Optimal resource allocation for network coding in multiple two-way relay OFDM systems

This paper investigates optimal resource allocation in orthogonal frequency division multiplexing (OFDM) based multiple two-way relay systems operating with analog network coding (ANC) protocol. We formulate a joint optimization problem considering power allocation, relay selection and subcarrier paring to maximize the sum capacity under individual power constraints on each node. By applying dual method, an unified optimization framework is provided and the problem is solved efficiently. Based on this framework, we further propose three suboptimal algorithms. The complexity of optimal algorithm (ORA) and three suboptimal algorithms are evaluated, and the analysis results show that the complexity of ORA is only a polynomial function of the number of subcarriers and relay nodes. Simulation results demonstrate that the proposed ORA scheme yields substantial performance improvement over baseline scheme, and suboptimal algorithms can achieve a trade off between performance and complexity.