基于IEEE802．11b的无线Mesh网中信道分配策略的分析及仿真

Simulation and Analysis of Channel Assignment Strategy in IEEE802.11b-Based Mesh Networks

研究无线Mesh网在繁忙区域增加接入点(AP)时,各种信道分配策略对网络性能的影响.首先研究了在多个AP和多个用户的热点环境中的容量平衡机制,然后分析了在物理层使用IEEE 802.11b标准提供的多重叠信道时对每个AP的影响,最后通过实测试验和NS2仿真,研究了信道条件、节点密度、信道接纳策略以及MAC协议对吞吐率和公平性的影响.结果证明,在网络中同一区域存在多个AP时,由于有限的频谱和无线介质特性,增加新的AP并不与系统容量成正比,反而会因为竞争和干扰降低这个区域的吞吐量.3种分配策略都存在一定的局限性,因此需要进一步考虑其它有效措施来提高系统容量.

The purpose of this paper is to study the affecting factors of channel assignment strategy on the performance of wireless Mesh network （WMN） when the number of APs is increased in a hot-spot （a crowded area with heavy traffic）. We first study mechanisms to balance the capacity of hot-spots in a scenario with multiple APs and many wireless users. Then we analyze the impact of separating each AP at the physical layer using multiple overlapping channels as provided by the IEEE 802. 11b standard. Finally we perform an extensive set of measurements and ns-2 simulations to study the impact of factors such as channel conditions, node density, channel allocation policies, and MAC protocol on throughput and fairness. The result shows that, due to the shared nature of the wireless medium and limited spectrum, the addition of new AP in the area with multiple APs does not increase the total system capacity proportionally, but can significantly degrade the total throughput of the region as a result of interference and contention. Three channel assignment strategies considered all have their own limitations. It is necessary to use other ways to improve the network performance.