Joint optimal AF relay assignment and power allocation in wireless cooperative networks

We investigate the joint problem of optimal relay selection and power allocation in wireless cellular networks considering both unicast and multicast traffic. We first present mixed Boolean-convex optimization models for both unicast and multicast traffic scenarios to maximize the overall network capacity and solve these combinatorial problems optimally using the branch and bound technique. We then show that obtaining the optimal solution is computationally infeasible for large network sizes. For unicast, similar to [1], we present an efficient water-filling based technique to obtain near optimal solutions. We show that, unlike unicast traffic, water-filling does not yield near optimal solutions in multicast scenarios. We thus adopt an algorithm based on sequential fixing for the multicast case which substantially reduces the computation time and achieves near optimal solutions. Furthermore, in the above scenarios, we assume that the power levels are drawn from a continuous range. To make the proposed methods more practical, we also consider scenarios when the number of power levels is finite (i.e., discrete). We present optimal and sub-optimal methods for solving this optimization problem and compare their performance with previous methods.