共查询到20条相似文献,搜索用时 109 毫秒
1.
2.
3.
利用调制引入循环平稳的CDMA盲信道估计 总被引:5,自引:0,他引:5
针对CDMA系统给出了一种新颖的盲辨识方法.它利用了恒模复序列调制产生的循环平稳性,其特色是,在接收机上可以根据循环统计量的支撑的不同,将各个用户的二阶循环统计量分离开来,每个用户形成自己的小规模子空间.采用已成熟的子空间方法,可以识别出不同的用户各自的片率传输信道,以便于均衡和检测.文中给出了自己的信道可辨识性的条件和证明,提出了辨识算法,并对算法进行了模拟.方法简单明了,适合于CDMA上行链路信道. 相似文献
4.
《电子科技文摘》2003,(2)
Y2002-63328-2517 0303213点对多点通信树通过链锁的网络线路有损速率估计=Estimation of network link loss rates via chaining in mul-ticast trees[会,英]/Ziotopoulos,A.-G.P.& HeroⅢ,A.O.//The 2001 IEEE International Conferenceon Acoustics,Speech,and Signal Processing Vol.ⅣofⅥ.—2517~2520(HE)0303214关于 CDMA 直放站工程建设中的若干建议[刊]/吴杰//移动通信.—2002,26(9).—67~70(C)0303215CDMA 时变色散信道的两级盲辨识算法[刊]/刘郁林//通信学报.—2002,23(9).—74~81(L)本文通过对时变信道的扩展函数在时频域进行正 相似文献
5.
6.
7.
提出了一种新的基于粒子滤波器的盲辨识及盲均衡算法。在对信道进行辨识时,通过对信道均值的采样来代替对真实信道的采样,避免了对信道的后验密度进行采样,从而降低了算法的复杂度。算法还采用先验密度作为重要性函数,以便于对重要性函数进行采样。仿真结果表明,该算法收敛速度快,所需的数据量少,在信噪比较低时也能完成对信道的盲辨识和盲均衡。 相似文献
8.
针对全盲信道辨识算法无法辨识含公零点信道且对信道阶数误差敏感的问题,提出一种半盲信道辨识算法。通过奇异值分解将信道矩阵分解为同维矩阵与酉矩阵乘积的形式,分别利用接收数据和已知符号求解同维矩阵与酉矩阵,最终得到信道矩阵的闭式解。该算法有效地克服了全盲信道辨识算法的诸多局限性,避免了传统半盲方法面临的最优加权选择问题,性能稳定,且对信道噪声与信道阶数都具有较强的鲁棒性。仿真实验验证了所提算法的有效性与优越性。 相似文献
9.
10.
针对SIMO信道的经典盲估计方法,如子空间法(SS)等,都是基于接收端样本自相关阵的特征值分解(EVD)或奇异值分解(SVD)来实现信道估计的,而基于QR分解的SIMO信道盲辨识方法是最近提出的一种性能优良的新算法.本文将该算法推广为MIMO信道盲辨识算法,并且证明了在一定的假设下,即使各路源信号为空间相关且其统计特性未知时,该算法仍然保持有效.实验结果表明这种MIMO辨识算法具有收敛速度快、计算量小、无须对噪声做额外的处理、对噪声不敏感等优点.我们还将这种算法与经典的MIMO辨识算法进行了性能比较. 相似文献
11.
双循环相关复倒谱的多用户盲信道辨识方法 总被引:5,自引:2,他引:3
该文针对多用户系统提出了一种新颖的盲辨识方法.它利用了调制引入的循环平稳性,可以识别出不同的用户不同的传感器(天线)各自的传输信道.利用循环复倒谱的方法可以给出信道的估计,方法简单明了,与现有的方法相比有一定的优势,适合于多用户上行链路信道.文中还给出了信道可辨识性的条件和证明,提出了辨识算法,并对算法进行了模拟. 相似文献
12.
Lang Tong Guanghan Xu Kailath T. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1994,40(2):340-349
A new blind channel identification and equalization method is proposed that exploits the cyclostationarity of oversampled communication signals to achieve identification and equalization of possibly nonminimum phase (multipath) channels without using training signals. Unlike most adaptive blind equalization methods for which the convergence properties are often problematic, the channel estimation algorithm proposed here is asymptotically ex-set. Moreover, since it is based on second-order statistics, the new approach may achieve equalization with fewer symbols than most techniques based only on higher-order statistics. Simulations have demonstrated promising performance of the proposed algorithm for the blind equalization of a three-ray multipath channel 相似文献
13.
A novel method for the blind identification of a non-Gaussian time-varying autoregressive model is presented. By approximating the non-Gaussian probability density function of the model driving noise sequence with a Gaussian-mixture density, a pseudo maximum-likelihood estimation algorithm is proposed for model parameter estimation. The real model identification is then converted to a recursive least squares estimation of the model time-varying parameters and an inference of the Gaussian-mixture parameters, so that the entire identification algorithm can be recursively performed. As an important application, the proposed algorithm is applied to the problem of blind equalisation of a time-varying AR communication channel online. Simulation results show that the new blind equalisation algorithm can achieve accurate channel estimation and input symbol recovery 相似文献
14.
15.
Precoder design and blind identification of MIMO channels 总被引:1,自引:0,他引:1
《Signal Processing, IEEE Transactions on》2006,54(7):2725-2736
In this paper, blind identification problem based on second-order statistics (SOS) of received signals is investigated for multiple-input multiple-output (MIMO) channels. It is shown that precoders introduced in transmitters can provide certain extra information for blind identification problem and commonly used identifiability conditions on MIMO channels can be relaxed. A design criterion for the precoders in frequency domain is proposed. Two blind identification algorithms based on the knowledge of the precoders and SOS of the received signals are then developed. In these algorithms, due to particular structure of the precoders, the blind identification problem for a MIMO channel is decomposed into several independent single-input multiple-output (SIMO) channel identification problems. The presented algorithms are robust to an overestimated channel order and not sensitive to signal-to-noise ratio (SNR). Compared with the existing results, a larger class of MIMO finite-impulse-response (FIR) channels can be identified by the new methods. 相似文献
16.
In this paper, a novel generalization of subspace-based blind channel identification methods in cyclic prefix (CP) systems is proposed. For the generalization, a new system parameter called repetition index is introduced whose value is unity for previously reported special cases. By choosing a repetition index larger than unity, the number of received blocks needed for blind identification is significantly reduced compared to all previously reported methods. This feature makes the method more realistic especially in wireless environments where the channel state is usually fast-varying. Given the number of received blocks available, the minimum value of repetition index is derived. Theoretical limit allows the proposed method to perform blind identification using only three received blocks in absence of noise. In practice, the number of received blocks needed to yield a satisfactory bit-error-rate (BER) performance is usually on the order of half the block size. Simulation results not only demonstrate the capability of the algorithm to perform blind identification using fewer received blocks, but also show that in some cases system performance can be improved by choosing a repetition index larger than needed. Simulation of the proposed method over time-varying channels clearly demonstrates the improvement over previously reported methods. 相似文献
17.
在盲信道均衡或盲语音去混响应用中,盲多信道系统辨识通常是信号解卷积的前提条件,即盲辨识过程后跟一个解卷积过程。本文提出一种基于卡尔曼滤波的同步盲系统辨识与解卷积方法,其中卡尔曼滤波的状态矢量由多信道系统参数与源信号矢量组成,过程方程和测量方程则建立在单输入-多输出系统(SIMO)的输入输出关系及信道间交叉关联关系(Cross Relation)基础上。此外,盲系统辨识部分与解卷积部分是可以解耦的,生成两个看似独立的卡尔曼滤波问题,并且这两个卡尔曼滤波问题可以实现并行计算。与级联结构相比,这种并行结构更有利于算法优化和实时信号处理。仿真表明,对于无噪声理想信号模型,本算法可以实现完全系统辨识和解卷积(信号误差比可达到100 dB以上),说明理论正确;对于实测的混响语音信号亦可以实现一定的去混响效果。 相似文献
18.
19.
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. 相似文献
20.
本文报道用自行设计的扫描隧道显微镜对光盘预刻槽进行测量。为观察大范围的结构,我们设计了一个新的大范围扫描头(~6μm),并成功地观察到预刻的槽形,给出了光盘预刻槽的灰度图像、三维轮廓像及剖面轮廓。为评价预刻的槽形提出了一种有效的测量手段。 相似文献