Routing in ad-hoc networks with MIMO links: Optimization considerations and protocols

Smart antennas include a broad variety of antenna technologies ranging from the simple switched beams to the sophisticated digital adaptive arrays. While beam-forming antennas are good candidates for operation in strong line of sight (LOS) environments, it is the multiple input multiple output (MIMO) technology that is best suited for multipath environments. In fact, the MIMO links exploit the multipath induced rich scattering to provide high spectral efficiencies. The focus of this work is to identify the various characteristics and tradeoffs of MIMO links that can be leveraged by routing layer protocols in rich multipath environments to improve their performance. To this end, we study the relative benefits of the different strategies of operation in MIMO links both analytically and through simulations. Using the insights gained from the study, we propose a routing protocol called MIR for ad-hoc networks with MIMO links, that optimally leverages the various characteristics of MIMO links in its mechanisms to improve the network performance. We show the effectiveness of the components of the proposed protocol by evaluating its performance through ns2 simulations for a variety of network conditions. Results indicate that MIR is able to provide significant performance gains of about 100% over baseline approaches.