Fair resource allocation and DF relay selection for multiuser OFDMA-based cooperative networks

We investigate the joint problem of power and subcarrier allocation with relay selection for a multi-user multi-relay cellular system with selective relaying. We first formulate the optimal problem using Boolean-convex optimization with the objective of improving the average network capacity while providing proportional rate fairness to all users. We show that except for very small network instances the model is computationally very complex to solve. Then, we present a sub-optimal model by decomposing the joint problem into two sub-problems. This model proves to be a simple one, however, the sub-optimal design of the first sub-problem restricts the model from achieving near optimal solutions. Therefore, to achieve near optimal solutions, we propose an iterative two step method where near-optimal solutions can be achieved by iterating between the two steps. Numerical results show that for smaller networks this two step iterative method obtains optimal solutions in much less time. We also show that a selective relaying technique always achieves better performance over the always relaying technique.