Mathematical and simulation analysis of contention resolution mechanism for IEEE 802.11ah networks

Abstract

IEEE 802.11ah Task Group has introduced group-based contention mechanism called Restricted Access Window (RAW) for accessing the shared medium. The RAW mechanism is an initial solution to control the collision that occurs due to the heavy contention in large networks. The Distributed Coordination Function (DCF) is a contention-based medium access method that uses Binary Exponential Backoff (BEB) to resolve contention among the stations inside the RAW group. As mentioned in several literatures, BEB suffers from high probability of collisions. This problem is mitigated through an efficient BO algorithm with appropriate integer sequences for calculating new Contention Window (CW) without any additional control overheads and complex computations. An analytical model is developed for computing saturated throughput, attained by the proposed algorithm. A comprehensive simulation is also carried out in NS3 network simulator with different packet sizes. It is observed from analytical and simulation results that, the proposed backoff algorithm outperforms BEB in terms of saturated throughput, packet delivery ratio, packet loss ratio and delay.