Iteractive decoder employing multiple external code error checks to lower the error floor

• US 6,810,502 B2
• Filed: 05/25/2001
• Issued: 10/26/2004
• Est. Priority Date: 01/28/2000
• Status: Expired due to Term

• Current Assignee: MaxLinear Communications, LLC (f/k/a Entropic Communications, LLC) (Maxlinear Incorporated)
• Original Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Inventors: Eidson, Donald Brian, Krieger, Abraham, Murali, Ramaswamy
• Primary Examiner(s): Ton, David
• Application Number:
  US09/865,958
• Publication Number:
  US 20010025358A1
• Time in Patent Office: 1,250 Days
• Field of Search: 371/43, 714/755, 714/786, 714/780, 714/795, 714/758, 714/792, 375/136, 375/341
• US Class Current: 714/786
• CPC Class Codes: H03M 13/09 Error detection only, e.g. using cyclic redundancy check [CRC] codes or single parity bit
• CPC Class Codes: H03M 13/15 Cyclic codes, i.e. cyclic shifts of codewords produce other codewords, e.g. codes defined by a generator polynomial, Bose-Chaudhuri-Hocquenghem [BCH] codes H03M13/17 takes precedence
• CPC Class Codes: H03M 13/2936 comprising an outer Reed-Solomon code and an inner convolutional code
• CPC Class Codes: H03M 13/2948 Iterative decoding H03M13/2957 takes precedence
• CPC Class Codes: H03M 13/2972 Serial concatenation using convolutional component codes
• CPC Class Codes: H03M 13/3776 using a re-encoding step during the decoding process
• CPC Class Codes: H03M 13/3994 using state pinning or decision forcing, i.e. the decoded sequence is forced through a particular trellis state or a particular set of trellis states or a particular decoded symbol
• CPC Class Codes: H04L 1/005 Iterative decoding, including iteration between signal detection and decoding operation
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0066 Parallel concatenated codes

Abstract

Iterative decoder employing multiple external code error checks to lower the error floor and/or improve decoding performance. Data block redundancy, sometimes via a cyclic redundancy check (CRC) or Reed Solomon (RS) code, enables enhanced iterative decoding performance. Improved decoding performance is achieved during interim iterations before the final iteration. A correctly decoded CRC block, indicating a decoded segment is correct with a high degree of certainty, assigns a very high confidence level to the bits in this segment and is fed back to inner and/or outer decoders (with interleaving, when appropriate) for improved iterative decoding. High confidence bits may be scattered throughout inner decoded frames to influence other bit decisions in subsequent iterations. Turbo decoders typically operate relatively well at regions where the BER is high; the invention improves iterative decoder operation at lower BERs, lowering the ‘BER floor’ that is sometimes problematic with conventional turbo decoders.

Claims

1. An iterative decoder, comprising:

an internal code decoder operable to perform iterative decoding of a data block; and

an external code decoder capable of supplying a feedback signal to the internal decoder wherein the feedback signal is used to influence selective decisions during subsequent decoding iterations of the data block, wherein the influence of the feedback signal comprises a path restriction mechanism that prohibits a plurality of undesirable outcomes from occurring during the iterative decoding of the data block.

2. The iterative decoder of claim 1, wherein the path restriction mechanism is performed by normalizing at least one of a plurality of selected state metrics and a plurality of selected path metrics.

3. An iterative decoder, comprising:

an internal code decoder operable to perform iterative decoding of a data block; and

an external code decoder capable of supplying a feedback signal to the internal decoder wherein the feedback signal is used to influence selective decisions during subsequent decoding iterations of the data block, wherein the influence of the feedback signal comprises data overloading that biases the iterative decoding of the data block towards a desired decision outcome.

4. The iterative decoder of claim 3, wherein the data overloading comprises overwriting at least one of input data and ‘

a priori’

data.

5. An iterative decoder method, comprising:

performing iterative internal decoding of a data block; and

feeding back external decoding information to influence selective decisions during subsequent internal decoding iterations of the data block,

wherein the influence of the feeding back of the external decoding information further comprises employing a path restriction mechanism to prohibit a plurality of undesirable outcomes from occurring during the iterative internal decoding of the data block.

6. An iterative decoder method, comprising:

performing iterative internal decoding of a data block; and

feeding back external decoding information to influence selective decisions during subsequent internal decoding iterations of the data block,

wherein the influence of the feeding back of the external decoding information further comprises data overloading that biases the iterative internal decoding of the data block towards a desired decision outcome.

7. An iterative decoder method, comprising:

performing iterative internal decoding of a data block; and

feeding back external decoding information to influence selective decisions during subsequent internal decoding iterations of the data block,

wherein the feeding back of the external decoding information comprises performing path restriction to prohibit a plurality of undesirable outcome from occurring during iterative decoding.

8. The method of claim 7, wherein the restriction mechanism comprises normalizing at least one of a plurality of selected state metrics and a plurality of selected path metrics.

9. An iterative decoder method, comprising:

performing iterative internal decoding of a data block; and

feeding back external decoding information to influence selective decisions during subsequent internal decoding iterations of the data block,

wherein the influence of the selective decisions comprises performing data overloading that biases the iterative decoding of the data block towards a desired decision outcome.

10. An iterative decoder, comprising:

means for performing iterative decoding of a data block; and

means for supplying a feedback signal to the internal decoder,

wherein the feedback signal is used to influence selective decisions during subsequent decoding iterations of the data block, and

wherein the influence of the feedback signal comprises means for performing path restriction mechanism that prohibits a plurality of undesirable outcomes from occurring during the iterative decoding of the data block.

11. The iterative decoder of claim 10, wherein the means for performing path restriction mechanism is performed by normalizing at least one of a plurality of selected state metrics and a plurality of selected path metrics.

12. An iterative decoder, comprising:

means for performing iterative decoding of a data block; and

means for supplying a feedback signal to the internal decoder,

wherein the feedback signal is used to influence selective decisions during subsequent decoding iterations of the data block, and

wherein the influence of the feedback signal comprises means for performing data overloading that biases the iterative decoding of the data block towards a desired decision outcome.

13. The iterative decoder of claim 12, wherein the data overloading comprises overwriting at least one of input data and ‘

a priori’

data.

14. An iterative decoder, comprising:

an internal code decoder operable to perform iterative decoding of a data block; and

an external code decoder capable of supplying a feedback signal to the internal decoder;

wherein the feedback signal is used to influence selective decisions during subsequent decoding iterations of the data block; and

the internal code decoder comprises a binary convolutional code decoder that comprises at least one of a trellis coded modulation decoder and a bit interleaved coded modulation decoder.

15. An iterative decoder, comprising:

an internal code decoder operable to perform iterative decoding of a data block; and

an external code decoder capable of supplying a feedback signal to the internal decoder wherein the feedback signal is used to influence selective decisions during subsequent decoding iterations of the data block;

wherein the influence of the feedback signal comprises a path restriction mechanism that prohibits a plurality of undesirable outcomes from occurring during the iterative decoding of the data block; and

the path restriction mechanism is performed by normalizing at least one of a plurality of selected state metrics and a plurality of selected path metrics.

16. An iterative decoder, comprising:

an internal code decoder operable to perform iterative decoding of a data block; and

an external code decoder capable of supplying a feedback signal to the internal decoder wherein the feedback signal is used to influence selective decisions during subsequent decoding iterations of the data block;

wherein the influence of the feedback signal comprises data overloading that biases the iterative decoding of the data block towards a desired decision outcome; and

the data overloading comprises overwriting at least one of input data and ‘

a priori’

data.

17. An iterative decoder method, comprising:

performing iterative internal decoding of a data block; and

feeding back external decoding information to influence selective decisions during subsequent internal decoding iterations of the data block;

wherein the influence of the feeding back of the external decoding information further comprises employing a path restriction mechanism to prohibit a plurality of undesirable outcomes from occurring during the iterative internal decoding of the data block.

18. An iterative decoder method, comprising:

performing iterative internal decoding of a data block; and

feeding back external decoding information to influence selective decisions during subsequent internal decoding iterations of the data block;

wherein the influence of the feeding back of the external decoding information further comprises data overloading that biases the iterative internal decoding of the data block towards a desired decision outcome.

19. An iterative decoder method, comprising:

performing iterative internal decoding of a data block; and

feeding back external decoding information to influence selective decisions during subsequent internal decoding iterations of the data block;

wherein the feeding back of the external decoding information comprises performing path restriction to prohibit a plurality of undesirable outcome from occurring during iterative decoding; and

the restriction mechanism comprises normalizing at least one of a plurality of selected state metrics and a plurality of selected path metrics.

20. An iterative decoder method, comprising:

performing iterative internal decoding of a data block; and

feeding back external decoding information to influence selective decisions during subsequent internal decoding iterations of the data block;

wherein the influence of the selective decisions comprises performing data overloading that biases the iterative decoding of the data block towards a desired decision outcome.