WO 97/09826 PCT/AU96/00560
I -
A VIDEO SIGNAL DISTRIBUTION SYSTEM
The present invention relates to a video signal distribution system and, in particular, to a system which enables video signals to be distributed over a public switched telephone network (PSTN)
Different techniques and technologies have been proposed for providing a variety of video and television services to the home, m addition to the existing free to air broadcast network. The services include
1 Video on demand (VOD) where movies and video programs are 20 transmitted to a customer on request The video signals may be transmitted immediately or at a time selected by the customer Depending on the video signals transmitted, a communication channel between the video signal provider and the customer may also be used to allow the customer to send control signals to the provider to control transmission functions, such as pause, fast forward and 25 rewind, or m the case of interactive video game, signals which dictate play of a game This communication channel may also be used to provide interactive capability to other types of services, e g educational, home shopping, etc
2 Pay per view (PPV) where video programs are scheduled for transmission and a customer is only charged for the programs selected to view
3 Pay TV where a customer is able to access broadcast scheduled video programs and pays a subscription charge for Pay TV channels
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Telecommunications networks can be used to distribute video services A transmission technology known as asymmetric digital subscriber line (ADSL) technology has been developed to allow the transmission of high bit rate video signals on the existing copper wires of a PSTN An ADSL line is asymmetric because it allows the transmission of up to 8 to 25 Mb/s or more 5 to customers from a local exchange but only allows low speed (e g. 16 kbs, 64 kbps or 640 kbps) control signals to be sent to and from the customer and the local exchange A line carrying ADSL signals also allows simultaneous transmission of plain old telephone system (POTS) services between a customer's telephone and the exchange Two modulation techniques available for signal transmission on an access line are known as discrete multi-tone (DMT) and carnerless 10 amplitude phase (CAP) modulation. ADSL technology is described in a number of publications, such as
1 ANSI Standard T1E1 4/°4-007 Network and Customer Installation Interfaces Asymmetric Digital Subscriber Line (ADSL) Metallic Interface
2 JJ Werner, Tutorial on Carnerless AM/PM - Part I - Fundamentals and 15 Digital CAP Transmitter UDF Document, 29 September, 1991 Also
Contribution to ANSI X3T9 5 TP/PMD Working Group, Minneapolis, 23 June, 1992
3 M Sorbara, J J Werner and N A Zervos, "Carnerless AM/PM", Contribution T1E1 4/90-154, 24 September, 1990
4 W Y Chen, GH Im and S S Werper, "Design of Digital Carnerless
AM/PM Transceivers", Contribution T1E1 4/92-149, 19 August, 1992
Whilst ADSL technology has been suggested as a suitable platform for providing video on demand services, an efficient system architecture is required to distnbute video signals
In accordance with the present invention there is provided a video signal distribution system, including video signal provider equipment having first telecommunications means for providing video signals to at least one local exchange of a telecommunications network, and 30 local exchange equipment having second telecommunications means for receiving said video signals, a plurality of exchange units for transmitting video signals to a plurality of
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respective customer units, and a multicast video switch for multicasting said video signals received by said second telecommunications means to said plurality of exchange units for transmission to said customer units
The present invention also provides a video services distribution system including a video switch for receiving a plurality of video service channels from a telecommunications network, said video switch having a selection unit for multicasting said service channels to customer video channels, and modulating units for modulating signals on said customer video channels, received from 10 said video switch, for transmission on telecommunication lines to respective customer units
Preferred embodiments of the present invention are hereinafter described, by way of example only, with reference to the accompanying drawings, wherein
Figure 1 is a block diagram of a preferred embodiment of a video signal distribution
system,
Figure 2 is a block diagram of a local exchange of the system connected to customer premises equipment,
Figure 3 is a block diagram of a first preferred embodiment of the local exchange, Figure 4 is a second preferred embodiment of the local exchange,
Figure 5 is a block diagram of the local exchange of the first embodiment using 155
Mbit/s service distribution,
Figure 6 is a block diagram of a network element of the local exchange of Figure 5, Figure 7 is a block diagram of the local exchange of the first embodiment using 622 Mbit/s service distribution,
Figure 8 is a block diagram of a network element of the local exchange of Figure 7,
Figure 9 is a diagram illustrating cross-connection of channels of the local exchange of Figure 7,
Figure 10 is a schematic diagram of a local exchange of the second embodiment,
Figure 11 is a block diagram of a local exchange of the second embodiment using a 622 30 Mbit/s local exchange ring, and
Figure 12 is a block diagram of a local exchange of Figure 11 with a dual head local
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exchange ring
A video distribution system 2, as shown in Figure 1, includes video signal provider equipment 4 which is able to provide video and/oi interactive services to customers over a 5 transmission netwoik S, such as the PSTN, to a local exchange 6 associated with the customers The local exchanges 6 of the distnbution system 2 each include a video switch 8 and a video switch controller 10 which both connect to ADSL exchange units (EUs) 12 of the exchange 6 The ADSL exchange units 12 can be connected via copper pairs 14 to respective ADSL customer units 16 The video signal provider equipment 4 includes a video head-end 18 and a 10 billing and operation, administration and management (OAM) system 20 The video head-end 18 stores video signals for up to N different channels, which may be VOD, Pay TV or PPV channels, and downloads video signals on the channels to the video switch 8 of each exchange 6, via the transmission network 5 The video switch 8 selectively switches the n channels to the m ADSL exchange units 12 of the exchange 6 in response to control signals from the video IS switch controller 10 The video switch controller 10 selects a channel for each ADSL exchange unit 12 in response to control signalling data received from the EUs 12, which is sent by the ADSL customer units 16, or from the provider equipment 4 Channel switching for video channels which carry continuous video data, such as Pay TV, PPV and free to air channels, are switched localiy at the exchange 6 by the video switch 8 and the controller 10 The video switch 20 8 is able to multicast each one of the input channels received from the head-end 18 to selected ADSL exchange units 12 for selected customers, removing the necessity for each customer to have a respective high capacity video signal downstream channel back to the provider equipment 4 The ADSL units 12 and 16 are able to transmit POTS and ISDN signals with the video signal sent downstream to the customers and the control and signalling data sent in both directions 25 between the exchange 6 and the customer The billing and OAM unit 20 receives billing and operation, administration and management (OAM) data from the video switch controller 10 via the transmission netwoik 5 The controller 10 may simply pass data provided to it by the ADSL exchange units 12
The video signals output by the video head-end 18 may be obtained from a storage system such as a video server architecture or digital v.deo tape The video signals may also be
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provided from a real-tone source, such as an MPEG encoder The video signals of the channels are encoded at 2 or 6 Mbit/s for example The telecommunications infrastructure used to distribute the video signals from the provider equipment 4 to all of the local exchanges 6 of the video delivery network of the system 2 needs to be able to handle high-bandwidth, semi-5 permanent, unidirectional video connections between providers 4 and each exchange 6 The synchronous digital hierarchy (SDH) transmission system and protocol, as specified by the International Telecommunications Union (ITU), is able to achieve this, and two transmission standards of SDH can be used on the network 5, being STM-1 (155 Mbit/s) and STM-4 (622 Mbit/s) STM-4 is best used for transmission between the video storage system and hubs and 10 regional hubs of the provider equipment 4 Regional hubs can then be connected to the local exchanges 6 using STM-1 links Channels broadcast to the video switches 8 can be transmitted in a distribution ring to allow multiple splitting of video data at each regional hub with a connection to a local exchange 6 Transmission of the billing and OAM data would also use an SDH transmission network 5 The video switch 8 and the video switch controller 10 maintam 15 effective and reliable switching to ensure all video and interactive services which can be provided by the equipment 4 is distributed to customers over the ADSL links 14 The switch 8 and controller 10 provide the following
(a) Transparent switching of digitally coded video signals and other information services
(b) Multicast switching to the m customers of the exchange 6, which includes point-to-multipoint switching for Pay TV, PPV, near-VOD, free to air services, and point-to-point switching for VOD and interactive services
(c) Non-blocking switch operation
(d) Modular expansion.
(e) Locally controlled switching, as described above, to facilitate rapid response times when changing channels
The video switch 8 and controller 10 can be implemented using SDH cross-connect units Preferred alternatives for implementing the switch 8 and controller 10 include
(a) An SDH ADM Ring - SDH network elements (NE) are interconnected at the local exchange 6 to form a ring so they behave as a distributed cross-
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connect switch. The SDH ring is described in detail below (b) An SDH 4/1 DXC - For larger sites, an NEC SXS-W 4/1 digital cross-
connect (DXC) switch can be used to support the video multicasting and other digital switching requirements of a local exchange 6 5 (c) An ATM Multicast Switch - An asynchronous transfer mode (ATM)
switch which supports both multicast and point-to-point connections (d) An NEC Video Distribution Switch - The NEC video distribution switch described in the specification of NEC Australia Pty Ltd's copending International patent application
The output cross-connect channels are fed into the m ADSL exchange units 12, as shown in Figure 2, which include ADSL modems The switch 8 and controller 10 are provided by one of the cross-connect switching options described above, which receives n channels from the transmission network 5 using an SDH NE 22 and all control data, such as billing and OAM data, 15 is passed between the SDH NE 22 and the ADSL exchange units 12 on a control channel 24 Local switching is performed by the cross-connect unit 23 in response to signals on a switch control channel 26 which is supported by a switching controller, such as the CPU, of the ADSL exchange units 12
At the customer premises, the ADSL customer unit 16 is able to receive and demodulate the downstream high speed digital video signals, together with any signals received on the low speed control channel. The customer unit 16 is also able to modulate and transmit on the control channel customer connection requests and status information in the upstream direcUon to the exchange 6 The customer unit 6 includes POTS splitters for transparently combining and 25 extracting telephone signals on the line 14 for the customer's telephone 23 The customer unit 16 includes an ADSL modem and is preferably as described in the specification of NEC Australia Pty LtcL's co-pending International patent application The ADSL customer unit 16 connects to the customer set-top unit (STU) 30 The STU 30 connects to a customer's television and allows customers access to the Pay TV, VOD, PPV, and other services which are provided on the 30 ADSL line 14 The STU 30 decodes MPEG video and audio for playing on connected TV and/or video and hi-fi equipment The STU 30 can, if desired, be integrated with the ADSL customer
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WO 97/09826 PCT/AU96/00560
umt 16
To implement the SDH ADM ring, the SDH inter-exchange network (IEN) 5 can be extended into the local exchange 6 SDH based switching can be implemented using add-drop 5 multiplexers (ADMs) or 4/1 DXC equipment In addition, the switching can be performed by either connecting equipment directly as part of the IEN 5 or externally linking the equipment to tfcelEN 5 The two alternatives are illustrated in Figures 3 and 4 For the first configuration of Figure 3, the ADSL equipment 12 is connected directly to network elements 32 of the IEN 5 which support and combine service distribution and customer switching requirements on the 10 channels 24 and 26 The configuration is a cost effecuve solution for small installations or tnal systems The configuration illustrated in Figure 4 uses an SDH nng 34 of SDH network elements 36 at the local exchange 6 for switching of channels using the switch control channel 26 The SDH nng 34 is connected to an SDH network element 38 which forms part of the SDH IEN 5 The SDH NE 38 supports the control channel 24 The configuration of Figure 4 separates the 15 subnetworks used for services distribution and for customer channel switching The configuration is also more easily upgradable Both configurations employ the NEC IS-3000 ADSL exchange units 12 descnbed in the specification of NEC Australia Pty Ltd's co-pending International patent application The ADSL exchange units 12 provide interfaces between the ITU G 703 standard output interfaces of the SDH equipment 36 and 38 and the ADSL lines 14 The 20 exchange units 12 also support the 2 Mbit/s control channel 24 for communication between the head netwoik element 38 and the exchange units 12, and in turn the ADSL customer unit 16 and STUs 30 The exchange units 12 also provide support for one or more ADM switch control lines 26 for the SDH NEs
The control channel 24 is a bidirectional 2 Mbit/s signal which uses HDLC framed messages The messages provide communications links between
0) The exchange units 12 and the management system 20
(u) The ADSL customer unit 16 and the management system 20
(111) The STUs 30 and the management system 20
(iv) The STUs 30 and the service provider equipment 4
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Additional control channels 24 can be used as customer application bandwidth requirements increase The control channels 24 are terminated in the regional NE 38 of the IEN S where messages are then routed to the appropriate management system or provider equipment 4 For the channel change request received from the customers by the exchange units 12, the 5 exchange units 12 separate the requests from the upstream control channel 24 if the requests are for a channel already received by the local exchange 6 The requests are formatted into suitable commands for the SDH NEs 36 and placed on the switch channel 26
The following add-drop multiplexers can be used for customer channel switching, each 10 of which are commercially available units
SMS-150A STM-1 (155 Mbit/s) ADM with a maximum of 63 * 2 Mbit/s tributary interfaces
SMS-600W STM-4 (622 Mbit/s) wideband ADM with a maximum of 126 * 2 Mbit/s tributary interfaces An additional 126 * 2 Mbit/s tributaries can be added 15 by using a SMS-150T2 expansion subrack.
SMS-2500A STM-16 (2500 Mbit/s) ADM with a maximum of 16 * STM-1 (or 4 x STM-4) tributary interfaces. Additional SMS-600W or SMS-150As may be used to access 2 Mbit/s tributaries SMS-2500W STM-16 (2500 Mbit/s) wideband ADM with a maximum of 252 * 2 20 Mbit/s tributaries Additional SMS-600Ws may be used to access extra
2 Mbit/s tributaries
The following configuration examples are described hereinafter (i) STM-1 service distribution, IEN based customer channel switching;
(ii) STM-4 service distribution, IEN based customer channel switching, and
(in) STM-4 service distribution, local exchange ring based customer channel switching.
In the STM-1 IEN based customer channel switching configuration, NEC's SMS-150A 30 unit 40 can be used for video signal distribution and switching The configuration supports small to medium sized Pay TV and VOD networks with 63 x 2 Mbit/s per second customers being
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supported for each SMS-150A 40 The SMS-150A units 40 are connected to form an STM-1 fibre nng in order to connect one or more local exchanges 6, as shown in Figure 5, to a regional hub site The SMS units 40 receive video interactive services from the IEN 5 and support both the switch control channel 26 and the 2 Mbit/s control channel 24 Each unit 40 is connected to 5 the ADSL exchange units 12 to support 63 * 2 Mbit/s downstream channels Each fibre line of the STM-1 nng 42 supported by the SMS umts 40 is a unidirectional self-healing nng wi'h path protection (USHR-P), also referred to as a path protection switched (PPS) nng This ensures customer traffic is maintained in the event of single or dual fibre cuts or in the case of total failure in a node of the nng To increase the number of customers supported, additional SMS-150A 10 units 40 can be added to the nng 42 without disrupting customer traffic
The ADX unit 50 of the SMS-150A unit 40, as shown in Figure 6, provides a non-blocking cross-connect function at a 2 Mbit/s (VC-12) or 34/45 Mbit/s (VC-3) level The ADX unit 50 permits point-to-point or point-to-multipoint switch connections to be established 15 simultaneously, which may be unidirectional or bidirectional Signals of different levels cannot be cross-connected, i e connection of a 2 Mbit/s steam to a 34 Mbit/s The cross-connections performed by the ADX unit 50 include
(i) Unidirectional connection from a line side channel received from the IEN
nng 42 to one or more tributary channels sent on the 2 Mbit/s lines 44 connected 20 to the ADSL exchange umts 12
(u) Bidirectional cross-connection from a line channel to a tnbutary channel
(ill) Bidirectional cross-connection between line side channels
(iv) Unidirectional connection from an input tributary channel to one or more output tnbutary channels, for local insertion of content, if desired
Configuration commands for the ADX unit 50 are generated internally by an ACM unit 52 of the SMS unit 40 The ACM unit 52 receives its commands from a local control (craft) terminal 53 (LCT) and/or a remotely located operations system (OS), such as the NEC networked craft terminal (NCT) The OS can be connected to the SMS unit 40 by a local LAN 30 connection or remotely connected through the IEN 5 to a management centre Connection through the IEN 5 is achieved using a communications channel in the framing overhead of the
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WO 97/09826 PCT/AU96/00560
STNl-1 signal OS communication uses a standard seven lay® OSI protocol which is processed by the MCI unit 54 of the SMS unit 40 The OS can perform al' administration, management and provisional control for each network element 40 This enaoies a single management system to be used for service distribution and local exchange customer switching in response to the signals 5 on the control channel 24 and the switch control 26 The OS can form part of the OAM system 20 to also connect to the control channel 24 The SMS un *0 supports simultaneous command entry from both the OS and LCT This enables the Uae of the N£C IS-3000 exchange units 12 to provide LCT formats which control commands on the switch contra! channel 26 for input into the SMS unit 40 The LCT command format also allows for control of remote SMS units 40 10 attached through SDH bearers 42 The LCT interface 53 uses a binary message protocol which allows for fast input and processing of commands by the ACM unit 52, as compared to implementations which may use a more complex CMISE based interface The message protocol used supports the performance required to respond to a large number of cross-connect change operations which may be issued m a video broadcast application. In simultaneously supporting 15 point-to-point and muhic * operations, the SMS unit 40 can be shared between video and other IEN traffic for efficient traffic distribution. The SMS unit 40 illustrated in Figure 6 includes an optionally redundant cross-connection matrix
For STM-4 IEN based customer channel switching, NEC's SMS-600W units 60, as 20 shown in Figure 7, are used for service distribution and switching and support of the switch channel 26 and the control channel 24 This configuration is suitable for medium to large sized video signal distribution networks Each SMS-600W unit 60 can support 252 * 2 Mbit/s downstream channels 62 to the ADSL units 12 The SMS units 60 receive services from the IEN 5 and perform customer channel switching An STM-4 fibre nng 66 is used to connect one or 25 more local exchanges 6, and the nng 66 is supported by the SMS umts 60 The nng 66 is a unidirectional self-healing nng with path protection (USHR-P) Additional SMS units 60 can be added to the nng 66 without disrupting customer traffic
The ADX4W unit 68 of the SMS-600W unit 60, as shown m Figure 8, provides a non-30 blocking cross-connection function at 2,34 or 140 Mbit/s levels The unit 68 permits point-to-point or point-to-multipoint switch connections to be established simultaneously which may be
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PCT/AL'96/00560
unidirectional or bidirectional Only signals of the same level can be cross-connected The cross-connections which can be performed by the ADX4W unit 68 are illustrated in Figure 9 and labelled A to D which represent the following
A Unidirectional connection from a line side channel on the nng 66 to one
or more tnbutary channels on the downstream customer lines 62
B Unidirectional connection from a tributary input to one or more tributary outputs
C Bidirectional cross-connection between line channels
D Bidirectional cross-connection from a line channel to a tnbutary channel
Configuration commands to the ADX4W unit 68 are issued internally by the ACM unit 70 The ACM unit 70 receives its commands from a locally attached control (craft) terminal (LCT) 53 and/or a remotely located operations system (OS) such as the NEC network craft terminal (NCT) The OS can be attached to the SMS-600W 60 by a local LAN connection or 15 remotely connected through the IEN 5 to a management centre A connection through the IEN 5 is achieved by using a communications channel in the framing overhead of the STM-4 signal OS communication uses a standard seven layer OSI protocol which is processed by the SMS-600W MCI unit 72 The OS performs all administration, management and provisioning control for each NE 60 This provides the benefit of having a single management system for video 20 distnbution and local exchange video channel switching The SMS-600W 60 also supports simultaneous command entry from both the OS and the LCT This allows the NEC IS-3000 EUs 12 to input LCT format switch control commands into the SMS-600W 60 The LCT command format also allows for control of remote SMS-600W units 60 attached through SDH bearers 66 The LCT interface 53 uses a binary message protocol, which allows for the fast input and 25 processing of commands by the ACM unit 70, as compared to implementations using a more complex CMISE based interface The protocol supports the performance required to respond to the large number of cross-connect change operations issued in a video broadcast application The SMS unit 60 simultaneously supports point-to-point and multicast operations, and as such, an SMS unit 60 can be shared between video and other IEN traffic thereby providing for efficient 30 traffic distnbution. The block diagram of Figure 8 includes optionally redundant components
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An STM-4 local exchange nng distribution switch configuration, as shown in Figure 10, is for use when a large number of local exchanges 6 are attached to a regional service distnbution nng 74 and each exchange 6 is required to support a large number of customers The architecture illustrated in Figure 10, and in Figure 4, separates the IEN transmission equipment from the 5 customer channel switching equipment, which also has advantages for future capacity upgrades The architecture can be applied to a distnbution system which uses the SMS-150A units 40 or the SMS-600W units 60 Distnbution using the SMS-600W units 60 is discussed hereinafter
In the local exchange 6, a first SMS-600W unit 76 is used to collect services from the 10 IEN nng 74, and drop four STM-1 signals to a second SMS-600W unit 78 if support for 252 services is required If support of only up to 126 services is required, then two STM-1 signals can be passed to the second SMS-600W unit 78, as shown in Figure 11, and 126 * 2 Mbit/s customer channels can be dropped to the second unit 78 Third and fourth SMS-600W units 80 and 82 are used to form a three node self-healing nng 34 with the second SMS-600W unit 78 15 Each of the units 78 to 82 m the ring 34 can switch up to 252 * 2 Mbit/s customer channels, as previously described For additional secunty against complete failure of the first or second units 76 and 78, the architecture can be modified to support a dual head-end linked nng 84, as shown in Figure 12 by adding a fourth SMS-600W unit 84 in the EEN nng 74, which can drop the 126 x 2 Mbit/s channels to the third SMS-600W unit 80 of the local exchange nng 84 A high level 20 of unit protection by the SDH network elements may not be required in this instance which would result in substantial cost savings
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Intellectual
Property Office of New Zealand
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PCT/AU96/00S60
8 A video services distribution system including a video switch for receiving a plurality of video service channels from a telecommunications network, said video switch having a selection unit for multicasting said service channels to customer video channels, and 5 modulating units for modulating signals on said customer video channels, received from said video switch, for transmission on telecommunication lines to respective customer units
9 A video services distribution system as claimed in claim 8, including a bidirectional data channel between said video switch and said modulating units for transmitting control data
between said video switch and said customer units, said control data being modulated with the signals on said customer video channels by said modulating units and said customer umts for transmission on said telecommunications lines
A video services distribution system as claimed in claim 9, wherein said selection unit 15 executes point-to-point or point-to-multipoint connections of said service channels to said customer video channels on the basis of channel select data received on said bidirectional data channel
11 A video services distnbution system as claimed in claim 10, wherein said video switch 20 and modulating umts are each included in a plurality of local telecommunications exchanges, and said video service channels are broadcast to said local exchanges
12 A video services distnbution system as claimed in claim 10 or 11, wherein said modulating units and customer units are ADSL umts
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Intellectual
Property Office of New Zealand
Te Pou Rahul Hanga Hou
DAMAGED OR MISSING PAGE
PLEASE CONTACT IPONZ
email iponz@iponz govt nz telephone +64-4-560 1600 facsimile +64-4-568 0747
Office Hours 8 30am to 5 00pm, Monday - Friday