Link Selection for Secure Two-Hop Transmissions in Buffer-Aided Relay Wireless Networks

This paper investigates the link selection problem for a two-hop relay wireless network consisting of one source-destination pair, one decode-and-forward (DF) relay with infinite buffer and one external eavesdropper overhearing both the source-relay and relay-destination links. To ensure the security of both links, we design a new link selection scheme to assign the current time slot to the source-relay link, or the relay-destination link or no link based on the quality of both links as well as their relative quality. We then derive the closed-form expressions for both the secrecy throughput of the concerned network and the secrecy outage probability (SOP) of both links under the new link selection scheme. The optimal parameters of the proposed link selection scheme are further determined to maximize the secrecy throughput under the two SOP constraints. Finally, numerical results are provided to illustrate the impact of the SOP constraints on the optimal secrecy throughput.