1 Introduction  
2 Fundamentals of Physical Layer Security  
2.1 General System Model  
2.2 Performance Metrics  
3 Physical Layer Security Techniques  
3.1 Artificial Noise Generation  
3.2 Multi-Antenna Diversity  
3.3 Cooperative Diversity  
4 Next Generation Physical Layer Technologies  
4.1 Massive MIMO  
4.2 mm-Wave  
4.3 HetNets – Small Cells  
4.4 Full-Duplex  
4.5 Non-Orthogonal Multiple Access  
5 Conclusions and Future Research Directions