Performance of Multibeam Packet Satellite Systems with Conflict Free Scheduling

The concept of a multibeam satellite system With on-board processing and memory is studied. In this system multiple slotted ALOHA uplinks carry the traffic to the satellite. Packets are accepted at the satellite, when memory is available, and are routed to their destination zones using a TDM protocol. We present a model which can be used to evaluate a satellite system with conflict-free scheduling, i.e., a system in which several packets can be simultaneously chosen for downlink transmissions, given each earth zone is served by at most one satellite transponder in each slot. We compute the system throughput, packet delays, and buffer overflow probabilities for a general configuration. It is shown that for some configurations the one beam per zone restriction can have a significant effect on the system performance. The presented model can be also used to evaluate satellite systems when this restriction is removed and to evaluate a variety of other satellite systems.