The existing physical layer encryption algorithm, which is based on artificial noise, could affect legitimate receivers negatively when the number of users is no less than sending antennas in the multiuser MIMO system. In order to improve the multiuser MIMO system security under this scenario, the paper proposed a multiuser MIMO system physical layer encryption algorithm based on joint channel state matrix. Firstly, multiple users are processed together, thus a multiuser joint channel state matrix is established. After Singular Value Decomposition of the joint channel state matrix, the minimum singular value is obtained and can be utilized for pre-coding, so as to eliminate the interference of artificial noise to legitimate receivers. Further, the paper also presented an approach to optimize the power allocation. The simulation results show that the proposed algorithm can effectively increase the secrecy capacity by 0.1bit/s/HZ averagely, and improve the multiuser MIMO system security.
The existing physical layer encryption algorithm, which is based on artificial noise, could affect legitimate receivers negatively when the number of users is no less than sending antennas in the multiuser MIMO system. In order to improve the multiuser MIMO system security under this scenario, the paper proposed a multiuser MIMO system physical layer encryption algorithm based on joint channel state matrix. Firstly, multiple users are processed together, thus a multiuser joint channel state matrix is established. After Singular Value Decomposition of the joint channel state matrix, the minimum singular value is obtained and can be utilized for pre-coding, so as to eliminate the interference of artificial noise to legitimate receivers. Further, the paper also presented an approach to optimize the power allocation. The simulation results show that the proposed algorithm can effectively increase the secrecy capacity by 0.1bit/s/HZ averagely, and improve the multiuser MIMO system security.
The existing physical layer security algorithm, which is based on artificial noise, could affect legitimate receivers negatively when the number of users is no less than sending antennas in multi-user MIMO system.In order to improve security of multi-user MIMO system under this scenario, we propose a new multi-user MIMO system physical layer security algorithm based on joint channel state matrix.Firstly, multiple users are processed together, thus a multi-user joint channel state matrix is established.After achieving Singular Value Decomposition (SVD) of the joint channel state matrix, the minimum singular value is obtained, which can be utilized for precoding to eliminate the interference of artificial noise to legitimate receivers.Further, we also present an approach to optimize the power allocation.Simulation results show that the proposed algorithm can increase secrecy capacity by 0.1 bit/s/HZ averagely.
The existing physical layer security algorithm could guarantee secure communication to a certain extent. However, eavesdropper can get more information from legitimate receivers whose channel condition is worse than other users. In order to improve the system's security, a novel physical layer security algorithm based on cooperative jamming for multiuser MIMO system is proposed in this paper. Firstly, a multi-user MIMO system of security is established, combining transmit beamforming and artificial noise. Then, the status of each user's characteristics is described respectively. And users are divided into a secure communications group and interference group for scheduling according to the characteristics of the user's state. Further, interference group assists the base station interference eavesdropper by adjusting the beamforming weights. Simulation results show that the proposed algorithm can increase the secrecy capacity by 2.4bit/s/HZ averagely, which can improve security for multi-user MIMO system.
At present, there has been a large amount of research on secrecy rate optimization. However, the reliability analysis of secure transmission is equally important although relatively less attention has been dedicated to. Therefore, this paper proposes a secure transmission method with artificial noise for the physical layer security issues in the transmission process of Multiple Input Multiple Output (MIMO) wireless communication systems. Firstly, we establish an artificial noise assisted MIMO systems model. Then, the channel state information (CSI) matrix is subjected to singular value decomposition to obtain the reasonable precoding and artificial noise matrices. Finally, the impact of artificial noise on the bit error rate performance of potential eavesdropper is analyzed, and based on the analysis, the problem of maximizing the system secrecy rate is established. The concave-convex procedure (CCCP) method is used to obtain the optimal power allocation, which significantly improves the security of MIMO systems. The simulation results show that using the null space of CSI matrix and artificial noise for signal encryption effectively improves the bit error rate of potential eavesdropping nodes. In addition, the secrecy rate obtained by the CCCP algorithm is consistent with the performance obtained by the particle swarm optimization algorithm, which verifies the effectiveness of the proposed algorithm.
In this thesis, we study the physical layer security in downlink multi-user wireless networks. Traditionally, security has been addressed by cryptography at the higher layers of the communication stack. Security at the physical layer has been a major research topic in recent years. We study two different precoder designs alongside artificial noise (AN) to mitigate multi-user interference and deteriorate reception at the eavesdropper (Eve). We study the large scale analysis to calculate the secrecy sum-rate for these two cases and analyze the effect of AN on the system. First, we consider the worst case scenario, when eavesdropper's (Eve's) rate is not deteriorated by the interference caused by the legitimate users. Later, we investigate how interference from legitimate users would affect the large scale security sum rate. At the end, we assume more practical situation where the channel state information at the transmitter is not perfect due to feedback limitation and estimation error. We first study block diagonalization (BD) precoding. We derive the asymptotic secrecy sum-rate of BD for physical layer security in downlink multi-user wireless networks using artificial noise (AN). We first derive the secrecy sum-rate assuming that the channel of the eavesdropper is not known at the transmitter and derive the asymptotic secrecy sum-rate. Then we derive the optimum power allocation for asymptotic secrecy sum-rate. We design the system based on large scale analysis for different special cases. Simulation results show that the proposed precoders outperform channel inversion (CI) and regularized channel inversion (RCI) schemes at all SNRs. We also show that as the number of receive antennas of each user increases, the sum-rate gap between the proposed scheme and existing methods increases. We, then, study two methods of regularized block diagonalization (RBD) precoding using artificial noise (AN) for physical layer security in downlink multi-user MIMO wireless networks. We compare the complexity analysis of these two methods in terms of floating point operations per second (FLOPS). We derive the secrecy and asymptotic secrecy sum-rates for these schemes. We also derive closed form expressions for the asymptotic optimal power allocation to the AN signal and legitimate users. Simulations show RBD precoding outperform regularized channel inversion (RCI) in terms of secrecy sum-rate with a margin of 0.5 bits/s/Hz. Also, simulation results show our closed-form asymptotic secrecy sum-rates matches closely with the simulations for perfect and imperfect CSIT. We also study the effect of interference on BD precoding scheme. In the first two studies the worst case scenarios was considered and the effect of interference was not considered at the eavesdropper. We first derive the closed-form secrecy and asymptotic secrecy sum-rates for this scheme. Then, we derive the optimum power allocation. Using the derived optimum power allocation, we determine the conditions under which adding AN helps. We also investigate the optimum number of users, number of antennas at the eavesdropper, and the number of transmit antennas to fully study the conditions where using AN improves performance. We show that as the number of users increases or the number of receive antennas at the eavesdropper decreases, improved performance is achieved by allocating a smaller fraction of the total power to transmit the AN. The closed form expressions for the secrecy sum rate (SSR) and optimum power allocation closely match our simulation results. In Chapter 5, we study the effect of imperfect channel state information at the transmitter (CSIT) for each case studied in earlier chapters. We first study the effect of imperfect CSIT for BD precoding in both scenarios when interference does and does not exist at eavesdropper. We show that the imperfect CSI play the same role as interference for the desired users. Then, we study the effect of imperfect CSIT for RBD precoding when interference does not exist at eavesdropper. We show as channel estimation error increases, the secrecy sum-rate decreases. This is due to the fact that channel estimation error just affects the desired users' rate and has no effect on eavesdropper's performance. Finally, in the last chapter, we conclude our thesis and provide some road map for future--Author's abstract
In this paper, physical layer security techniques are studied for the downlink of multiuser multi-input multi-output (MIMO) networks. We aim at minimizing the total transmit power such that individual secrecy rate is satisfied for each user. An iterative joint power control and transceiver beamforming algorithm is developed to achieve this goal. The proposed algorithm is realized by solving the two subproblems. We first study the power control problem with the fixed receiver beamforming. In the following, we obtain the optimal receiver beamforming by minimizing the noise-plus-interference power at the receiver under the condition of unity gain for the signal. The performance is evaluated by considering the impact of individual secrecy rate requirement and number of the transmit antenna. Furthermore, we evaluate the impact of the eavesdropper's channel state information (CSI). The numerical results demonstrate the effectiveness of the joint transceiver beamforming scheme.
In this paper, we focus on antieavesdropping design in a multicell multiuser interference channel coexisting with a multiantenna eavesdropper, in which multiuser interference arises as a nonneglectable factor in securing communication. Supposing the eavesdropper is equipped with an arbitrary number of antennas, we jointly exploit the role of inherent multiuser interference and artificial noise (AN) to enhance security, and propose a noniterative secure transceiver design under a multiple input multiple output (MIMO) framework. The quantity relationship of system parameters is then analyzed to ensure feasibility. And the achievable secrecy rate is then derived without any knowledge of the eavesdropper. Finally, to balance the power allocated to AN and secrecy data, a power allocation strategy aiming at maximizing the achievable secrecy rate is designed, while guaranteeing legitimate users the required quality of service. With the adopted design, both the multiuser interference and AN are leveraged to facilitate communication security such that the proposed secure transceiver design can adapt to changes in eavesdropping antennas. Extensive numerical results have verified our analysis and demonstrated that the proposed power allocation strategy outperforms the baseline algorithms in terms of the achievable secrecy rate.