Transfer of position information to a mobile terminal

• US 20080070589A1
• Filed: 10/30/2007
• Published: 03/20/2008
• Est. Priority Date: 04/28/2005
• Status: Active Grant

• Current Assignee: Cambridge Positioning Systems Limited (Qualcomm, Inc.)
• Original Assignee: Cambridge Positioning Systems Limited (Qualcomm, Inc.)
• Inventors: Pratt, Anthony, Duffett-Smith, Peter, Hansen, Paul
• Granted Patent: US 7,639,179 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 19/252 Employing an initial estimate of location in generating assistance data
• CPC Class Codes: G01S 19/51 Relative positioning
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/0054 of actual mobile position, i.e. position calculation on base station
• CPC Class Codes: G01S 5/0284 Relative positioning
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

The invention provides a method of combining satellite positioning system signals and position information derived from such signals in a mobile terminal, when these are available at a first location, with cellular communication signals and a method, system and apparatus for determining the approximate position information for the said mobile terminal when SPS signals are not available at a second location. The approximate position is determined in the mobile terminal only using a position difference vector derived from the cellular communication signals using time offsets and associated time-tags in a method based on the observed time difference of arrival. The computations of cellular position and position difference information are made within the network infrastructure. The invention provides for the security of the user as only position difference information is communicated over the air interface, or transmission time offset measurements which require non-transmitted information to determine a solution. In a further aspect of the invention, the approximate position information is used to provide position assistance information to an SPS receiver for the purposes of (a) satellite signal acquisition with reduced search time and/or (b) initial position information for the calculation of SPS location which thereby avoids the ‘integer ambiguity’ problem resulting from the repetitive nature of the SPS ranging signals.

Claims

1. A method of supplying position assistance information to a receiver of a satellite positioning system, contained within a mobile terminal having a timing reference, said mobile terminal being connected to a cellular communications network and also able to communicate via a bi-directional link with one or more remote devices capable of calculating position information, the method comprising the steps of:

(a) at a first location, where satellite signals are available, obtaining satellite position information of the mobile terminal from the satellite positioning system, storing said satellite position information within said terminal, measuring first time offsets, of the signals received by the terminal from a first plurality of transmitters of said cellular communications network, relative to each other or to the timing reference;

(b) sending said first time offset measurements to a remote device, calculating a first terminal cellular position information in the remote device using said time offset measurements, and storing said first terminal cellular position information;

(c) assigning a first time-tag to the first time offset measurements and storing said first time-tag;

(d) at a second location, where signals from the satellite positioning system are not adequately available, measuring second time offsets, of the signals received by the terminal from the first or a second plurality of the transmitters of said cellular communications network, relative to each other or to the timing reference;

(e) sending said second time offset measurements to, and calculating a second terminal cellular position information in, the or another remote device using said second time offset measurements;

(f) assigning a second time-tag to the second time offset measurements and storing said second time-tag;

(g) retrieving the first terminal cellular position information and the first time-tag and calculating a cellular average motion vector from the first and second terminal cellular position information and the first and second time-tags, and sending the cellular average motion vector to the mobile terminal;

(h) calculating in the terminal a position difference vector using said cellular average motion vector and the first and second time-tags, and adding said cellular position difference vector to the satellite position information stored within the mobile terminal and obtaining therefrom position assistance information of the mobile terminal at the second location;

(i) providing said position assistance information to the satellite receiver within the mobile terminal to aid the acquisition of satellite signals by the satellite receiver.

2. A method according to claim 1, wherein said first time offset measurements are stored.

3. A method according to claim 1, wherein said first and/or second time-tags are sent to one or more remote devices.

4. A method according to claim 1, wherein said first and/or said second time-tags are stored in the mobile terminal or in a device remote from the mobile terminal.

5. A method according to claim 1, wherein the timing reference is a signal sent to the mobile terminal.

6. A method according to claim 1, wherein the first and second time-tags include estimates of the instants at which the first and second time offsets respectively are made of the signals received by the mobile terminal from transmitters of the communications network.

7. A method according to claim 6, wherein the time-tags are assigned using a local timing reference within the mobile terminal and are sent to the remote device.

8. A method according to claim 6, wherein the time-tags are assigned in the remote device on receipt of a message from the mobile terminal.

9. A method according to claim 6, wherein the structure of the signals themselves received by the terminal from the transmitters of the communications network is used to assign the time-tags.

10. A method according to claim 1, further comprising, within the locale of the first location, obtaining multiple measurement information sets including measurements of the time offsets of the signals received by the mobile terminal from a plurality of the transmitters, assigning a time-tag to each measurement information set, obtaining motion information including a dynamical model of the motion of the terminal from the SPS measurements, removing the effects of the predicted motion from said measurement information sets using said motion information, and combining the corrected measurement information sets.

11. A method according to claim 1, further comprising, within the locale of the first location, obtaining multiple measurement information sets, including measurements of the time offsets of the signals received by the terminal from a plurality of the transmitters, from each of which measurement information set cellular position information is determined, assigning a time-tag to each of the measurement information sets, obtaining motion information including a dynamical model of the motion of the terminal from the SPS measurements, removing the effects of the predicted motion from said cellular position information using said dynamical model, and combining the corrected cellular position information to form an improved cellular position information.

12. A method according to claim 1, further comprising, within the locale of the first location, further combining the cellular position information with the motion information to obtain coherency indicator information which pertains to the degree of independence of the cellular measurement information sets from each other with respect to time or position, and using said coherency indicator information at the second location, to determine the extent of plural cellular measurement information sets used in the combining operation.

13. A method of determining the position of a mobile terminal of a satellite positioning system in which the satellite receiver is provided with calibrated terminal position assistance information in accordance with claim 1, and the position of the terminal is determined using at least one of the satellite signals.

14. A system for supplying position assistance information to a satellite positioning system receiver adapted to obtain, where possible, satellite position information of the mobile terminal from a satellite positioning system, the satellite positioning system receiver being contained within a mobile terminal, and said system including

a mobile terminal having

a timing reference

a receiver for connection to a cellular communications network,

means for communicating via a bi-directional link with one or more remote devices,

means for measuring first and second time offsets of the signals received by the terminal from one or more pluralities of transmitters of said cellular communications network, relative to each other or to the timing reference,

at respective first and second locations of said terminal,

storage means for storing said satellite position information, and

means for sending said first and second time offset measurements to a remote device;

means for assigning first and second time-tags to the time offset measurements;

storage means for storing the first and/or second time-tags;

a device for retrieving the first terminal cellular position information and the first and second time-tags, calculating a cellular average motion vector from the first and second terminal cellular position information and the first and second time-tags, and

means for sending the cellular average motion vector to the mobile terminal,

the mobile terminal further including

calculation means for calculating a position difference vector using said cellular average motion vector and the first and second time-tags, and

adding said cellular position difference vector to the satellite position information stored within the mobile terminal to obtain therefrom position assistance information of the mobile terminal at the second location; and

means for transferring said position assistance information to the satellite receiver within the mobile terminal to aid the acquisition of satellite signals by the satellite receiver.

15. A system according to claim 14, including a plurality of remote calculation devices for calculating terminal cellular position information using said time offset measurements.

16. A system according to claim 14, including a plurality of storage devices for storing terminal cellular position information.

17. A system according to claim 14, further including a storage means for said first and/or said second time-tags.

18. A system according to claim 14, wherein the timing reference is a signal sent to the mobile terminal.

19. A system according to claim 14, wherein the first and second time-tags include estimates of the instants at which the first and second time offsets respectively are made of the signals received by the mobile terminal from transmitters of the communications network.

20. A system according to claim 19, wherein the time-tags are assigned using a local timing reference within the mobile terminal and are sent to the remote device.

21. A system according to claim 19, wherein the time-tags are assigned in the remote device on receipt of a message from the mobile terminal.

22. A medium carrying a set of instructions which, when loaded into a terminal containing satellite positioning system components, enables the terminal to carry out the method of claim 14.

23. A mobile terminal satellite positioning system receiver having

a timing reference

a receiver for connection to a cellular communications network,

means for communicating via a bi-directional link with one or more remote devices,

means for measuring first and second time offsets of the signals received by the terminal from one or more pluralities of transmitters of said cellular communications network, relative to each other or to the timing reference, at respective first and second locations of said terminal,

storage means for storing said satellite position information,

means for sending said first and second time offset measurements to a remote device;

calculation means for calculating a position difference vector using a cellular average motion vector received from a remote device and first and second time-tags assigned to the time offset measurements, and adding said cellular position difference vector to the satellite position information stored within the mobile terminal to obtain therefrom position assistance information of the mobile terminal at the second location; and

means for transferring said position assistance information to the satellite receiver within the mobile terminal to aid the acquisition of satellite signals by the satellite receiver.

24. A mobile terminal according to claim 23, further including means for assigning first and second time-tags to the time offset measurements.

25. A mobile terminal according to claim 23, further including means for storing said first and second time-tags.