Heterogeneous Multi-interface Multi-channel Wireless Mesh Networks

Wireless Mesh networks with the characteristics of high bandwidth, large coverage and low deployment cost, was one of the most popular solutions for the "last mile" internet access. The usage of a wide range of wireless radios and multi-channel technology would further enhance the network performance. The channel assignment algorithm and routing protocol were studied in this paper as they had a direct impact on network performance and resource utilization. The main work done at this dissertation was as follows.Due to the differences between node's interface types and number in heterogeneous multi-radio multi-channel WMN, its channel assignment would cause the neighbour nodes' throughput down, a neighbor information and channel usage statistics based channel assignment algorithm was proposed. All nodes in the network used a common channel as the control channel to share their radio-channel information and a channel gain factor was designed based on the information to quantify the network's throughput gain when one channel was assigned. At the same time the usage frequency statistics of the surrounding active channels were counted, the lower the channel's usage statistic the smaller the potential conflict. Combined the channel gain factor and channel usage frequency statistics, a channel assignment metric called CGSBM was designed, which made node not only consider it self's throughput requirement but also took its neighbor nodes' data transmission into account when it was assigning the channels.In the network layer, network load balancing issues became the key issues of affecting the routing protocol's performance because of the heterogeneity in nodes' radio, thus a radio ability and link-layer information based cognitive routing protocol was proposed which aimed to improve the network throughput and balance network load. The link-layer related parameters such as bandwidth, bit error rate, channel usage statistics and MAC layer's queue length information were send to the network layer with the help of the modified ICMP message, then a link quality measurement, node's channel switching cost measurement and path load measurement were designed based on these parameters. All the three measurement were integrated into a new comprehensive routing metric called RACIM, which was used in the modified DSR routing protocol.Finally, a performance evaluation of the proposed CGSBM algorithm and RACIM protocol was carried out with the help of network simulation tool NS2 under a variety of network scenes. The simulation results showed that there was a performance improvement on network throughput and network resource utilization compared with other algorithm.