Power Allocation for OFDM Based Links in Hybrid Forward Relay

In this paper, we consider a two-hop orthogonal frequency division multiplexing (OFDM) relay link, and investigate the system capacity in hybrid forward (HF) relay through the power allocation (PA). The expression of the system capacity in HF relay is provided. Two situations about the power constraint are concerned, and under each situation, the selection criterion among different forwarding schemes in HF relay is proposed by means of capacity comparison on the subcarrier pair. From the selection criterions, the source or relay can adaptively choose the best scheme for every subcarrier pair according to the channel condition. Then the optimal solutions of the relay PA and the joint PA are derived to maximize the capacity. In the simulation, the advantage of the HF relay is shown in terms of capacity improvement compared with the conventional forward relay.