Performance of Untrusted Amplify-and-Forward Relaying

In this paper, we analyze the secrecy outage performance of amplify-and-forward (AF)-based relay networks consisting of a source, a destination, and an untrusted relay, where each terminal has a single antenna and operates in a half-duplex mode. In this network, the common message is transmitted through the relay-path, and the private message is transmitted through the direct-path to keep the message from the untrusted relay which has a different security clearance from the source-destination pair. Specifically, we investigate the AF-based relay network with the untrusted relay, and we derive the exact secrecy outage probability in one-integral form as well as its lower bound in closed-form. Numerical results confirm that the derived secrecy outage probability of the AF-based networks is exact, and that the closed-form lower bound of the AF- based network is also very accurate.