Method and apparatus for detection and classification of impairments on a RF modulated network

• US 7,024,680 B2
• Filed: 11/16/2001
• Issued: 04/04/2006
• Est. Priority Date: 11/16/2000
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Howard, Daniel H.
• Primary Examiner(s): Nguyen, Lee
• Application Number:
  US09/988,065
• Publication Number:
  US 20020086641A1
• Time in Patent Office: 1,600 Days
• Field of Search: 725/107, 725121-125, 455/67.11, 455/67.13, 455/67.15, 455/423, 455/424
• US Class Current: 725/107
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0006 by adapting the transmission format
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/1829 Arrangements specially adapted for the receiver end
• CPC Class Codes: H04L 1/1887 Scheduling and prioritising arrangements
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 2001/0093 Point-to-multipoint

Abstract

A method and apparatus for detecting and classifying RF impairments on the upstream path of a communication system is provided. The detection system detects frequencies with common path distortion impairments, and a system manager avoids transmission over those frequencies or adapts transmissions accordingly. Subsequently, periodic impairments on the upstream path are detected. Detection of periodic impairments triggers the system manager to schedule no traffic during impairment periods, schedule low priority traffic during impairment periods, and/or adjust the physical layer parameters of traffic transmitted during an impairment period in order to increase robustness only when necessary. Finally, non-periodic or random impairments are detected on the upstream path and global parameter changes are made to adapt to non-predictable impairments. Each of the impairment types is then further classified to assist an operator of the system in determining the physical source of the impairment.

Claims

1. A method for maintaining the integrity of a communication system, comprising:

detecting an impairment on a communication channel of the communication system;

characterizing said impairment as one of a plurality of impairment types, wherein said plurality of impairment types includes at least one non-periodic impairment type and one periodic impairment type; and

adapting operating parameters of the communication system in accordance with said characterization of said impairment.

2. The method of claim 1, wherein said detecting comprises:

performing a time domain to frequency domain conversion on a signal associated with the communication channel;

aggregating a signal magnitude in the frequency domain;

comparing said signal magnitude at a set of specified frequencies with threshold values each associated with a frequency from said set of specified frequencies; and

reporting a list of frequencies from said set of specified frequencies for which said signal magnitude of an individual frequency exceeds a threshold value associated with said individual frequency.

3. The method of claim 2, wherein said set of specified frequencies comprises 6 MHz, 12 MHz, 18 MHz, 24 MHz, 30 MHz, and 36 MHz.

4. The method of claim 3, wherein said set of specified frequencies further comprises 4.5 MHz, 7.5 MHz, 10.5 MHz, 13.5 MHz, 16.5 MHz, 19.5 MHz, 22.5 MHz, 25.5 MHz, 28.5 MHz, 31.5 MHz, 34.5 MHz, and 37.5 MHz.

5. The method of claim 1, wherein said detecting comprises:

performing a time domain to frequency domain conversion on a signal associated with the communication channel;

aggregating a signal magnitude in the frequency domain;

comparing said signal magnitude aggregated within specified frequency ranges with threshold values each associated with a frequency range from said specified frequency ranges; and

reporting a list of frequency ranges from said specified frequency ranges for which the signal magnitude of an individual frequency range exceeds a threshold value associated with said individual frequency range.

6. The method of claim 1, wherein said detecting comprises:

performing a time domain to frequency domain conversion on a signal associated with the communication channel;

computing a pulse width and a time between pulses for said signal within one or more frequency ranges; and

detecting a periodic signal within said one or more frequency ranges.

7. The method of claim 1, wherein said detecting comprises:

examining data packets from the communication channel;

determining whether said data packets contain data errors; and

detecting a period with which data packets containing data errors arrive from the communication channel.

8. The method of claim 1, wherein said adapting operating parameters comprises scheduling data transmissions at a frequency without said impairment.

9. A system for maintaining the integrity of a communication system comprising:

an analog receiver that receives analog data from the communication system;

an analog-to-digital converter coupled to said analog receiver that converts said analog data into digitized data;

a fast Fourier transform (FFT) processor coupled to said analog-to-digital converter that receives said digitized data and performs a time domain to frequency domain conversion of said digitized data; and

a processor coupled to said FFT processor that examines said converted digitized data to detect an impairment on a communication channel of the communication system and classify said impairment as one of a plurality of impairment types, wherein said plurality of impairment types includes at least one non-periodic impairment type and at least one periodic impairment type, and wherein said processor adapts operating parameters of the communication system in accordance with said characterization of said impairment.

10. The system of claim 9, wherein said processor detects said impairment by accumulating a magnitude of said digitized data over a period of time at one or more specified frequencies and examines said specified frequencies to determine whether a threshold has been exceeded.

11. The system of claim 10, wherein said specified frequencies comprise 6 MHz, 12 MHz, 18 MHz, 24 MHz, 30 MHz, and 36 MHz.

12. The system of claim 11, wherein said specified frequencies further comprise 4.5 MHz, 7.5 Mhz, 10.5 MHz, 13.5 MHz, 16.5 MHz, 19.5 MHz, 22.5 MHz, 25.5 MHz, 28.5 MHz, 31.5 MHz, 34.5 MHz, and 37.5 MHz.

13. The system of claim 9, wherein said processor detects said impairment by comparing a frequency spectrum comprising said digitized data with one or more stored frequency spectra.

14. The system of claim 9, wherein said processor detects said impairment by examining a frequency band of said digitized data, computes a pulse width and a time between pulses for a DC waveform in said frequency band, and tracks an impulse train from said DC waveform.

15. The system of claim 9, further comprising:

an upstream demodulator coupled to said analog-to-digital converter that demodulates said digitized data into demodulated data;

a media access controller coupled to said upstream demodulator that extracts data packets from said demodulated data; and

a memory coupled to said media access controller that stores said data packets in said memory;

wherein said processor detects said impairment by examining said data packets stored in said memory to identify contiguous groups of data packets with errors and data packets without errors and computing a burst period for said contiguous groups of data packets with errors.

16. The system of claim 15, wherein said processor schedules outgoing transmissions to not coincide with said burst period.

17. The system of claim 9, wherein said processor schedules data transmissions at a frequency without said impairment.

18. An apparatus for maintaining the integrity of a communication system comprising:

receiving means for receiving analog data from the communication system;

converting means for converting said analog data into digitized data;

transforming means for transforming said digitized data from a time domain to a frequency domain; and

processing means for examining said transformed digitized data to detect an impairment on a communication channel of the communication system and classify said impairment as one of a plurality of impairment types, wherein said plurality of impairment types includes at least one non-periodic impairment type and at least one periodic impairment type, and wherein said processing means adapts operating parameters of the communication system in accordance with said classification of said impairment.

19. The apparatus of claim 18, wherein said processing means detects said impairment by accumulating a magnitude of said digitized data over a period of time in one or more specified frequency ranges and examining said specified frequency ranges to determine whether a threshold has been exceeded.

20. The apparatus of claim 18, wherein said processing means detects said impairment by comparing a frequency spectrum comprising said digitized data with one or more frequency spectra.

21. The apparatus of claim 18, wherein said processing means detects said impairment by selecting a frequency band of said transformed data, computing a pulse width and a time between pulses for a DC waveform in said frequency band, and tracking an impulse train based on said pulse width and said time between pulses.

22. The apparatus of claim 18, further comprising:

demodulating means for demodulating said digitized data into demodulated data;

extracting means for extracting data packets from said demodulated data; and

storing means for storing said data packets;

wherein said processor means detects said impairment by examining said data packets stored in said storing means to identify contiguous groups of data packets with errors and data packets without errors and computing a burst period for said contiguous groups of data packets with errors.

23. The apparatus of claim 22, wherein said processing means schedules outgoing transmissions to not coincide with said burst period.

24. The apparatus of claim 18, wherein said processing means schedules data transmissions at a frequency without said impairment.