Various methods and apparatuses for impulse noise detection

• US 7,813,439 B2
• Filed: 02/06/2006
• Issued: 10/12/2010
• Est. Priority Date: 02/06/2006
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Lery, Scott A., Desjardins, Philip, Behrin, Mike, Norrell, Andy
• Primary Examiner(s): Tran; Khanh C
• Application Number:
  US11/348,733
• Publication Number:
  US 20070183526A1
• Time in Patent Office: 1,709 Days
• Field of Search: 375/260, 375/262, 375/265, 375340-341, 375/346, 714/786, 714/788, 714/792, 714/795, 714/701, 714/752, 370/335, 370/342
• US Class Current: 375/265
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 25/061 providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of dc offset removal of dc offset in coupling arrangements H04L25/029, H04L25/0296
• CPC Class Codes: H04L 25/067 providing soft decisions, i.e. decisions together with an estimate of reliability H04L25/068 and H04L25/069 take precedence; sequence estimation techniques H04L25/03178
• CPC Class Codes: H04L 27/2078 in which the phase change per symbol period is constrained coset coding H04L27/186
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

Methods and apparatuses for reducing effects of impulse noise in a DSL transmitter receiver device are described. According to certain embodiment, the method includes comparing a hard decision output of a decoder with a soft decision output for a convolution coded modulation symbol received at a digital subscriber line (DSL) receiver. The presence of impulse noise is detected based on a lack of agreement between the hard decision output and the soft decision output.

Claims

1. A method for impulse noise detection, comprising:

processing a received signal using a first stage of a decoder arrangement to provide a hard decision output representing best estimates of transmitted data elements and a second stage of the decoder arrangement to provide a soft decision output based on the hard decision output, the soft decision output representing a determination of whether a grouping of the hard decision outputs represents an allowable sequence of data elements;

comparing the hard decision output with the soft decision output; and

detecting a presence of impulse noise based on a lack of agreement between the hard decision output and the soft decision output.

2. The method of claim 1, wherein the received signal comprises a trellis coded modulated signal.

3. The method of claim 1, further comprising:

selecting the hard decision output from a set of hard decision outputs of the decoder arrangement based upon a distance between the hard decision output and a point received at the decoder arrangement.

4. The method of claim 1, further comprising:

setting an indicator to indicate the lack of agreement between the hard decision output and the soft decision output; and

comparing the indicator with a threshold to determine the presence of the impulse noise.

5. The method of claim 1, further comprising:

instructing to reduce an amount of data transmitted with data frames in which the presence of the impulse noise is detected as compared to data frames with no impulse noise.

6. The method of claim 1, further comprising:

setting an indicator to indicate the lack of agreement between the hard decision output and the soft decision output;

comparing the indicator with a threshold to determine the presence of the impulse noise; and

utilizing the indicator in an erasure indicator for DSL systems employing erasure decoding.

7. A method for impulse noise detection, comprising:

comparing a hard decision output of a decoder with a soft decision output of the decoder for a convolution coded modulation symbol received at a digital subscriber line (DSL) receiver;

detecting a presence of impulse noise based on a lack of agreement between the hard decision output and the soft decision output; and

selecting the soft decision output from a set of soft decision outputs of the decoder based upon a match between the set of soft decision outputs and a received sequence.

8. A digital subscriber line (DSL) modem, comprising a receiver, the receiver comprising:

a trellis decoder, having a soft decision output and a hard decision output, configured to decode which of a plurality of sub-constellations are received at the receiver, the hard decision output representing best estimates of transmitted data elements and the soft decision output being based on the hard decision and representing a determination of whether a grouping of the hard decision outputs represents an allowable sequence of data elements;

a comparator configured to receive the soft decision output and the hard decision output, to compare soft decision data from the soft decision output and hard decision data from the hard decision output, and to generate a comparison result on an output of the comparator; and

an impulse noise predictor to predict when data frames are affected by impulse noise based upon the comparison result.

9. The DSL modem of claim 8, wherein data frames are decoded into P-dimensional constellations having 2^N sub-constellations.

10. The DSL modem of claim 8, further comprising:

a table configured and arranged to receive the output of the comparator and to set an indicator to indicate a lack of agreement between the hard decision data and the soft decision data.

11. The DSL modem of claim 8, wherein the comparator is further configured to select the hard decision data from a set of hard decision outputs based upon a distance between each of the set of hard decision outputs and a point received at the trellis decoder.

12. The DSL modem of claim 10, wherein the distance between the hard decision data that is selected and the point received at the trellis decoder is shorter than the distance between each of the set of hard decision outputs that was not selected and the point received at the trellis decoder.

13. The DSL modem of claim 8, wherein the comparator is further configured to select the soft decision data from a set of soft decision outputs based upon a match between the set of soft decision outputs and a received sequence of data.

14. The DSL modem of claim 8, wherein the trellis decoder is a viterbi decoder.

15. A DSL system, comprising:

a first transmitter-receiver device having a receiver, the receiver having an impulse noise predictor configured to determine if data frames are affected by impulse noise based on a comparison of soft decision data and hard decision data of a decoder arrangement at the receiver,

the receiver being configured to process a received signal using a first stage of the decoder arrangement to provide a hard decision output representing best estimates of transmitted data elements and a second stage of the decoder arrangement to provide a soft decision output based on the hard decision output, the soft decision output representing a determination of whether a grouping of the best estimates represents an allowable sequence of data elements,

the receiver being configured to compare the hard decision output with the soft decision output, and

the receiver being configured to detect a presence of impulse noise based on a lack of agreement between the hard decision output and the soft decision output; and

a second transmitter-receiver device having a transmitter, the first transmitter-receiver device being configured and arranged to transmit parameters of the impulse noise to the second transmitter-receiver device.

16. The DSL system of claim 15, wherein the second transmitter-receiver device is configured to reduce payload data in frames upon receiving the control parameters from the first transmitter-receiver device.

17. A method for impulse noise detection, comprising:

comparing a hard decision output of a decoder with a soft decision output of the decoder for a convolution coded modulation symbol received at a digital subscriber line (DSL) receiver; and

detecting a presence of impulse noise based on a lack of agreement between the hard decision output and the soft decision output, wherein the hard decision output is a nearest-neighbor decision output corresponding to a sub-constellation point nearest to a current point received at the decoder, and wherein the soft decision output is a coding-assisted decision output corresponding to an allowed sequence of points best matched to a sequence of points received at the decoder.

18. A digital subscriber line (DSL) modem, comprising a receiver, the receiver comprising:

a trellis decoder, having a soft decision output and a hard decision output, configured to decode which of a plurality of sub-constellations are received at the receiver;

a comparator, coupled to the soft decision output and the hard decision output, configured to compare a soft decision data from the soft decision output and the hard decision data from the hard decision output for a convolution coded modulation symbol received at the receiver and to generate a comparison result on an output of the comparator; and

an impulse noise predictor to predict when data frames are affected by impulse noise based upon the comparison result,

wherein the hard decision output is a nearest-neighbor decision output corresponding to a sub-constellation point of the plurality of sub-constellations nearest to a current point received at the trellis decoder, and wherein the soft decision output is a coding-assisted decision output corresponding to an allowed sequence of points best matched to a sequence of points received at the trellis decoder.