This paper investigates the covert communications in the wireless-powered two-way relay systems with energy harvesting. The primary task of the relay is to assist the source nodes on both sides in completing the legitimate communication. Based on this, relay attempt to transmit covert information to source nodes. With limited transmit power at the relay, a reliable transmission strategy is needed to against the warden, who detects whether the relay transmits the cover message or not. We first analyzed the detection error probability at the warden. Based on the detection performance of the warden, we propose a ratio-control transmit strategy for the relay, which can efficiently implement covert communication with the harvested energy while the warden has optimized the detection error probability.
This paper investigates the covert communications in the wireless-powered two-way relay systems with energy harvesting. The primary task of the relay is to assist the source nodes on both sides in completing the legitimate communication. Based on this, relay attempt to transmit covert information to source nodes. With limited transmit power at the relay, a reliable transmission strategy is needed to against the warden, who detects whether the relay transmits the cover message or not. We first analyzed the detection error probability at the warden. Based on the detection performance of the warden, we propose a ratio-control transmit strategy for the relay, which can efficiently implement covert communication with the harvested energy while the warden has optimized the detection error probability.
This article investigates covert communications in a multirelay Internet of Things (IoT) system with multiple energy harvesting jammers, where a transmitter (Alice) attempts to covertly transmit confidential messages to its destination (Bob) through relay forwarding, while a warden (Willie) detects the existence of Alice’s transmission. Specifically, we employ a harvesting-then-jamming protocol with which the jammers first harvest energy from Alice and then send jamming signals to interfere with Willie’s detection. We propose a relay and jammer selection strategy, namely quality of service (QoS)-aware selection, and use the random selection strategy as a comparison strategy. Under these two selection strategies, we derive the optimal detection threshold and minimum detection error probability at Willie, respectively. We then model the covert throughput performance and obtain the maximum covert throughput by jointly optimizing covert transmit power and jamming transmit power. Extensive numerical results are provided to illustrate the impacts of system parameters on covert throughput performance.
In the context of Internet-of-Things (IoT) applications, ensuring secure and covert wireless communication remains a critical challenge, especially when using energy harvesting relays. Moreover, the analysis of hardware impairments is a pivotal practical aspect in the evaluation of IoT communication networks. This paper investigates four scenarios to address security and covert communication. In the first scenario, the focus is on guaranteeing the security in the presence of hardware impairments. In this case, the external jammer transmits interference signals toward both the relay and Bob to prevent information leakage from the untrusted relay. However, in this scenario, since the state of the untrusted relay is always superior to that of Bob, security cannot be guaranteed under any network parameters. Accordingly, in the second scenario, to tackle this problem, a receiver equipped with the capability to transmit jamming signals (receiver jammer) is proposed, aiming to protect the communication against potential information leakage from the untrusted relay. In the third and fourth scenarios, the relay is considered a trusted node, and warden (Willie) is introduced into the system. Here, the external jammer plays a crucial role when transmitting interference signals simultaneously toward Bob, relay, and Willie to ensure communication security. This scenario incorporates covert communication designed to counter threats from Willie’s detection. Covert communication in these two scenarios is analyzed under the following two conditions: 1) When Willie has Channel State Information (CSI); 2) When Willie lacks CSI, in which case he equips himself with multiple antennas. Simulation results show that the proposed power allocation can enhance secure and covert communications, even in the presence of hardware impairments and a multi-antenna Willie. Moreover, it is shown that when Willie has CSI, the performance of covert communication is severely reduced.
Owing to the ever increasing of information privacy requirement, covert communication has gained more and more attention, whose effective range is limited by the trade-off between the covertness and the transmit power. Benefiting from the high mobility and easy deployment, unmanned aerial vehicles (UAVs) can be utilized to expand the range of covert networks. Thus, we propose a UAV-relayed covert communication scheme with finite blocklength to maximize the effective transmission bits from the transmitter to the legitimate receiver against a flying warden. The transmitter adopts the maximum ratio transmission and the relay performs Gaussian signalling 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 end-to-end 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.
Wireless systems are of paramount importance in enabling ubiquitous data transmission for various Internet of Things (IoT) applications. However, due to the broadcast nature and openness of wireless channels, such systems face inherent security challenges. Covert communication is an enabling technology for secure wireless communications while the Unmanned Aerial Vehicle (UAV)-assisted covert communication is particularly promising for enhancing covert performance. This paper investigates joint covert and secure communications in a two-hop UAV-assisted wireless system, where a source S transmits a covert message to a destination D with the help of an untrusted UAV, while being subject to detection by a warden W. We first design a covert transmission scheme for the proposed system with the considerations of both covert and secure constraints. We then develop theoretical models for the warden1detection error probability and the covert-and-secure rate (CSR) from S to D. Based on these models, we further explore the optimal power control for CSR maximization under both covertness and security constraints. Finally, numerical results are presented to validate the theoretical models and demonstrate the performance of covert and secure communications in the UAV-assisted system.
To address the inherent openness of wireless communication environments, covert communication has emerged as a promising approach to protect legitimate transmissions from unauthorized detection. This paper investigates a UAVassisted wireless covert communication system, where channel uncertainty is exploited to enable covert information transmission in the presence of active wardens acting simultaneously as jamming sources. We first model the indirect communication strategy between legitimate parties and characterize the detection behavior of an active warden. To achieve both covertness and communication efficiency, the transmit power of the devices and the hovering positions of UAVs are jointly optimized, subject to the dual constraints of maintaining a sufficient covert communication rate and ensuring a high detection error probability at the warden. Closed-form expressions for the wardens detection error probability and the achievable covert communication rate are derived. Furthermore, numerical optimization is employed to maximize the achievable rate under covertness constraints. Simulation results corroborate the theoretical analysis and demonstrate the effectiveness of the proposed scheme in enabling covert communication in jamming-assisted active warden scenarios.
Wireless systems are of paramount importance for providing ubiquitous data transmission for smart cities. However, due to the broadcasting and openness of wireless channels, such systems face potential security challenges. UAV-assisted covert communication is a supporting technology for improving covert performances and has become a hot issue in the research of wireless communication security. This paper investigates the performance of joint covert and security communication in a tow-hop UAV-assisted wireless system, where a source transmits the covert message to a destination with the help of an untrusted UAV. We first design a transmission scheme such that use UAVs to assist in covert communications while ensuring the security of covert messages. Then, we develop a theoretical model to derive the expressions for the detection error probability of the warden and the covert and security rate, and the maximum covert and security rate is optimized by power control under a given covertness and security requirements. Finally, numerical results are provided to illustrate our theoretical analysis and the performance of covert and security communication in such systems.