The wireless transmission environment opens up opportunities for an eavesdropper to intercept a secret message from the source to the legitimate destination, particularly in the case when the eavesdropper is close to the source. Cooperative jamming, where nodes that are inactive serve as noise-generating nodes to disrupt an eavesdropper, has recently been considered in wireless communication networks to improve secrecy in such scenarios. Here we consider optimal power allocation to these jamming nodes (termed “chatterers”) in the case of an eavesdropper of known location. The optimal power allocation to the chatterer nodes is achieved via water-filling that, as one would expect, favors nodes that are close to the eavesdropper but will not impact the message to the destination significantly, either because the chatterer is located at a large distance from the destination or because the chatterer's signal is significantly faded at the destination. Numerical results compare the performance of the system employing the optimal power allocation to the performance of lower overhead schemes that employ only a single jamming node.
The wireless transmission environment opens up opportunities for an eavesdropper to intercept a secret message from the source to the legitimate destination, particularly in the case when the eavesdropper is close to the source. Cooperative jamming, where nodes that are inactive serve as noise-generating nodes to disrupt an eavesdropper, has recently been considered in wireless communication networks to improve secrecy in such scenarios. Here we consider optimal power allocation to these jamming nodes (termed “chatterers”) in the case of an eavesdropper of known location. The optimal power allocation to the chatterer nodes is achieved via water-filling that, as one would expect, favors nodes that are close to the eavesdropper but will not impact the message to the destination significantly, either because the chatterer is located at a large distance from the destination or because the chatterer's signal is significantly faded at the destination. Numerical results compare the performance of the system employing the optimal power allocation to the performance of lower overhead schemes that employ only a single jamming node.
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.
Relying on physical layer security is an attractive alternative of utilizing cryptographic algorithms at upper layers of protocol stack for secure communications. In this paper, we consider a two-hop wireless relay network in the presence of an eavesdropper. Our scenario of interest spans over a four-node network model including a source, a destination, a trusted relay, and an untrusted eavesdropper in which the relay forwards the source message in a decode-and-forward (DF) fashion. The source and relay are allowed to use some of their available power to transmit jamming signals in order to create interference at the eavesdropper. The relay and destination are assumed to have the knowledge of the jamming signals. An important question is how to allocate the transmission power of the message signal and that of the jamming signal. First, we propose an optimal power allocation solution in which the knowledge of global channel state information (CSI) is required. To facilitate practical system design, two simple yet sub-optimal power allocation solutions are proposed which do not rely on eavesdropper's channels. For the purpose of performance comparisons, power allocation problems for two benchmark schemes without jamming are also analyzed.
In this paper, we investigate secure communications in two-hop wireless relaying networks with one eavesdropper. To prevent the eavesdropper from intercepting the source message, the destination sends an intended jamming noise to the relay, which is referred to as cooperative jamming. This jamming noise helps protecting the source message from being captured reliably at the eavesdropper, while the destination cancels its self-intended noise. According to the channel information available at the destination, we derive three jamming power allocation strategies to minimize the outage probability of the secrecy rate. In addition, we derive analytic results quantifying the jamming power consumption of the proposed allocation methods.
Physical (PHY) layer security approaches for wireless communications can prevent eavesdropping without upper layer data encryption. However, they are hampered by wireless channel conditions: absent feedback, they are typically feasible only when the source-destination channel is better than the source-eavesdropper channel. Node cooperation is a means to overcome this challenge and improve the performance of secure wireless communications. This paper addresses secure communications of one source-destination pair with the help of multiple cooperating relays in the presence of one or more eavesdroppers. Three cooperative schemes are considered: decode-and-forward (DF), amplify-and-forward (AF), and cooperative jamming (CJ). For these schemes, the relays transmit a weighted version of a reencoded noise-free message signal (for DF), a received noisy source signal (for AF), or a common jamming signal (for CJ). Novel system designs are proposed, consisting of the determination of relay weights and the allocation of transmit power, that maximize the achievable secrecy rate subject to a transmit power constraint, or, minimize the transmit power subject to a secrecy rate constraint. For DF in the presence of one eavesdropper, closed-form optimal solutions are derived for the relay weights. For other problems, since the optimal relay weights are difficult to obtain, several criteria are considered leading to suboptimal but simple solutions, i.e., the complete nulling of the message signals at all eavesdroppers (for DF and AF), or the complete nulling of jamming signal at the destination (for CJ). Based on the designed relay weights, for DF in the presence of multiple eavesdroppers, and for CJ in the presence of one eavesdropper, the optimal power allocation is obtained in closed-form; in all other cases the optimal power allocation is obtained via iterative algorithms. Numerical evaluation of the obtained secrecy rate and transmit power results show that the proposed design can significantly improve the performance of secure wireless communications.
In this paper, we propose efficient power allocation techniques using both convex optimization (using Lagrange multiplier method) and a soft evolutionary approach (using Differential Evolution (DE) algorithm) to optimize both the relay and jammer powers in addition to an increase in the system performance in terms of secrecy rate. Here, we consider a cooperative wireless network with control jamming comprising of a source-destination pair with a set of relay nodes in the presence of single and multiple eavesdroppers. Optimal relay node is selected based on the SNR received at each relay, which transmits the data to the destination using decode and forward strategy. Amongst the remaining nodes, selection of jammer is done based on the SNR value of the relay to eavesdropper link. The proposed power allocation schemes are compared with equal power allocation policy for using the Monte-Carlo simulation study and these schemes are found to be superior in terms of average secrecy rate.
This paper investigates cooperative security in wireless networks, where a source (Alice) intends to transmit a confidential message to a legitimate destination (Bob), with the help of a cooperative jammer (Charlie), coexisting with multiple passive eavesdroppers (Eves). In particular, by assuming knowledge of Bob's perfect channel state information (CSI) but only Eves’ statistical CSIs, secrecy beamforming with artificial noise (AN) is utilized for secure transmission, and cooperative jamming (CJ) is explored to further enhance secrecy. We first derive an accurate closed-form expression for the secrecy outage probability (SOP), and establish the condition under which positive secrecy rate is achievable. Then, we provide a secure transmit design for maximizing the SOP constrained secrecy rate. Moreover, based on a strict mathematical analysis, we characterize the impact of the main channel quality and the number of Eves on transmit design and secrecy performance. Specifically, optimal power allocation ratio between the information-bearing signal and the AN signal increases as the main channel quality improves, and decreases with the number of Eves. Numerical results confirm that our design achieves performance improvement in terms of both secrecy rate and secure energy efficiency, as compared to the approach without CJ.