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.
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.
In this paper, we consider a covert communication system with a multi-antenna full-duplex (FD) receiver to enhance covert performance. More precisely, the receiver Bob (i.e., multiple antennas) selects the best antenna to receive the covert message, and then it sends artificial noise (AN) to the warden Willie causing uncertainty by utilizing an antenna among the remaining antennas. In order to take full advantage of multi-antenna technology, we consider two cases: (1) Willie does not know which antenna Bob chooses to send AN, and Willie knows only part of the channel information. (2) Willie knows which antenna Bob chooses to send AN, and Willie knows all the channel information. Based on the analysis of the optimal detection threshold, we derive the minimum detection error probability of the two cases. Furthermore, given the pre-determined convert constraints, the closed-form expression of the maximum effective convert rate is derived. When the power of AN sent by Bob is greater than that of covert message sent by the sender Alice, surprised research results are shown: (1) the detection error rate of case 1 is higher than that of case 2. (2) the effective covert rate of case 1 is always lower than that of case 2. The simulation results show that the proposed scheme is more conducive to sending covert messages for Alice; in addition, the numerical results imply that the maximum effective covert rate of the system using the multi-antenna FD receiver is significantly higher than that of the traditional dual-antenna FD receiver system.
This paper studies a scheme of optimal relay selection with cooperative jamming and optimal power allocation factor between forwarding relay and jammer.The traditional optimal relay selection scheme selects an optimal relay node to assist forward source information.Based on legitimate user and eavesdropper instantaneous channel state information, the proposed scheme selects two relay nodes to increase security against eavesdropper.The first relays to forward source information as traditional scheme.The second relays to send artificial noise as a friendly jammer.The relay operates in Decode-and-Forward strategy.The closed form expression of secrecy outage probability is derived.In addition, the optimal power allocation factor is given when the total relay transmit power is constrained.The simulation results verify that the proposed scheme can significantly improve system security performance compared with the traditional scheme.,
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 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.
We explore the influence of cooperative jamming on covert communication for integrated satellite–terrestrial relay networks (ISTRN) in this article, where one full-duplex relay is utilized to support communications and acts as a jammer to confuse eavesdroppers. A cooperative scheme is first proposed to efficiently achieve covert communication in this specific scenario. Further, the probability of detection error (PDE) is derived. Subsequently, the minimum PDE is calculated using the optimal detection threshold. Moreover, a closed-form expression of outage probability (OP) is acquired to quantify the system’s covert performance. Based on this, we design a power optimization algorithm to enhance the effective covert rate under covertness constraints. Lastly, numerical simulation results are given to verify the efficiency of our cooperative jamming scheme when interrupting the eavesdroppers. Notably, an optimal power allocation factor can be obtained, leading to a higher effective covert rate.
This paper adopts the antenna selection technique to enhance the covert rate in a wireless communication network comprised of a source, a destination , an external jammer and an eavesdropper. In the covert communication, the level of transmit power is low and hence a source with multiple antennas can be adopted to send the information toward the single antenna destination while concurrently, the jammer transmits an artificial noise signal. For this system model, we consider a scenario where the source is forced to select one or several of its antennas to transmit its confidential information due to its limited RF chains. Furthermore, we consider two different jamming scenarios to support our covert communication: 1) The destination is unable to cancel the jamming signal, 2) The destination can subtract the jamming signal. For such a communication network, our aim is to maximize the covert rate subject to power constraint and covert communication requirement. In the first scenario, the optimization problem is non-convex, and hence, it can be solved through using Difference of Convex function (DC) method while the optimization problem of the second scenario is intrinsically convex. Our numerical results show that the higher the number of selected antennas at the transmitter, the higher the covert rate will be achieved.