Locating the source of a wireless signal

• US 9,942,864 B2
• Filed: 11/22/2016
• Issued: 04/10/2018
• Est. Priority Date: 02/04/2015
• Status: Active Grant

• Current Assignee: Cognitive Systems Corp.
• Original Assignee: Cognitive Systems Corp.
• Inventors: Kravets, Oleksiy, Sherrat, Colin John
• Primary Examiner(s): Hua, Quan M
• Application Number:
  US15/359,530
• Publication Number:
  US 20170078989A1
• Time in Patent Office: 504 Days
• CPC Class Codes: G01S 5/02 using radio waves using satellite radio beacon systems for determining position G01S19/00
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04K 2203/16 for telephony
• CPC Class Codes: H04K 3/22 including jamming detection and monitoring
• CPC Class Codes: H04K 3/45 characterized by including monitoring of the target or target signal, e.g. in reactive jammers or follower jammers for example by means of an alternation of jamming phases and monitoring phases, called "look-through mode"
• CPC Class Codes: H04K 3/82 related to preventing surveillance, interception or detection
• CPC Class Codes: H04K 3/822 by detecting the presence of a surveillance, interception or detection
• CPC Class Codes: H04L 43/00 Arrangements for monitoring or testing data switching networks
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic
• CPC Class Codes: H04W 48/10 using broadcasted information
• CPC Class Codes: H04W 56/001 Synchronization between nodes
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 64/006 with additional information processing, e.g. for direction or speed determination
• CPC Class Codes: H04W 72/21 in the uplink direction of a wireless link, i.e. towards the network
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

In some aspects, a wireless-signal source locator system includes wireless sensor devices distributed at distinct locations over a geographic region. The wireless sensor devices are configured to passively monitor wireless communication network signals in the geographic region. Each wireless sensor device is configured to receive a source signal wirelessly transmitted by a source (e.g., a mobile device, etc.) and a reference signal (e.g., from a synchronization source). The wireless sensor devices can generate arrival-time data based on the source signal and the reference signal. The wireless-signal source locator system further includes a data analysis system configured to receive the arrival-time data from the wireless sensor devices and to identify a location of the source based on analyzing the arrival-time data generated by three or more of the wireless sensor devices.

Claims

1. A method of determining a location of a wireless source, the method comprising:

sending a synchronization signal to wireless sensor devices distributed at distinct locations over a geographic region, the wireless sensor devices configured to passively monitor wireless signals in the geographic region;

receiving wireless source signals collected by the wireless sensor devices after receiving the synchronization signal, each wireless source signal comprising a radio-frequency (RF) transmission from a wireless source in the geographic region, each wireless source signal detected by a respective wireless sensor device at a time indicated by the synchronization signal; and

identifying, at a data analysis system, a location of a wireless source in the geographic region based on cross-correlating the wireless source signals collected by three or more distinct wireless sensor devices,

wherein identifying the location of the wireless source in the geographic region is based on solving a system of equations, the system of equations comprising n equations;

cδ

τ

_ij=[|{right arrow over (r_b)}−

{right arrow over (r_l)}|+|{right arrow over (r_s)}−

{right arrow over (r_l)}|]−

[|{right arrow over (r_b)}−

{right arrow over (r_j)}|+|{right arrow over (r_s)}−

{right arrow over (r_j)}|]

where {right arrow over (r_s)}=(x_s, y_s, z_s)represents the location of the wireless source, {right arrow over (r_b)}=(x_b, y_b, z_b) represents a location of a base station, {right arrow over (r_l)}=(x_i, y_i, z_i) represents a location of the i-th wireless sensor device, {right arrow over (r_j)}=(x_j, y_j, z_j) represents a location of the j-th wireless sensor device, c represents the speed of light, and δ

τ

_ij represents a peak identified in a cross-correlation output.

2. The method of claim 1, wherein the synchronization signal indicates a synchronized start time when the wireless sensor devices begin recording the wireless source signals.

3. The method of claim 1, comprising identifying the location of the wireless source in the geographic region by:

cross-correlating respective pairs of the wireless source signals;

identifying one or more peaks in each of the cross-correlation outputs;

identifying arrival-time information based on the one or more peaks; and

identifying the location based on the arrival-time information.

4. The method of claim 2, wherein the synchronization signal indicates a synchronized end time when the wireless sensor devices finish recording the wireless source signals.

5. The method of claim 3, wherein cross-correlating respective pairs of the wireless source signals comprises applying a correlation function between S_i(t) and S_j(t), where S_n(t) represents the wireless source signal waveform received from an n-th wireless sensor device, i and j are indices of the respective wireless sensor device, and i≠

j.

6. The method of claim 1, wherein each wireless sensor device is a wireless spectrum-inspection device.

7. The method of claim 1, wherein the wireless sensor devices are configured to passively monitor cellular network signals formatted according to any of multiple distinct cellular network standards.

8. The method of claim 1, wherein passively monitoring wireless signals in the geographic region comprises monitoring wireless signals exchanged in a wireless communication network without requesting services from the wireless communication network.

9. The method of claim 1, wherein each wireless sensor device comprises:

an RF interface configured to detect RF signals in a local wireless environment about the wireless sensor device;

a signal analysis subsystem configured to process the RF signals; and

a communication interface configured to transmit data to a remote system.

10. A wireless-signal source locator system comprising:

wireless sensor devices distributed at distinct locations over a geographic region and configured to passively monitor wireless communication network signals in the geographic region, each wireless sensor device configured to;

receive a synchronization signal;

detect, at a time indicated by the synchronization signal, a wireless source signal comprising a radio-frequency (RF) transmission from a wireless source in the geographic region; and

transmit the wireless source signal; and

a data analysis system comprising one or more processors configured to identify a location of the wireless source based on cross-correlating the wireless source signals transmitted by three or more distinct wireless sensor devices,

wherein identifying the location of the wireless source in the geographic region is based on solving a system of equations, the system of equations comprising n equations;

cδ

τ

_ij=[|{right arrow over (r_b)}−

{right arrow over (r_l)}|+|{right arrow over (r_s)}−

{right arrow over (r_l)}|]−

[|{right arrow over (r_b)}−

{right arrow over (r_j)}|+|{right arrow over (r_s)}−

{right arrow over (r_j)}|]

where {right arrow over (r_s)}=(x_s, y_s, z_s) represents the location of the wireless source, {right arrow over (r_b)}=(x_b, y_b, z_b) represents a location of a base station, {right arrow over (r_l)}=(x_i, y_i, z_i) represents a location of the i-th wireless sensor device, {right arrow over (r_j)}=(x_j, y_j, z_j) represents a location of the j-th wireless sensor device, c represents the speed of light, and δ

τ

_ij represents a peak identified in a cross-correlation output.

11. The system of claim 10, wherein the synchronization signal indicates a synchronized start time when the wireless sensor devices begin recording the wireless source signals.

12. The system of claim 11, wherein the synchronization signal indicates a synchronized end time when the wireless sensor devices finish recording the wireless source signals.

13. The system of claim 10, wherein the data analysis system is configured to identify the location of the wireless source in the geographic region by:

cross-correlating respective pairs of the wireless source signals;

identifying one or more peaks in each of the cross-correlation outputs;

identifying arrival-time information based on the one or more peaks; and

identifying the location based on the arrival-time information.

14. The system of claim 13, wherein cross-correlating respective pairs of the wireless source signals comprises applying a correlation function between S_i(t) and S_j(t), where S_n(t) represents the wireless source signal waveform received from an n-th wireless sensor device, i and j are indices of the respective wireless sensor device, and i≠

j.

15. The system of claim 10, wherein each wireless sensor device is a wireless spectrum-inspection device.

16. The system of claim 10, wherein the wireless sensor devices are configured to passively monitor cellular network signals formatted according to any of multiple distinct cellular network standards.

17. The system of claim 10, wherein passively monitoring wireless signals in the geographic region comprises monitoring wireless signals exchanged in a wireless communication network without requesting services from the wireless communication network.

18. The system of claim 10, wherein each wireless sensor device comprises:

an RF interface configured to detect RF signals in a local wireless environment about the wireless sensor device;

a signal analysis subsystem configured to process the RF signals; and

a communication interface configured to transmit data to a remote system.