LDPC (Low Density Parity Check) encoding method based on FPGA (Field Programmable Gate Array) and used in CMMB (China Mobile Multimedia Broadcasting) exciter

Abstract

The invention discloses an LDPC (Low Density Parity Check) encoding method based on FPGA (Field Programmable Gate Array) and used in CMMB (China Mobile Multimedia Broadcasting) exciter. The method comprises the following steps: firstly, processing a verification matrix H of an LDPC system code on an MATLAB (Matrix Laboratory) platform, so as to generate verification matrixes Hp and Hs which correspond to a verification bit column vector P and an information bit column vector S; carrying out LU (Logical Unit) decomposition to the verification matrixes so as to obtain a lower triangular matrix L and an upper triangular matrix U; and realizing the LDPC encoding on the FPGA platform, which mainly involves the storage of a large matrix, matrix multiplication, forward iteration and backward iteration. According to the encoding method, an encoding mode based on a LU decomposition verification matrix is adopted; the logic calculation that large matrixes are multiplied is avoided; and the problem of large requirement on FPGA internal storage resource caused by large data quantity storage is solved, thereby simplifying the logic calculation operation, saving the storage space, and being beneficial for the realization of the LDPC encoding of the CMMB system.

Description

technical field [0001] The invention is aimed at the LDPC coding in the CMMB standard, and the coding method used is also applicable to the LDPC coding based on a large sparse parity check matrix. Background technique [0002] LDPC (Low Density Parity Check Codes, Low Density Parity Check Codes) has attracted much attention for its excellent error correction performance and low decoding complexity, and has been widely used in communication and digital broadcasting and other fields. One of the main problems faced by LDPC coding is its high coding complexity and coding delay. How to choose a suitable algorithm to achieve a balance between resources and efficiency is the main difficulty in hardware implementation of LDPC encoding. [0003] Description of the LDPC encoding module in the CMMB standard: [0004] The input information bit string vector S and check bit string vector P are rearranged to obtain the LDPC output codeword. [0005] C ...

AI Technical Summary

Problems solved by technology

Therefore, one of the main problems faced by LDPC codes is its high coding complexity and coding delay.

[0046] In the CMMB system, each row of the G matrix obtained by the above method has more than 1000 elements equal to 1, which will result in too much storage required and too high encoding complexity, making it unrealistic to implement

[0047] (2) Two matrix-vector multiplications in the general coding method of linear block codes. In the first multiplication, B is a sparse matrix. The multiplication of a sparse matrix and a vector is linear complexity, but in the second multiplication A -1 It is no longer a sparse matrix, so it is no longer linear complexity when multiplying vectors

The disadvantage of this algorithm is that the general H matrix does not have an approximate lower triangular structure, and the H matrix must be rearranged first, but when rearranging, it is difficult to ensure the form of the H matrix system code, and the transformed The submatrix T of the H matrix is ​​reversible, so it has certain limitations

[0049] To sum up, the main problems faced by the LDPC coding of the CMMB standard are its large parity check matrix, high coding complexity and long coding delay.

Images