Load Balancing Of Multi-gateway Wireless Mesh Network

With the development of the Internet and popularity of Web applications, we have been used to getting information from the Internet. And we hope to access the Internet anywhere and anytime. Cellular network is a common way to achieve this, which includes 2-generation GPRS network and 3-genaration (WCDMA, CDMA200, TD-SCDMA) networks.As a kind of infrastructure network, the cellular network works stably, but costs highly. First, the wired Internet connection and the spectrum licenses are expensive. Second, the station itself is expensive and its maintenance cost is high. All of these lead to a high cost for users to access the Internet by cellular network. Wireless Mesh Network (WMN) is brought out for the reason of low cost, high signal coverage and flexible application. In WMN, stations communicate to each other by multi-hop wireless links so the cost is lower and the coverage is bigger. But the distributed and multi-hop structure makes the original protocols perform poor in WMN. And the asymmetric structure leads to an unbalance load in the network. This thesis analyzes the problem of load balancing of WMN and proposes two protocols to solve the load balancing problem of WMN.In Chapter 2, the thesis introduces the WMN on the aspect of structure and protocols firstly. Then the thesis lists the typical application scene of WMN, such as in battle fields or emergency activities. The integration of protocols on each layer, the cross-layer method and the security problem etc. are discussed at the end of this chapter.According to the load balancing problem on gateways, Chapter 3 analyzes the causes for the load unbalance firstly. In order to solve the problem on 802.11s based WMN, this chapter introduces the gateway selection procedure and the related messages. Consequently a strategy on gateway load balancing is brought out. In order to evaluate the performance of giving method, a test bed on Net Simulator 2 is developed and shows that the proposed strategy can improve the load-balance on WMN gateways very well.A cross-layer designed routing protocol is brought out to solve load balancing problem at the center of WMN. Chapter 4 analyzes the CSMA/CA working flow and gives the relation between RTS drop rate and the congestion level by a lot of experiments. Then the thesis gives out a multi-path routing protocol based on HWMP (Hybrid Wireless Mesh Protocol) and takes the RTS drop rate as a part of routing metrics. Based on NS2 test bed, experiments resaults show that the protocol has a good performance on network throughput, peer-2-peer delay and user fairness.Finally, Chapter 5 gives a summary of the thesis work and looks into the future research of WMN.