Based On Ldpc Cpm Serial Concatenated System

Coding and modulation is one of the most important part of the communication systems. It is the key element to improve the system performance.Continuous Phase Modulation (CPM) is a kind of constant-envelope digital modulation schemes which could provide better spectral utilization than PSK scheme. Due to the characteristic of continuous phase, CPM has the ability of error-control. It is shown that CPM system could be decomposed into a continuous phase encoder (CPE) and a memory-less modulator (MM). So CPM could use CPE as inner-code to cascade with other error-control codes to buildup concatenated error-control system.Low-Density Parity-Check Codes (LDPC) is a channel coding scheme which approaches the Shannon Limit. LDPC has the advantages of low decode complexity and low error-floor. Meanwhile, LDPC could be parallel calculated and suitable for hardware implementation. So it is a hot-point in channel coding domain in recent years.This thesis focused on the serially concatenated CPM system based on LDPC codes. This thesis introduced the characteristics of LDPC codes and Tanner graphics at first. Then described the methods of building check matrix and fast encoding algorithms, the Sum-product decoding algorithm has also been fully derived. After this, this thesis introduced the characteristic of CPM, derived the decomposed model and maximum likelihood decoding of CPM. Based on these theories, this thesis introduced the serially concatenated CPM systems based on LDPC codes. The system performance has been analyzed. More detailed analysis on parameters such as:code length, code rate, iterative time, iterative' scheme and interleave affection have also been studied. At last, an implementation scheme of coding and decoding of LDPC has been described.