LDPC Decoding Algorithms Researches In Digital Television Transmitting Systems

Digital television is an industry which gets lots of attention and is developing at a high speed. LDPC codes had been chosen to be a part of the channel coding scheme in many digital television broadcasting standards. With the LDPC coding, these standards can make their systems more reliable and do more wireless multimedia services. So the researches about LDPC code have a significant value of widely practical application.In this paper, according to the standards of the three digital television broadcasting systems, CMMB, TMMB and DVB-S2, a deep research about the decoing algorithm and the scheme of hardware implementation of LDPC code has been done. The main jobs in this paper include these following aspects:1. To take the LDPC codes in three digital television standards as the research subjects, the respective different quasi-cyclic characteristics of these LDPC codes are obtained by theoretical analysising and structure simulation of the parity-check matrixces.2. Both the hard-decision algorithm and soft-decision algorithm of LDPC codes are researched deeply. Considering the multi-level mapping scheme in digital television standards, this paper proposed the algorithm of how to extract the confidence degree information of variable node from the received information. This algorithm makes up the deficiency of the analysis of LDPC decoding algorithm only used in BPSK mapping scheme in these literatures available.3. Taking the LDPC codes in CMMB system as example, numerous simulation have been done, with which the superiority-inferiority of different decoding algorithms were verified and the optimum parameters in the decoding algorithms were chosen; and at the same time, the decoding algorithm which is suitable for hardware implementation was indicated.4. Using the quasi-cyclic characteristics of these LDPC codes in the three standards and according to the decoding algorithm which was chosen previously, both the general decoder implementation scheme which was suitable for quasi-cyclic LDPC codes and the unit structure of the decoder were designed.