CA2120031A1 - Pstn architecture for video-on-demand services - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A public switched telephone network (PSTN) provides digital video signals from a video information provider to one or more of a plurality of subscriber premises. A subscriber uses either a standard telephone instrument over the PSTN or a dedicated control device over an ISDN packet network to order video programming. The request is transmitted to a designated video information provider and digital transmission connectivity is established between the video information provider and the central office serving the subscriber.
Connectivity between the central office and subscriber is provided by asymmetrical digital subscriber line interface units over a local loop. The interface units frequency multiplex digital video information with voice information to the subscriber and support transmission of a reverse control channel from the subscriber to the central office for transmission on the ISDN packet data network back to the video information provider. The interfaces also allow base band signalling and audio between the central office and the subscriber for conventional telephone instrument connectivity.

Description

~VO93/~66')~ PCr/llS92/06X~-~2V~31 PSTN ARCHITECTURE FQR VIDEO-ON-DEMAND SERVICES

Technical Fleld The invention relates to a Public Swltched Telephone Network (PSTN) configuration and, more partlcularly, to a combined voice and data switching configuration and method for supplying connectivity from a remote or collocated video provider to a local subscriber over a PSTN.

Backqround Art Distribution of full motion video data has evolved from the early days of television broadcasting to meet viewer demand. Earliest video distribution was by point-to-point wiring between a camera and a video monitor. This wAs followed shortly thereafter by the proliferation of television broadcast stations transmitting fixed schedules of programming over the public air wavey. In the 1960s, Community ~ntenna Television (CATV) sy~tems were established, initially to provide off-air television signal~ to viewers in broadcast reception fringe areas. Under FCC

2~ regulation, the CATV industry was required to provide local access and original programming in addition to required off-air broadcast signal distribution. In response to the requirement for further televlsion programming, .~everal sources of cable network programming were established. ~ecause of the wide :

UO93/06697 l'Cr/US92/06X~I
2120~)3 ~

bandWidt~ VA I ~ on cable television ~sy~tem~, additional ~hannels were made available for tl~e new programmina ~w~ver, the programming wa~s generally prescheduled ~ith the viewer left to tune into the designated channel at the appointed time to view a particular proqram.
To increa~e revenue6, cable television systems initiated ilstrlbution of premlum channel6 viewable only by ciub~criberci ~laving appropriate descramblers.
I0 The descrambler apparatus would receive premium channels and dei~cramble the video and audio information to supply an OtltpUt signal capable of reception on a ~tandard television set. Pay per view programs were later provided. These programs included recently lS released movi~, live concert~ and popular sporting events. Sub~crlbers wishing to view a pay-per-view program would place nn order wlth the cable operator.
In response, at the designated time, the subscriber~s descrambler would be activated to permit viewing of the pay per view ~roqramming. However, the subscriber was re~tricted to vlewing the programming at the scheduled tlme, there w~s no provision for providin~ programming to a ~ubscriher at a tlme and date speclfied by the ~ubscriber.
For example, ~essler et al., 4,755,872, describes an impulse pay-per-view system for use wlth a cable system having one-way addressiable converters. Each of several central offices in a metropolitan area provide ~utomatic Number Identification (~NI) information representing thP cable subscriber's phone number and the code representing the cable event to be viewed or cancelled. The data is sent a~ynchronously to a Telephone Communicatlon Unit (TCU) located at a central office. The TCU sends the data asynchronously to a ~093/()669~ PCrlll5~)2/06X~/

3 2 ~ 2 ~

rrelephene (ommunication Controller (TCC) located at a cable head end station. ~ system controller at the head end receives the data from each subscriber, locates a corresponding home terminal unit address, and performs other housekeeping actlvities. The controller then authorize~ the home terminal unit to receive and descramble the requested program.
In the early l9~0s, technological advances resulted in the proliferation of Video Cassette Recorders (VCn)~ thereby establishing a second channel for video programming distribution. Pre-recorded video programs were made available for sale and rental to VCR
owners. With a VCR, the viewer could select from many title~ available ~or sale and rental and could view the program when convenient. The VCR owner further had the capability to selectively view the programming using special functions of the vCR. Thus, the viewer could pau~e, fast forward, reverse and replay portions of the program at will. The penalty for this convenience, 2~ however, was the added inconvenience of maklng a trip to the local video sales and/or rental store, waiting ~or a popular ~ldeo program to become available for ~ale and/or rental, returning home to vlew i3 vldeo cassette, and the required trip back to the video store to return a rental tape.
To combine the benefits of both cable and video cassette distribution of programming, some cable operators have proposed programming-on-demand cable systems. For example, Walter, 4,506,387, describes a 3~ programming-on-demand cable system which allows a user to select a video program from a llbrary of programs.
The user transmits the program request over a dedicated fiber optic control cable to a central data station.
The video program is then transmitted at a high, non-~ 93/0669~ 1~C~/US')2/0~7 4 2 ~ 2 ~ a 3 1 real-time rate nver a fiber optic line network to a data receivin~ ~tation at the user's location. ~ data receiving station then converts the received optical data back to ~lectrical data and stores it for subsequent real time transmission to the user~s television set.
Popock et al., 5,014,125, describes an interactive televislon system for transmission of still frame video images and accompanying audio over a television system such a~ a cable network. ~ telephone network is used to establish a two-way communlcatlon path between a vlewer~s locatlon and a central location. Information pertaining to the viewer, as well as commands related to the viewer selectlons for presentations and other data, are transmitted to the central location from a terminal at the viewer site by means of a telephone connectlon. The same telephone connection is used to transmit audlo inform~tion from the central location to the viewer~s terminal. The audlo is combined with video lnformation transmltted over another medium, such .:
aa a dedicated di~tribution cable, by the user terminal.
Clark et al., 4,761,6~4, describes a telephone access di~play system uslng a program data processor to operate a cable ~.elevision system wherein a subscriber selects video information to be di~played on a common cable channel. The subscriber accesses a data proce~sor using a telephone and selects video information to be broadcast over the cable system by inputting a dlgital code using the telephone touch tone pad. The data processor processes the signal generated, retrieves the video information from memory and places it in a queue to be broadcast simultaneously to all subscribers.
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W~9~ fi69~ l'Crl~!S~2/(~fi~
2~ 31 Gordon et al., 4,763,191, de~cribes dial-up telephon~ lletwork equipment for requesting an identified ~election. ~ caller dials a 800~ dial-a-view number for placing an order for a particular selection With a telephone network. Local and toll swltchlng o~fl~e~ acce~s a centralized data bafie to provide routln~ instructions to network services equipment whlch Acknowledge the request and provide the request to ~able television distribution equipment.
~NI is orwarde~ along with a request to the program vendor equlpment. The vendor equipment 6upplies the requested pro~rammln~ to the calling customer over a local cable company via an addressable descrambler at the calling customer s television.
Mon~low et al., 4,995,078, describes a television broadcast system u~ing dedicated cables for real-time transmission of a viewer-chosen proqram at a viewer requested time to the requesting viewer~s television receiver. ~ vlewer telephones a central location to reque~t a partlcular program and viewing time.
Re~pectlve customer servlce repre~entatlves answer the lncomlng calls and enter the informatlon into a ~cheduling computer. ~lternatlvely, an auto dial device can be used to request a program, the request being made dlrectly to a volce response system. If the chosen movle hi3s not yet been scheduled at the requested time, an appropriate cable channel is selected by the system and an operator activates a corresponding vCR to transmit the program at the requested tlme.
Lambert, 4,381,522, discloses a system in which a viewer can telephone a cable company central location and select a video program to be broadcast over one of the channels of a cable television system. ~ computer ~ 09~ 669' PCT/~'S92/068~/
6 2~2~

schedules the ~elected program, ~ransmits the program at the sch~duled time, and separately transmits a directory o~ all the scheduled programs on a dedicated directory channel. The viewer monitors the directory channel to d~ter~ine when the requested recording is scheduled to be ~)roadcast over the cable, and then tunes to the channel indicated at the scheduled time to vlew the program.
~ dlsadvantage of programming-on-demand cable systems is the limlted number of dlfferent programs which can be simultaneously supplied to viewers due to the small number of unused cable channels available for distribution of ideo programming. With the increase of premium and ~ay-per-view video programming available to the cable system operator, fewer channels remain .
free for viewer selected programming use. Further, the subscriber must forego desirable VCR type control of the vldeo programmlng including pause, fast forward and rewind.
Telephone llnes have been suggested as an alternate means of video distributlon. Goodman et al., 5,010,399, de~crlbefl a video transmission ~ystem for dlstrlbutlng vldeo and control slgnals wlthln a residence uslng existlng telephone wirlng. By filtering, simultaneous transmission of video and control signals over active telephone linefi is possible without interference with telephone communications.
The patent includes an extensive discussion of problems as~ociated with the transmission of video signals over ordinary telephone wiring.
Kleinerman, 4,849,811, describes simultaneously sending audio and digitized single frames of video over standard telephone lines using ~inary Frequency Shift Keying (BFSR). ~ frame grabber is used to convert the ~'~93/Oh69~ 1'Cr/~lS9~ 68~7 2l2ao3~

imaqe to 3 ~tandard NTSC signal for di~play on a monito r .
Thus, ~hlle ~imultaneous real-time dlstribution of a relatively ~mall number of video programs i9 available over existing cable television systems, the capacity of the sy~tems is limited by the available number of vacant channels on the system. Further, limlted pro~r~mming cholce is offered by cable dlstribution method~ since many subscribers must watch a particular selectlon to ~ustify use of a dedicated channel for the ~ur~tion of the video program. Still further, cable ~ystem distribution of video programs provides minimal programming flexlbility on the part of the subscrlber, again dependent on channel ~ - -1~ availability. Flnally, no provilions are made to control the video in real tlme. Thus, the 6ubscriber i8 without standard VCR type controls of the program material.
In contrast to cable distribution, systems using the PSTN are often bandwidth limited, providing only still frame or Jideo conferencing capabilities.
~ecause the systems use the PSTN only for connectivity between 3ubscribers and/or between subscribers and Vldeo Informatlon Providers (VIPs), there is no capability for dynamic routing of digitized video without requiring dedicated leased, wide bandwidth circuits. The ~ystems al~o fail to provide vCR type functLonal control of the programming.
~ccordlngly, an ob~ect of the invention i8 to provide video programming on demand using components of the PSTN.
~ nother ob~ect of the invention i9 to provide ~ubscr~ber access to multiple sources of video programming over the PSTN.

~'()93/06697 l'CI/lJ~92/(~h~-~ 8 2~ 2~3t Still another ob~ect of the invention is to provide real-time subscriber control o~ video programming delivery ~ still further ob~ect of the invention is to provide a selected video program to a subscriber within a predetermined short processing interval after initiation of a request.

Dlsclosure of the Invention ~ccording to one aspect of the invention, a Public Switched Telephone Network (PSTN) provides video signals ~rom a Video Information Provider (VIP) to one of a plurality o~ subscrlber premises. Video data is stored and transmitted to the PSTN by the VIP in a compreseed dlgital format together with as~ociated compres~ed digital audio data. (As used herein, the phrase~ "video signal'~ and "vldeo data~' encompa6s combined dig~tal video and audio data signals unless otherwise noted.
Subscribers are provided with a subscriber interface unit including a local loop input node for receiving a multiplexed signal from a ~ubscriber local loop. ~ splitter separates the multlplexed signal into a video output signal and a ~ubscriber telephone instrument signa1, these output signals being provided at respective output nodes. Corresponding Central Offlce (CO) interfaces are provided at the CO end of respectlve subscriber loop nodes. The CO interfaces include inputs for receivlng video signals and a telephone instrument signal. The video and telephone instrument signals are combined by the CO interface and transmitted as a multiplexed signal to the respective sub~crlber loop.

~093/~669~ pcr/lls92lnfi~
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~ voice Cwitch receives telephone instrument signals from the ~:O interface and responds to telephone number data transmitted by the telephone instrument signal. In response to the telephone number, the switch provides ~udio signal connectivity fro~ the subscriber telephone local loop to a video gateway.
The voice cwitch also provides in-band telephone connectivity to other subscribers on the network for conventional telephone communications.
The video qateway is re~ponsive to A control signal received from the subscriber telephone instrument to ~rovide video scheduling data to a VIP.
~lso responsive to the video gateway, a Digital Cros6-connect System (~C5) receives video data fro~ the video provider and supplies the video data to selected CO interface~. Thu~, the video signal from the video provider is supplied to the subscriber over the DCS, the CO lnterface and ~ubscriber telephone local loop to the subscriber interface unit.
The output from the subscriber interface is provided to A decoder which performs decompression of the dlgitlzed vldeo signal and digital-to-analog converslon The decoder al~o decodes dlgitized audio included with the compressed video signal, converts the digitized audlo stgnal to an analog ~ignal and provides the output to the subscriber.
The subscriber interface further includes circuitry for transmitting digital command signals over the respectlve subscriber loop to the CO interface.
These digital command signals include video scheduling data to be provlded to the vldeo gateway. This data link from subscriber to CO interface also supports ~ubscriber control of video data supplied through the CO. Control data can al~o be provided to a data \-() 93/~)66'~ CI/~l~i92/(~6X 7 1() 2'120g3~ ~:

network for ~ransmlssion to the VIP in support of ~ -interactiv~ ~ideo siqnaling.
~ccor~inq t-~ another aspect of the invention, ~ -video ~toraae facilities provide buffering of video data receive~l from the VIP over the DCS. The video storage facilities are controllable to provide VCR type functions including pause, slow motion, forward and reverse ~earch, fast forward and rever~e under subscriber ~ontrol in response to dlgital command signals from the subscriber interface. These function~
are available by manual input at the subscriber -interface or remotely using a conventional infrared remote control unit.
~nother reature of the invention includes transmission nf caller identification information from the voice ~ltch to the video gateway. The video gateway translate~ the caller identlfication ~ -information to i~ network address and passes the address lnformatlon to the PSTN to establish dlgltal signal connectivity to the requesting caller and for billing purposes. The caller identification informatlon i9 :~
also transmltted to the VIP for identificatlon of the subscriber. The vlr equipment uses the subscriber~s data addres~ to establlsh a data link with the subscriber for interactlve video control.
~nother feature of the invention includes storage ;
of subscriber access data by the video scheduling unit.
The access data together with subscriber identification information, is used to define and limit system, VIP
and video program title access on a time of day basis.
Pre-programmed Personal Identification Numbers (PINs) are used by subscribers to override or redefine system access.
.

~'()93/~6697 ~'CI/IIS92/(~8~/
11 212~3~

~ ccording to another ob~ect of the invention, the local loop ~roviding connectivity betw~en the ~ubscriber pre~ise~ and the central office can be a standard tip and ring telephone pair, a coaxial cable or a fiber optic cable.
~ ccording to another a~pect of the invention, a PSTN provides ~:ideo data from a VIP to subscriber premises. The VIF provides a selectable output of dlgitlzed compressed video/audlo data programs including feature films, music videos, medical and commercial lmaging, video phone, video conferencing, court arraLgnment, di~tance loarning, surveillance vldeo, video games, home shopping and High Definition Television (I~DTV).
Subscriber loop tran~mi~sion facilities supply video data from a C0 location to the 6ubscriber premises and supply subscriber order data from the subscriber premises to the C0 location. The subscriber loop transmission facilities also carry telephone service signals be~ween the subscriber premises and the CO . ~ CO 9Wi tch receives the ~ubscriber order data from the subscrlber loop and supplie6 the order data to a video gateway. In re~ponse, the video gateway supplies vldeo routing data to a DCS which, in re~ponse, supplies video data from the VIP to the subscriber loop transmission facilities.
According to another feature of the invention, data transmission means are provided for transmitting subscriber order data to the VIP. The data transmission ~eans may include a packet data network.
The subscriber loop includes a local loop for providlng connectivity between the C0 and the subscriber premises. A central office interface tran~mits video data to the subscrlber premises on the WO9~/0669' 12 I'C~ S')2/(~68~, local loop ,~nd transmits sub~criber control data, ~
including order ~iata, ~rom the local loop to the video ~ :
gateway. ~ subscriber interface transmits subscriber order data to ~Ie ~O interface over the local loop and supplies video ~atA from the local loop to a video output node. The local loop may comprise a standard tip and ring telephone pair, a fiber optic cable or a coaxial cable.
~ccordlng to another feature of the lnverltio~l, the CO switch comprises a voice switch, with telephone instrument connectlvity to the switch provided between the CO and subscriber premises over the local loop. ~ :
packet data network is used to supply video control data from the ~ubscrlber local loop to the v~P for controlllng the video data. The system may further lnclude a video buffer which receives the video data from the DCS and, respon~ive to a vldeo control signal, supplies the vldeo data to the subscriber loop tr~nsmission means.
The video control data is provided over the subscriber loop transmission facilities from the subscriber premises to the video buffer to control the vldeo data supplied to the subscriber.
According ~o flnother feature of the invention, a ~.
video directory provides a video menu of video data available from the VIP to the subscriber in response to subscriber order data. To provide an alternative msthod of ordering video programming, a gateway receives order data from the C0 switch, and, in response, supplies (i) a voice reply signal to the voice switch and ~ii) video routing data to the DCS.
voice response unit also interfaces with the video gateway to provide scheduling information to the VIP.

, WO93/~6~97 I'C~ S92/~6~/
13 212~3~

The ~ubscriber loop transmission facilities include a rrequency multiplexor and demultiplexor for combining and ~eparating the (i) digital vi.deo and audio data ~nd ~ii) telephone service signals and S hybrid audio ~l~nals. The telephone service signals are exchanged t,etween the telephone instrument and CO
voice switch ~o provide standard dial-up telephone servlce over ~he loop in addition to transfer of dlgital video/audlo data to the subscriber. ~ video data expander is provided at the subscriber premises for convertlnq the compressed digitized video and audio data into analoa output signals.
The above and other ob~ects, features and advantages of ~he present invention will become apparent from ~he following description taken in con~unction with the accompanying drawings.

Brief DescriDtion of Drawina9 Figure I is an overall diagram showing video data flow ~rom a video information source to subscriber.
Figure 2 is a block diagram of a video-on-demand system according to the invention.
Flgure 3 i~ n functional diagram of a subscriber interface unit.
Flgure ~ is a spectrum diagram showing ;~
channelization of a local loop.
Figure 5 shows a typical in-the-home configuration providing video transported over a 1.544 M~PS channel overlaid with ~tandard telephone service signaling.
Flgure 6 is a block diagram of an asymmetrical dlgital subscriber line system providing simplex high-blt-rate access and POTS on a common copper loop.
Figure 7 is ~ logic dlagram of a gateway for acceptlng subscrlber video orders.

WO 93/06fi9' rCI /~l592/1)68~7 14 212~

Figure l~ is a block diagram of an alternate embodiment ~f A video-on-demand sy~tem using separate Tl and POTS loops.

Best Mode for Carrvinq out the Invention The video-~n-demand service platform shown in Figure 1 l1se~ ~xisting components of the Public Switched Telephone Network (PSTN). The system uses compression techniques to store video information for subsequent forwarding over interoffice facilitie~. The switching facilities are located in Central Offices (COs) servina residential customers or subscribers.
Loop electronic devices modify the transmi~sion characteristics of the local copper loop, to provide required enhancement to the PSTN and permit delivery of full motion video information.
~nalog video information i9 flrst converted to a dlgital format using encoding techniques compatible with decompression algorithms now existing and being developed ~nd ~andardized by the International Standards Organization (ISOs) Motlon Picture Expert~
Group (MPEG). Each title comprises video information stored as an addressable data file in conventional data processinq devices functioning as a video library.
The functlon of establishing and monitoring connections llnking a video library port transmitting selected~information with the end user ports receiving the information is performed by a supervisory controller such as a network control system, e.g., 3~ FLEXCOM~ software, used to control the electronic digital cro~s-connect switches (DCS) in the PSTN. The DCS, also used for switching two-way DS-1 rate transmissions, is adapted to additionally provide brldging or broadcast of video information to several 669' I'CI~ S92/(~8 2~2~3~

users. The normal data session" control between a video librar~ ror~ ~nd a port providing access te the ~ideo-on-dem~n~ ~quipment is one of the functions performed by the ~entral processing unit in the video library. The network control software and an ad~unct proce~sor control the ~network ses~ion' between the video-on-demand access port and user ports. The ad~unct processor a f 80 maintains a record of relevant data regarding each session which is forwarded to a customer billing system.
Customer local loop~ equipped with Asymmetric Digital Sub~criber Line (~DSL) devices are connected to the DCS. The video-on-demand system provides for the simultaneous tran~port of a one-w~y 1.544 megnbit per second (MsPS) slqnal over the same twi~ted pair transmltting :olce messages to the re~ldential subscriber. The ~DSL transported signal is demultiplexed nnd the 1.544 portion is then decoded using MPEG standard techniques to deliver a fu1l ~otion video signal. In the PSTN, fiberoptic technology will replace exi6tlng coaxial and twisted pair connectivity with correspondlng enhancements made to switching and routing equipment.
Referrin~ to Flgure 2, a video~on-demand system ~-includes C0 equipment lO which is part of a PSTN. C0 lO provides video/audio connectivity from VIPs 140 and 160 selectively through the system to subscribers 100 and 120. - ~-C0 lO includes a conventional voice switch 12 which includes means to detect off-hook, service requests, call completion ~i.e., ring trip), a DTMF
decoder 14 and dial pulse detector. Voice switch 12 al60 includes an actual telephone call connection ~093/066~ 1'Cr/~lS92/~6~-16 2~2~n3~

switch for routing voice circuits among the variou ports.
Conne~ted to voice switch 12 are ADSL equipment 16 and 18 for multiplexing (i) voice and signallng information ~rom voice switch 12 and (ii) digital video/audio information from Digital Cross-Connect System (DCS) 2~ onto respective subscriber local loops ; .
20 and 22. Dlgital compressed vldeo and audio data from VIPs 140 and 160 is provided to DCS node 26.
Under control of Network Management System 2~, connectivity is estab-l~Qhed between DCS node 26 and DCS
node 24, Output nodes of DCS 24 provide the digital video/audio data to selected ADSLs 16 and 18 for transmission to subscriber premises 100 and 120.
~DSLs 16 and 18 multiplex data on subscribers loops 20 and 22 using frequency multiplexing, dividing -~
the avallable loop bandwidth into three segments as shown in Flqures 3 and 4. Base band audio and -~
~ignaling below 4 kllohertz (kHz) provide~ connectivity for a convent~onsl telephone services available on the "plain old telephone system" (POTS). Alternatively, ISDN channel requirements consume the bottom ~0 kll~. of loop bandwldth. Reverse channel dlgltal packet lnformatlon is posltloned between 80 and 9~ k~z :
providlng approxlmately 16 kilobits per second (kbps) connectlvlty ~rom the subscriber premi~es to a packet ;
swltched network such as ISDN network over a D-channel interface. Compressed digital video information is .. -`
contained between 100 and 400 kHz to provide a 1.6 MBPS
channel for transporting video/audio data over :
respectlve loops 20 and 22 to customer premise~ 100 and 120.
The ~DSL multiplexor is functlonally shown in Flgure 3. Multiplexor 200 in combination with ~DSL

W093/0669t PCT/~IS92/06X~, 17 212~

line ,'02 ~upport transmission of a one-way 1.544 M~PS
digital siynal ~long with a POTS or ~ sase R~te ISDN
signal over a single non-loaded copper pair. This configuration provides service to a customer o~er copper loop length~ of up to 18,000 feet, thereby conforming w~th Carrier Serving ~rea (CS~) and re~istance design rules. The only further limitation ls that the loop be non-loaded.
Referr~ng to F~gure 4, the ~DSL's transmission system provides three transmlssion wlndows on a frequency multlplex basis. The wlndow repre~ented by area 302 provides a 2-way channel used to provide standard P~TS ~ervice or ISDN (2B+D) service over the ADSL line. Wlndow 304 is an up-stream only (subscriber to CO), low speed data channel. The channel has a bandwldth of 32 KBPS. Slxteen RBPS of this window is u~ed for tran6fer of operations, administration, malntenance, and provisioning (OAM&P) data for the ADSL
unit. The remaining 16 KBPS, compatible with D channel interfaces of ISDN-BRI, is used to interface with an ~-:
ISDN packet swltch allowing the subscriber to interact -with the network and/or the 1.544 MBPS slgnal provlder.
Wlndow 306 is a down-stream only (CO to ~ubscriber) dlgltal signal providing 1.544 MBPS -tran6por~ (1.6 M~PS with overhead) for carrying the digitlzed compres6ed video signal. The combined --digital down-stream signal utilizes the DSl bit map specified by ANSIT1.403-1989. ~ ;
Because data channels 304 and 3~6 are unidirectional, the sy~tem does not experience self- ~ -NEXT (near end cross-talk). This allows concentration -~
on the interface and interference from impulse noise becau~e the ~DSL sy6tem is loss-limited rather than ~-()93/()669' I'C~ S92/068~' ~~ 18 212~

N~XT limited. Impulse nolse exposure can be reduced by using a pa9~ t~And technique as opposed to a base band approach ~inc~ impulse noise affects are greatest below 40kHz. There~ore, a base band Quadrature ~mplitude Modulatlon (Q~M~ .~y~tem is preferred over a 2BlQ base band system.
~ eferrinq ~o Fiqure 4, the lower edge for window 306 is set at l00kHz. This edge is chosen to minimize channel 109~ ,~nd to allow appropriate bandwidth for base band channel 302 and reverse channel 304 and to minimize interference from impul~e noi~e. Design of the interface provide~ error-free operation with ringing voltaqe present on the line. The system is further designed to be immune to on-hook and off-hook transients and dial pulsing. In addition to base band POTS service, the ADSL system can co-exist with other transmission systems such as Hlgh Speed Dlgital Subscriber lines (~IDSL) Dl, Tl and data circuits.
Figure ~ shows a typical in-the-home configuration which provide~ tideo tran~ported over the 1.5q4 M~PS
channel. The unldlrectlonal 1.544 M~PS slgnal carried by the ADSL sy~tem has either a Superframe Format tSF) or an ~xtended Superframe format (ESF). The Superframe format consists of 24 consecutive 8-bit words preceded by one bit called the framing bit (F-bit) for a total of 193 bits per frame. The F-bit is time-shared to synchronize the ~DSL interface equipment and to identify signaling framing. Twelve consecutive frames form A Superframe. ~ line code used with a Superframe format is bi-polar return-to-zero, also known as Alternate Mark Inversion (~`MI).
The FSF format con~ists of 24 consecutive frames, each of which includes 192 information bits preceded by lF-bit for a total of 193 bits per frame. The F-bit is ~093/0~69' PCT/~IS92/06X~-~
, ~ , 2120~33~
used ~or ~asic frame synchronization, a ~yclic redundancy che~k and a data link. Twenty-four frames form a Super~rame. The line code used with the ESF is either ~MI, bi-polar ~ ero substitution (~8ZS), or ~MI
w~th Zero-Hyte Time Slot Interchange (ZBTSI).
Subscriber and CO ~DSL interface units are : :
synchronized to ensure that both units derive timing from one master clock to preven~ data loss. Stand alone unlts derive tLming from the incoming 1.544 M8PS
signal. Subscriber and ~DSL equipment are powered locally from the customer premises. ADSL equipment installed in the CO are powered with a DC input voltage of between -42.5 and -55 VDC.
Figure 6 is a block diagram of an ADSL system providing simplex hlgh-blt-rate vldeo data and P~TS
connectlvity to a sub~criber over a common copper loop.
The ~SL sy6tem has the transport capability to deliver a one-way high-bit-rate data stream with POTS
or ISDN basic access multiplexed at baseband.
Two subscriber premises configurations 100 and 120 are shown in Figure 2. In subscriber premise6 100, video order~ are placed using standard POTS 6ervice provided with telephone instrument 1~2 interfaced through subscriber ~DSL interface 104 to voice switch 2~ 12. ~ sub~criber at premises 100 requests the - -~
transmission of video data using telephone instrument 102 by dialing voice Response Unit (VRU) 34 of video gateway 32 through voice switch 12. Figure 7 is a flowchart showing operatlon of VR~ 34 for ordering video information.
Referring to Figure 7, voice switch 12 establishes `~-connectivlty ~ith VRU 34 which answers the incoming call. The vRU prompts the subscriber for a user ID
whlch i~ input via the DT~ pad of teleph~ne in~trument :,.: ~. ., ,: ~ :-.

W093/0669~ ~'Cr/US92/068 2123~31 ~

102. The u~er ID is checked and, if valid, the v~u promptC for a video selection. The video selection is then input uY1nq the DTMF pad of telephone instrument 102 which then ~ends the selection information to the Vldeo Informatlon ~rovider (VIP) via video gateway 32 and packet data network 40. The VIP identifies the requested tltle and determines if the title is ~ -available.
If the tltle ls found, and has not been previously queued for transmission, the corresponding data file is opened and a reserve idle communications port is ldentlfied for transmlssion of the vldeo data to DCS
node 26. Transmi~sion of the data iY delayed for a predetermined number of minutes in respon~e to a firYt reque~t for the video selection to allow for Yimultaneous trAnsmission of the video data file to subsequent subscrlbers placing an order for the same tltle within the delay period. The subsequent request orders are also placed in the queue and the aY~ociated communicatlons port ID i~ matched to the YubYcriber~Y
network address.
After expiratlon of the predetermined delay, i.e., when current time as Yhown in the flowchart equals the designated ~tart tlme, video data file ls transmitted from VIP 140 or l60, a~ appropriate, through DCS nodes 24 nnd 26 to the designated ~DSL interface~ 16 and 18 ~ ~
for transmission to subscriber premiYes 100 and 120. - ~-~t the end of the program, a message i5 transmltted to ~ :
Network Management System 28 to take the system down by terminating connectivity between DCS nodes 24 and 26.
In an enhanced verslon of the video-on-demand system, subscriber premises 120 (Figure 2) is provided wlth a control unlt 130 for receiving data commands from remote control 132. Remote control 132 can be a W093/0669~ PCT/US92/n68~7 21 2~2~3~

conventlonal Infrared remote control for interacting ~ .
with control l~nit 130. Data from control unit 130 is provided t o .~ubscriber ~DSL interface 124 for transmiysion of command data to ISDN D-channel lnterface 38. The ISDN D-channel interface can p~ovide subscriber order information directly to video gateway 30 in lieu of using voice response unit 34. Once video gateway 32 ldentlies a sub6criber reque~t to e6tablish connectivity between a VIP 140 or 160, the address of control unlt 130 18 provided to the selected VIP. Upon receipt of the correRponding VIP network address by control unit 130, direct connectivity is established between control unit and VIP 140 or 160 over packet data network 40. This connectivity permits direct data -~
transfer between the customer premises and the associated VIP to support interactive video control used in interactive educational programming and interactive vldeo pre~entations such as video game6.
Control unit 130 provides further functionality by providing for lnteractlve control of the buffered video data. As 6hown ln Flgure 2, temporary ~torage device 42 can be controlled over packet data network 40.
Wlthln the llmlt~ of data stored ln the buffer, the .:~.
subscriber can ast forward, rewind, forward, reverse search and pause the video/audio data provided via DCS ~;~
24 to the subscrlbers premise~. If the requested function exceeds the capability of the temporary :.
storage to buffer information provided by the VIP, the subscriber wlll have the optlon of cancelling the ; :~
request or being rescheduled into a later transmission .:~
of the video programming. For example, if a pause request lnitiated via control 130 results in overflow of temporary storage 42, video transmission to the customer premises will either be continued with a `, '~: '~'.
:..~':
::

~'093/0669t PCT/IJS92/068~7 22 2~ 2ao3~

message or, at cu~tomer direction, will be discontinued and the transmis~ion rescheduled for later transmis~ion.
VIPs 140 and 160 include re~pective control units 142 and 162 ~or a~cessing video storage units 144 and 164. ~8 discuqsed above, the VIP stores the requested program material in coded or compres~ed digltal format to mlnlmlze B torage requirements and trans~is~ion bandwidth. Sultable video coding algorithms rely on Motion Compensated Prediction (MCP) and Motion-Compensated Interpolation (MCI). Motion Compensated Predictive/Interpolat1ve Coding (MCPIC) is described in Wonq et al. ~MCPIC: ~ Video Coding Algorithm for Transmi~sion and Storage ~ppllcation~", Nov. 1990 IEEE
Communication~ M~qazine. MCPIC provides compre~ion of vldeo lnformatlon for VCR quallty playback uslng pre~
proce~slng snd encoding of the video source information to obta~n a coded b1t ~tream. The bit stream represents a progressive format of 30 frames per 2~ second, each frame having 352 x 24~ samples for luminance (y) and 176 x 12~ samples for each of two `;~
chrominance chsnnel~ (U and V). The MCPIC algorithm supports vldeo material ranglng from qlow to fast motlon wlth a resolution equivalent to that of consumer-grade VCR's.
Another compresslon technique using Motion ~-Estimntlon, Motion-Compensation Predictive Coding and Adaptive Discrete Cosine Transform (DCT) quantization is supported by the Internatlonal Standards Organization (ISO) Moving Pictures Expert Group (MPEG).
MPEG-l specifies a video coding algorithm having a data rate of l.2 MBPS. This digital-video and digltal-audio compression standard can be accommodated by a T-l line or a D-l channel to provide full-motion video within WO 93/06692 PCr/US92/n6857 23 2~ 20~3~

the I . 544 MMPS d~ta channel provided by an ~DSL to the subscriber ~remi~es. MPEG programmable decoder/proce~sor~, cspable of de~ompres~ing digital video in re~l ~ime, have been produced by such companie~ as C-Cube Micro~ystem~ and LSI of San Jose, California. The~e or equivalent device6 are incorporated into decoders 106 and 126 ~hown in Figure 2 to generate ~tandard NTSC analog video and analog audlo signals.
In addltlon to the ba~ic video-on-demand ~rchitecture shown in Figure 2, other feature~ can be incorporated lnto the PSTN under softw~re control. For example, a subscriber can elect to implement call blocking through ~wltch 12 to avold interruption~ from incoming call~ during the duration of the video program. Incoming calls would instead be diverted to a subscriber~s volce mail box.
. . , VRU 34 may addltionally include voice recognition c~pability to ~upport voice recognition security functions and voice selection of video programming.
An alternatlve embodiment of the invention is ~hown in Figure ~ wherein connectlvity between central office 10a flnd subscriber preml~es 100a and 120a i5 provlded by re~pective Hlgh-bit-rate Digital Subscriber Lines (HDSL) and ~eparate PQTS lines. The HDSL uses bi-directional four wire T1 lines 48 and 50, including repeaters 52 and 54 to connect Office Repeater Bays (QRB) 44 and 46 to Customer Service Units (CSU) and Digital Service Units (DSU) 110 and 134 located ~in respective customer premises 100a and 120a. The ~DSL
requires two pairs and provides full duplex transport at a DSI rate ~or loops limited to a CSA standard range. Because the HDSL does not provide a low bit-rate data channel, data from the ~ub~criber premises to Wo93/()669' 24 212a~3~ PCT/~IS~2/068~-the CO is earriod using full duplex bi-directional Tl service. Separate POTS service is provided on lines 56 and 58. The subscriber loop may also comprise a copper Diqital Loop ~arrier (DLC~ wherein analog data is converted to ~ digital format and transported over a Tl copper loop circuit. The remaining structure and operation of the video-on-demand system shown in Figure 8 is otherwfse generally the same as discussed with respect to the embodiment shown in Figure 2 o~ the drawings.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration an example and is not to be taken by way of limitation, the spirit and scope of the present lnvention being limited only by terms of the appended clalms.

Claims (17)

AMENDED CLAIMS
[received by the International Bureau on 3 February 1993 (03.02.93);
original claims 1-50 replaced by amended claims 1-17 (4 pages)]

1. A public switched telephone network for providing digital video signals from a video information provider to any one of a plurality of subscriber premises, comprising:
a telephone company central office receiving digital video signals from a video information provider and subscriber orders from a prescribed subscriber, said central office including a video gateway for providing video scheduling and routing data in response to subscriber orders and a switch for routing video signals from said video information provider to the prescribed subscriber in accordance with said scheduling and routing data;
a central office interface including, for each subscriber, a first frequency multiplexer/demultiplexer for transmitting or receiving audio telephone service signals, subscriber control signals and digital video signals on, respectively, first, second and third signal channels displaced from each other in frequency;
each said subscriber premises including second frequency multiplexer/demultiplexer means for transmitting or receiving audio telephone service signals, subscriber control signals and digital video signals on, respectively, the first, second and third signal channels; and a plurality of subscriber local loops interconnecting corresponding central office and subscriber interfaces.

2. The network of claim 1, wherein said first channel is a bidirectional channel carrying said audio telephone service signals between the subscriber and central office, said second channel is a unidirectional channel carrying subscriber control signals to said central office, and said third channel is a unidirectional channel carrying digital video signals from said central office to the subscriber.

3. The network of claim 2, wherein said first, second and third channels occupy progressively increasing frequency bands, with the first channel occupying the lowest.

4. The network of claim 3, wherein said first, second and third channels are non-overlapping.

5. The network of claim 1, wherein said subscriber interface includes a splitter for supplying telephone service and video signals incoming from the central office to telephone and television terminals.

6. The network of claim 1, wherein said local loops comprise wire pairs.

7. The network of claim 1, wherein said local loops comprise coaxial cable.

8. The network of claim 1, wherein said local loops comprise optical fibers.

9. The network of claim 1, wherein said subscriber interface includes a decoder for converting an incoming digital video signal to an analog video output signal.

10. The network of claim 9, wherein said decoder includes a decompressor for decompressing the incoming video signal and producing analog video and associated audio output signals.

11. The network of claim 1, wherein said central office further includes a packet data network responsive to said video gateway for supplying command signals to said video information provider.

12. The network of claim 1, including video storage means remote from the subscriber premises for buffering video data obtained from said switch and supplying buffered video data to a prescribed central office interface.

13. The network of claim 12, wherein said central office interface includes a control link output node for supplying said subscriber control signal to said video storage means.

14. The network of claim 1, wherein said video gateway comprises a memory storing subscriber access data, and further wherein said gateway is responsive to subscriber identification information and said stored access data to supply said video scheduling data to said video information provider.

15. The network of claim 1, including a voice switch responsive to telephone number data transmitted from said subscriber interface for establishing an audio connection from the local loop of a prescribed subscriber to the video gateway.

16. The network of claim 15, wherein said voice switch further supplies caller identification information to said video gateway that, in turn, supplies network address information to said switch for directing video data from the video information provider to a prescribed central office interface.

17. The network of claim 1, including voice response means for supplying to said switch a voice reply to order data received from a prescribed customer premises.