Method and apparatus for evaluating error control parameters of self-similar constellations

• US 7,263,130 B1
• Filed: 05/25/2001
• Issued: 08/28/2007
• Est. Priority Date: 05/25/2001
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Mitlin, Vlad
• Primary Examiner(s): Payne; David C.
• Assistant Examiner(s): Bolourchi; Nader
• Application Number:
  US09/865,763
• Time in Patent Office: 2,286 Days
• Field of Search: 375/260, 375/261, 375/353, 375/365, 370/468, 370/208
• US Class Current: 375/260
• CPC Class Codes: H04K 1/10 by using two signals transmitted simultaneously or successively
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 27/362 Modulation using more than one carrier, e.g. with quadrature carriers, separately amplitude modulated H04L27/366 takes precedence
• CPC Class Codes: H04L 27/366 Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator
• CPC Class Codes: H04L 27/38 Demodulator circuits; Receiver circuits
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

A method and apparatus implementing the method, of selecting a bit load b for a channel in a carrier system. The carrier system encodes data based on a constellation of points. Each point represents a tuple of data. The constellation has a self-similarity property. The bit load for the channel is selected based on the self-similarity property of the constellation. In an alternate embodiment, the method and apparatus are used to determine the bit load of the sub-channels in a multi-carrier system.

Claims

1. A method of selecting a bit load b per sub-channel in a multicarrier system, the multicarrier system encoding data based on a constellation of points, each point representing a tuple of data, the constellation having a self-similarity property, comprising:

determining a probability of having k bit errors in an erroneous tuple (p(k,b)) based on Hamming distances between the points of the constellation;

estimating an average number of bit errors in an erroneous tuple based on said probability (p(k,b)); and

selecting the bit load per sub-channel based on the estimated number of bit errors in an erroneous tuple.

2. The method of claim 1 wherein said average number of bit errors in the erroneous tuple is determined as follows:

3. The method of claim 1 wherein said probability (p(k,b)) is determined as follows:

4. The method of claim 1 wherein said probability (p(k,b)) is determined as follows:

5. The method of claim 1 wherein said probability (p(k,b)) approaches ½

^k for constellations which have large values of b.

6. The method of claim 1 wherein said constellation is square.

7. The method of claim 1 wherein said constellation is non-square.

8. The method of claim 1 wherein the sub-channel has a bit error rate, and further comprising:

determining a mean square deviation of the number of bit errors in an erroneous tuple;

wherein said selecting further comprises selecting the bit load per sub-channel based on said mean square deviation of the number of bit errors in an erroneous tuple.

9. The method of claim 8 wherein said mean square deviation of the number of bit errors in an erroneous tuple σ

_e is determined based on the following relationship;

10. The method of claim 8 wherein at large values of b, the mean square deviation of the number of bit errors in an erroneous tuple σ

_e tends to the square root of two.

11. The method of claim 8 further comprising:

accessing a table of associated values of the number of bits b and the values of the mean square deviation of the number of bit errors in an erroneous tuple to retrieve a value of a particular mean square deviation of the number of bits errors in an erroneous tuple for a particular value of b; and

adjusting a target bit error rate to accommodate said value of said particular mean square deviation of the number of bit errors in an erroneous tuple to provide an adjusted target bit error rate, wherein said bit load is also selected based on said adjusted target bit error rate.

12. The method of claim 11 further comprising:

selecting at least one forward error correction parameter based on said adjusted target bit error rate.

13. The method of claim 1 wherein said selecting comprises:

determining a probability of having k bit errors in an erroneously decoded tuple as follows;

14. The method of claim 1 wherein said constellation is non-square, and said probability of having k bit errors in an erroneously decoded tuple of the non-square constellation is estimated as if said non-square constellation was a square constellation.

15. The method of claim 1 wherein said constellation is non-square, and said probability of error of said non-square constellation becomes asymptotically close to the probability of error of a square constellation encoder.

16. A method of selecting a bit load b for a channel in a communications system, the communications system encoding data based on a non-square constellation of points, the non-square constellation having a self-similarity property, comprising:

determining a probability of having k bit errors in an erroneously decoded tuple (p(k,b)) based on the self-similarity property of the non-square constellation, wherein said probability of having k bit errors in an erroneously decoded tuple of the non-square constellation is estimated as if said non-square constellation was a square constellation;

selecting the bit load for the channel using said probability.

17. The method of claim 16 wherein the channel has a bit error rate, and further comprising

determining a mean square deviation of the number of bit errors in an erroneous tuple;

wherein said selecting further comprises selecting the bit load based on said mean square deviation of the number of bit errors in an erroneous tuple.

18. The method of claim 16 wherein said self-similarity property is determined with respect to a Hamming distance between the points of the constellation.

19. An apparatus for selecting a bit load b for a channel in a communications system, the communications system encoding data based on a non-square constellation of points, the non-square constellation having a self-similarity property, comprising:

means for selecting the bit load for the channel using an improved estimate of bit error per symbol error based on the self-similarity property of the constellation, wherein said means for selecting comprises means for determining a probability of having k bit errors in an erroneously decoded tuple (p(k,b)) based on Hamming distances between the points of the non-square constellation, and wherein said probability of having k bit errors in an erroneously decoded tuple of the non-square constellation is estimated as if said non-square constellation was a square constellation.

20. The apparatus of claim 19 wherein the channel has a bit error rate, and said means for selecting further comprises means for determining a mean square deviation of the number of bit errors in an erroneous tuple, wherein said means for selecting selects the bit load based on said mean square deviation of the number of bit errors in an erroneous tuple.

21. An apparatus for selecting a bit load b per sub-channel in a multicarrier system, the multicarrier system encoding data based on a constellation of points, each point representing a tuple of data, the constellation having a self-similarity property, comprising:

means for determining a bit load per sub-channel using an estimate of bit error per symbol error and forward error correction parameters, comprising means for determining a probability of having k bit errors in an erroneous tuple (p(k,b)) based on Hamming distances between the points of the constellation, and means for estimating an average number of bit errors in an erroneous tuple based on said probability (p(k,b)); and

means for selecting a bit load based on coding gain and the average number of bit errors in the erroneous tuple.

22. The apparatus of claim 21 wherein said probability (p(k,b)) is determined as follows:

23. The apparatus of claim 21 wherein said probability (p(k,b)) is determined as follows:

24. The apparatus of claim 21 wherein said probability (p(k,b)) approaches ½

^k for constellations which have large values of b.

25. The apparatus of claim 21 wherein said constellation is square.

26. The apparatus of claim 21 wherein said constellation is non-square.

27. The apparatus of claim 21 wherein the sub-channel has a bit error rate, and said means for determining the bit load further comprises:

means for determining a mean square deviation of the number of bit errors in an erroneous tuple;

wherein said means for selecting also selects the bit load per sub-channel based on said mean square deviation of the number of bit errors in an erroneous tuple.

28. The apparatus of claim 27 wherein said means for determining the mean square deviation of the number of bit errors in an erroneous tuple determines said mean square deviation of the number of bit errors in an erroneous tuple σ

_e in accordance with the following relationship;

29. The apparatus of claim 28 wherein at large values of b, σ

_e tends to the square root of two.

30. The apparatus of claim 27 further comprising:

means for accessing a table of associated values of the number of bits b and the values of the mean square deviation of the number of bit errors in an erroneous tuple to retrieve a value of a particular mean square deviation of the number of bit errors in an erroneous tuple for a particular value of b; and

means for adjusting a target bit error rate to accommodate said value of said particular mean square deviation of the number of bit error in an erroneous tuple to provide an adjusted target bit error rate, wherein said means for selecting also selects said bit load based on said adjusted target bit error rate.

31. The apparatus of claim 30 wherein said means for selecting selects at least one forward error correction parameter based on said adjusted target bit error rate.

32. The apparatus of claim 21 wherein said means for determining a bit load comprises:

means for determining a probability of having k bit errors in an erroneously decoded tuple in accordance with the following relationship;

33. The apparatus of claim 21 wherein said constellation is non-square, and said probability of having k bit errors in an erroneously decoded tuple of the non-square constellation is estimated as if said non-square constellation was a square constellation.

34. The apparatus of claim 21 wherein said constellation is non-square, and said probability of error of said non-square constellation becomes asymptotically close to the probability of error of a square constellation encoder.

35. The apparatus of claim 21 wherein said self-similarity property is determined with respect to a Hamming distance between the points of the constellation.