In this work, we propose a two-stage integrated sensing and communication (ISAC) framework for exploiting the benefits of utilizing ISAC's detection capability in covert communications. Specifically, in the first stage a full-duplex transceiver Bob detects the presence of a warden Willie while performing uplink transmissions to another transceiver Alice. Then, in the second stage Bob helps Alice's covert downlink transmission via jamming as per his detection outcome in the first stage. We optimally design the covert ISAC system to maximize the formulated overall covert rate subject to a covertness constraint, an average power constraint at Bob, and an uplink rate requirement. As shown in our examinations, the proposed two-stage framework significantly outperforms a benchmark scheme without the detection function in terms of achieving a higher covert rate. This, for the first time, explicitly demonstrates the superiorities of using ISAC's detection function to enhance covert communications.
In this work, we propose a two-stage integrated sensing and communication (ISAC) framework for exploiting the benefits of utilizing ISAC's detection capability in covert communications. Specifically, in the first stage a full-duplex transceiver Bob detects the presence of a warden Willie while performing uplink transmissions to another transceiver Alice. Then, in the second stage Bob helps Alice's covert downlink transmission via jamming as per his detection outcome in the first stage. We optimally design the covert ISAC system to maximize the formulated overall covert rate subject to a covertness constraint, an average power constraint at Bob, and an uplink rate requirement. As shown in our examinations, the proposed two-stage framework significantly outperforms a benchmark scheme without the detection function in terms of achieving a higher covert rate. This, for the first time, explicitly demonstrates the superiorities of using ISAC's detection function to enhance covert communications.
This paper investigates the covert communication in the scenario of counter detection. In traditional covert communication design where the uncertainty of the position of the Warden Willie typically reduces covert performance. To overcome this limitation, we leverage the sensing ability of the ISAC system in a new way to reduce the channel uncertainty between Alice and Willie, thereby enabling less conservative power allocation and significantly improving the achievable covert throughput. In the first stage, the dual functional sensing and communication (DFRC) base station Bob sends joint signals to estimate the azimuth of Willie and transmits information to Alice at the same time. In the second stage, Alice uses the obtained azimuth information of Willie to adjust transmit power while meeting the covert constraints. We build a mathematical model of azimuth angle estimation error and connect it with the Cramér-Rao Bound (CRB) to change it into distance error. This connects sensing accuracy with channel state information (CSI) uncertainty in a linear way, allowing Alice to adopt a higher transmit power while still satisfying the covert constraint, and thus improving the achievable covert throughput. To increase the covert throughput of the user, we use a layered solving strategy to decouple the original problem. First, we use S-procedure to change the constraint on possible distance error into a linear matrix inequality (LMI) constraint and then find the upper limit of transmit power on the user side. Second, we combine it with the uplink communication link rate constraint to find the closed form expression of the resource allocation strategy in vector space. Finally, we use one dimensional search to find the optimal time slot allocation strategy. Simulation results show that the proposed two-stage protocol effectively improves the achievable covert throughput by reducing position uncertainty through sensing.
This paper develops a two-phase secure integrated sensing and communication (ISAC) framework, where a dual-functional transmitter (Alice) detects the existence of a potential eavesdropper (Eve) as a sensing target in the first phase. In the second phase, Alice adapts her secure transmission strategy based on the sensing outcome of the first phase. A distinct aspect of our proposed two-phase framework is the derivation of the overall effective secrecy rate across both phases. This is achieved by seamlessly incorporating the a priori probability of Eve’s presence, the sensing false alarm rate, and the sensing detection probability directly into the effective secrecy rate as weighting coefficients. For system design, we aim to maximize the overall effective secrecy rate subject to Alice’s average transmit power remaining below a predetermined threshold. To address the resulting non-convex design problem, an algorithm based on semi-definite relaxation (SDR) and double-layer optimization is proposed. Our numerical results show that the proposed two-phase secure ISAC framework significantly enhances the secrecy rate compared to a conventional physical layer security (PLS) system if Eve is present with a low probability.
Emerging wireless applications pursue a paradigm shift towards the integrated system that is capable of secure data transmission and high-resolution sensing in near-field environments. Conventional far-field use-cases suffer from the fundamental limitations in security, spatial precision, and spectral coexistence. Against this backdrop, this paper investigates an integrated covert communications and sensing (ICCS) system operating in the near-field environment. Specifically, the transmitter (Alice) aims to covertly convey messages to legitimate receivers (Bobs), while circumventing the detection by the eavesdropper (Willie) as well as improving the sensing performance at the target. To elevate communication performance, we aim to maximize the achievable sum rate to jointly optimize the communication and sensing beamforming matrices at Alice. The optimization problem is subject to multiple constraints with coupled variables: the transmit power budget at Alice, the minimum communication rate requirements for Bob, the Crameˊr-Rao bound (CRB) constraint to ensure accurate parameter estimation in sensing, and the covertness constraint against Willie’s detection. Given the non-convex nature of the formulated problem, an efficient successive convex approximation and semidefinite relaxation algorithms are proposed. In addition, we provide a theoretical analysis to confirm the convergence behaviour of the proposed algorithm, which can achieve the near-optimal solution. Finally, the numerical results are presented to highlight the superiority of the proposed ICCS system over existing counterparts. These results numerically verify the effectiveness of the proposed approach in enhancing communication rates while maintaining sensing performance and covertness in the near-field regime.
The following paper models a secure full duplex (FD) integrated sensing and communication (ISAC) scenario, where malicious eavesdroppers aim at intercepting the downlink (DL) as well as the uplink (UL) information exchanged between the dual functional radar and communication (DFRC) base station (BS) and a set of communication users. The DFRC BS, on the other hand, aims at illuminating radar beams at the eavesdroppers in order to sense their physical parameters, while maintaining high UL/DL secrecy rates. Based on the proposed model, we formulate a power efficient secure ISAC optimization framework design, which is intended to guarantee both UL and DL secrecy rates requirements, while illuminating radar beams towards eavesdroppers. The framework exploits artificial noise (AN) generation at the DFRC BS, along with UL/DL beamforming design and UL power allocation. We propose a beamforming design solution to the secure ISAC optimization problem. Finally, we corroborate our findings via simulation results and demonstrate the feasibility, as well as the superiority of the proposed algorithm, under different situations. We also reveal insightful trade-offs achieved by our approach.
This paper studies the joint secure transceiver design for the full-duplex integrated sensing and communication (ISAC) system, in which the base station performs the target tracking and communicates with the downlink and the uplink users by reusing the resources. Here, the target, referred to as Eve, is a potential eavesdropper with the intention of intercepting both the downlink and the uplink information. The security problem of the full-duplex ISAC system has not been studied well, where the sensing and communication signals suffer from the serious interference. In this paper, we jointly design the information beamformer, the radar waveform, the uplink communication receive filter, and the radar receive filter to achieve the downlink and uplink communication security and the target tracking. Specifically, both the Eve’s signal-to-interference-plus-noise ratio minimization and the secrecy rate maximization problems, subject to the sensing and the communication constraints, are formulated for the ISAC system from the perspectives of the quality of service and the secrecy rate. An iterative algorithm is proposed for solving the formulated problems. We prove that, under appropriate conditions, the proposed iterative algorithm converges to the Karush-Kuhn-Tucker optimal point of the original problem without the rank 1 constraint. We further extend the joint design to the case of the imperfect wiretap channel and the angle uncertainty. Numerical results show that our scheme remarkably outperforms the benchmark approaches. The performance is close to that of designing the secure communication and the sensing separately.
This research investigates the feasibility of covert and reliable communication between Alice and Bob in the presence of a vigilant adversary, Willie, employing a jammer in a complex Gaussian channel. Alice strategically manipulates the noise-power ratio along the real and imaginary axes to disrupt Willie’s detection capabilities. Covertness constraints are quantified using KL divergence, and transmission performance is assessed through mutual information. Additionally, an optimization method is introduced to enhance covert communication by fine-tuning the amplitude gain and noise-power ratio. Numerical results confirm the effectiveness and superiority of the proposed method, showcasing its ability to maximize covert transmission rates.