Satellite Packet Communication - Multiple Access Protocols and Performance

Satellite communication systems have traditionally been designed for voice traffic. Multiple access protocols for conflict resolution have typically been channel-oriented with either fixed or demand assignment. Data communications, however, have much more diverse traffic characteristics and transmission requirements than voice communications. We present in this paper an overview of two major categories of packet-oriented multiple access protocols: contention and reservation protocols. A traffic model suitable for the data communications environment is first introduced. A key element in this model is user-specified message delay constraints. Our primary performance measure of a protocol is the channel throughput versus average message delay tradeoff characteristic. The main attributes of the two categories of packet-oriented protocols are discussed. Four specific contention protocols are described and their performance characteristics are examined. Design considerations of the two important components of reservation protocols, reservation channel and distributed global queue, are discussed. Three reservation protocols with distributed control are described. Finally the performance of channel-oriented protocols and the two classes of packet-oriented protocols are compared using a variety of traffic models.