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

• US 20060141971A1
• Filed: 02/16/2006
• Published: 06/29/2006
• 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.
• Granted Patent: US 7,334,253 B2
• Time in Patent Office: Days
• US Class Current: 455/296
• 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 is disclosed for maintaining the integrity of a communication system. The method comprises detecting common path distortion (CPD) and periodic impulse/burst (PIB) noise in a received signal in the communication system. After isolating the CPD and PIB noise, ingress noise in the received signal is identified. Isolating the CPD and PIB noise thus prevents improper classification of CPD and PIB noise as ingress noise. Operating parameters of the communication system are then adapted in accordance with the identified ingress noise, the detected CPD and/or the detected PIB noise.

Claims

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

isolating common path distortion (CPD) in a received signal in the communication system;

isolating periodic impulse/burst (PIB) noise in the received signal;

identifying ingress noise in the received signal after isolating the CPD and PIB noise, thereby preventing improper classification of CPD and PIB noise as ingress noise; and

adapting operating parameters of the communication system in accordance with the identified ingress noise, the CPD and/or the PIB noise.

2. The method of claim 1, wherein the identifying step further comprises:

performing a fast Fourier transform on the received signal;

further isolating random impulse/burst (RIB) noise in the received signal; and

characterizing time domain characteristics of the ingress noise after isolating the RIB noise in the received signal, thereby preventing improper classification of RIB noise as ingress noise.

3. The method of claim 1, wherein the isolating CPD step further comprises:

characterizing the CPD in the received signal;

storing the CPD characterization;

performing a fast Fourier transform on the received signal to generate a transformed signal;

comparing an energy value within predetermined frequency bins of the transformed signal with a first threshold value to determine whether CPD is present; and

reporting any CPD to a system manager.

4. The method of claim 3, wherein the characterizing the CPD step further comprises:

obtaining a measured CPD spectrum that indicates a plant amplifier imbalance;

deriving a simulated CPD spectrum caused by plant oxidation;

comparing the measured CPD spectrum with the simulated CPD spectrum to characterize the source of the CPD.

5. The method of claim 3, further comprising:

correlating the transformed signal with the stored CPD characterization to generate a correlation;

comparing the correlation to a second threshold value to determine whether additional CPD is present; and

reporting any additional CPD to the system manager.

6. The method of claim 1, wherein the isolating CPD step further comprises:

identifying frequency bins in the received signal where CPD is expected;

measuring energy in frequency bins where CPD is expected;

measuring energy in frequency bins where CPD is not expected;

comparing the energy in frequency bins where CPD is expected with the energy in frequency bins where CPD is not expected to determine whether CPD is present.

7. The method of claim 1, wherein the isolating PIB noise step further comprises:

performing a time domain to frequency domain conversion on the received signal;

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

detecting a periodic signal within the frequency ranges.

8. The method of claim 1, wherein the adapting step further comprises updating an ingress cancellation filter to account for identified ingress noise.

9. The method of claim 1, wherein the adapting step further comprises not scheduling data transmission during intervals where PIB noise is expected.

10. The method of claim 1, wherein the adapting step further comprises scheduling lower priority transmissions during expected PIB noise intervals.

11. 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 the analog receiver that converts the analog data into digitized data;

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

a processor coupled to said FFT module that examines the converted digitized data to isolate common path distortion (CPD) and periodic impulse/burst (PIB) noise in a received signal in a communication channel of the communication system and, after isolating CPD and PIB noise, that identifies ingress noise; and

a system manager coupled to the processor that adapts operating parameters of the communication system in accordance with the identified ingress noise, CPD and/or PIB noise.

12. The system of claim 11, wherein the FFT module further performs a fast Fourier transform on the received signal;

and the processor further isolates random impulse/burst (RIB) noise in the received signal and then characterizes time domain characteristics of the ingress noise, thereby preventing improper classification of RIB noise as ingress noise.

13. The system of claim 11, wherein the processor characterizes the CPD in the received signal and stores the CPD characterization;

and wherein the FFT module performs a fast Fourier transform on the received signal to generate a transformed signal; and

wherein the processor further compares an energy value within predetermined frequency bins of the transformed signal with a first threshold value to determine whether CPD is present, and reports any CPD to a system manager

14. The system of claim 13, wherein the processor further obtains a measured CPD spectrum that indicates a plant amplifier imbalance and derives a simulated CPD spectrum caused by plant oxidation;

and wherein the processor further compares the measured CPD spectrum with the simulated CPD spectrum to characterize the source of the CPD.

15. The system of claim 13, wherein the processor further correlates the transformed signal with the stored CPD characterization to generate a correlation;

compares the correlation to a second threshold value to determine whether additional CPD is present; and

reports any additional CPD to the system manager.

16. The system of claim 11, wherein the processor further identifies frequency bins in the received signal where CPD is expected;

measures energy in frequency bins where CPD is expected and in frequency bins where CPD is not expected; and

compares the energy in frequency bins where CPD is expected with the energy in frequency bins where CPD is not expected to determine whether CPD is present.

17. The system of claim 11, wherein to further isolate PIB noise the FFT module performs a time domain to frequency domain conversion on the received signal;

and the processor computes a pulse width and a time between pulses for the received signal within one or more frequency ranges to detect a periodic signal within the frequency ranges.

18. The system of claim 11, wherein the system manager updates an ingress cancellation filter to account for identified ingress noise.

19. The system of claim 11, wherein the system manager does not schedule data transmission during intervals where PIB noise is expected.

20. The system of claim 11, wherein the system manager schedules lower priority transmissions during expected PIB noise intervals.