Covert Monitoring for D2D-enabled Cellular Networks

This paper studies the covert monitoring performance for a device-to-device (D2D)-enabled cellular network, consisting of a cellular user Alice, a base station BS, a legal monitor and a suspicious D2D pair. In such a network, a suspicious D2D transmitter intends to transmit message to its receiver, while the legitimate monitor attempts to eavesdrop the messages of the D2D communication. The cellular user Alice assists the legitimate monitor to covertly send signal (AN) to interfere with the D2D suspicious receiver (Dr). To this end, we first study the effects of uncertain channel of suspicious link and interfering link when the suspicious receiver Dr detects whether Alice transmits AN to it or not. Then we derive false alarm probability, missed detection probability of Dr and expressions for optimal AN detection threshold and the average minimum detection error probability. Finally, we maximize the non-outage probability with the constraint of covert requirement by optimizing power of Alice.