Anti-Geolocation

• US 9,201,132 B2
• Filed: 05/02/2012
• Issued: 12/01/2015
• Est. Priority Date: 04/15/2011
• Status: Active Grant

• Current Assignee: Ziva Corporation
• Original Assignee: Ziva Corporation
• Inventors: Hsu, Mark, Smith, David, Rode, Jeremy, Husain, Anis, Achour, Maha
• Primary Examiner(s): Nguyen, Leon-Viet
• Assistant Examiner(s): Hassan, Sarah
• Application Number:
  US13/462,514
• Publication Number:
  US 20120328037A1
• Time in Patent Office: 1,308 Days
• US Class Current: 1/1
• CPC Class Codes: G01S 1/725 Marker, boundary, call-sign or like beacons transmitting signals not carrying directional information
• CPC Class Codes: G01S 7/282 Transmitters
• CPC Class Codes: G01S 7/4814 of transmitters alone
• CPC Class Codes: H04B 7/0413 MIMO systems

Abstract

Methods, apparatus, and articles of manufacture make Geolocation of a source transmitter more difficult or impossible. Scatterers common to a source transmitter and an intended receiver are identified using a variety of techniques, such as iterative time reversal (ITR) and Singular Value Decomposition (SVD) of a scatter matrix. The source transmitter then uses time reversal and knowledge of the signatures of the scatterers to focus its transmissions on one or more of the scatterers, instead of the intended receiver. The source transmitter may have multiple antennas or antenna elements. The source transmitter and/or the intended receiver may include antenna elements with Near-Field Scatterers to enable spatial focusing below the diffraction limit at the frequencies of interest. The source transmitter may be a plurality of ad hoc nodes cooperating with each other.

Claims

1. A method of transmitting data from a first radio frequency communication system to a second radio frequency communication system, the method comprising steps of:

receiving by a plurality of antennas of the first radio frequency communication system waveforms that resulted from sounding environment using one or more channel sounding bursts transmitted from the second radio frequency communication system, the waveforms comprising reflections of the one or more channel sounding bursts from one or more scatterers;

processing the waveforms using time-reversal and Singular Value Decomposition to (1) select a first selected scatterer from the one or more scatterers, and (2) determine first signatures for launching from the plurality of antennas a first transmission temporally and spatially focused on the first selected scatterer, each first signature corresponding to a different antenna of the plurality of antennas;

convolving first data with said each first signature to obtain first transmission waveforms, a first transmission waveform per antenna of the plurality of antennas; and

transmitting the first transmission waveforms from the antennas of the plurality of antennas, each first transmission waveform transmitted through the antenna corresponding to said each first transmission waveform, so that the first data is temporally and spatially focused on the first selected scatterer.

2. A method according to claim 1, wherein the step of processing comprises processing in frequency domain.

3. A method according to claim 2, wherein the step of processing in the frequency domain comprises:

assembling a scatter matrix from the waveforms obtained in the step of receiving;

transforming the scatter matrix into frequency domain;

conjugating and applying Singular Matrix Decomposition to the scatter matrix in the frequency domain, to identify the first signatures in the frequency domain; and

transforming the first signatures to time domain.

4. A method according to claim 2, wherein the step of processing in the frequency domain comprises:

transforming the waveforms into the frequency domain;

assembling a scatter matrix in the frequency domain from the waveforms in the frequency domain;

conjugating and applying Singular Matrix Decomposition to the scatter matrix in the frequency domain, to identify the first signatures in the frequency domain; and

transforming the first signatures to time domain.

5. A method according to claim 1, wherein the step of processing comprises step of processing in the time domain, the step of processing in the time domain comprising time-reversal.

6. A method according to claim 1, wherein the first selected scatterer is the strongest scatterer.

10. A method according to claim 1, wherein the first communication system comprises a plurality of ad hoc nodes movable relative to each other and synchronized with each other, each ad hoc node of the plurality of ad hoc nodes comprising at least one antenna of the plurality of antennas.

7. A method of transmitting data from a first radio frequency communication system to a second radio frequency communication system, the method comprising steps of:

receiving by a plurality of antennas of the first radio frequency communication system waveforms that resulted from sounding environment using one or more channel sounding bursts transmitted from the second radio frequency communication system, the waveforms comprising reflections of the one or more channel sounding bursts from a plurality of scatterers;

processing the waveforms using time-reversal and Singular Value Decomposition to (1) select a first selected scatterer from the plurality of scatterers, (2) determine first signatures for launching from the plurality of antennas a first transmission temporally and spatially focused on the first selected scatterer, each first signature corresponding to a different antenna of the plurality of antennas, (3) select a second selected scatterer from the plurality of scatterers, the second selected scatterer being different from the first selected scatterer, and (4) determine second signatures for launching from the plurality of antennas a second transmission temporally and spatially focused on the second selected scatterer, each second signature corresponding to a different antenna of the plurality of antennas;

convolving first data with said each first signature to obtain first transmission waveforms, a first transmission waveform per antenna of the plurality of antennas;

transmitting the first transmission waveforms from the antennas of the plurality of antennas, each first transmission waveform transmitted through the antenna corresponding to said each first transmission waveform, so that the first data is temporally and spatially focused on the first selected scatterer;

convolving second data with said each second signature to obtain second transmission waveforms, a second transmission waveform per antenna of the plurality of antennas; and

transmitting the second transmission waveforms from the antennas of the plurality of antennas, each second transmission waveform transmitted through the antenna corresponding to said each second transmission waveform, so that the second data is temporally and spatially focused on the second selected scatterer.

8. A method according to claim 7, wherein the step of transmitting the first transmission waveforms is performed concurrently with the step of transmitting the second transmission waveforms.

9. A method according to claim 7, wherein the step of transmitting the first transmission waveforms is performed before the step of transmitting the second transmission waveforms.

11. A radio frequency communication system, comprising:

at least one transmitter;

at least one receiver;

a plurality of antennas coupled to the at least one transmitter and the at least one receiver; and

at least one processor coupled to the at least one transmitter and the at least one receiver, to control operation of the at least one receiver and the at least one transmitter, the at least one processor configured to execute code to cause the radio frequency communication system to;

receive by the plurality of antennas waveforms that resulted from sounding environment using one or more channel sounding bursts transmitted from an intended receiver, the waveforms comprising reflections of the one or more channel sounding bursts from one or more scatterers;

process the waveforms using time-reversal and Singular Value Decomposition to (1) select a first selected scatterer from the one or more scatterers, and (2) determine first signatures for launching from the plurality of antennas a first transmission temporally and spatially focused on the first selected scatterer, each first signature corresponding to a different antenna of the plurality of antennas;

convolve first data with said each first signature to obtain first transmission waveforms, a first transmission waveform per antenna of the plurality of antennas; and

transmit to the intended receiver the first transmission waveforms from the antennas of the plurality of antennas, each first transmission waveform transmitted through the antenna corresponding to said each first transmission waveform, so that the first data is temporally and spatially focused on the first selected scatterer.

12. A radio frequency communication system according to claim 11, wherein the at least one processor is further configured to execute code to cause the radio frequency communication system to process the waveforms using time-reversal and Singular Value Decomposition in frequency domain by:

assembling a scatter matrix from the waveforms;

transforming the scatter matrix into frequency domain;

conjugating and applying Singular Matrix Decomposition to the scatter matrix in the frequency domain, to identify the first signatures in the frequency domain; and

transforming the first signatures to time domain.

13. A radio frequency communication system according to claim 11, wherein the at least one processor is further configured to execute code to cause the radio frequency communication system to process the waveforms using time-reversal and Singular Value Decomposition in frequency domain by:

transforming the waveforms into the frequency domain;

assembling a scatter matrix in the frequency domain from the waveforms in the frequency domain;

conjugating and applying Singular Matrix Decomposition to the scatter matrix in the frequency domain, to identify the first signatures in the frequency domain; and

transforming the first signatures to time domain.

14. A radio frequency communication system according to claim 11, wherein the at least one processor is further configured to execute code to cause the radio frequency communication system to process the waveforms using time-reversal and Singular Value Decomposition in time domain.

15. A radio frequency communication system according to claim 11, wherein the first selected scatterer is the strongest scatterer.

17. A radio frequency communication system according to claim 11, wherein the radio frequency communication system comprises a plurality of ad hoc nodes movable relative to each other and synchronized with each other, at least one antenna of the plurality of antennas per ad hoc node of the plurality of ad hoc nodes.

16. A radio frequency communication system comprising:

at least one transmitter;

at least one receiver;

a plurality of antennas coupled to the at least one transmitter and the at least one receiver; and

at least one processor coupled to the at least one transmitter and the at least one receiver, to control operation of the at least one receiver and the at least one transmitter, the at least one processor configured to execute code to cause the radio frequency communication system to;

receive by the plurality of antennas waveforms that resulted from sounding environment using one or more channel sounding bursts transmitted from an intended receiver, the waveforms comprising reflections of the one or more channel sounding bursts from a plurality of scatterers;

process the waveforms using time-reversal and Singular Value Decomposition to (1) select a first selected scatterer from the plurality of scatterers, (2) determine first signatures for launching from the plurality of antennas a first transmission temporally and spatially focused on the first selected scatterer, each first signature corresponding to a different antenna of the plurality of antennas, (3) select a second selected scatterer from the plurality of scatterers, the second selected scatterer being different from the first selected scatterer, and (4) determine second signatures for launching from the plurality of antennas a second transmission temporally and spatially focused on the second selected scatterer, each second signature corresponding to a different antenna of the plurality of antennas;

convolve first data with said each first signature to obtain first transmission waveforms, a first transmission waveform per antenna of the plurality of antennas;

convolve second data with said each second signature to obtain second transmission waveforms, a second transmission waveform per antenna of the plurality of antennas;

transmit to the intended receiver the first transmission waveforms from the antennas of the plurality of antennas, each first transmission waveform transmitted through the antenna corresponding to said each first transmission waveform, so that the first data is temporally and spatially focused on the first selected scatterer; and

transmit the second transmission waveforms from the antennas of the plurality of antennas, each second transmission waveform transmitted through the antenna corresponding to said each second transmission waveform, so that the second data is temporally and spatially focused on the second selected scatterer.

18. A method of transmitting data from a first radio frequency communication system to a second radio frequency communication system, the method comprising:

receiving by a plurality of antennas of the first radio frequency communication system waveforms that resulted from sounding environment using one or more channel sounding bursts transmitted from the second radio frequency communication system, the waveforms comprising reflections of the one or more channel sounding bursts from one or more scatterers;

step for processing the waveforms using time-reversal and Singular Value Decomposition to (1) select a first selected scatterer from the one or more scatterers, and (2) determine first signatures for launching from the plurality of antennas a first transmission temporally and spatially focused on the first selected scatterer, each first signature corresponding to a different antenna of the plurality of antennas;

convolving first data with said each first signature to obtain first transmission waveforms, a first transmission waveform per antenna of the plurality of antennas; and

transmitting the first transmission waveforms from the antennas of the plurality of antennas, each first transmission waveform transmitted through the antenna corresponding to said each first transmission waveform, so that the first data is temporally and spatially focused on the first selected scatterer.