Distributions of packet delay and interdeparture time in slotted ALOHA and carrier sense multiple access

Abstract

Packet communication systems of the multiaccess/broadcast type, in which all communicating devices share a common channel that is multiaecessed in some random fashion, are considered. Among the various muhraecess schemes known, two prominent ones are considered: slotted ALOHA and Carrier Sense Multiple Access (CSMA). Existing analysis of these schemes has led to the determination of the average channel performance m terms of average throughput and average packet delay. This was achieved by formulating Markovian models for these channels with finite populations of users, each with a single packet buffer. Unfortunately, average performance is not adequate when designing communication systems intended for real-tune applicauons, such as digitized speech, or when analyzing multihop packet radio networks, and the analysis has to be extended so as to provide delay distributions. Using the same Markovian models, the distributions of packet delay and interdeparture time for slotted ALOHA and CSMA channels are derived, and expressions for their moments are given.