Hybrid eavesdropping approach against energy-ratio-based detection

There is a growing need for government agencies to prevent crimes and terror attacks by legitimately monitoring suspicious communication links. In this paper, two concepts named eavesdropping rate and eavesdropping outage probability are defined to evaluate the eavesdropping performance of legitimate monitor. Against the energy-ratio-based detection exploited by suspicious users, a hybrid eavesdropping approach is proposed. The hybrid eavesdropping approach includes the passive eavesdropping and the active eavesdropping, and switches between them depending on the requirements of eavesdropping performance. Furthermore, two active eavesdropping schemes are given. One is to maximize the eavesdropping rate under pilot spoofing attack power constraint, the other is to minimize the pilot spoofing attack power of monitor by satisfying the eavesdropping rate requirements. The simulation results show that the proposed hybrid eavesdropping approach greatly outperforms conventional passive eavesdropping and pure pilot spoofing attack with constant power, since it increases eavesdropping rate and reduces eavesdropping outage probability significantly.