Time acquisition in a wireless position determination system

• US 20020168988A1
• Filed: 03/15/2002
• Published: 11/14/2002
• Est. Priority Date: 03/15/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Younis, Saed
• Granted Patent: US 6,907,224 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset

Abstract

A system and method for providing timing information to a wireless device in a position determination system is disclosed. A wireless device includes a reference signal receiver, a signal processor, a wireless communications transceiver and a GPS receiver. The wireless device is adapted to receive a reference signal, extract a snippet of the received reference signal, determine a time of reception for the snippet and transmit the snippet and time of reception to a position determination entity as part of a request for GPS aiding information. The position determination entity includes a timing source, a GPS memory for storing GPS satellite information, a reference signal memory, a communications interface, a signal processor and a control processor. The position determination entity is adapted to continually receive and store a reference signal along with an associated time of reception, and receive the snippet and timestamp transmitted from the wireless device. The position determination entity is further adapted to match the signal snippet to a portion of the stored reference signal, determine a time offset between the timestamp and the time of reception of the matched portion of the stored reference signal, prepare aiding information for the wireless device, synchronize the aiding information to the wireless device using the time offset, and transmit the synchronized aiding information to the wireless device. The wireless device is further adapted to receive the aiding information, including timing information to assist the wireless device in acquiring the GPS signals.

Claims

1. In a wireless communications system including a position determination entity, a method for acquiring satellite positioning system signals comprising the following steps:

receiving a snippet of a reference signal, the snippet having a time of reception measured by a timing source;

transmitting a request for aiding information to the position determination entity, the request including the snippet and the time of reception;

receiving the requested aiding information; and

locating the satellite positioning system signals using the received aiding information.

2. The method of claim 1 wherein the timing source is not synchronized with the position determination entity.

3. The method of claim 1 wherein the step of receiving a snippet comprises the steps of:

receiving a radio frequency (RF) signal; and

sampling a portion of the received radio frequency signal.

4. The method of claim 3 wherein the RF signal is an FM radio broadcast signal.

5. The method of claim 3 wherein the RF signal is ubiquitous throughout the wireless communications system.

6. The method of claim 1 wherein the aiding information includes timing information that identifies the time at which the wireless device is expected to receive the satellite signals.

7. The method of claim 1 wherein the aiding information is synchronized with the timing source.

8. In a wireless communications system, a method for assisting a wireless device in acquiring satellite positioning system signals, comprising the following steps:

maintaining a timing source;

continually receiving a reference signal;

storing the reference signal, the stored reference signal having an associated time of reception that is measured by the timing source;

receiving a request from the wireless device for aiding information, the request including a signal snippet and a timestamp;

matching the signal snippet to a portion of the stored reference signal;

determining a time offset between the timestamp and the time of reception of the matched portion of the stored reference signal;

preparing aiding information for the wireless device;

synchronizing the aiding information to the wireless device using the time offset; and

transmitting the synchronized aiding information to the wireless device.

9. The method of claim 8 wherein the timing source is not synchronized with the wireless device.

10. The method of claim 8 wherein the reference signal is a ubiquitous signal.

11. The method of claim 10 wherein the ubiquitous signal comprises an FM radio broadcast signal.

12. The method of claim 8 wherein the step of storing comprises the following steps:

sampling the received reference signal; and

storing the sampled reference signal in a buffer;

wherein the time of reception of each stored sample may be determined as a function of the current time, as measured by the timing source, and its position in the buffer.

13. The method of claim 8 wherein the aiding information includes timing information identifying the time at which the satellite positioning system signals are expected to be received by the wireless device.

15. The wireless device of claim 14 wherein the reference signal receiver is an FM radio receiver.

16. The wireless device of claim 14 wherein the reference signal receiver is an AM radio receiver.

17. The wireless device of claim 14 wherein the reference signal receiver is a television signal receiver.

18. The wireless device of claim 14 further comprising:

a processor; and

a timing source;

wherein the time of reception of the snippet is determined using the timing source;

wherein the SPS aiding information includes a time offset, and

wherein the processor is adapted to synchronize the timing source with the position determination entity using the time offset.

19. The wireless device of claim 14 further comprising:

double heterodyne receiver circuitry adapted to double downconvert a radio frequency (RF) input signal to an intermediate frequency (IF) signal;

wherein the reference receiver provides a first RF input to the double heterodyne receiver circuitry;

wherein the communications transceiver provides a second RF input to the double heterodyne receiver circuitry; and

wherein the SPS receiver provides a third RF input to the double heterodyne receiver circuitry; and

a switch for selecting one of the first, second, and third RF input signals for input to the double heterodyne receiver.

14. In a satellite positioning system (SPS) including a position determination entity, a wireless device comprising:

a reference signal receiver adapted to receive an RF signal;

a signal processor coupled to the reference signal receiver, the signal processor adapted to extract a snippet of the RF signal and determine a time of reception at which the snippet of the RF signal was received by the reference signal receiver;

a wireless communications transceiver adapted to transmit the snippet and time of reception to a position determination entity, and receive SPS aiding information from the position determination entity; and

a SPS receiver adapted to receive SPS satellite signals using the SPS aiding information.

20. In a wireless communications network including a wireless device having a first clock and a position determination entity having a second clock a method for providing global positioning system (GPS) timing information to the wireless device, the method comprising the following steps:

receiving a reference signal;

extracting a snippet of the received reference signal;

determining a time of reception for the snippet according to the first clock;

transmitting the snippet and the time of reception to the position determination entity; and

receiving aiding information from the position determination entity, the aiding information including timing information relating to the acquisition of a satellite positioning system signal, the timing information being synchronized with the first clock.

21. The method of claim 20 wherein the step of extracting a snippet comprises the step of sampling a portion of the received reference signal.

22. The method of claim 21 wherein the reference signal is an FM radio broadcast signal.

23. The method of claim 22 wherein the FM radio broadcast signal is ubiquitous throughout the wireless communications network.

24. In a wireless communications system including a wireless device, a position determination entity comprising:

a timing source;

a satellite positioning system (SPS) memory including stored SPS satellite position information;

a reference signal memory including a stored reference signal and associated time of reception information;

a communications interface adapted to receive a request for aiding information from the wireless device, the request including a signal snippet and a timestamp;

a signal processor adapted to align the signal snippet with a portion of the stored reference signal; and

a control processor adapted to determine a time offset between the timestamp and the time of reception of the portion of the stored reference signal, prepare aiding information from the SPS satellite information to assist the wireless device in locating the SPS satellite signals, and adjust the aiding information using the time offset to synchronize the aiding information with the wireless device, and using the communications interface, transmit the aiding information to the wireless device.