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IEEE Systems Journal

Adaptive Jamming Power Control for Untrusted Relay Networks With Imperfect Channel Reciprocity

Kisong Lee, Jun‐Pyo Hong, Hyun-Ho Choi

Published Sep 5, 2019• 9 citations
Publisher

Abstract

In an untrusted relay network where a destination transmits a jamming signal to prevent an untrusted relay from recovering the data sent by a source, we consider imperfect channel reciprocity (ICR) between the relay and the destination. This ICR prevents the destination from removing jamming interference perfectly, meaning that transmit power of the jamming signal has a significant impact on the secrecy rate. In this article, we present a system model of an untrusted relay network with ICR, and verify that the secrecy rate is concave with respect to the jamming power. We derive an asymptotic optimal jamming power to maximize the secrecy rate in closed-form and propose an adaptive scheme for jamming power control (JPC). Numerical results show that the proposed JPC scheme achieves a near-optimal secrecy rate, as well as outperforming conventional schemes by controlling the jamming power adaptively. In particular, we note that to improve the secrecy rate, it is advantageous to reduce the jamming power to decrease the residual jamming interference as the reciprocity error increases or the channel between the relay and the destination improves.

DOI
10.1109/jsyst.2019.2937963

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In an untrusted relay network where a destination transmits a jamming signal to prevent an untrusted relay from recovering the data sent by a source, we consider imperfect channel reciprocity (ICR) between the relay and the destination. This ICR prevents the destination from removing jamming interference perfectly, meaning that transmit power of the jamming signal has a significant impact on the secrecy rate. In this article, we present a system model of an untrusted relay network with ICR, and verify that the secrecy rate is concave with respect to the jamming power. We derive an asymptotic optimal jamming power to maximize the secrecy rate in closed-form and propose an adaptive scheme for jamming power control (JPC). Numerical results show that the proposed JPC scheme achieves a near-optimal secrecy rate, as well as outperforming conventional schemes by controlling the jamming power adaptively. In particular, we note that to improve the secrecy rate, it is advantageous to reduce the jamming power to decrease the residual jamming interference as the reciprocity error increases or the channel between the relay and the destination improves.
This paper investigates a secure communication via an untrusted relay with channel estimation error, in which a destination-assisted jamming strategy is adopted to prevent the relay from recovering a source signal. In the presence of channel estimation error in the relay-to-destination link, a destination cannot decode the source signal as well as eliminate a jamming signal perfectly, which causes a serious degradation in secrecy performance. Therefore, it is required to propose an effective strategy to determine jamming power level for maximizing secrecy rate. Under the assumption of high transmit signal-to-noise ratio, we derive the closed-form expression of a suboptimal jamming power ratio and propose an adaptive jamming power allocation which can be operated in practical systems. Numerical results confirm that the proposed scheme outperforms the conventional scheme in terms of secrecy rate.
We investigate the effect of outdated channel state information (CSI) on the secrecy performance of wireless-powered untrusted relay networks, in which the relay is a potential eavesdropper. To keep the information secret from this untrusted relay, the destination sends a jamming signal to the relay when the source transmits an information signal. At the same time, the relay harvests energy from the radio-frequency power, and forwards the received signals to the destination using this harvested energy. To determine the proportions of energy harvesting and information processing, the relay makes use of relaying based on power splitting or time switching policy. Although the destination tries to remove the jamming signal from the relaying signal, it cannot cancel out the jamming signal perfectly due to imperfect channel reciprocity caused by the outdated CSI; this residual jamming signal therefore has a negative impact on secrecy performance. In this scenario, we derive the closed-form expressions for the outage probability and average secrecy rate, and find the jamming power ratio, power splitting ratio, and time switching ratio to optimize these secrecy performance metrics. The numerical results demonstrate the accuracy of our analysis, and show that the proposed secure relaying protocols achieve a near-optimal secrecy performance, as well as outperforming the conventional scheme without the jamming power control.
The objective of this paper is to maximize the secrecy rate in an untrusted relay network with imperfect channel state information (CSI). Considering bounded channel estimation error in cooperative jamming network, we optimize the power allocation for confidential and jamming signals to maximize the instantaneous secrecy rate. The upper and lower bounds of achievable secrecy rate are analyzed. The ergodic secrecy rate (ESR) is further derived to evaluate the maximum average secrecy rate. And the optimal power allocation is also studied based on ESR. Numerical results show optimal power allocation can increase both instantaneous secrecy rate and ESR, and at higher SNR, the impact of channel estimation error can be neglected for the maximum ESR, which is asymptotically approaches to the upper bound.
By taking a variety of realistic hardware imperfections into consideration, we propose an optimal power allocation (OPA) strategy to maximize the instantaneous secrecy rate of a cooperative wireless network comprised of a source, a destination, and an untrusted amplify-and-forward relay. We assume that either the source or the destination is equipped with a large-scale multiple antennas' system, while the rest are equipped with a single antenna. To prevent the untrusted relay from intercepting the source message, the destination sends an intended jamming noise to the relay, which is referred to as destination-based cooperative jamming. Given this system model, novel closed-form expressions are presented in the high signal-to-noise ratio regime for the ergodic secrecy rate and the secrecy outage probability. We further improve the secrecy performance of the system by optimizing the associated hardware design. The results reveal that by beneficially distributing the tolerable hardware imperfections across the transmission and reception radio-frequency front ends of each node, the system's secrecy rate may be improved. The engineering insight is that equally sharing the total imperfections at the relay between the transmitter and the receiver provides the best secrecy performance. Numerical results illustrate that the proposed OPA together with the most appropriate hardware design significantly increases the secrecy rate.
This work investigates the security issue of the energy-constrained untrusted relay network with imperfect channel reciprocity, where the relay without the built-in power supply can only scavenge energy from radio-frequency signals radiated by the source and destination. A hybrid power-splitting (PS)- and time-switching (TS)-based relaying (HPTR) protocol is presented to improve the degraded secrecy performance due to the incomplete self-interference cancellation at the destination. To evaluate the secrecy throughput (ST) of the studied system, the analytical expression of the secrecy outage probability under the delay-limited transmission mode and the closed-form lower bound of the ergodic secrecy capacity under delay-tolerant transmission mode are derived. Both linear and nonlinear models for the energy harvester at the relay are compared. The optimal PS and TS ratios are evaluated numerically. The theoretical derivations are validated by numerical results, revealing that the residual jamming has a negative effect on the secrecy performance of untrusted relay networks, which can be alleviated by the HPTR protocol. Besides, we compare the ST performance of the HPTR protocol with that of the PS and TS relaying schemes, and the results show that the HPTR protocol outperforms both PS and TS relaying protocols in terms of the ST.
In this paper, we investigate secure transmission in untrusted amplify-and-forward half-duplex relaying networks with the help of cooperative jamming at the destination (CJD). Under the assumption of full channel state information (CSI), conventional CJD using self-interference cancellation at the destination is efficient when the untrusted relay has no capability to suppress the jamming signal. However, if the source and destination are equipped with a single antenna and the only untrusted relay is equipped with N multiple antennas, it can remove the jamming signal from the received signal by linear filters and the full multiplexing gain of relaying cannot be achievable with the conventional CJD due to the saturation of the secrecy rate at the high transmit power regime. We propose in this paper new CJD scheme where neither destination nor relay can acquire CSI of relay-destination link. Our proposed scheme utilizes zero-forcing cancelation based on known jamming signals instead of self-interference subtraction, while the untrusted relay cannot suppress the jamming signals due to the lack of CSI. We show that the secrecy rate of the proposed scheme can enjoy a half of multiplexing gain in half-duplex relaying while that of conventional CJD is saturated at high transmit power for N ≥2. The impact of channel estimation error at the destination is also investigated to show the robustness of the proposed scheme against strong estimation errors.