Method and system for determining time in a satellite positioning system

• US 7,554,487 B2
• Filed: 03/26/2007
• Issued: 06/30/2009
• Est. Priority Date: 11/17/2000
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Podshivalov, Sergi, Abraham, Charles, van Diggelen, Frank
• Primary Examiner(s): Issing; Gregory C
• Application Number:
  US11/728,391
• Publication Number:
  US 20070171125A1
• Time in Patent Office: 827 Days
• Field of Search: None
• US Class Current: 342/357.25
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/09 providing processing capability normally carried out by the receiver
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/27 creating, predicting or correcting ephemeris or almanac data within the receiver
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: G01S 2205/008 using a mobile telephone network
• CPC Class Codes: G01S 5/0018 Transmission from mobile station to base station
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station

Abstract

Method and apparatus for receiving an estimate of time in a satellite signal receiver receives an estimate of time from a server and compensates for error of a clock in the satellite signal receiver using the estimate of time. The output of the compensated clock is used when computing a position of the satellite signal receiver. The estimate of time is received using a network time protocol (NTP), a simple network time protocol (SNTP), or by one-way broadcast from the server.

Claims

1. A method of receiving an estimate of time in a satellite signal receiver comprising:

receiving a broadcast of an estimate of time from a server at the satellite signal receiver;

compensating for error of a clock in the satellite signal receiver using the estimate of time;

designating the output of the compensated clock as an a-priori estimate of absolute time; and

employing the a-priori estimate of absolute time in a mathematical model that updates the a-priori estimate of absolute time to compute a position of the satellite signal receiver and an absolute time.

2. The method of claim 1, further comprising:

employing the absolute time when computing a position of the satellite signal receiver.

3. A method of receiving an estimate of time in a satellite signal receiver comprising:

receiving a broadcast of an estimate of time from a server at the satellite signal receiver;

compensating for error of a clock in the satellite signal receiver using the estimate of time;

designating the output of the compensated clock as an a-priori estimate of absolute time;

employing the a-priori estimate of absolute time in a mathematical model that updates the a-priori estimate of absolute time to compute a position of the satellite signal receiver and an absolute time;

providing an a-priori estimate of absolute time from a time source;

computing a position of the satellite signal receiver and an absolute time using a mathematical model that updates the a-priori estimate of absolute time; and

comparing the computed absolute time with the output of the compensated clock.

4. The method of claim 3, further comprising:

operating the clock in a low-power state while the satellite signal receiver is inactive.

5. A method of receiving an estimate of time in a satellite signal receiver comprising:

determining a time of last compensation of the clock;

comparing the time of last compensation with a threshold;

requesting the estimate of time from the server in response to the time of last compensation exceeding the threshold;

receiving a broadcast of an estimate of time from a server at the satellite signal receiver;

compensating for error of a clock in the satellite signal receiver using the estimate of time;

designating the output of the compensated clock as an a-priori estimate of absolute time; and

employing the a priori estimate of absolute time in a mathematical model that updates the a-priori estimate of absolute time to compute a position of the satellite signal receiver and an absolute time.

6. The method of claim 5, wherein receiving an estimate of time from a server and compensating for error of a clock in the satellite signal receiver are performed periodically.

7. The method of claim 5, wherein requesting and receiving an estimate of time is performed in response to the unavailability of absolute time.

8. A method for determining a position of a satellite signal receiver comprising:

computing pseudoranges that estimate the range of the satellite signal receiver to a plurality of satellites in a satellite constellation;

requesting and receiving a broadcast of an estimate of time from a server;

receiving ephemeris data relating to the satellite constellation;

designating the estimate of time as an a-priori estimate of absolute time; and

employing the designated a-priori estimate of absolute time in a mathematical model that updates the a-priori estimate of absolute time to determine the position of the satellite signal receiver and an absolute time.

9. The method of claim 8, wherein determining position comprises:

designating the estimate of time as an absolute time; and

employing the designated absolute time when determining the position of the satellite signal receiver.

10. A method for determining a position of a satellite signal receiver comprising:

computing pseudoranges that estimate the range of the satellite signal receiver to a plurality of satellites in a satellite constellation;

requesting and receiving a broadcast of an estimate of time from a server using a time transfer protocol;

receiving ephemeris data relating to the satellite constellation;

providing an a-priori estimate of absolute time from a time source;

computing a position of the satellite signal receiver and an absolute time using a mathematical model that updates the a-priori estimate of absolute time; and

comparing the computed absolute time with the estimate of time.

11. The method of claim 10, wherein the estimate of time from the server is in error by more than ten milliseconds.

12. A system for determining a position of a mobile device comprising:

a mobile device having a satellite signal receiver and a wireless transceiver; and

a server being in wireless communication with the mobile device, for broadcasting an estimate of time;

wherein said satellite signal receiver compensates for error of a clock in the satellite signal receiver using the estimate of time, designates the output of the compensated clock as an a-priori estimate of absolute time, and employs the a-priori estimate of absolute time in a mathematical model that updates the a-priori estimate of absolute time to compute a position of the satellite signal receiver and an absolute time.

13. The system of claim 12, wherein the wireless transceiver transmits pseudoranges and the output of the local clock to the server;

and

wherein the server receives ephemeris data and computes a position of the mobile device using the pseudoranges, the ephemeris data, and the output of the local clock.