Multichannel Wireless Networks: Capacity and Protocols

Recent years have seen significant interest in using the multihop wireless networking paradigm for building mesh networks, ad hoc networks, and sensor networks. A key challenge in multihop wireless networks is to provision for sufficient network capacity to meet user requirements. Several approaches have been proposed to improve the network capacity in multihop networks, ranging from approaches that improve the efficiency of existing protocols, to approaches that use additional resources. In this dissertation, we propose to use additional frequency spectrum, as well as improve the efficiency of using existing frequency spectrum, for improving network capacity. Widely used wireless technologies, such as IEEE 802.11, provision for multiple frequency-separated channels in the available frequency spectrum. Commercially available wireless network interfaces can typically operate over only one channel at a time. Due to cost and complexity constraints, the total number of interfaces at each node is expected to be fewer than the total number of channels available in the network. Under this scenario with fewer interfaces per node than channels, several challenges have to be addressed before all the channels can be utilized. In this dissertation, we have established the asymptotic capacity of multichannel wireless networks with varying number of channels and interfaces. Capacity analysis has shown that it is feasible to effectively use a large number of channels even with only a few interfaces per node. Based on insights from the capacity analysis, we have developed a new interface management protocol and a new routing protocol to exploit multiple channels. Detailed simulation-based evaluations of the protocols have shown that multiple channels can be used to significantly enhance network capacity, even if only a few interfaces per node are available. We have implemented the protocols in a testbed to demonstrate the feasibility of using the protocols in practice. As part of the implementation, we have developed generic architectural support for using multiple channels, which may be of use in implementing other multichannel protocols as well