Interference detection, identification, extraction and reporting

• US 20020057751A1
• Filed: 04/06/2001
• Published: 05/16/2002
• Est. Priority Date: 04/28/1999
• Status: Active Grant

• Current Assignee: ISCO International Inc.
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Willetts, Mark N., Jagger, Charles E., Tobia, Micolino
• Granted Patent: US 7,317,698 B2
• Time in Patent Office: Days
• 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, 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;

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

determining if the assigned filters are operating properly; and

bypassing any of the assigned filters that are not operating properly.

2. The method of claim 1, wherein determining if the assigned filters are operating properly comprises reading outputs of the assigned filters.

3. The method of claim 2, wherein the assigned filters are determined not to be operating properly if narrowband interference is present at the outputs.

4. The method of claim 1, comprising coupling a known interferer into one of the assigned filters and determining if the known interferer is present at an output of the one of the assigned filters.

5. The method of claim 4, comprising bypassing the one of the assigned filters if the known interferer is present at the output of the known interferer.

6. 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;

a bypass switch adapted to bypass the notch module when the bypass switch is enabled; and

a controller coupled to the scanner and to the notch module, wherein the controller is adapted 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 control the notch module to filter the wideband communication signal at a frequency corresponding to a narrowband channel having a signal strength exceeding the threshold, to determine if the notch module is operating properly and to enable the bypass switch when the notch module is not operating properly.

7. The system of claim 6, further comprising an analog to digital converter coupled to an output of the notch module and to the controller, wherein the controller is adapted to control the analog to digital converter to read the output of the notch module and to determine if the notch module is operating properly based on information provided to the controller from the analog to digital converter.

8. The system of claim 7, wherein the notch filters are determined not to be operating properly if narrowband interference is present at the notch filter output.

9. The system of claim 8, further comprising an interference generator that is coupled to an input of the notch filter and to the controller, wherein the controller is adapted to control the interference generator to couple a known interferer into the notch module and to control the analog to digital converter to read the output of the notch module and to determine if the notch module is operating properly.

10. The system of claim 9, wherein the notch module is not operating properly if interference is present at the output of the notch module and wherein the controller controls the bypass switch to bypass the notch module when interference is present at the output of the notch module.

11. 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 fading narrowband channels having signal strengths that do not exceed the threshold and that were previously identified as exceeding the threshold, based on how long the identified narrowband channels have not exceeded the threshold; and

filtering the wideband communication signal at a frequency corresponding to a fading narrowband channel.

12. The method of claim 11, comprising de-assigning filters from narrowband channels having signal strengths below the threshold that are not identified as having fading interference.

13. The method of claim 11, wherein a narrowband channel is identified as a fading narrowband channel when its signal strength is below the threshold for less than 20 milliseconds.

15. The system of claim 14, wherein the controller is adapted to deassigning notch modules from filtering narrowband channels having signal strengths below the threshold that are not identified as having fading interference.

16. The system of claim 14, wherein the controller is adapted to identify a narrowband channel as a fading narrowband channel when its signal strength is below the threshold for less than 20 milliseconds.

14. 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 determining a threshold based on the signal strengths in at least some of the narrowband channels, to identify fading narrowband channels having signal strengths that do not exceed the threshold and that were previously identified as exceeding the threshold, based on how long the identified narrowband channels have not exceeded the threshold and to control the notch module to filter the wideband communication signal at a frequency corresponding to a fading narrowband channel.