Secure Communication in Millimeter Wave Relaying Networks

The use of relay can expand the coverage of millimeter-wave (mmWave) signals, whereas it may increase the risk of information leakage due to the additional link from source to relay. In this paper, we consider a secure communication in the mmWave randomize-and-forward relaying system with multiple spatially random eavesdroppers. By leveraging the tools from stochastic geometry, we investigate the reliability/rate performance with security consideration. The closed-form expressions of secure connectivity probability, secrecy outage probability, and the first-order integral expressions of average achievable secrecy rate for both non-colluding and colluding eavesdroppers cases are derived. The simulation results are presented to verify our derivations and show that the secure connectivity probability of relay transmission is larger than direct transmission when the relay locates in an oval-like area and its range is related to the antenna gains of source and relay. Furthermore, the secrecy outage probability and average achievable secrecy rate can also be improved when the relay is closed to the midpoint between the source and the destination.