Modulation analysis and distortion identification

• US 9,602,518 B2
• Filed: 02/24/2014
• Issued: 03/21/2017
• Est. Priority Date: 02/05/2010
• Status: Active Grant

• Current Assignee: Comcast Cable Communications LLC (Comcast Corporation)
• Original Assignee: Comcast Cable Communications LLC (Comcast Corporation)
• Inventors: Wolcott, Lawrence D., Chang, Phillip F.
• Primary Examiner(s): Tran, Khanh C
• Application Number:
  US14/187,912
• Publication Number:
  US 20140241409A1
• Time in Patent Office: 1,121 Days
• Field of Search: 375/229, 375/261, 375/285, 375/340, 375/346, 375/350, 375/224, 375/227, 375231-232, 375/257, 375/296, 375/377
• US Class Current: 1/1
• CPC Class Codes: H04L 2025/0342 QAM
• CPC Class Codes: H04L 2025/03808 Transmission of equaliser coefficients
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/03 Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
• CPC Class Codes: H04L 25/03019 adaptive, i.e. capable of adjustment during data reception
• CPC Class Codes: H04L 43/0823 Errors, e.g. transmission errors
• CPC Class Codes: H04L 63/107 wherein the security policies are location-dependent, e.g. entities privileges depend on current location or allowing specific operations only from locally connected terminals
• CPC Class Codes: H04L 67/52 specially adapted for the location of the user terminal

Abstract

An apparatus, method, computer readable medium, and system are provided to generate a symbol placement associated with a transmission scheme by transforming a retrieved set of equalization coefficients. Symbols included in the symbol placement may be analyzed and quantified in terms of their distance from a decision boundary. Symbols may be synthesized on an iterative basis in order to obtain visibility into the underlying performance of the transmission scheme over time. If equalization is unable to reduce a signal impairment below a threshold value within a predetermined amount of time, then a determination may be made that a non-linear distortion source is present in a network or communication system. Signals received from a plurality of user terminals may be compared with one another in order to determine a probable location or cause of the non-linear distortion.

Claims

1. A method comprising:

generating, by a first computing device and based on a first signal received from a second computing device, a first symbol placement, wherein the first signal was transmitted based on a first set of equalization coefficients;

transmitting, by the first computing device and to the second computing device, a second set of equalization coefficients;

generating, by the first computing device and based on a second signal received from the second computing device, a second symbol placement, wherein the second signal was transmitted based on the second set of equalization coefficients; and

transmitting, based at least in part on the second symbol placement, a status message comprising an indication of one or more symbols that satisfy a threshold indicative of likely demodulation error at the second computing device.

2. The method of claim 1, further comprising:

determining, by the first computing device, whether a signal impairment associated with the second signal satisfies a threshold value; and

in response to determining that the signal impairment associated with the second signal does not satisfy the threshold value, determining that the signal impairment associated with the second signal is non-linear.

3. The method of claim 2, further comprising:

determining that a signal impairment associated with a third signal received from a third computing device is non-linear;

determining a network component of a communication channel common to the second computing device and the third computing device; and

determining that the network component is a probable error source location of the signal impairment associated with the second signal and the signal impairment associated with the third signal, wherein the status message comprises an identifier of the network component.

4. The method of claim 1, further comprising:

calculating at least one of a modulation error ratio (MER) and an error vector based on the first symbol placement.

5. The method of claim 1, further comprising:

determining a location of a source likely causing a non-linear signal impairment, wherein the status message comprises an indication of a distance between the source and the second computing device.

6. The method of claim 1, further comprising:

calculating, by the first computing device, a distance between a location of an ideal symbol placement and an actual location of the second symbol placement.

7. The method of claim 1, further comprising:

generating, based on the first symbol placement and the second symbol placement, a constellation pattern, wherein the constellation pattern comprises a plurality of demodulation decision boundaries for different symbols, and wherein the threshold indicative of likely demodulation error comprises a threshold distance to a demodulation decision boundary of the plurality of demodulation decision boundaries.

8. The method of claim 1, wherein the first set of equalization coefficients comprises a set of pre-equalization coefficients.

9. A method comprising:

determining, by a first computing device, that application of equalization coefficients to signals transmitted by a second computing device and via a communication channel is unable to reduce signal impairment associated with the signals to satisfy a threshold value within a threshold amount of time;

determining, by the first computing device and based on the determining, that a non-linear signal impairment is present in the communication channel used by the second computing device; and

causing output of an indication of the determination that the non-linear signal impairment is present in the communication channel used by the second computing device.

10. The method of claim 9, further comprising:

determining, by the first computing device, that a signal received from a third computing device has the non-linear signal impairment; and

determining, by the first computing device and based on a communication path common to the second computing device and the third computing device, a probable location of a source of the non-linear signal impairment.

11. The method of claim 10, further comprising:

transmitting at least one status message comprising a map indicating a geographic region where the second computing device and the third computing device are located.

12. The method of claim 11,

wherein the at least one status message comprises an indication of a distance between the probable location of the source and the second computing device.

13. A method comprising:

generating, by a first computing device and based on a first set of equalization coefficients associated with a first signal received from a second computing device, a first symbol placement;

generating, by the first computing device and based on a second set of equalization coefficients associated with a second signal received from the second computing device, a second symbol placement; and

determining, by the first computing device, a likely source of a demodulation error associated with the first symbol placement and the second symbol placement.

14. The method of claim 13, further comprising:

transmitting a status message comprising an indication of which of a plurality of symbols is more likely to be subject to a demodulation error at the second computing device.

15. The method of claim 13, further comprising:

determining, by the first computing device, whether a signal impairment associated with the second signal satisfies a threshold value; and

in response to determining that the signal impairment associated with the second signal does not satisfy the threshold value, determining that the signal impairment associated with the second signal is non-linear.

16. The method of claim 13, further comprising:

transmitting, by the first computing device, to a device, and based on the second symbol placement, guidance on how to alter the second computing device or a component associated with the second computing device.

17. The method of claim 13, further comprising:

transmitting, based on the second symbol placement, a distance between the second computing device and the likely source of the demodulation error.

18. The method of claim 13, further comprising:

generating, by first the computing device, a constellation pattern based on the first symbol placement and the second symbol placement.

19. The method of claim 13, further comprising:

calculating one or more of a modulation error ratio (MER) or an error vector corresponding to the second symbol placement.

20. The method of claim 13, wherein the first set of equalization coefficients comprises a set of pre-equalization coefficients.