Secrecy performance of MRT/RAS system with outdated CSI in MIMO wiretap channels

We analyze the impact of outdated CSI on the security performance in multi-input multi-output (MIMO) system, where the transmitter uses maximal-ratio transmission (MRT) and the receiver uses receive antenna selection (RAS). In our analysis, new closed-form expressions for the probability of the existence of a nonzero secrecy capacity and the secrecy outage probability are derived. Then, based on the exact expressions, we derive the asymptotic secrecy outage probability. These conclusions demonstrate that under the impact of the outdated CSI, the secrecy array gain suffered from some loss, while the receive diversity order is reduced to one and the transmit diversity order is not affected. Theoretical analysis is verified by our simulation results.