Method and apparatus for determining time in a satellite positioning system

• US 6,215,442 B1
• Filed: 04/16/1998
• Issued: 04/10/2001
• Est. Priority Date: 02/03/1997
• Status: Expired due to Term

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Inventors: Krasner, Norman F., Sheynblat, Leonid
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/062,232
• Time in Patent Office: 1,090 Days
• Field of Search: 342/357.05, 342/104, 342/352, 342/357.06, 701/213, 455/12.1
• US Class Current: 342/357.25
• CPC Class Codes: G01S 19/09 providing processing capability normally carried out by the receiver
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/246 involving long acquisition integration times, extended snapshots of signals or methods specifically directed towards weak signal acquisition
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain
• CPC Class Codes: G01S 19/396 Determining accuracy or reliability of position or pseudorange measurements
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/0045 Transmission from base station to mobile station G01S5/009 takes precedence
• CPC Class Codes: G01S 5/0063 of measured values, i.e. measurement on base station and position calculation on mobile
• CPC Class Codes: G04R 20/04 Tuning or receiving; Circuits therefor
• CPC Class Codes: G04R 20/06 Decoding time data; Circuits therefor

Abstract

A method and apparatus for determining a reference time associated with a satellite positioning system. In turn, the reference time, in one embodiment, may be used to determine other navigational information. Such navigational information may include, for example, the location/position of a satellite positioning system (SPS) receiver. In one embodiment, a relative velocity between an SPS receiver and a set of one or more satellites is used to determine an offset between time as indicated by the SPS receiver and the reference time. According to another embodiment of the invention, an error statistic is used to determine the reference time. According to yet another embodiment of the invention, two records, each representing at least a portion of a satellite message, are compared to determine time. In one implementation, the SPS receiver is mobile and operates in conjunction with a basestation to determine time and/or other navigational information according to one or a combination of the methods described.

Claims

1. A machine-implemented method for determining a reference time associated with a satellite positioning system, said method comprising:

estimating a position of an entity relative to a set of satellites, said estimation being associated with a first time measurement, wherein said first time measurement and said reference time differ by an offset;

determining a relative velocity of said set of satellites;

based on said relative velocity of said set of satellites and said estimated position, determining said offset between said first time measurement and said reference time; and

computing said offset by including said relative velocity of said set of satellites in a set of pseudorange residual computations.

2. The method of claim 1, wherein said relative velocity represents a relative velocity between said entity and said set of satellites.

3. The method of claim 1, wherein said relative velocity represents a relative velocity between said entity and a remote entity.

4. The method of claim 1, further comprising the step of iteratively repeating said pseudorange residual computations using a new set of data.

5. The method of claim 4, wherein each one of said repeated pseudorange residual computations provides a correction to said position of said entity and said offset.

6. A machine-implemented method for determining a reference time associated with a satellite positioning system, said method comprising:

an entity estimating a first value associated with a position of a set of satellites relative to said entity, said estimated first value being associated with a first time measurement, wherein said first time measurement associated with said values and said reference time associated with said satellite positioning system differ by an offset;

calculating an error statistic for said first value; and

based on said error statistic, determining said offset between said first time measurement and said reference time associated with said satellite positioning system;

wherein said first value comprises a pseudorange residual value, and said error statistic includes a sum of squares of said pseudorange residual value.

7. The method of claim 6, wherein said sum of squares of said pseudorange residual value is weighted by a weight factor.

8. A method for determining a time associated with a satellite positioning system, said method comprising the machine-implemented steps of:

an entity estimating a plurality of values associated with at least one of a relative range and a relative position between said entity and a set of satellites, wherein each of said plurality of values is associated with a respective time of measurement, wherein each time of measurement and said time associated with said satellite positioning system differ by a first offset;

determining a first set of error statistic values using each time of measurement associated with one of said plurality of values;

altering each time of measurement by a second offset;

determining a second set of error statistic values using said altered time of measurement; and

based on said second set of error statistic values, determining said first offset.

9. The method of claim 8, wherein said step of determining said first offset comprises the step of determining a linear convergence of said second error statistic.

10. The method of claim 9, wherein said second error statistic comprises a unit variance based on said plurality of values and said second offset.