Achievable rate region for two-way OFDM relay networks

Higher data rates will be needed in the next generation of mobile communication systems. This paper presents a multi-subcarrier decode-and-forward relay strategy that reduces data loss in per-subcarrier relay strategies for two-way orthogonal frequency division multiplexing (OFDM) relay networks. This paper also presents an optimal (convex) power allocation problem that characterizes the achievable rate region for the relay strategy that maximizes the weighted sum rate, where the weight factors depend on the queue lengths of the user data buffers. An efficient duality-based algorithm is developed to solve this power allocation problem. The computational complexity of this algorithm is only linear with respect to the number of subcarriers, which is much lower than that of conventional interior-point methods for solving convex optimization problems. Numerical results show that the strategy substantially enlarges the achievable rate region over existing per-subcarrier relay strategies.