In this paper, we investigate the security of a multi-antenna two-way relay cellular network in the presence of a passive eavesdropper, where a base station and multiple mobile users exchange uplink and downlink information with the assistance of a relay station.We propose a secrecy scheme based on the concepts of the artificial noise scheme for the secure transmission and signal alignment scheme for the suppression of multiuser interference. This paper aims to study transceiver design to minimize the transmit power allocated to the information signal so that the transmit power allocated to the artificial noise signal can be maximized to confuse the eavesdropper, under the constraints of quality of service requirement. We show that transceiver design problems can be converted to a second-order cone programming problem and the optimal solution is obtained efficiently. The performance of the proposed secrecy scheme is evaluated by simulations.
In this paper, we investigate the security of a multi-antenna two-way relay cellular network in the presence of a passive eavesdropper, where a base station and multiple mobile users exchange uplink and downlink information with the assistance of a relay station.We propose a secrecy scheme based on the concepts of the artificial noise scheme for the secure transmission and signal alignment scheme for the suppression of multiuser interference. This paper aims to study transceiver design to minimize the transmit power allocated to the information signal so that the transmit power allocated to the artificial noise signal can be maximized to confuse the eavesdropper, under the constraints of quality of service requirement. We show that transceiver design problems can be converted to a second-order cone programming problem and the optimal solution is obtained efficiently. The performance of the proposed secrecy scheme is evaluated by simulations.
In this paper, we address the security of a two-way relay network in the presence of an eavesdropper, where each node is only equipped with single antenna. We propose two-phase distributed analog network coding, or distributed beamforming and power allocation to enhance the secrecy sum rate of the data exchange. In the first phase, the two terminals broadcast their information data simultaneously to all the relay nodes. In the second phase, three different security schemes are proposed: optimal beamforming, null-space beamforming, and artificial noise beamforming. In the first scheme, the objective is to achieve the maximum secrecy sum rate of the two terminals. Mathematically, the objective function is difficult to optimize. In the second scheme, we maximize the total information exchanged while we eliminate the information leakage completely, subject to the total transmission power constraint. We show that the problem has a unique and global optimum, which can be solved using bisection method. When the instantaneous channel state information of the eavesdropper is not available, we propose an artificial noise beamforming in the third scheme. We minimize the information transmission power so that the artificial noise power is maximized to eliminate information leakage, under the constraints of quality of service (QoS) required by terminals. It is a second-order convex cone programming (SOCP) problem, thus can be efficiently solved using interior point methods. Numerical results are provided and analyzed to show the properties and efficiency of the proposed designs.
In this paper, we investigate the performance of secure cellular multiuser two-way amplify-and-forward relay networks, wherein one Na-antenna base station (BS) exchanges information bidirectionally with K single-antenna users (USs) by the assistance of a single-antenna relay node in the presence of a singleantenna passive eavesdropper. We employ user selection coupled with antenna selection (AS) scheme at the BS so as to maximize the end-to-end signal-to-noise ratios. In the considered system, by employing two possible combining techniques at the eavesdropper, viz., maximum ratio combining (MRC) and selection combining (SC), we derive the novel tight closed-form expressions for the secrecy outage probability (SOP) under Rayleigh fading channels. We present an asymptotic secrecy diversity order analysis of the considered system for the large transmit power, and demonstrate that the eavesdropping reduces the secrecy diversity order from min(Na, K) to 1. Further, we present some useful insights into the impact of eavesdropper and number of antennas and users on the SOP performance. It is shown that the eavesdropper has a severe impact on the SOP performance, regardless of number of antennas and users. The numerical and simulation results corroborate our theoretical findings, and demonstrate the influence of eavesdropper and relay positions on the SOP performance. We show that the SOP performance improves significantly when the eavesdropper is far away from the BS and USs. It is also shown that the SOP performance enhances noticeably if the relay location is chosen optimally, for different eavesdropper positions and/or different values of antennas and users. Moreover, our results also reveal that only coding gain rather than diversity gain is achieved by increasing Naand K, because of the dominance of information leakage by the first time phase. Furthermore, results illustrate that the SOP performance under SC technique employed at the eavesdropper outperforms the MRC-based technique for the broad range of transmit power.
In this paper, we study the physical layer security in a two-way relay system consisting of two transceivers, one eavesdropper, and multiple relays. We study the system in case of the channel state information (CSI) of the eavesdropper is unknown, and hence artificial noise is used to degrade the signal to noise ratio at the eavesdropper. In order to reserve the maximum possible power for artificial noise, we consider the problem of minimizing the total power of the information signal transmitted by the relays, under quality of service constraints at the legitimate transceivers. This problem has been solved using semidefinite programming (SDP) and second order cone programming (SOCP) methods. Here, aiming to significantly decrease the complexity, we propose a novel approach to find the optimal solution using the generalized eigenvalue. We show that in most cases, we can provide a closed-form expression of the optimal solution. In addition, our proposed solution can be used for all quadratically constrained quadratic programs (QCQPs) with positive definite objective function and two constraints. Simulation results demonstrate the effectiveness of our algorithm in terms of optimality and low complexity compared to SDP.
This paper introduces two novel physical-layer security algorithms for interference alignment (IA)-based multipair communication systems with a single half-duplex relay and a single eavesdropper. According to these proposed physical-layer security algorithms, users mix their information signals with jamming signals, and broadcast them at the multiple access phase, while the relay forwards the mixed signals at the broadcast phase. Moreover, the relay and users' precoding and decoding matrices are designed in a way which enables the legitimate receivers to eliminate the jamming signals while the hidden eavesdropper is unable to eliminate these jamming streams. In this context, the proposed algorithms are designed to transmit the information streams with minimum power, preserving the user received signal to noise ratio above a pre-determined threshold and utilizing the remaining power for the jamming signals. Therefore, the user and relay power budgets allocation is formulated as a joint optimization problem that can be solved using an iterative optimization algorithm and semi-definite programming. In such fashion, four transmission models are proposed to manage the artificial noise transmission among the different users to achieve a tradeoff between the users sum-rate and secrecy rate. Extensive simulation results are provided to show the efficiency of the proposed algorithms and the transmission models in achieving the transmission security for IA-based multiuser relaying networks.
This paper studies secure wireless transmission from a multi-antenna transmitter to a single-antenna intended receiver overheard by multiple eavesdroppers with considering the imperfect channel state information (CSI) of wiretap channel.To enhance security of communication link, the artificial noise (AN) is generated at transmitter.We first design the robust joint optimal beamforming of secret signal and AN to minimize transmit power with constraints of security quality of service (QoS), i.e., minimum allowable signal-to-interference-and-noise ratio (SINR) at receiver and maximum tolerable SINR at eavesdroppers.The formulated design problem is shown to be nonconvex and we transfer it into linear matrix inequalities (LMIs).The semidefinite relaxation (SDR) technique is used and the approximated method is proved to solve the original problem exactly.To verify the robustness and tightness of proposed beamforming, we also provide a method to calculate the worst-case SINR at eavesdroppers for a designed transmit scheme using semidefinite programming (SDP).Additionally, the secrecy rate maximization is explored for fixed total transmit power.To tackle the nonconvexity of original formulation, we develop an iterative approach employing sequential parametric convex approximation (SPCA).The simulation results illustrate that the proposed robust transmit schemes can effectively improve the transmit performance.
We consider an amplify-and-forward (AF) relay network with multiple source-destination pairs in the presence of an eavesdropper. This paper studies the robust artificial noise (AN) assisted joint transceiver optimization for secure communication with imperfect channel state information (CSI) of legitimate users and no CSI regarding the eavesdropper. The goal is to design the linear precoding matrix of the relay and the linear equalizer of each destination, such that the transmit power for the information-bearing signals and forwarded background noises at the relay can be minimized subject to the quality of service (QoS) constraints at the destinations. The remainder of the constrained total power is used to generate the AN for jamming the eavesdropper. Although such a power minimization problem is nonconvex, we recast it into two semidefinite programming (SDP) subproblems which can be solved using interior-point methods. Then this problem can be solved with the alternating iterative optimization algorithm. Simulations demonstrate that the proposed algorithm can significantly reduce the sensitivity to imperfect CSI, while degrading the eavesdropper's capability of intercepting.