Multistage LDPC encoding

1. A system for performing low-density parity-check (LDPC) encoding, comprising:

a first encoder configured to encode input data using a first sub-matrix of a parity check matrix to obtain intermediate data, wherein:

the parity check matrix includes the first sub-matrix and a second sub-matrix having a matrix inversion;

the parity check matrix is an m×n matrix;

the first sub-matrix is an m×(n−m) matrix; and

the matrix inversion of the second sub-matrix is an m×m matrix; and

a second encoder configured to encode the intermediate data using the matrix inversion of the second sub-matrix of the parity check matrix.

2. The system of claim 1 , wherein the parity check matrix includes a quasi-cyclic low-density parity-check (QC-LDPC) parity check matrix.

3. The system of claim 1 , wherein the parity check matrix is a full rank matrix.

4. The system of claim 1 , wherein:

the second encoder is configured to encode the intermediate data by generating parity data; and

the system further includes a combiner configured to combine the parity data with the input data to obtain LDPC encoded data.

5. The system of claim 1 further comprising storage configured to store the encoded intermediate data generated by the first encoder.

6. The system of claim 1 further comprising a first buffer and a second buffer, wherein the first buffer is configured to store in the first buffer a first set of intermediate data received from the first encoder while simultaneously the second buffer is configured to pass a second set of intermediate data from the second buffer to the second encoder.

7. The system of claim 1 , wherein the first encoder is configured to:

divide up the input data into a plurality of portions; and

repeatedly use the first encoder to encode each of the plurality of portions.

8. A system for performing low-density parity-check (LDPC) encoding, comprising:

a first encoder configured to encode input data using a first sub-matrix of a parity check matrix to obtain intermediate data, wherein the parity check matrix includes the first sub-matrix and a second sub-matrix having a matrix inversion; and

a second encoder configured to encode the intermediate data using the matrix inversion of the second sub-matrix of the parity check matrix, wherein the second encoder is configured to:

divide up the intermediate data into a plurality of portions; and

repeatedly use the second encoder to encode each of the plurality of portions.

9. A method for performing low-density parity-check (LDPC) encoding, comprising:

using a first encoder to encode input data using a first sub-matrix of a parity check matrix to obtain intermediate data, wherein the parity check matrix includes the first sub-matrix and a second sub-matrix having a matrix inversion; and

using a second encoder to encode the intermediate data using the matrix inversion of the second sub-matrix of the parity check matrix, including by:

dividing up the intermediate data into a plurality of portions; and

repeatedly using the second encoder to encode each of the plurality of portions.

10. The method of claim 9 further comprising storing data encoded using the method recited in claim 9 in magnetic disk storage.

11. The method of claim 9 , wherein the parity check matrix includes a quasi-cyclic low-density parity-check (QC-LDPC) parity check matrix.

12. The method of claim 9 , wherein the parity check matrix is a full rank matrix.

13. The method of claim 9 , wherein:

using the second encoder includes generating parity data; and

the method further includes combining the parity data with the input data to obtain LDPC encoded data.

14. The method of claim 9 further comprising storing the encoded intermediate data generated by the first encoder.

15. The method of claim 9 further comprising using a first buffer to store a first set of intermediate data received from the first encoder and using a second buffer to simultaneously pass a second set of intermediate data from the second buffer to the second encoder.

16. The method of claim 9 , wherein using the first encoder includes:

dividing up the input data into a plurality of portions; and

repeatedly using the first encoder to encode each of the plurality of portions.

17. A method for performing low-density parity-check (LDPC) encoding, comprising:

using a first encoder to encode input data using a first sub-matrix of a parity check matrix to obtain intermediate data, wherein:

the parity check matrix includes the first sub-matrix and a second sub-matrix having a matrix inversion;

the parity check matrix is an m×n matrix;

the first sub-matrix is an m×(n−m) matrix; and

the matrix inversion of the second sub-matrix is an m×m matrix; and

using a second encoder to encode the intermediate data using the matrix inversion of the second sub-matrix of the parity check matrix.

18. A computer program product for performing low-density parity-check (LDPC) encoding, the computer program product being embodied in a non-transitory computer readable storage medium and comprising computer instructions for:

encoding input data using a first sub-matrix of a parity check matrix to obtain intermediate data, wherein:

the parity check matrix includes the first sub-matrix and a second sub-matrix having a matrix inversion;

the parity check matrix is an m×n matrix;

the first sub-matrix is an m×(n−m) matrix; and

the matrix inversion of the second sub-matrix is an m×m matrix; and

encoding the intermediate data using the matrix inversion of the second sub-matrix of the parity check matrix.

19. A computer program product for performing low-density parity-check (LDPC) encoding, the computer program product being embodied in a non-transitory computer readable storage medium and comprising computer instructions for:

encoding input data using a first sub-matrix of a parity check matrix to obtain intermediate data, wherein the parity check matrix includes the first sub-matrix and a second sub-matrix having a matrix inversion; and

encoding the intermediate data using the matrix inversion of the second sub-matrix of the parity check matrix, including by:

dividing up the intermediate data into a plurality of portions; and

repeatedly using the second encoder to encode each of the plurality of portions.