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Future satellites should be able to support not only circuit switched data communication, such as voice and video traffic, but also bursty traffic based on connectionless data communication generated in (High Speed) LAN. Further they should support the low power stations, such as VSAT-Stations or mobile users. The satellite could be used as a network nodc in Store-and-Forward networks or as a switchboard in a telephone network to reduce round trip dclay in satcllite links. These requirements lead to the dcsign of future on-boardprocessing satellites. While current satellites are designcd for circuit switched data communications, future satellites will be based on hybrid circuit/packet switches or advanced fast packet switches. These will be combined with suitable network management and congestion control techniques to ensure proper availability and dclay characteristics for delay sensitive tnftic.

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No abstract

On systems consisting of packet switched networks (e.g. LANs, HSLANs and ATM/BISDN) which are linked over satellite, there are packet losses due to buffer overJEow at bridges and routers as well as bit errors on the satellite link. The resulting high error probability requires error correction methods, which are simple and effective in terms of throughput and memory requirements. For packet switched communications, quite a number of ARQ (Automatic Repeat Request) protocols have been designed which are able to cope with stringent memory requirements, but they either lack safety at high block error rates, or they require a large bandwidth due to low throughput. In this paper, we will introduce a simple and effective strategy (called Stutter-XOR or SXOR strategy) to increase throughput of exisiting protocols. In contrast to existing hybrid schemes (combinations of ARQ and forward error correction), it does not only correct bit errors, but also handles block losses. This is achieved by sending additional blocks, so called XOR blocks, which are created by combining other blocks using the XOR (modulo 2 addition) operation. We developed several variants of this strategy. Two of them will be evaluated here by means of analysis and simulation.