This work investigates the problem of finite blocklength covert communications with relay assistance in Internet of Things (IoT) to extend the communications range. We reconstruct the framework for analyzing covert communications under decoded and forwarded protocols based on Willie’s optimal detection method. The analytic expression of Kullback-Leibler (KL) divergence is derived, the upper bound of KL divergence is solved by using the convexity of KL divergence, and the strict covertness constraint of the system is obtained. Meanwhile, to maximize the effective throughput, a covert communication parameter configuration scheme is proposed. Theoretical analysis and simulation results indicate that the compromised relationship of transmit power between Alice and relay nodes, and a reasonable power allocation scheme can enhance the effective throughput of the system.
This work investigates the problem of finite blocklength covert communications with relay assistance in Internet of Things (IoT) to extend the communications range. We reconstruct the framework for analyzing covert communications under decoded and forwarded protocols based on Willie’s optimal detection method. The analytic expression of Kullback-Leibler (KL) divergence is derived, the upper bound of KL divergence is solved by using the convexity of KL divergence, and the strict covertness constraint of the system is obtained. Meanwhile, to maximize the effective throughput, a covert communication parameter configuration scheme is proposed. Theoretical analysis and simulation results indicate that the compromised relationship of transmit power between Alice and relay nodes, and a reasonable power allocation scheme can enhance the effective throughput of the system.
Covert communication enhances the security of information transmission by protecting communication behavior, which has been widely investigated in various wireless communication systems. In this paper, we develop a covert Internet of things (IoT) network, where energy-limited IoT nodes selectively transmit information or artificial noise based on channel state information. Specifically, if the channel gains of all legitimate links are less than a given threshold, the energy-limited node emits artificial noise, otherwise, it transmits covert information. Meanwhile, we adopt the strategy of channel inversion power control (CIPC) to hide the location information of the nodes. Then, we derive Willie's detection error probability (DEP), propose an optimization problem for covert throughput, and obtain the optimal threshold and transmission energy. The results indicate that the probability of covert transmission significantly affects Willie's DEP. Moreover, the average covert throughput can be maximized by a relatively small threshold.
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.
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.
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.
Covert communication aims to enhance the security of the wireless communication by hiding the transmission behavior from the eavesdropper. In this paper, a spectrum mask-based multi-antenna covert communication strategy is proposed in Internet of Things (IoT) networks. Specifically, the transmitter superimposes its messages on the existing overt channel to prevent the transmission being detected by the adversary eavesdropper, which can significantly enhance communication covertness without the need for additional spectrum resources. To eliminate the interference cause to the existing overt channel, multi-antenna technology and improper Gaussian signaling (IGS) are leveraged at the covert transmitter. Moreover, maximum ratio transmission (MRT) is adopted at the covert transmitter can fully exploit the additional degrees of freedom (DoF) that the multi-antenna provides to achieve reliable and covert transmission. Firstly, the optimal detection threshold at the eavesdropper is analyzed, and minimum error detection probability is then calculated, which indicates the worst-case from the covert transmitter’s perspective. In this scenario, a joint transmit power and IGS factor optimization problem is proposed to maximize the covert throughput under the covertness constraints. Secondly, the optimization problem is divided into three subproblems based on the power relationship, then the optimal transmit power and IGS factor are solved, respectively. Finally, extensive simulation is executed to demonstrate that under the given covertness constraints, the proposed strategy can effectively improve the covert communication performance of the multi-antenna system in IoT networks.