~ w~ich indicates the ordinal number of ~he following free call of the radio switching system that is to be used for ano~her transmission of a call attempt, and according~ repeats the call aL~t:mp~.
This process assures that, on the basis of a possihl~ si~nal hazard due to simultaneous call ~ I(C ~ .Ls by several snhscrih~rs a disentanglement of the S~BS`~ l'l'U 1 ~; SHEET

individual s~lb~iher calls will be made.
If an overlapping of ~equirements regarding incQming and outgoing traffic for two dirÇe~ s~lhs~nher terrninals o~curs wi~in a radio c~hannel, this does not result in traffic hazards, sinoe in this case ~nr~h~r, free radio charulel is allocatel to one of thc sllhsr~ r t- "~ in q~ion (soe claim 11). The p~c~l~e of ~ ~ to another free channd can result in losses, ~s~qlly in the case of the oae~l~.ce of relativel~ high trafflc and relati~el~r great numbers of c~nels, due to the fact that t~e s~lbs~rihPr radio ~llunals requ;re an appre~is~le amount of time to sear~ for free radio channels if the search ~ le invoh~es the s~nnin~ of all of the r~dio ~els. To fol~s~all this, the radio ~ g D~S~n iS cor ~n~cly trans,.u~ .g ~ terl inrf~ n on free f~dS. ~'~o~c~uently the subscriber radio t~ll~ als arc able to ~t~ e w~at the new channel is without a se~, thus r~duang the te~ical ~...~ ni~ti~n bsses.
(1) PCT/EP91/~)0853 (~ntPn~ ns~ hli~tionN~mh~rwo 9l/l8483 (2) Mandel, Gunter; K~C1R~, Klaus; ~DAl in analog7~ rer Technikn Elek~ronik Berlin 42 11992) 4 (3) Leipold, Pcter: DAL ~ ed~llik im Teilne~unor~ns~ 3bereich"
NTZ 45 (1992) 4 (4) Buckingham, Colin; Wolterink, Gé K~ein, ~k~ r~,, Dag; A Business Cordless PAB~ Telephone System on 800 MHz based on the DECI`
Technology, IEEl; Comm1mi~tions Ma~e, Janua~y l99l The following abL~ tions are terms from user docurnentation, t~pe names and ~stered ~ nnarks of the Siemens ~..lr~.ly;
IOM ISDN Oriented Modular Int.orf~c~
IOM-l ISDN Oriented Modular In~ ce Version 1 ~OM-2 ISDN Oriented Modular Int~ ce Version 2 ~SYD ~e~ynchronizing Indication Downstream ~ARU Act~ration Request Uys~re~n ARN Activa~ion Request no I,oop AIU A~tivation Indication Upstream IEC ISDN Echocanoellation Circuit -1~
SlJBS~ ul~; SE~EET

- 2168~88 IEC-T ISDN Echocan~ll~tion Circuit IEC-TD ISDN E~hocancellation Ciralit / Digital Circuit IEC-TA ISDN Echo~nc~ tion Cir~uit l Analog Circuit SBC S-Bus Int~ ce Cirwit ~~
SBCX S-Bus In~ cr Ciralit, F.Yt~n~let1 In-ln~t~ql U~;li~r The invention is incl~ lly useful in the teleoo~ ication industry.

SUBSTITUI'E SHEE~

Claims

Claims:

1. Local ISDN transmission system which is organized as a local radio cell, consisting of a central fixed radio station and a plurality of decentral subscriber radio terminals and is connected to the subscriber ports (ISDN base connections) of a local switching center, store-and-forward center or private branch exchange, and provides the subscribers with access to the public ISDN telephone system through an So interface by the use of wireless transmission, and in which, for the operation of the system in the case of a number of subscribers greater than the number of the duplex radio channels (hereinafter called communication channels) in use, a radio communication system is present in a central fixed radio station (base station BS) which, in the event of an activation request (PH-ACTIVATE REQUEST) opens to the subscriber radio terminal (TL), by means of a special radio communication process, any one of the available and free communication channels for the communication, characterized in that the net bit rate (B1 + B2 + D) of the ISDN subscriber terminal is transmitted unrestricted through the radio channel and the So interface constitutes an unrestricted interface, that the ISDN two-wire subscriber connection line between Line Termination (LT) in the ISDN switching and Network Termination (NT) is divided at the subscriber by the use of an intermediate generator (ZWR) into two sections, and in section ZWR - NT the wire-connected transmission is replaced by radio transmission, the intermediate generator (ZWR) being a component of the base station (BS) of the local radio cell and of the network termination (NT) component of the subscriber radio terminal (TL) and both being so integrated that, upon the occurrence of an activation request (PH-ACTIVATE
REQUEST) the allocation of an information channel is performed within the waiting and monitoring periods for the activation of the ISDN two-wire subscriber connecting line, and that a system is provided which, in the presence of an activation request, delays its forwarding by a delay period which makes it possible to switch an information channel for the called subscriber and activate radio systems of the subscriber radio terminal (TL).

2. Local ISDN transmission system according to claim 1, characterized in that in the base station (BS) for making a radio connection for an incoming call for a radio subscriber, a system (4.3, Fig. 4) is present at the switching-side (LT-side) input of the intermediate generator (ZWR) (4.3, Fig. 4) which delays the wake-up call issuing from the switching point in the direction of the intermediate generator (ZWR) and/or a system (4.5, Fig. 4) is present on the subscriber-side (NT-side) output of the intermediate generator (ZWR) which delays the wake-up call (3.6, Fig.
4) issuing from the intermediate generator (ZWR) in the NT direction, and that these delay times individually or together are used in order to connect an information channel for the called subscriber and activate the radio system of the subscriber's radio terminal (TL).

3. Local ISDN transmission system according to claim 1, characterized in that, in another variant, in the base station (BS) for the establishment of a radio connection upon an incoming call for a radio subscriber, there is inserted into the interface between the input circuit (5.5/6.5) on the LT side and the output circuit (5.7/6.7) of the intermediate generator (ZWR) on the subscriber side a system (6.14) is inserted which delays the transfer of the activate request (6.6) to the output circuit (6.7), and that this delay time is used in order to connect an information channel for the called subscriber and activate the radio systems of the subscriber radio terminal.

4. Local ISDN transmission system according to claim 1, characterized in that, for the establishment of a radio connection upon an outgoing call of a radio subscriber, there is present in the subscriber radio terminal at the So connection (8.1) of the network termination (NT) (8.2), a system which delays the activation request (INFOS1) of a connected terminal, and that this delay time is used in order to connect the called subscriber and activate the radio systems (8.8) of the subscriber radio terminal (TL).

5. Local ISDN transmission system according to claim 1, characterized in that, in another variant of the establishment of the radio connection in the case of an outgoing call of a radio subscriber in the subscriber radio terminal a system is inserted into the interface between the input circuit (9.4) on the subscriber side and the output circuit (9.7) of the network termination (NT) on the switching side, which delays the transfer of the activate request of a connected end terminal, and that this delay time is used for the purpose of connecting an information channel for the called subscriber and activating the radio systems of the subscriber radio terminal.

6. Local ISDN transmission system according to Claims 1, 2, 3, 4 and 5, characterized in that, after the delayed transmission of the activate requests the radio transmission system is connected transparent and on-line into the transmission path between the subscriber's switching and end terminal.

7. Local ISDN transmission system according to claim 1, characterized in that, for the radio switching, no special organization channel is used, but a distributed switching is performed in which switching, organizational and signaling procedures are performed in all free channels, and for this purpose the inactive subscriber radio terminals position themselves automatically in one of the free information channels and a uniform distribution of the subscriber radio terminals to the free information channels is assured by the fact that, prior to any channel change, a random whole number n (e.g., 1 n 16) is determined which indicates the ordinal number of the free channel that is to be used in cyclical scanning, and that channel changes are allocated automatically at time intervals upon instruction from the radio switching system of the base station (BS), or whether the channel actually in use is assigned to another subscriber radio terminal for active use.

8. Local ISDN transmission system according to claims 1 and 7, characterized in that the radio switching system of the base station (BS), upon an incoming call for a radio subscriber, issues an addressed query to all free channels and allocates to the subscriber terminal, on the basis of his acknowledgement, the information channel in which, as a rule, it is currently located.

9. Local ISDN transmission system according to claims 1 and 7, characterized in that the radio switching system of the base station (BS) sends "free call" commands into the free channels if no other switching and signaling procedures are to be performed, which in the case of an activate request from a radio subscriber (activate request from a connected terminal device is present) permit the subscriber radio system to issue the "activate request" command, and the base station (BS) allocates to the subscriber radio terminal, at its request, as a rule, the information channel in which it is currently located, for active use.

10. Local ISDN transmission system according to claims 1, 7 and 9, characterized in that, in the subscriber radio terminal, after a call request which is not acknowledged by the radio switching system, a random integer n (e.g., 1 n 16) is determined, which indicates the ordinal number of the following free call of the radio switching system that is to be used for a repeated transmission of an activate request.

11. Local ISDN transmission system according to claims 1, 7, 8 and 9, characterized in that, in case of the simultaneous occurrence of incoming and outgoing activate requests for two subscriber radio terminals in the same information channel, or the simultaneous occurrence of outgoing activate requests from two subscriber radio terminals in the same information channel, the radio switching system can allocate to one of the subscriber terminals another free information channel for active use.

12. Local ISDN transmission system according to claims 1, 6 and 7, characterized in that, for data transmission for the purpose of radio switching, frame length, transmission speed and synchronizing word identical to the ISDN transmission can be used on the ISDN two-wire subscriber connection line, and that a clear distinction of transmissions for radio switching and ISDN transmissions is achieved by the fact that the synchronizing word (10.2) in transmissions for radio switching is inserted into the transmission in reverse (beginning and end exchanged).

13. Local ISDN transmission system according to claims 1 and 7, characterized in that the radio switching system, in the case of data transmission for the purpose of radio switching in the data part (10.5) of the data frame, transmits the updated information through free channels, so that subscriber radio terminals can specify another target channel for the purpose of channel changing without a searching procedure.