Topology control with a limited number of relays

Network longevity and connectivity are key design goals in any wireless sensor network deployment. In this context, we consider the placement of relay nodes and individual transmission power assignments. Specifically, given a planar deployment of sensors and a base station, we seek the placement of a limited number of relays and optimal sensor power assignments such that the network is connected. We present a polynomial-time bicriteria approximation algorithm for this problem. We also provide an optimal O(n² log n)-time algorithm for a restricted version where nodes lie on a simplified urban grid (that we call a comb-grid). We also study a related variant that assumes fixed transmission power values, with the goal of minimizing the number of relays. We provide extensive simulation results for the comb-grid case.