Method and apparatus for determining absolute time-of-day in a mobile-assisted satellite positioning system

1. A method of determining time-of-day in a mobile receiver, the method comprising:

obtaining expected pseudoranges to a plurality of satellites, said expected pseudoranges based on an initial position of said mobile receiver and an initial time-of-day;

obtaining expected line-of-sight data to said plurality of satellites;

measuring pseudoranges from said mobile receiver to said plurality of satellites;

computing update data for said initial time-of-day using a mathematical model relating said pseudoranges, said expected pseudoranges, and said expected line-of-sight data;

updating said initial time-of-day using said update data to compute a time-tag; and

transmitting said pseudoranges and said time-tag to a server in wireless communication with said mobile receiver.

2. The method of claim 1 , further comprising receiving acquisition assistance data at said mobile receiver from a server, wherein said expected pseudoranges and said expected line-of-sight data are obtained from said acquisition assistance data.

3. The method of claim 1 , wherein said computing update data for said initial time-of-day comprises: determining update data for a clock bias associated with said mobile receiver using said mathematical model.

4. The method of claim 3 , further comprising:

detecting bit transitions within satellite navigation data transmitted by at least one of said plurality of satellites; and

updating said initial time-of-day in response to said detected bit transitions and said clock bias update data.

5. The method of claim 1 , further comprising:

detecting bit transitions within satellite navigation data transmitted by at least one of said plurality of satellites;

decoding absolute time data from said satellite navigation data in response to said detected bit transitions; and

updating said initial time-of-day using said absolute time data.

6. The method of claim 5 , wherein said absolute time data comprises a time-of-week count message.

7. A method of determining time-of-day in a mobile receiver, the method comprising:

obtaining expected pseudoranges to a plurality of satellites, said expected pseudoranges based on an initial position of said mobile receiver and an initial time-of-day;

obtaining expected line-of-sight data to said plurality of satellites;

measuring pseudoranges from said mobile receiver to said plurality of satellites;

computing update data for said initial time-of-day using a mathematical model relating said pseudoranges, said expected pseudoranges, and said expected line-of-sight data;

measuring pseudorange rates at said mobile receiver;

obtaining almanac data; and

computing an approximate position of said mobile receiver using said pseudorange rates and said almanac data, wherein said expected line-of-sight data is obtained in response to said approximate position and said almanac data.

8. The method of claim 7 , further comprising:

updating said initial time-of-day using said update data to compute a time-tag; and

transmitting said pseudoranges and said time-tag to a server in wireless communication with said mobile receiver.

9. The method of claim 7 , further comprising: receiving acquisition assistance data at said mobile receiver from a server, wherein said expected pseudoranges and said expected line-of-sight data are obtained from said acquisition assistance data.

10. The method of claim 7 , wherein computing update data for said initial time-of-day comprises: determining update data for a clock bias associated with said mobile receiver using said mathematical model.

11. The method of claim 10 , further comprising:

detecting bit transitions within satellite navigation data transmitted by at least one of said plurality of satellites; and

updating said initial time-of-day in response to said detected bit transitions and said clock bias update data.

12. The method of claim 7 , further comprising:

detecting bit transitions within satellite navigation data transmitted by at least one of said plurality of satellites;

decoding absolute time data from said satellite navigation data in response to said detected bit transitions; and

updating said initial time-of-day using said absolute time data.

13. The method of claim 12 , wherein said absolute time data comprises a time-of-week count message.

14. A method of determining time-of-day in a mobile receiver, the method comprising:

obtaining expected pseudoranges to a plurality of satellites, said expected pseudoranges based on an initial position of said mobile receiver and an initial time-of-day;

obtaining expected line-of-sight data to said plurality of satellites;

measuring pseudoranges from said mobile receiver to said plurality of satellites;

computing update data for said initial time-of-day using a mathematical model relating said pseudoranges, said expected pseudoranges, and said expected line-of-sight data;

obtaining almanac data; and

obtaining an estimated position of said mobile receiver, wherein said expected line-of-sight data is obtained in response to said estimated position and said almanac data.

15. The method of claim 14 , further comprising:

computing an approximate position of said mobile receiver using said almanac data and said estimated position, wherein said expected line-of-sight data is obtained in response to said approximate position and said almanac data.

16. The method of claim 14 , further comprising:

updating said initial time-of-day using said update data to compute a time-tag; and

transmitting said pseudoranges and said time-tag to a server in wireless communication with said mobile receiver.

17. The method of claim 14 , further comprising: receiving acquisition assistance data at said mobile receiver from a server, wherein said expected pseudoranges and said expected line-of-sight data are obtained from said acquisition assistance data.

18. The method of claim 14 , wherein computing update data to said initial time-of-day step comprises: determining update data for a clock bias associated with said mobile receiver using said mathematical model.

19. The method of claim 18 , further comprising:

detecting bit transitions within satellite navigation data transmitted by at least one of said plurality of satellites; and

updating said initial time-of-day in response to said detected bit transitions and said clock bias update data.

20. The method of claim 14 , further comprising:

detecting bit transitions within satellite navigation data transmitted by at least one of said plurality of satellites;

decoding absolute time data from said satellite navigation data in response to said detected bit transitions; and

updating said initial time-of-day using said absolute time data.

21. The method of claim 20 , wherein said absolute time data comprises a time-of-week count message.

22. An apparatus for determining time-of-day in a mobile receiver, the apparatus comprising:

a wireless transceiver for obtaining acquisition assistance data from a server, said acquisition assistance data comprising expected pseudoranges to a plurality of satellites based on an initial position of said mobile receiver and an initial time-of-day;

a satellite signal receiver for measuring pseudoranges from said mobile receiver to said plurality of satellites;

a processor for obtaining expected line-of-sight data to said plurality of satellites and for computing update data for said initial time-of-day using a mathematical model relating said pseudoranges, said expected pseudoranges, and said expected line-of-sight data; and

a clock circuit, wherein said processor is further configured to calibrate said clock circuit using said update data.

23. The apparatus of claim 22 , wherein said processor is configured to obtain said expected line-of-sight data from said acquisition assistance data.

24. The apparatus of claim 22 , wherein said processor is further configured to compute update data from a clock bias associated with said satellite signal receiver using said mathematical model.

25. The apparatus of claim 24 , wherein said processor is further configured to detect bit transitions within satellite navigation data transmitted by at least one of said plurality of satellites and update said initial time-of-day in response to said detected bit transitions and said clock bias update data.

26. The apparatus of claim 22 , wherein said processor is further configured to decode absolute time data from satellite navigation data transmitted by at least one of said plurality of satellites and update said initial time-of-day using said absolute time data.

27. The apparatus of claim 26 , wherein said absolute time data comprises a time-of-week count message.

28. An apparatus for determining time-of-day in a mobile receiver, the apparatus comprising:

a wireless transceiver for obtaining acquisition assistance data from a server, said acquisition assistance data comprising expected pseudoranges to a plurality of satellites based on an initial position of said mobile receiver and an initial time-of-day;

a memory for storing almanac data associated with a constellation having said plurality of satellites;

a satellite signal receiver for measuring pseudoranges from said mobile receiver to said plurality of satellites and for measuring pseudorange rates; and

a processor for:

obtaining expected line-of-sight data to said plurality of satellites;

computing update data for said initial time-of-day using a mathematical model relating said pseudoranges, said expected pseudoranges, and said expected line-of-sight data;

computing an approximate position of said mobile receiver using said pseudorange rates and said almanac data; and

obtaining said expected line-of-sight data in response to said approximate position and said almanac data.

29. The apparatus of claim 28 , wherein said processor is configured to obtain said expected line-of-sight data from said acquisition assistance data.

30. The apparatus of claim 28 , wherein said processor is further configured to compute update data from a clock bias associated with said satellite signal receiver using said mathematical model.

31. The apparatus of claim 30 , wherein said processor is further configured to detect bit transitions within satellite navigation data transmitted by at least one of said plurality of satellites and update said initial time-of-day in response to said detected bit transitions and said clock bias update data.

32. The apparatus of claim 28 , wherein said processor is further configured to decode absolute time data from satellite navigation data transmitted by at least one of said plurality of satellites and update said initial time-of-day using said absolute time data.

33. The apparatus of claim 32 , wherein said absolute time data comprises a time-of-week count message.

34. An apparatus for determining time-of-day in a mobile receiver, the apparatus comprising:

a wireless transceiver for obtaining acquisition assistance data from a server, said acquisition assistance data comprising expected pseudoranges to a plurality of satellites based on an initial position of said mobile receiver and an initial time-of-day;

a memory for storing almanac data associated with a constellation having said plurality of satellites;

a satellite signal receiver for measuring pseudoranges from said mobile receiver to said plurality of satellites; and

a processor for:

obtaining expected line-of-sight data to said plurality of satellites;

computing update data for said initial time-of-day using a mathematical model relating said pseudoranges, said expected pseudoranges, and said expected line-of-sight data;

computing an approximate position of said mobile receiver using an estimated position of said mobile receiver and said almanac data; and

obtaining said expected line-of-sight data in response to said approximate position and said almanac data.

35. The apparatus of claim 34 , wherein said processor is configured to obtain said expected line-of-sight data from said acquisition assistance data.

36. The apparatus of claim 34 , wherein said processor is further configured to compute update data from a clock bias associated with said satellite signal receiver using said mathematical model.

37. The apparatus of claim 36 , wherein said processor is further configured to detect bit transitions within satellite navigation data transmitted by at least one of said plurality of satellites and update said initial time-of-day in response to said detected bit transitions and said clock bias update data.

38. The apparatus of claim 34 , wherein said processor is further configured to decode absolute time data from satellite navigation data transmitted by at least one of said plurality of satellites and update said initial time-of-day using said absolute time data.

39. The apparatus of claim 38 , wherein said absolute time data comprises a time-of-week count message.

40. A position location system, comprising:

a mobile receiver comprising:

a wireless transceiver;

a satellite signal receiver for measuring pseudoranges from said mobile receiver to a plurality of satellites; and

a processor; and

a server, in wireless communication with said mobile receiver, for transmitting acquisition assistance data to said mobile receiver, said acquisition assistance data comprising expected pseudoranges to said plurality of satellites based on an initial position of said mobile receiver and an initial time-of-day, wherein said processor is configured to obtain expected line-of-sight data to said plurality of satellites and to compute update data for said initial time-of-day using a mathematical model relating said pseudoranges, said expected pseudoranges, and said expected line-of-sight data; and wherein said wireless transceiver is configured to transmit said measured pseudoranges and said update data to said server.

41. The system of claim 40 , wherein said server is configured to locate position of said mobile receiver in response to said measured pseudoranges and said update data.