Methods and apparatuses for using mobile GPS receivers to synchronize basestations in cellular networks

• US 7,801,108 B2
• Filed: 01/29/2007
• Issued: 09/21/2010
• Est. Priority Date: 05/04/2000
• Status: Active Grant

• Current Assignee: Qualcomm, Inc., Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm, Inc.
• Inventors: Jolley, Edward V, Krasner, Norman F
• Primary Examiner(s): Appiah; Charles N
• Assistant Examiner(s): Rideout; William F
• Application Number:
  US11/668,384
• Publication Number:
  US 20070123248A1
• Time in Patent Office: 1,331 Days
• Field of Search: 370/350, 370/507, 370/515, 370/516, 455/456.1, 455/456.3, 455/456.6, 455/502, 455/524, 342/357.1, 342/357.09, 375/142
• US Class Current: 370/350
• CPC Class Codes: G01S 11/08 using synchronised clocks
• CPC Class Codes: H04B 7/2693 Centralised synchronisation, i.e. using external universal time reference, e.g. by using a global positioning system [GPS] or by distributing time reference over the wireline network
• CPC Class Codes: H04L 69/28 Timers or timing mechanisms used in protocols
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 4/029 Location-based management or tracking services
• CPC Class Codes: H04W 56/00 Synchronisation arrangements

Abstract

Methods and apparatuses for establishing time at a first basestation, and synchronizing the first basestation with other basestations in a cellular network. The method may be performed using a mobile (cellular communication) station that includes a satellite position system receiver. One method comprises determining a location of the mobile station, determining a time indicator that represents a time-of-day at the mobile station, wherein the time indicator is determined relative to a signal available at the first basestation, transmitting at least one of the position information and location, and transmitting the time indicator from the mobile station. The time indicator and at least one of the position information and the location are used to establish a time at the first basestation such that the first basestation is synchronized to other basestations in the cellular communication system. Other methods and apparatuses are also described for synchronizing basestations in a cellular network.

Claims

1. A method for synchronizing time between mobile stations and basestations in a communication system, said method comprising:

transmitting a communication signal having a marker from a basestation to a first mobile station;

receiving from the first mobile station a time indicator which represents a time-of-day the transmitted communication signal having the marker was received by the first mobile station and at least one of position information of the first mobile station or location of the mobile station;

determining a time at the basestation based on the time indicator which represents a time-of-day the transmitted communication signal having the marker was received by the first mobile station and at least one of the position information or the location; and

transmitting the time at the basestation to at least one other mobile station and synchronizing a time at the one other mobile station based on the time at the basestation and a propagation delay between the basestation and the one other mobile station.

2. The method as in claim 1 wherein the propagation delay between the basestation and the one other mobile station is based on the known location of the basestation and at least one of the position information or the location of the one other mobile station.

3. A method as in claim 1 wherein said position information at least comprises a pseudorange to a satellite and wherein said communication signal transmitted to the first mobile station is a cellular communication signal transmitted from said basestation to said first mobile station, and wherein said time indicator is associated with a marker in said signal.

4. A method as in claim 3 wherein said time indicator comprises at least one of a sampling of an SPS signal received by said SPS receiver and a time-of-day message in said SPS signal.

5. A method as claimed in claim 2 wherein said position information of the one other mobile station at least comprises a pseudorange to a satellite and wherein said communication signal transmitted to the one other mobile station is a cellular communication signal transmitted from said basestation to said one other mobile station, and wherein the one other mobile station does not receive time information from the satellite.

6. A method as in claim 3 wherein a location server receives the position information and determines the location and provides the position to the basestation.

7. A method as in claim 1 wherein the time at the basestation is determined based on the time indicator less the propagation delay plus a time difference between transmission of the communication signal with the marker and reception of the time indicator.

8. A method for synchronizing time between mobile stations and basestations in a communication system, said method comprising:

receiving a time indicator that represents a time-of-day at a first mobile station from said first mobile station, wherein said time indicator is determined relative to a signal which is available to said basestation;

determining a time at said basestation from said time indicator such that said basestation is synchronized to other basestations; and

transmitting the time at said basestation to at least one other mobile station and synchronizing a time at the at least one other mobile station based on the time at the basestation and a propagation delay between the basestation and the one other mobile station.

9. A method as in claim 8 wherein said signal is a cellular communication signal transmitted from said basestation.

10. A method as in claim 8 further comprising:

receiving a location of said one other mobile station, wherein said time at said one other mobile station is determined from said location of said one other mobile station and from a known, predetermined location of said basestation.

11. A method as in claim 8 further comprising:

receiving a location of said first mobile station, wherein said time at said basestation also is determined from said location of said first mobile cellular communication station and from a known, predetermined location of said basestation.

12. A method as in claim 11 wherein said location of said mobile station and said location and said known predetermined location of said basestation are used to determine a propagation delay between said mobile station and said basestation.

13. A method as in claim 11 wherein said other basestations synchronize to said basestation by receiving other time indicators and wherein said other time indicators and said time indicator are based upon a same time standard.

14. A method as in claim 13 wherein said same time standard is a Global Positioning System time.

15. A basestation apparatus for use in a cellular communication system to synchronize time between mobile stations and basestations in a communication system, said basestation comprising:

a transceiver;

a network interface coupled to said transceiver; and

a clock coupled to said transceiver, said transceiver receiving a time indicator from a first mobile station which represents a time-of-day at said first mobile station, wherein said time indicator is determined relative to a signal which is available to said basestation and wherein a time for said clock is determined from said time indicator such that said basestation is synchronized to other basestations and wherein said transceiver transmits the time for said clock to at least one other mobile station such that the time at the one other mobile station is synchronized to the time for said clock and a propagation delay.

16. A basestation as in claim 15 wherein said signal is a cellular communication signal transmitted from said basestation.

17. A basestation as in claim 16 wherein said network interface transfers land-based communications to said first mobile station and said one other mobile station through said transceiver and wherein said transceiver receives a location of said mobile station, wherein said time for said clock also is determined from said location and from a known, predetermined location of said basestation.

18. A basestation as in claim 17 further comprising:

a digital processing system coupled to said clock and coupled to at least one of said transceiver and said network interface, said digital processing system determining a propagation delay from said location and said known, predetermined location, and using said propagation delay and said time indicator to set said time on said clock or provide a correction to said clock.

19. A basestation as in claim 18 wherein said other basestations and said one other mobile station synchronize to said basestation by receiving other time indicators from at least one of said first mobile station and other mobile stations and wherein said other time indicators and said time indicator are based upon a same time standard.

20. A mobile station comprising:

a transceiver to receive communication signals from at least one basestation;

said transceiver receiving a time for a basestation clock, wherein said time for said basestation clock is determined from an indicator from another mobile station which represents a time-of-day at said another mobile station, wherein said time indicator is determined relative to a signal which is available to said basestation and wherein a time for said clock is determined from said time indicator such that said basestation is synchronized to other basestations; and

wherein said mobile station is synchronized to the time for said clock and a propagation delay.

21. The mobile station of claim 20 comprising a satellite positioning system (SPS) receiver coupled to said transceiver such that the SPS receiver is not able to determine the time-of-day from the SPS.

22. A mobile station as in claim 21 wherein said SPS receiver determines a location and said propagation delay is based on said determined location of the mobile station and the known location of said basestation.