Relay Selection for Improving Physical Layer Security in D2D Underlay Communications

This paper investigates the physical layer security of inband underlay Device-to-Device (D2D) communication, where direct link between D2D users is not available. In this respect, optimal relay and suboptimal selections are utilized to secure transmission. The eavesdropper uses either maximal-ratio combining or selection increase wiretapped signals. secrecy performance analysis performed regarding outage probability (SOP) non-zero capacity, closed-form expressions provided for both approaches verified using Monte-Carlo simulation. From numerical results, it shown that increasing number relays enhances communications. Moreover, exact asymptotic SOP provided. It turns out diversity order same.