Full-Duplex Decode-and-Forward Relay-Assisted Interference Management: A Diversity Gain Region Perspective

A two-user Z-channel with a full-duplex (FD) decode-and-forward (DF) relay, where one user is interference-limited while the other user is interference-free, is considered in this paper. The FD-DF relay can decode either a part of the interference or the entire interference. The former is called partial DF (PDF) protocol, and the latter is called complete DF (CDF) protocol. In the case of PDF protocol, the interference-limited user does partial interference cancellation. A closed-form expression for achievable diversity gain region (DGR) with the PDF protocol is presented. Furthermore, achievable DGR of the PDF protocol is optimized under the constraint that the interference-free receiver achieves optimal diversity gain. At low interference levels, the PDF protocol provides better DGR compared to both CDF protocol and direct transmission scheme. As the interference level increases, either the CDF protocol or the direct transmission scheme is shown to achieve better DGR compared to PDF protocol. The multiplexing gain regions where the PDF, CDF, and direct transmission schemes perform well are identified.