1. Field of the Invention
The present invention relates to a technology of a low-density parity-check (LDPC) code for a transmission channel, particularly to a cyclic comparison method for an LDPC decoder.
2. Description of the Related Art
The low-density parity-check (LDPC) code is a promising and very useful encoding technology with highly complicated calculation. The Min-Sum algorithm thereof can greatly reduce the hardware complexity of a decoder. However, a little performance loss may occur in the operation thereof. Therefore, it is an important subject how to reduce operational complexity via the Min-Sum algorithm without the penalty of performance.
The operation of an LDPC decoder is an iterative process. Refer to
Accordingly, the present invention proposes a cyclic comparison method for an LDPC decoder to solve the abovementioned problems.
The primary objective of the present invention is to provide a cyclic comparison method for an LDPC decoder, wherein the cyclic comparison algorithm can be easily programmed, can approach the optimal solution and can accept any number of inputs in a low-density parity-check process.
Another objective of the present invention is to provide a cyclic comparison method for an LDPC decoder, wherein via the large set intersection between the compared level sequences, k input elements need only k×┌log2(k−1)┐ comparisons; thereby, the number of calculations can be reduced and the efficiency of the system is promoted.
Further another objective of the present invention is to provide a cyclic comparison method for an LDPC decoder, wherein when the number of the input elements is k, each element of the input elements is sequentially removed from the input elements to form k first level sequences, and each first level sequences has (k−1) elements; pairs of two elements selected from the k elements are used to form k level sequences, and pairs of two level sequences selected from the k level sequences are used to form a plurality of level sequences; the preceding step is repeated until obtaining k output results with each output results has (k−1) elements; the first level sequences and the output results are compared to determine whether they are identical; thereby, a fast comparison is achieved.
To achieve the abovementioned objectives, the present invention proposes a cyclic comparison method for an LDPC decoder, wherein k elements are input to a CNU for comparison. The cyclic comparison method for an LDPC decoder of the present invention comprises the following steps: (a) sequentially removing the elements respectively at from the first position to the kth position to obtain k first level sequences with each first level sequences having (k−1) elements, and outputting the first level sequences and the minimum value of each first level sequences; (b) utilizing pairs of two elements sequentially selected from the k elements input to the CNU to form k second level sequences, and utilizing pairs of two second level sequences sequentially selected from the k second level sequences to form k third level sequences; (c) utilizing pairs of two third level sequences selected from the k third level sequences to form a plurality level sequences, and repeating the step until obtaining k output results with each output results containing (k−1) elements; and (d) comparing the output results obtained in Step (c) and the first level sequences obtained in Step (a) to determine whether they are identical; if they are identical, stopping the process and outputting the minimum value of each output results; if they are not identical, doing Step (c) again to obtain new output results.
Below, the embodiments are to be described in detail to make the objectives, technical contents, characteristics and accomplishments of the present invention easily understood.
The present invention pertains to a cyclic comparison method for an LDPC decoder, which reduces the number of comparison operations via working out the largest common comparison set under the condition without changing the shortest critical path of the comparison operation, and which can also fast work out the result for any input number.
Refer to
The cyclic comparison method for an LDPC decoder of the present invention is applied to the CNU 14. K elements are input to the CNU for comparison. Refer to
After the abovementioned k outputs have been generated from the k elements input to the CNU, pairs of two elements sequentially selected from the k elements input to the CNU are used to form k second level sequences. When k=9, pairs of two elements sequentially selected from the first input 20 to the ninth input 20 are used to form 9 second level sequences in the first-level comparators 22, including Min{1,2}, Min{2,3}, Min{3,4}, Min{4,5}, Min{5,6}, Min{6,7}, Min{7,8}, Min{8,9}, and Min{9,1}. Next, pairs of two second level sequences sequentially selected from the 9 second level sequences are used to form 9 third level sequences in the second level comparators 24, including Min{9,1,2,3}, Min{1,2,3,4}, Min{2,3,4,5}, Min{3,4,5,6}, Min{4,5,6,7}, Min{5,6,7,8}, Min{6,7,8,9}, Min{7,8,9,1}, and Min{8,9,1,2}. Next, pairs of two third level sequences selected from the 9 third level sequences are used to form 9 output results, and each output results has 8 elements. Then, the output results are compared with the first level sequences output beforehand to determine whether they are identical; if they are identical, the process stops; if they are not identical, the preceding step repeats.
In the abovementioned steps, all the values of the elements of each level sequences are non-zero. The number of the elements of the second level sequences, the third level sequences or the succeeding level sequences is equal to 2 to the nth power, wherein n is the number of the combinations for the level sequences. Therefore, the output results must possess an even number of elements. At the same time, the output results are obtained via combining two third level sequences and repeating the step until obtaining the level sequences containing (k−1) elements. When the input number k is an even number, the lastly-output output results should have (k−1) elements, and (k−1) is an odd number, which conflicts with that the output results should possess an even number of elements. Therefore, when k is an even number, two third level sequences containing a repeated element are combined to obtain one output results having an odd number of elements. For example, when k=8, two third level sequences {2,3,4,5} and {5,6,7,8} are combined to form the output results {2,3,4,5,6,7,8}. In the present invention, the number of the required comparators is k×┌log2(k−1)┐, and the number of the levels of comparators is ┌log2(k−1)┐, i.e. the number of the combinations each output results has to pass through is ┌log2(k−1)┐.
In summary, the present invention proposes a cyclic comparison method for an LDPC decoder, wherein the cyclic comparison algorithm can be easily programmed, can approach the optimal solution and can accept any number of inputs in a low-density parity-check process. Further, via the large set intersection between the compared level sequences, k input elements need only k×┌log2(k−1)┐ comparisons; thereby, the number of calculations can be reduced, and the efficiency of the system is promoted.
Those described above are the preferred embodiments to exemplify the present invention. However, it is not intended to limit the scope of the present invention. Any equivalent modification or variation according to the spirit of the present invention is to be also included within the scope of the present invention.
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96108173 A | Mar 2007 | TW | national |
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