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IEEE Internet of Things Journal

Secure and Covert Communication in Energy Harvesting Relay IoT Networks: Impacts of Hardware Impairments

Reza Aghaei, Moslem Forouzesh

Published Oct 31, 2025• 4 citations
Publisher

Abstract

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.

DOI
10.1109/jiot.2025.3627789

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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.
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.
This study investigates covert communication in the presence of a half-duplex amplify-and-forward (AF) relay, while accounting for transceiver hardware impairments. A cooperative jamming strategy and channel uncertainty are employed to achieve covertness. For a trusted relay, informed jammers mitigate the effect of artificial noise (AN) at the legitimate receiver and increase the warden’s uncertainty, thereby enhancing the covert rate. For an untrusted relay, the jammer must emit AN while the data signal is transmitted toward the untrusted relay to reduce the untrusted relay’s signal-to-interference-plus-noise ratio (SINR), which poses a challenge for deploying an informed jammer. The results show that, in both trusted and untrusted relay scenarios, increasing the transmit power yields only marginal performance gains due to hardware impairments, highlighting the importance of high-quality transceivers and compensation algorithms. Notably, under specific conditions, impairments in the legitimate receiver’s transmitter can slightly enhance performance in the trusted relay case, while in untrusted relay scenarios, impairments in any legitimate node degrade covert communication performance. Differences in hardware equipment quality between the transmitter (or retransmitter) and its associated jammer also affect the warden’s ability to detect the transmission.
Covert communication can prevent an adversary from knowing that a transmission has occurred between two users. In this article, we consider covert wireless communications in an Internet-of-Things (IoT) network with dense deployment, where an IoT device experiences not only the background noise but also the aggregates interference from other Tx devices. Our results show that in a dense IoT network with lower frequency AWGN channels, when the distance between Alice and the adversary Willie da,w= ω(n1/(2α)), Alice can reliably and covertly transmit O(log2√n) bits to Bob in n channel uses. In an IoT network with terahertz (THz) band, covert communication is more difficult because Willie can simply place a receiver in the narrow beam between Alice and Bob in order to detect or block their line-of-sight communications. We demonstrated that covert communication is still possible in this occasion by utilizing the reflection or diffuse scattering from a rough surface. From the physical-layer security perspective, covert communication can enhance the security of IoT network from the bottom layer.
In practice, Internet of Things (IoT) applications may face two different hostile attacks, i.e., overhearing the broadcasted data and detecting the presence of data communication. Previous works have assumed that only one of these attacks is present in the network and have addressed these attacks separately. In this article, we investigate the security of a simple but practical IoT-based point-to-point communication which is facing with the above-mentioned two attacks under some realistic assumptions. In other words, we aim to protect the data against two adversary nodes, namely Eve (who tries to capture the broadcasted data) and warden Willie (who tries to detect the presence of data communication between legitimate nodes). To tackle these attacks, we jointly employ the information-theoretic security and covert communication techniques. To hide information from Willies, we force the source to transmit its message in the selected time slot and the multiple-antennas cooperative jammer to inject jamming during all time slots contentiously which leads to deceive Eves and Willies jointly. To enhance the performance of this security design, we formulate an optimization problem, with the goal of maximizing the secrecy rate subject to power constraints at the source and jammer, while satisfying a covert communication requirement. Since the mentioned optimization problem is nonconvex, we propose an algorithm to solve it. Then, to obtain further insights, we extend our proposed system model to noncolluding and colluding Willies. Next, we study a practical communication scenario, where the source has uncertainty about Willie’s location and knows the channel state information (CSI) of Eves imperfectly. Our numerical results highlight that a more accurate estimation of Willie’s location has a more positive efficacy on the secrecy performance compared to the case with more accuracy of Eves’ CSI estimation.
We propose a new scheme to secure a wireless-powered untrusted cooperative-communication network, where a legitimate source node (Alice) transmits her information messages to a legitimate destination node (Bob) through the multiple amplify-and-forward untrusted relays. The relay nodes are assumed to be honest but curious nodes; hence, they are trusted at the service level but are untrusted at the information level. To reduce the energy consumption of the network, only one relay node is selected in each time slot to forward Alice's information signal. We assume a power-splitting-based energy-harvesting scheme, where each relay node splits its received signal into information and energy streams. Since the relay nodes are assumed to be untrusted at the information level, they attempt to decode the information intended to Bob while harvesting energy at the same time. When the relaying mode is selected, the scheme is realized over two non-overlapping time phases. To prevent any information leakage to the untrusted relay nodes, Bob and a cooperative jammer (John) inject jamming (artificial noise) signals during the first phase. During the second phase, the untrusted relay nodes that will not be forwarding the information signal must harvest energy to accumulate more energy to help Alice in future time slots. Moreover, the cooperative jammer will jam the untrusted relays to further power their batteries and prevent them from decoding the information-forwarding relay signal in case they decided to cheat and decode it. We model the battery state transitions at each relay as a finite-state Markov chain and analyze it. Our numerical results show the security gains of our proposed scheme relative to two benchmark schemes.
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.