Research On Multi-Gateway Routing And Handoff Mechanism In Wireless Mesh Network

With the development of wireless communication techniques, wireless networks changes people's daily life dramatically by providing mobile Internet access. Now widely used Wireless Local Area Network (WLAN) is a single-hop wireless access network, access point(AP) is needed by the wireless terminals to access wired networks. Transmission distance of single-hop wireless network limits the coverage of the WLAN. Meanwhile, AP needs direct connection to the wired network, resulting that WLAN has serious dependence on wired network, deployment cost is still high. To extend the coverage of wireless access networks and reduce the deployment cost, Wireless Mesh Network is introduced.Wireless Mesh Network provides a brand new way to access the Wide Band network. As a revolution of traditional network topology, Wireless Mesh Network not only reduces the deployment cost, but also extremely extends the wireless network coverage. It is independent of cables, and has high performance at the same time. At present, the research on Wireless Mesh Network is still at the very beginning. The original network protocols and techniques are unsuitable in this new environment. So, the new protocols and techniques, which agree with Wireless Mesh Network to make use of the network capacity, are eagerly demanded.In this master's dissertation, we present a Multi-Gateway and Multi-Path Routing protocol which is mainly implemented in Wireless Mesh Network. Because there is always not only one gateway in Wireless Mesh Network, other gateways can also be used to communicate with Internet. The wireless terminal is mapped to several gateways, and data stream can select the rational gateway and path to route. Meanwhile, the multi-path routing is based on data packet. This Multi-Gateway and Multi-Path routing protocol dramatically increases the degree of parallelism and improves the efficiency of the network.After the investigation of the traditional terminal handoff strategy, we divide the situation of terminal handoff to internal handoff and external handoff, and use two different handoff strategies to handle them. Internal handoff has a higher priority and lower handoff delay and overhead than external handoff. An external handoff will be triggered when the internal handoff cannot be occurred. Although, external handoff has higher handoff delay and overhead, it can make sure the data stream not being interrupted. The combination of two handoff strategies not only brings down the handoff delay, but also reduces the average network overhead. There is no centralized management mechanism in Wireless Mesh Network; the change of network topology is also out of control. The traditional method to dealing with the change of network topolohy is link-aware and routing update. The response is too slow to maintain the data stream. To strengthen the network robustness and guarantee the transferring data streams being not interrupted, the mesh gateways and mesh routers should be adjusted to the new topology in advance. After the imployment of network active mediation, data stream will not be interrupted in most cases.Numbers of expirements have been done to verify the protocols which have been concerned. The results show that there is a visible improvement after using the protocols which are designed for Wireless Mesh Network, and Wireless Mesh Network is dominant in performance compared to WLAN.This thesis shows the high performance routing protocol and handoff strategy aiming at Wireless Mesh Network. The correlative network simulation has been experimented. This thesis also makes reasonable recommendations on how to routing protocol and handoff strategy of Wireless Mesh Network.