Quasi error free (QEF) communication using turbo codes

• US 20020051499A1
• Filed: 09/05/2001
• Published: 05/02/2002
• Est. Priority Date: 09/05/2000
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Jones, Christopher R., Cameron, Kelly B.
• Granted Patent: US 7,421,044 B2
• Time in Patent Office: Days
• US Class Current: 375/295
• CPC Class Codes: H03M 13/1515 Reed-Solomon 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 13/2732 Convolutional interleaver; Interleavers using shift-registers or delay lines like, e.g. Ramsey type interleaver
• CPC Class Codes: H03M 13/275 Interleaver wherein the permutation pattern is obtained using a congruential operation of the type y=ax+b modulo c
• CPC Class Codes: H03M 13/2789 Interleaver providing variable interleaving, e.g. variable block sizes
• CPC Class Codes: H03M 13/29 combining two or more codes or code structures, e.g. product codes, generalised product codes, concatenated codes, inner and outer codes
• CPC Class Codes: H03M 13/2945 using at least three error correction codes H03M13/2957 takes precedence
• CPC Class Codes: H03M 13/2966 Turbo codes concatenated with another code, e.g. an outer block code
• CPC Class Codes: H03M 13/3988 for rate k/n convolutional codes, with k>1, obtained by convolutional encoders with k inputs and n outputs
• CPC Class Codes: H03M 13/45 Soft decoding, i.e. using symbol reliability information H03M13/41 takes precedence
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0066 Parallel concatenated codes
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27

Abstract

A method for encoding and decoding information using turbo codes. Turbo codes, though providing error performance superior to many codes, exhibit a phenomenon known as error floor. The error floor is a bit error level that turbo codes themselves have had difficulty improving on. This error floor can prove problematical for quasi error free applications in which error rates on the order of 10⁻¹⁰ are required. In addition turbo codes have failure modes in which errors occur in a burst, which may preclude the establishment of quasi error free communication. Such quasi error free applications also require an error correction that is superior to that generally represented by the error floor of turbo-codes. Quasi error free performance can be produced using turbo codes as an inner code in conjunction with an algebraic outer code linked by an interleaver. A combination of outer algebraic code and turbo inner code linked by an interleaver, which has a guaranteed minimum Depth between symbols output from the interleaver, can produce a quasi error free performance in systems utilizing Turbo-Codes without an increase in bandwidth.

Claims

1. A method for encoding, to provide a quasi error free decoding, the method comprising:

providing data to be communicated;

algebraically encoding the data to be communicated thereby producing algebraically encoded data;

interleaving the algebraic encoded data in an interleaver having a guaranteed Depth thereby producing interleaved data; and

turbo encoding the interleaved data thereby producing turbo encoded data;

2. The method of claim 1 wherein algebraically encoding the data to be communicated comprises Reed-Solomon encoding the data to be communicated.

3. The method of claim 1 wherein interleaving the algebraic encoded data comprises using a Ramsey interleaver to interleave the algebraic encoded data.

4. The method of claim 1 wherein turbo encoding the interleaved data comprises modulo-N turbo encoding of the interleaved data.

5. The method of claim 4 wherein N>

2.

6. The method of claim 1 wherein turbo encoding the interleaved data further comprises providing at least one nonsystematic component encoding.

7. The method of claim 1 wherein the guaranteed Depth is at least 201.

8. A method for decoding quasi error free encoded data the method comprising:

accepting data to be decoded which has been encoded according to the method of claim 1;

turbo decoding the data to be decoded;

deinterleaving the data using a deinterleaver having a guaranteed depth to produce deinterleaved data; and

algebraically decoding the deinterleaved data to produce decoded data.

9. The method of claim 8 wherein decoding the data to be communicated comprises Reed-Solomon decoding the data to be communicated.

10. The method of claim 8 wherein deinterleaving the data to be decoded comprises using a Ramsey deinterleaver to deinterleave the algebraic encoded data.

11. The method of claim 8 wherein turbo decoding the interleaved data comprises modulo-N turbo decoding of the interleaved data.

12. The method of claim 8 wherein N>

2.

13. The method of claim 11 wherein modulo-N turbo decoding further comprises parallel map decoding.

15. The apparatus of claim 14 wherein the algebraic encoder comprises a Reed-Solomon encoder.

16. The apparatus of claim 14 wherein the interleaver comprises a Ramsey interleaver.

17. The apparatus of claim 14 wherein the turbo encoder comprises a modulo-N turbo encoder.

18. The apparatus of claim 4 wherein N>

2.

19. The apparatus of claim 14 wherein the turbo encoder comprises a turbo-trellis encoder.

20. A decoder apparatus comprising:

a turbo decoder that accepts data to be decoded, which has been encoded according to the method of claim 1, to produce turbo decoded data;

a deinterleaver that accepts the turbo decoded data and produce deinterleaved data; and

an algebraic decoder that decodes the deinterleaved data to produce decoded data.

21. The apparatus of claim 20 wherein the algebraic decoder comprises a Reed-Solomon decoder.

22. The apparatus of claim 20 wherein the deinterleaver comprises a Ramsey deinterleaver.

23. The apparatus of claim 20 wherein the turbo decoder comprises a modulo-N turbo decoder.

24. The apparatus of claim 20 wherein N>

2.

25. The method of claim 11 wherein the modulo-N turbo decoder is a parallel map decoder.

14. An encoding apparatus the apparatus comprising:

an input that accepts data to be encoded;

an algebraic encoder that receives the data to be encoded and algebraically encodes the data thereby producing algebraically encoded data;

an interleaver that interleaves the algebraically encoded data, said interleaver having a guaranteed Depth, thereby producing interleaved data; and

a turbo encoder that encodes the interleaved data thereby producing turbo encoded data;