In this paper, we propose two cooperative jamming protocols in two-hop amplify-and-forward (AF) wiretap channels: 1) jamming signal at the source (JSS) and 2) jamming signal at the relay (JSR). We apply optimal power allocation (OPA) between the useful signal and the jamming signal to maximize the secrecy rate for each of the protocols. A fundamental question to address is “Which cooperative jamming protocol is superior under OPA?” To this end, we evaluate the maximum secrecy rate of JSS and JSR for the general scenario of independent but not necessarily identically distributed fading with distinct average signal-to-noise ratios (SNRs) in the first hop, the second hop, and the wiretap link. We demonstrate that the strong first and second hops equally benefit the secrecy rates of JSS and JSR, when the wiretap link is weak. When the wiretap link is strong, the secrecy rate of JSR is superior to JSS.
In this paper, we propose two cooperative jamming protocols in two-hop amplify-and-forward (AF) wiretap channels: 1) jamming signal at the source (JSS) and 2) jamming signal at the relay (JSR). We apply optimal power allocation (OPA) between the useful signal and the jamming signal to maximize the secrecy rate for each of the protocols. A fundamental question to address is “Which cooperative jamming protocol is superior under OPA?” To this end, we evaluate the maximum secrecy rate of JSS and JSR for the general scenario of independent but not necessarily identically distributed fading with distinct average signal-to-noise ratios (SNRs) in the first hop, the second hop, and the wiretap link. We demonstrate that the strong first and second hops equally benefit the secrecy rates of JSS and JSR, when the wiretap link is weak. When the wiretap link is strong, the secrecy rate of JSR is superior to JSS.
In this paper, we investigate secrecy communications in two-hop wireless relaying networks which consist of one source, one amplify-and-forward (AF) relay, one legitimate destination, and one eavesdropper. To prevent the eavesdropper from intercepting the source message, we make the destination send the intended noise to the AF relay during the first phase. This is referred to as cooperative jamming. According to the channel information at the destination, we address two types of jamming power allocation; (i) rate-optimal power allocation and (ii) outage-optimal power allocation. More specifically, without the instantaneous channel knowledge for the eavesdropper side, the outage probability of the secrecy rate is minimized with respect to the intended noise power level. We show that the outage-optimal allocation gives almost the same outage probability as the rateoptimal one. In addition, the jamming power consumption can be significantly reduced compared to the fixed and rate-optimal power allocation methods.
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.
A two-hop relay-eavesdropper channel model with one transmitter,one relay,one receiver and one eavesdropper is considered,where the nodes harvest energy and the save-then-transmit protocol is employed.That is,the nodes harvest energy first,which is then used to transmit the data.The relay is operated as an amplify-and-forward relay,and the destination sends an intended jamming noise to protect information,which is referred as cooperative jamming.First,the condition that ensures the promotion of secrecy capacity is derived.Second,an optimization algorithm to maximize secrecy rate Rsis given,which is based on the optimization of the energy saving time ratioρand the jamming power allocation scaling factorα.Simulation results show that the algorithm has a high convergence speed,and can effectively improve secrecy rate.
In this paper, we consider a dual-hop amplify-and-forward (AF) multiple-input-multiple-output (MIMO) relay network, where the source, relay, and destination are each equipped with multiple antennas. The relay is untrusted if it is willing to forward the signal to the destination and, at the same time, acts as a potential eavesdropper to interpret the message from the source. Since there exists no direct link between the source and the destination, a positive secrecy rate cannot be obtained. Addressing this issue, we propose a joint destination-aided cooperative jamming and precoding at both the source and the relay scheme: joint source, relay, and destination precoding (JP). We target at maximizing the secrecy rate by jointly designing the source, relay, and destination precoding matrices and propose an alternating iterative optimization algorithm to tackle the nonconvex problem. Then, a comprehensive study on the asymptotic performance is conducted in a high signal-to-noise ratio (SNR) regime. In particular, we present simple closed-form expressions for the two key performance parameters in the asymptotic secrecy rate, i.e., the high-SNR slope and the high-SNR power offset. Finally, numerical results are conducted to demonstrate the validity of the proposed secure scheme and its performance analysis.
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.