I. Introduction

II. Physical Layer Security Coding

III. Physical Layer Security in Massive MIMO Systems

IV. Physical Layer Security for mmWave Communications

V. Physical Layer Security in Heterogeneous Networks

VI. Physical Layer Security of NOMA

VII. Physical Layer Security for Full Duplex Technology

VIII. Other Important Research Work

IX. Future Technical Challenges
A. Physical Layer Security Coding
C. Physical Layer Security for mmWave Communications
D. Physical Layer Security in Heterogeneous Networks
E. Physical Layer Security of NOMA
F. Physical Layer Security for Full Duplex Technology
G. Physical Layer Security for Other 5G Scenarios and Beyond

X. Conclusion