Methods and apparatus for supporting timing and/or frequency corrections in a wireless communications system

• US 7,991,362 B2
• Filed: 08/31/2005
• Issued: 08/02/2011
• Est. Priority Date: 07/20/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Li, Junyi, Lane, Frank A.
• Primary Examiner(s): Addy; Anthony S
• Application Number:
  US11/216,770
• Publication Number:
  US 20070021121A1
• Time in Patent Office: 2,162 Days
• Field of Search: 455/11.1, 455/12.1, 455/13.1, 455/13.2, 455/404.1, 455/404.2, 455/430, 455/431, 4554561-457, 455/524, 455/525, 455/550.1, 455/561, 455/62, 455/71, 455/441
• US Class Current: 455/71
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236
• CPC Class Codes: G01S 5/0284 Relative positioning
• CPC Class Codes: H04B 7/01 Reducing phase shift
• CPC Class Codes: H04W 56/0025 synchronizing potentially movable access points
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase
• CPC Class Codes: H04W 56/006 using known positions of transmitter and receiver
• CPC Class Codes: H04W 92/10 between terminal device and access point, i.e. wireless air interface

Abstract

A wireless terminal determines the position of a moving base station and determines timing and/or frequency corrections. A wireless terminal determines its relative position with respect to the base station and determines a timing adjustment correction. The wireless terminal applies the determined timing correction to control uplink signaling timing and achieve synchronization at the base station'"'"'s receiver. The wireless terminal determines its relative velocity with respect to the moving base station and determines a Doppler shift adjustment which it adds to the uplink carrier frequency or to its baseband signal. Base station position is determined from the current time and stored information correlating the base station position with time, e.g., for a geo-synchronous satellite. Base station position information, e.g., a GPS derived base station position fix, is determined from downlink airlink broadcast information, e.g., for an aircraft base station. Wireless terminals may be mobile and include a GPS receiver for wireless terminal position determination.

Claims

1. A method of operating a wireless communications terminal to communicate with a moving base station, the method comprising:

receiving a signal from a base station indicating a position of the moving base station;

computing a relative velocity between the moving base station and a wireless terminal based on the position of the moving base station indicated by the received signal;

determining a Doppler shift correction based on the computed relative velocity between the moving base station and the wireless terminal; and

generating uplink signals for transmission from the wireless terminal, the uplink signals comprising the Doppler shift correction based on the computed relative velocity between the moving base station and the wireless terminal combined with a baseband signal or a carrier frequency,

wherein the signal is received periodically at an interval and a change in the position of the wireless terminal relative to the moving base station is less than or equal to 11 km, based at least in part on the interval and relative velocity.

2. The method of claim 1, wherein the moving base station is mounted on an airplane and wherein the position of the moving base station is a global positioning system determined position.

3. The method of claim 1, wherein the moving base station is a non-geostationary satellite.

4. The method of claim 1, further comprising:

registering with the moving base station; and

wherein the signal indicating the position of the moving base station is received when registering with the moving base station.

5. The method of claim 4, further comprising:

receiving moving base station position information on a periodic basis from signals transmitted by the moving base station.

6. The method of claim 4, wherein the moving base station position information is received at intervals less than or equal to 11 msec.

7. The method of claim 1, wherein computing the relative velocity includes determining a position of the wireless terminal at different points in time.

8. The method of claim 7, wherein determining the position of the wireless terminal includes using global positioning system(GPS) information obtained from a GPS receiver included in the wireless terminal.

9. The method of claim 1, wherein determining the Doppler shift correction based on the position of the moving base station includes determining the relative position of the wireless terminal with respect to the moving base station.

10. The method of claim 9, wherein determining the relative position includes using global positioning system (GPS) position information obtained from a GPS receiver included in the wireless terminal.

11. The method of claim 9, wherein the wireless terminal is a fixed wireless terminal, the wireless terminal is pre-programmed with wireless terminal position information, and the pre-programmed wireless terminal position is used to determine the relative position of the wireless terminal with respect to the moving base station.

12. The method of claim 1, wherein the wireless terminal and the moving base station communicate with one another via orthogonal frequency-division multiplexing (OFDM) signaling.

13. A wireless terminal capable of communicating with a moving base station, the wireless terminal comprising:

a base station position determination unit for determining the position of a base station from a received signal indicating the position of the base station, the received signal being from the moving base station;

a relative velocity determination unit for computing a relative velocity between the moving base station and the wireless terminal based on base station position information received from the base station position determination module;

a Doppler shift adjustment unit for generating a Doppler shift correction based on the computed relative velocity between the moving base station and the wireless terminal; and

a combining unit for generating uplink signals for transmission from the wireless terminal, the uplink signals comprising the Doppler shift correction based on the computed relative velocity between the moving base station and the wireless terminal combined with a baseband signal or a carrier frequency,

wherein the signal is received periodically at an interval and a change in the position of the wireless terminal relative to the moving base station is less than or equal to 11 km, based at least in part on the interval and relative velocity.

14. The wireless terminal of claim 13, wherein the moving base station is mounted on an airplane and wherein the position of the moving base station is a global positioning system determined position.

15. The wireless terminal of claim 13, wherein the moving base station is a non-geostationary satellite.

16. The wireless terminal of claim 13, wherein the wireless terminal includes a receiver for receiving the signal indicating the position of the moving base station from the base station.

17. The wireless terminal of claim 16, wherein the receiver is configured to receive base station position information on a periodic basis from signals transmitted by the moving base station.

18. The wireless terminal of claim 17, wherein the moving base station position information is received at intervals less than or equal to 11 msec.

19. The wireless terminal of claim 13, wherein the combining unit is a carrier frequency adder for generating uplink signals for transmission from the wireless terminal, the carrier frequency adder adding the Doppler shift correction based on the computed relative velocity between the moving base station and the wireless terminal determined by the Doppler shift adjustment unit to the carrier frequency.

20. The wireless terminal of claim 13, wherein the combining unit is a baseband signal adder for generating uplink signals for transmission from the wireless terminal, the combining unit adding the Doppler shift correction based on the computed relative velocity between the moving base station and the wireless terminal to the baseband signal to be transmitted.

21. The wireless terminal of claim 13, further comprising:

a wireless terminal position determination unit for determining the wireless terminal position at different points in time; and

a velocity determination unit for computing a relative velocity from the determined wireless terminal position at different points in time.

22. The wireless terminal of claim 21, wherein the wireless terminal position determination unit uses orthogonal frequency-division multiplexing (OFDM) beacon signals to determine the position of the wireless terminal.

23. The wireless terminal of claim 21, wherein the wireless terminal position determination unit uses global positioning system (GPS) information obtained from a GPS receiver included in the wireless terminal.

24. The wireless terminal of claim 13, wherein the wireless terminal is a fixed wireless terminal that includes a memory with stored pre-programmed wireless terminal position information, and the pre-programmed wireless terminal position is used to determine the relative position of the wireless terminal with respect to the moving base station.

25. The wireless terminal of claim 13, wherein the wireless terminal further comprises:

an orthogonal frequency-division multiplexing (OFDM) receiver;

an OFDM transmitter, and

wherein the receiver and transmitter enable communications with the moving base station communicate with the moving base station via OFDM signaling.

26. A wireless terminal capable of communicating with a moving base station, the wireless terminal comprising:

base station position determination means for recovering an indicated position of a base station from a received signal that indicates the position of the base station, the received signal being from the moving base station;

relative velocity determination means for computing a relative velocity between the moving base station and the wireless terminal based on base station position information received from the base station position determination means;

Doppler shift adjustment means for generating a Doppler shift correction based on the computed relative velocity between the moving base station and the wireless terminal; and

combining means for generating uplink signals for transmission from the wireless terminal, the uplink signals comprising the Doppler shift correction based on the computed relative velocity between the moving base station and the wireless terminal combined with a baseband signal or a carrier frequency,

wherein the signal is received periodically at an interval and a change in the position of the wireless terminal relative to the moving base station is less than or equal to 11 km, based at least in part on the interval and relative velocity.

27. The wireless terminal of claim 26, wherein the moving base station is mounted on an airplane and wherein the position of the moving base station is a global positioning system determined position.

28. The wireless terminal of claim 26, wherein the moving base station is a non-geostationary satellite.

29. A non-transitory machine readable medium including machine executable instructions for use in a wireless terminal communicating with a moving base station, the non-transitory machine readable medium comprising:

instructions for causing the wireless terminal to recover an indicated base station position from a signal, received from the moving base station, that indicates the position of the base station;

instructions for causing the wireless terminal to compute a relative velocity between the moving base station and the wireless terminal based on the moving base station position indicated by the received signal;

instructions for causing the wireless terminal to determine a Doppler shift correction based on the computed relative velocity between the moving base station and the wireless terminal; and

instructions for causing the wireless terminal to generate uplink signals for transmission from the wireless terminal, the uplink signals comprising the Doppler shift correction based on the computed relative velocity between the moving base station and the wireless terminal combined with a baseband signal or a carrier frequency,

wherein the signal is received periodically at an interval and a change in the position of the wireless terminal relative to the moving base station is less than or equal to 11 km, based at least in part on the interval and relative velocity.