A Token-Based MAC Solution for WiLD Point-To-Multipoint Links

Abstract

The inefficiency of the fundamental access method of the IEEEE 802.11 standard is a well-known problem in scenarios where multiple long range and faulty links compete for the shared medium. The alternatives found in the literature are mostly focused on point-to-point and rarely on long range links. Currently, there is no solution optimized for maritime scenarios, where the point-to-multipoint links can reach several tens of kilometers, while suffering from degradation due to the harsh environment. This paper presents a novel MAC protocol that uses explicit signalling messages to control access to the medium by a central node. In this solution, this role is played by an Access Point that sends token messages addressed to each associated station, which is granted exclusive access to the medium and assigned a number of credits; after sending its own packets (if any), a station must release control of the token. Simulation results show that this mechanism has superior performance in point-to-multipoint, long range and faulty links, allowing a fairly and more efficient usage of the shared resources among all nodes.