Research On LDPC And TCM Coded In Modulation

The ultimate objective of the digital communication technology is reliable information transmission in the system permission maximum speed (channel capacity). One of these goal ways is the channel coding technology. The low density parity check (LDPC) codes are the most one popular research direction in the present information field and correspondence. LDPC codes are error correction codes which the performance has approaches Shannon limits and the greatly strengthened error correction and error detection ability. The decoding order of complexity is low and it is easy to realize the channel coding plan. One kind of special codes in the LDPC codes--circulates LDPC (Quasi-Cyclic LDPC, QC-LDPC) are a kind of very important LDPC codes, which have the low complexity codes and the low error code platform.High data rate with favorable communication quality should be provided in modern communication services. But it is a challenge for limited bandwidth and disturbance channel. It is a challenging topic to this problem. The grid coded modulation (Trellis Coded Modulation, TCM) will correct error codes and modulates as a whole to design, which not only has the high error correction ability but also has the very high band width use factor.This thesis takes the LDPC code as the research core. The important is to construct the simulation system of LDPC codes and TCM. We simulate and analysis the LDPC codes and TCM and study the system's performance.Firstly this thesis analyzes the basic principle and the structure methods of the LDPC codes. Then we research the LDPC codes based on the Euclidean space finite geometry. To obtain quasi-cyclic structure of the LDPC codes, we decomposed ranks of LDPC codes. This thesis measure the performance of LDPC codes through the code rate, iterative number of times as well as compare LDPC codes to other structure codes.Then this thesis studied the encoding and decoding methods of LDPC codes. Because the generator matrix has quasi-cycle characteristic, this thesis discussed two kinds of feedback shift register encoding algorithm--serial entering and parallel out encoding algorithm and parallel entering and serial out encoding algorithm in the encoding aspect of QC-LDPC. Then this thesis introduced probability sum-product decoding, log-domain sum-product decoding and min-sum decoding and construct to the different decoding algorithms' performance.Finally this thesis studied and realized the system program of LDPC codes combined with TCM. Then this thesis analyzed the TCM basic principle and discussed the application of TCM in the actual modulation system and analyzed the systems' performance of TCM-8PSK and TCM-16QAM. Finally the simulation system of LDPC codes combined with TCM is constructed and the corresponding simulation result is obtained.