Luring the Enemy in Deep: Jamming-Assisted Legitimate Eavesdropping Over HARQ-Based Suspicious Communications

This paper investigates the wireless surveillance with a legitimate monitor (E) over hybrid automatic repeat request (HARQ) based suspicious communications between a suspicious transmitter (S) and a suspicious destination (D). Specifically, with the HARQ protocol, S uses at most $L \geq 2$ transmission rounds (TRs) for delivering the same message to D. Under this setup, E deliberately jams D at each TR to decrease its signal receiving quality, so as to induce S to consume more TRs for transmitting its message. Then, as a reward, E at these TRs can overhear the suspicious message from S more clearly. Our purpose is to maximize E's eavesdropping success probability, by allocating its jamming power at these $L$ TRs, subject to its power budget constraint. The problem is highly non-convex. To solve it, we first exploit the general successive convex approximation (SCA) approach to determine the iterative solution. Considering the large complexity of the SCA-based approach, we further develop an easy-to-implement Lagrange multiplier method to find the sub-optimal solution. Numerical results show that the proposed schemes increase the eavesdropping success probability as compared with several benchmarks.

Automated summary

This paper investigates wireless surveillance using the HARQ protocol between a suspicious transmitter (S) and a suspicious destination (D) with a legitimate monitor (E). It aims to maximize E's eavesdropping success probability by allocating jamming power to decrease D's signal quality, inducing S to consume more transmission rounds.