In this paper,a reconfigurable intelligent surface(RIS)-assisted MIMO wireless secure communication system is considered,in which a base station(BS)equipped with multiple antennas exploits statistical channel state in...
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In this paper,a reconfigurable intelligent surface(RIS)-assisted MIMO wireless secure communication system is considered,in which a base station(BS)equipped with multiple antennas exploits statistical channel state information to communicate with a legitimate multi-antenna user,in the presence of an eavesdropper,also equipped with multiple *** firstly obtain an analytical expression of the ergodic secrecy rate based on the results of largedimensional random matrix ***,a jointly alternating optimization algorithm with the method of Taylor series expansion and the projected gradient ascent method is proposed to design the transmit covariance matrix at the BS,as well as the diagonal phaseshifting matrix to maximize the ergodic secrecy *** are conducted to demonstrate the accuracy of the derived analytical expressions,as well as the superior performance of our proposed algorithm.
In this letter, we investigate the secrecy rate of a reconfigurable intelligent surface (RIS)-aided millimeter-wave (mmWave) system with low-resolution digital-to-analog converters (LDACs). Compared to the RIS-aided s...
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In this letter, we investigate the secrecy rate of a reconfigurable intelligent surface (RIS)-aided millimeter-wave (mmWave) system with low-resolution digital-to-analog converters (LDACs). Compared to the RIS-aided systems in most existing works, we consider how to alleviate the hardware loss and improve the secrecy rate by using RIS. In particular, we formulate a secrecy rate maximization problem with hardware constraints. To handle the problem, an alternatingoptimization (AO)-based algorithm is proposed. Specifically, we first use the successive convex approximation (SCA) method to obtain the transmit beamforming. Then, the element-wise block coordinate descent (BCD) method is used to obtain the RIS phase shifts. Numerical results demonstrate that the RIS can mitigate the hardware loss, and the proposed AO-based algorithm with low complexity outperformances the baselines.
As a passive programmable reflecting device, Reconfigurable Intelligent Surface (RIS) can change signal transmission conditions very well and is now widely used in physical layer security (PLS) communications. However...
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As a passive programmable reflecting device, Reconfigurable Intelligent Surface (RIS) can change signal transmission conditions very well and is now widely used in physical layer security (PLS) communications. However, due to the low cost of RIS, eavesdroppers (Eves) may equip themselves with illegal RIS in the future to reduce the secrecy rate (SR) of the system. In this correspondence, we design a maximum-minimum problem for the interplay between legal and illegal RISs on the SR, and propose two schemes to improve the SR. Scheme I designs an alternating optimization algorithm based on Riemannian manifolds to determine the degree of the illegal RIS on the system SR and tries to offset its impact by increasing the number of reflected elements of the legal RIS. Scheme II replaces the legal passive RIS with the legal active RIS and designs an alternatingoptimization scheme based on semi-positive definite relaxation (SDR) and Lemma I for the non-convex problem caused by the legal active RIS. The final simulation results show that both proposed schemes can effectively ensure PLS in the presence of illegal RIS.
When deploying Reconfigurable Intelligent Surface (RIS) to improve System Sum-Rate (SSR), the timeliness and accuracy of SSR optimization methods are difficult to achieve simultaneously through a single algorithm. Som...
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When deploying Reconfigurable Intelligent Surface (RIS) to improve System Sum-Rate (SSR), the timeliness and accuracy of SSR optimization methods are difficult to achieve simultaneously through a single algorithm. Some algorithms focus on timeliness, while some focus on accuracy. In this paper, in order to take into account the timeliness and accuracy of the system comprehensively, we construct SSR analysis model of RIS-assisted multi-user downlink communication system and propose several new optimization methods. The goal is to maximize SSR by using the proposed algorithms to jointly optimize power allocation and reflection coefficients. To solve this comprehensive problem, two sets of alternatingoptimization (AO)-based timeliness algorithms and one set of Monotonic optimization (MO)-based accuracy algorithms are proposed separately to jointly optimize system performance. First, the Water-Filling (WF)-based and penalty-based low complexity algorithms are developed to optimize power allocation and reflection coefficients respectively. To improve the reality of the calculation, penalty-based algorithm cleverly considers residual noise that is difficult to calculate. Then, for further improve the timeliness, a new Successive Convex Approximation (SCA)-based low complexity algorithm is designed to further optimize reflection coefficients and its convergence is proved. Third, in order to verify the effectiveness of the proposed timeliness algorithms, we further propose MO-based accuracy algorithms, in which, the Polyblock Outer Approximation (POA) algorithm, the Semidefinite Relaxation (SDR) method, and the bisection search algorithm are combined in a novel way. Numerical results confirm the timeliness of AO-based algorithms and the accuracy of MO-based algorithms. They supervise and complement each other.
Limited angle tomography is a severely ill-posed problem yet practically significant in x-ray computed tomography. In recent development, limited angle tomography problem is casted in the form of convex optimization p...
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ISBN:
(纸本)9781509062386
Limited angle tomography is a severely ill-posed problem yet practically significant in x-ray computed tomography. In recent development, limited angle tomography problem is casted in the form of convex optimization problem. In this paper, incorporating anisotropic total variation with Mumford-Shah functional, we propose a novel objective functional and develop the corresponding alternating optimization algorithm. The experimental results demonstrate the efficiency of Mumford-Shah functional minimization for limited angle tomography. Furthermore, we also get the segmentations of reconstructed images.
This paper presents an alternatingoptimization clustering procedure called a similarity-based clustering method (SCM). It is an effective and robust approach to clustering on the basis of a total similarity objective...
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This paper presents an alternatingoptimization clustering procedure called a similarity-based clustering method (SCM). It is an effective and robust approach to clustering on the basis of a total similarity objective function related to the approximate density shape estimation. We show that the data points in SCM can self-organize local optimal cluster number and volumes without using cluster validity functions or a variance-covariance matrix. The proposed clustering method is also robust to noise and outliers based on the influence function and gross error sensitivity analysis. Therefore, SCM exhibits three robust clustering characteristics: 1) robust to the initialization (cluster number and initial guesses), 2) robust to cluster volumes (ability to detect different volumes of clusters), and 3) robust to noise and outliers. Several numerical data sets and actual data are used in the SCIVI to show these good aspects. The computational complexity of SCM is also analyzed. Some experimental results of comparing the proposed SCM with the existing methods show the superiority of the SCM method.
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