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WO1997001244A1 - Procede et appareil donnant acces a un grand nombre de canaux de communication via un conduit a bande passante relativement etroite - Google Patents

Procede et appareil donnant acces a un grand nombre de canaux de communication via un conduit a bande passante relativement etroite Download PDF

Info

Publication number
WO1997001244A1
WO1997001244A1 PCT/US1996/010599 US9610599W WO9701244A1 WO 1997001244 A1 WO1997001244 A1 WO 1997001244A1 US 9610599 W US9610599 W US 9610599W WO 9701244 A1 WO9701244 A1 WO 9701244A1
Authority
WO
WIPO (PCT)
Prior art keywords
communications channel
channels
communications
server interface
narrow bandwidth
Prior art date
Application number
PCT/US1996/010599
Other languages
English (en)
Inventor
Philip C. Richards
Original Assignee
Transwitch Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Transwitch Corporation filed Critical Transwitch Corporation
Publication of WO1997001244A1 publication Critical patent/WO1997001244A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/65—Arrangements characterised by transmission systems for broadcast
    • H04H20/69—Optical systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/2801—Broadband local area networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/16—Analogue secrecy systems; Analogue subscription systems
    • H04N7/173—Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal
    • H04N7/17309—Transmission or handling of upstream communications
    • H04N7/17318—Direct or substantially direct transmission and handling of requests
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
    • H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
    • H04Q11/0478—Provisions for broadband connections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5638—Services, e.g. multimedia, GOS, QOS

Definitions

  • the invention broadly relates to telecommunications. More particularly, the invention relates to a method and apparatus for providing access to a large number of communications channels, in particular television channels, via a relatively narrow bandwidth conduit.
  • Cable television channels are transmitted as RF signals via coaxial cable to subscribers. All of the subscribers receive all of the channel signals simultaneously through the coaxial cable which is arranged as a read-only bus system.
  • Each subscriber is provided with a tuner/decoder box ("set-top box") which is coupled to the coaxial cable and to the subscriber's television set.
  • set-top box Typically, approximately forty television channels are simultaneously transmitted through the coaxial cable. While it is theoretically possible to transmit many more channels through a coaxial cable, practical limitations described below, limit the bandwidth of coaxial cable TV to about forty channels .
  • Some of the channels, e.g. premium movie channels, may be encrypted or coded.
  • the classic set-top box includes an RF receiver, a tuner, a transmitter, and a programmable decoder.
  • the subscriber selects a channel with the tuner and the channel is transmitted via a cable connection from the set-top box to the subscriber's television set where it is received on channel 3 or 4. If the channel is coded or encrypted, the subscriber can only view the channel if the subscriber's set-top box is programmed to decode the channel.
  • Modern set-top boxes accept two inputs and use an "A-B switch" to select from up to one hundred channels (fifty channels on each coaxial cable bus) .
  • A-B switch to select from up to one hundred channels (fifty channels on each coaxial cable bus) .
  • channels fifty channels on each coaxial cable bus
  • cable television providers are exploring ways to increase further the channel capacity of the cable television system.
  • Modern set-top boxes are "addressable".
  • the decoding and/or tuning capabilities of an addressable box may be affected by the signals it receives via the coaxial cable.
  • each addressable box has a unique identification (address) .
  • the cable television provider can program the addressable box by transmitting the address of the box together with programming codes via the coaxial cable.
  • the address and programming codes are actually received by every set-top box connected to the coaxial cable, i.e. all of the subscribers. However, only the box having the selected address will respond to the programming signals.
  • the use of addressable boxes allows the cable television provider to program "pay-per-view" channels. Pay-per-view programming operates according to a published schedule.
  • a subscriber chooses to view a scheduled pay-per-view program by placing a telephone call to the cable television provider.
  • the provider then transmits the appropriate address and programming codes to allow the subscriber's set-top box to decode the pay-per-view channel for the duration of the program.
  • the advantage of pay-per-view is that a subscriber need not pay for a monthly subscription to a "movie channel", but rather may pay for programs individually. It is potentially more convenient than renting a movie from a video store, but it has the substantial disadvantage that it is pre-scheduled.
  • VOD video-on-demand
  • a subscriber With VOD, a subscriber will be able to select a program from a published but unscheduled menu of programs to watch a selected program at any time the subscriber chooses.
  • conventional coaxial cable television systems are incapable of providing VOD programming.
  • the subscribers are not directly connected to the provider by unique downlinks, but rather receive signals from a common bus. There is simply not enough bandwidth in the coaxial cable bus to provide unique channels for more than a few subscribers.
  • the subscriber in order to provide a VOD service which has all of the advantages of a video tape rental, the subscriber must be able to pause, rewind, fast forward, etc. Therefore, each VOD subscriber must have a unique uplink to the provider in order to control the delivery of VOD. In order to provide VOD, therefore, the network architecture of a cable television system must be completely redesigned.
  • the network architecture of a conventional cable television system is a read-only bus structure where all of the subscribers are coupled to the provider, and essentially to each other, by a single coaxial cable having many branches.
  • This is quite different from the network architecture of a telephone system, for example, where each subscriber is individually and bi-directionally connected to the service provider (the central office switch) .
  • the optimal VOD service would seem to require that each subscriber be individually and bidirectionally coupled to the service provider. Unfortunately, this would require a complete rewiring of a cable television system.
  • VOD services Because of the intense interest in VOD services, and the fact that these services seem to require an individual bi ⁇ directional link between subscriber and provider, local telephone companies are exploring ways to increase the bandwidth of their copper cable (twisted pair) network to provide a direct bi ⁇ directional video link to each customer with no loss or noise.
  • the most promising approach to achieving this goal is to convert the composite analog video signal to a digital signal and to subject the digital signal to a data compression algorithm.
  • the Motion Picture Experts Group (MPEG) was formed to standardize algorithms for digital video compression.
  • the MPEG-2 algorithm allows a VCR quality video signal to be compressed to a bandwidth of approximately 6 Mbps (approximately the same bandwidth as analog broadcast video, but with the noise immunity of a digital signal) .
  • ADSL Asymmetric Digital Subscriber Lines
  • fiber optics In order to compete with the potential video offerings of local telephone companies, cable television systems are exploring fiber optics as a solution to the limited bandwidth of the read- only coaxial cable bus system. For example, an "OC-12" fiber link is capable of delivering 622 Mbps. This is enough bandwidth for approximately 70 broadcast television channels in addition to approximately 16 VOD channels.
  • Systems which carry fiber optic signals directly to a subscriber's home are referred to a Fiber to the Home (“FTTH”) systems. These systems replace existing coaxial cable with fiber optic cable. New set-top boxes are provided which couple directly with the fiber optic cable and provide broad bandwidth bidirectional capabilities. Unlike coaxial cable, fiber optic cable requires special terminations if a single cable is designed to serve several set-top boxes in a single home.
  • HFC Hybrid Fiber Coax
  • each provider can be allocated a portion of the coaxial cable bandwidth for VOD. Since the bandwidth of coaxial cable is relatively narrow, in order to serve a reasonable number of subscribers via the same cable bus system, sophisticated multiplexing techniques are used to enhance the bandwidth of the bus and these techniques rely on a sophisticated demultiplexing system in each subscriber's set- top box.
  • Another system which has been proposed eliminates all cable connections to the home by using a high frequency (40GHz) radio link to each subscriber from a fiber optic termination point. Each subscriber is assigned a dedicated frequency band for bidirectional communication and a relatively sophisticated unit in the home interfaces the high frequency transceiver with the subscriber's television sets.
  • FTTC Fiber to the Curb
  • HFC Fiber to the Curb
  • the method of the present invention includes providing a fiber optic downlink conduit from a programming source to a "curb-top" box (a communications channel server interface) and a fiber optic uplink conduit from the curb-top box to the programming source, and providing a plurality of relatively simple set-top boxes (communications channel client interfaces) which are bidirectionally linked to .the curb-top box via existing coaxial cables.
  • the curb-top box is provided with the ability to access all of the channels carried by the downlink and to rebroadcast selected channels as RF signals to the set-top boxes via the existing coaxial cables.
  • the set-top boxes are each provided with the ability to send selection signals to the curb-top box via the coaxial cable and to receive RF television signals from the curb-top box via the coaxial cable.
  • the RF television signals may be sent directly to the subscriber's television set for tuning and demodulation, or the set-top box may include tuning, demodulating, and remodulating circuits.
  • the downlink to the curb-top box provides approximately 70 television channels and approximately 16 VOD channels as compressed digital signals.
  • the uplink from the curb-top box provides control signals to the programming source for each of the VOD channels.
  • a portion, e.g. 5% of the uplink and downlink bandwidth is reserved for telephony, and VOD channels are utilized for video telephony.
  • unused VOD channels are used to deliver additional broadcast programs when needed.
  • the arrangement of curb-top boxes and set-top boxes also precludes theft of cable services because the curb-top box determines what signals are sent to the set-top boxes and the workings of the cur-top box are accessible only to the service provider. Therefore, only authorized signals enter into the homes of subscribers.
  • the downlink to each curb-top box is preferably an OC-12 fiber link and uplink from each curb-top box is preferably an OC-3 fiber link.
  • Figure 3 is a block diagram of one embodiment of a curb-top box according to the invention.
  • Figure 4b is a block diagram of a second alternative embodiment of a set-top box.
  • Each curb-top box, e.g. 42 is coupled via existing coaxial cable 54, 56, 58 to the homes 60, 62, 64 of Cable TV subscriber.
  • the ATM network 24 is a bidirectional data path and that at least some of the communications channels 10, 12, 14 will be bidirectionally coupled to the ATM network.
  • some of the communications channels, e.g. the television broadcast/satellite receiver 12 may be unidirectionally coupled to the network, thereby providing data to the network without receiving any data from the network.
  • Each curb-top box is bidirectionally coupled to the network, and each coaxial cable link 54, 56, 58 serves as a bidirectional data path between the curb top box 42 and a respective subscriber home 60, 62, 64.
  • FIG. 2 is a more detailed view of the connections between the curb-top box 42 and subscriber households 60-64.
  • the curb-top box 42 receives data from the network via a broad band OC-12 optical connection 42a and returns data to the network via an OC-3 optical connection 42b.
  • Households 60-64 are coupled to the curb-top box 42 by respective existing coaxial cables 54-58.
  • An existing coaxial cable, e.g. 54 may serve up to four television sets 160a-160d in household 60, each set being coupled to the cable 54 by a respective set-top box 260a-260d.
  • the number of television sets served by the curb-top box and the number of set-top boxes coupled to a single coaxial cable bus may be varied according to design choice.
  • the presently preferred embodiment envisions twenty to thirty-two set-top boxes served by a single curb-top box, and up to four set-top boxes served by a single coaxial cable bus.
  • each curb-top box e.g. 42
  • the ATM switch 70 provides selected digital channels to an internal data bus 72.
  • Groups of four digital-to-analog converters (DACs) 74a-d, 76a-d, etc., are coupled to the data bus 72, each DAC extracting a single data channel and converting the digital data to an analog signal.
  • the outputs of each group of the DACs 74a- d, 76a-d are coupled to respective RF modulators 78, 80 wherein the analog signal from each DAC is prepared for transmission via a respective coaxial cable.
  • Each of the RF modulators 78, 80 is coupled via a respective interface 82, 84 to a respective coaxial cable 54, 55, which typically will be an existing cable-tv cable.
  • Each coaxial cable interface 82, 84 is also coupled to a respective control signal receiver 86, 88 for receiving control signals from the respective coaxial cables 54, 55.
  • the control signals which will be described in more detail below, are used to select which data channel from the downlink 42a is sent to which DAC 74a-d, 76a-d and also to send control signals to the uplink 42b.
  • control signal receivers 86, 88 are coupled to a microprocessor controller 90 and the controller 90 is coupled to each of the DACs 74a-d, 76a-d as well as to the ATM switch 70.
  • control signal receiver 86 includes means for receiving an analog data signal which will be placed on the data bus 72 via an analog-to-digital converter 86a for transmission via the ATM switch 70 to the digital network.
  • the operation of the curb-top box 42 is responsive to requests from the set-top boxes which are coupled to it.
  • FIG. 4 illustrates the operation of two set-top boxes 260a, 260b which are coupled to a single coaxial cable bus 54 served by the curb-top box 42 described above.
  • Each set-top box includes a tuner 262a, 262b for selecting one of the analog signals carried on the coaxial cable 54 and an RF modulator 264a, 264b for transmitting the selected signal to the RF section of a television set for reception on an unused local channel, typically channel 3 or .
  • the tuner 262a, 262b is preferably coupled to and controlled by a microprocessor controller 266a, 266b which receives commands from a keypad 268a, 268b.
  • the control signal is interpreted by the controller 90 in the curb-top box 42 which directs one of the DACs 74a-d to access the selected channel and convert the data therein to an analog signal.
  • the analog signal is modulated by the RF modulator 78 and transmitted via the interface 82 onto the cable 54.
  • the modulated RF signal is tuned by the tuner 262a in the set-top box 260a and remodulated by the RF modulator 264a so that it can be received by an attached television on an unused local channel such as channel 3 or .
  • the number of analog signals modulated on the cable 54 is limited only by the number of DACs which are coupled to the cable. In a presently preferred embodiment, four DACs 74a-d service each coaxial cable bus 54.
  • the analog signal is modulated by the RF modulator 78 and transmitted via the interface 82 onto the cable 54 on a channel (e.g. 3, 4, 5, 6, etc.) which is assigned to the set-top box 260c so that it can be received by an attached television on the assigned channel.
  • a channel e.g. 3, 4, 5, 6, etc.
  • curb-top box may be configured in the field to provide different numbers of DACs for each cable bus. Thus, if one household has two televisions, the cable bus to the that household may be coupled to only two DACs.
  • the methods and apparatus of the invention also permit the efficient delivery of VOD services.
  • a subscriber chooses a VOD program in much the same way as choosing any other program as described above.
  • the subscriber's command is relayed by the curb-top box 42 via the controller 90 through the ATM switch 70 back onto the digital network 24, 26, 28 where it is forwarded to the VOD server 10.
  • the ATM switch 16 coupled to the VOD server 10 provides the appropriate header for the digital video data which is sent over the digital network and is received by the curb-top box 42 where it is transmitted to the set-top box 260 via the DAC 74 and RF modulator 78.
  • the VOD user may pause, rewind, fast forward, or freeze the VOD display. These VCR-like commands issued by the user are transmitted back to the VOD server by the curb-top box.
  • curb-top and set-top boxes wherein existing coaxial cable is used to provide access to broad band fiber optic networks. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus, while portions of the invention have been described as "curb-top” and “set-top”, it will be understood that these terms are used illustratively only and should not be considered limiting in any way. These portions of the invention need not be located near a curb or a set.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Multimedia (AREA)
  • Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
  • Small-Scale Networks (AREA)

Abstract

L'invention porte sur un procédé et un appareil donnant accès à un grand nombre de canaux de communication via un conduit à bande passante relativement étroite, comportant la mise en ÷uvre d'un conduit de liaison descendante à fibre optique (20) d'une source de programmation (10, 12, 14) vers un module utilisateur du boîtier de raccordement voirie (42) et d'un conduit de liaison montante à fibre optique (28) du module utilisateur du boîtier de raccordement voirie (42) vers la source de programmation (10, 12, 14) ainsi que de plusieurs coffrets d'abonné relativement simples en liaison bidirectionnelle avec le module utilisateur du boîtier de raccordement voirie (42) par des câbles coaxiaux existants (54). Le module utilisateur du boîtier de raccordement voirie (42) est capable d'accéder à tous les canaux portés par la liaison descendante (28) et de rediffuser, comme signaux H.F., des canaux sélectionnés vers les coffrets d'abonné via des câbles coaxiaux existants (54). Les coffrets d'abonné sont également à même d'envoyer des signaux de sélection vers le module utilisateur du boîtier de raccordement voirie par le câble coaxial (54) et de recevoir des signaux H.F. de télévision en provenance du module utilisateur du boîtier de raccordement voirie par le câble coaxial (54).
PCT/US1996/010599 1995-06-21 1996-06-19 Procede et appareil donnant acces a un grand nombre de canaux de communication via un conduit a bande passante relativement etroite WO1997001244A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US49275295A 1995-06-21 1995-06-21
US08/492,752 1995-06-21

Publications (1)

Publication Number Publication Date
WO1997001244A1 true WO1997001244A1 (fr) 1997-01-09

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PCT/US1996/010599 WO1997001244A1 (fr) 1995-06-21 1996-06-19 Procede et appareil donnant acces a un grand nombre de canaux de communication via un conduit a bande passante relativement etroite

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0881815A3 (fr) * 1997-05-26 2000-10-25 Telsey S.r.l. Procédé et dispositif de distribution de services à large bande
WO2000064174A1 (fr) * 1999-04-20 2000-10-26 Diva Systems Corporation Optimisation de la bande passante d'un reseau par attribution dynamique de canaux
WO2000056057A3 (fr) * 1999-03-18 2000-12-14 Next Level Comm Procede et appareil destines a la connexion transversale des signaux video
WO2001067765A1 (fr) * 2000-03-10 2001-09-13 Alma Media Oyj Procede et station dans un reseau de diffusion numerique a connexion de telecommunication bidirectionnelle

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5181106A (en) * 1991-07-31 1993-01-19 Alcatel Network Systems, Inc. Video line shelf arrangement in an optical fiber telecommunications network providing broadband switched video services
US5357276A (en) * 1992-12-01 1994-10-18 Scientific-Atlanta, Inc. Method of providing video on demand with VCR like functions

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5181106A (en) * 1991-07-31 1993-01-19 Alcatel Network Systems, Inc. Video line shelf arrangement in an optical fiber telecommunications network providing broadband switched video services
US5357276A (en) * 1992-12-01 1994-10-18 Scientific-Atlanta, Inc. Method of providing video on demand with VCR like functions

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0881815A3 (fr) * 1997-05-26 2000-10-25 Telsey S.r.l. Procédé et dispositif de distribution de services à large bande
US6389004B1 (en) 1997-05-26 2002-05-14 Telsey S.R.L. Broadband service distribution method and device
WO2000056057A3 (fr) * 1999-03-18 2000-12-14 Next Level Comm Procede et appareil destines a la connexion transversale des signaux video
US6408436B1 (en) * 1999-03-18 2002-06-18 Next Level Communications Method and apparatus for cross-connection of video signals
WO2000064174A1 (fr) * 1999-04-20 2000-10-26 Diva Systems Corporation Optimisation de la bande passante d'un reseau par attribution dynamique de canaux
GB2363692A (en) * 1999-04-20 2002-01-02 Diva Systems Corp Network bandwidth optimization by dynamic channel allocation
GB2363692B (en) * 1999-04-20 2002-08-28 Diva Systems Corp Network bandwidth optimization by dynamic channel allocation
US6718552B1 (en) 1999-04-20 2004-04-06 Diva Systems Corporation Network bandwidth optimization by dynamic channel allocation
US7669220B2 (en) 1999-04-20 2010-02-23 Comcast Ip Holdings I, Llc Network bandwidth optimization by dynamic channel allocation
WO2001067765A1 (fr) * 2000-03-10 2001-09-13 Alma Media Oyj Procede et station dans un reseau de diffusion numerique a connexion de telecommunication bidirectionnelle

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