# Review of Physical Layer Security in 5G Wireless Networks
## 3 Literature Review  
[PERSON] and [PERSON] et al. [8] proposed that encryption is one practical method for preserving security and privacy in social networks. To prevent wireless leakage and boost information security, physical layer security is increased. Several academics are researching physical layer refuge in wireless complexes relevant to 5G. The performance of network security will be impacted by both physical and logical connections, and this study primarily focuses on the security challenges of the physical level in extensive social linkages. Part III summarizes the prospects for physical layer safekeeping in communal linkages,  
Figure 1: PRISMA flowchart. whereas Part IV discusses the challenges. Part II discusses the characteristics of physical layer security in large-scale social networks. The majority of security measures used in the design and actions of the current safety network are constructed on the encryption algorithm and key. This coordination of encryption operates beyond the physical level (in the MAC layer, linkage layer, application layer, etc.). The equation is used to express the safety amount in the MIMO scenario  
\[Cs=maxQ:Q\geq 0,Tr(Q)\leq P[log|I+HQHH|--log|I+GQGH|] \tag{1}\]  
In Equation (1) \(Cs\) is the channel capacity, \(Q\) is the input covariance matrix, and we assume that \(H\) and \(G\) are perfectly known as Alice and Bob. System layer, linkage layer, and cross-layer optimization could increase the level of physical layer refuge. However, the use of physical layer safety is still constrained by ideal assumptions. In this study, which serves as a review article, we suggest some new possibilities for physical security in 5G-based massive communal networks that we must highlight in subsequent research. [PERSON], L et al. [9] found that upcoming wireless applications will require an ultra-high data amount, an ultra-wide radio analysis, an ultra-large quantity of expedients, and an ultra-low invisibility, and the fifth generation (5G) network will be a critical facilitator in addressing these expectations. The popularity of numerous intelligent devices has fueled an extraordinary increase in data circulation in mobile wireless communication in recent years. For the 5G era, for instance, academic institutions are investigating reliable and effective wireless transmission technologies, such as the heterogeneous network (HetNet). In the 5G era, the HetNet is a promising design for network densification. The HetNet aims to deliver a system that is both spectrum and energy efficient and meets the dramatically rising data requirements of future wireless applications. We assume that the pico- and macrocells operate in the same frequency range. Macrocell HPN and picocell LPN positions adhere to independent homogeneity. Based on the knowledge from the domains of graph theory and stochastic geometry, the impact of the positions of HPNs and LPNs on physical layer security can be investigated. Massive MIMO systems are a developing research area that has piqued the interest of both academics and businesspeople. Consuming very huge antenna arrays (usually tens or even hundreds) at the transmitter and/or headset allows for the massive MIMO technique's advantages to be realized. The paper's main objective is to explain how the path to 5G is practically unavoidable and how this will have a significant impact on how physical layer security is designed. In this work, they described the technical difficulties brought on by HetNet, massive MIMO, and mm-wave communication while also identifying the scientific prospects. The innovative solutions created have the potential to significantly increase data secrecy and usher in a brand new security paradigm that is deserving of the 5G moniker. [PERSON] et al. [10] stated that for decades, the moment-generating function (MGF) has been a crucial component of announcement theory as a tool for assessing the effectiveness of communication systems in a variety of situations.