Secure Full-Duplex Spectrum-Sharing Wiretap Networks With Different Antenna Reception Schemes

In this paper, we investigate the secrecy performance of full-duplex multi-antenna spectrum-sharing wiretap networks in which a jamming signal is simultaneously transmitted by the full-duplex secondary receiver (Bob) based on the zero forcing beamforming (ZFB) algorithm. For the security enhancement, we propose the two antenna reception schemes: 1) random selection combining (RSC) where Bob selects
$L_{\mathrm{B}}$
antennas at random to combine the received signals and 2) generalized selection combining (GSC) where Bob selects
$L_{\mathrm{B}}$
strongest antennas to combine the received signals. We derive the exact closed-form expressions for the secrecy outage probability of full-duplex multi-antenna spectrum-sharing wiretap networks with ZFB algorithm. In order to explore a new design of the proposed schemes, we provide tractable asymptotic approximations for the secrecy outage probability in high signal-to-noise ratio regime under two distinct scenarios. From the analysis, we demonstrate that: 1) when the main channel is much better than the eavesdropper’s channel, GSC/ZFB scheme achieves full diversity
$N_{\mathrm{B}}$
, while RSC/ZFB scheme only achieves partial diversity
$L_{\mathrm{B}}$
and 2) GSC/ZFB scheme achieves better secrecy performance than RSC/ZFB with different antenna numbers at Bob.