To protect data communication from eavesdropper nodes, different techniques have been developed to improve the physical‐layer security (PLS) of communications systems. Destination‐based cooperative signalling (DBCS) is one of such techniques where the destination sends an intended artificial noise to the untrusted listeners helping to protect the source message from being captured reliably at eavesdroppers. In this study, the authors investigate the application of DBCS to improve the PLS, and as a consequence the secrecy performance of a two‐hop amplify‐and‐forward cooperative system with an untrusted relay. To get the best performance out of DBCS, the transmit power of the source's signal as well as the artificial noise should be carefully adjusted. To address this, they have introduced the optimal power allocation to maximise the secrecy rate of the system under a sum‐power constraint at the network nodes. For a system with large‐scale antenna arrays at the base station, then then find the closed‐form solution for the secrecy outage probability and the ergodic secrecy rate of the optimised system for both uplink and downlink. The presented simulation results validate the authors’ theoretical analysis and reveal that the proposed DBCS with optimal power allocation significantly improves the secrecy performance of the system.
To protect data communication from eavesdropper nodes, different techniques have been developed to improve the physical‐layer security (PLS) of communications systems. Destination‐based cooperative signalling (DBCS) is one of such techniques where the destination sends an intended artificial noise to the untrusted listeners helping to protect the source message from being captured reliably at eavesdroppers. In this study, the authors investigate the application of DBCS to improve the PLS, and as a consequence the secrecy performance of a two‐hop amplify‐and‐forward cooperative system with an untrusted relay. To get the best performance out of DBCS, the transmit power of the source's signal as well as the artificial noise should be carefully adjusted. To address this, they have introduced the optimal power allocation to maximise the secrecy rate of the system under a sum‐power constraint at the network nodes. For a system with large‐scale antenna arrays at the base station, then then find the closed‐form solution for the secrecy outage probability and the ergodic secrecy rate of the optimised system for both uplink and downlink. The presented simulation results validate the authors’ theoretical analysis and reveal that the proposed DBCS with optimal power allocation significantly improves the secrecy performance of the system.
In this paper, the authors deal with secure transmission in two‐hop amplify‐and‐forward network with untrusted relays. To prevent the untrusted relays from intercepting the source message and to achieve positive secrecy rate, the destination‐based cooperative jamming technique is used. The authors propose joint secure best relay selection (BRS) and optimal power allocation (OPA) for uplink transmission of a cellular network when the base station is equipped with very large‐scale antenna arrays. Then, the common performance metrics such as ergodic secrecy rate (ESR) and secrecy outage probability are evaluated for the optimised network. Moreover, the diversity order and diversity‐multiplexing tradeoff of the system are examined. The authors obtain that the diversity order of joint BRS and OPA scenario is equal to number of relays. Finally, some numerical and simulation results are presented to validate the theoretical analysis and to show the advantages offered by the presented systems. They reveal interesting results that, by increasing number of untrusted relay nodes, the system performance improves. For example, for target ESR 2 bits/s/Hz and ten untrusted relay nodes, the optimised network saves about 5 dB for uplink transmission, in comparison with the system applying the BRS and equal power allocation.
In this study, the authors study the problem of secure transmission in two‐hop amplify‐and‐forward systems with an untrusted relay. To prevent the untrusted relay from intercepting the source message and to achieve positive secrecy rate, the destination‐based cooperative jamming technique is used. In this method, the destination sends an intended jamming signal to the relay. This jamming signal helps protecting the source message from being captured reliably at the untrusted relay, while the destination cancels itself intended jamming signal. The optimal power allocation (OPA) strategy is considered for the proposed system. They observe that the objective function is a quasi‐concave function at high signal‐to‐noise‐ratio regimes. Based on this OPA strategy, in the first step, the outage probability of the system is investigated. It is investigated for three cases. In the two cases, either of the source or the destination node is equipped with large‐scale antennas, and in the third case, both of them are equipped with large‐scale antenna arrays. In all the cases, the closed‐form expressions are derived. In the second step, they investigate the ergodic secrecy rate and present the closed‐form solutions for all the mentioned cases. Finally, simulation results indicate the accuracy of the derived equations.
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.
By considering millimetre wave (mmWave) transmission as an effective solution for the fifth‐generation (5G) wireless communication systems, the authors propose a new optimal power allocation (OPA) scheme to maximise the instantaneous secrecy rate of a cooperative wireless network. The communication network under study is comprised of a multiple‐antennas source, a multiple‐antennas destination, a single antenna untrusted relay and single antenna passive eavesdroppers (Eves). To prevent the untrusted relay and passive Eves from overhearing the source message, a new secure transmission scheme is proposed. Based on this scheme, the destination sends an artificial noise (AN) towards the untrusted relay, and concurrently, the source is forced to dedicate part of its power to transmit AN to keep the information confidential from the Eves. For such a communication network, two cases of non‐colluding Eves (NCE) and colluding Eves (CE) are taken into account. Based on the proposed OPA, a novel closed‐form expression is presented for the ergodic secrecy rate (ESR) performance over mmWave channels. Next, the authors derive the high signal‐to‐noise ratio slope and power offset of the ESR to evaluate the effects of network parameters on the ESR performance. Numerical examples depict that the proposed optimised systems for both NCE and CE present superior ESR compared to other transmission policies.
In this paper, a joint relay selection and power allocation (JRP) scheme is proposed to enhance the physical layer security of a cooperative network, where a multiple antennas source communicates with a single-antenna destination in the presence of untrusted relays and passive eavesdroppers (Eves). The objective is to protect the data confidentially while concurrently relying on the untrusted relays as potential Eves to improve both the security and reliability of the network. To realize this objective, we consider cooperative jamming performed by the destination while the JRP scheme is implemented. With the aim of maximizing the instantaneous secrecy rate, we derive a new closed-form solution for the optimal power allocation and propose a simple relay selection criterion under two scenarios of non-colluding Eves (NCE) and colluding Eves (CE). For the proposed scheme, a new closed-form expression is derived for the ergodic secrecy rate (ESR) and the secrecy outage probability as security metrics, and a new closed-form expression is presented for the average symbol error rate as a reliability measure over Rayleigh fading channels. We further explicitly characterize the high signal-to-noise ratio slope and power offset of the ESR to highlight the impacts of system parameters on the ESR. In addition, we examine the diversity order of the proposed scheme to reveal the achievable secrecy performance advantage. Finally, the secrecy and reliability diversity-multiplexing tradeoff of the optimized network are provided. Numerical results highlight that the ESR performance of the proposed JRP scheme for NCE and CE cases is increased with respect to the number of untrustworthy relays.
Abstract—In this paper, the problem of secure transmission in two-hop amplify-and-forward (AF) systems with an untrusted relay is investigated. To prevent the untrusted relay from intercepting the source message and to achieve positive secrecy rate, the destination-based cooperative jamming (DBCJ) technique is used. In this method the destination sends an intended jamming signal to the relay. This jamming signal helps protecting the source message from being captured reliably at the untrusted relay, while the destination cancels itself intended jamming signal. The optimal power allocation (OPA) technique is considered for the presented system. It is observed that the objective function is a quasiconcave function at high signal-to-noise-ratio (SNR) regimes. Based on this OPA technique, we study the ergodic secrecy rate (ESR) and the secrecy outage probability (SOP) of the system when the source and relay are equipped with a single antenna while the destination is equipped with largescale antenna arrays (LSA). Using the achieved closed-form expressions, one can evaluate the performance of the secure system easily and fast and also, they provide significant insight for system design. Finally, simulation results indicate the accuracy of the derived expressions.