LDPC (low density parity check) coded modulation symbol decoding

• US 7,849,389 B2
• Filed: 10/05/2006
• Issued: 12/07/2010
• Est. Priority Date: 06/13/2003
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Shen, Ba-Zhong, Tran, Hau Thien, Cameron, Kelly Brian
• Primary Examiner(s): Chase; Shelly A
• Application Number:
  US11/543,956
• Publication Number:
  US 20080065961A1
• Time in Patent Office: 1,524 Days
• Field of Search: 714800-801, 714/807
• US Class Current: 714/800
• CPC Class Codes: G11B 20/1833 by adding special lists or symbols to the coded information G11B20/1806, G11B20/1866 take precedence
• CPC Class Codes: H03M 13/1111 Soft-decision decoding, e.g. by means of message passing or belief propagation algorithms
• CPC Class Codes: H03M 13/1117 using approximations for check node processing, e.g. an outgoing message is depending on the signs and the minimum over the magnitudes of all incoming messages according to the min-sum rule
• CPC Class Codes: H03M 13/112 with correction functions for the min-sum rule, e.g. using an offset or a scaling factor
• CPC Class Codes: H03M 13/25 Error detection or forward error correction by signal space coding, i.e. adding redundancy in the signal constellation, e.g. Trellis Coded Modulation [TCM] modulation codes H03M13/31
• CPC Class Codes: H03M 13/255 with Low Density Parity Check [LDPC] codes
• CPC Class Codes: H03M 13/256 with trellis coding, e.g. with convolutional codes and TCM
• CPC Class Codes: H03M 13/258 with turbo codes, e.g. Turbo Trellis Coded Modulation [TTCM]
• CPC Class Codes: H03M 13/2957 Turbo codes and decoding
• CPC Class Codes: H03M 13/4161 implementing path management
• CPC Class Codes: H03M 13/45 Soft decoding, i.e. using symbol reliability information H03M13/41 takes precedence
• CPC Class Codes: H03M 13/6516 Support of multiple code parameters, e.g. generalized Reed-Solomon decoder for a variety of generator polynomials or Galois fields
• CPC Class Codes: H03M 13/6583 Normalization other than scaling, e.g. by subtraction
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/005 Iterative decoding, including iteration between signal detection and decoding operation
• CPC Class Codes: H04L 1/0058 Block-coded modulation
• CPC Class Codes: H04L 1/006 Trellis-coded modulation
• CPC Class Codes: H04L 1/1671 the supervisory signal being transmitted together with control information
• CPC Class Codes: H04L 27/18 Phase-modulated carrier systems, i.e. using phase-shift keying H04L27/32 takes precedence
• CPC Class Codes: H04L 27/2602 Signal structure

Abstract

LDPC (Low Density Parity Check) coded modulation symbol decoding. Symbol decoding is supported by appropriately modifying an LDPC tripartite graph to eliminate the bit nodes thereby generating an LDPC bipartite graph (such that symbol nodes are appropriately mapped directly to check nodes thereby obviating the bit nodes). The edges that communicatively couple the symbol nodes to the check nodes are labeled appropriately to support symbol decoding of the LDPC coded modulation signal. The iterative decoding processing may involve updating the check nodes as well as estimating the symbol sequence and updating the symbol nodes. In some embodiments, an alternative hybrid decoding approach may be performed such that a combination of bit level and symbol level decoding is performed. This LDPC symbol decoding out-performs bit decoding only. In addition, it provides comparable or better performance of bit decoding involving iterative updating of the associated metrics.

Claims

1. A decoder that is operable to decode an LDPC (Low Density Parity Check) coded signal, the decoder comprising:

a symbol sequence estimate and symbol node update block that is operable to employ an updated edge message to make an estimate of a symbol within the LDPC coded signal; and

wherein;

the edge message corresponds to an edge that connects a check node and a symbol node within an LDPC coded modulation bipartite graph.

2. The decoder of claim 1, further comprising:

a check node update block that is operable to generate the updated edge message corresponding to the edge that connects the check node and the symbol node within the LDPC coded modulation bipartite graph.

3. The decoder of claim 1, further comprising:

a check node update block that is operable to update the edge message corresponding to the edge that connects the check node and the symbol node within the LDPC coded modulation bipartite graph; and

wherein;

the check node update block is operable to employ min* (min-star) processing to generate the updated edge message.

4. The decoder of claim 1, further comprising:

a check node update block that is operable to calculate a plurality of forward metrics and a plurality of backward metrics that correspond to the symbol within the LDPC coded signal; and

wherein;

the check node update block that is operable to use the plurality of forward metrics and the plurality of backward metrics to update the edge message corresponding to the edge that connects the check node and the symbol node within the LDPC coded modulation bipartite graph.

5. The decoder of claim 1, wherein:

the symbol node corresponds to a plurality of bits within the LDPC coded signal.

6. The decoder of claim 1, wherein:

the symbol within the LDPC coded signal is a first symbol within the LDPC coded signal;

the first symbol within the LDPC coded signal includes a first plurality of bits; and

the second symbol within the LDPC coded signal includes a second plurality of bits.

7. The decoder of claim 1, wherein:

the symbol within the LDPC coded signal is a first symbol within the LDPC coded signal;

the first symbol within the LDPC coded signal is mapped to a first constellation whose constellation points are mapped according to a first mapping; and

a second symbol within the LDPC coded signal is mapped to a second constellation whose constellation points are mapped according to a second mapping.

8. The decoder of claim 1, wherein:

the symbol within the LDPC coded signal is a first symbol within the LDPC coded signal;

the first symbol within the LDPC coded signal is mapped to a constellation when its constellation points are mapped according to a first mapping; and

a second symbol within the LDPC coded signal is mapped to the constellation when its constellation points are mapped according to a second mapping.

9. The decoder of claim 1, wherein:

the symbol within the LDPC coded signal is a first symbol within the LDPC coded signal;

the first symbol within the LDPC coded signal has a first code rate; and

a second first symbol within the LDPC coded signal has a second code rate.

10. The decoder of claim 1, wherein:

the decoder is implemented within a communication device; and

the communication device is implemented within at least one of a satellite communication system, an HDTV (High Definition Television) communication system, a cellular communication system, a microwave communication system, a point-to-point communication system, a uni-directional communication system, a bi-directional communication system, a one to many communication system, a fiber-optic communication system, a WLAN (Wireless Local Area Network) communication system, and a DSL (Digital Subscriber Line) communication system.

11. A decoder that is operable to decode an LDPC (Low Density Parity Check) coded signal, the decoder comprising:

a check node update block that is operable to update an edge message corresponding to an edge that connects a check node and a symbol node within an LDPC coded modulation bipartite graph using min* (min-star) processing; and

a symbol sequence estimate and symbol node update block that is operable to;

receive the updated edge message from the check node update block; and

employ the updated edge message to make an estimate of a symbol within the LDPC coded signal.

12. The decoder of claim 11, wherein:

the symbol within the LDPC coded signal is a first symbol within the LDPC coded signal;

the first symbol within the LDPC coded signal includes a first plurality of bits; and

the second symbol within the LDPC coded signal includes a second plurality of bits.

13. The decoder of claim 11, wherein:

the symbol within the LDPC coded signal is a first symbol within the LDPC coded signal;

the first symbol within the LDPC coded signal is mapped to a first constellation whose constellation points are mapped according to a first mapping; and

a second symbol within the LDPC coded signal is mapped to a second constellation whose constellation points are mapped according to a second mapping.

14. The decoder of claim 11, wherein:

the symbol within the LDPC coded signal is a first symbol within the LDPC coded signal;

the first symbol within the LDPC coded signal is mapped to a constellation when its constellation points are mapped according to a first mapping; and

a second symbol within the LDPC coded signal is mapped to the constellation when its constellation points are mapped according to a second mapping.

15. The decoder of claim 11, wherein:

the symbol within the LDPC coded signal is a first symbol within the LDPC coded signal;

the first symbol within the LDPC coded signal has a first code rate; and

a second first symbol within the LDPC coded signal has a second code rate.

16. The decoder of claim 11, wherein:

the decoder is implemented within a communication device; and

the communication device is implemented within at least one of a satellite communication system, an HDTV (High Definition Television) communication system, a cellular communication system, a microwave communication system, a point-to-point communication system, a uni-directional communication system, a bi-directional communication system, a one to many communication system, a fiber-optic communication system, a WLAN (Wireless Local Area Network) communication system, and a DSL (Digital Subscriber Line) communication system.

17. A method for decoding an LDPC (Low Density Parity Check) coded signal, the method comprising:

receiving an updated edge message that corresponds to an edge that connects a check node and a symbol node within an LDPC coded modulation bipartite graph; and

employing the updated edge message to make an estimate of a symbol within the LDPC coded signal.

18. The method of claim 17, further comprising:

generating the updated edge message that corresponds to the edge that connects the check node and the symbol node within the LDPC coded modulation bipartite graph using min* (min-star) processing.

19. The method of claim 17, wherein:

the symbol within the LDPC coded signal is a first symbol within the LDPC coded signal;

the first symbol within the LDPC coded signal is mapped to a first constellation whose constellation points are mapped according to a first mapping; and

a second symbol within the LDPC coded signal is mapped to a second constellation whose constellation points are mapped according to a second mapping.

20. The method of claim 17, wherein:

the symbol within the LDPC coded signal is a first symbol within the LDPC coded signal;

the first symbol within the LDPC coded signal has a first code rate; and

a second first symbol within the LDPC coded signal has a second code rate.