A Fast Forward Full-Duplex Cooperative Relay Scheme for Securing Wireless Communications

This letter makes a first attempt to design a cooperative relay scheme to secure wireless communications by adopting a fast-forward full-duplex (F3D) node. Different from the conventional full-duplex relay, the F3D node could process and forward the received signal immediately. With such forwarding, the forwarded signal of F3D could enhance the signal to interference plus noise ratio of the receiver, whereas weaken that of the eavesdropper and thus build up a secure channel. Beyond the proposed scheme, we move forward to optimize the signal processing design of the F3D node with the target of maximizing the secrecy capacity. The formulated optimization problem is nonconvex and challenging to deal with. We then design an iterative algorithm based on generalized fractional programming to solve it. One key step in the iterative algorithm involves another nonconvex optimization and we decompose it into a two-level optimization. Simulation results validate the effectiveness of our designed secure cooperative relay scheme and show that adopting F3D node for physical-layer security has good performance in terms of achievable secrecy capacity compared with the scheme without F3D node.