This paper considers the use of a friendly full-duplex (FD) relay to increase the secrecy rate over a fading channel between the legitimate source and destination in the presence of a naive or informed eavesdropper. Naive eavesdropper can only decode the received signals either from the source or from the relay, while informed eavesdropper can overhear signals transmitted from both the source and relay. Accordingly, we compare the achievable secrecy rates of FD relay with traditional half-duplex (HD) relay in terms of the channel state information (CSI) between nodes, eavesdropper types, and the self-interference (SI) in FD-Relay. We consider the non-convex power allocation problems for the developed FD-relay to maximize the secrecy rate under the power constraints and develop an efficient iterative algorithm based on the difference-of-two-concave-functions (DC) programming. The analytical and simulation results confirm that FD relay offers significant improvements in the secrecy rate over the HD-Relay.
This paper considers the use of a friendly full-duplex (FD) relay to increase the secrecy rate over a fading channel between the legitimate source and destination in the presence of a naive or informed eavesdropper. Naive eavesdropper can only decode the received signals either from the source or from the relay, while informed eavesdropper can overhear signals transmitted from both the source and relay. Accordingly, we compare the achievable secrecy rates of FD relay with traditional half-duplex (HD) relay in terms of the channel state information (CSI) between nodes, eavesdropper types, and the self-interference (SI) in FD-Relay. We consider the non-convex power allocation problems for the developed FD-relay to maximize the secrecy rate under the power constraints and develop an efficient iterative algorithm based on the difference-of-two-concave-functions (DC) programming. The analytical and simulation results confirm that FD relay offers significant improvements in the secrecy rate over the HD-Relay.
This paper proposes a jointly cooperative relay and jamming protocol based on full-duplex (FD) capable relay to increase the source-destination secrecy rate in the presence of different types of eavesdroppers. In this so called FD-Relay with jamming (FDJ) protocol, the FD-Relay, first, simultaneously receives data and sends jamming to the eavesdropper, and, then, forwards the data, while the source jams the eavesdropper. Achievable secrecy rates of the proposed FDJ in the presence of different eavesdropper types and self-interference (SI) are derived and compared with those of the traditional half-duplex (HD) relay. The adaptive power allocation for secrecy rate maximization in a multi-carrier scenario for both proposed FDJ and HD-Relay is formulated as a non-convex optimization problem and corresponding iterative solution algorithm is developed using the difference-of-two-concave-functions (DC) programming technique. The simulation results confirm that FDJ offers significant improvements in the secrecy rate over the HD-Relay.
In this paper, we examine the use of a friendly full-duplex (FD) relay to increase the secrecy rate over a fading channel between the legitimate source and the destination in the presence of residual self-interference (SI) and eavesdropper. In particular, we consider two different protocols based on the FD capability of relay: 1) FD transmission (FDT), in which the FD-Relay receives and sends data concurrently; 2) FD-Relay with jamming (FDJ), where first, the FD-Relay simultaneously receives data and sends jamming to the eavesdropper; then, it forwards the data, while the source jams the eavesdropper. We first develop the secrecy rate expressions for half-duplex transmission (HDT), half-duplex with jamming (HDJ), FDT, and FDJ relaying protocols, and then use them to derive their performance properties in terms of the channel gains between nodes, eavesdropper types, and more importantly, the SI level in FD-Relay. We further investigate the non-convex power allocation problems for the developed FDT and FDJ to maximize the secrecy rate under the power constraints. In particular, we develop an efficient iterative algorithm based on the difference-of-two-concave-functions programming. Analytical and simulation results show the strong influence of SI level on the achieved secrecy rate of the FDT and the FDJ. For sufficiently low SI, FDT achieves a much higher secrecy rate than FDJ, HDJ, and HDT. However, for higher SI, FDJ becomes more effective in enhancing the achieved secrecy rate. The results also indicate that adaptive power allocation can significantly improve the performance and confirm that the proposed FDT and FDJ outperform the HDT and the HDJ.
This paper investigates secrecy efficiency (SE) optimization in a friendly full-duplex (FD) decode- and-forward (DF) relay network with a passive eavesdropper. Targeting on SE maximization, the power allocation is optimized subject to the total power and minimum secrecy rate constraints adapting to the assumption of unknown eavesdropper's channel state information (CSI). By exploiting the properties of fractional programming (FP) and Difference of Convex functions (DC) programming, the resulting nonconvex optimization problem can be relaxed into a more tractable equivalent problem. Simulation results demonstrate that our proposed scheme can reach a better trade-off between security performance and energy consumption.
This letter studies secure communications in a full-duplex relay (FDR) network when an eavesdropper overhears communications between legitimate parties. In a FDR network, both the amplify-and-forward relay and the destination operate in full-duplex for the purpose of achieving a higher secrecy rate and/or improving security. In particular, the destination is capable of receiving the relayed signal and simultaneously emitting a cooperative jamming signal. This work is motivated by an intriguing question: how much residual self-interference (SI) in a FDR network is allowed to achieve a superiority of secrecy performance over conventional half-duplex relay (HDR) networks? To answer the question, the secrecy outage probability (SOP) of the FDR network is derived as a function of residual SI. The analytic results enable us to compare the SOPs of existing HDR networks and the FDR network at various levels of residual SI. In addition, this work allows one to opportunistically select either FD or HD, which leads to a significant performance improvement.
This paper studies a wire-tap channel in which a source node wants to communicate securely to a destination node in the presence of an eavesdropper and under the aid of an amplify-and-forward (AF) relay operating in full-duplex (FD) mode. The residual self-interference due to FD transmission is explicitly taken into account. The secrecy capacity and the respective optimal power allocation schemes for this system are examined under both individual and joint power constraints. At first, the related optimization problems are shown to be quasi-concave. As such, the globally optimal solution exists and is unique. Due to the non-linearity of the derivative, we apply a simple bisection method for root finding and obtain a simple expression for the optimal power allocation scheme. To further provide some insight on the solutions, we apply the method of dominant balance to analyze the capacity and power allocations in different high power regions. It is then demonstrated that full relay power is only needed when the power at the relay is sufficiently small compared to the power at the source. Comparisons with half-duplex (HD) relaying also revealed that FD can achieve a significantly higher secrecy capacity. Finally, numerical results are presented to confirm the optimality of the solutions.
This paper proposes optimum beamforming for a system consisting of a source, a full-duplex (FD) relay, an intended destination, and an eavesdropper. The source and destination are single-antenna nodes, whereas the FD relay is a multi-antenna node. Our objective is to find the optimum receive and transmit beamformers at the relay so that the secrecy rate is maximized. The joint optimization problem is equivalently expressed in terms of the transmit beamformer. The resulting optimization is non-convex. However, we equivalently reformulate it to a suitable form so that the optimum solution is obtained by solving semi-definite relaxation problem, in conjunction with a line search confined to a specific region. Computer simulations demonstrate significant increase in secrecy rate compared to the conventional secure half-duplex relay communications.