Throughput Maximization for OFDMA Cooperative Relaying Networks with Fair Subchannel Allocation

In this paper, we consider the dynamic subchannel allocation problem in OFDMA-based selective relaying networks. Our goal is to maximize the total throughput under the constraint of total transmission power, while guaranteeing fairness on subchannel occupation by multiple destination nodes (users). Since the optimal solution to this optimization problem is extremely computationally complex to obtain, we decompose the original optimization problem into two subproblems. Firstly, we assign subchannels to the users with the best equivalent channel gains for them under the assumption of equal power distribution among all subchannels. Secondly, water-filling method is adopted to distribute the power to the determined links. Simulation results show that the performance of the proposed algorithm approaches asymptotically to that of the optimal one, while reducing computational complexity from exponential to linear with the numbers of subchannels, relay nodes and users. It is also shown that subchannel permutation (SP) scheme brings additional throughput gain to DF cooperative transmission.