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1、Department of Computer Science and Technology at Nanjing University2008.22008.6南京大学计算机科学与技术专业本科课程数 据 通 信 Data Communications杨献春 计算机软件新技术国家重点实验室（南京大学） State Key Laboratory for Novel Software Technology信号编码技术 Signal Encoding Techniques Title/subtitle/confidentiality line: 10pt Arial Regular, white Max
2、imum length: 1 lineInformation separated by vertical strokes, with two spaces on either side Copyright: 10pt Arial Regular, whiteDATA COMMUNICATIONSOptional slide number: 10pt Arial Bold, whiteSignal Encoding Techniques2008.22008.6信号编码技术数字-数字编码数字数据, 数字信号 数字-模拟编码（数字调制，D/A转换）数字数据, 模拟信号 模拟-数字编码（A/D转换）模
3、拟数据, 数字信号 模拟-模拟编码（模拟调制）模拟数据, 模拟信号2 Title/subtitle/confidentiality line: 10pt Arial Regular, white Maximum length: 1 lineInformation separated by vertical strokes, with two spaces on either side Copyright: 10pt Arial Regular, whiteDATA COMMUNICATIONSOptional slide number: 10pt Arial Bold, whiteSignal
4、 Encoding Techniques2008.22008.63 Title/subtitle/confidentiality line: 10pt Arial Regular, white Maximum length: 1 lineInformation separated by vertical strokes, with two spaces on either side Copyright: 10pt Arial Regular, whiteDATA COMMUNICATIONSOptional slide number: 10pt Arial Bold, whiteSignal
5、Encoding Techniques2008.22008.64.1 数字数据, 数字信号术语 编码方案不归零编码 (NRZ)多电平二进制双相位多态信号技术 调制速率 扰码4 Title/subtitle/confidentiality line: 10pt Arial Regular, white Maximum length: 1 lineInformation separated by vertical strokes, with two spaces on either side Copyright: 10pt Arial Regular, whiteDATA COMMUNICATIO
6、NSOptional slide number: 10pt Arial Bold, whiteSignal Encoding Techniques2008.22008.6术语术语单单极性 (unipolar) 所有信号单单元具有相同符号 双极性 (polar)正电压电压 表示一种逻辑逻辑 状态态负电压负电压 表示另一种 数据率 以每秒比特表示的数据信号传输传输 速率 比特持续时间续时间 或长长度 发发送器发发送出一个比特所需要的时间时间 调制速率 信号电平改变的速率以波特(baud)度量 每秒多少个信号单元5 Title/subtitle/confidentiality line: 10pt
7、Arial Regular, white Maximum length: 1 lineInformation separated by vertical strokes, with two spaces on either side Copyright: 10pt Arial Regular, whiteDATA COMMUNICATIONSOptional slide number: 10pt Arial Bold, whiteSignal Encoding Techniques2008.22008.66 Title/subtitle/confidentiality line: 10pt A
8、rial Regular, white Maximum length: 1 lineInformation separated by vertical strokes, with two spaces on either side Copyright: 10pt Arial Regular, whiteDATA COMMUNICATIONSOptional slide number: 10pt Arial Bold, whiteSignal Encoding Techniques2008.22008.6n再看图3.15 (噪声对一个数字信号的影响)接收器对对信号的解释释(1)7 Title/s
9、ubtitle/confidentiality line: 10pt Arial Regular, white Maximum length: 1 lineInformation separated by vertical strokes, with two spaces on either side Copyright: 10pt Arial Regular, whiteDATA COMMUNICATIONSOptional slide number: 10pt Arial Bold, whiteSignal Encoding Techniques2008.22008.6接收器对对信号的解释
10、释(2)需要知道 比特的定时关系 比特的起止时间 信号电平 (在比特持续时间中间位置采样) 决定成功解释信号的因素 带宽 （带宽增加，数据率增加） 数据率（数据率增加，BER增加） 信噪比 （S/N 或Eb/N0增加，误码率BER减少 ）编码方案8 Title/subtitle/confidentiality line: 10pt Arial Regular, white Maximum length: 1 lineInformation separated by vertical strokes, with two spaces on either side Copyright: 10pt
11、Arial Regular, whiteDATA COMMUNICATIONSOptional slide number: 10pt Arial Bold, whiteSignal Encoding Techniques2008.22008.6编码编码 方案不归零电平 (NRZ-L) 不归零1制(NRZI) 改进：mBnB如3B4B应用：5B6B(100BASE-FX和FDDI)，8B10B(1000BASE-?X和FC) 双极性交替传号翻转(AMI) 北美改进：双极性8零替换(B8ZS)扰码欧洲改进：高密度3零码双极性(HDB3)扰码应用：ISDN主速率（PRI速率） 伪三元码应用：ISDN
12、基本速率（BRI速率） MLT-3应用：100BASE-TX和CDDI 曼彻斯特应用：10BASE-T以太网（Ethernet） 差分曼彻斯特应用：令牌环（Token Ring） 8B6T应用：100BASE-T4 4D-PAM5应用：1000BASE-T9 Title/subtitle/confidentiality line: 10pt Arial Regular, white Maximum length: 1 lineInformation separated by vertical strokes, with two spaces on either side Copyright:
13、10pt Arial Regular, whiteDATA COMMUNICATIONSOptional slide number: 10pt Arial Bold, whiteSignal Encoding Techniques2008.22008.610 Title/subtitle/confidentiality line: 10pt Arial Regular, white Maximum length: 1 lineInformation separated by vertical strokes, with two spaces on either side Copyright:
14、10pt Arial Regular, whiteDATA COMMUNICATIONSOptional slide number: 10pt Arial Bold, whiteSignal Encoding Techniques2008.22008.6(cont.)11 Title/subtitle/confidentiality line: 10pt Arial Regular, white Maximum length: 1 lineInformation separated by vertical strokes, with two spaces on either side Copy
15、right: 10pt Arial Regular, whiteDATA COMMUNICATIONSOptional slide number: 10pt Arial Bold, whiteSignal Encoding Techniques2008.22008.6数字信号常见编码格式(码型)12 Title/subtitle/confidentiality line: 10pt Arial Regular, white Maximum length: 1 lineInformation separated by vertical strokes, with two spaces on ei
16、ther side Copyright: 10pt Arial Regular, whiteDATA COMMUNICATIONSOptional slide number: 10pt Arial Bold, whiteSignal Encoding Techniques2008.22008.6编码编码 方案的比较较 (1)信号频谱减少高频分量可节省传输所需带宽非直流成分可经变压器交流耦合提供电气隔离传输功率集中在传输带宽中心 时钟同步使发送器与接收器同步同步方式 外部时钟 基于发送信号的同步机制13 Title/subtitle/confidentiality line: 10pt Arial Regular, white Maximum length: 1 lineI
