MULTIMEDIA APPLICATIONS OF THE INTEGRATED BROADCAST INTERACTION SYSTEM (IBIS) Sergio Chacón (1), José Luis Casas (1), Asís Cal (1), Rafael Rey (1), Josep Prat (1), Africa Rodriguez (1) Javier de la Plaza (1), Carlos Miguel Nieto (2), Fco. Javier Ruiz Piñar (2) INTRODUCTION (1) ALCATEL ESPACIO, C/ Einstein 7, 28760 Tres Cantos (Spain), sergio.chacon@space.alcatel.es (2) ETSIT Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain), cmn@dit.upm.es The Integrated Broadcast Interaction System is implemented with a fully regenerative On-Board Processor (Alcatel 9343) designed to provide direct (distributed) [1] compliant satellite access for individual digital video broadcasters, Internet Service Providers, and multimedia users. Transparent Transparent Figure 1: IBIS System Concept IBIS Regenerative Cross-Connected Multi-Spot IBIS integrates two existing satellite transmission standards: and [2]. Both of which are used in transparent satellites without any regeneration on board. IBIS combines these two standards into a single regenerative multi-spot satellite system allowing for full cross-connectivity between the different uplink and downlink beams. The uplink will be compliant with the standard. This fact will allow users to use standard stations, which will be widespread and relatively inexpensive in the future thanks to the standardization effort of terminal manufacturers and broadcast satellite operators. Individual users and broadcasters will be able to access the satellite on any of several uplink coverage footprints illuminated by the satellite, using multiple frequencies, within a TDMA frame, and at several transmission rates (multiple-rate MF-TDMA or Multiple Frequency Time Division Multiple Access). The Downlink will be fully compliant with the Standard, including all the possible convolutional rates [3]. This will allow users to take advantage of the economies of scale and the performance of standard commercial receivers, which are widespread across Europe today. A key feature of the system will be the capacity to route data on any of the uplink coverage footprints on to any combination of downlink coverage footprints; the system will implement full cross-connectivity between uplink and downlink footprints. In order to accomplish all this, contributions from all compliant uplink users must be demultiplexed, demodulated, and decoded and then switched and re-multiplexed into the compliant downlink data streams as required by users. On board switching and multiplexing will take place in accordance with a dynamic multiplexer table. Each downlink has associated with it a multiplexing table. It will be possible to reconfigure this table
very quickly through a regenerative signaling channel allowing very fast circuit switching at packet level on-board. In case of emergency the standard Telecommand (TM/TC) channel will be used to configure the payload. A9343 DOWNLINK #N TDMA DOWNLINK #2 UPLINK COVERAGE #1 UPLINK FDMA DOWNLINK #1 DOWNLINK COVERAGE #2 UPLINK COVERAGE #2 DOWNLINK COVERAGE #1 Figure 2: Multi-Beam MF-TDMA Compliant Uplink and Multi-Beam Downlink; Allowing for full Cross-Connectivity between Uplink and Dowlink Beams THE IBIS COMMUNICATION MODEL The Communication Model as is defined in the Standard is shown in Figure 3. The Broadcast Channel is defined as a unidirectional channel from the Service Provider to the User, while the Interaction Channel is defined as a bi-directional channel used to exchange information between the Service Provider and the User or between Users. SATELLITE USER SERVICE PROVIDER Service Provider Processing Broadcast Ch. Interaction Ch. USER Figure 3: The Communication Model In the IBIS System, both broadcast channel and interaction channel will be compliant on the uplink and compliant on the Downlink. Physically they are the same. The only thing that distinguishes them is the information content they carry. In the IP world, the interaction channel becomes the only channel because the broadcast channel is imbedded in the interaction channel. The signaling channel is illustrated in figure 4. This channel is used for fast configuration of the satellite and general OBP management. It is also used by the Service Provider or the Prosumer (in this case they are just users) to communicate with the NCC (Network Control Center). This channel is used for the Logon & Synchronism Procedures, and for resource requests. USER SATELLITE SERVICE PROVIDER Service Provider Processing Signaling Channel USER NETWORK CONTROL Network Operation Figure 4: The IBIS Signaling Channel
The basic symmetry among users along with centralised resource management will make the system ideally suited for true mesh networking with a single hop through the satellite combined with the advantages of signalling through a star topology. THE IBIS COMPETITIVE EDGE Full cross-connectivity between uplink and downlink footprints IBIS has the capacity to route data on any of the uplink coverage footprints on to any combination of downlink coverage footprints on a per need basis. One packet may be routed to one downlink while the next packet may be routed to a different downlink or a combination of downlinks. The onboard processor combines the individual contributions into one or several downlinks as required by users. Dedicated Unicast, Multicast, and Broadcast Bandwidth On-Demand IBIS will provide users with a high capacity dedicated link supporting real-time services on a flexible per-need basis, taking advantage of the inherent satellite broadcast capacity and the OBP s full cross-connectivity between uplink and downlink spots. A Single Hop from Source to Destination allows Real-Time Services The transparent satellite reference Model requires two satellite hops. This means that the propagation delay is large enough to preclude real-time applications such as VoIP or Videoconferencing. The IBIS OBP solution will allow real-time services through point-to-point, point-to-multipoint, multipoint-to-point, and multipoint-to-multipoint communications in a single hop. Propagation delay is reduced enough so that real-time applications such as VoIP and Videoconferencing will become possible over the IBIS regenerative satellite network. A Single Hop saves Bandwith as compared to the Reference Model An OBP solution such as IBIS requires half the bandwidth than a double-hop transparent system, where bandwidth must be reserved for two uplink and two downlink paths (required by the two hops). Onboard Regeneration The user transmitter requirements can also be relaxed when we take advantage of the regenerative gain provided by the IBIS OBP Solution. In addition, with a single carrier on the downlink, less Back-off is required on the on-board channel power amplifier, thus, reducing amplifier complexity an consumption. Single-Hop Mesh networking combined signaling through a star topology The basic symmetry among users along with centralized resource management will make the system ideally suited for true mesh networking with a single hop through the satellite combined with the advantages of signaling through a star topology. Inexpensive User Terminals Thanks to /S compatibility, regenerative gain, and the minimum transmission rate (Rs), user terminal costs will be reduced. MPEG2-TS Based Transport Layer The IBIS system is compliant with the standard on the downlink and the standard on the uplink. is based on a MPEG2-TS transport layer. In order to avoid protocol translation or re-encapsulation on board, the IBIS compliant uplink transport layer will be based on MPEG2-TS. Hence, IBIS OBP switching will be based on MPEG2-TS packets. Uplink and downlink communication in IBIS will be based on the protocol stacks shown in figure 5.
1R1 1R2 1R3 1R4 1R5 1R6 1R7 1R8 1R9 1R10 1R11 1R12 1R13 1R14 1R 15 1R 16 1R49 1R50 1R51 1R52 1R53 1R54 1R55 1R56 1R57 1R58 1R59 1R60 1R61 1R62 1R 63 1R 64 1R 65 1R 66 1R 67 1R 68 1R69 1R70 1R71 1R72 2R1 2R2 2R3 2R4 2R5 2R6 2R7 2R8 2R25 2R26 2R27 2R28 2R29 2R30 2R31 2R32 2R33 2R34 2R35 2R36 4R1 4R2 4R3 4R4 4R13 4R14 4R15 4R16 4R17 4R18 8R1 8R2 8R7 8R8 8R9 16R1 16R4 IBIS-OBP MCDDD SWITCH & MUX CODING Control -TX -RX Appli TCP/ UDP IP IP IP Appli TCP/ UDP IP 802.3 802.3 MPE MPEG2-TS MPE MPEG2-TS 802.3 802.3 10 base T 10 base T Air interface 10 base T 10 base T Figure 5. IBIS Traffic Protocol Stacks IBIS Transmission Rate Flexibility IBIS supports a wide range of uplink transmission rates, going down as low as 327 ksps (QPSK symbols per second) and up to 5244 ksps (allowing for information rates up to 8294 kbps ). This flexibility allows for a wide range of IBIS users in accordance with their transmission requirements. Multimedia users with low transmission requirements can take advantage of the lower transmission rates to reduce the cost of their terminal s power amplifier and antenna. A large corporation can take advantage of mid-range transmission rates to interconnect their LANs or a TV broadcaster can take advantage of the higher transmission rates to broadcast several programs. 36 MHz 36 MHz 1R1 1R2 1R3 1R4 1R5 1R6 1R7 1R8 1R9 1R10 1R111R12 1R131R14 1R151R16 8R7 8R8 1R65 1R66 1R67 1R68 1R69 1R70 1R71 1R72 2R25 2R26 2R27 2R28 2R29 2R30 2R31 2R32 4R13 4R14 4R15 4R16 2R33 2R34 2R35 2R36 4R17 4R18 16R4 8R9 Figure 5. A flexible uplink frequency plan allows a wide range of uplink transmission rates MF-TDMA Bandwidth on demand In addition to transmission rate flexibility, transmission carriers can be segmented in time. Time is divided into superframes, frames, and timeslots. A superframe may contain anywhere from one to 32 frames, while frames are subdivided into transmission timeslots. Individual timeslots within a frame can be allocated to individual users. Within the same superframe, a timeslot can be allocated to one user during one frame while the same resource can be allocated to another user during the next frame. This allows bandwidth to be allocated to users on-demand in accordance with their uplink transmission requirements. In addition, various burst sizes within a frame can be assigned to users in accordance with their bandwidth requirements (see figure below).
1 Frame = approx. 69ms 1 TRF Burst /Frame 2 TRF Burst /Frame 4 TRF Burst /Frame 6 TRF Burst /Frame 18 TRF Burst /Frame Combinations Figure 5. Flexible frame configuration allows bandwidth to be allocated based on individual user requirements Fast Circuit Switching Onboard at Packet Level The on-board switching matrix can be reconfigured on a frame by frame basis, that is to say every 69ms or more than 14 times per second. This allows the Network Control Center (NCC) to modify network resource allocations and onboard routing on a very dynamic basis (from one frame to the next). Combined with MF-TDMA Bandwidth on demand, Fast Circuit Switching on board allows individual users to optimize bandwidth utilization in accordance with their routing needs. Real-Time Services and IBIS MF-TDMA Resource Granularity Real-time services such as VoIP or Videoconferencing require reduced propagation delay and jitter. The IBIS system MF-TDMA resource granularity is such that real-time services can be supported in an effective and efficient manner. In IBIS as in any system, MF-TDMA resources are segmented into frames. Frame duration is approximately 69 ms and in every frame, the minimum resource that can be allocated is a one MPEG2-TS packet burst. For real-time applications this introduces a jitter of approximately 60 ms, which in most cases is well within the tolerable range. One MPEG2-TS Packet per frame corresponds to a 21 kbps real-time channel, which can provide a 14.4 kbps service for the application layer (VoIP). With an 8 kbps CODEC such as the G.729, a 14 kbps channel is about right to absorb the conversation traffic, while leaving resources for best-effort services to be aggregated along with the VoIP conversation. SUPPORTED SERVICES AND SCENARIOS Modern multimedia environments require connections which make a flexible use of bandwidth. Current point-to-point guaranteed bandwidth solutions such as ISDN provide fixed bandwidth channels instead of flexible channels sized in accordance with the user s needs. IBIS combines guaranteed bandwidth on-demand with dynamic connections between users located anywhere within the IBIS coverage. Services and applications contemplated in IBIS are: Real-Time services and applications: VoIP and Videoconferencing LAN Interconnection (Virtual Private Network) Interactive Digital TV and Tele-shopping ISP Access IP Multicast and IP Streaming Distributed TV Broadcast NVoD Push Services Interactive Gaming and Distributed Processing Teleducation and Telemedicine
All of these applications require flexible on-board bandwidth resource allocation and packet level switching. Figure 7 illustrates how the multi-beam IBIS system allocates MF-TDMA resources to the different QoS Queues supported by the per destination Downlink. In this example, a four packet (MPEG2-TS) MF-TDMA resource is allocated to an supporting a LAN. The different users on the LAN need to communicate with other users located on different downlinks. The IBIS OBP will be able to route information on a packet by packet basis to the different downlinks as required by the LAN users needs. As the needs change, the IBIS OBP switching matrix will change on a real time basis. Freq. MF-TDMA RESOURCE ALLOCATION time Channel_id_3 Channel_id_1 Channel_id_2 QoS type A QoS type A QoS type A D/L #2 D/L #3 QoS type B QoS type B QoS type B LAN QoS type C QoS type C QoS type C QUEUING FOR QUEUING FOR QUEUING FOR ROUTE #1 ROUTE #2 ROUTE #3 D/L #1 Figure 7: On Board Packet Level Switching The IBIS OBP (Alcatel 9343) is designed to provide physical support for IP Multicast applications, such as IP streaming and push services, over several or all of the satellite IBIS downlink beams as shown in the figure below. A9343 DOWNLINK DOWNLINK UPLINK DOWNLINK Figure 8: Physical Support for IP Multicast Applications A number of scenarios exist where these system features make IBIS a serious contender in the telecommunication market. Three such scenarios are described in this paper: the Corporate Network / LAN Interconnection, the Neighborhood/SMATV (Satellite Master Antenna TV), or the SO-HO (Small Office / Home Office). Corporate Network / LAN Interconnection Corporations will see in the IBIS system a cost effective solution to provide LAN interconnection among their geographically distributed sites. Additional services such as VoIP and Videoconferencing among sites will also make the system an attractive solution for corporations. The figure below illustrates the corporate network scenario.
Corporate Facilities Corporate Central 1 Servers (WEB,E-mail, etc.) Internet N Figure 9. Corporate Network with Central and Client Facilities In the corporate scenario, we can identify at least two types of corporate facilities: Central Facility and Client Facility. In the Central Facility are located all the applications servers include Internet access proxy/firewall, web server, and E- mail server. There could be N Client Facilities accessing the different servers through their s. In the corporate network scenario true mesh networking comes to life. Any one corporate site may establish a connection with any other site through a single satellite hop. The connection is set up in accordance with the user bandwidth requirements on-demand. In comparison with a dedicated terrestrial link among sites, where the link capacity is set, in the IBIS mesh, link capacity among sites is dynamically based on demand. Neighborhood (SMATV) An example of an SMATV environment might be a building with 100 households served by a single. The SMATV scenario provides for a combination of mesh and star networking. A group of users may have signed up with one ISP (Internet Service Provider) while another group of users in the same building may have signed up with a different ISP, perhaps located in a different downlink. At the same time some other users may be using a TV return channel in a third downlink while others might be involved in several VoIP conversations. In addition, IBIS includes the possibility where content requested by users may be delivered by an ISP through a transparent satellite channel. TV Broadcast Center Feeder ISP Internet Figure 10. Neighborhood /SMATV Scenario regenerative transparent
Small Office/Home Office (SO-HO) Small Office/Home Office refers to the small business or business-at-home user which requires a connection to an ISP, the main office LAN, and perhaps other SO-HOs. Again, the IBIS advantage is provided by mesh networking combined with dynamic bandwidth on demand. In addition to ISP access or connection with the office LAN, applications such as VoIP, videoconferencing, IP streaming, push services, or interactive TV will take advantage of IBIS bandwidth on demand and single-hop mesh networking. Main Office SO-HO Networks 1 ISP Internet Figure 11. SO-HO Scenario N CONCLUSION IBIS combines and into a single regenerative multi-spot satellite system allowing for full crossconnectivity between the different uplink and downlink beams. IBIS is implemented with a fully regenerative On-Board Processor (Alcatel 9343) designed to provide direct (distributed) compliant satellite access for individual digital video broadcasters, Internet Service Providers, and multimedia users. In addition, the Alcatel 9343 is designed to provide physical support for IP Multicast applications, such as IP streaming and push services, over several or all of the satellite IBIS downlink beams. IBIS will provide users with a high capacity dedicated link supporting real-time services on a flexible real-time per-need basis, taking advantage of the inherent satellite broadcast capacity and the OBP s (Alcatel 9343) full cross-connectivity between uplink and downlink spots. The IBIS OBP will be able to route information on a packet by packet basis to the different downlinks as required by the users needs. As the needs change, the IBIS OBP switching matrix will change on a real time basis. REFERENCES [1] EN 301 790, DVB Interaction channel for satellite distribution systems, ver 1.2.2, ETSI [2] EN 301 192, DVB specification for data broadcasting, ver 1.2.1, ETSI [3] EN 300 421, DVB Framing structure, channel coding and modulation 11/12 Ghz satellite services, ver 1.1.2, ETSI [4] EN 300 468, DVB Specification for Service Information (SI) in DVB systems, ver 1.4.1, ETSI [5] M. Lamarca et al., DVB-Forward: A Digital Television / Internet Payload, 19 th International Communications Satellite Systems Conference and Exhibit, American Institute of Aeronautics and Astronautics, Toulouse, France, 17-20 April 2001. [6] Y. Le Roy et al., The Alcatel 9343 DVB-OBP Product: An On-Board Processor for Digital Television and Internet Data, Seventh International Workshop on Digital Signal Processing Techniques for Space Communications, Sesimbra, Portugal,, 1-3 October 2001, in press.