Proactive Eavesdropping in Underlaid D2D Communication Networks

This paper considers the legitimate proactive eavesdropping in the underlaid device-to-device (D2D) communications networks. In such network, a dedicated node working in the full-duplex mode monitors a pair of suspicious D2D users, and transmits its own information to the base station at the same time. We formulate a beamforming design problem for the monitoring node to maximize its transmitting rate while guaranteeing the success of surveillance. As the problem is non-convex, we first transform it into a semi-definite problem via semi-definite relaxation and obtain an optimal solution to the transformed problem. For low-complexity implementation, we propose another scheme based on zero-forcing and max-ratio-transmitting beamforming methods. For simulation results, we show that compared to the passive eavesdropping, the two proposed beamforming schemes can improve the achievable legitimate transmitting rate and guarantee the non-outage probability of surveillance.