Interference detection, identification, extraction and reporting

• US 6,704,378 B2
• Filed: 03/08/2002
• Issued: 03/09/2004
• Est. Priority Date: 04/28/1999
• Status: Expired due to Term

• Current Assignee: ISCO International Inc.
• Original Assignee: ISCO International Inc.
• Inventors: Willetts, Mark N., Jagger, Charles E., Tobia, Micolino
• Primary Examiner(s): BAYARD, EMMANUEL
• Application Number:
  US10/093,904
• Publication Number:
  US 20020154614A1
• Time in Patent Office: 732 Days
• Field of Search: 375/259, 375/278, 375/285, 375/296, 375/346, 455/134, 455/135, 455/150, 455/154, 455/161.1, 455/161.3, 455/164, 455/434, 455/200.1, 455/266, 455/226.2
• US Class Current: 375/346
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04B 1/71 the interference being narrowband interference
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10
• CPC Class Codes: H04B 2001/1063 using a notch filter
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04B 2201/709718 Determine interference
• CPC Class Codes: H04B 7/005 Control of transmission; Equalising
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 24/04 Arrangements for maintaining operational condition
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 28/04 Error control
• CPC Class Codes: H04W 28/16 Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
• CPC Class Codes: H04W 28/20 Negotiating bandwidth
• CPC Class Codes: H04W 52/243 taking into account interferences
• CPC Class Codes: H04W 52/245 taking into account received signal strength
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 72/541 : using the level of interference
• CPC Class Codes: H04W 72/542 : using measured or perceived quality
• CPC Class Codes: H04W 88/02 : Terminal devices
• CPC Class Codes: H04W 88/08 : Access point devices

Abstract

An adaptive notch filter (ANF) module selectively filters a received wideband communication signal to eliminate narrowband interference that lies within the frequency spectrum of the wideband communication signal. To determine the presence of narrowband interference, the ANF module scans various known narrowband channels that lie within the frequency spectrum of the wideband communication signal and determines signal strengths for each of the narrowband channels. The signal strengths from the narrowband channels are compared to a threshold that is derived from the narrowband signal strengths. Narrowband channels having signal strengths that are greater than the threshold are determined to have interference.

Claims

1. A method of detecting and eliminating narrowband interference in a wideband communication signal having a frequency bandwidth with narrowband channels disposed therein, wherein guard bands having guard band frequencies adjacent the frequency bandwidth, the method comprising:

scanning at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels;

determining a threshold based on the signal strengths in at least some of the narrowband channels;

scanning the guard band frequencies to determine guard band signal strengths; and

filtering a guard band frequency when the guard band signal strength exceeds the threshold.

2. The method of claim 1, further comprising the step of compensating the guard band signal strengths by a compensation factor.

3. The method of claim 2, wherein compensating the guard band signal strengths comprises decreasing the guard band signal strengths by an amount that the guard band signal strengths will be attenuated by a filter of a wideband receiver.

4. The method of claim 2, wherein the compensation factor is based on a frequency response of a receiver filter.

5. The method of claim 4, wherein filtering the guard band frequency comprises filtering the guard band frequency when the guard band signal strength that has been compensated by the compensation factor exceeds the threshold.

6. The method of claim 1, wherein determining the threshold comprises determining an average of at least some of the signal strengths in at least some of the narrowband channels.

7. The method of claim 6, wherein determining the threshold comprises not including a number of the largest signal strengths when determining the average of at least some of the signal strengths in at least some of the narrowband channels.

8. The method of claim 7, wherein determining the threshold comprises adding an offset to the average of at least some of the signal strengths in at least some of the narrowband channels.

9. A system adapted to detect and eliminate narrowband interference in a wideband communication signal having a frequency bandwidth with narrowband channels disposed therein, wherein guard bands having guard band frequencies are adjacent the frequency bandwidth, the system comprising:

a scanner adapted to scan at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels;

a notch module adapted to receive the wideband communication signal and to selectively remove narrowband interference from the wideband communication signal to produce a filtered wideband communication signal; and

a controller coupled to the scanner and to the notch module, wherein the controller is adapted to control the scanner to scan at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels, to determine a threshold based on the signal strengths in at least some of the narrowband channels, to control the scanner to scan the guard band frequencies to determine guard band signal strengths and to control the notch module to selectively filter a guard band frequency when the guard band signal strength exceeds the threshold.

10. The system of claim 9, wherein the controller is adapted to compensate the guard band signal strength by a compensation factor.

11. The system of claim 10, wherein the controller is adapted to compensate the guard band signal by decreasing the guard band signal strength by an amount that the guard band signal strength will be attenuated by a filter a wideband receiver.

12. The system of claim 10, wherein the compensation factor is based on a frequency response of a receive filter.

13. The system of claim 12, wherein the controller is adapted to filter the guard band frequency when the guard band signal strength that has been compensated by the compensation factor exceeds the threshold.

14. The system of claim 9, wherein the controller is adapted to determine the threshold by determining an average of at least some of the signal strengths in at least some of the narrowband channels.

15. The system of claim 9, wherein the notch module is a first notch module and the filtered wideband communication signal is a first filtered wideband communication signal, the system further comprising a second notch module adapted to receive the first filtered wideband communication signal from the first notch module and to selectively filter the first filtered wideband communication signal at a frequency corresponding to a narrowband channel having a signal strength that exceeds the threshold to produce a second filtered wideband communication signal.

16. A method of detecting and eliminating narrowband interference in a wideband communication signal having a frequency bandwidth with narrowband channels disposed therein, the method comprising:

scanning at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels;

determining a threshold based on the signal strengths in at least some of the narrowband channels;

identifying narrowband channels having signal strengths exceeding the threshold;

identifying narrowband channels having temporary interference; and

filtering the wideband communication signal at a frequency corresponding to a narrowband channel having a signal strength exceeding the threshold, but not filtering the narrowband channels identified as having temporary interference.

17. The method of claim 16, wherein narrowband channels are identified as having temporary interference based on how long the signal strengths of the narrowband channels have exceeded the threshold.

18. The method of claim 16, wherein narrowband channels are identified as having temporary interference if the signal strength of the narrowband channel has not exceeded threshold longer than about 20 milliseconds.

19. A system adapted to detect and eliminate narrowband interference in a wideband communication signal having a frequency bandwidth with narrowband channels disposed therein, the system comprising:

a scanner adapted to scan at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels;

a notch module adapted to receive the wideband communication signal and to selectively remove narrowband interference from the wideband communication signal to produce a filtered wideband communication signal; and

a controller coupled to the scanner and to the notch module, wherein the controller is adapted to operate in conjunction with the scanner to determine a threshold based on the signal strengths in at least some of the narrowband channels, to identify narrowband channels having signal strengths exceeding the threshold, to identify narrowband channels having a temporary interference and to control the notch module to filter the wideband communication signal at a frequency corresponding to an identified narrowband channel having a signal strength exceeding the threshold, but not to filter the narrowband channels having temporary interference.

20. The system of claim 19, wherein the controller is adapted to identify narrowband channels as having temporary interference based on how long the signal strengths of the narrowband channels have exceeded the threshold.

21. The system of claim 19, wherein the controller is adapted to identify narrowband channels as having temporary interference if the signal strength of the narrowband channel has not exceeded the threshold longer than about 20 milliseconds.

22. A method of detecting and eliminating narrowband interference in a wideband communication signal having a frequency bandwidth with narrowband channels disposed therein, the method comprising:

scanning at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels in an order representative of a probability that the narrowband channels will have interference;

determining a threshold based on the signal strengths in at least some of the narrowband channels;

identifying narrowband channels having signal strengths exceeding the threshold; and

filtering the wideband communication signal at a frequency corresponding to an identified narrowband channel having signal strengths exceeding the threshold.

23. The method of claim 22, wherein the probability that the narrowband channels will have interference is based on historical data.

24. A system adapted to detect and eliminate narrowband interference in a wideband communication signal having a frequency bandwidth with narrowband channels disposed therein, the system comprising:

a scanner adapted to scan at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels in an order representative of a probability that the narrowband channels will have interference;

a notch module adapted to receive the wideband communication signal and to selectively remove narrowband interference from the wideband communication signal to produce a filtered wideband communication signal; and

a controller coupled to the scanner and to the notch module, wherein the controller is adapted to operate in conjunction with the scanner to determine a threshold based on the signal strengths in at least some of the narrowband channels, to identify narrowband channels having signal strengths exceeding the threshold and to control the notch module to filter the wideband communication signal at a frequency corresponding to an identified narrowband channel having a signal strength exceeding the threshold.

25. The system of claim 24, wherein the controller is adapted to determine the probability that the narrowband channels will have interference based on historical data.

26. A method of detecting and eliminating narrowband interference in a wideband communication signal having a frequency bandwidth with narrowband channels disposed therein, the method comprising:

scanning at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels;

determining a threshold based on the signal strengths in at least some of the narrowband channels;

storing a list of narrowband channels having signal strengths that exceed the threshold;

identifying a type of interference source based on the list of narrowband channels having signal strengths that exceed the threshold; and

filtering the wideband communication signal at a frequency corresponding to an identified narrowband channel having a signal strength exceeding the threshold, wherein the filtering is based on the type of interference source identified.

27. The method of claim 26, comprising selecting a filter for filtering the wideband communication signal based on the bandwidth of the interference source.

28. The method of claim 27, wherein a narrowband filter is used to filter a narrowband interference source.

29. The method of claim 27, wherein the bandwidth of the filter used for filtering the wideband communication signal is about the bandwidth of the interference source.

30. A system adapted to detect and eliminate narrowband interference in a wideband communication signal having a frequency bandwidth with narrowband channels disposed therein, the system comprising:

a scanner adapted to scan at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels in an order representative of a probability that the narrowband channels will have interference;

a notch module adapted to receive the wideband communication signal and to selectively remove narrowband interference from the wideband communication signal to produce a filtered wideband communication signal; and

a controller coupled to the scanner and to the notch module, wherein the controller is adapted to store a list of narrowband channels having signal strengths that exceed the threshold, to identify a type of interference source based on the list of narrowband channels having signal strengths that exceed the threshold and to control the notch module to filter the wideband communication signal at a frequency corresponding to an identified narrowband channel having a signal strength exceeding the threshold, wherein the filter used by the notch module is based on the type of interference source identified.

31. The system of claim 30, wherein the controller is adapted to select a filter for filtering the wideband communication signal based on the bandwidth of the interference source.

32. The system of claim 31, wherein the notch module uses a narrowband filter to filter a narrowband interference source.

33. The system of claim 31, wherein the filter bandwidth used by the notch module is about the bandwidth of the interference source.

34. A method of detecting and eliminating narrowband interference in a wideband communication signal having a frequency bandwidth with narrowband channels disposed therein, the method comprising:

scanning at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels;

determining a threshold based on the signal strengths in at least some of the narrowband channels;

storing a list of narrowband channels having signal strengths that exceed the threshold;

assigning filters to at least some of the identified narrowband channels having signal strengths exceeding the threshold; and

outputting to a network administrator the list of narrowband channels having signal strengths that exceed the threshold.

35. The method of claim 34, wherein the list is prioritized according to the signal strengths of the narrowband channels.

36. The method of claim 34, wherein the outputting is performed so that the network administrator may receive the information about at least some of the narrowband channels and may determine an identity of an interferer causing the narrowband signal strength to exceed the threshold.

37. The method of claim 36, wherein the network administrator determines the identity of an interferer by receiving an electronic indication of the identity of the interferer that is contained in the narrowband interference.

38. The method of claim 36, wherein the electronic indication is an electronic serial number of a mobile unit.

39. The method of claim 38, wherein the network administrator disables the interferer once the interferer is identified.

40. The method of claim 34, wherein the outputting is performed so that the network administrator may receive the information on at least some of the narrowband channels and may determine an if an interferer causing narrowband signal strength to exceed the threshold was attempting to place a call to an emergency service.

41. The method of claim 40, wherein the network administrator may determine if the interferer was attempting to place a call to an emergency service by intercepting a series of dialing digits transmitted by a mobile unit.