Capacity Threshold-based On-off Transmission in mmWave Systems with Randomly Distributed Eavesdroppers

This paper investigates secure on-off transmission scheme of millimeter wave (mmWave) systems in the presence of randomly distributed eavesdroppers. To characterize spatially distributed eavesdroppers, a stochastic geometry approach is considered. We derive the closed-form expressions of secrecy outage probability (SOP) in term of non-cooperative eavesdroppers (NCE) and cooperative eavesdroppers (CE) scenarios, respectively. In addition, some asymptotic analysis of the SOP for the two scenarios has been given. Numerical results demonstrates that the blocking is beneficial for improving the secrecy performance in the capacity threshold-based on-off transmission scheme, and there is no obvious performance difference between NCE and CE scenarios in large blockage density environment. In addition, there exists an optimal transmit power to achieve the security of higher level in the on-off transmission scheme.