Physical Layer Security Schemes for Full-Duplex Cooperative Systems: State of the Art and Beyond

As an alternative to complex cryptographic techniques, PLS is emerging as a promising paradigm to protect wireless communication systems from eavesdropping attacks by exploiting the physical characteristics of the wireless channels. Among various PLS approaches, the one based on cooperative communication is favorable and has received a lot of interest from the research community. Although PLS schemes with half-duplex relays have been extensively researched, the issue of PLS in cooperative systems with full-duplex (FD) relays is far from being comprehensively understood. In this article, we first present the state of the art on PLS approaches proposed for FD cooperative systems. We then provide a case study in which a source-based jamming scheme is proposed to enhance the secrecy performance of a cooperative system with an untrusted FD relay. Finally, we outline several interesting yet challenging future research problems in this topic.