Handoff between external and internal positioning systems

• US 6,768,909 B1
• Filed: 02/18/2000
• Issued: 07/27/2004
• Est. Priority Date: 02/18/2000
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Irvin, David R.
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): TORRES, MARCOS L
• Application Number:
  US09/507,554
• Time in Patent Office: 1,621 Days
• Field of Search: 455/436, 455/456, 455/457, 342/357.11, 701/213
• US Class Current: 455/456.1
• CPC Class Codes: G01S 19/48 by combining or switching between position solutions derived from the satellite radio beacon positioning system and position solutions derived from a further system
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236
• CPC Class Codes: G01S 5/0054 of actual mobile position, i.e. position calculation on base station
• CPC Class Codes: H04W 36/00 Hand-off or reselection arrangements
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A method and apparatus for determining the position of a mobile terminal using either an internal positioning system, such as a GPS receiver, or an external positioning system such as an external cellular positioning system. A handoff procedure is used to decide which positioning system is used to calculate the position of the mobile terminal. In one embodiment, the internal positioning system is preferred and the mobile terminal switches to the external positioning system only when the internal system is unavailable, and switches back when the internal system is functioning properly. Alternatively, the external positioning system is preferred and when it is unavailable the mobile terminal switches to the internal positioning system, but switches back to the external system when it is available. In one embodiment, the mobile terminal includes the internal positioning system, a transceiver, and a mobile terminal position controller. The mobile terminal position controller selects between the external and internal positioning systems depending on availability or other factors such as operator preference.

Claims

1. A method for conducting a handoff procedure between positioning systems used in determining a position for a mobile terminal in a cellular network, the method comprising:

disengaging a first positioning system when said first positioning system is unable to calculate the position of said mobile terminal;

instructing a second positioning system to engage and calculate the position of said mobile terminal; and

monitoring said first positioning system and, when said first positioning system is able to calculate the position of said mobile terminal, instructing the second positioning system to disengage and instructing said first positioning system to engage and calculate the position of said mobile terminal;

wherein one of said first positioning system and said second positioning system is an internal positioning system which calculates the position at the mobile terminal using radio signals from satellites, and the other of said first positioning system and said second positioning system is an external positioning system which calculates the position based on arrivals of a radio signal from the mobile terminal at a plurality of base stations.

2. The method according to claim 1, wherein said first positioning system is an external positioning system and said second positioning system is an internal positioning system.

3. The method according to claim 2, wherein said external positioning system is an external cellular positioning system.

4. The method according to claim 2, wherein said internal positioning system is an internal GPS receiver.

5. The method according to claim 2, wherein said external positioning system is an external cellular positioning system, and said internal positioning system is an internal GPS receiver.

6. The method according to claim 5, wherein instructing said external cellular positioning system further comprises transmitting an instruction message to said external cellular positioning system over a channel from said mobile terminal to said external cellular positioning system.

7. The method according to claim 6, wherein said channel is selected from the group consisting of a random access control channel, a fast access control channel, and a slow access control channel.

8. The method according to claim 6, wherein said instruction message is a short message of a short message service.

9. The method according to claim 5, wherein instructing said external cellular positioning system to engage and calculate the position of said mobile terminal is performed repeatedly.

10. The method according to claim 5, wherein instructing said external cellular positioning system to disengage when said external cellular positioning system is unable to calculate the position of said mobile terminal further comprises calculating which GPS satellites offer the highest probability for obtaining a first position fix, and sending information to said mobile terminal relating to which GPS satellites offer the highest probability for obtaining a first position fix.

11. The method according to claim 1, wherein said first positioning system is an internal positioning system and said second positioning system is an external positioning system.

12. The method according to claim 11, wherein said internal positioning system is an internal GPS receiver.

13. The method according to claim 11, wherein said external positioning system is an external cellular positioning system.

14. The method according to claim 11, wherein said external positioning system is an external cellular positioning system, and said internal positioning system is an internal GPS receiver.

15. The method according to claim 14, wherein instructing said external cellular positioning system to engage or disengage further comprises transmitting an instruction message to said external cellular positioning system over a channel from said mobile terminal to said external cellular positioning system.

16. The method according to claim 15, wherein said channel is selected from the group consisting of a random access control channel, a fast access control channel, and a slow access control channel.

17. The method according to claim 15, wherein said instruction message is a short message of a short message service.

18. The method according to claim 14, wherein instructing said external cellular positioning system to engage and calculate the position of the mobile terminal is performed repeatedly.

19. A mobile terminal usable in a cellular network, said mobile terminal comprising:

an internal positioning system which calculates, at the mobile terminal, a position of the mobile terminal using signals from satellites;

a transceiver for communicating via wireless signals with the cellular network, wherein the cellular network comprises an external positioning system which calculates, the position of the mobile terminal based on arrivals of the wireless signals at a plurality of base stations, said signals including data regarding the position of the mobile terminal as determined by at least one of the external and the internal positioning systems; and

a mobile terminal position controller, wherein said mobile terminal position controller determines the availability of one of the external and internal positioning systems, wherein said mobile terminal position controller selects the other of the positioning systems when said one positioning system is unavailable.

20. The mobile terminal of claim 19, wherein said mobile terminal position controller selects said internal positioning system when said internal positioning system is able to determine the position of said mobile terminal.

21. The mobile terminal of claim 19, wherein said mobile terminal position controller determines the position of said mobile terminal from the data included in said signal when said internal positioning system is unable to determine said position.

22. The mobile terminal of claim 19, further comprising a batter monitor, wherein the mobile terminal position controller selects the position of the mobile terminal from the data included in the signal when said battery monitor determines battery charge to be low.

23. The mobile terminal of claim 19, wherein said internal positioning system is a GPS receiver.

24. The mobile terminal of claim 19, wherein said wireless signals include data regarding the presence of external positioning systems in a cell of the cellular network which the mobile terminal is entering, and said mobile terminal position controller selects the position of the mobile terminal determined by the internal positioning system when said signal includes data indicating that no external positioning system is present in a cell of the cellular network which the mobile terminal is entering.

25. An external cellular positioning system for a cellular network, the external cellular positioning system comprising:

a plurality of cellular positioning receivers operable for monitoring transmissions from at least one mobile terminal, wherein the at least one mobile terminal comprises an internal positioning system which is operable to calculate, at the mobile terminal, using signals from satellites, a position for the at least one mobile terminal; and

a central positioning control site connected to the plurality of cellular positioning receivers, the central positioning control site operable to receive information regarding the transmissions from the plurality of cellular positioning receivers and calculate, at the central positioning control site, the position for the at least one mobile terminal, using the arrivals of the transmissions at the cellular positioning receivers;

wherein the external cellular positioning system is operable to receive over a channel and act on an instruction message from the at least one mobile terminal which selectively instructs the external cellular positioning system to engage and disengage based on the availability of the internal positioning system.

26. The system according to claim 25, wherein said channel is a random access control channel.

27. The system according to claim 25, wherein said channel is a fast access control channel.

28. The system according to claim 25, wherein said channel is a slow access control channel.

29. The system according to claim 25, wherein said instruction message is a short message of a short message service.