This article investigates the physical layer security (PLS) performance in an Energy Harvesting Underlay Cognitive Radio Network (EHUCRN). Firstly, the article examines the impact of parameters such as primary transmitter power, interference power threshold, and expected security level on EHUCRN's Secrecy Outage Probability (SOP). Then, based on the findings, the article evaluates the PLS performance of the system. The results indicate that increasing the primary transmitter power reduces the PLS performance while raising the interference power threshold improves PLS performance. Furthermore, increasing the expected security level decreases the PLS performance. Additionally, the percentage of time spent collecting energy increases within a small range, resulting in an increasing PLS performance up to a peak value. However, if this percentage continues to increase within a large range, the PLS gradually decreases. Moreover, the results demonstrate that the PLS performance in EHUCRN is low due to relatively high SOP values.

ABSTRACT This paper analyzes the security performance of underlay cognitive energy-harvesting relay radio networks (UCEHRRN) through the Monter-Carlo simulation results. The results clarify the influence of critical operating parameters on the security performance of the system. Furthermore, the security capabilities of UCEHRRN have been compared with those of the live transmission system. Moreover, many results show that the security performance of the system is significantly improved. Analysis of the results also shows that UCEHRRN is especially effective when the direct transmission system cannot achieve security due to objective reasons such as path loss, severe fading, and shadowing.

The fifth generation (5G) cellular network has been commercialized recently to fulfill the new demands such as very high data exchange rate, extra low latency and high reliability. Many new technologies have been introduced and exploited since the early of the 2010s. Among these emerging technologies, full-duplex relaying cognitive radio networks, device-to-device communications and cell-free massive multiple-input and multiple-output have been considered as promising technologies/systems for 5G and beyond. This work provides a comprehensive study on the concepts, advantages and challenges of the above-mentioned technologies. In addition, we also introduce four new research directions which are challenges of 5G and beyond.