Identification and isolation of radio signals for a wireless location system

• US 8,737,452 B2
• Filed: 06/19/2012
• Issued: 05/27/2014
• Est. Priority Date: 06/19/2012
• Status: Active Grant

• Current Assignee: Skyhook Holding, Inc. (Liberty Broadband Corp.)
• Original Assignee: TruePosition Incorporated
• Inventors: Mia, Rashidus S.
• Primary Examiner(s): Nguyen, Leon-Viet
• Assistant Examiner(s): Hassan, Sarah
• Application Number:
  US13/527,289
• Publication Number:
  US 20130336366A1
• Time in Patent Office: 707 Days
• Field of Search: 375/148, 370/342, 370/332
• US Class Current: 375/148
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference

Abstract

In an overlay, network-based, Wireless Location System, LMUs typically co-located with BTSs, are used to collect uplink radio signaling for use in TOA, TDOA and/or AoA positioning methods. In a UMTS, the dual nature of the uplink allows for identification of the correct uplink signal even in the presence of co-channel interference from other UMTS mobile devices.

Claims

1. A method for identifying a signal-of-interest (SOI), comprising:

receiving the SOI at a reference sensor station;

providing a first reference signal based on a first component of the SOI received at the reference sensor station, and a second reference signal based on a second component of the SOI received at the reference sensor station;

receiving a signal comprising the SOI along with an interfering signal at a cooperative sensor station;

correlating the first reference signal and the second reference signal with the signal received at the cooperative sensor station;

providing a first correlation map representing the correlation of the first reference signal with the signal received at the cooperative sensor station, and providing a second correlation map representing the correlation of the second reference signal with the signal received at the cooperative sensor station;

based on the first correlation map, identifying first and second peaks;

based on the second correlation map, identifying third and fourth peaks;

determining a first value corresponding to a ratio of the first and third peaks and determining a second value corresponding to a ratio of the second and fourth peaks;

comparing the first and second values to a third value based on a ratio of predetermined gain factors β

c/β

d; and

identifying the SOI based on the value most closely matching the third value.

2. The method recited in claim 1, further comprising determining a time of arrival of the SOI at the cooperative sensor station.

3. The method recited in claim 1, wherein the SOI includes a user data part and a control data part.

4. The method recited in claim 3, wherein the SOI is transmitted by a mobile device over dual uplink channels using a dual channel phase shift keying digital modulation method in which coded user data are applied to an in-phase input of a quadrature phase shift keying (QPSK) modulator and control data are applied to a quadrature-phase input of the QPSK modulator, thereby resulting in physical uplink channels including a Dedicated Physical Data Channel (DPDCH) and a Dedicated Physical Control Channel (DPCCH).

5. The method recited in claim 4, wherein the first reference signal, DPDCH_REF, is based on the user data part of the SOI received at the reference sensor station, and the second reference signal, DPCCH_REF, is based on the control data part of the SOI received at the reference sensor station.

6. The method of claim 1, wherein the reference sensor station comprises a first location measuring unit (LMU).

7. The method of claim 6, wherein the cooperative sensor station comprises a second LMU.

8. A method for identifying a signal-of-interest (SOI) having a user data part and a control data part, wherein the SOI is transmitted by a mobile device over dual uplink channels using a dual channel phase shift keying digital modulation method in which coded user data are applied to an in-phase input of a quadrature phase shift keying (QPSK) modulator and control data are applied to a quadrature-phase input of the QPSK modulator, thereby resulting in physical uplink channels including a Dedicated Physical Data Channel (DPDCH) and a Dedicated Physical Control Channel (DPCCH), the method comprising:

receiving the SOI at a first, reference location measuring unit (LMU);

providing a first reference signal (DPDCH_REF) based on the user data part of the SOI received at the reference LMU, and a second reference signal (DPCCH_REF) based on the control data part of the SOI received at the reference LMU;

receiving a signal comprising the SOI along with an interfering signal at a second, cooperative LMU;

correlating the first reference signal, DPDCH_REF, and the second reference signal, DPCCH_REF, with the signal received at the cooperative LMU;

providing a first correlation map representing the correlation of the first reference signal, DPDCH_REF, with the signal received at the cooperative LMU, and providing a second correlation map representing the correlation of the second reference signal, DPCCH_REF, with the signal received at the cooperative LMU;

based on the first correlation map, identifying first and second peaks;

based on the second correlation map, identifying third and fourth peaks;

determining a first value corresponding to a ratio of the first and third peaks and determining a second value corresponding to a ratio of the second and fourth peaks;

comparing the first and second values to a third value based on a ratio of predetermined gain factors β

c/β

d, wherein the SOI is identified based on the value most closely matching the third value; and

determining a time of arrival of the SOI at the cooperative LMU.

9. The method recited in claim 8, wherein the method is carried out as part of an interference detection and mitigation process employed by a wireless location system (WLS).

10. The method recited in claim 9, wherein the interference detection and mitigation process is part of an overall process comprising the following:

a location request is initiated by the mobile device or a wireless communications network associated with the mobile device or WLS;

the WLS is tasked to locate the mobile device;

the WLS determines one or more LMUs suited to detect the received signal and serve as a reference LMU;

the WLS determines which LMUs are candidates for making timing measurements and functioning as cooperative LMUs;

while the mobile device is transmitting, the WLS instructs candidate reference LMU(s) and cooperative LMUs to collect a transmitted uplink SOI over a synchronized time window;

the candidate reference LMU(s) extracts the SOI reference signal in an environment with relatively small levels of interference present;

once the collected SOI is de-spread and demodulated at the candidate reference LMU(s), an evaluation of the collected SOI and the final selection of a reference LMU is made;

at the reference LMU, the SOI is compressed into a representative reference signal, and the reference signal and a reference LMU time of arrival timestamp are distributed to the cooperative LMUs;

cross-correlation in time and frequency domains with the reference signal is carried out at each cooperative LMU;

the interference detection and mitigation process is carried out;

the cooperative LMUs send timing measurements to the WLS where final mobile device position, velocity and/or confidence factors are determined; and

a final location response is sent back to the requestor.

11. A system for identifying a signal-of-interest (SOI), comprising:

a reference sensor station configured to receive the SOI and to provide a first reference signal based on a first component of the SOI and a second reference signal based on a second component of the SOI;

a cooperative sensor station configured to receive a signal comprising the SOI along with an interfering signal, and to correlate the first reference signal and the second reference signal with the signal received at the cooperative sensor station; and

means for identifying the SOI based on a ratio of predetermined gain factors (β

c/β

d) and the correlations of the first and second reference signals with the signal received at the cooperative sensor station.

12. The system recited in claim 11, wherein the means for identifying the SOI comprises:

means for providing a first correlation map representing the correlation of the first reference signal with the signal received at the cooperative sensor station, and providing a second correlation map representing the correlation of the second reference signal with the signal received at the cooperative sensor station;

means for identifying first and second peaks based on the first correlation map;

means for identifying third and fourth peaks based on the second correlation map;

means for determining a first value corresponding to a ratio of the first and third peaks and determining a second value corresponding to a ratio of the second and fourth peaks;

means for comparing the first and second values to a third value based on a ratio of predetermined gain factors β

c/β

d; and

means for identifying the SOI based on the value most closely matching the third value.

13. A non-transitory computer readable medium, comprising instructions for performing a computer-implemented process, comprising:

instructions for receiving a signal-of-interest (SOI) at a reference sensor station;

instructions for providing a first reference signal based on a first component of the SOI received at the reference sensor station, and a second reference signal based on a second component of the SOI received at the reference sensor station;

instructions for receiving a signal comprising the SOI along with an interfering signal at a cooperative sensor station;

instructions for correlating the first reference signal and the second reference signal with the signal received at the cooperative sensor station;

instructions for providing a first correlation map representing the correlation of the first reference signal with the signal received at the cooperative sensor station, and providing a second correlation map representing the correlation of the second reference signal with the signal received at the cooperative sensor station;

instructions for identifying first and second peaks;

instructions for identifying third and fourth peaks;

instructions for determining a first value corresponding to a ratio of the first and third peaks and determining a second value corresponding to a ratio of the second and fourth peaks;

instructions for comparing the first and second values to a third value based on a ratio of predetermined gain factors β

c/β

d; and

instructions for identifying the SOI based on the value most closely matching the third value.

14. A method for identifying a signal-of-interest (SOI), wherein the SOI includes a user data part and a control data part, comprising:

providing a first reference signal based on the user data part of the SOI and a second reference signal based on the control data part of the SOI;

correlating the first reference signal and the second reference signal with an interference-corrupted signal comprising the SOI along with an interfering signal;

providing a first correlation map representing the correlation of the first reference signal with the interference-corrupted signal, and providing a second correlation map representing the correlation of the second reference signal with the interference-corrupted signal;

based on the first correlation map, identifying first and second peaks;

based on the second correlation map, identifying third and fourth peaks;

determining a first value corresponding to a ratio of the first and third peaks and determining a second value corresponding to a ratio of the second and fourth peaks;

comparing the first and second values to a third value based on a ratio of predetermined gain factors β

c/β

d; and

identifying the SOI based on the value most closely matching the third value.

15. The method recited in claim 14, further comprising determining a time of arrival of the SOI at a cooperative sensor station.

16. The method recited in claim 14, wherein the SOI is transmitted by a mobile device over dual uplink channels using a dual channel phase shift keying digital modulation method in which coded user data are applied to an in-phase input of a quadrature phase shift keying (QPSK) modulator and control data are applied to a quadrature-phase input of the QPSK modulator, thereby resulting in physical uplink channels including a Dedicated Physical Data Channel (DPDCH) and a Dedicated Physical Control Channel (DPCCH).

17. The method recited in claim 16, wherein the first reference signal, DPDCH_REF, is based on the user data part of the SOI received at a reference sensor station, and the second reference signal, DPCCH_REF, is based on the control data part of the SOI received at the reference sensor station.