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IEEE Wireless Communications Letters

Joint Beamforming for Jammer-Aided MU-MISO Covert Communications With Finite Blocklength

Xing Lv, Manlin Wang, Zhen Ming Xu, Bin Xia

Published Jun 26, 2025• 2 citations
Publisher

Abstract

In this work, a jammer-aided covert communication system with finite blocklength is investigated, where we propose a joint beamforming strategy of the legitimate transmitter and the friendly jammer in spatial and temporal domains. Specifically, we first derive the warder’s detection performance using a novel covertness metric. Then, an optimization problem is formulated to maximize the minimum covert rate, and a successive convex approximation-based algorithm is proposed to obtain a near-optimal solution. Numerical simulations show that our proposed joint beamforming strategy outperforms several benchmarks and achieves more realistic performance for short packet transmission than the results with infinite blocklength.

DOI
10.1109/lwc.2025.3583439

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In this work, a jammer-aided covert communication system with finite blocklength is investigated, where we propose a joint beamforming strategy of the legitimate transmitter and the friendly jammer in spatial and temporal domains. Specifically, we first derive the warder’s detection performance using a novel covertness metric. Then, an optimization problem is formulated to maximize the minimum covert rate, and a successive convex approximation-based algorithm is proposed to obtain a near-optimal solution. Numerical simulations show that our proposed joint beamforming strategy outperforms several benchmarks and achieves more realistic performance for short packet transmission than the results with infinite blocklength.
In this work, the covert communication assisted by a probabilistic jammer is investigated in the finite blocklength regime, in which the jammer emits jamming signals with a certain probability to alleviate its negative effect on legitimate link but still enhance the covertness performance. Specifically, we first derive a tractable expression of covertness constraint based on the average KL divergence. Then, a closed-form expression of average decoding error probability (DEP) involving the effect of probabilistic jamming is presented. Moreover, joint optimization of transmit power and blocklength at the transmitter for maximizing the average effective covert throughput (AECT) is formulated and tackled, which demonstrates the trade-off between the transmit power and blocklength to improve covert communication performance. Our results show that the probabilistic jamming can indeed enhance the covert communication performance, and the jamming probability can be optimized to further improve the AECT.
In this paper, we investigate covert communication where the relay and the jammer are jointly selected. It is demonstrated that the improvement of covert communication performance can be achieved under the proposed maximum-and-minimum-selection (MMS) scheme. Specifically, the relay with maximal channel gain to the legitimate destination (Bob) is selected to forward the covert signal when the jammer with minimal channel gain to Bob sends artificial noise to confuse the warden (Willie). We derive the expressions of detection error probability and effective covert rate in closed-form. Based on the derivations, the transmit power of relay is optimized to further improve the covert communication performance. The simulation shows that the effective covert rate cannot always be improved by increasing the number of relay, and there exists an optimal jamming power to maximize the effective covert rate.
This work employs an unmanned aerial vehicle (UAV) as a jammer to aid a covert communication from a transmitter Alice to a receiver Bob, where the LAV transmits artificial noise (AN) with random power to deliberately create interference to a warden Willie. To maximize the system performance, we formulate an optimization problem to jointly design the UAV’s trajectory and Alice’s transmit power. The formulated optimization problem is non-convex that is difficult to tackle directly. To this end, this work, for the first time, develops a geometric (GM) method to solve the optimization problem. Our examination shows that the GM method can significantly outperforms a benchmark method in terms of achieving a higher average covert rate and the complexity of the GM method is lower than that of the benchmark method.
We propose a joint covert beamforming design and jamming strategy to protect the communication process between Alice and Bob from being discovered by Willie with the help of another pair of neutral nodes. Specifically, with the help of irrelevant communication parties that commonly exist in practical communication scenarios, Jammer increases his transmission power by interfering with the neutral receiver, thus indirectly increasing the interference to Willie, which can be viewed as leveraging the force to make a big impact with a small effect. In our designed beamformer, we jointly optimize the beam power allocation factor, Alice’s transmission power, and Jammer’s transmission power when Alice transmits, to maximize the covert rate, which also maximizes Alice’s transmission power. In the perfect channel state information (CSI) scenario, the transformed optimization problem is solved via a one-dimensional search method and CVX solver. Due to the solution’s high complexity, we further propose a method to determine the optimal power allocation factor. For the imperfect Willie’s CSI scenario, three cases are investigated: Alice to Willie imperfect CSI, Transmitter to Willie imperfect CSI, and Jammer to Willie imperfect CSI. We utilize the S-procedure to tackle the optimization problem. Simulation results demonstrate the effectiveness of our proposed strategy.
We propose a UAV-relayed covert communication scheme with finite blocklength to maximize the effective transmission rate from the transmitter to the legitimate receiver against a flying warden. The transmitter adopts the maximum ratio transmission and the relay performs Gaussian signaling transmission to cause uncertainty at the warden. First, the optimal detection thresholds are derived at the warden towards the transmitter and the relay, respectively. Then, the hovering location of the warden is optimized to maximize the summation of relative entropies from the transmitter and the relay, which can greatly threaten the covertness. With this worst covert situation, the blocklength and transmit power at the transmitter and the relay are jointly optimized under the constraint of the error detection probability to maximize the effective transmission rate from the transmitter to the legitimate receiver. Numerical results are provided to demonstrate the effectiveness of the proposed UAV-relayed covert communication scheme.
This paper considers the physical layer security (PLS) and covertness of the signal transmission in a multiple-input single-output downlink adopting ultra-high reliability and low latency communication (URLLC). In the considered system, Alice transmits confidential signals to Bob in the presence of a multi-antenna eavesdropper (Eve) and a multi-antenna watchful adversary (Willie). Although artificial noise (AN) is a common PLS technique for protecting the confidential signal from wiretapping, it may reduce the communication covertness due to the additional signal emission. For maximizing the achievable secrecy rate, we propose an AN-aided secure and covert communication strategy through optimizing the information carrying beamformer and AN jointly subject to the covertness constraint. To tackle the formulated non-convex design problem, we propose a branch-reduce-and-bound (BRB)-based algorithm to solve the considered problem globally. Simulation results validate its efficiency compared with a benchmark algorithm and unveil the importance of exploiting AN.