第1章 Introduction of error coding_1.ppt

School of Electronic Information Engineering, Tianjin University Communication Theory and System 侯春萍 Email: hcp@tju.edu.cn Tel: 1392128837 Reference Book Digital Communication Fundamentals and Applications Bernard Sklar Publishing House of Electronics Industry （2004.1月） Modulation and Coding for Wireless Communications Aliser Burr Publishing House of Electronics Industry （2003.2） About the Class Introduction to Modulation and Coding Error Coding (BCH, Convolution codes, Turbo codes) Summary of Digital Modulations Trellis Coded Modulation (TCM) Modulation and Coding Trade-offs Two Parts Error Coding Technologies: Part 1 Introduction to error coding and decoding technologies Cyclic block codes（BCH , RS） Convolution codes Turbo codes Digital Modulation Technologies: Part 2 Summary of digital modulation technologies Trellis coded modulation (TCM) Modulation and coding trade-offs Chapter 1 Introduction of Error Control Coding Error coding technologies Error decoding technologies Why digital? 1.1 Error Coding Technologies 1.1.1 Types of Error Control 一、 Error Detection Retransmission Detection of Error ：using parity bit （奇偶校验比特） Correction of Error ：retransmission Requirement to system: Transmission in both directions Delay allowed Advantage：simple in the receiver Automatic Repeat Request (ARQ) 二、Forward Error-correction Coding Why Reducing bit error ratio (BER) Obtain coding gain How Adding into redundant bit Increasing Hamming distance 1.1.2 Code Rate and Redundancy Coder Information Bit ( k ) Code Bit ( n ) Redundant Bit, Parity Bit, Check Bit ( n-k) Code Rate ： k/n，information bits per a code bit。 Redundancy ：(n-k)/k，redundant bits per a information bit. 1.1.3 Why use error-correction coding? Trade-Off1：Error Performance versus Bandwidth Obtaining better error performance (from PB = 10-2 to PB = 10-4 ) uncoding: increasing power from A to B coding：increasing bandwidth from A to C poin