6G and Beyond Wireless Channel Characteristics for Physical Layer Security: Opportunities and Challenges

Security has emerged as one of the critical requirements of future wireless networks. Unlike traditional cryptography-based security, physical layer security (PLS) tends to exploit various features of the random wireless channel to secure not only the information being communicated but the whole communication process from any type of attack. Due to the limited capability of the legacy wireless networks, only a few channel features could be effectively exploited for PLS. Future wireless networks are envisioned to feature advanced transceiver technologies, signal processing techniques, channel control, and sensing capabilities which will allow them to easily access and extract additional channel features that can be readily exploited for PLS. The novel use cases to be accommodated in future networks are also found to experience some peculiar channel characteristics which enrich the list of channel features that can be exploited for PLS. This article, thus, tends to highlight the opportunities and potential challenges of these new channel features from the PLS perspective. In the course of the article, the assessment of important qualities while selecting a certain channel feature for the PLS application is discussed. The importance of the channel control concept and sensing technologies for PLS is highlighted. Finally, the article discusses the challenges and vulnerabilities of the channel-based PLS concept from which future research directions are derived.