Joint power allocation and subcarrier pairing for dual-hop OFDM links with full-duplex relaying

Resource allocation plays an important role in orthogonal frequency division multiplexing (OFDM) based relaying systems. In this paper, we jointly consider power allocation (PA) and subcarrier pairing (SP) in a relaying system in which a source node sends OFDM signals to a destination node with the help of a full-duplex (FD) relay node. Under individual power constraints at both the source node and the relay node, we seek to maximize the end-to-end data rate of the relay link by performing PA across subcarriers in the two hops. Furthermore, SP is employed to re-associate subcarriers between the incoming link and the outgoing link at the relay to further improve system performance. Specifically, the coupling of different subproblems makes the problem rather complicated. Thus, we propose a novel iterative method together with the dual method to solve this joint PA and SP problem, which is verified by simulations to be able to converge in a small number of iterations. Numerical results show that the proposed algorithm can significantly enhance the system performance when compared to conventional methods; particularly, PA can provide significant benefit in the case of high self-interference. In addition, when the relay self-interference is high, with the proposed joint PA and SP method, FD operation at the relay can reduce to half-duplex (HD) mode from the frequency domain perspective, where the relay only receives over a portion of subcarriers and transmits over the rest subcarriers to avoid excessive self-interference.