Interference detection, characterization and location in a wireless communications or broadcast system

• US 9,121,923 B2
• Filed: 02/28/2012
• Issued: 09/01/2015
• Est. Priority Date: 12/30/2008
• Status: Active Grant

• Current Assignee: Skyhook Holding, Inc. (Liberty Broadband Corp.)
• Original Assignee: TruePosition Incorporated
• Inventors: Bull, Jeffrey F., Ward, Matthew L.
• Primary Examiner(s): Phan, Dao
• Application Number:
  US13/407,224
• Publication Number:
  US 20120154213A1
• Time in Patent Office: 1,281 Days
• Field of Search: 342/357.25, 342/357.47, 342/437, 342/442, 342/450, 342/457, 342/465, 455/456.1, 455/456.3
• US Class Current: 1/1
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: G01S 19/215 issues related to spoofing
• CPC Class Codes: G01S 5/0215 Interference
• CPC Class Codes: G01S 5/02526 using non-dedicated equipment, e.g. user equipment or crowd-sourcing
• CPC Class Codes: H04K 2203/18 for wireless local area networks or WLAN
• CPC Class Codes: H04K 3/224 with countermeasures at transmission and/or reception of the jammed signal, e.g. stopping operation of transmitter or receiver, nulling or enhancing transmitted power in direction of or at frequency of jammer
• CPC Class Codes: H04K 3/228 Elimination in the received signal of jamming or of data corrupted by jamming interference suppression in receivers H04B1/10
• CPC Class Codes: H04W 12/122 Counter-measures against attacks; Protection against rogue devices
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 28/04 Error control
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A Wide Area Sensor Network (WASN) is disclosed that utilizes wideband software defined radios (SDRs) to monitor RF energy over a wide frequency range, detect when critical frequencies are being jammed or otherwise interfered with, and locate the source of the interference so that the interference can be eliminated. The WASN may use one or more geolocation techniques In addition, the WASN may detect and locate unauthorized transmitters as well as estimate the transmitted power of authorized transmitters to assure they are not transmitting more power than authorized.

Claims

1. A method for detecting, classifying and locating radio frequency (RF) emitters in a wide area wireless communications network comprising a plurality of software defined radios, comprising:

detecting a presence of an interfering RF signal;

characterizing a received power of said interfering RF signal;

determining a bandwidth of said interfering RF signal;

locating the source of said interfering RF signal; and

synchronizing time and frequency between said software defined radios.

2. The method of claim 1, further comprising maintaining a historical database of RF signal information, the RF signal information representing RF signals received by said plurality of software defined radios for a predetermined duration over a predetermined bandwidth at a plurality of locations within said wide area wireless communications network.

3. The method of claim 1, wherein locating the source of said interfering RF signal is performed with a network-based wireless location technique.

4. The method of claim 1, further comprising moving at least one software defined radio to multiple locations in a serial fashion over a geographic area to be monitored.

5. The method of claim 1, wherein said synchronizing is performed using a GPS timing receiver.

6. The method of claim 1, wherein said characterizing comprises estimating an absolute power transmitted by the interfering RF signal by using propagation models of a local environment.

7. The method of claim 1, wherein at least one of the software defined radios is calibrated to measure absolute power of the received RF signals.

8. The method of claim 6, wherein said locating comprises estimating radiated power of the source of said interfering RF signal by determining the source'"'"'s power and determining a location as a function of characteristics of one or more software defined radios'"'"' receive antennae and an RF propagation model.

9. A method for detecting, classifying and locating radio frequency (RF) emitters in a wide area wireless communications network, comprising:

receiving time domain RF data corresponding to a signal to be monitored, said RF data representing said signal during a predetermined duration and over a predetermined bandwidth;

associating the received time domain RF data with a plurality of equal time intervals spanning said predetermined duration;

converting the time domain RF data associated with said equal time intervals into frequency domain data corresponding to a plurality of frequency bins;

determining at least one power characteristic for each of said frequency bins and for said signal to be monitored; and

for each of said frequency bins, determining, based on the power characteristic for the frequency bin, whether a source of interference is present.

10. The method of claim 9, wherein a source of interference is determined to be present when the at least one power characteristic for the frequency bin substantially differs from the at least one power characteristic of said signal to be monitored;

and further comprising locating the source of interference using a geolocation determination algorithm.

11. The method of claim 9, further comprising receiving information for the signal to be monitored, wherein said information comprises at least one of frequency channels occupied by said signal and a spectral density function.

12. The method of claim 9, further comprising passing the time domain RF data through digital downconverters to perform I/Q detection, bandlimiting, increasing bit resolution, and reducing a sample rate of the time domain RF data.

13. The method of claim 10, wherein said locating is performed using at least one of Time of Arrival (TOA), Time Difference of Arrival (TDOA), Angle of Arrival (AOA), Power of Arrival (POA), Power Difference of Arrival (PDOA), and Frequency Difference of Arrival (FDOA) techniques.

14. The method of claim 9, wherein said network comprises a software defined radio, and further comprising moving said software defined radio to multiple locations in a serial fashion over a geographic area to be monitored.

15. A method for detecting, classifying and locating radio frequency (RF) signals in a wide area wireless communications network comprising a software defined radio, comprising:

receiving time domain RF data corresponding to a signal to be monitored, said RF data representing said signal during a predetermined duration and over a predetermined bandwidth;

associating the received time domain RF data with a plurality of equal time intervals spanning said predetermined duration;

converting the time domain RF data associated with said equal time intervals into frequency domain data corresponding to a plurality of frequency bins;

determining at least one power characteristic for each of said frequency bins and for said signal to be monitored;

identifying frequency bins with at least one power characteristic above a noise floor;

for each of the identified frequency bins with at least one power characteristic above said noise floor, characterizing signals in the frequency bin; and

locating the characterized signals using a geolocation determination algorithm.

16. The method of claim 15, further comprising determining a location of an unlicensed white space transmitter and a maximum power that the white space transmitter can transmit without interfering with digital over-the-air television service.

17. The method of claim 16, further comprising moving said software defined radio to multiple locations in a serial fashion over a geographic area to be monitored.

18. The method of claim 15, further comprising receiving information for the signal to be monitored, wherein said information comprises at least one of frequency channels occupied by said signal, a spectral density function, and a catalog of legitimate signals.

19. The method of claim 18, further comprising comparing the characterized signals with said legitimate signals to identify illegitimate signals.

20. A system for detecting, classifying and locating radio frequency (RF) emitters in a wide area wireless communications network, the system comprising one or more software defined radios with a wide instantaneous bandwidth and tuning range, at least one processor communicatively coupled to the one or more software defined radios, and at least one memory communicatively coupled to said at least one processor, the at least one memory storing therein computer readable instructions, including:

instructions for receiving time domain RF data corresponding to a signal to be monitored, said RF data representing said signal during a predetermined duration and over a predetermined bandwidth;

instructions for associating the received time domain RF data with a plurality of equal time intervals spanning said predetermined duration;

instructions for converting the time domain RF data associated with said equal time intervals into frequency domain data corresponding to a plurality of frequency bins;

instructions for determining at least one power characteristic for each of said frequency bins and for said signal to be monitored;

instructions for determining whether a source of interference is present based on the power characteristics; and

instructions for locating the source of interference using a geolocation determination algorithm.