Joint Relay Selection and Destination Assisted Cooperative Jamming with Power Allocation for Secure DF Relay Network

To enhance the physical-layer security of a decode-and-forward (DF) cooperative relay network in the presence of a potential eavesdropper, a joint relay selection and destination assisted cooperative jamming (CJ) scheme is proposed. In phase I, the source transmits its confidential signal, and concurrently, it cooperates with the friendly jammers and the destination to send jamming signals to confuse the eavesdropper without affecting the forwarding relay which is preselected. In phase II, the forwarding relay retransmits the decoded signal, and simultaneously, the particular relay cooperates with the friendly jammers to send jamming signal to confuse the eavesdropper without affecting the destination. The achievable secrecy rate maximization (SRM) problem is investigated by optimally allocating the power between the data signal and jamming signals. Although SRM problem is non-convex, the power allocation problem can be solved by a bisection method together with a one-dimensional search. Optimal relay selection and suboptimal relay selection schemes are also proposed to further improve the secrecy rate. Simulation results are presented to show that the joint scheme can attain higher achievable secrecy rates than some existing works.