Improving the Security of Spectrum-Sharing Wiretap Networks with Full-Duplex Technique

In this paper, we propose generalized selection combining/zero forcing beamforming (GSC/ZFB) scheme to improve the secrecy performance of spectrum-sharing wiretap networks with a full-duplex Bob. Specifically, the full-duplex Bob selects LB strongest antennas to receive the signals from Alice and simultaneously transmits jamming signals with the remaining (NB-LB) antennas based on ZFB algorithm. We first derive exact closed-form expression for the secrecy outage probability of full-duplex multi-antenna spectrum-sharing wiretap networks with GSC/ZFB scheme. Then, we derive tractable asymptotic expression for the secrecy outage probability, which reveals that there exists a secrecy outage floor for the proposed GSC/ZFB scheme in high SNR region. The simulation results demonstrate that the proposed scheme achieves better performance than traditional GSC scheme with half-duplex technique. In addition, different from the traditional GSC scheme, the secrecy performance of the proposed GSC/ZFB scheme is not always improved with the increase of LB under a given NB.