第三章 语音及信道编解码技术
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Chapter 3
Chapter3 Source Coding and Ch l C di Channel Coding
Outline (目录)
Outline(
p g gy
3.1 Speech Coding technology
(语音编解码技术)
3.2 Overview of Code Design
(码设计概述)
3.3 Convolutional Codes ((卷积码)
3.4 Interleaving for Fading Channels
(衰落信道中的交织)
3.5 Turbo Codes （Turbo码）
35T b C d T b
Outline(目录)
3.1 Source Coding technology
3.2 Overview of Code Design
32Overview of Code Design
3.3 Convolutional Codes
3.4 Interleaving for Fading Channels 3.5 Turbo Codes
3.1.1Characteristics of speech coding technology 3.1.1 Characteristics of speech coding technology
Speech coding technology can compress the information using the speech signal and the redundancy of the human auditory characteristic, and is a kind of compressed redundancy technology. 语音编码技术利用语音信号和人类听觉特性的冗余性对信息进行压缩，是一种压用语音信号和人类听觉特性的冗余性对信息进行压缩，是种压缩冗余性技术。
The aim is to use less channel capacity and send more speech signal at th i f k i t i t ti l l it d
the premise of keeping certain computational complexity and communication delay. 目的是在保持一定算法复杂度和通信时延的前提下，利用尽可能少的信道容量，传送质量尽可能高的语音。 The objective reason of compressible for the speech signal is that there is huge redundancy in itself. 语音信号本身存在很大的冗余，是语音可压缩的外因
音可压缩的外因。 The subjective reason of compressible for speech signal is the human
auditory sensing mechanism. 人耳的听觉感知机理，语音可压缩的y g 内因。
3.1.1Characteristics of speech coding technology 3.1.1 Characteristics of speech coding technology
The Redundancy of voice signal can be described in the time domain and frequency domain
The Redundancy of voice signal in the time domain shows in the following aspects
▪The amplitude of voice signal obey the non-uniform distribution.语音信号的幅度表现为非均匀分布
信号的幅度表现为非均匀分布。▪The correlation between signal samples. 语音信号样本间的相关性。当取样频率为8kHz 时，相邻取样值间的相关系数大于0.85；甚至个样本之间还可有左右的数量级
在相距10个样本之间，还可有0.3左右的数量级。▪The correlation between speech signal cycles.语音信号周期之间的相关。在特定的瞬间，某一声音却往往只是该频带内的少数频率成关。在特定的瞬间，某声音却往往只是该频带内的少数频率成分在起作用。当声音中只存在少数几个频率时，就会像某些振荡波形一样，在周期与周期之间，存在着一定的相关性。
3.1.1Characteristics of speech coding technology 3.1.1 Characteristics of speech coding technology
Correlation between the pitch of the voice signal.语音信号基音之间的相关。语音可以分为清音和浊音两种基本类型。浊音是由声带振动产生，每一次振动使一股空气从肺部流进声道激励声道的各股空气之间的间隔称为基音周期进声道。激励声道的各股空气之间的间隔称为基音周期。 Static coefficient. According to the analysis , Voice clearance full duplex telephone channels efficiency is makes full-duplex telephone channels typical efficiency is about 40%.(the static coefficient is 0.6).静止系数。通过分析表明，话音间隙使得全双工话路的典型效率约为通话时间的40%（静止系数为0.6）。
Long time correlation function. 长时间相关函数。