Adaptive Centralized Random Access for Collision Free Wireless Local Area Networks

Packet collisions caused by the standard Distributed Coordination Function (DCF) protocol in wireless local area networks (WLANs) have been a challenging problem leading to congestion and reduced throughput. To solve this problem,we propose a novel backoff state generation algorithm, called adaptive virtual backoff algorithm (AVBA), operating in an access point. The virtual contention window size in the algorithm is automatically adjusted based on the number of synchronized active nodes in a cell. Backoff counts generated by AVBA operating in the access point are sent by the access point to each active node in the cell to try to synchronise transmissions and minimize packet collisions. Evaluation results show that AVBA improves the throughput performance compared to existing collision resolution techniques, such as deterministic backoff andcentralized random backoff (CRB), when the number of active nodes is large. Moreover, the results show that it maintains a high level of fairness in terms of channel access opportunities between nodes using AVBA and nodes using the DCF protocol when they coexist in a mixed wireless network scenario.