Capacity analysis of 802.11 multi-channel multi-radio wireless mesh networks

IEEE 802.11 based wireless mesh networks have recently attracted much attention as they provide a quick and inexpensive way to extend access to the existing wired networks. A significant problem of such networks is their limited capacity due to signal interference. A frequently proposed approach to increasing mesh network capacity is to equip each mesh node with multiple radios, which can work on multiple non-interfering channels simultaneously. In this paper, we characterize the relationship between the mesh network capacity and the number of non-interfering channels as well as the number of radios per node, assuming that each radio works on a statically assigned channel. Our main result is that, given k non-interfering channels and m radios on each node, the network capacity improvement is bound by O(min(k, m(2)/t)), where t is the average node degree per neighbor (i.e., the average number of common channels shared by a pair of neighboring nodes). The parameter t and the number of neighbors around each node determine the mesh network's average node degree, which affects the network connectivity. To validate our analysis, we use simulation results of two channel assignment algorithms and find that both can achieve a constant factor of the theoretical upper bound. Our work offers practical insights for designing and evaluating channel assignment algorithms and for deploying 802.11 wireless mesh networks.