In this paper, a physical layer security based secure routing problem in a multi-hop cognitive radio enabled device-to-device (CRD2D) communication, under the threat of multiple randomly distributed eavesdroppers (EVEs), is studied. Delivery of confidential packets between a given legitimate D2D transmitter–receiver pair is targeted with the aid of multiple intermediate legitimate D2D nodes that share spectrum of a predefined licensed$∕$primary user for their transmissions as unlicensed$∕$secondary users and operate on the principle of randomized-and-forward relaying. In view of the energy limitations of the D2D nodes engaged in IoT applications, the secure routing problem aims to maximize the secrecy energy efficiency (SEE) under the constraints of $-$ (i) minimum secrecy rate (ii) minimum signal-to-interference plus noise ratio at any D2D receiver (iii) maximum primary user outage loss in presence of the D2D transmission (iv) maximum retransmission attempts by any D2D nodes. Based on our analysis, an optimal routing algorithm is proposed. Simulation results illustrate the dependence of SEE on various critical system parameters. Further, complexity analysis and implementation issues are also presented for the proposed routing algorithm.

本文研究了在具有多个随机分布的窃听者（EVE）的威胁下，多跳认知无线电使能的设备到设备（CRD2D）通信中基于物理层安全性的安全路由问题。通过共享预定义许可频谱的多个中间合法D2D节点，可以在给定的合法D2D收发器对之间传输机密数据包$∕$主要用户的无许可传输$∕$二级用户，并按照随机转发中继的原则进行操作。考虑到从事物联网应用的D2D节点的能源限制，安全路由问题旨在在以下约束条件下最大化保密能源效率（SEE）：$-$（i）最小保密率（ii）任何D2D接收器的最小信号干扰加噪声比（iii）存在D2D传输时最大的主要用户中断损耗（iv）任何D2D节点进行的最大重传尝试。在分析的基础上，提出了一种最优路由算法。仿真结果说明了SEE对各种关键系统参数的依赖性。此外，还针对提出的路由算法提出了复杂性分析和实现问题。