Analysis of an Exponential Backoff Algorithm for Multipacket Reception Slotted ALOHA Systems

Abstract

This paper examines throughput and delay performances of multipacket reception (MPR) slotted ALOHA systems with the exponential backoff (EB) algorithm which consists of an initial transmission probability, exponentially decaying factor and a maximum number of backoff stages. We assume a finite population model and the saturated traffic condition where every terminal always has a packet to transmit. To show the general impacts of the EB algorithm's parameters on the system performance, we consider two MPR channels. In the first channel, all the packets transmitted cannot be successfully received, if the number of packets simultaneously transmitted exceeds a predefined threshold. In the second one, some of packets concurrently transmitted can be probabilistically received (captured). In numerical studies, we show how to adjust the parameters of EB algorithm given the MPR channel in order to achieve close-to-maximal system throughput, and discuss fair channel use.