Method for constructing LDPC code in the mobile digital multimedia broadcast system

A method of constructing a LDPC code in a mobile digital multimedia broadcast system using a processor, wherein a Low-Density Parity-Check matrix of the LPDC code is iteratively constructed according to a code table and an expansion method, and the code-table is a part of the constructed Low-Density Parity-Check matrix, the method comprising the following steps:

• step 1:
• using the processor to set up a first cycle with a cycling index I with the I falls in the range of 1 to row number or column number of the code table, wherein the maximum value of the I is the row number of the code table if the code table is a part of rows of the constructed Low-Density Parity-Check matrix, and the maximum value of the I is the column number of the code table if the code table is a part of columns of the constructed Low-Density Parity-Check matrix;
• selecting data of Ith row or Ith column in the code table, if a representing format of the data sequence is not sparse, the data sequence is transformed into sparse format, and the data sequence in sparse format is marked by hexp, in which the data of the Ith row in the code table is selected if the code table is a part of rows of the constructed Low-Density Parity-Check matrix, and the data of the Ith column in the code table is selected if the code table is a part of columns of the constructed Low-Density Parity-Check matrix;
• step 2:
• using the processor to nest a second cycle with a cycling index J in the first cycle in which J is selected from the range of 1 to L;
• wherein it is supposed that the dimension of the Low-Density Parity-Check matrix of the LPDC code is M rows and N columns, and the Low-Density Parity-Check matrix with M rows and N columns can be divided into m×n blocks with each block having L×L elements, i.e., M=m×L and N=n×L;
• if the code table is a part of rows of the constructed Low-Density Parity-Check matrix and it is supposed that the data sequence hexp corresponds to the rth row of the Low-Density Parity-Check matrix with the r in the range of 1 to M, a variable “row” is calculated according to the following formula:
• row={[(J−1)×m+(r−I)]% M}+I,
• in which the symbol % denotes modular operation, and the row falls in the range of 1 to M;
• if the code table is a part of columns of the constructed Low-Density Parity-Check matrix and it is supposed that the data sequence hexp corresponds to the cth column of the Low-Density Parity-Check matrix with the c in the range of 1 to N, a variable “column” is calculated according to the following formula:
• column={[(J−1)×n+(c−I)]% N}+I,
• in which % denotes modular operation, and the “column” falls in the range of 1 to N;
• step 3:
• using the processor to nest a third cycle with a cycle index K in the variable “row” of the second cycle with the K in the range of 1 to W, and the Kth data of the data sequence hexp is marked by hexp (K), and
• if the code table is a part of rows of the constructed Low-Density Parity-Check matrix, the hexp (K) falls in the range of 0 to N−1, and the variable “column” is calculated according to the following formula:
• column=[(└hexp(K)/n┘+J−1)% L]×n+(hexp(K)% n)+1,
• in which └•┘ denotes floor rounding operation;
• if the code table is a part of columns of the constructed Low-Density Parity-Check matrix, the hexp (K) falls in the range of 0 to M−1, and the variable “row” is calculated according to the following formula:
• row=[(└hexp(K)/m┘+J−1)% L]×m+(hexp(K)% m)+1, and
• setting the element at the rowth row and columnth column of the Low-Density Parity-Check matrix to be a non-zero element.