Analysis of Mobile Radio Slotted ALOHA Networks

Abstract

Given a mobile terminal transmitting a message to some receiver, the level at the receiver will be affected by path loss and by fading phenomena. Transmissions from different terminals will suffer different attenuations on their respective ways to the receiver and will therefore yield different levels at the receiver. Thanks to the capture effect, the receiver will now be able to read the message with the strongest signal, provided that it is sufficiently stronger than its contenders. In a mobile radio ALOHA network this means that a packet collision need not necessarily destroy all packets involved. A Markov model is developed for slotted ALOHA networks with capture and it is shown that the throughput in such a network can be markedly greater than the famous <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/e</tex> . Perhaps even more important is the result that such networks are very stable under overload.