Abstract
Full-duplex (FD) communications provide a more efficient and secure architecture for secure communications. It enables both source and destination nodes to generate artificial noise (AN) to interfere with the eavesdropper while still can decode the original signal with a negligible loss. Despite the direct FD transmission, an FD-enabled relay architecture further improves the secrecy rate of secure communications by adding a relay node to the transmission. Nevertheless, it is challenging to implement a stable relay system due to lacking incentives for the potential relay nodes to deliver the messages of others, especially when they have their own messages to transmit. In light of this concern, we propose a double relay model, that is, both source nodes of transmissions pairs relay the messages of each other simultaneously in FD mode so both can benefit from the relay system. This naturally formulates a roommate matching problem, which is a traditional matching problem in game theory. Nevertheless, the proposed problem is different from the existing single-party matching problem as the relay is optional in our system. Thus, we extend the roommate matching problem to support that players can strategically choose to be single. We then propose an improved roommate matching algorithm, which aims to maximize the system secrecy rate and guarantee the incentive of participated pairs. The simulation results confirmed that the proposed algorithm could achieve near-optimal performance.