GPS signal acquisition based on frequency-domain and time-domain processing

• US 6,922,546 B1
• Filed: 05/03/2000
• Issued: 07/26/2005
• Est. Priority Date: 05/03/2000
• Status: Expired due to Term

• Current Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Da, Ren, Vannucci, Giovanni
• Primary Examiner(s): Gesesse, Tilahun
• Application Number:
  US09/564,096
• Time in Patent Office: 1,910 Days
• Field of Search: 455/12.1, 455/13.3, 455/431, 455/427, 455/428, 455/429, 455/430, 455/13.1, 455/456.1, 455/456.2, 455/456.3, 455/457, 455/440, 342/357.06, 342/357.01, 342/457, 342/450, 340/988
• US Class Current: 455/12.1
• CPC Class Codes: G01S 19/06 employing an initial estimate of the location of the receiver as aiding data or in generating aiding data
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/254 relating to Doppler shift of satellite signals
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset

Abstract

An improved code acquisition scheme for faster acquisition of GPS “coarse acquisition” (C/A) codes leads to faster detection of GPS signals, and thereby a wireless terminal may determine its position in a shorter period of time. The scheme is a combination of a frequency-domain and time-domain code acquisition techniques. The scheme utilizes a frequency-domain code acquisition technique to detect one GPS signal and to create a precise timing reference at the wireless terminal, and then utilizes time-domain code acquisition techniques to detect other GPS signals from the same satellite or other satellites faster. The scheme has the advantage of being able to be used for any wireless communications system without the requirement of maintaining a precise timing reference in the wireless terminals, and without the requirement of heavy computational resources that are usually needed in systems that utilize frequency-domain code acquisition techniques.

Claims

1. At a single terminal, a method for detecting two or more signals from one or more satellites, comprising the steps of:

(a) receiving timing reference assistance information corresponding to a detected first signal from a first satellite;

(b) detecting a second signal from a satellite using a frequency-domain code acquisition technique;

(c) determining an actual code phase based on the detected second signal;

(d1) comparing a predicted code phase indicated by the timing reference assistance information and the actual code phase;

(d2) generating a precise timing reference based on the comparison; and

(e) detecting one or more other signals based on the precise timing reference using one or more time-domain code acquisition techniques.

2. The invention of claim 1, wherein the second signal is from the first satellite.

3. The invention of claim 1, wherein the second signal is from a second satellite different from the first satellite.

4. The invention of claim 1, wherein a predicted Doppler frequency indicated in the timing reference assistance information based on the detected first signal is used to accelerate the frequency-domain code acquisition technique used to detect the second signal.

5. The invention of claim 4, wherein the timing reference assistance information comprises the predicted Doppler frequency.

6. The invention of claim 4, wherein the predicted Doppler frequency is generated from the timing reference assistance information.

7. The invention of claim 1, wherein the one or more other signals comprise one or more signals from one or more satellites other than the first satellite.

8. The invention of claim 1, wherein the one or more other signals comprise a subsequent signal from the first satellite.

9. The invention of claim 1, further comprising the step of determining position based on the detected second signal and two or more other detected signals from two or more other satellites.

10. The invention of claim 1, wherein:

the first signal is a first GPS signal from a first GPS satellite; and

the second signal is a second GPS signal from the first GPS satellite.

11. The invention of claim 1, wherein the timing reference assistance information comprise the predicted code phase.

12. The invention of claim 1, wherein the predicted code phase is generated based on the timing reference assistance information.

13. The invention of claim 1, wherein the frequency-domain code acquisition technique involves applying a fast Fourier transform to the second signal.

14. The invention of claim 1, wherein the one or more other signals are detected without using any frequency-domain code acquisition technique.

15. A terminal for detecting two or more signals from one or more satellites, the terminal comprising:

(a) a satellite receiver configured to receive the two or more signals from one or more satellites;

(b) a telecommunication receiver configured to receive timing reference assistance information corresponding to a detected first signal from a first satellite;

(c) a processor configured to process the two or more signals from the satellite receiver and the timing reference assistance information from the telecommunication receiver; and

(d) a timing calibrator configured to generate a precise timing reference for the terminal, wherein;

the satellite receiver detects a second signal from a satellite using a frequency-domain code acquisition technique;

the processor determines an actual code phase based on the detected second signal;

the timing calibrator (1) compares a predicted code phase indicated by the timing reference assistance information and the actual code phase and (2) generates the precise timing reference based on the comparison; and

the processor detects one or more other signals based on the precise timing reference using one or more time-domain code acquisition techniques.

16. The invention of claim 15, wherein the second signal is from the first satellite.

17. The invention of claim 15, wherein the second signal is from a second satellite different from the first satellite.

18. The invention of claim 15, wherein the terminal uses a predicted Doppler frequency indicated in the timing reference assistance information based on the detected first signal to accelerate the frequency-domain code acquisition technique used to detect the second signal.

19. The invention of claim 18, wherein the timing reference assistance information comprises the predicted Doppler frequency.

20. The invention of claim 18, wherein the processor generates the predicted Doppler frequency from the timing reference assistance information.

21. The invention of claim 15, wherein the one or more other signals comprise one or more signals from one or more satellites other than the first satellite.

22. The invention of claim 15, wherein the one or more other signals comprise a subsequent signal from the first satellite.

23. The invention of claim 15, wherein the processor determines the position of the terminal based on the detected second signal and two or more other detected signals from two or more other satellites.

24. The invention of claim 15, wherein:

the terminal is a wireless terminal of a wireless telecommunication network;

the first signal is a first GPS signal from a first GPS satellite; and

the second signal is a second GPS signal from the first GPS satellite.

25. The invention of claim 15, wherein the timing references assistance information comprises the predicted code phase.

26. The invention of claim 15, wherein the processor generates the predicted code phase based on the timing reference assistance information.

27. The invention of claim 15, wherein the frequency-domain code acquisition technique involves applying a fast Fourier transform to the second signal.

28. The invention of claim 15, wherein the one ore more other signals are detected without any frequency-domain code acquisition technique.