LTE系统中的多径时延估计算法

就LTE系统中单小区信道估计这一课题,给出信道的参数化频域模型,针对多径时延这一参数,比较两种时延估计（TDE）算法,IFFT时延估计算法与MUSIC超分辨率时延估计算法,并进行仿真。得到MUSIC超分辨率时延估计改善了每条径TDE的准确性,但受多普勒频移影响较大,该课题中宜采用IFFT时延估计算法。     

基于改进TLS-ESPRIT的Chirp扩频系统信道估计

提出了一种基于快速伪谱修正的四阶累积量TLS-ESPRIT算法。该算法充分运用了四阶累积量矩阵的数据信息,不但能较准确地估计Chirp扩频系统信道多径时延,而且可有效地识别和剔除虚径,进而建立在时延估计基础上的多径幅度估计就更可靠。针对关键参数在仿真设计和工程应用中的设置,列出了它们需要遵从的三个关系。最后以IEEE802.15.4a信道为传输环境,对该算法进行了仿真验证,并与四阶矩TLS-ESPRIT算法和伪谱搜索算法作了性能对比。     

多径信道下MIMO系统发送天线数估计

为了解决认知无线电或信号截获中多径信道下MIMO系统发送天线数估计问题,首先分析了现有模型在多径信道下失效的原因,将MIMO多径信道模型等效变换出一种虚拟信道矩阵,从而建立多径信道下MIMO系统发送天线数估计模型;然后,利用随机矩阵理论中协方差矩阵最小特征值分布的相关研究结果,证明了时不变瑞利信道的协方差矩阵最小特征值收敛于第二类Tracy-Widom分布,分析了该特点对发送天线数估计的影响,并提出一种改进的RMT估计算法来估计多径信道下MIMO系统发送天线数.最后对改进算法进行了仿真验证,结果表明在低信噪比和小数据条件下,改进算法的估计性能相比RMT算法有较大提升.     

OFDM系统基于信道多径时延检测的自适应信道估计

针对宽带正交频分复用(OFDM)系统,提出了一种基于信道多径时延估计的自适应信道估计算法.文章分析了无线信道的特性,随后利用导频频域相关性进行多径时延估计,提出通过动态跟踪信道时延估计参数自适应选择信道估计中适宜的导频数目的方法,同时实现循环前缀(CP)长度的实时调整.仿真结果表明,在时变环境下,本文算法可以有效获知当前信道时延参数的近似统计信息,实现对系统冗余信息的优化.     

一种新的基于参数信道模型的MIMO信道估计算法

针对频率选择性块衰落MIMO信道,该文提出一种改进的基于参数信道模型的信道估计方法.该方法首先通过修正后的TST-MUSIC算法估计多径的传播时延和角度.由时延和角度信息,得到一种基于参数信道模型的信道估计方法.仿真结果表明此种方法可以有效地减少参数估计的维数,其性能要远远优于非参数的最小二乘估计器.     

基于时延分集的MIMO多径信道盲估计算法

发送时延分集在空时编码中是一种有效可行的方法。本文提出了一种基于发送时延分集的多径信道估计方法,指出如果发送时延大于信道时延,多输入多输出（MIMO）信道可以转化为特殊的单输入多输出信道,通过对信道输出进行子空间分解可以估计出信道参数。仿真结果显示了本文算法的有效性。     

一种空时分布多径信号DOA-时延联合估计的ESPRIT方法

在城市密集环境下,由于局部密集多径反射信号不再符合点目标模型,传统多径参数(波达方向与相对时延)联合估计算法往往失效。针对此类问题本文考虑一种基于空时相干分布的多径模型,并在得到信道估计后将其转化至频率域去卷积获得空时联合信号子空间,由于多径扩展影响该信号子空间不再具有旋转不变结构,本文通过在联合信号子空间中抽取行向量构造不同的矩阵对,使各矩阵对在相位上满足旋转不变性质,然后,利用ESPRIT算法估计中心时延与中心DOA参数。与点目标ESPRIT方法相比该方法能够有效克服多径扩展影响,实现参数自动配对,且具有不敏感于多径分布形式的优点,仿真实验证明了其有效性。     

OFDM系统基于导频的信道多径时延估计

本文针对宽带正交频分复用(OFDM)系统,分析了多径时延扩展与循环前缀(cP)长度及导频数目的关系.随后利用导频的频域相关性估计得到信道时域功率时延谱(PDP),并根据PDP提出信道均方根(RMS)时延及最大多径时延门限值的估计算法.最终实现OFDM系统对信道多径参量的实时跟踪,有利于系统参数自适应调整.仿真结果表明,本文算法在低复杂度条件下可以有效获知当前传输信道模型多径时延参数的近似统计信息.     

一种新颖的水声信道参数估计算法

宽带水声信道通常被建模为多扩展多时延（MSML）信道,不同路径的多普勒扩展不同给信道参数估计带来了挑战.本文提出一种新颖的MSML信道参数估计算法,称之为改进的粒子群优化（MPSO）算法.该算法创建一个多径列表来记录局部最优粒子的位置和适应度值,并用于迭代中粒子速度的更新.算法结束时,根据多径列表的记录值,可以同时估计出每一径的多普勒扩展、时延和幅度参数.仿真结果表明：MPSO算法的参数估计精度优于匹配追踪（MP）算法和分数阶傅里叶变换（FrFT）算法.     

解卷积主动声呐目标回波高分辨时延估计技术

为提高浅海复杂海洋环境下的目标回波时延估计精度,增强主动声呐系统对目标的探测能力,该文基于稀疏表示理论和解卷积思想,提出一种高分辨目标回波时延估计技术。首先,引入Toeplitz算子,将发射信号的不同时延结果构造成时延字典矩阵,时延估计值存在于所求解的稀疏向量中。其次,利用交替方向乘子算法(ADMM)优化框架,求解全局最优解。最后,采用一种加权迭代策略设置正则化参数,进一步抑制多途信道的影响,解耦合出回波到达的时刻,获得高精度的目标回波时延估计结果。数值仿真和实验数据表明,该文提出的解卷积主动声呐目标回波高分辨时延估计技术可以在多途扩展严重的浅海声信道实现目标探测,在信道水池的实验环境下,时延估计分辨率可达0.056 ms。     

基于矩阵束的MIMO雷达低仰角快速估计方法

针对多径效应的影响,提出了一种基于矩阵束的MIMO雷达低仰角快速估计方法。该方法同时考虑了发射多径信号和接收多径信号,采用单样本数信号矢量构造了一个前后向矩阵束,并利用两个酉矩阵对该矩阵束进行降维处理,最后采用广义特征值分解的总体最小二乘法来估计目标角度。算法不需要估计数据协方差矩阵,可在低信噪比和单样本数情况下,有效地克服多径效应,实现同时多目标低仰角估计,相比最大似然算法,避免了谱峰搜索,计算量小。仿真结果验证了该算法的有效性。     

Time-domain measurements with the Hewlett-Packard network analyzerHP 8510 using the matrix pencil method

The generalized pencil of function (GPOF) method, also known as the matrix pencil method, is used to improve the resolution of HP 8510B network analyzer data in the time domain. This method provides for much higher resolution than the Fourier techniques. A comparison of the two methods is given for the example of the Beatty standard. The examples show that a parametric technique such as the GPOF can provide accurate and reliable results with a high degree of resolution even when the fast Fourier transform (FFT)-based technique fails     

An ESPRIT-like method for quadratic phase coupling estimation

Two algorithms are proposed for estimating the quadratically coupled frequency pairs (QC pairs) in a signal consisting of complex sinusoids in white noise. Three matrices are constructed from the complex third-order cumulants of the noisy signal, the second and third being time shifted versions of the first. The list of coupled frequencies is obtained from the rank reducing numbers of the matrix pencil formed from the first matrix and either of the latter two. The first algorithm then pairs these components by relating quadratic coupling to the intersection of generalized eigenspaces corresponding to two of these frequencies. The coupling strengths are also obtained in terms of generalized eigenvectors in this intersection space. The second algorithm constructs a two-parameter matrix pencil using all the three matrices. The rank reducing pairs of this pencil on the unit circle yield the QC pairs and the associated generalized eigenvectors: the coupling strengths     

Discrete Fractional Fourier Transform Based on New Nearly Tridiagonal Commuting Matrices

Based on discrete Hermite–Gaussian-like functions, a discrete fractional Fourier transform (DFRFT), which provides sample approximations of the continuous fractional Fourier transform, was defined and investigated recently. In this paper, we propose a new nearly tridiagonal matrix, which commutes with the discrete Fourier transform (DFT) matrix. The eigenvectors of the new nearly tridiagonal matrix are shown to be DFT eigenvectors, which are more similar to the continuous Hermite–Gaussian functions than those developed before. Rigorous discussions on the relations between the eigendecomposition of the newly proposed nearly tridiagonal matrix and the DFT matrix are described. Furthermore, by appropriately combining two linearly independent matrices that both commute with the DFT matrix, we develop a method to obtain DFT eigenvectors even more similar to the continuous Hermite–Gaussian functions (HGFs). Then, new versions of DFRFT produce their transform outputs closer to the samples of the continuous fractional Fourier transform, and their applications are described. Related computer experiments are performed to illustrate the validity of the works in this paper.     

基于GTD模型的目标二维散射中心提取

为精确描述隐身目标的高频电磁散射特性,该文用基于几何绕射理论的GTD模型代替以镜面散射为主的指数和模型.同时,为克服传统矩阵束算法(MEMP)计算量大、距离坐标配对等问题,该文提出用修正矩阵束算法和二维旋转不变技术(2D-ESPRIT)提取基于GTD模型的目标二维散射中心参数.仿真实验表明,该文的两种方法均适用于以边缘绕射等为主要散射源的隐身目标.     

分组密码Cauchy型MDS扩散结构的几点注记

 MDS矩阵是设计分组密码扩散结构的一种重要手段,由有序数组生成的Cauchy矩阵是一类基本的MDS矩阵.本文给出了两个有序数组生成的Cauchy矩阵相同的充要条件,证明了有限域上Cauchy矩阵的个数,证明了Cauchy矩阵一定不是循环移位矩阵;给出了Cauchy矩阵的不同元素个数达到最小值的充要条件,给出了使不同元素个数达到最少,同时1的个数达到最多的Cauchy矩阵的构造方法.此外,本文还提出了对合Cauchy矩阵的一种构造方法.     

A group of permutations that commute with the discrete Fouriertransform

The authors characterize a potentially useful set of permutation matrices that commute with the Fourier matrix of order n. The set of all such permutation matrices is a group under matrix multiplication, and every element of the group is its own inverse. They study the number of these permutations as a function of the order n_ of the Fourier matrix and conclude that it is a multiplicative function of n     

On a Non-homogeneous Singular Linear Discrete Time System with a Singular Matrix Pencil

In this article, we study the initial value problem of a non-homogeneous singular linear discrete time system whose coefficients are either non-square constant matrices or square with an identically zero matrix pencil. By taking into consideration that the relevant pencil is singular, we provide necessary and sufficient conditions for existence and uniqueness of solutions. More analytically we study the conditions under which the system has unique, infinite and no solutions. Furthermore, we provide a formula for the case of the unique solution. Finally we provide some numerical examples based on a singular discrete time real dynamical system to justify our theory.     

Nonminimum-phase FIR channel estimation using cumulant matrix pencils

This paper studies the blind estimation of single-input-single-output channels with finite impulse response (FIR) and nonminimum phase. Based on higher order statistics, we introduce a new algorithm that exploits a matrix pencil constructed from a set of cumulant matrices. By solving a generalized eigenvalue problem, channel estimates (up to a scalar ambiguity) can be obtained from nontrivial generalized eigenvectors of this cumulant matrix pencil. With multiple estimation results available, different schemes are given to extract channel information effectively. The proposed algorithm does not require exact knowledge of the channel length and can function properly under channel length overestimation. Numerical simulations demonstrate the robustness of this new algorithm to various adverse conditions.     

Utilization of a unitary transform for efficient computation in the matrix pencil method to find the direction of arrival

In this study, we use the matrix pencil (MP) method to compute the direction of arrival (DOA) of the signals using a very efficient computational procedure in which the complexity of the computation can be reduced significantly by using a unitary matrix transformation. This method applies the technique directly to the data without forming a covariance matrix. Simulation results show that the variance of the estimate approaches to the Cramer-Rao lower bound. Using real computations through the unitary transformation for the MP method leads to a very efficient computational methodology for real time implementation on a digital signal processor chip. A unitary transform can convert the complex matrix to a real matrix along with their eigenvectors and thereby reducing the computational cost at least by a factor of four without sacrificing accuracy. This reduction in the number of computations is achieved by using a transformation, which maps centro-hermitian matrices to real matrices. This transformation is based on Lee's work on centro-hermitian matrices.