System and method for detecting ingress in a signal transmission system

• US 20050281344A1
• Filed: 06/22/2004
• Published: 12/22/2005
• Est. Priority Date: 06/22/2004
• Status: Abandoned Application

• Current Assignee: Scientific-Atlanta LLC (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta LLC (Cisco Systems, Inc.)
• Inventors: Wall, William E.
• Application Number:
  US10/873,804
• Publication Number:
  US 20050281344A1
• Time in Patent Office: Days
• US Class Current: 375/259
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04J 7/00 Multiplex systems in which the amplitudes or durations of the signals in individual channels are characteristic of those channels
• CPC Class Codes: H04L 1/00 Arrangements for detecting or preventing errors in the information received correcting synchronisation H04L7/00
• CPC Class Codes: H04Q 11/0071 Provisions for the electrical-optical layer interface
• CPC Class Codes: H04Q 2011/0083 Testing; Monitoring

Abstract

A system and method for detecting ingress on shared media is presented. In one embodiment, among others, an input signal is selectively attenuated at each source site using a pseudo-random pattern, thereby amplitude modulating at low level the signal in a pseudo-random manner. Each encoded signal from each of the source sites is combined on shared media connected to a headend. The headend receives a composite signal comprising all of the individual source site signals and extracts the source site information using the pseudo-random pattern, thereby determining which of the source sites is the source of ingress.

Claims

1. A system for identifying signal source locations, comprising:

a clock generator configured to generate a synchronization signal;

a plurality of encoding devices, wherein each of the plurality of encoding devices is configured to generate a unique code in response to the synchronization signal, wherein each of the plurality of encoding devices is further configured to encode a signal using the generated unique code, wherein each of the encoded signals comprises a plurality of words arranged in a pseudo-random fashion, wherein each of the encoded signals is associated with a signal source location;

a medium configured to mix the plurality of encoded signals to produce a composite signal;

a receiver configured to receive the composite signal;

a spectrum analyzer configured to generate a digitized frequency spectrum from the received composite signal;

an multiple-code generator configured to generate a plurality of orthogonal codes in response to the synchronization signal, wherein each of the plurality of orthogonal codes is correlated to a different one of the encoded signals from the plurality of encoding devices, wherein each of the plurality of orthogonal codes comprises words arranged in a pseudo-random fashion,

a correlator configured to calculate a correlation coefficient between each of the plurality of orthogonal codes and the composite signal; and

a criteria engine configured to identify the signal source locations using the calculated correlation coefficients.

2. A system for identifying signal source locations, comprising:

a source location having a unique identifier; and

an attenuator configured to encode a signal by selectively attenuating time segments of the signal according to a pseudo-random pattern, wherein the pseudo-random pattern is related to the unique identifier.

3. The system of claim 2, wherein the time segments of the signal have a fixed duration.

4. The system of claim 2, further comprising a clock receiver configured to receive a synchronization signal, wherein the synchronization signal is configured to determine the duration of the time segments.

5. The system of claim 2, further comprising a code generator configured to generate the pseudo-random pattern.

6. A system for identifying signal source locations, comprising:

a receiver configured to receive a composite signal, wherein the composite signal comprises a plurality of encoded signals, wherein each of the plurality of encoded signals is correlated to a unique pseudo-random pattern associated with a signal source location; and

a headend configured to extract the signal source location from the received composite signal.

7. The system of claim 6, wherein the headend comprises spectrum analyzer configured to digitize the composite signal and produce a digitized spectrum from the composite signal.

8. The system of claim 7, wherein the headend further comprises a multiple-code generator configured to generate a plurality of codes, wherein each of the plurality of codes is correlated to each of the plurality of encoded signals.

9. The system of claim 8, wherein the headend further comprises a correlator configured to determine a plurality of correlation coefficients, wherein each of the plurality of correlation coefficients is indicative of a correlation between the each of the plurality of codes and the composite signal.

10. The system of claim 8, wherein the headend further comprises a clock generator configured to generate a synchronization signal, wherein the synchronization signal is configured to initiate the generation of the plurality of codes.

11. The system of claim 9, wherein the headend further comprises a comparator configured to compare each of the plurality of correlation coefficients with a threshold value to produce a plurality of result, wherein each of the plurality of results is selected from a group consisting of:

presence of ingress; and

absence of ingress.

12. The system of claim 11, wherein the headend further comprises a look-up table configured to identify signal source locations for each of the plurality of results.

13. A method for identifying signal source locations, comprising the steps of:

receiving a synchronization signal;

generating a plurality of unique codes in response to the received synchronization signal, wherein each of the plurality of unique codes is associated with a signal source location;

uniquely encoding each of a plurality of signals by selectively attenuating discrete time segments of each of the plurality of signals using the generated plurality of unique codes;

adding the uniquely encoded plurality of signals to produce a composite signal;

generating a plurality of orthogonal codes, wherein each of the plurality of orthogonal codes is correlated to each of the uniquely encoded plurality of signals;

calculating a plurality of correlation coefficients, each of the plurality of correlation coefficients indicative of a correlation between each of the plurality of orthogonal codes and the composite signal; and

identifying signal source locations using each of the calculated plurality of correlation coefficients.

14. A method for identifying signal source locations, comprising the steps of:

encoding a signal by selectively attenuating time segments of the signal according to a pseudo-random pattern, wherein the pseudo-random pattern is associated with a signal source location;

adding the encoded signal to a plurality of signals to produce a composite signal; and

extracting the signal source location from the composite signal.

15. The method of claim 14, wherein the step of encoding the signal further comprises the step of generating a unique code, wherein the unique code is associated with a signal source location.

16. The method of claim 14, wherein the time segments are fixed time intervals.

17. The method of claim 15, wherein the step of generating the unique code is responsive to receiving a synchronization signal.

18. The method of claim 17, wherein the selective attenuation of each time segment is responsive to a synchronization signal.

19. The method of claim 14, wherein the step of extracting the signal source location further comprises the step of receiving the composite signal.

20. The method of claim 19, further comprising the step of generating a plurality of orthogonal codes, wherein one of the plurality of orthogonal codes is correlated to the pseudo-random pattern.

21. The method of claim 20, further comprising the step of calculating a plurality of correlation coefficients, wherein each of the plurality of correlation coefficients is indicative of a correlation between each of the plurality of orthogonal codes and the received composite signal.

22. The method of claim 21, further comprising the step of comparing each of the calculated correlation coefficients with a threshold value to produce a result, wherein the result is selected from a group consisting of:

presence of ingress; and

absence of ingress.

23. The method of claim 22, further comprising the step of identifying signal source locations from the result of the comparing step.

24. A system for identifying signal source locations, comprising:

means for generating a plurality of unique codes, wherein each of the plurality of unique codes is associated with a signal source location;

means for uniquely encoding each of a plurality of signals by selectively attenuating discrete time segments of each of the plurality of signals using the plurality of unique codes;

means for adding the uniquely encoded plurality of signals to produce a composite signal;

means for generating a plurality of orthogonal codes, wherein each of the plurality of orthogonal codes is correlated to each of the uniquely encoded plurality of signals;

means for calculating a plurality of correlation coefficients, wherein each of the plurality of correlation coefficients is indicative of a correlation between each of the plurality of orthogonal codes and the composite signal; and

means for identifying signal source locations using each of the calculated plurality of correlation coefficients.

25. A system for identifying signal source locations, comprising:

means for encoding a signal by selectively attenuating time segments of the signal according to a pseudo-random pattern, wherein the pseudo-random pattern is associated with a signal source location;

means for adding the encoded signal to a plurality of signals to produce a composite signal; and

means for extracting the signal source location from the composite signal.

26. The system of claim 25, wherein the means for encoding the signal further comprises means for generating a unique code, wherein the unique code is associated with a signal source location.

27. The system of claim 26, wherein the means for generating the unique code is responsive to a synchronization signal.

28. The system of claim 25, wherein the means for extracting the signal source location further comprises means for receiving the composite signal.

29. The system of claim 28, further comprising means for generating a plurality of orthogonal codes, wherein one of the plurality of orthogonal codes is correlated to the pseudo-random pattern.

30. The system of claim 29, further comprising means for calculating a plurality of correlation coefficients, wherein each of the plurality of correlation coefficients is indicative of a correlation between each of the plurality of orthogonal codes and the composite signal.

31. The system of claim 30, further comprising means for comparing each of the correlation coefficients with a threshold value to produce a result, wherein the result is selected from a group consisting of:

presence of ingress; and

absence of ingress.

32. The system of claim 31, further comprising means for identifying signal source locations from the result.