Proactive Eavesdropping via Pilot Contamination and Jamming

Proactive eavesdropping is a new paradigm shift in wireless physical layer security from preventing conventional eavesdropping attacks to legitimate intercepting suspicious communications, which has attracted a lot of attention recently. Pilot contamination is one effective technique in proactive eavesdropping, which spoofs the suspicious transmitter on channel estimation by sending the same pilot signal as the suspicious receiver, and lets it leak information in the direction of the legitimate eavesdropper during its transmission. However, this technique may fail when an anti-pilot-contamination mechanism called "energy ratio detector (ERD)" is applied at the suspicious receiver. To deal with the case that the suspicious receiver is a smart device using ERD, in this paper, we study using pilot contamination along with jamming to improve the legitimate eavesdropping performance. We first derive a closed-form expression for the probability of pilot contamination being detected by the suspicious receiver, and use it to obtain a closed-form expression for the eavesdropping rate. Using this theoretical analysis result, we propose an algorithm to maximize the eavesdropping rate by jointly optimizing the pilot contamination power and jamming power via two-dimensional search. Simulation results show that the proposed eavesdropping rate maximization algorithm can significantly improve eavesdropping rate, as compared to other benchmark schemes.