Feedback based two-phase transmission for secure SIMO communications

In this paper, we investigate the secure transmission in the single-input multiple-output (SIMO) wireless systems. Motivated by the existing destination-feedback schemes, and the utilization of artificial noise, a novel destination-feedback based two-phase transmission strategy is proposed to secure the SIMO communications. In the first phase, the multiple-antenna destination transmits both artificial interference and artificial noise on the backhaul links. In the second phase, the source utilizes the received interference signals to mask the confidential messages and emits the mixed signals to the destination. In the high signal-to-noise ratio (SNR) region, the lower bound of the worst-case ergodic secrecy rate is derived. Then we obtain the closed-form optimal power allocations that maximize the above lower bound. Moreover, we derive an analytical high-SNR approximation of the worst-case secrecy outage probability. Simulations are demonstrated to verify the secrecy performance analysis and corroborate the effectiveness of our scheme.