Service Differentiations with Dynamic Jamming-length Control in Wireless Ad Hoc Networks

摘要

EDCA, developed by IEEE 802.11 working group E, provides service differentiations for the growing demand of multimedia traffic. Although it has emerged as an upcoming standard in wireless local area networks, the problems of continuous contention failures and unfair bandwidth sharing among high- and low-priority traffic remain unsolved. To overcome these QoS limitations, this paper presents service differentiation with jamming-based MAC (JMAC) for multimedia traffic in wireless ad hoc networks. The main idea behind the JMAC scheme is that mobile nodes can be differentiated by transmitting different lengths of jamming noise; the one with the longest jamming length can win the contention, immediately broadcast its current priority level (local) to update the global priorities of all the neighboring nodes, and start its frame transmission. The length of jamming noise issued by a mobile node can be dynamically adjusted based on its current priority, global priority, and contention retries experienced by a frame. Therefore, the possible starvation of low-priority traffic and the ineffective contention of high-priority traffic can be avoided simultaneously. For the purpose of performance evaluation, the proposed JMAC scheme is simulated on NS-2. The performance metrics of our interest include the contention-success probability, the packet dropping ratio, the medium access delay, and the system throughput. The simulation results show the effectiveness and the superiority of our proposed scheme over other previous works.