基于信道利用率的无线自组网竞争窗口控制算法

摘要

介质访问控制(MAC)协议的物理载波侦听机制是一种减少冲突的有效方法.同时,载波侦听阈值的大小对网络性能也有很大影响.由于无线自组织网络物理层可具有多种速率,而MAC层中的发送速率与物理层速率的不匹配,会导致网络拥塞和网络性能下降.在分析物理层速率和载波侦听阈值之间关系的基础上,提出一个选择与多速率相匹配的载波侦听阈值算法,最后基于物理层的最理想速率,对MAC层和物理层信道利用率进行比较,再通过竞争窗口来自适应控制MAC层的发送速率来提高网络性能.仿真结果表明,该机制在吞吐量和延迟方面要优于802.11DCF,在吞吐量方面提升了47.66％,在延迟方面降低了33.18％.%Physical carrier sensing is an effective mechanism for medium access control (MAC) protocols to reduce collisions, at the same time, the size of carrier sensing threshold has a great impact on the network performance. Since there is multiple rates in physical layer of wireless ad hoc networks, when the sending rate of MAC level does not match that of physical layer, it will cause network congestion and network performance degradation. In the paper, we investigate the relationship between rates in physical layer and carrier sensing threshold, and present an algorithm for choosing the carrier sensing threshold which is matched with multiple rates. Finally, based on the optimal rates in physical layer, we compare the MAC channel efficiency with that of physical layer, and adaptively control the sending rate in MAC by using the contention window in order to enhance the network performance. Simulation results show that the proposed mechanism outperforms 802. 11 DCF in terms of throughput and delay, 47.66% and 33. 18% , respectively.