This letter studies the proactive eavesdropping with one full-duplex monitor (E) in unmanned aerial vehicle (UAV)-enabled suspicious multiuser communications, which include downlink broadcasting (DB) and uplink multiple access (UMA). Under this setup, E aims to maximize its sum eavesdropping rate by overhearing the messages from the UAV and jamming the ground multiple suspicious users simultaneously (corresponding to DB), or vice versa (corresponding to UMA). However, as the jamming power of E varies, the suspicious UAV and users will adapt their deployment and power allocation patterns concurrently to maintain the benefits of the suspicious system, which will cause certain obstacles for E to grasp its accurate jamming effect. To tackle these challenges, we first fix the jamming behavior of E and accordingly figure out the adaptiveness of the suspicious system, armed with which we further exploit thestep characteristicof the eavesdropping rate to determine the optimal (sub-optimal) jamming power of E, and the complexity involved only increases linearly with the number of suspicious users and thus avoiding the tedious exhaustive search. Simulations verify the effectiveness of the proposed schemes compared to conventional benchmarks.
This letter studies the proactive eavesdropping with one full-duplex monitor (E) in unmanned aerial vehicle (UAV)-enabled suspicious multiuser communications, which include downlink broadcasting (DB) and uplink multiple access (UMA). Under this setup, E aims to maximize its sum eavesdropping rate by overhearing the messages from the UAV and jamming the ground multiple suspicious users simultaneously (corresponding to DB), or vice versa (corresponding to UMA). However, as the jamming power of E varies, the suspicious UAV and users will adapt their deployment and power allocation patterns concurrently to maintain the benefits of the suspicious system, which will cause certain obstacles for E to grasp its accurate jamming effect. To tackle these challenges, we first fix the jamming behavior of E and accordingly figure out the adaptiveness of the suspicious system, armed with which we further exploit thestep characteristicof the eavesdropping rate to determine the optimal (sub-optimal) jamming power of E, and the complexity involved only increases linearly with the number of suspicious users and thus avoiding the tedious exhaustive search. Simulations verify the effectiveness of the proposed schemes compared to conventional benchmarks.
We investigate proactive eavesdropping with one half-duplex legitimate monitor (E) in unmanned aerial vehicle (UAV)-enabled suspicious relaying systems, which consist of a suspicious transmitter (ST), a suspicious UAV-based relay (SU) and a suspicious destination (SD). Under this setup, we propose two jamming-assisted eavesdropping strategies, namely, “Eavesdrop-Then-Jam” (ETJ) and “Jam-Then-Eavesdrop” (JTE), to maximize the eavesdropping throughput of E. Specifically, for ETJ, E first eavesdrops the suspicious signal of the ST in the ST-SU phase and then jams the SD in the SU-SD phase; for JTE, E first jams the SU in the ST-SU phase and then eavesdrops the suspicious signal of the SU in the SU-SD phase.However, in both strategies, as the jamming power of E (independent variable) changes, the SU can also adaptively adjust its deployment (dependent variable) to maximize the benefit of the suspicious system. Facing this challenge, we can only employ the undesirable exhaustive search over both the independent and dependent variables to achieve the optimal solution. To decrease the complexity, we further derive a tight approximation of the Lambert function and then develop easy-to-implement algorithms to find the sub-optimal solutions. Numerical results demonstrate the effectiveness of our proposed strategies compared to conventional passive eavesdropping.
This letter studies the Unmanned Aerial Vehicles (UAVs)-assisted proactive eavesdropping in the suspicious amplify-and-forward multi-relay system, where the suspicious transmitter based on opportunistic relaying protocol selects one best suspicious relay to communicate with the suspicious destination. In addition, we assume each UAV hovers over one specific relay for the purpose of jamming or eavesdropping, which is only valid for this relay due to the limited coverage of the UAVs and the dispersion between these relays. Moreover, the UAVs used for jamming cannot implement eavesdropping concurrently due to the half-duplex constraints. Under this setup, with detailed analysis and strict proof, we find an interesting trade-off in deciding the number of UAVs used for jamming: jamming with more UAVs helps decrease the suspicious rate to facilitate the eavesdropping by remaining UAVs, but is at the cost of degrading the precondition of successful eavesdropping. Numerical results verify this trade-off and show that with simple one-dimensional search, the proposed jamming-assisted strategy achieves significant gain compared to conventional passive eavesdropping.
In this paper, we study the robust secure unmanned aerial vehicle (UAV) communication system, where a UAV with full-duplex (FD) capability simultaneously receives the information signal from a ground unit (GU) and transmits jamming signal to degrade the wiretap capability of potential multiple ground eavesdroppers (Eves). With the consideration of estimation error of Eves' locations, we aim to maximize the average worst secrecy rate inside a certain flight period of the UAV by jointly optimizing the transmit power of the GU and UAV as well as the trajectory of the UAV. The resulting problem is intractable due to its non-convex nature and strongly coupled variables. Furthermore, the estimation error of Eves' locations results in an infinite number of constraints, which makes the problem even more difficult. To tackle this difficulty, we first propose an iterative algorithm based on the Schur complement lemma and successive inner approximation method to efficiently solve the problem suboptimally under the estimated Eves' locations. Then, in order to cope with the of Eves' location errors, we develop a cutting-set method, which solves the problem by alternating between optimal power-trajectory design and worst-case Eves' locations analysis. Via simulation, we show the improvement of the proposed algorithm compared to other benchmark algorithms under high FD self-interference cancellation levels.
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.
Unmanned aerial vehicle (UAV) wireless communication has recently been recognized to be inevitable and prevalent in the fifth-generation (5G) wireless networks. In this paper, we propose a secure transmission scheme for a wiretap channel, where a source communicates with a legitimate UAV in the presence of an eavesdropper. We consider the full-duplex active eavesdropper, which performs both eavesdropping and malicious jamming simultaneously. The source transmits artificial noise (AN) signals, in addition to information signals, to confuse this eavesdropper. By considering the ground-to-UAV channel model, we analyze the hybrid outage probability, which takes both the transmission outage probability and the secrecy outage probability into consideration. We further provide the asymptotic hybrid outage probability in a more compact form, where both the transmit power at the source and the jamming power at the eavesdropper become large with a fixed ratio. Through the analysis and the numerical results, we determine the optimal power allocation factor between information signals and AN signals as well as the operating height of UAV that minimize the hybrid outage probability. We also provide the most harmful antenna configuration of the eavesdropper to the UAV communications, and this paper can be a useful framework for the design of confidential UAV communication system.
This paper studies a legitimate proactive eavesdropping scenario where a central monitor covertly wiretaps the communications between suspicious users through a full-duplex multi-antenna relay. Specifically, the suspicious information is intercepted by the eavesdropping relay, and then encoded and forwarded to the central monitor. At the same time, the relay sends jamming signals to the suspect destination to reduce the quality of suspicious communication. To minimize the suspicious secrecy rate, the optimal forwarding and jamming beamforming vectors of the eavesdropping relay are first designed. Based on this optimized result, the best power allocation ratio is obtained. To this end, the optimal beamforming vectors and power allocation ratio are derived in closed-form. The simulation results verify the existence of the optimal forwarding power of the relay and show that the proposed scheme achieves better performance than the conventional schemes.