CDMA时变色散信道基于一阶统计量的盲辨识算法

在深入分析CDMA时变色散信道的离散正则模型的基础上,给出了一种新的CDMA时变色散信道的盲辨识方法.使用解相关接收机分离出时变有效特征波形中的信道参数后,仅利用处理后信号的一阶统计量,通过少量的导频符号,就可以实现对信道的辨识.这种方法和通常的基于二阶统计量的盲辨识算法相比具有更低的运算复杂度,同时所需要的观察数据也更少.仿真结果证明了算法的有效性.     

对CDMA时变色散信道基于离散正则模型的盲辨识方法

本文通过将扩展函数在时延扩展域和Ｄｏｐｐｌｅｒ扩展域进行采样，得到了ＣＤＭＡ时变色散信迢的离散正则模型，此模型适宜于采用二阶统计量方法对ＣＤＭＡ时变色散系统进行盲信号处理。文章同时给出了一种对正则采样值的子空间盲辨识算法。与基于基展开模型处理时变信道的方法不同的是，这种基于离散正则模型的盲辨识方法不需借助高阶统计量估计信道的指数基频率，也不必假设相邻符号间的时延变化呈线性关系，而且赋予了基展开坐标明确的物理意义。文章通过仿真验证了算法的有效性。     

CDMA时变色散信道的快速半盲辨识方法

利用CDMA时变色散信道的离散正则模型,给出了一种新的信道快速盲辨识算法,首先使用时-频解相关RAKE接收机消除了多址干扰的影响,然后再利用解相关处理后信号的一阶统计量,实现对信道的辨识。和基于二阶统计量以及高阶统计量的盲辨识算法相比,该算法仅需要少量的导频符号,就可实现对信道的估计,具有更低的计算复杂度和更好的抗噪性能。仿真结果证明了算法的有效性。     

水声稀疏时变SIMO信道盲均衡算法

基于复指数基扩展模型（Complex exponential basis expansion model, CE-BEM）,利用信道的稀疏特性和发送信号的常模特性（Constant Modulus, CM）,提出水声稀疏时变（Time-variant, TV）SIMO信道盲均衡算法。首先采用l0-范数约束的比例系数归一化最小均方误差常模算法对等效信道矩阵的稀疏时不变部分进行均衡,然后采用基频率估计算法估计基频率并对多普勒频移进行补偿,最后对恢复信号中存在的相偏进行估计补偿。仿真实验结果表明,本文算法提高了均衡器的收敛速度,降低了剩余码间干扰。      

一种基于子空间分解的IIR信道盲辨识算法

本文证明了对IIR信道输出进行过采样（采样率是输入码率的整数倍）可以转化成单输入多输出的多信道模型，并且不同的信道有相同的AR系数。基于这一特性本文提出一种基于子空间分解的信道参数盲辨识方法，即不同信道的MA系数可以输出信号的噪声子空间唯一确定，而AR系数则可以通过求解YW方程得到。     

色散CDMA信道中基于子空间的盲多用户检测

用多输入多输出(MTMO)信号模型描绘色散CDMA(码分多址)系统,而后用盲MTMO信道检测和均衡理论,同时结合所需用户的特征波形,应用子空间的方法来判定每个用户的色散CDMA信道脉冲响应。基于所识别的信号子空间参数和信道响应,构成具有抑制码间干扰(ISI)和多址干扰(MAI)能力的两种线性检测器(最小均方误差检测器和迫零检测器),且没有额外的计算代价。     

时变WOC信道的二阶盲辨识与估计研究

时变及干扰严重是室内光无线通信应用的主要限制.本文引入基于二阶统计量的盲辨识信道估计与去噪策略,对WOC室内信道变化进行自适应跟踪.采用不同的WOC信道作为研究对象,完成了对噪声的估计及信道系数的预测.模拟中对SNR的跟踪范围达30dB,结果证明该方法对信道变化具有适应性.利用该方法对WOC进行改进,可以获得稳定、高效的WOC室内应用系统.     

CDMA移动通信系统中的信道盲与半盲估计

介绍了应用于异步CDMA移动通信系统中的信道盲估计技术的原理,信道盲估计主要分为子空间分解、相关拟合和最大似然三种方法。分析了各自的特点,然后讨论了在部分发送数据已知条件下的半盲信道估计技术。     

信道盲辨识的新方法

只要单输入多输出(SIMO)信道的公因式满足本文提出的充分必要条件，那么本文方法就可以有效地辨识这些带公零点的信道．本文算法由以下步骤组成：先借助整数约束二次优化盲检测属于给定字符集的发送信号，然后根据这些估得的发送信号辨识传输信道．仿真结果表明：本文新算法明显优于现有的文献算法．     

一种改进的稀疏多径信道盲辨识算法

针对无线多径稀疏信道,利用信道有效近似思想,提出了一种改进的基于矩阵外积分解的信道盲辨识与盲均衡算法。算法首先利用改进的VIA信道阶数估计准则,对多径稀疏信道“有效部分”的阶数进行精确估计,然后利用改进的矩阵外积分解算法估计出信道冲激响应的“有效部分”,最后利用该估计结果对接收数据进行反卷积运算,恢复出发送信号。为了降低噪声以及信道冲激响应中的“零抽头”部分对信道盲辨识性能的影响,本算法对噪声方差估计方法进行了改进,提高了算法在中、低信噪比条件下的盲辨识性能。与现有算法相比,本算法不仅降低了对信噪比的要求,而且克服了基于LC准则的子空间算法(SSA, Subspace Algorithm)的相位偏转问题,其中噪声方差的估计方法也可应用于信噪比估计技术。仿真实验以及对SPIB微波信道测试结果验证了本文算法的有效性。      

SUBSPACE METHOD FOR BLIND IDENTIFICATION OF CDMA TIME—VARYING CHANNELS

A new blind method is proposed for identification of CDMA Time-Varyin(TV) channels in this paper.By representing the TV channel‘s impulse responses in the delay-Doppler spread domain, the discrete-time canonical model of CDMA-TV systems is developed and a subspace method to identify blindly the Time-Invariant(TI) coordingates is proposed.Unlike existing basis expansion methods, this new algorithm does not require estimation of the base frequencies, neither need the assumption of linearly varying delays across symbols.The algorithm offers definite explanation of the expansion coordinates.Simulation demonstrates the effectiveness of the algorithm.     

Adaptive blind receivers for MC‐CDMA communication systems

In this paper, we propose three adaptive blind algorithms for multiuser multicarrier code division multiple‐access systems in multipath fading channels. The proposed adaptive blind receivers are based on the property of the discreteness of the input data symbol and are updated in every symbol interval. We also use the concept that the variance of the output signal approaches to the variance of the desired signal to get the cost function. The three proposed receiver structures are the traditional finite impulse response (FIR) structure, the despreading (DES) filter structure and the generalized sidelobe canceller (GSC) structure. The advantage of the FIR filter is that the length of the filter weights does not have to be the same length as the spreading code. For the DES filter, the combination of the adaptive weight and the despreading code has the simplest structure than the other two proposed receiver structures. The constrained GSC filter is superior to the other two proposed receiver structures in the environments dominated by multiple‐access interference. By this constraint, the blind GSC filter can guarantee to converge to the desired solution. Simulation results are given to show the effectiveness and comparison of the proposed adaptive blind receivers. Copyright © 2012 John Wiley & Sons, Ltd.     

EM-based blind LDPC identification in multipath channels

As the advent of cognitive radios,blind encoder identification has attracted increasingly attentions since it plays an important role.The existing works mainly focus on additive white Gaussian noise (AWGN) channel,while the blind identification in multipath scenarios has not been sufficiently investigated.Considering the blind low density parity-check (LDPC) codes identification in the presence of unknown multipath fading channel,a likelihood-based classifier was proposed using the expectation maximization (EM) algorithm to obtain the maximum likelihood estimates of the unknown parameters.Then,an average log-likelihood ratio (LLR) estimator was adopted to classify the unknown encoder.Numerical results show that the proposed algorithm provides promising identification performance in multipath channels,especially in the low signal-to-noise ratio region.     

The LSCM_SUB algorithm for blind multiuser detection in multipath CDMA channels

1 Introduction Multiuser detection (MUD) is applied mainly in CDMA to cancel the multiaccess interference. The single-user matched filter or RAKE receiver treats interference from other users as noise, but MUD takes advantage of other user’s interference…     

在OFDM系统中用循环前缀对时变色散信道进行估计

目前，正交频分复用（OFDM）技术困能在无线时变信道中进行高速数据传输而受到广泛的关注。在相干的OFDM系统中，接收机能否获得准确的信道状态信息（CSI）是系统性能提高的关键。为了能在接收端获得准确的CSI和提高系统的传输速率，文中将文献[3]的算法由单路发射推广为I/Q两路发射，采用复抽头系数的FIR滤波器对多径衰落信道进行建模，并用通常被丢弃的循环前缀作为训练序列对信道进行估计和均衡，仿真结果表明改进的算法在相同的子数和子载波和比文献[3]传输效率提高一倍的情况下能有效地自动跟踪信道的变化。     

Decision-aided-based multiple blind PN code estimation algorithm of asynchronous CDMA signal

Aiming at the problem of blind estimation of multi-user pseudo-code of multi-path asynchronous code division multiple access (CDMA) signal,using the finite element (FA) characteristic of transmitted symbol,a decision aid (DA) method based on maximum likelihood was proposed.A two-step iterative estimation structure for PN code,transmitted bit and channel was designed to realize the estimation of multiple user code in asynchronous CDMA system with superior performance.Moreover,the Cramer-Rao bound (CRB) of PN code estimation in asynchronous CDMA signal was derived to evaluate the performance of proposed method.Simulation indicates significant improvement in performance which is close to the theory bound of the proposed method compared to commonly-used iterative least square with projection (ILSP) method.The method can also achieve superior estimation when the user number increases.     

一种新的盲自适应多用户检测算法

多址干扰引发严重的远 /近问题。本文提出一种新的代价函数 :差分平均输出能量(DMOE) ,并设计了适用于DS/CDMA系统的盲多用户检测算法。理论分析和数值模拟表明该算法的收敛性能及误码性能均优于MOE检测器     

Joint Angle and Delay Estimation (JADE) in Antenna Array CDMA Systems

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