Short packet communications play key roles in the Internet-of-Things. Conventional Shannon’s coding theorem is not applicable for short packet communications, and the achievable rate in the finite blocklength regime is related to the blocklength and the decoding error probability. Contrary to conventional physical layer security, wireless information surveillance assumes that the communication users are suspicious users and the eavesdroppers are legitimate monitors, and proactive eavesdropping via jamming has been proposed to improve the eavesdropping performance. Existing works on proactive eavesdropping ignored the scenario when the suspicious users adopt the short packet communications. Thus, this paper tries to develop effective proactive eavesdropping schemes suitable for the short packet suspicious communications. Under the truncated channel inversion power allocation and the modified constant power allocation policies at the suspicious source, the problems of jamming power allocation for maximizing the monitoring success probability subject to the average transmit power constraint at the monitor are investigated. Based on the Dinkelbach-type algorithm, the Lagrange duality method and a novel tractable approximate expression for the decoding error probability, we derive suboptimal solutions to the problems. Simulation results demonstrate the effectiveness of the proposed solutions compared to various benchmark algorithms in existing literature.
This letter studies the proactive eavesdropping with one half-duplex legitimate monitor (E) over the wireless-powered multichannel suspicious system, where the suspicious transmitter (ST) proceeds energy harvesting from the power beacon and then communicates with the suspicious destination (SD) via N parallel channels. Under this setup, one jamming-assisted eavesdropping scheme is proposed to maximize the ergodic eavesdropping rate at E. Specifically, we first fix the number of jamming channels K at E, and then reveal that E should jam with maximum power over these K channels to force the ST to allocate more power over the other N - K channels, so as to maximally increase the perceived power at E over the corresponding N - K channels. Armed with this, to maximize the ergodic rate, the following work is only to find the optimal K with simple search. Moreover, one closed-form sub-optimal K is derived for practical implementation. Results present the great gain achieved by the proposed scheme compared to conventional passive eavesdropping and the effectiveness of the sub-optimal K.
There is a growing need for government agencies to monitor suspicious communication links to prevent crimes and terror attacks. In this paper, we study a legitimate surveillance scenario where a legitimate monitor aims to intercept the suspicious communication between a transmitter and a receiver over fading channels. The legitimate monitor can eavesdrop (decode) the information of the suspicious link only when its achievable data rate is no smaller than that at the suspicious receiver. In practice, the legitimate eavesdropping is challenging, especially when the legitimate monitor is far from the suspicious transmitter. To overcome this issue, we propose a new approach, namely proactive eavesdropping via cognitive jamming, in which the legitimate monitor purposely jams the receiver and changes the suspicious communication (e.g., to a smaller data rate) in order to overhear easily. In particular, we consider delay-sensitive and delay-insensitive applications for the suspicious transmission, under which the legitimate monitor maximizes the eavesdropping non-outage probability and the relative eavesdropping rate, respectively, by optimizing its jamming power allocation over different fading states subject to an average power constraint. We present efficient algorithms for optimally solving the formulated problems. Numerical results show that thanks to the cognitive jamming, the proposed proactive eavesdropping scheme greatly outperforms the conventional passive eavesdropping without jamming.
Proactive eavesdropping improves the wireless information surveillance performance by cognitively sending jamming signals to degrade the suspicious link condition. Current studies all considered that the suspicious users do not apply jamming to defend against the proactive eavesdropping. Contrary to that, this paper considers that a jammer sends jamming signals to degrade the eavesdropping link condition to protect the suspicious communications. A Stackelberg game framework is formulated to track the interactions between the jammer and the monitor and make strategy designs, where the monitor is the leader aiming at maximizing the successful eavesdropping probability and the jammer is the follower aiming at minimizing the successful eavesdropping probability. For the follower’s problem, the optimal jammer’s jamming power allocation policy with respect to the fixed monitor’s jamming power is derived based on the sum-of-ratios optimization. Then for the leader’s problem, the optimal monitor’s jamming power allocation policy is obtained via the bisection search method and the sum-of-ratios optimization. Some design insights are discussed from the obtained policies. The effectiveness of the proposed scheme is verified by simulation results. It is shown that the jamming from the jammer deteriorates the eavesdropping performance and the proposed scheme outperforms various benchmark schemes in existing literature.
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.
Proactive eavesdropping is an effective approach to legitimately surveil the suspicious communications. Current studies all considered that physical layer security (PLS) techniques such as the wiretap coding are not applied by the suspicious users (SUs) to protect their communications. Contrary to that, we consider that the wiretap coding in PLS is adopted by the SUs to defend against the proactive eavesdropping from the legitimate monitor over fading channels. Under the fixed power allocation (FPA) and the water-filling power allocation (WFPA) at the SUs, the problem of jamming power allocation at the monitor to maximize the relative eavesdropping rate under the average transmit power constraint is investigated. The optimization problem is solved by two nested optimizations, where the bisection search method is used in the outer optimization, and the Lagrange duality method and the successive convex approximation method are used in the inner optimization. Simulation results confirm the effectiveness of the proposed algorithms compared to various baseline algorithms. It is shown that the proposed algorithm under the WFPA at the SUs outperforms the one under the FPA at the SUs, and the monitor achieves lower relative eavesdropping rate when the SUs adopt a stricter secure transmission scheme.