Secure on-off transmission in mmWave systems with randomly distributed eavesdroppers

Abstract

To meet ever-increasing mobile data traffic demands for next-generation wireless communication systems, the plentiful spectrum resources in millimeter wave (mmWave) band have been exploited to improve the system capacity. This paper investigates physical layer security of mmWave systems with different secure on-off transmission strategies in the presence of randomly distributed eavesdroppers, including capacity threshold-based on-off scheme, secrecy guard zone on-off scheme and hybrid on-off scheme. Considering the effect of mmWave channel characteristics, random blockages and directional beamforming antenna gains, new closed-form expressions of system performance for each transmission scheme in terms of transmitting probability and secrecy outage probability have been derived under stochastic geometry framework. Then, the effects of various network parameters on secrecy performance, e.g., the density of eavesdroppers and blocking parameter, and the number of antennas and transmit power are validated. The numerical and analysis results show that the secure on-off schemes can effectively improve the secrecy performance of mmWave systems. Furthermore, for the capacity threshold-based on-off scheme and hybrid on-off transmission scheme, blocking is beneficial for improving secrecy performance significantly.