Low Density Parity Check (Ldpc) Decoder

• US 20080104474A1
• Filed: 09/19/2005
• Published: 05/01/2008
• Est. Priority Date: 10/01/2004
• Status: Abandoned Application

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Joseph Laks
• Inventors: Gao, Wen, Ramaswamy, Kumar, Stewart, John Sidney
• Application Number:
  US11/662,565
• Publication Number:
  US 20080104474A1
• Time in Patent Office: Days
• US Class Current: 714/752
• CPC Class Codes: H03M 13/1105 Decoding
• CPC Class Codes: H03M 13/1111 Soft-decision decoding, e.g. by means of message passing or belief propagation algorithms
• CPC Class Codes: H03M 13/1137 Partly parallel processing, i.e. sub-blocks or sub-groups of nodes being processed in parallel
• CPC Class Codes: H03M 13/1165 QC-LDPC codes as defined for the digital video broadcasting [DVB] specifications, e.g. DVB-Satellite [DVB-S2]
• CPC Class Codes: H03M 13/1168 wherein the sub-matrices have column and row weights greater than one, e.g. multi-diagonal sub-matrices
• CPC Class Codes: H03M 13/1185 wherein the parity-check matrix comprises a part with a double-diagonal
• CPC Class Codes: H03M 13/616 Matrix operations, especially for generator matrices or check matrices, e.g. column or row permutations

Abstract

A satellite receiver comprises a front-end, demodulator and an LDPC decoder. The front-end receives a DVB-S2 LDPC coded signal and provides a down-converted signal to the demodulator. The latter demodulates the down-converted signal and provides a demodulated signal to the LDPC decoder. The LDPC decoder has a partially parallel architecture and partitions the bit node messages into N/360 groups and the check node messages into q groups, where q=M/360. Each group is processed by 360 bit node processors or 360 check node processors, respectively. Illustratively, the LDPC decoder includes a memory that is partitioned such that messages associated with bit node groups are consecutively addressed. Alternatively, the LDPC decoder includes a memory that is partitioned such that messages associated with check node groups are consecutively addressed.

Claims

1. A method for use in a receiver, the method comprising:

receiving low density parity check (LDPC) encoded data; and

processing the received LDPC encoded data using check node messages and bit node messages to provide decoded data;

wherein the processing step manipulates a parity check matrix such that there are Y groups of bit nodes and q groups of check nodes, where q varies as a function of a code rate associated with the received LDPC encoded data.

2. The method of claim 1, wherein the received LDPC encoded data is derived from a received digital video broadcasting system-2 signal.

3. The method of claim 1, wherein the received LDPC encoded data is representative of an (N, K) LDPC code, where M=N−

K, and q=Y (N−

K)/N.

4. The method of claim 3, wherein Y=N/360.

5. The method of claim 1, wherein the received LDPC encoded data is representative of an (N, K) LDPC code having a parity matrix of dimensions M×

N, and wherein the processing step includes;

processing each group of check node messages with J processors; and

processing each group of bit node messages with J processors;

wherein J represents dimensions of a square sub-matrix, such that an integral number of square sub-matrices fit into the parity matrix.

6. The method of claim 5, wherein the processing the check node messages step includes the steps of:

cyclically shifting each group of check node messages;

processing each cyclically shifted group of check node message with J processors to provide a group of new messages; and

cyclically shifting each group of new messages to form a group of bit node messages.

7. The method of claim 5, wherein the processing the bit node messages step includes the steps of:

cyclically shifting each group of bit node messages;

processing each cyclically shifted group of bit node message with J processors to provide a group of new messages; and

cyclically shifting each group of new messages to form a group of check node messages.

8. The method of claim 1, wherein the received LDPC encoded data is representative of an (N, K) LDPC code having a parity matrix of dimensions M×

N, and wherein the processing step includes;

processing each group of check node messages with J processors; and

processing each group of bit node messages with J processors;

wherein J=N/Y.

9. The method of claim 8, wherein the processing the check node messages step includes the steps of:

cyclically shifting each group of check node messages;

processing each cyclically shifted group of check node message with J processors to provide a group of new messages; and

cyclically shifting each group of new messages to form a group of bit node messages.

10. The method of claim 8, wherein the processing the bit node messages step includes the steps of:

cyclically shifting each group of bit node messages;

processing each cyclically shifted group of bit node message with J processors to provide a group of new messages; and

cyclically shifting each group of new messages to form a group of check node messages.

11. Apparatus for use in a receiver, the apparatus comprising:

a demodulator for providing low density parity check (LDPC) encoded data;

an LDPC decoder for decoding the LDPC encoded data to provide decoded data;

wherein the LDPC decoder processes the LDPC encoded data by partitioning bit node messages into Y groups and check node messages into q groups, where q varies as a function of a code rate associated with the LDPC encoded data.

12. The apparatus of claim 11, wherein the LDPC encoded data is derived from a received digital video broadcasting system-2 signal.

13. The apparatus of claim 11, wherein the LDPC encoded data is representative of an (N, K) LDPC code, where M=N−

K, and q=Y (N−

K)/N.

14. The apparatus of claim 13, wherein Y=N/360.

15. The apparatus of claim 11, wherein the LDPC encoded data is representative of an (N, K) LDPC code having a parity matrix of dimensions M×

N, and wherein the LDPC encoder comprises;

J processors for processing each group of bit node messages; and

J processors for processing each group of check node messages;

wherein J represents dimensions of a square sub-matrix, such that an integral number of square sub-matrices fit into the parity matrix.

16. The apparatus of claim 11, wherein the LDPC encoded data is representative of an (N, K) LDPC code having a parity matrix of dimensions M×

N, and wherein the LDPC encoder comprises;

J processors for processing each group of bit node messages; and

J processors for processing each group of check node messages;

wherein J=N/Y.

17. The apparatus of claim 11, wherein the LDPC decoder comprises:

a memory for storing the check node messages and the bit node messages; and

cyclic shifter for shifting the check node messages;

a group of bit node processors for processing the cyclically shifted check node messages to provide new messages;

a cyclic shifter for shifting the new messages to form new bit node messages;

a group of check node processors for processing the bit node messages to provide new check node messages for storage in the memory,

wherein the memory is structured such that new bit node messages are stored consecutively.

18. The apparatus of claim 11, wherein the LDPC decoder comprises:

a memory for storing the check node messages and the bit node messages; and

a group of bit node processors for processing the check node messages to provide new bit node messages for storage in the memory; and

a cyclic shifter for shifting the bit node messages;

a group of check node processors for processing the cyclically shifted bit node messages to provide new messages; and

a cyclic shifter for shifting the new messages to form new check node messages;

wherein the memory is structured such that new check node messages are stored consecutively.

19. The apparatus of claim 11, wherein the LDPC decoder comprises a memory organized such that groups of bit node messages are stored consecutively.

20. The apparatus of claim 11, wherein the LDPC decoder comprises a memory organized such that groups of check node messages are stored consecutively.