On the secrecy degrees of freedom with full-duplex communication

Full-duplex communication enables simultaneous transmission from both ends of a communication link, thereby promising gains in terms of the throughput and the delay. Such compelling gains are conditioned on a number of design constraints. Generally, it has been shown that the throughput gain and the delay reduction of full-duplex communication are conditioned on a number of assumptions. This has lead researchers to study other possible applications of full-duplex communication which can provide significantly higher gains over half-duplex communication in general. Physical-layer security is an example of such an application. The potential of full-duplex nodes in improving the physical-layer security of a communication link is investigated in this contribution. We specifically derive the information-theoretic secrecy degrees of freedom measure for a pair of nodes communicating in full-duplex mode. The secrecy degrees of freedom with full-duplex is shown to be two as opposed to that of zero in half-duplex mode. In addition, closed-form expressions for the instantaneous and ergodic throughput gain of full-duplex communication over conventional half-duplex are derived.