# Review of Physical Layer Security in 5G Wireless Networks
## 3 Literature Review
We presume that various listeners wiretap the kth destination during both phases. The non-collusion and passive eavesdropping instances are taken into consideration, which is a typical premise in many different genres of writing. They recommend a two-stage locked hybrid beamforming technique in this study for a MIMO mm-wave relay eavesdropping system where the source and relay serve various destination nodes and the analog and digital beamforming designs are separated. In the second stage, the source employs the ZF technique to create an information signal digital beamforming matrix depending on the effective channel to remove interference between various destinations. [PERSON] et al. [15] improve physical layer security. This study suggests a brand-new channel training (CT) approach for a full-duplex receiver. The receiver, which has N B full-duplex antennas, simultaneously receives and sends a signal carrying information (AN). The receiver must estimate the self-interference channel before the data communication phase to limit the non-cancellable self-interference caused by the broadcast AN. In the proposed CT method, just a small number of internal pilot symbols are transmitted by the receiver. This covert CT technique efficiently reduces the eavesdropping capabilities by preventing an observer from estimating the jamming route from the observer to the receiver. Analytically, we investigate the secrecy outage chance due to eavesdropping for the proposed secret CT technique as well as the connection probability of the legitimate channel. Our analysis demonstrates that when the number of antennas at the eavesdropper is greater than one, the newly suggested secret CT method greatly outperforms the non-secret CT strategy that uses pilots who are known to the public. [PERSON], [PERSON] et al. [16] proposed that the fifth generation (5G) of mobile networks seeks to achieve previously unheard of levels of capacity and performance, including ultra-high data rates, ultra-wide radio coverage, vast numbers of concurrently connected devices, and ultra-low latencies. Millimeter-wave (mm-wave), device-to-device, machine-type, and vehicular communications are only a few of the novel wireless system possibilities covered by 5G. The worldwide wireless communications industry refers to fifth-generation wireless technology as \"5G\", and it aims to achieve multiple-fold improvements in crucial wireless communication areas. Major research institutions and businesses are looking into millimeter-wave (mm-wave) and THz frequencies and technologies in addition to traditional microwave frequencies. This paper proposes a special issue covering many of the technological issues that need to be resolved to usher in the 5G era, and they provide in-depth insights and encouraging outcomes. [PERSON] et al. [17] conducted the research that because of smartphones, the desire for high-definition multimedia content, and an increase in base stations, mobile wireless communication networks have seen a notable increase in data traffic in recent years (BS). Although many experts have worked to address this security issue in the 5G network, it is still unclear how sensitive data are protected in wireless connections. Opposed to cryptography, physical layer security offers two key advantages that make it a preferable option for the 5G network. The first benefit is that, in the event of illegal access to data in the 5G network, the physical layer security mechanisms employed would not be influenced by computing complexity. This suggests that no compromises or trade-offs would be necessary for the attained level of security. The physical layer security technique's tremendous scalability is its second benefit. Devices can be connected to a variety of nodes in 5G networks, each of which has a varied level of processing capability and power needs. Furthermore, because of the decentralized network architecture, devices tend to connect to or disengage from the network at different times. Cryptographic encryption for security would be challenging as a result.