Study On Multi-Channel MAC Protocols For Wireless Mesh Networks

Wireless Mesh Network (WMN),a static multi-hop wireless network connecting mesh routers and mesh clients with wireless links,is a new type of broadband wireless access systems that is completely different from traditional wireless networks. Nowadays, researches on WMNs have been very popular around the world. Since channel allocation and management is a key factor influencing the performance optimization of networks, MAC protocols for WMNs are gaining significant attention.Based on the analyses of the concepts, architectures of WMN, as well as the researches on MAC protocols at home and aboard, this thesis focuses on multi-channel MAC protocols of WMNs,especially on multiple interfaces condition. Firstly, the demands and problems of multi-channel in WMNs are studied, and then several common multi-channel MAC protocols are analyzed. According to the researches above, an intensively analysis on dual-interface multi-channel WMN is made, and the network employs a hybrid multi-channel protocol HMCP. In WMN based on this protocol, each node in the network is equipped with two wireless radio interfaces and uses multiple channels for transmission. To some extent, this protocol implements a channel allocation strategy which increases the throughput and improves the system performance.This strategy provides support for frequent channel switching on an interface which is required by the hybrid multi-channel protocol, but also brings certain channel switching delay overheads, which is the key factor that effects the performance of WMN. Then, we discuss how to reduce the delay of channel switching and the effects on all aspects of system performance.In order to improve thoughput and network performance, a new routing police based on HMCP is put forward.Through the simulation, we look at the throughput improvement achieved for a single flow and concurrent multiple flows in the multi-channel network as opposed to using a single channel in the network. Experiments show that HMCP network gets more thoughput and allows the UDP thoughput achievable over a single hop to be sustained over multiple hops for a flow. What's more, it's also indicates that HMCP network achieves the throughput for flows more than twice than that achieved when using single channel in the network. It also confirms that it will arise some problems when transmitting data concurrently in the multi-channel networks of which the nodes are too closed to each other, and the channel switching delay has great influence on the performance of network. These problems can be addressed by making certain changes in the Multi-Channel Routing metric. Then, the thesis evaluates the throughput performance improvements observed when using the new routing metric as compared to using the old routing metric.Finally, some suggestions for developing new multi-channel protocols and mesh networks in future are made.