On effects of feedback delay in secure buffer-aided relay networks

Cooperative communication is one of the fundamental technologies for the future wireless networks including 5G to improve communication reliability and enhance spectrum efficiency. In this paper, we consider a buffer-aided relay that performs opportunistic selection of the legitimate users in presence of an eavesdropper under physical layer security constraints. The channel state information of users are subjected to delays in the feedback channel. Closed form expression for outage probability is derived based on link selection scheme. Numerical results present the minimized secrecy outage probability by optimizing selection parameters. It is found that although feedback delay degrades the performance, the increase in number of legitimate users helps to improve the performance by exploiting multiuser diversity.