This paper investigates the information surveillance with a half-duplex legitimate monitor (E) for wireless-powered suspicious communication in Internet of Things networks, which consists of one suspicious power-beacon (PB),
Nbattery-free suspicious transmitters (STs) operating in orthogonal frequency bands (FBs) and one suspicious destination (SD). The suspicious communication includes two phases: in phase 1, the PB chooses one best ST and exhausts its power over the corresponding FB for the energy transfer; in phase 2, by exploiting the harvested energy, such ST uploads its suspicious message to the SD. Under this setup, a novel proactive eavesdropping scheme is proposed to maximize the eavesdropping success probability at E. Specifically, in phase 1, E assists energy transfer in random
KFBs, to deliberately increase the harvested energy of the corresponding
KSTs; in phase 2, E overhears in the same
KFBs and jams in the remaining
N−KFBs concurrently, to intentionally improve the interference levels of the SD in those
N−KFBs. We prove that, given
K, as E’s energy transfer power in phase 1 or jamming power in phase 2 increases: 1) the suspicious system will choose one of those unjammed
KSTs for information uploading with a higher probability, thus increasing the conditional probability of E’s eavesdropping and 2) the ratio of the selected ST’s transmit power and communication rate will improve, thus enhancing the decoding success probability of E concurrently. In addition, given E’s transmit power in phases 1 and 2, as
Kincreases, the conclusion of i) still holds, but the conclusion of ii) reverses. Hence, to maximize the objective, which is the product of the conditional probability of eavesdropping and the decoding success probability, interestingly there exists a fundamental trade-off in deciding both
Kand the power allocations in phases 1 and 2, and a simple search can be exploited to find the optimal solution. Numerical results show the effectiveness of our proposed scheme compared to competitive benchmarks.
This letter studies the legitimate surveillance with one half-duplex legitimate monitor (E) over the suspicious multichannel relaying system, where the suspicious transmitter (ST) and relay (SR) implement the optimal power allocation over all orthogonal channels under a joint sum-power constraint to maximize the communication rate of the suspicious system. Under this setup and considering that SR operates in amplify-and-forward (AF) or decode-and-forward (DF) mode, E aims to i) determine the optimal set of sub-channels for jamming and ii) optimize its jamming power over these sub-channels in order to deliberately force ST and SR reallocating power to the unjammed sub-channels to the most, so as to increase the perceived power of E over the unjammed sub-channels and then maximize the eavesdropping rate. In particular, for the AF case, the formulated problem is non-convex, for which the slack variables are introduced and successive convex approximation is exploited. For the DF case, some insights are provided for the optimization process. Results present the considerable gain of the proposed strategy compared to intuitive schemes.
This paper studies the proactive eavesdropping for the potential energy-constrained suspicious communication system with one full-duplex-enabled legitimate monitor. Specifically, for such a system, we consider the proactive eavesdropping over finite time blocks under the off-line framework. In each time block, the monitor first acts as the masked power beacon deliberately to proceed wireless energy transfer to the suspicious transmitter for its uplink data transmission, then adaptively executes jamming, passive eavesdropping or assisting strategy based on our provided exact channel condition with strict proofs. According to these adaptive strategies and considering the optimization of transmit power at the monitor, we aim to solve the problem of sum eavesdropping rates maximization over N (N ≥ 1 ) time blocks subject to limited power at the monitor, which is explained as a difficult mixed-inter nonlinear programming (MINLP) problem. Fortunately, it is shown that this MINLP problem can be divided into one jamming subproblem and one passive eavesdropping/assisting subproblem. To observe the achieve performance bound, we firstly exploit the exhaustive search based algorithm and block coordinate descent (BCD) based algorithm to solve these two subproblems, respectively. In addition, in order to decrease the time complexities, we further propose one jamming power efficiency sorting based heuristic algorithm and one signal-to-noise ratio (SNR) approximation based fast algorithm. Numerical results present the considerable gains brought from our proposed adaptive proactive eavesdropping strategy.
This letter studies proactive eavesdropping with one legitimate monitor (E) in the classical single-hop suspicious communication. Specifically, unlike all previous works that ignored the suspicious channel training phase and just considered the jamming power optimization of E in the suspicious data transmission phase to facilitate eavesdropping, this letter advances the research by comprehensively investigating the jamming power allocation of E in both phases, with the purpose of maximizing its eavesdropping success probability. Under this setup, we first derive an exact expression of the objective and reveal the existence of a fundamental trade-off in deciding the jamming power allocation, for which a simple one-dimensional search is employed to find the optimal solution. To simplify the analysis, we further derive a tight approximation of the objective and then develop a very fast alternating optimization algorithm to find the sub-optimal jamming power allocation. Moreover, we extend our analysis to the case where the channel state information is available at the suspicious transmitter via channel feedback. Simulation results demonstrate the effectiveness of our proposed scheme compared to competitive benchmarks.
This letter studies the proactive eavesdropping in a suspicious decode-and-forward relay system, where the suspicious communication is divided into transmitter-to-relay (ST-SR) phase and relay-to-destination (SR-SD) phase with partial channel selection over N ≥ 2 orthogonal channels, and the monitor (E) can only jam/overhear the E-SR/SR-E link over M ≤ N sub-channels for practicality. Under this framework, with strict proof we first theoretically present the impact of jamming power and number of jamming channels selected by E on its eavesdropping success probability (ESP), and then reveal a fundamental trade-off: given jamming power (number of jamming channels), jamming with more channels (power) reduces the suspicious rate for E to overhear more clearly, but degrades the preconditions for successful eavesdropping. Results verify our obtained conclusions and show that the proposed jamming-assisted eavesdropping scheme with simple search method achieves pretty good performance compared with some intuitive schemes.
Unlike passive eavesdropping, proactive eavesdropping is recently proposed to use jamming to moderate a suspicious link's communication rate for facilitating simultaneous eavesdropping. This paper advances the proactive eavesdropping research by considering a practical half-duplex mode for the legitimate monitor (e.g., a government agency) and dealing with the challenging case that the suspicious link opportunistically communicates over parallel fading channels. To increase eavesdropping success probability, we propose cognitive jamming for the monitor to change the suspicious link's long-term belief on the parallel channels' distributions and thereby induce it to transmit more likely over a smaller subset of unjammed channels with a lower transmission rate. As the half-duplex monitor cannot eavesdrop the channel that it is simultaneously jamming to, our jamming design should also control the probability of such “own goal” that occurs when the suspicious link chooses one of the jammed (uneavesdroppable) channels to transmit. We formulate the optimal jamming design problem as a mixed integer nonlinear programming (MINLP) and show that it is non-convex. Nevertheless, we prove that the monitor should optimally use the maximum jamming power if it decides to jam, for maximally reducing the suspicious link's communication rate and driving the suspicious link out of the jammed channels. Then we manage to simplify the MINLP to integer programming and reveal a fundamental trade-off in deciding the number of jammed channels: jamming more channels helps reduce the suspicious link's communication rate for overhearing more clearly but increases own goal probability and thus decreases eavesdropping success probability. Finally, we extend our study to the two-way suspicious communication scenario and show that there is another interesting trade-off in deciding the common jammed channels for balancing bidirectional eavesdropping performances. Numerical results show that our optimized jamming-assisted eavesdropping schemes greatly increase eavesdropping success probability as compared with the conventional passive eavesdropping.