中文摘要：

针对此类网络的饱和吞吐量模型，分析了速率调整无法降低帧冲突的原因以及发送节点的尝试发送帧概率对网络性能的影响．基于发送节点的尝试发送帧概率和竞争窗口大小之间的关系，提出了一个802．11多速率无线局域网中控制竞争窗口的方法，该方法通过估计局域网中的平均连续空闲时隙数来控制竞争窗口，因此能够主动减少由于节点数量大造成的帧冲突，从而提高网络性能．模拟实验表明，在802．11多速率无线局域网中，竞争窗口控制算法的引入可以在已有的速率调整算法的基础上使网络性能大大提高，获得更好的吞吐量和公平性．

英文摘要：

Under a saturated throughput model in 802.11 multi rate WLANs, the ineffectiveness of rate adaptation on collisions and the impact of transmission probability on network performance were studied. Based on the relationship between the transmission probability and the value of contention window, an algorithm, which estimates the average number of consecutive idle slots to control contention window and decreases collisions to improve the performance of 802.11 multi-rate WLANs was presented. Simulation results show that combining rate adaptation with contention window control can achieve much better network performances, including throughput and fairness, than only using rate adaptation in 802. 11 multirate WLANs.