In this paper, the physical layer security of a dual-hop underlay uplink cognitive radio network is investigated over Nakagami- ${m}$ fading channels. Specifically, multiple secondary sources $(S_{i})_{1\leq i \leq N}$ are taking turns in accessing the licensed spectrum of the primary users and communicating with a multi-antenna secondary base station ( ${D}$ ) through the aid of a multi-antenna relay ${R}$ in the presence of ${M}$ eavesdroppers $(E_{k})_{1\leq k \leq M}$ that are also equipped with multiple antennas. Among the remaining nodes, one jammer is randomly selected to transmit an artificial noise to disrupt all the eavesdroppers that are attempting to intercept the communication of the legitimate links, i.e., $S_{i}$ - ${R}$ and ${R}$ - ${D}$ . The received signals at each node are combined using maximum-ratio combining. Secrecy analysis is provided by deriving closed-form and asymptotic expressions for the secrecy outage probability. The impact of several key parameters on the system’s secrecy, e.g., transmit power of the sources, number of eavesdroppers, maximum tolerated interference power, and the number of diversity branches is investigated. Importantly, by considering two scenarios, namely (i) absence and (ii) presence of a friendly jammer, new insights are obtained for the considered communication system. Especially, we tend to answer to the following question: Can better secrecy be achieved without jamming by considering a single antenna at eavesdroppers and multiple-ones at the legitimate users (i.e., relay and end-user) rather than sending permanently an artificial noise and considering that both the relay and the destination are equipped with a single antenna, while multiple antennas are used by the eavesdroppers? The obtained results are corroborated through Monte Carlo simulation and show that the system’s security can be enhanced by adjusting the aforementioned parameters.

中文翻译：

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具有多窃听者的基于上行链路协作干扰的底层 CRN 的 PHY 层安全性分析

在本文中，在 Nakagami 上研究了双跳底层上行链路认知无线电网络的物理层安全性。 ${m}$ 衰落的频道。具体来说，多个二级来源 $(S_{i})_{1\leq i \leq N}$ 轮流接入主用户的授权频谱，并与多天线辅基站通信（ ${D}$ ) 借助多天线中继 ${R}$ 在......的存在下 ${M}$ 窃听者 $(E_{k})_{1\leq k \leq M}$ 还配备了多个天线。在剩余的节点中，随机选择一个干扰器来发送人工噪声来干扰所有试图拦截合法链路通信的窃听者，即， $S_{i}$ —— ${R}$ 和 ${R}$ —— ${D}$ . 使用最大比率组合来组合每个节点处的接收信号。通过导出保密中断概率的封闭形式和渐近表达式来提供保密分析。研究了几个关键参数对系统保密性的影响，例如源的发射功率、窃听者的数量、最大容忍干扰功率和分集分支的数量。重要的是，通过考虑两种情况，即 (i) 不存在和 (ii) 存在友好干扰机，可以为所考虑的通信系统获得新的见解。特别是，我们倾向于回答以下问题：通过考虑窃听者使用单个天线和合法用户使用多个天线，是否可以在不干扰的情况下实现更好的保密性（即，中继和最终用户），而不是永久发送人工噪声并考虑中继和目的地都配备单个天线，而窃听者使用多个天线？所得结果通过蒙特卡罗模拟得到证实，表明通过调整上述参数可以增强系统的安全性。