公开(公告)号：US20100208788A1

公开(公告)日：2010-08-19

申请号：US12768817

申请日：2010-04-28

申请人： Oscar E. Azazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

发明人： Oscar E. Azazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

IPC分类号： H03H7/40

CPC分类号： H04L7/0062 ,  G01R31/3004 ,  G01R31/3008 ,  G01R31/3016 ,  G01R31/31715 ,  G01R31/318502 ,  G01R31/318552 ,  G01R31/318594 ,  H03M13/256 ,  H03M13/41 ,  H04B3/23 ,  H04B3/32 ,  H04L1/0054 ,  H04L1/0059 ,  H04L1/242 ,  H04L7/0334 ,  H04L25/03038 ,  H04L25/03057 ,  H04L25/03146 ,  H04L25/03203 ,  H04L25/03267 ,  H04L25/03324 ,  H04L25/067 ,  H04L25/14 ,  H04L25/4917 ,  H04L25/497 ,  H04L2025/03363 ,  H04L2025/03369 ,  H04L2025/03458 ,  H04L2025/03477 ,  H04L2025/0349 ,  H04L2025/03496 ,  H04L2025/03503 ,  H04L2025/03617 ,  H04L2025/03643 ,  H04L2025/03745

摘要： A method and a system for providing ISI compensation to an input signal in a bifurcated manner. ISI compensation is provided in two stages, a first stage compensates ISI components induced by characteristics of a transmitter's partial response pulse shaping filter, a second stage compensates ISI components induced by characteristics of a multi-pair transmission channel. First stage ISI compensation is performed in an inverse response filter having a characteristic feedback gain factor K, during system start-up. Second stage ISI compensation is performed by a single DFE in combination with a MDFE operating on tentative decisions output from a Viterbi decoder. As the DFE of the second stage reaches convergence, the feedback gain factor K of the first stage is ramped to zero.

摘要翻译： 一种用于以分叉方式向输入信号提供ISI补偿的方法和系统。 ISI补偿分两阶段提供，第一级补偿由发射机的部分响应脉冲整形滤波器的特性引起的ISI分量，第二级补偿由多对传输信道的特性引起的ISI分量。 在系统启动期间，在具有特性反馈增益因子K的逆响应滤波器中执行第一级ISI补偿。 第二级ISI补偿由单个DFE与由维特比解码器输出的暂定决定操作的MDFE组合执行。 当第二级的DFE达到收敛时，第一级的反馈增益因子K变为零。

公开(公告)号：US07466751B2

公开(公告)日：2008-12-16

申请号：US11204534

申请日：2005-08-16

申请人： Oscar E. Azazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

发明人： Oscar E. Azazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

IPC分类号： H03H7/30

CPC分类号： H04L7/0062 ,  G01R31/3004 ,  G01R31/3008 ,  G01R31/3016 ,  G01R31/31715 ,  G01R31/318502 ,  G01R31/318552 ,  G01R31/318594 ,  H03M13/256 ,  H03M13/41 ,  H04B3/23 ,  H04B3/32 ,  H04L1/0054 ,  H04L1/0059 ,  H04L1/242 ,  H04L7/0334 ,  H04L25/03038 ,  H04L25/03057 ,  H04L25/03146 ,  H04L25/03203 ,  H04L25/03267 ,  H04L25/03324 ,  H04L25/067 ,  H04L25/14 ,  H04L25/4917 ,  H04L25/497 ,  H04L2025/03363 ,  H04L2025/03369 ,  H04L2025/03458 ,  H04L2025/03477 ,  H04L2025/0349 ,  H04L2025/03496 ,  H04L2025/03503 ,  H04L2025/03617 ,  H04L2025/03643 ,  H04L2025/03745

摘要： A method and a system for providing ISI compensation to an input signal in a bifurcated manner. ISI compensation is provided in two stages, a first stage compensates ISI components induced by characteristics of a transmitter's partial response pulse shaping filter, a second stage compensates ISI components induced by characteristics of a multi-pair transmission channel. First stage ISI compensation is performed in an inverse response filter having a characteristic feedback gain factor K, during system start-up. Second stage ISI compensation is performed by a single DFE in combination with a MDFE operating on tentative decisions output from a Viterbi decoder. As the DFE of the second stage reaches convergence, the feedback gain factor K of the first stage is ramped to zero.

摘要翻译： 一种用于以分叉方式向输入信号提供ISI补偿的方法和系统。 ISI补偿分两阶段提供，第一级补偿由发射机的部分响应脉冲整形滤波器的特性引起的ISI分量，第二级补偿由多对传输信道的特性引起的ISI分量。 在系统启动期间，在具有特性反馈增益因子K的逆响应滤波器中执行第一级ISI补偿。 第二级ISI补偿由单个DFE与由维特比解码器输出的暂定决定操作的MDFE组合执行。 当第二级的DFE达到收敛时，第一级的反馈增益因子K变为零。

公开(公告)号：US06249544B1

公开(公告)日：2001-06-19

申请号：US09370354

申请日：1999-08-09

申请人： Oscar E. Azazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

发明人： Oscar E. Azazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

IPC分类号： H03H730

CPC分类号： H04L7/0062 ,  G01R31/3004 ,  G01R31/3008 ,  G01R31/3016 ,  G01R31/31715 ,  G01R31/318502 ,  G01R31/318552 ,  G01R31/318594 ,  H03M13/256 ,  H03M13/41 ,  H04B3/23 ,  H04B3/32 ,  H04L1/0054 ,  H04L1/0059 ,  H04L1/242 ,  H04L7/0334 ,  H04L25/03038 ,  H04L25/03057 ,  H04L25/03146 ,  H04L25/03203 ,  H04L25/03267 ,  H04L25/03324 ,  H04L25/067 ,  H04L25/14 ,  H04L25/4917 ,  H04L25/497 ,  H04L2025/03363 ,  H04L2025/03369 ,  H04L2025/03458 ,  H04L2025/03477 ,  H04L2025/0349 ,  H04L2025/03496 ,  H04L2025/03503 ,  H04L2025/03617 ,  H04L2025/03643 ,  H04L2025/03745

摘要： A method and a system for providing ISI compensation to an input signal in a bifurcated manner. ISI compensation is provided in two stages, a first stage compensates ISI components induced by characteristics of a transmitter's partial response pulse shaping filter, a second stage compensates ISI components induced by characteristics of a multi-pair transmission channel. First stage ISI compensation is performed in an inverse response filter having a characteristic feedback gain factor K, during system start-up. Second stage ISI compensation is performed by a single DFE in combination with a MDFE operating on tentative decisions output from a Viterbi decoder. As the DFE of the second stage reaches convergence, the feedback gain factor K of the first stage is ramped to zero.

公开(公告)号：US20090067559A1

公开(公告)日：2009-03-12

申请号：US12269697

申请日：2008-11-12

申请人： Oscar E. Azazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

发明人： Oscar E. Azazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

IPC分类号： H04B1/10 ,  H03D1/06

CPC分类号： H04L7/0062 ,  G01R31/3004 ,  G01R31/3008 ,  G01R31/3016 ,  G01R31/31715 ,  G01R31/318502 ,  G01R31/318552 ,  G01R31/318594 ,  H03M13/256 ,  H03M13/41 ,  H04B3/23 ,  H04B3/32 ,  H04L1/0054 ,  H04L1/0059 ,  H04L1/242 ,  H04L7/0334 ,  H04L25/03038 ,  H04L25/03057 ,  H04L25/03146 ,  H04L25/03203 ,  H04L25/03267 ,  H04L25/03324 ,  H04L25/067 ,  H04L25/14 ,  H04L25/4917 ,  H04L25/497 ,  H04L2025/03363 ,  H04L2025/03369 ,  H04L2025/03458 ,  H04L2025/03477 ,  H04L2025/0349 ,  H04L2025/03496 ,  H04L2025/03503 ,  H04L2025/03617 ,  H04L2025/03643 ,  H04L2025/03745

摘要： A method and a system for providing ISI compensation to an input signal in a bifurcated manner. ISI compensation is provided in two stages, a first stage compensates ISI components induced by characteristics of a transmitter's partial response pulse shaping filter, a second stage compensates ISI components induced by characteristics of a multi-pair transmission channel. First stage ISI compensation is performed in an inverse response filter having a characteristic feedback gain factor K, during system start-up. Second stage ISI compensation is performed by a single DFE in combination with a MDFE operating on tentative decisions output from a Viterbi decoder. As the DFE of the second stage reaches convergence, the feedback gain factor K of the first stage is ramped to zero.

摘要翻译： 一种用于以分叉方式向输入信号提供ISI补偿的方法和系统。 ISI补偿分两阶段提供，第一级补偿由发射机的部分响应脉冲整形滤波器的特性引起的ISI分量，第二级补偿由多对传输信道的特性引起的ISI分量。 在系统启动期间，在具有特性反馈增益因子K的逆响应滤波器中执行第一级ISI补偿。 第二级ISI补偿由单个DFE与由维特比解码器输出的暂定决定操作的MDFE组合执行。 当第二级的DFE达到收敛时，第一级的反馈增益因子K变为零。

公开(公告)号：US06947482B2

公开(公告)日：2005-09-20

申请号：US09858760

申请日：2001-05-15

申请人： Oscar E. Azazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

发明人： Oscar E. Azazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

IPC分类号： G01R31/30 ,  G01R31/317 ,  G01R31/3185 ,  H04B3/23 ,  H04B3/32 ,  H04L1/00 ,  H04L1/24 ,  H04L7/02 ,  H04L7/033 ,  H04L25/03 ,  H04L25/06 ,  H04L25/14 ,  H04L25/49 ,  H04L25/497 ,  H03H7/30 ,  H03K5/159 ,  H04B1/38

CPC分类号： H04L7/0062 ,  G01R31/3004 ,  G01R31/3008 ,  G01R31/3016 ,  G01R31/31715 ,  G01R31/318502 ,  G01R31/318552 ,  G01R31/318594 ,  H03M13/256 ,  H03M13/41 ,  H04B3/23 ,  H04B3/32 ,  H04L1/0054 ,  H04L1/0059 ,  H04L1/242 ,  H04L7/0334 ,  H04L25/03038 ,  H04L25/03057 ,  H04L25/03146 ,  H04L25/03203 ,  H04L25/03267 ,  H04L25/03324 ,  H04L25/067 ,  H04L25/14 ,  H04L25/4917 ,  H04L25/497 ,  H04L2025/03363 ,  H04L2025/03369 ,  H04L2025/03458 ,  H04L2025/03477 ,  H04L2025/0349 ,  H04L2025/03496 ,  H04L2025/03503 ,  H04L2025/03617 ,  H04L2025/03643 ,  H04L2025/03745

摘要： A method and a system for providing ISI compensation to an input signal in a bifurcated manner. ISI compensation is provided in two stages, a first stage compensates ISI components induced by characteristics of a transmitter's partial response pulse shaping filter, a second stage compensates ISI components induced by characteristics of a multi-pair transmission channel. First stage ISI compensation is performed in an inverse response filter having a characteristic feedback gain factor K, during system start-up. Second stage ISI compensation is performed by a single DFE in combination with a MDFE operating on tentative decisions output from a Viterbi decoder. As the DFE of the second stage reaches convergence, the feedback gain factor K of the first stage is ramped to zero.

摘要翻译： 一种用于以分叉方式向输入信号提供ISI补偿的方法和系统。 ISI补偿分两阶段提供，第一级补偿由发射机的部分响应脉冲整形滤波器的特性引起的ISI分量，第二级补偿由多对传输信道的特性引起的ISI分量。 在系统启动期间，在具有特性反馈增益因子K的逆响应滤波器中执行第一级ISI补偿。 第二级ISI补偿由单个DFE与由维特比解码器输出的暂定决定操作的MDFE组合执行。 当第二级的DFE达到收敛时，第一级的反馈增益因子K变为零。

公开(公告)号：US08201045B2

公开(公告)日：2012-06-12

申请号：US12247064

申请日：2008-10-07

申请人： Oscar E. Agazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

发明人： Oscar E. Agazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

IPC分类号： H03M13/00

CPC分类号： H04L7/0062 ,  G01R31/3004 ,  G01R31/3008 ,  G01R31/3016 ,  G01R31/31715 ,  G01R31/318502 ,  G01R31/318552 ,  G01R31/318594 ,  H04B3/23 ,  H04B3/32 ,  H04L1/0054 ,  H04L1/0059 ,  H04L1/242 ,  H04L7/0334 ,  H04L25/03038 ,  H04L25/03057 ,  H04L25/03146 ,  H04L25/03267 ,  H04L25/067 ,  H04L25/14 ,  H04L25/4917 ,  H04L25/497 ,  H04L2025/03363 ,  H04L2025/03369 ,  H04L2025/03477 ,  H04L2025/0349 ,  H04L2025/03496 ,  H04L2025/03503 ,  H04L2025/03617 ,  H04L2025/03745

摘要： A method and a system for decoding information signals encoded in accordance with a multi-state encoding scheme and transmitted over a multi-dimensional transmission channel by computing a distance of a received word from a codeword. One-dimensional (1D) input signals are processed in a pair of symbol decoders, implemented as look-up tables, to produce a pair of 1D errors, with each representing a distance metric between the input signal and a symbol in one of two disjoint symbol-subsets. The 1D errors are combined based on the multi-state encoding scheme in order to produce a set of multi-dimensional error terms. Each of the multi-dimensional error terms corresponds to a distance between a received word and a nearest codeword.

摘要翻译： 一种用于对根据多状态编码方案编码并通过计算从码字的接收字的距离而在多维传输信道上传送的信息信号的方法和系统。 一维（1D）输入信号在一对符号解码器中被处理，被实现为查找表，以产生一对1D误差，其中每一个代表在两个不相交中的一个中的输入信号和符号之间的距离度量 符号子集。 基于多状态编码方案组合1D误差，以产生一组多维误差项。 多维误差项中的每一个对应于接收到的字和最近的码字之间的距离。

公开(公告)号：US07711077B2

公开(公告)日：2010-05-04

申请号：US12269697

申请日：2008-11-12

申请人： Oscar E. Agazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

发明人： Oscar E. Agazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

IPC分类号： H04B1/10 ,  H03D1/06

CPC分类号： H04L7/0062 ,  G01R31/3004 ,  G01R31/3008 ,  G01R31/3016 ,  G01R31/31715 ,  G01R31/318502 ,  G01R31/318552 ,  G01R31/318594 ,  H03M13/256 ,  H03M13/41 ,  H04B3/23 ,  H04B3/32 ,  H04L1/0054 ,  H04L1/0059 ,  H04L1/242 ,  H04L7/0334 ,  H04L25/03038 ,  H04L25/03057 ,  H04L25/03146 ,  H04L25/03203 ,  H04L25/03267 ,  H04L25/03324 ,  H04L25/067 ,  H04L25/14 ,  H04L25/4917 ,  H04L25/497 ,  H04L2025/03363 ,  H04L2025/03369 ,  H04L2025/03458 ,  H04L2025/03477 ,  H04L2025/0349 ,  H04L2025/03496 ,  H04L2025/03503 ,  H04L2025/03617 ,  H04L2025/03643 ,  H04L2025/03745

摘要： A method and a system for providing ISI compensation to an input signal in a bifurcated manner. ISI compensation is provided in two stages, a first stage compensates ISI components induced by characteristics of a transmitter's partial response pulse shaping filter, a second stage compensates ISI components induced by characteristics of a multi-pair transmission channel. First stage ISI compensation is performed in an inverse response filter having a characteristic feedback gain factor K, during system start-up. Second stage ISI compensation is performed by a single DFE in combination with a MDFE operating on tentative decisions output from a Viterbi decoder. As the DFE of the second stage reaches convergence, the feedback gain factor K of the first stage is ramped to zero.

摘要翻译： 一种用于以分叉方式向输入信号提供ISI补偿的方法和系统。 ISI补偿分两阶段提供，第一级补偿由发射机的部分响应脉冲整形滤波器的特性引起的ISI分量，第二级补偿由多对传输信道的特性引起的ISI分量。 在系统启动期间，在具有特性反馈增益因子K的逆响应滤波器中执行第一级ISI补偿。 第二级ISI补偿由单个DFE与由维特比解码器输出的暂定决定操作的MDFE组合执行。 当第二级的DFE达到收敛时，第一级的反馈增益因子K变为零。

公开(公告)号：US06226332B1

公开(公告)日：2001-05-01

申请号：US09370353

申请日：1999-08-09

申请人： Oscar E. Agazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

发明人： Oscar E. Agazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

IPC分类号： H04L2534

CPC分类号： H04L7/0062 ,  G01R31/3004 ,  G01R31/3008 ,  G01R31/3016 ,  G01R31/31715 ,  G01R31/318502 ,  G01R31/318552 ,  G01R31/318594 ,  H04B3/23 ,  H04B3/32 ,  H04L1/0047 ,  H04L1/0054 ,  H04L1/242 ,  H04L7/0334 ,  H04L25/03038 ,  H04L25/03057 ,  H04L25/03146 ,  H04L25/03267 ,  H04L25/03885 ,  H04L25/067 ,  H04L25/14 ,  H04L25/4917 ,  H04L25/497 ,  H04L2025/03363 ,  H04L2025/03369 ,  H04L2025/03477 ,  H04L2025/0349 ,  H04L2025/03496 ,  H04L2025/03503 ,  H04L2025/03617 ,  H04L2025/03745

摘要： A method and a system for decoding information signals encoded by a multi-state encoding architecture and transmitted over a multi-dimensional transmission channel by computing a distance of a received word from a codeword. One-dimensional (1D) input signals are detected in a symbol decoder, implemented using look-up tables, to produce a pair of 1D errors, with each representing a distance metric between the input signal and a symbol in one of two disjoint symbol-subsets. The symbol decoder is implemented as a pair of slicers, each detecting an input signal with respect to one of two disjoint symbol-subsets. A third slicer detects the input with respect to the union of the two disjoint symbol-subsets. Decisions from the first, second and third slicers are processed to define 1D square error terms expressed in Hamming metrics. Reduced bit count error terms allow follow-on error processing to be performed with a minimum of computational complexity. The 1D errors are combined to produce a set of multi-dimensional error terms. Each of the multi-dimensional error terms corresponds to a distance between a received word and a nearest codeword.

摘要翻译： 一种用于对由多状态编码架构编码的信息信号进行解码并通过计算从码字的接收字的距离而在多维传输信道上传输的方法和系统。 在使用查找表实现的符号解码器中检测一维（1D）输入信号，以产生一对1D误差，其中每一个代表在两个不相交符号的一个中的输入信号和符号之间的距离度量， 子集 符号解码器被实现为一对限幅器，每个限幅器相对于两个不相交符号子集之一检测输入信号。 第三个切片器检测相对于两个不相交符号子集合的输入。 处理来自第一，第二和第三限幅器的决策，以定义用Hamming度量表示的1D平方误差项。 减少位计数误差项允许以最小的计算复杂度执行后续的误差处理。 1D误差被组合以产生一组多维误差项。 多维误差项中的每一个对应于接收到的字和最近的码字之间的距离。

公开(公告)号：US20100135372A1

公开(公告)日：2010-06-03

申请号：US12698639

申请日：2010-02-02

申请人： Oscar E. Agazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

发明人： Oscar E. Agazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

IPC分类号： H04B1/38 ,  H04B1/10

CPC分类号： H04L7/0062 ,  G01R31/3004 ,  G01R31/3008 ,  G01R31/3016 ,  G01R31/31715 ,  G01R31/318502 ,  G01R31/318552 ,  G01R31/318594 ,  H04B3/23 ,  H04B3/32 ,  H04L1/0054 ,  H04L1/006 ,  H04L1/242 ,  H04L7/0334 ,  H04L25/03038 ,  H04L25/03057 ,  H04L25/03146 ,  H04L25/03267 ,  H04L25/067 ,  H04L25/14 ,  H04L25/4917 ,  H04L25/497 ,  H04L2025/03363 ,  H04L2025/03369 ,  H04L2025/03477 ,  H04L2025/0349 ,  H04L2025/03496 ,  H04L2025/03503 ,  H04L2025/03617 ,  H04L2025/03745

摘要： A feedforward equalizer for equalizing a sequence of signal samples received by a receiver from a remote transmitter. The feedforward equalizer has a gain and is included in the receiver which includes a timing recovery module for setting a sampling phase and a decoder. The feedforward equalizer comprises a non-adaptive filter and a gain stage. The non-adaptive filter receives the signal samples and produces a filtered signal. The gain stage adjusts the gain of the feedforward equalizer by adjusting the amplitude of the filtered signal. The amplitude of the filtered signal is adjusted so that it fits in the operational range of the decoder. The feedforward equalizer does not affect the sampling phase setting of the timing recovery module of the receiver.

摘要翻译： 前馈均衡器，用于均衡来自远程发射机的接收机接收的信号样本序列。 前馈均衡器具有增益并且被包括在接收机中，该接收机包括用于设置采样相位和解码器的定时恢复模块。 前馈均衡器包括非自适应滤波器和增益级。 非自适应滤波器接收信号样本并产生滤波信号。 增益级通过调整滤波信号的幅度来调节前馈均衡器的增益。 调整滤波后的信号的幅度使其适合于解码器的操作范围。 前馈均衡器不影响接收机的定时恢复模块的采样相位设置。

公开(公告)号：US07434134B2

公开(公告)日：2008-10-07

申请号：US10798675

申请日：2004-03-11

申请人： Oscar E. Agazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

发明人： Oscar E. Agazzi ,  David Kruse ,  Arthur Abnous ,  Mehdi Hatamian

IPC分类号： H03M13/00

CPC分类号： H04L7/0062 ,  G01R31/3004 ,  G01R31/3008 ,  G01R31/3016 ,  G01R31/31715 ,  G01R31/318502 ,  G01R31/318552 ,  G01R31/318594 ,  H04B3/23 ,  H04B3/32 ,  H04L1/0054 ,  H04L1/0059 ,  H04L1/242 ,  H04L7/0334 ,  H04L25/03038 ,  H04L25/03057 ,  H04L25/03146 ,  H04L25/03267 ,  H04L25/067 ,  H04L25/14 ,  H04L25/4917 ,  H04L25/497 ,  H04L2025/03363 ,  H04L2025/03369 ,  H04L2025/03477 ,  H04L2025/0349 ,  H04L2025/03496 ,  H04L2025/03503 ,  H04L2025/03617 ,  H04L2025/03745

摘要： A method and a system for decoding information signals encoded in accordance with a multi-state encoding scheme and transmitted over a multi-dimensional transmission channel by computing a distance of a received word from a codeword. One-dimensional (1D) input signals are processed in a pair of symbol decoders, implemented as look-up tables, to produce a pair of 1D errors, with each representing a distance metric between the input signal and a symbol in one of two disjoint symbol-subsets. The 1D errors are combined based on the multi-state encoding scheme in order to produce a set of multi-dimensional error terms. Each of the multi-dimensional error terms corresponds to a distance between a received word and a nearest codeword.

摘要翻译： 一种用于对根据多状态编码方案编码并通过计算从码字的接收字的距离而在多维传输信道上传送的信息信号的方法和系统。 一维（1D）输入信号在一对符号解码器中被处理，被实现为查找表，以产生一对1D误差，其中每一个代表在两个不相交中的一个中的输入信号和符号之间的距离度量 符号子集。 基于多状态编码方案组合1D误差，以产生一组多维误差项。 多维误差项中的每一个对应于接收到的字和最近的码字之间的距离。