Optimal power allocation for a full-duplex multicarrier decode-forward relay system with or without direct link

This paper addresses power allocation problems for a dual-hop full-duplex multicarrier decode-forward relay system with or without a direct link from the source to the destination. The full-duplex relay has a residual self-interference proportional to its transmitted power. We consider two schemes of decode forward at the relay: carrier-wise decode-forward (CDF) and group-wise decode-forward (GDF). For the CDF scheme, we consider problems of optimal power allocation subject to system-wise total power constraint, node-wise individual power constraint and system-wise rate constraint, respectively. All these problems are shown to be equivalent to convex problems, and fast algorithms for finding the exact solutions are developed. For the GDF scheme, we focus on the case of node-wise individual power constraint. This problem is non-convex for which we develop fast algorithms for finding locally optimal solutions. Using the algorithms developed in this paper, we are able to show that the system capacity with optimal power allocation based on either CDF or GDF is higher than that of the half-duplex relay (HDR) system at power levels where HDR outperforms the direct transmission via the direct link. Furthermore, the system capacity based on GDF is consistently higher than that of HDR for all power levels while both have the same degree of freedom. This paper also shows new insights of algorithmic development, which should be useful for other related problems. (C) 2017 Elsevier B.V. All rights reserved.