Efficient Resource Allocation for OFDMA-Based Two-Hop Relay Systems

We propose an efficient resource allocation scheme for the downlink of orthogonal frequency-division multiple-access (OFDMA)-based two-hop relay systems. The proposed scheme reuses the subchannels within a single cell in the frequency-selective fading environment by allocating a subchannel to multiple links simultaneously. We first formulate a preliminary subchannel allocation problem in consideration of the quality-of-service (QoS) requirements for both real-time traffic and nonreal-time traffic. We also design an efficient postprocessing algorithm that modifies the solution obtained by solving the preliminary problem so that it can be used in practical OFDMA systems. Numerical results show that the proposed scheme can significantly improve system performance.