Stability, Throughput, and Delay of Asynchronous Selective Reject ALOHA

An analytical performance evaluation model is presented for selective reject (SREJ) ALOHA, a recently proposed high-capacity protocol for unslotted channels with high propagation delay. SREJALOHA approaches the theoretical asynchronous multiaccess throughput limit of 0.368 for fixed or variable length message traffic, using subpacketization of messages in conjunction with a selective reject retransmission policy. A finite user flow equilibrium-based model for SREJ-ALOHA with variable length messages is derived and used to characterize stability, throughput, and delay. Particular attention is given to the development of a stability analysis methodology for unslotted ALOHA-type protocols with variable length transmissions. Numerical results based on a satellite channel example are presented to demonstrate the significant performance advantages offered by SREJ-ALOHA, even after accounting for realistic subpacket overheads.