# Cybersecurity Risk Analysis in the IoT: A Systematic Review
## 3 Literature Review
### Physical Layer Security Solutions for IoT Devices  
In the context of physical layer security, a study focused on improving secrecy-energy efficiency in a satellite-terrestrial integrated network by using secrecy-aware hybrid beamforming schemes. These schemes involved a multibeam satellite system sharing the millimeter wave spectrum with a cellular system. The goal was to maximize achievable secrecy-energy efficiency by jointly designing hybrid and digital beamformers at the base station and satellite, respectively. The researchers used a sequential convex approximation method to handle multiple ESs and converted the original problem into a linear one with matrix inequalities and second-order cone constraints. Their proposed robust beamforming design was shown to be effective and superior through simulations using realistic satellite and terrestrial downlink channel models [43]. In another study, the researchers focused on addressing two critical aspects of future satellite communications: security and energy efficiency. They investigated secure energy efficient beamforming in multibeam satellite systems, where each satellite user was vulnerable to eavesdroppers attempting to intercept confidential information. The researchers employed the signal-to-leakage-plus-noise ratio metric to derive closed-form normalized beamforming weight vectors. Additionally, they utilized the successive convex approximation method to efficiently solve the power allocation subproblem. By combining these techniques, they proposed an iterative algorithm to obtain suboptimal solutions for the design [44]. To meet the increasing demands of Internet-of-Things (IoT) devices, multiple access techniques have been a focus of research. A study aimed to maximize the overall data transmission rate in the system while satisfying signal-interference-plus-noise-ratio requirements for IoT devices and power constraints for the UAV and satellite. The optimization problem was initially non-convex, but the researchers used sequential convex approximation and first-order Taylor expansion to transform it into a solvable one with a rank-one constraint. They then developed an iterative penalty function-based algorithm to solve this transformed problem. Simulations were conducted, and the results showed that the proposed method effectively reduced mutual interference and improved the system's overall data transmission rate compared to existing benchmark schemes. In essence, the study focused on optimizing multiple access techniques for IoT devices in a satellite-UAV communication system to enhance overall performance and accommodate explosive access demands [45; 46; 47; 48; 49; 50; 51]. Whereas 6G networks offer customized end-to-end network services and support emerging cloud-edge applications, 5G networks do not. As the resource allocation problem in 6G is of utmost importance and requires more research attention, a study introduced an efficient resource allocation algorithm called TailoredSlice-6G. This algorithm is designed to enable tailored slices in 6G networks. When a slice request is received, the TailoredSlice-6G algorithm first identifies the slice resource type. Based on this information, it selects the most suitable sub-algorithm for resource allocation and slicing deployment. Each type of slice is associated with a specific resource allocation sub-algorithm incorporated into TailoredSlice-6G. A crucial aspect of the proposed algorithm is that each sub-algorithm is designed to operate within polynomial time, ensuring efficient and timely resource allocation for different slice types. In summary, the study focuses on addressing resource allocation challenges in 6G networks by introducing the TailoredSlice-6G algorithm, which allows for tailored end-to-end network services and supports diverse cloud-edge applications [52; 53; 54; 55; 56; 57]. This literature review section provides a comprehensive summary of the most important previous studies related to the cybersecurity of the IoT.