METHOD OF CHARACTERIZING IMPAIRMENTS DETECTED BY EQUALIZATION ON A CHANNEL OF A NETWORK

• US 20140029655A1
• Filed: 07/30/2012
• Published: 01/30/2014
• Est. Priority Date: 07/30/2012
• Status: Active Grant

• Current Assignee: ARRIS Enterprises LLC (CommScope Holding Company, Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Thompson, Robert J., Moore, Charles S., Moran, John L. III, Morrissette, Marc L.
• Granted Patent: US 9,136,943 B2
• Time in Patent Office: Days
• US Class Current: 375/224
• CPC Class Codes: H04B 10/0795 Performance monitoring; Measurement of transmission parameters
• CPC Class Codes: H04B 10/2507 for the reduction or elimination of distortion or dispersion
• CPC Class Codes: H04B 10/25751 Optical arrangements for CATV or video distribution adaptations of television systems for optical transmission H04N7/22
• CPC Class Codes: H04B 10/66 Non-coherent receivers, e.g. using direct detection
• CPC Class Codes: H04B 3/46 Monitoring; Testing
• CPC Class Codes: H04L 25/03006 Arrangements for removing intersymbol interference

Abstract

An automated method of characterizing distortion detected by equalization on a channel of a network is provided. Equalization stress of an observed channel equalization response of an end device of the network is estimated, and equalization stress is calculated for a theoretical channel equalization response of the end device mathematically based on the observed channel equalization response and a theoretical removal of a suspected impairment from the network. The above referenced calculating step is separately repeated for each of a plurality of suspected impairments stored in a database of suspected impairments. A highest ranking suspected dominant impairment is determined from the database of suspected impairments such that removal of the highest ranking suspected dominant impairment from the network would provide a greatest reduction of equalization stress of a channel equalization response of the end device.

Claims

1. An automated method of characterizing impairments detected by equalization on a channel of a network, comprising, in at least one processor:

estimating a first equalization stress of an observed channel equalization response of an end device of the network required for equalization;

calculating a second equalization stress of a channel equalization response of the end device mathematically based on the observed channel equalization response and a removal of a suspected impairment from the network;

repeating said calculating step separately for each of a plurality of suspected impairments stored in a database of suspected impairments; and

determining a highest ranking suspected dominant impairment from the database of suspected impairments that, if removed from the network, would provide a greatest reduction of an equalization stress of a channel equalization response of the end device.

2. An automated method according to claim 1, wherein, during said determining step, a next highest ranking suspected dominant impairment is identified from the database of suspected impairments that, if removed from the network, would provide a next greatest reduction of equalization stress of the channel equalization response of the end device.

3. An automated method according to claim 2, further comprising a step of determining a further modified channel equalization response from the observed channel equalization response assuming the highest ranking suspected dominant impairment and the next highest ranking suspected dominant impairment are removed from the network.

4. An automated method according to claim 1, wherein, during said determining step, an ordered series of next highest ranking suspected dominant impairments are identified from the database of suspected impairments that, if removed from the network, would provide next greatest reductions of the equalization stress of the channel equalization response of the end device.

5. An automated method according to claim 4, further comprising a step of determining a further modified channel equalization response from the observed channel equalization response assuming the highest ranking suspected dominant impairment, a next highest ranking suspected dominant impairment, and at least one additional next highest ranking suspected dominant impairment are removed from the network.

6. An automated method according to claim 1, wherein said calculating step includes division of the observed channel equalization response by a known channel equalization response of the suspected impairment to produce the channel equalization response from which the equalization stress of the channel equalization response is determined.

7. An automated method according to claim 1, wherein equalization stress is measured by at least one metric selected from a group of metrics consisting of Main Tap Compression (MTC), Non Main Tap to Total Tap Energy Ratio (NMTTER), Pre Main Tap Energy Ratio (PreMTTER), Post Main Tap Energy Ratio (PostMTTER), Pre/Post Energy Symmetry Ratio (PPESR), and Pre/Post Tap Symmetry Ratio (PPTSR).

8. An automated method according to claim 1, wherein the database of suspected impairments includes a known impairment equalization response for each of the suspected impairments in the database.

9. An automated method according to claim 8, further comprising a step of populating the database of suspected impairments with known impairment equalization responses obtained based on at least one of laboratory simulations and prior actual observations.

10. An automated method according to claim 1, wherein said estimating, re-calculating, repeating, and determining steps are performed electronically with software.

11. An apparatus for characterizing impairments detected by equalization on a channel of a network, comprising:

one or more processors communicatively coupled to the network, wherein the network has a headend with a cable modem termination system (CMTS);

the one or more processors configured to estimate a first equalization stress of an observed channel equalization response of a cable modem of the network required for equalization;

the one or more processors further configured to calculate a second equalization stress of a channel equalization response of the cable modem mathematically based on the observed channel equalization response and a removal of a suspected impairment from the network;

the one or more processors further configured to repeat said calculating step separately for each of a plurality of suspected impairments stored in a database of suspected impairments; and

the one or more processors further configured to determine a highest ranking suspected dominant impairment from the database of suspected impairments that, if removed from the network, would provide a greatest reduction of an equalization stress of a channel equalization response of the cable modem;

wherein a communication protocol used by the cable modem and CMTS for equalization is Data Over Cable System Interface Specification (DOCSIS), and a modulation scheme used by the network is quadrature amplitude modulation (QAM).

12. At least one non-transitory computer readable storage medium having computer program instructions stored thereon that, when executed by at least one processor, cause the at least one processor to perform the following operations:

estimating a first equalization stress of an observed channel equalization response of an end device of a network;

calculating a second equalization stress of a channel equalization response of the end device mathematically based on the observed channel equalization response and a removal of a suspected impairment from the network;

repeating said calculating step separately for each of a plurality of suspected impairments stored in a database of suspected impairments; and

determining a highest ranking suspected dominant impairment from the database of suspected impairments that, if removed from the network, would provide a greatest reduction of an equalization stress of a channel equalization response of the end device.

13. At least one non-transitory computer readable storage medium according to claim 12, wherein, during said determining operation, a next highest ranking suspected dominant impairment is identified from the database of suspected impairments that, if removed from the network, would provide a next greatest reduction of equalization stress of the channel equalization response of the end device.

14. At least one non-transitory computer readable storage medium according to claim 13, wherein the computer program instructions, when executed by the at least one processor, cause the at least one processor to determine a further modified channel equalization response from the observed channel equalization response assuming the highest ranking suspected dominant impairment and the next highest ranking suspected dominant impairment are removed from the network.

15. At least one non-transitory computer readable storage medium according to claim 12, wherein, during said determining step, an ordered series of next highest ranking suspected dominant impairments are identified from the database of suspected impairments that, if removed from the network, would provide next greatest reductions of the equalization stress of the channel equalization response of the end device.

16. At least one non-transitory computer readable storage medium according to claim 15, wherein the computer program instructions, when executed by the at least one processor, cause the at least one processor to determine a further modified channel equalization response from the observed channel equalization response assuming the highest ranking suspected dominant impairment, a next highest ranking suspected dominant impairment, and at least one additional next highest ranking suspected dominant impairment are removed from the network.

17. At least one non-transitory computer readable storage medium according to claim 12, wherein the calculating operation includes division of the observed channel equalization response by a known channel equalization response of the suspected impairment to produce the channel equalization response from which the equalization stress of the channel equalization response is determined.

18. At least one non-transitory computer readable storage medium according to claim 12, wherein equalization stress is measured by at least one metric selected from a group of metrics consisting of Main Tap Compression (MTC), Non Main Tap to Total Tap Energy Ratio (NMTTER), Pre Main Tap Energy Ratio (PreMTTER), Post Main Tap Energy Ratio (PostMTTER), Pre/Post Energy Symmetry Ratio (PPESR), and Pre/Post Tap Symmetry Ratio (PPTSR).

19. At least one non-transitory computer readable storage medium according to claim 12, wherein the database of suspected impairments includes a known impairment response for each of the suspected impairments in the database.

20. At least one non-transitory computer readable storage medium according to claim 19, wherein the computer program instructions, when executed by the at least one processor, cause the at least one processor to populate the database of suspected impairments with known impairment responses.