Random access for a multibeam satellite with dynamic transponder switching

Abstract

A multibeam satellite communications network serving multiple zones with S-ALOHA random access uplinks and dynamically switched transponders in the downlinks is studied. The overhead of switching transponders between ones may degrade the performance of the system significantly. Two different strategies are introduced and studied. In the guard time strategy, each slot time is equal to the packet transmission time plus the transponder switching time, allowing the transponder to be pointed to a new zone at the beginning of each slot. In the idle waiting strategy, each slot time is equal to the packet transmission time. If a transponder is switched to a new zone, it will take k slot time where k is the smallest integer greater than the switching time divided by the slot time. The throughputs of these two strategies are analyzed and compared.