Assistance to a mobile SPS receiver

• US 8,013,788 B2
• Filed: 08/31/2006
• Issued: 09/06/2011
• Est. Priority Date: 09/05/2005
• Status: Active Grant

• Current Assignee: Cambridge Positioning Systems Limited (Qualcomm, Inc.)
• Original Assignee: Cambridge Positioning Systems Limited (Qualcomm, Inc.)
• Inventors: Duffett-Smith, Peter James, Pratt, Anthony Richard
• Primary Examiner(s): Issing; Gregory C
• Application Number:
  US11/991,430
• Publication Number:
  US 20090160703A1
• Time in Patent Office: 1,832 Days
• Field of Search: 342/357.43, 342/357.41, 342/357.27
• US Class Current: 342/357.41
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/06 employing an initial estimate of the location of the receiver as aiding data or in generating aiding data
• CPC Class Codes: G01S 19/50 whereby the position solution is constrained to lie upon a particular curve or surface, e.g. for locomotives on railway tracks

Abstract

A method is described, for use with an SPS mobile terminal receiver 102, of providing a compact assistance vector to initialize and constrain the computation of the terminal'"'"'s location within a region of validity. The compact assistance vector is provided to a computing node 108 able also to obtain measurements from a mobile terminal satellite positioning system receiver within said region. For a known reference point 104 within the region, the range or ranges from the reference point to one or more satellites 101 of the satellite positioning system are obtained. The range or ranges are represented by a number or numbers of ranging code repeat intervals in a limited resolution format. The compact assistance vector is created from the representation or representations of ranging code repeat intervals and transferred to the computing node 108. The compact assistance vector can then be used to initialize a location computation for the SPS mobile terminal receiver 102.

Claims

1. A method of computing the location of a mobile terminal satellite positioning system receiver, said computation using measurements made by said receiver of satellite transmission ranging codes, the method comprising

obtaining for a known reference point within a region of validity, the range or ranges from the reference point to one or more satellites of the satellite positioning system;

creating a representation of each range, in a limited resolution format, as a number related to the number of satellite transmission ranging code repeat intervals, wherein said representation comprises fractions of integers of ranging code repeat intervals in transit;

creating a compact assistance vector from each said representation of ranging code repeat intervals;

transferring said compact assistance vector to a computing node;

obtaining at said computing node the measurements from the receiver when within the region; and

using said measurements and said compact assistance vector to initialise and constrain a location computation of said receiver.

2. A method according to claim 1, further including computing a location solution for the mobile terminal which includes the step of constraining the solution to be consistent with the information contained within the compact assistance vector.

3. A method according to claim 1, including the step of obtaining further measurements made by said receiver for the in-view satellites, and using this information with the original measurements and the compact assistance vector to determine the location of the mobile terminal.

4. A method according to claim 1, wherein the range or ranges from the known reference point to each satellite are measured.

5. A method according to claim 4, wherein the range or ranges are obtained from one or more additional satellite positioning system receivers.

6. A method according to a claim 1, wherein the ranges from the known reference point to each satellite are calculated using parameters of the satellite orbits.

7. A method according to claim 1, wherein the compact assistance vector is structured to allow selection between more than one region of validity.

8. A method according to claim 1, wherein a plurality of compact assistance vectors corresponding to different regions of validity are enjoined to create a single compact assistance entity.

9. A method according to claim 1, wherein the computing node executes a set of instructions which calculates the position of the mobile terminal satellite positioning system receiver using the measurements made by the receiver and assisted by the compact assistance vector.

10. A method according to claim 1, wherein the measurements made by the mobile terminal satellite positioning system receiver are sent to the computing node by a radio link.

11. A method according to claim 1, wherein said computation is iterative, and for each new position computed via said iterative computation, the number of ranging code repeat intervals between each satellite and the mobile terminal satellite positioning system receiver is computed and is compared with the compact assistance vector to ensure that the solution is valid.

12. A method according to claim 1, wherein the compact assistance vector is transferred to the computing node by a point-to-point link, or by a two-way communications link, or by broadcasting.

13. A method according to claim 1, further including:

obtaining for said known reference point one or more satellite clock bias values relative to the satellite positioning system time reference;

combining said range or ranges and satellite clock bias or biases; and

producing an enhanced compact assistance vector.

14. A method according to claim 13, wherein the ranges are corrected for clock biases before being converted into the enhanced compact assistance vector.

15. A method according to claim 13, wherein the clock biases are sent separately as additional elements of the assistance vector.

16. A method according to claim 13, wherein, for a respective satellite, the current clock bias error, after conversion to its equivalent in distance, is subtracted from the measured range, and the corrected value is used to construct the element of the enhanced compact assistance vector appropriate to that satellite.

17. A method according to claim 1, further including:

determining the period during which the compact assistance vector, or enhanced compact assistance vector, remains valid,

constructing a validity information vector from said determination;

transferring the validity information vector to the computing node; and

using the validity information vector to modify or reject the compact assistance vector or enhanced compact assistance vector.

18. A method according to claim 17, wherein a plurality of time values is included for each element of the compact assistance vector or enhanced compact assistance vector in the validity information vector to extend further the time over which the data in a given compact assistance vector or enhanced compact assistance vector can be used.

19. A method according to claim 1, wherein the or another computing node uses the acquired information to determine the time at which the compact assistance vector becomes valid for each SPS satellite and known reference point individually or in groups.

20. A method according to claim 1, wherein the or another computing node further determines the time at which the compact assistance vector ceases to be valid.

21. A method according to claim 1, wherein the period of validity of the assistance vector is extended beyond the original validity period through the provision of extra information in the assistance vector concerning the rate of change of the integer and fractional number of ranging code sequences in transit.

22. A method according to a claim 1, wherein the compact assistance vector is derived from a network of reference receivers.

30. A method according to claim 1, wherein the fractions of integers are selected from the group comprising ½

, ⅓

, ¼

, . . . , 1/n of ranging code repeat intervals, where n is an integer.

23. A system for computing the location of a mobile terminal satellite positioning system receiver receiving satellite transmission ranging codes, said computation using measurements made by said receiver when located within a region of validity, the system including

means for providing the computing node with measurements from the mobile terminal satellite positioning system receiver when within the region;

means for obtaining for a known reference point within said region, the range or ranges from the reference point to one or more satellites of the satellite positioning system;

means for creating a representation of each range, in a limited resolution format as a number or numbers related to the number of satellite transmission ranging code repeat intervals;

means for creating a compact assistance vector from each said representation of ranging code repeat intervals;

means for transferring said compact assistance vector to a computing node; and

means for initialising and constraining a location computation using said compact assistance vector,

wherein the means for representing the range by a number of ranging code repeat intervals in a limited resolution format includes means for representing integers using fractions of integers of ranging code repeat intervals in transit.

24. A system according to claim 23, wherein the means for providing the computing node with measurements from the mobile terminal satellite positioning system receiver within said region includes components of one or more of a radio, cable, or network link.

25. A system according to claim 23, wherein the mobile terminal SPS receiver or mobile terminal includes the computing node.

26. A system according to claim 23, wherein the means for obtaining for a known reference point within said region, the range or ranges from the reference point to one or more satellites of the satellite positioning system includes one or more of a reference receiver located at or near the reference point, or a network of receivers, or calculating means for using known orbital parameters.

27. A system according to claim 23, wherein the means for creating the compact assistance vector from said representation or representations of ranging code repeat intervals includes a processor executing a set of instructions.

28. A system according to claim 23, wherein the means for transferring said compact assistance vector to the computing node includes components of one or more of a radio, cable, or network link.

29. A system according to claim 23, wherein the fractions of integers are selected from the group comprising ½

, ⅓

, ¼

, . . . , 1/n of ranging code repeat intervals, where n is an integer.