Method and apparatus for optimizing GPS-based position location in presence of time varying frequency error

• US 6,903,684 B1
• Filed: 03/31/2003
• Issued: 06/07/2005
• Est. Priority Date: 10/22/2002
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Simic, Emilija, Patrick, Christopher, Rowitch, Douglas
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): MULL, FRED H
• Application Number:
  US10/404,711
• Time in Patent Office: 799 Days
• Field of Search: 342/357.15, 342/357.1, 342/357.12
• US Class Current: 342/357.29
• CPC Class Codes: G01S 19/235 Calibration of receiver components

Abstract

Position determination accuracy of a wireless communication device may be negatively affected by a large unaccounted GPS doppler bias, which in turn may affect GPS doppler estimations and GPS doppler measurements conducted by the wireless communication device. The quality of GPS doppler measurements is very important for position location, because poor quality GPS doppler measurements may prevent the wireless communication device from acquiring satellites in the most sensitive modes with narrow frequency ranges, which results in reduced GPS pseudorange measurement yield. Large unaccounted GPS doppler bias also adversely affects position accuracy because of the adverse effect on the GPS code phase measurements time propagation to common time prior to their use in position location calculation. The same is true in the case of unaccounted CDMA code doppler, through the adverse effect on the AFLT code phase measurements time propagation to common time prior to their use in a position location engine. This effect is the biggest concern in the case of large search windows. Therefore, the present disclosure provides a method of optimizing GPS based position location in the presence of time-varying frequency error, including the steps of continuously measuring and/or calculating resulting GPS doppler bias and CDMA code doppler bias and then minimizing their adverse effects with regard to position location determination by re-centering GPS doppler search windows based on the GPS doppler bias value, as well as using GPS doppler bias and CDMA code doppler bias value to properly propagate GPS pseudorange and AFLT pilot phase measurements, respectively, to common time prior to their use in a position location engine.

Claims

1. A method of propagating AFLT pilot phase measurements to common time, comprising:

determining a CDMA channel dependent CDMA code doppler bias; and

accounting for the CDMA code doppler bias during time propagation of AFLT pilot phase measurements to common time, prior to reporting the AFLT pilot phase measurements to a position determining entity (PDE), or prior to using the AFLT pilot phase measurements in a position location engine in a wireless device.

2. The method of claim 1, wherein the propagation of AFLT pilot phase measurements is determined by continuously calculating the CDMA code doppler bias.

3. A method of optimizing GPS based position location in the presence of time-varying frequency error, comprising:

determining a GPS doppler bias value including determining a CDMA code doppler bias value;

centering a GPS doppler search window based on the GPS doppler bias value;

adjusting for the GPS doppler bias value during GPS code phase measurement time propagation to common time; and

adjusting for the CDMA code doppler bias value during AFLT code phase measurement time propagation to common time.

4. The method of claim 3, wherein the GPS doppler bias value is subtracted from a GPS measured doppler value prior to reporting the GPS measured doppler value to a position determining entity (PDE) or prior to using the GPS measured doppler value in a position location and/or a velocity engine in a wireless device.

5. A method of optimizing GPS based position location in the presence of time-varying frequency error, comprising:

determining a GPS doppler bias value;

centering a GPS doppler search window based on the GPS doppler bias value;

adjusting for the GPS doppler bias value during GPS code phase measurement time propagation to common time;

storing a CDMA channel independent GPS doppler bias value in a cellular device memory;

storing a calculated CDMA channel dependent GPS doppler and CDMA code doppler bias values, wherein the stored CDMA channel dependent CDMA code doppler bias value is used to propagate AFLT code phase measurements to common time; and

utilizing the CDMA channel independent GPS doppler bias value and the CDMA channel dependent GPS doppler bias value to re-center the GPS doppler search window for all search modes.

6. The method of claim 5, wherein the CDMA channel independent GPS doppler bias value and the CDMA channel dependent GPS doppler bias value are utilized to propagate GPS code phase measurement to common time.

7. A wireless communication device for optimizing GPS based position location in the presence of time varying frequency error, comprising:

a receiver for receiving signals from a base station, the signals including an indication of the timing of a GPS satellite;

a GPS receiver; and

a control processor coupled to the receiver and to the GPS receiver, and configured to use the received timing of the GPS satellite to determine a GPS search window center in doppler to search for the satellite;

wherein the GPS doppler search window center is determined by determining a total GPS doppler bias value and by centering the GPS doppler search window based on the total GPS doppler bias value, and wherein a CDMA channel dependent CDMA code doppler bias value is calculated and accounted for during time propagation of AFLT code phase measurements to common time prior to reporting the AFLT code phase measurements to a position determining entity (PDE) or using the AFLT code phase measurements in a wireless device position location engine.

8. A tangible data storage medium comprising executable data capable of causing a programmable device to perform the steps of:

determining a GPS doppler search window center for searching for a global positioning system (GPS) satellite, including the steps of;

determining a GPS doppler bias value including determining a CDMA code dopper bias value; and

centering a GPS doppler search window based on the GPS doppler bias value; and

accounting for GPS doppler and CDMA code doppler bias while propagating GPS pseudorange and AFLT pilot phase measurements, respectively, to common time.

9. The tangible data storage medium of claim 8, wherein the GPS doppler search window is determined by continuously measuring and/or calculating the GPS doppler bias value.

10. The tangible data storage medium of claim 8, further including the step of accounting for continuously measured and/or calculated GPS doppler bias and continuously calculated CDMA code doppler bias while propagating GPS pseudorange and AFLT pilot phase measurements, respectively, to common time.