Underlay协同频谱共享系统中基于SDF-DZFB的物理层安全传输

协同中继传输不仅能改善认知用户的传输可靠性，而且也能增强认知用户物理层安全性。针对Underlay模式下多中继协同频谱共享认知无线网络，本文设计了基于选择译码转发和分布式迫零波束成形（SDF-DZFB）的物理层安全传输方案，其中，假设存在单个被动窃听节点窃听中继节点的发送信号，在认知用户发送端同时考虑峰值干扰温度约束和最大发射功率约束，中继和认知用户目的端都受到主用户干扰。在此情况下，分析了认知用户发送端分别到目的端（称为主链路）和到窃听节点（称为窃听链路）的等效信干噪比的统计特性，进而推导出系统安全中断概率性能的闭式表达式。为了揭示所提物理层安全传输方案的安全分集度性能，本文进一步分析了高信噪比条件下安全中断概率的渐近表达式。计算机仿真验证了本文的理论分析结果。 

SDF-DZFB-Based Physical-Layer Security Transmission for Underlay Cooperative Spectrum-Sharing Systems

Relay cooperative can not only improve the transmission reliability, but also has great potential to enhance the physical layer security for cognitive users. In this paper, we consider a cooperative spectrum-sharing underlay cognitive radio networks in the presence of one eavesdropper, where the transmission power of the secondary transmitter is constrained by the maximum transmission power and the peak interference power to the primary receiver, and both the relays and the secondary destination are interfered by the primary user’s co-channel interference. We design a selection decode-and-forward and distributed zero-forcing beamforming (SDF-DZFB) scheme for physical-layer security Transmission and investigate the statistical characteristics of the received signal to interference noise ratio (SINR) of the links from the secondary transmitter to the secondary receiver and from the secondary transmitter to the eavesdropper, respectively. Then, we derive the closed-form expression for secrecy outage probability over independent and identically distributed Rayleigh fading channels. Furthermore, to reveal insights into the impact on secrecy diversity order, the asymptotic secrecy outage probability is provided. Finally, simulation results are provided to validate our theoretical analysis.