In this paper, a near Optimum Power Allocation (OPA) for a cooperative jamming relay network is proposed, by using physical layer security to protect the user's messages from relay's interception. The network uses Amplify and Forward (AF) relay to enlarge the coverage area, however the relay is untrusted. By defining secure Energy Efficiency (EE) as the ratio of the instantaneous secrecy rate to the total power consumption to measure the performance of the network. To simplify such optimization problem, an approximated OPA on the basis of Taylor expansion is derived. The numerical results show that the approximated OPA error does not exceed 1% even in the worst case, which verifies the correctness and lower complexity of the proposed algorithm.
In this paper, a near Optimum Power Allocation (OPA) for a cooperative jamming relay network is proposed, by using physical layer security to protect the user's messages from relay's interception. The network uses Amplify and Forward (AF) relay to enlarge the coverage area, however the relay is untrusted. By defining secure Energy Efficiency (EE) as the ratio of the instantaneous secrecy rate to the total power consumption to measure the performance of the network. To simplify such optimization problem, an approximated OPA on the basis of Taylor expansion is derived. The numerical results show that the approximated OPA error does not exceed 1% even in the worst case, which verifies the correctness and lower complexity of the proposed algorithm.
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.
Abstract A half‐duplex relaying network provides 2 opportunities for passive eavesdroppers (Eves) and 1 opportunity for untrusted relays to intercept the information. In this paper, we aim to enhance the physical layer security of a cooperative network where a single‐antenna source intends to communicate with a single‐antenna destination in the presence of a group of untrusted relays and a passive eavesdropper. 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 design a joint cooperative beamforming and cooperative jamming strategy. With the aim of maximizing the instantaneous secrecy rate, an optimal power allocation (OPA) scheme is proposed where the transmission powers of both jammer and source are optimized simultaneously under the total power budget constraint. To further improve the secrecy rate, a jammer selection strategy is also proposed where cooperative jamming is performed by the destination or one of the idle relays. For the proposed scheme, a closed‐form expression of beamformer vector is derived by solving a generalized eigenvalue problem. Finally, for the OPA problem, it is possible to be neither convex nor concave. In this regard, all possible cases are investigated to determine the OPA factor accurately. Numerical results illustrate that the proposed joint OPA–cooperative beamforming scheme, together with the most appropriate jammer selection strategy, significantly increases the secrecy rate.
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.
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.
The inherent broadcast characteristics of wireless medium make wireless data transmission difficult to be shielded from unintended recipients. As such, secure communication over wireless channels becomes a critical issue in the design of wireless networks. In this study, the authors study cooperative jamming and power optimisation in untrusted relay networks to improve physical layer security. By exploiting the direct link, a source‐based jamming (SBJ) scheme is proposed to hinder the untrusted relay from intercepting the confidential message. Considering the total power budget, a power allocation strategy is also proposed to optimally determine the power of source and untrusted relay as well as the power of information and jamming signals. Furthermore, to evaluate the secrecy performance of the proposed SBJ scheme with the power allocation strategy, tight lower bound of ergodic secrecy capacity and asymptotic secrecy outage probability are derived in closed form. Simulation verifies the advantages of the proposed SBJ scheme and the power allocation strategy.
In this paper, we investigate the cooperative jamming (CJ) strategy in a three-node cooperative system, where the relay, which forwards the received signals in a amplify-and-forward (AF) protocol, is untrusted, furthermore, there is an external malicious eavesdropper. A two-phase CJ scheme, which merely using internal nodes of the cooperative system without the help of external nodes, is proposed to enhance the secrecy information transmission against the malicious eavesdropper and the untrusted relay. And then, we provide the optimal power allocation with maximum instantaneous secrecy rate (OPA-MISR) and the suboptimal power allocation with max-min instantaneous secrecy rate (SPA-MMISR). Finally, the simulation results show that the cooperative jamming proposed is effective to improve the achievable instantaneous secrecy rate and to resist both internal untrusted relay and external malicious eavesdropper.