Research Of Physical-Layer Security In Multiuser Communication Systems Based On MRT

Secure transmission of wireless communication is quite crucial in wireless networks. Combining the multi-user multi-antenna technology and cognitive radio technology as multi-user multi-antenna cognitive systems can not only improve the utilization of spectrum resources but also enhance the transmission reliability as well as secrecy capacity and achieve diversity and multiplexing gain. Consequently, related researches for transmission scheme, transmission performance and the physical layer security of multi-user multi-antenna systems and multi-user multi-antenna cognitive systems are of great significance.In this paper, in order to maximize the secrecy capacity, the secrecy performance of multi-user multiple-input single-output (MU-MISO) and multi-user multiple-input multiple-output multi-users (MU-MIMO) as well as MU-MISO cognitive systems and MU-MIMO cognitive systems via a maximal ratio transmission (MRT) scheme in Rayleigh fading channels is studied and some meaningful results are obtained.In Rayleigh fading channels, the transmission performance is studied in a MU-MISO and MU-MIMO downlink system considering the absence of an eavesdropper under the influence of interference sources. The closed expressions of the secrecy outage probability are obtained with the consideration of the imperfect channel state information (CSI) and the perfect CSI. Moreover, closed expressions of asymptotic results are derived in high signal-noise ratio (SNR) by Taylor series expansion. Simulation results verify the validity of the theoretical analysis.In Rayleigh fading channels, the transmission performance is studied in a MU-MISO and MU-MIMO downlink cognitive system and closed-form secrecy outage probability expressions as well as asymptotic results in high SNR are deduced under the imperfect and perfect CSI considering two transmit power constraints, i.e., the peak interference temperature and the maximum transmit power constraint. Simulation results match analysis results well which provides a good theoretical basis for designing and optimizing the secrecy performance scheme.