A ring model for local mobile radio communications with variable packet length

Abstract

This thesis presents an analysis of the performance of a local mobile radio communications system utilizing the Aloha random access protocol with variable length packets. The capture phenomenon due to the nearfar effect that enhances the performance of the system is investigated. A tagged packet will capture the base station if its signal-to-interference ratio exceeds a threshold gamma sub zero. Because of the nearfar effect, users near the base station typically have a stronger signal than those farther away. A multiple ring model is used to alleviate this problem. Users in one ring employ different retransmission strategy from those in other rings. A shorter retransmission delay is allocated to users in rings farther from the base station than those closer to the base station in order to achieve approximately the same average delay throughout the network regardless of location.