Joint transmit antenna selection and jamming for security enhancement in MIMO wiretap channels

In this paper, we propose an effective method with low feedback overhead and low signal processing cost for security enhancement in multi-input multi-output (MIMO) wiretap channels. Based on transmit antenna selection (TAS) protocol, the transmitter selects two antennas that maximizes and minimizes the instantaneous signal-noise-ratio (SNR) at the receiver, respectively. Then, the transmitter uses the antenna with maximum SNR (strongest-antenna) to transmit valid data, and uses the antenna with minimum SNR (weakest-antenna) to transmit jamming, simultaneously. We derive new closed-form expressions for the exact probability density functions (PDFs) of receivers' SNR, based on which the secrecy outage probability and the probability of non-zero secrecy capacity are characterized. We demonstrate that our proposed TAS-Jamming protocol offers higher secure performance than other existing TAS protocols when the SNR of transmitter-receiver channel is below a specific value. The numerical simulation results verify our analysis.