Wireless local area networks (WLANs) based on the family of 802.11 technologies are becoming ubiquitous. These technologies support multiple data transmission rates. Transmitting at a lower data rate (by using a more resilient modulation scheme) increases the frame transmission time but reduces the bit error rate. In non-cooperative environments such as public hot-spots or WLANs operated by different enterprises that are physically close to each other, individual nodes attempt to maximize their achieved throughput by adjusting the data rate or frame size used, irrespective of the impact of this on overall system performance. In this paper, we show both analytically using a game theoretic model and through simulation that the existing 802.11 distributed MAC protocol, DCF (for Distributed Coordination Function), as well as its enhanced version, which is being standardized as part of 802.11e, can lead non-cooperative nodes to undesirable Nash equilibriums in which the wireless channel is inefficiently used. We show that by establishing independence between the allocation of the shared channel resource and the transmission strategies used by individual nodes, an ideal MAC protocol can lead rational nodes to arrive at equilibriums in which all competing nodes achieve higher throughputs than with DCF.

翻译：基于802.11系列技术的无线局域网（WLAN）正变得无处不在。这些技术支持多种数据传输速率。以较低的数据速率传输（通过使用更具抗干扰能力的调制方案）会增加帧传输时间，但会降低误码率。在非合作环境中，例如公共热点或由物理位置相近的不同企业运营的WLAN中，各个节点试图通过调整所使用的数据速率或帧大小来最大化其获得的吞吐量，而不管这对整体系统性能的影响。在本文中，我们通过博弈论模型的分析以及仿真表明，现有的802.11分布式MAC协议——DCF（分布式协调功能），以及其增强版本（正作为802.11e的一部分进行标准化），可能导致非合作节点陷入不良的纳什均衡，在这种均衡下无线信道被低效利用。我们证明，通过建立共享信道资源分配与各节点所用传输策略之间的独立性，一个理想的MAC协议可以引导理性节点达到均衡，在此均衡下所有竞争节点都能获得比使用DCF时更高的吞吐量。