We consider single-user OFDM wiretap channel with an external cooperative jammer (CJ), where the CJ helps the destination to interfere the eavesdropper. The achievable secrecy rate is derived. The source power and CJ power are optimized over all sub-carriers to maximize the sum secrecy rate under a total system power constraint. The simulation results indicate that the secrecy rate with optimal resource allocation is higher than that of the network without a CJ. It indicates that the network with an external CJ using optimal resource allocation improves the security performance greatly.
We consider single-user OFDM wiretap channel with an external cooperative jammer (CJ), where the CJ helps the destination to interfere the eavesdropper. The achievable secrecy rate is derived. The source power and CJ power are optimized over all sub-carriers to maximize the sum secrecy rate under a total system power constraint. The simulation results indicate that the secrecy rate with optimal resource allocation is higher than that of the network without a CJ. It indicates that the network with an external CJ using optimal resource allocation improves the security performance greatly.
This paper studies the secrecy communication in an orthogonal frequency division multiplexing system, where a source sends confidential information to a destination in the presence of a potential eavesdropper. We employ wireless powered cooperative jamming to improve the secrecy rate of this system with the assistance of a cooperative jammer, which works in the harvest-then-jam protocol over two time slots. In the first slot, the source sends dedicated energy signals to power the jammer; in the second slot, the jammer uses the harvested energy to jam the eavesdropper, in order to protect the simultaneous secrecy communication from the source to the destination. In particular, we consider two types of receivers at the destination, namely Type-I and Type-II receivers, which do not have and have the capability of canceling the (a priori known) jamming signals, respectively. For both types of receivers, we maximize the secrecy rate at the destination by jointly optimizing the transmit power allocation at the source and the jammer over sub-carriers, as well as the time allocation between the two time slots. First, we present the globally optimal solution to this problem via the Lagrange dual method, which, however, is of high implementation complexity. Next, to balance the tradeoff between the algorithm complexity and performance, we propose alternative low-complexity solutions based on the minorization maximization and heuristic successive optimization, respectively. Simulation results show that the proposed approaches significantly improve the secrecy rate, as compared to benchmark schemes without joint power and time allocation.
This paper investigates optimal power allocation strategies over a bank of idle independent parallel Gaussian wiretap channels where a cognitive-based transmitter and a cognitive-based receiver communicate in the presence of an eavesdropper and a friendly jammer. We initially focus on the scenario where the cognitive transceiver's confidential message is transmitted without the assistance of a cooperative jammer (CJ) and characterize the secrecy rate maximization power allocation strategy, which indicates that only part of the sensing idle subchannels are utilized. This is a case of inefficiency in spectrum usage for cognitive radio network whose resource comes from spectrum sensing. Thus, we then extend our scenario by introducing a CJ and investigate whether we can further improve the system secrecy rate as that in non-cognitive network. In which, we focus on the joint transmitter and jammer power control and propose a suboptimal algorithm to demonstrate the benefits of introducing a CJ in our scenario.
Summary This paper considers an orthogonal frequency division multiplexing (OFDM) based cooperative network, where a source node communicates with a destination node with the help of multiple intermediate nodes, in the presence of an eavesdropper. Each intermediate node is assumed to be able to act as a relay or a jammer to improve the physical layer security. The problem of joint subcarrier allocation, power allocation, and mode selection to maximize the sum secrecy rate is investigated. We first reformulate the problem of subcarrier allocation and intermediate node mode selection as a three‐sided matching game and propose an algorithm that achieves a stable matching. Then, the sum secrecy rate is further improved by proposing a heuristic algorithm to switch the modes of the intermediate nodes. Finally, an iterative power allocation algorithm is proposed. It is verified by simulation results that the proposed algorithm outperforms various benchmark algorithms such as the equal subcarrier allocation algorithm, the pure relay selection algorithm, and the random relay selection algorithm, especially when the transmit power limit is high and the number of intermediate nodes is large.
This paper studies the secrecy rate maximization problem of a secure wireless communication system in the presence of multiple eavesdroppers. The security of the communication link is enhanced through cooperative jamming with the help of multiple jammers. First, a feasibility condition is derived to achieve a positive secrecy rate at the destination. Then, we solve the original secrecy rate maximization problem, which is not convex in terms of power allocation at the jammers. To circumvent this nonconvexity, the achievable secrecy rate is approximated for a given power allocation at the jammers, and the approximated problem is formulated into a geometric programming one. Based on this approximation, an iterative algorithm has been developed to obtain the optimal power allocation at the jammers. Next, we provide a bisection approach, based on 1-D search, to validate the optimality of the proposed algorithm. In addition, by assuming Rayleigh fading, the secrecy outage probability (SOP) of the proposed cooperative jamming scheme is analyzed. More specifically, a single-integral form expression for the SOP is derived for the most general case, as well as a closed-form expression for the special case of two cooperative jammers and one eavesdropper. Simulation results have been provided to validate the convergence and the optimality of the proposed algorithm, as well as the theoretical derivations of the presented SOP analysis.
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.
In this paper, we consider the problem of power allocation of OFDM user in the presence of an active attacker. The malicious user has the ability of either eavesdropping of ongoing connection or jamming it. However, it can not function as both the eavesdropper and jammer at the same time. The attacker's policy is to choose between eavesdropping and jamming such that the ultimate secrecy rate is minimized. Hence, the legitimate user considers the worst case at which the ultimate secrecy rate is assumed to be the minimum between the achievable rate of each case. Under the total transmit power constraint, the user distribute the transmit power over subcarrier such that the total secrecy rate is maximized. By simulation, we evaluate the efficiency of the proposed scheme.