Research Of TCM And Low-Density Parity-Check Codes

Channel Coding technology which can bring coding gain and save valuable power resource becomes a key technology in modern communication system. Firstly, every block diagram of the transmitter in TRECOMMENDATION V.34 is discussed in detail. The Viterbi decoder of the 4D-TCM in TRECOMMENDATION V.34 is researched; Secondly, this paper introduces the coding and decoding methods of LDPC code, presents the performance of both soft and hard decisions of (1008,3,6) regular LDPC code, analyzes the LLR-BP, Min-Sum and Offset BP-Based decoding algorithm performances of three QC-LDPC codes in GB20600-2006 standard; Thirdly, the density evolution theory is described, the process of density evolution is simplified by using gaussian approximation. This paper uses a simple method to get the detection threshold with the knowledge of probability, which can reduce considerable computation amount of decoding. The performance of improved algorithm and the original algorithm is compared, and the reason of computation amount reducing is analyzed.