Analysis of New Distributed Media Access Control Protocols Proposed for IEEE 802.11 Wireless Local Area Networks

Since distributed coordination function (DCF) is the basis protocol for IEEE 802.11 standard wireless local area networks, many modifications have been proposed in the literature to improve its throughput performance particularly under congested environments. These improvements are achieved by modifying the contention window reset mechanism in which a DCF station immediately reduces the window size to the minimum value (ω0) after a successful transmission, irrespective of the congestion level observed on the channel. Recently, we have proposed a new media access control protocol N-DCF to improve the throughput performance of DCF by reducing the average backoff overhead that is required for the packet transmission. In this paper we present the analysis of N-DCF protocol by proposing a throughput model applicable for any arbitrary load conditions. The throughput model is verified by simulating N-DCF using NS-2 network simulator. We then compare the performance of N-DCF with the other recently proposed DCF enhancements in the literature. Comparisons have revealed that only N-DCF provides improvement in throughput performance under RTS/CTS access mechanism. Based on the reasoning, we propose two more media access control schemes to further improve the performance of DCF protocol in both basic and RTS/CTS access mechanisms. Finally, we analyze the performance of the proposed modifications to N-DCF protocol.