Model-Based Radio and Channel Assignment in IEEE 802.11 Wireless Mesh Networks

Local area wireless networks based on IEEE 802.11 have a cellular topology: Stations associate to one of several access points, which are connected using a wired backbone. As connectivity is only possible close to the access points, a dense infrastructure is needed, resulting in high costs. A Wireless Mesh Network (WMN) replaces the wired backbone by radio: Only few access points are installed; mesh points extend their coverage by forwarding data over wireless hops. Hence, deployment costs are reduced. Since the wireless medium has to be shared by the nodes, multi-hop traffic requires a high capacity. Hence, mechanisms which increase the system capacity in wireless mesh networks are needed. With more than 10 orthogonal channels, IEEE 802.11a provides an excellent foundation for a multi-channel network; furthermore, standardized hardware allows to equip nodes in the WMN with more than one radio. Thus, the problem arises how to plan the channel and radio assignment in a IEEE 802.11-based Multi-Channel Multi-Radio (MRMC) WMN. In this paper, we first establish and evaluate a model to compute the saturation throughput in a given WMN configuration, taking into account the characteristics of the service area and the MAC and PHY capabilities of IEEE 802.11. With the help of the model, it becomes possible to identify the network bottleneck; This allows the application of a local search optimization algorithm which maximizes the saturation throughput under the constrains of limited channels and radios. The evaluation shows that the developed algorithm together with the load model does not only increase the saturation throughput, but also the system spectral efficiency, which indicates a more effective usage of the radio resources.