Secrecy performance analysis of artificial noise aided precoding in full-duplex relay systems

In Rayleigh fading channels, we investigate the secrecy performance of a full-duplex relay secure transmission system. To improve the secrecy capacity of the system and efficiently interfere the interception of the eavesdropper, the multiple-antenna source applies the artificial noise aided precoding (ANP) scheme to broadcast the intended signal and the artificial noise simultaneously, and the decode-and-forward relay operates in full- duplex mode. To improve the received signal-to-noise ratio (SNR), the multiple-antenna destination applies maximum ratio combining (MRC) strategy. In the presence of self-interference at the relay, the approximate closed-form expression of ergodic achievable secrecy rate (EASR) for any values of antenna number and the exact closed-form expression of EASR for large-scale antennas array were derived respectively. Both the theoretical analysis and numerical simulations show that the ANP combined with full-duplex scheme can achieve considerable secrecy performance gain.