Topology optimization for wireless mesh with directional antennas

A wireless mesh employing directional antenna, termed DMesh in this paper, can greatly extend coverage and improve spatial reuse of wireless channels. As beaming direction of the antennas changes network topology which in turns affects routing and channel decisions, we address in this work how to jointly optimize topology (in terms of beaming directions of antennas), routing and channel assignment so as to maximize network throughput. Specifically, we use a model based on SINR which captures much more realistically network interference than the traditional conflict graph approach. Using the model, we then formulate the NP-hard optimization problem for a general DMesh with multiple gateways, possibly heterogeneous number of antennas in routers, and routers generating traffic to any of the gateways or routers. As the problem is NP-hard, we propose a simple and implementable joint optimization heuristic called TORCA (topology control, routing and channel assignment). TORCA is based on iterative LP rounding guaranteed to converge. Extensive simulation based on NS3 shows that TORCA is closely optimal and highly efficient, performing significantly better than recent approaches by wide margins in terms of loss rate, delay, fairness and throughput.