Research On Channel Assignment For Multi-Radio Wireless Mesh Networks

Wireless mesh networks (WMN), which is multi-hop and self-organized, can be applied in last mile broadband wireless access. Compared with widely used Wi-Fi, WMN has the advantages of larger coverage, lower deployement cost and more robustness. It has become a hot research point of broadband wireless communications.Because of the interference between neighboring wireless links, the capacity of WMN dramatically declines with the increasing of the number of nodes and the average hops. Equipping multiple radios on each node and assigning channels to the wireless links properly can effectively reduce network interference and thus increase network capacity.Aiming to increase network capacity, it is studied in this thesis the channel assignment of multi-radio WMN.A network interference metric is defined according to the conflict between neighboring links, the traffic load and data rate of each link. An integer quadratic programming (IQP) model is constructed to obtain optimal channel assignment while minimizing the network interference. This model is based on the global network information and considers different data rates of distinct links. Simulation results reveal that equipping small number of radios per node is sufficient for reducing the network interference. In order to reduce computational complexity, a heuristic channel assignment algorithm is proposed, which has a near optimal performance.Joint routing and channel assignment is investigated without using global network information of WMN. A distributed algorithm using local network information and traffic characteristics of practical WMN is proposed, which includes a routing metric taking account of both the path residual capacity and path consumed air time, an effective method of measuring the link residual capacity, and a novel DOWN-NIC channel assignment method considering both the data rate and interference of each reverse link. Simulation validates its effectiveness of increasing network throughput and reducing average end-to-end delay.In IEEE 802.11b/g standard used by most WMNs, there are 11 channels. Only 3 of them are orthogonal, while the others are partially correlated due to the spectrum overlapping. To explore more channel resource, the interference ranges of the channels with different frequency intervals are analyzed. It is proved that partially overlapping channels can also be used if the channel interval is large enough. A heuristic algorithm is proposed for assigning partially overlapping channels. It can be observed from the simulation results that the network interference can be further reduced if use more channels including partially overlapping channels, as compared with that of only using orthogonal channels.