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Asia-Pacific Conference on Communications (APCC)

Impact of Channel Estimation Error on Covert Communication With Adaptive Power Control

Emmanuel Kwaning Kwakye, Taehoon Kim, Inkyu Bang

Published Nov 26, 2025• 0 citations
Publisher

Abstract

In covert communication, adaptive power control can help balance reliability and covertness, particularly when working with a cooperative jammer. Recent studies considering adaptive power control in covert communications typically assume perfect channel estimation at the transmitter. However, channel estimation is imperfect in practice, resulting in inaccurate power allocation with degraded covertness performance. This paper investigates the effect of channel estimation error on jammer-assisted covert communication. We model channel estimation error in covert communication and analyze its impact on the covertness throughput. Simulation results show that estimation uncertainty leads to degraded throughput compared to perfect channel state information (CSI).

DOI
10.23919/apcc64555.2025.11279732

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In covert communication, adaptive power control can help balance reliability and covertness, particularly when working with a cooperative jammer. Recent studies considering adaptive power control in covert communications typically assume perfect channel estimation at the transmitter. However, channel estimation is imperfect in practice, resulting in inaccurate power allocation with degraded covertness performance. This paper investigates the effect of channel estimation error on jammer-assisted covert communication. We model channel estimation error in covert communication and analyze its impact on the covertness throughput. Simulation results show that estimation uncertainty leads to degraded throughput compared to perfect channel state information (CSI).
In jammer-assisted covert communication scenarios, jamming signals also degrade the communication between legitimate users. Considering that it is difficult for a transmitter to obtain all the required channel state information (CSI), we propose an adaptive power control strategy with partial CSI, which decreases the outage probability while bringing more uncertainty to a warden. Specifically, we adopt an upper confidence limit to estimate the unknown CSI from the jammer to the receiver. Under warden’s optimal detector, we analyze the maximum covert throughput by optimizing the upper confidence limit. A closed-form expression of the optimized upper confidence limit is derived in certain cases. The numerical results validate the effectiveness of the proposed strategy and guide the estimation of unknown CSI.
This paper considers the problem of covert communication over a multiple-input single-output channel (MISO) in the case of the imperfect channel state information. The transmitter wants to communication with the receiver while the eavesdropper detects the existence of the transmission. We first study the scenario that the accurate channel state information (CSI) is known and show that the condition achieving the positive rate by the beamforming vector. However, because of the non-cooperation between the transmitter and the eavesdropper, we consider the CSI is imperfect. There are estimation errors for the transmitter. When the positive rate can not be achieved, the objective is to maximize the communication rate. We discuss the deterministic bounded CSI errors for the covert communication. Robust beamforming and the transmitter power is investigated, which can be transformed as a second order cone programming (SCOP) problem. We consider the line-of-sight (LoS) channel and the linear array antenna model. Comparing with the perfect CSI, the results show that the strategy of the transmitter is more conservative under the imperfect CSI. The capacity declines by the estimation errors.
Covert communication is achieved if a transmitter (Alice) sends a message to a legitimate receiver (Bob) without being detected by an attentive warden (Willie). Recent work has taken an outage approach that considers an infinite blocklength and analyzes the probability that channel conditions are such that communication is reliable and/or covert. Power adaptation via truncated channel inversion (TCI) has been examined in previous work in an attempt to minimize outage under the covertness constraint. However, the optimality of TCI was not established, and the associated parameters in the TCI scheme were only found numerically. We provide the exact optimal power adaptation schemes under different covertness constraints and with different channel models: 1) when the channel between Willie and an uninformed jammer is AWGN; and 2) when the channel is a Rayleigh fading channel. We also examine the performance improvement of these schemes over standard approaches. This establishes that TCI is optimal in some, but not all, scenarios of interest.
The study of the fundamental limits of covert communications, where a transmitter Alice wants to send information to a desired recipient Bob without detection of that transmission by an attentive and capable warden Willie, has emerged recently as a topic of great research interest. Previous work has assumed that the distribution of the multipath fading on the channel, which we term the channel distribution information (CDI), is known to Alice, hence facilitating her characterization of Willie's capabilities to detect the signal. However, in practice, Willie tends to be passive and the environment heterogeneous, implying a lack of signaling interchange between the transmitter and Willie makes it difficult if not impossible for Alice to estimate the CDI exactly and provide covertness guarantees. In this paper, we address this issue by developing covert communication schemes for various assumptions on Alice's imperfect CDI: 1) when the transmitter knows the channel distribution is within some distance of a nominal distribution; 2) when only the mean and variance of the channel distribution are available; 3) when Alice knows the channel distribution is complex Gaussian but the variance is unknown. In each case, we formulate new optimization problems to find the power allocations that maximize covert rate subject to a covertness requirement under uncertain CDI. Moreover, Willie may be able to estimate CDI exactly or be faced with an error in estimation, and we investigate two these issues. Numerical results are presented to compare the proposed schemes from various aspects, for attaining desirable covert system performance.
Covert or low probability of detection communication is crucial to protect user privacy and provide a strong security. We analyze the joint impact of imperfect knowledge of the channel gain (channel uncertainty) and noise power (noise uncertainty) on the average probability of detection error at the eavesdropper and the covert throughput in Rayleigh fading channel. We characterize the covert throughput gain provided by the channel uncertainty as well as the covert throughput loss caused by the channel fading as a function of the noise uncertainty. Our result shows that the channel fading is essential to hiding the signal transmission, particularly when the noise uncertainty is below a threshold and/or the receive SNR is above a threshold. The impact of the channel uncertainty on the average probability of detection error and covert throughput is more significant when the noise uncertainty is larger.
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.