Computer data communication

Abstract

Methods for data communication using a packet switching technology over a slotted satellite channel are proposed and studied. The basic model assumes an input source from many independent lowrate stations which use the channel in a multiple random access mode. When simultaneous transmissions interfere with one another, all of the conflicting packets are destroyed and must be retransmitted after some random delay. The message delay vs. channel throughput tradeoff is studied for various random delay policies. The dynamic behavior and stability of the model is analyzed. The channel is locally stable if the traffic rate is less than 1. Control policies are studied to return the channel from an unstable state to a stable state. The maximum channel throughput for this model (corresponding to a channel traffic rate of 1) is limited to below 1/e. Two other models are studied in which the channel throughput exceeds 1/e. The first consists of the addition of one or more high-rate buffered stations to the previous model. In this case the increase in overall channel throughput is at the expense of degraded performance for the low-rate stations. The second involves using a fraction of the channel capacity for the stations to make reservations. In this case, the increase in channel through put is at the expense of longer message delays.