Variable modulation with LDPC (low density parity check) coding

• US 8,683,288 B2
• Filed: 06/29/2012
• Issued: 03/25/2014
• Est. Priority Date: 05/31/2002
• Status: Active Grant

• 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): LAMARRE, GUY J
• Application Number:
  US13/537,170
• Publication Number:
  US 20120272118A1
• Time in Patent Office: 634 Days
• Field of Search: 714/755, 714/786, 714/774, 714/790
• US Class Current: 714/755
• CPC Class Codes: G11B 20/18 Error detection or correction; Testing , e.g. of drop-outs
• 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 13/11 using multiple parity bits
• CPC Class Codes: H03M 13/1102 Codes on graphs and decoding on graphs, e.g. low-density parity check [LDPC] codes
• CPC Class Codes: H03M 13/1105 Decoding
• 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 13/27 using interleaving techniques
• CPC Class Codes: H03M 13/2767 Interleaver wherein the permutation pattern or a portion thereof is stored
• CPC Class Codes: H03M 13/2771 Internal interleaver for turbo codes H03M13/2714 and H03M13/2725 take precedence
• CPC Class Codes: H03M 13/2785 Interleaver using in-place interleaving, i.e. writing to and reading from the memory is performed at the same memory location
• CPC Class Codes: H03M 13/2957 Turbo codes and decoding
• CPC Class Codes: H03M 13/4123 implementing the return to a predetermined state
• 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 13/6362 by puncturing
• CPC Class Codes: H03M 13/6561 Parallelized implementations
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0045 : Arrangements at the receiver 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 1/0066 : Parallel concatenated codes
• CPC Class Codes: H04L 1/0068 : by puncturing
• CPC Class Codes: H04L 1/0071 : Use of interleaving interleaving per se H03M13/27
• 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

Variable modulation within combined LDPC (Low Density Parity Check) coding and modulation coding systems. Variable modulation encoding of LDPC coded symbols is presented. In addition, LDPC encoding, that generates an LDPC variable code rate signal, may also be performed as well. The encoding can generate an LDPC variable code rate and/or modulation signal whose code rate and/or modulation may vary as frequently as on a symbol by symbol basis. Some embodiments employ a common constellation shape for all of the symbols of the signal sequence, yet individual symbols may be mapped according different mappings of the commonly shaped constellation; such an embodiment may be viewed as generating a LDPC variable mapped signal. In general, any one or more of the code rate, constellation shape, or mapping of the individual symbols of a signal sequence may vary as frequently as on a symbol by symbol basis.

Claims

1. An apparatus comprising:

an input configured to receive a low density parity check (LDPC) coded signal;

a metric computer configured to;

calculate a first plurality of symbol metrics of a first symbol of the LDPC coded signal having a first modulation including a first constellation having a first mapping of constellation points therein; and

calculate a second plurality of symbol metrics of a second symbol of the LDPC coded signal having a second modulation including a second constellation having a second mapping of constellation points therein;

a symbol node calculator configured to;

calculate a first plurality of bit metrics based on the first plurality of symbol metrics; and

calculate a second plurality of bit metrics based on the second plurality of symbol metrics; and

an LDPC decoder configured to decode the LDPC coded signal to make a first at least one estimate of a first plurality of bits of the first symbol of the LDPC coded signal and a second at least one estimate of a second plurality of bits of the second symbol of the LDPC coded signal based on the first plurality of bit metrics and the second plurality of bit metrics, respectively, wherein the apparatus operative within at least one of a satellite communication system, a wireless communication system, a wired communication system, and a fiber-optic communication system.

2. The apparatus of claim 1, wherein:

first plurality of bits including a same number of bits as the second plurality of bits;

the first constellation having a same number of constellation points as the second constellation; and

the constellation points of the first constellation having a same shape or arrangement as constellation points of the second constellation.

3. The apparatus of claim 2, wherein the first mapping of constellation points being same as the second mapping of constellation points.

4. The apparatus of claim 1, wherein the LDPC coded signal including at least one uncoded bit;

and further comprising;

the LDPC decoder configured to employ the at least one uncoded bit to make at least one of the first at least one estimate of the first plurality of bits of the first symbol of the LDPC coded signal and the second at least one estimate of the second plurality of bits of the second symbol of the LDPC coded signal.

5. The apparatus of claim 1, wherein the first modulation being quadrature phase shift key (QPSK) and having 4 constellation points therein, and the second modulation being 16 quadrature amplitude modulation (QAM) and having 16 constellation points therein.

6. An apparatus comprising:

an input configured to receive a low density parity check (LDPC) coded signal;

a metric computer configured to;

calculate a first plurality of symbol metrics of a first symbol of the LDPC coded signal having a first modulation including a first constellation having a first mapping of constellation points therein; and

calculate a second plurality of symbol metrics of a second symbol of the LDPC coded signal having a second modulation including a second constellation having a second mapping of constellation points therein; and

an LDPC decoder configured to decode the LDPC coded signal to make a first at least one estimate of a first plurality of bits of the first symbol of the LDPC coded signal and a second at least one estimate of a second plurality of bits of the second symbol of the LDPC coded signal based on a first plurality of bit metrics corresponding to the first plurality of symbol metrics and a second plurality of bit metrics corresponding to the second plurality of symbol metrics, respectively.

7. The apparatus of claim 6 further comprising:

a symbol node calculator configured to;

calculate the first plurality of bit metrics based on the first plurality of symbol metrics; and

calculate the second plurality of bit metrics based on the second plurality of symbol metrics.

8. The apparatus of claim 6, wherein:

the first plurality of bits including a same number of bits as the second plurality of bits;

the first constellation having a same number of constellation points as the second constellation; and

the constellation points of the first constellation having a same shape or arrangement as constellation points of the second constellation.

9. The apparatus of claim 8, wherein the first mapping of constellation points being same as the second mapping of constellation points.

10. The apparatus of claim 6, wherein the LDPC coded signal including at least one uncoded bit, and the LDPC decoder to employ the at least one uncoded bit to make at least one of the first at least one estimate of the first plurality of bits of the first symbol of the LDPC coded signal and the second at least one estimate of the second plurality of bits of the second symbol of the LDPC coded signal.

11. The apparatus of claim 6, wherein the first modulation being quadrature phase shift key (QPSK) and having 4 constellation points therein, and the second modulation being 16 quadrature amplitude modulation (QAM) and having 16 constellation points therein.

12. The apparatus of claim 6 further comprising:

a set top box (STB) receiver communicatively coupled to a display operative to display or output a decoded version of the LDPC coded signal.

13. The apparatus of claim 6 further comprising:

a communication device that is operative within at least one of a satellite communication system, a wireless communication system, a wired communication system, and a fiber-optic communication system.

14. A method for execution by a communication device, the method comprising:

via an input of the communication device, receiving a low density parity check (LDPC) coded signal;

calculating a first plurality of symbol metrics of a first symbol of the LDPC coded signal having a first modulation including a first constellation having a first mapping of constellation points therein;

calculating a second plurality of symbol metrics of a second symbol of the LDPC coded signal having a second modulation including a second constellation having a second mapping of constellation points therein; and

decoding the LDPC coded signal to make a first at least one estimate of a first plurality of bits of the first symbol of the LDPC coded signal and a second at least one estimate of a second plurality of bits of the second symbol of the LDPC coded signal based on a first plurality of bit metrics corresponding to the first plurality of symbol metrics and a second plurality of bit metrics corresponding to the second plurality of symbol metrics, respectively.

15. The method of claim 14 further comprising:

calculating the first plurality of bit metrics based on the first plurality of symbol metrics; and

calculating the second plurality of bit metrics based on the second plurality of symbol metrics.

16. The method of claim 14, wherein:

the first plurality of bits including a same number of bits as the second plurality of bits;

the first constellation having a same number of constellation points as the second constellation; and

the constellation points of the first constellation having a same shape or arrangement as constellation points of the second constellation.

17. The method of claim 16, wherein the first mapping of constellation points being same as the second mapping of constellation points.

18. The method of claim 14, wherein the LDPC coded signal including at least one uncoded bit;

and further comprising;

employing the at least one uncoded bit to make at least one of the first at least one estimate of the first plurality of bits of the first symbol of the LDPC coded signal and the second at least one estimate of the second plurality of bits of the second symbol of the LDPC coded signal.

19. The method of claim 14, wherein the first modulation being quadrature phase shift key (QPSK) and having 4 constellation points therein, and the second modulation being 16 quadrature amplitude modulation (QAM) and having 16 constellation points therein.

20. The method of claim 14, wherein the communication device is operative within at least one of a satellite communication system, a wireless communication system, a wired communication system, and a fiber-optic communication system.