A Survey on Physical Layer Security of Ultra/Hyper Reliable Low Latency Communication in 5G and 6G Networks: Recent Advancements, Challenges, and Future Directions

Ultra-reliable low latency communication (URLLC) is an innovative service offered by fifth-generation (5G) wireless systems. URLLC enables various mission-critical applications by facilitating reliable and low-latency signal transmission. Apart from reliability and latency, ensuring the security of URLLC data transmission has been a prominent issue in recent years. URLLC uses finite blocklength signals to achieve the stringent reliability and latency requirement which eliminates the possibility of using conventional complex secret key-based cryptographic techniques. In this regard, lightweight security mechanisms like physical layer Security (PLS) have emerged as a powerful alternative to the complex cryptographic security techniques for URLLC by exploiting the randomness of the wireless channel. Therefore, this survey presents a comprehensive and in-depth review of the state-of-the-art PLS enhancements utilized to unleash secure URLLC in 5G and upcoming sixth-generation (6G) wireless networks. Moreover, the survey discusses the impact of system design parameters on the PLS of URLLC. It also incorporates a detailed overview of the recent advancements in ensuring PLS for mission-critical applications, URLLC enabling technologies, and Machine Learning (ML) based intelligent PLS schemes for URLLC. Then, for the first time, the survey introduces the extended service class of URLLC in 6G, i.e., Hyper Reliable Low Latency Communication (HRLLC), and provides an outlook on the future security aspects while identifying various promising new technologies that can provide secure HRLLC in 6G. Finally, the survey discusses several key challenges and identifies interesting future research directions for developing efficient PLS schemes for 5G URLLC and HRLLC service in 6G wireless networks.