This research presents a comprehensive analysis of physical layer and cross-layer authentication schemes in the context of the Internet of Things (IoT) through a systematic literature review. The study evaluates the methods, as well as strengths and weaknesses of existing techniques in defending against prominent security threats, including eavesdropping, impersonation, and brute-force attacks. The findings underscore the challenges faced by physical layer authentication due to variations in features, rendering it unreliable despite its ability to offer enhanced security with minimal computational resources. In contrast, the integration of physical layer techniques into cross-layer authentication methods demonstrates promising results in mitigating these challenges. Despite such integration being one of the most common approaches to cross-layer authentication, we also evaluate other approaches that does not involve physical-layer authentication. There is also an emphasis on the fact that although hypothesis testing yields optimistic outcomes, assessing the impact on communication network latency, delay, and overhead in actual testbeds is essential.