Enhancement of signal-detection capability of GPS systems

• US 6,252,545 B1
• Filed: 02/04/2000
• Issued: 06/26/2001
• Est. Priority Date: 02/04/2000
• Status: Expired due to Term

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Da, Ren, Vannucci, Giovanni
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/497,418
• Time in Patent Office: 508 Days
• Field of Search: 342/357.06, 342/357.1, 342/357.12, 455/12.1, 701/213
• US Class Current: 342/357.42
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/246 involving long acquisition integration times, extended snapshots of signals or methods specifically directed towards weak signal acquisition
• 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

Abstract

Estimated Global Position System (GPS) navigation data is used to increase the signal integration interval. In one embodiment, a WAG (wireless assisted GPS) server receives GPS signals and demodulates the navigation data modulated onto the GPS signals. The WAG server utilizes known features of the demodulated navigation data to generate estimated navigation data for the satellite. This estimation can be made several seconds or even minutes ahead of time. The wireless terminal uses this estimated navigation data to perform a data wipe-off operation to enable the integration interval to be increased (e.g., beyond 20 ms), thereby increasing overall signal-detection sensitivity at the wireless terminal. In another embodiment, information from strong GPS signals is used to detect weak GPS signals from other satellites. In this embodiment, strong GPS signals are received directly by the wireless terminal from the satellites. After strong GPS signals have been detected, the strong GPS signals are demodulated to compute satellite ephemerides including navigation data. The demodulated navigation data is then matched with known features of the navigation data to estimate the navigation data for weak GPS signals. The estimated navigation data is then used to increase the integration interval for weak GPS signals so that weak GPS signals can also be detected at the wireless terminal.

Claims

1. A method for processing GPS signals modulated with navigation data, comprising the steps of:

(a) recovering navigation data from a first GPS signal transmitted by a first satellite of a GPS system;

(b) generating estimated navigation data based on the recovered navigation data; and

(c) performing, at a wireless terminal, a data wipe-off operation on a subsequent GPS signal, received by the wireless terminal, wherein the data wipe-off operation is based on the estimated navigation data.

2. The invention of claim 1, wherein the subsequent GPS signal is transmitted by the first satellite and step (a) is performed at a server of the GPS system.

3. The invention of claim 2, wherein the server transmits the recovered navigation data to the wireless terminal and step (b) is performed at the wireless terminal.

4. The invention of claim 2, wherein step (b) is performed at the server and the server transmits the estimated navigation data to the wireless terminal.

5. The invention of claim 1, wherein the subsequent GPS signal is transmitted by a second satellite of the GPS system.

6. The invention of claim 5, wherein step (a) is performed at a server of the GPS system.

7. The invention of claim 6, wherein the server transmits the recovered navigation data to the wireless terminal and step (b) is performed at the wireless terminal.

8. The invention of claim 6, wherein step (b) is performed at the server and the server transmits the estimated navigation data to the wireless terminal.

9. The invention of claim 5, wherein steps (a), (b), and (c) are performed at the wireless terminal.

10. The invention of claim 1, wherein the wireless terminal enlarges its integration interval to detect the subsequent GPS signal after the data wipe-off operation.

11. The invention of claim 10, wherein the enlarged integration interval is greater than 20 ms.

12. The invention of claim 10, wherein the wireless terminal detects the subsequent GPS signal without having to buffer the subsequent GPS signal.

13. The invention of claim 10, wherein the subsequent GPS signal is transmitted by the first satellite, and the step (a) is performed at a server of the GPS system, and the server transmits the recovered navigation data to the wireless terminal and step (b) is performed at the wireless terminal.

14. The invention of claim 10, wherein the subsequent GPS signal is transmitted by the first satellite and steps (a) and (b) are performed at a server of the GPS system, and the server transmits the estimated navigation data to the wireless terminal.

15. The invention of claim 10, wherein the subsequent GPS signal is transmitted by a second satellite of the GPS system, and step (a) is performed at a server of the GPS system, and the server transmits the recovered navigation data to the wireless terminal and step (b) is performed at the wireless terminal.

16. The invention of claim 10, wherein the subsequent GPS signal is transmitted by a second satellite of the GPS system, and steps (a) and (b) are performed at a server of the GPS system, and the server transmits the estimated navigation data to the wireless terminal.

17. The invention of claim 10, wherein the subsequent GPS signal is transmitted by a second satellite of the GPS system, and steps (a), (b), and (c) are performed at the wireless terminal.

18. A server for a GPS system, comprising:

(a) a GPS receiver configured to receive a first GPS signal modulated with navigation data and transmitted from a first satellite of the GPS system;

(b) a demodulator configured to recover the navigation data from the received first GPS signal; and

(c) an estimator configured to generate estimated navigation data from the recovered navigation data, wherein the server is configured to transmit the estimated navigation data for receipt by a wireless terminal configured to perform a data wipe-off operation based on the estimated navigation data.

19. The invention of claim 18, wherein the estimated navigation data corresponds to the first satellite.

20. The invention of claim 18, wherein the estimated navigation data corresponds to a second satellite of the GPS system.

21. A wireless terminal for a GPS system, comprising:

(a) a GPS receiver configured to receive GPS signals modulated with navigation data; and

(b) a data wipe-off processor configured to perform a data wipe-off operation on a GPS signal transmitted by a satellite in the GPS system based on estimated navigation data.

22. The invention of claim 21, wherein the wireless terminal receives the estimated navigation data from a server in the GPS system.

23. The invention of claim 22, wherein the estimated navigation data corresponds to a previous GPS signal from the satellite.

24. The invention of claim 22, wherein the estimated navigation data corresponds to a previous GPS signal from another satellite of the GPS system.

25. The invention of claim 21, wherein the wireless terminal further comprises an estimator configured to generate the estimated navigation data from recovered navigation data.

26. The invention of claim 25, wherein the wireless terminal receives the recovered navigation data from a server in the GPS system.

27. The invention of claim 26, wherein the recovered navigation data corresponds to a previous GPS signal from the satellite.

28. The invention of claim 26, wherein the recovered navigation data corresponds to a previous GPS signal from another satellite of the GPS system.

29. The invention of claim 25, wherein the wireless terminal further comprises a demodulator configured to generate the recovered navigation data corresponding to a GPS signal received from another satellite of the GPS system.

30. The invention of claim 21, wherein the wireless terminal enlarges its integration interval to detect the GPS signal after the data wipe-off operation.

31. The invention of claim 30, wherein the enlarged integration interval is greater than 20 ms.

32. The invention of claim 30, wherein the wireless terminal detects the GPS signal without having to buffer the GPS signal.