Analysis of New Distributed-Media Access-Control Schemes for IEEE 802.11 Wireless Local-Area Networks

Many modifications are proposed in the literature to improve the throughput performance of the distributed coordination function (DCF) under congested environments. These improvements are achieved by modifying the contention-window reset mechanism used in the DCF protocol. However, the main drawback with these modifications is the high backoff process overhead. We have recently proposed a new modification to DCF (N-DCF) to improve the throughput performance by reducing the average backoff overhead. In this paper, we propose a throughput model for N-DCF, which is applicable for arbitrary load conditions. We verify the throughput model by NS-2 simulations. Then, we compare the performance of N-DCF with other recently proposed DCF enhancements in the literature. Comparisons reveal that only N-DCF provides throughput improvement in the request-to-send/clear-to-send access mechanism. Finally, we propose two more schemes to further improve the performance of our original N-DCF scheme.