Secure communications in fixed gain untrusted relay networks

This paper investigates secure communications in fixed gain untrusted relay networks. Unlike the trusted relay, an untrusted relay may be an eavesdropper and also does not have the instantaneous channel state information (CSI) of the main link. We propose a destination aided secure transmission scheme. A closed-form of achievable secrecy rate of the proposed scheme is derived and the optimal power allocation between the information signal and jamming signal is also discussed. Simulations elaborately verify our theoretical results.