Identification and isolation of radio signals for a wireless location system

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 βc/βd; 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 βc/βd, 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 (βc/βd) 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 βc/βd; 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 βc/βd; 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 βc/βd; 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.