一种快速,低运算量的信道辨识算法

在离散多音频（ＤＭＴ）系统中,保证通信正常进行的关键之一是完成收发信机的时域和频域均衡器的正确设置。一般的均衡器训练算法计算量较大。为了降低对计算量的要求,同时保证的精确度,本文提出一种基于信道辨识的均衡器训练算法。该算法将信道等效为一个ＡＲＭＡ（自回归滑动平均）模型,应用正交最小二乘法（ＯＬＳ）可快速估计出这个ＡＲＭＡ模型的阶数和参数,同时也就得到了均衡器系数的值。实验结果证明,本算法计算量较小     

DMT调制系统中一种新的信道冲激响应最优缩短算法

在离散多音调制（ＤＭＴ）系统中，每个符号块在进行传输前通常要加入循环前缀（ＣＰ），以保证子信道之间的相互独立性，消除符号块间的干扰。ＣＰ的长度等于有效信道冲激响应的记忆长度。较长的ＣＰ大大降低了ＤＭＴ调制系统的传信率。为了避免采用较长的ＣＰ，通常在接收端采用有限冲激响应滤波器（ＦＩＲ）缩短有效信道冲激响应的长度。文献［１］给出了计算最优缩短冲激响应滤波器（ＳＩＲＦ）抽头系数的算法，但该算法要求ＳＩＲＦ抽头的长度必须小于或等于目标冲激响应的记忆长度。本文改进了这种算法，使其可计算任意长度ＳＩＲＦ的抽头系数。     

快速时域模拟器FTSIM

开关级快速时域模拟器ＦＴＳＩＭ，可对ＭＯＳ ＬＳＩ／ＶＬＳＩ数字电路进行逻辑功能和时间特性的模拟与验证。基于波形松弛算法，ＦＴＳＩＭ首先将电路分解成直流连通单元（ＤＣＣ），然后利用晶体管非线性模型按一定次序计算每个ＤＣＣ的输出波形。在求解该模型特征方程的过程中，采用了电压步进方法，同时提出了处理ＤＣＣ之间反馈问题的事件驱动自适应窗口算法。ＦＴＳＩＭ可以充分利用电路的多速率特性和各类休眠特性来提高分     

频谱分析和DSP频谱分析仪

本文的目的是介绍用ＤＳＰ芯片制造数字频谱分析仪。为此，首先讨论了傅氏分析：复习了时间连续信号和时间离散信号的频谱定义；从实用的计算观点推导了离散傅氏变换（ＤＦＴ）；叙述了快速傅氏变换（ＦＦＴ）的基本思想，以解释为什么ＦＦＴ算得快。文章的最后部分指出了ＤＳＰ频谱仪和传统频谱仪相比的特点。给出了ＤＳＰ频谱仪的硬件方框图和软件流程图。解释了为什么ＤＳＰ芯片特别适合于执行ＦＦＴ算法。     

一种基于DMT技术的HFC反向信道传输方案

详细阐述了用于ＨＦＣ（光纤混合同轴电缆）网络上行信道数据传输的ＳＤＭＴ（同步多载波调制）系统的原理,分析了其性能。与采用单载波系统进行比较,得到的结论是：ＳＤＭＴ具有更大的优越性,它是用于ＨＦＣ反向信道传输的一个较先进的解决方案。     

一种新的用于高速波分复用系统的色散补偿方案

本文提出了一种用于高速多路波分复用（ＷＤＭ）陆上级联掺铒光纤放大器（ＥＤＦＡ）光纤通信系统的色散补偿方案，其特点是：利用特殊设计的色散位移光纤ＳＤＤＳＦ（零色散波长λ０≈１．６μｍ，色散斜率Ｓ＿０＝０．０５ｐｓ／ｋｍ／ｎｍ２），在１５５０ｎｍ处产生－２～－４ｐｓ／ｋｍ／ｎｍ的色散，以避免ＩＴＵ－ＴＧ．６５３色散位移光纤在多路复用时的四波混频（ＦＷＭ）效应；并利用ＩＴＵ－ＴＧ．６５２标准单模光纤（非色散位移光纤ＮＤＳＦ）在１５３０～１５７０ｎｍ（ＥＤＦＡ工作带宽）范围内，有效地补偿ＳＤＤＳＦ所引入的负色散。此方案可使单路数据率高于１０Ｇｂ／ｓ的波分复用系统，经１０００ｋｍ传输后因色散引入的眼图恶化量仍＜１ｄＢ。     

DS－SFH扩频多址系统在瑞利衰落信道中多径分集的性能研究

本文讨论了混合ＤＳ－ＳＦＨ扩频多址ＳＳＭＡ通信系统在瑞利衰落信道中多径分集接收的性能。基于多径干扰、多址干扰和信道噪声之和为一个高斯随机变量的分析，推导了在等增益组合（ＥＧＣ）和选择最大（ＳＭ）多径分集接收算法下，扩频系统的平均差错概率。理论分析和数值模拟指出：扩频多径分集接收可以明显地改善ＤＳ－ＳＦＨＳＳＭＡ系统的性能，在提高系统性能方面，等增益组合算法优于选择最大分集算法。     

VDM+EDFA系统中光纤非线性效应影响的研究

系统分析了光纤非线性效应对光纤主干网ＷＤＭ＋ＥＤＦＡ扩容的影响，在信道间隔相等的条件下，得出了光纤非线性响应影响下的阈值功率，信道数，信道间隔和ＥＤＦＡ级联数等之间的关系。结果表明，在信道数和信道间隔不同时，ＦＷＭ，ＸＰＭ和ＳＲＳ分别起不同作用；为实现ＷＤＭ＋ＥＤＦＡ技术，每个信道的输入功率必须小于一定值。     

声表面波技术

１声表面波技术９５００１ＳＡＷ换能器及其应用研究─—小田川裕之。东北大学电通谈话会记录（ＪＰＮ），１９９３；６２（１）：２９～３０采用浮置电极单向换能器（ＦＥＵＤＴ）制作了２ＧＨｚ的ＳＡＷ滤波器。通过改变相并列的ＦＥＵＤＴ的距离进行加权。采用１２８°...     

正交频分复用系统时域均衡器一种优化准则

本文提出了一种新的我频分复用（ＯＦＤＭ）系统时域均衡器的化准则,即最小缩短信道方差（ＭＳＣＳＥ）准则,基于该准则导出了一种非常实用的优化算法,同时,本文还证明在一定条件下,通常的最匀方差（ＭＭＳＥ）准则将转化为ＭＳＣＳＥ准则,并对各种算法的性能做了比较。     

自适应均衡算法在信道均衡技术中的应用研究

文中描述了两种非线性均衡器分别为判决反馈均衡器(DFE)和最大似然序列估计(MLSE)均衡器.所用信道模型为加性白高斯噪声信道,在DFE和线性均衡器(LE)中都是使用递归最小二乘(RLS)算法和最小均方(LMS)算法对数据进行分块处理.MLSE均衡器中使用了维特比最佳译码算法.就误比特性能来做以比较,DFE远好于LE,MLSE均衡器又明显优于DFE,并且它能达到几乎最优的性能.     

Fuzzy stochastic gradient decision feedback equalizer for VSBterrestrial HDTV broadcasting

We present a fuzzy stochastic gradient (FSG) decision feedback equalizer (DFE) for VSB terrestrial HDTV broadcasting. This equalizer employs a well-designed fuzzy Takagi-Sugeno (1985) model to automatically regulate the step size of the descent gradient vector, combining a fast convergence rate and a low excess mean square error (MSE). The only penalty paid is a slight increase in the computational complexity compared with the LMS algorithm. Simulation results show that this equalizer provides 3.5 dB signal-to-noise ratio (SNR) improvement at a BER of 3.0×10^-6 with respect to the conventional LMS DFE recommended by the Grand Alliance     

Stochastic Unbiased Minimum Mean Error Rate Algorithm for Decision Feedback Equalizers

Capitalizing on a well-known minimum mean-square error (MMSE) property for decision feedback equalization (DFE) along with the use of stochastic gradient approach, we formulate an adaptive minimum error rate (MER) algorithm for DFE over M-ary PAM channels to be named as stochastic unbiased minimum mean-error rate (SUMMER). Comparisons are made between our algorithm and existing MER algorithms in the literature. Also, by invoking the central limit theorem, we present an analytical proof that an unbiased MMSE equalizer will approach an MER equalizer when the equalizer length approaches infinity; thereby, we obtain a lower bound expression for MER.     

基于多用户反馈的判决反馈均衡器的研究

本文提出的一种新颖的基于多用户反馈的判决反馈均衡器,解决了在CDMA多用户检测中传统自适应判决反馈均衡器误码率高、系统容量小的缺点.它由具有误差反馈滤波器的判决反馈均衡器(Decision Feedback Equalizer with Error Feedback Filter,DFE-EFF)构成,并在判决后反馈多用户数据抵消多址干扰(多用户反馈干扰抵消).文中给出其结构图,分析各种判决反馈均衡算法.理论证明,具有误差反馈滤波器的多用户反馈干扰抵消判决反馈均衡器(多用户反馈干扰抵消DFE-EFF)较各种判决反馈均衡器为最优,它能同时有效处理ISI,MAI和噪声的干扰.仿真结果表明,在误码率性能和系统容量两方面,多用户反馈干扰抵消DFE-EFF比DFE、DFE-EFF均有较大改善.     

A blind decision feedback equalizer incorporating fixed lagsmoothing

A new type of blind decision feedback equalizer (DFE) incorporating fixed lag smoothing is developed in this paper. The structure is motivated by the fact that if we make full use of the dependence of the observed data on a given transmitted symbol, delayed decisions may produce better estimates of that symbol. To this end, we use a hidden Markov model (HMM) suboptimal formulation that offers a good tradeoff between computational complexity and bit error rate (BER) performance. The proposed equalizer also provides estimates of the channel coefficients and operates adaptively (so that it can adapt to a fading channel for instance) by means of an online version of the expectation-maximization (EM) algorithm. The resulting equalizer structure takes the form of a linear feedback system including a quantizer, and hence, it is easily implemented. In fact, because of its feedback structure, the proposed equalizer shows some similarities with the well-known DFE. A full theoretical analysis of the initial version of the algorithm is not available, but a characterization of a simplified version is provided. We demonstrate that compared to the zero-forcing DFE (ZF-DFE), the algorithm yields many improvements. A large range of simulations on finite impulse response (FIR) channels and on typical fading GSM channel models illustrate the potential of the proposed equalizer     

运用误差反馈的判决反馈均衡器的性能分析

判决反馈均衡器（Decision Feedback Equalizer，DFE）能补偿具有严重符号间干扰（Inter Symbol Interference，ISI）的信道，且不存在线性均衡器增强噪声的影响。而在其基础上改进的运用误差反馈的DFE，可利用误差反馈滤波器来减少传统DFE中存在的误差信号的相关性，同时其硬件实现的复杂度没有明显提高。理论分析和仿真表明，这种方法比传统的DFE更有效，特别是针对信道有严重符号间干扰的情况。     

Adaptive decision feedback equalization: can you skip the trainingperiod?

This paper presents a novel unsupervised (blind) adaptive decision feedback equalizer (DFE). It can be thought of as the cascade of four devices, whose main components are a purely recursive filter (ℛ) and a transversal filter (𝒯). Its major feature is the ability to deal with severe quickly time-varying channels, unlike the conventional adaptive DFE. This result is obtained by allowing the new equalizer to modify, in a reversible way, both its structure and its adaptation according to some measure of performance such as the mean-square error (MSE). In the starting mode, ℛ comes first and whitens its own output by means of a prediction principle, while 𝒯 removes the remaining intersymbol interference (ISI) thanks to the Godard (1980) (or Shalvi-Weinstein (1990)) algorithm. In the tracking mode the equalizer becomes the classical DFE controlled by the decision-directed (DD) least-mean-square (LMS) algorithm. With the same computational complexity, the new unsupervised equalizer exhibits the same convergence speed, steady-state MSE, and bit-error rate (BER) as the trained conventional DFE, but it requires no training. It has been implemented on a digital signal processor (DSP) and tested on underwater communications signals-its performances are really convincing     

应用于10 Gbit/s光通信及背板传输的自适应均衡器设计

描述了一种既可用于背板传输也可用于光纤通信的高速串行收发器前端均衡器的设计。为适应光信号在传播中的色散效应,使用前馈均衡器(FFE)加判决反馈均衡器(DFE)的组合,取代了背板通信中常用的连续时间线性均衡器(CTLE)和DFE的组合。设计使用3 pre-tap、3 post-tap和1个main tap的抽头组合方式,兼顾pre-cursor和post-cursor的信号失真,有效补偿范围为15 dB。补偿系数采用完全自适应算法调整,对FFE采用模拟MSE算法调整,DFE引擎采用1/16速率数字sign-sign最小均方差(LMS)算法实现。芯片使用UMC 28 nm工艺流片,输入信号频率为10 Gbit/s。     

BAD: bidirectional arbitrated decision-feedback equalization

The bidirectional arbitrated decision-feedback equalizer (BAD), which has bit-error rate performance between a decision-feedback equalizer (DFE) and maximum a posteriori (MAP) detection, is presented. The computational complexity of the BAD algorithm is linear in the channel length, which is the same as that of the DFE, and significantly lower than the exponential complexity of the MAP detector. While the relative performance of BAD to those of the DFE and the MAP detector depends on the specific channel model, for an error probability of 10/sup -2/, the performance of BAD is typically 1-2 dB better than that of the DFE, and within 1 dB of the performance of MAP detection.     

Iterative Equalization using Improved Block DFE for Synchronous CDMA Systems

Iterative equalization using optimal multiuser detector and optimal channel decoder in coded CDMA systems improves the bit error rate (BER) performance tremendously. However, given large number of users employed in the system over multipath channels causing significant multiple-access interference (MAI) and intersymbol interference (ISI), the optimal multiuser detector is thus prohibitively complex. Therefore, the sub-optimal detectors such as low-complexity linear and non-linear equalizers have to be considered. In this paper, a novel low-complexity block decision feedback equalizer (DFE) is proposed for the synchronous CDMA system. Based on the conventional block DFE, the new method is developed by computing the reliable extrinsic log-likelihood ratio (LLR) using two consecutive received samples rather than one received sample in the literature. At each iteration, the estimated symbols by the equalizer is then saved as a priori information for next iteration. Simulation results demonstrate that the proposed low-complexity block DFE algorithm offers good performance gain over the conventional block DFE.