MODULATION ANALYSIS AND DISTORTION IDENTIFICATION

• US 20110194597A1
• Filed: 08/02/2010
• Published: 08/11/2011
• 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: Chang, Phillip F., Wolcott, Lawrence D.
• Granted Patent: US 8,693,530 B2
• Time in Patent Office: Days
• US Class Current: 375/229
• 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:

retrieving a set of equalization coefficients; and

generating, based on the set of equalization coefficients, a symbol placement associated with a transmission scheme.

2. The method of claim 1, further comprising:

generating a constellation pattern based on the symbol placement.

3. The method of claim 2, further comprising:

displaying the generated constellation pattern on a display device.

4. The method of claim 1, further comprising:

retrieving a second set of equalization coefficients; and

transforming the second set of equalization coefficients to generate a second synthesized symbol placement associated with the transmission scheme.

5. The method of claim 1, further comprising:

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

6. The method of claim 1, further comprising:

quantifying a distortion present in a communication channel in terms of at least one of amplitude over an operating frequency range and phase over the operating frequency range.

7. The method of claim 1, further comprising:

calculating for at least one of the symbols included in the symbol placement a distance relative to a corresponding ideal symbol; and

displaying the calculated distance.

8. A method comprising:

determining that equalization is unable to reduce a signal impairment associated with a signal received from a user terminal below a threshold value within a predetermined amount of time; and

determining that a non-linear distortion source is present in a communication channel connected to the user terminal responsive to said determining that the equalization is unable to reduce the signal impairment associated with the signal received from the user terminal below the threshold value within the predetermined amount of time.

9. The method of claim 8, further comprising:

determining that equalization is unable to reduce a signal impairment associated with a signal received from each of a plurality of user terminals below the threshold value within the predetermined amount of time, the plurality of user terminals including the user terminal; and

comparing a layout associated with the plurality of user terminals relative to a layout associated with at least one other terminal to determine a probable location of the non-linear distortion source, wherein a signal received from the at least one other terminal is not impaired above the threshold value.

10. The method of claim 9, further comprising:

generating at least one status message comprising a map identifying a geographic region where the plurality of user terminals is located.

11. The method of claim 9, further comprising:

generating at least one status message comprising an identification of at least one device located at the probable location of the non-linear distortion source.

12. An apparatus comprising:

at least one processor; and

memory storing instructions that, when executed by the at least one processor, cause the apparatus to;

retrieve a set of equalization coefficients; and

generate, based on the set of equalization coefficients, a symbol placement associated with a transmission scheme.

13. The apparatus of claim 12, wherein the instructions, when executed by the at least one processor, cause the apparatus to:

generate a constellation pattern based on the symbol placement.

14. The apparatus of claim 13, further comprising:

a display device,

wherein the instructions, when executed by the at least one processor, cause the apparatus to;

display the constellation pattern on the display device.

15. The apparatus of claim 12, wherein the instructions, when executed by the at least one processor, cause the apparatus to:

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

16. The apparatus of claim 12, wherein the instructions, when executed by the at least one processor, cause the apparatus to:

quantify a distortion present in a communication channel between the apparatus and at least one user terminal in terms of at least one of amplitude over an operating frequency range and phase over the operating frequency range.

17. The apparatus of claim 12, wherein the transmission scheme comprises quadrature amplitude modulation.

18. The apparatus of claim 12, wherein the instructions, when executed by the at least one processor, cause the apparatus to:

identify a subset of symbols included in the symbol placement that are within a threshold distance of one or more decision boundaries.

19. The apparatus of claim 12, wherein the instructions, when executed by the least one processor, cause the apparatus to:

transmit to a user terminal at least one of;

(1) a request to schedule an appointment and, (2) guidance on how to alter the user terminal or a component associated with the user terminal, based on the generated symbol placement.

20. The apparatus of claim 12, wherein the instructions, when executed by the least one processor, cause the apparatus to:

retrieve a second set of equalization coefficients subsequent to retrieving the first set of equalization coefficients; and

update the symbol placement associated with the transmission scheme responsive to retrieving the second set of equalization coefficients.