Resource Allocation for Multiuser OFDMA-Based Amplify-and-Forward Relay Networks with Selective Relaying

We address the problem of designing efficient resource allocation schemes for an OFDMA based multiuser cooperative communication system that uses amplify and forward relaying. With a two-phase relaying protocol, we assume that both source and the relay have fixed power constraints and that the source employs a selective relaying mechanism. That is, the source adaptively decides on which frequency subcarriers relaying has to performed. We first formulate the problem as a capacity maximizing integer programming optimization problem and then propose a heuristic solution that is composed of several subproblems. The first part is to suboptimally allocate subcarriers to different users based on proportional rate fairness. The next part is a two step iterative approach to find relay decisions and power allocation at the source during the first phase and at the relay during the second phase. The last step is a water-filling algorithm to allocate power at the source during the second phase to all non-relaying subcarriers. Simulation results show that this selective relaying mechanism outperforms the always relay case while also providing an approximate proportional rate fairness.