Stability of S‐Aloha with variable propagation delay

Abstract

State-of-the-art variants of slotted Aloha (S-Aloha) for underwater acoustic networks do not consider the joint effect of retransmission and distance-dependent propagation delay variability, which is one of the most important parameters that affect the performance of any medium access control protocol. In this study, the authors analyse the stability of S-Aloha in a network environment, such as underwater, where propagation delay and its variance are not negligible. A finite number of unbuffered transmitters are considered. Through mathematical analysis, supported by discrete event simulations, they compare the utilisation and stability with S-Aloha in radio frequency environments where propagation delay, as well as delay variance, are negligible. The comparison results indicate that the stability region is appreciably shifted and also there is a significant decrease of utilisation in the presence of retransmission and distance-dependent propagation delay variability.