The underlay cognitive radio-based hybrid radio frequency / free-space optical (RF / FSO) systems have been emerged as a promising technology due to its ability to eliminate spectrum scarcity and spectrum under-utilization problems. Consequently, this work analyzes the physical layer security aspects of a cognitive RF / FSO hybrid network that includes a primary user, a secondary source, a secondary receiver, and an eavesdropper where the secret communication takes place between two legitimate secondary peers over the RF and FSO links simultaneously, and the eavesdropper can overhear the RF link only. In particular, the maximum transmit power limitation at the secondary user as well as the permissible interference power restriction at the primary user are also taken into consideration. All the RF links are modeled with $\alpha$-$\mu$ fading whereas the FSO link undergoes M\'alaga (M) turbulence with link blockage and pointing error impairments. At the receiver, the selection combining diversity technique is utilized to select the signal with the best electrical signal-to-ratio (SNR). Moreover, the closed-form expressions for the secrecy outage probability, probability of strictly positive secrecy capacity, and effective secrecy throughput are derived to analyze the secrecy performance. Besides, the impacts of fading, primary-secondary interference, detection techniques, link blockage probability, atmospheric turbulence, and pointing error are examined. Finally, Monte-Carlo simulations are performed to corroborate the derived expressions.
翻译:由于能够消除频谱稀缺和频谱利用不足问题,内置的认知性无线电式混合无线电频率/自由空间光学(RF/FSO)系统已成为一项大有希望的技术,因此,这项工作还分析了认知性RF/FSO混合网络的物理层安全方面,该网络包括一个初级用户、一个二级源、一个二级接收器和一个窃听器,其中两个合法的二级同龄人同时在RF和FSO链接上进行秘密通信,而窃听器只能旁听RF链接。特别是,二级用户的最大传输功率限制以及允许主要用户的干扰力限制也得到了考虑。所有RF混合网络的物理层安全方面都以美元为模型,而FSO链接是M+ALaga(M)与阻塞和点错误损伤相交错。在接收器中,选择混合多样性技术用于选择带有最佳电信号到RF链接的信号表达方式。此外,对二次用户的最大传输力限制以及允许的干扰力力限制以及主要用户的允许干涉力限制。所有RFSB链接都以美元为模型模型模型模型模型模型模型模型,此外, 保密性测测测测测测测测测测测测度的机的精确性概率的概率是准确性测测测测测测测测测测测测测测度的概率的概率的概率的概率的概率的概率。