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

• US 20070021121A1
• Filed: 08/31/2005
• Published: 01/25/2007
• Est. Priority Date: 07/20/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Li, Junyi, Lane, Frank
• Granted Patent: US 7,991,362 B2
• Time in Patent Office: Days
• US Class Current: 455/441
• 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:

determining the position of the moving base station; and

determining one of a timing and frequency correction based on the determined base station position.

2. The method of claim 1, wherein said step of determining the position of the moving base station includes determining the current time and using information correlating base station position with time.

3. The method of claim 2, wherein the base station is a non-geostationary satellite.

4. The method of claim 1, wherein said step of determining the position of the moving base station includes determining the position from information broadcast by the base station.

5. The method of claim 4, wherein the broadcast information is position information.

6. The method of claim 4, wherein the broadcast information is time information.

7. The method of claim 1, wherein determining one of a timing and frequency correction based on the determined base station position includes determining a frequency correction and includes computing a relative velocity between said base station and said wireless terminal.

8. The method of claim 7, wherein the frequency correction is a Doppler adjustment correction added to uplink carrier frequency.

9. The method of claim 7, wherein the frequency correction is a Doppler adjustment correction added to the baseband signal.

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

11. The method of claim 10, wherein determining the wireless terminal position includes using GPS information obtained from a GPS receiver included in said wireless terminal.

12. The method of claim 1, wherein determining one of a timing and frequency correction based on the determined base station position includes determining a timing correction and includes determining the relative position of the wireless terminal with respect to the base station.

13. The method of claim 12, wherein determining the relative position includes using GPS position information obtained from a GPS receiver included in the wireless terminal.

14. The method of claim 12, wherein the wireless terminal is a fixed wireless terminal, wireless terminal is pre-programmed with wireless terminal position information, and said pre-programmed wireless terminal position is used to determine said relative position of the wireless terminal with respect to the base station.

15. The method of claim 1, wherein said wireless terminal and said moving base station communicate with one another via OFDM signaling.

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

a base station position determination module for determining the position of the moving base station; and

a first correction determination module for generating at least one of a timing and a frequency correction based on the determined position of the moving base station.

17. The method of claim 16, further comprising:

a memory storing base storing position information indicating base station position relative to time;

a current time source for indicating a current time; and

wherein said base station position determination module determines the position of the moving base station from the current time indicated by said current time source and said stored information correlating base station position with time.

18. The wireless terminal of claim 17, wherein the base station is a non-geostationary satellite and wherein said stored base station position information indicates the position of said non-geostationary satellite as a function of time.

19. The wireless terminal of claim 16,

wherein said wireless terminal includes a receiver for receiving base station position information broadcast by said base station;

and

wherein the base station position determination module determines the position of the moving base station from information broadcast by the base station and received by said receiver.

20. The wireless terminal of claim 19, wherein the broadcast information is position information.

21. The wireless terminal of claim 19, wherein the broadcast information includes time information.

22. The wireless terminal of claim 16, wherein said first correction determination module is one of a relative distance determination module for generating a timing offset adjustment signal and a Doppler shift adjustment determination module for determining a frequency correction signal.

23. The wireless terminal of claim 22, wherein said first correction determination module is a relative distance determination module and wherein said wireless terminal further includes a second correction determination module which is a Doppler shift adjustment determination module.

24. The wireless terminal of claim 22,

wherein said first correction determination module is a Doppler shift adjustment determination module;

and

wherein said wireless terminal further includes a relative velocity determination module for determining-a relative velocity between said base station and said wireless terminal from base station position information received from said base station position determination module, said relative velocity being used by said Doppler shift adjustment module to determine the Doppler shift adjustment.

25. The wireless terminal of claim 24, further comprising a carrier frequency adder for adding the frequency correction determined by said Doppler shift adjustment module to a carrier frequency being used for uplink signal transmissions.

26. The wireless terminal of claim 22, further comprising a basesband signal adder for adding the frequency correction to a baseband signal to be transmitted.

27. The wireless terminal of claim 22, further comprising:

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

wherein said velocity determination module computes the relative velocity from the determined wireless terminal position at different points in time.

28. The wireless terminal of claim 27, wherein said wireless terminal position determination module uses OFDM beacon signals to determine the position of the wireless terminal.

29. The wireless terminal of claim 27, wherein said wireless terminal position determination module uses GPS information obtained from a GPS receiver included in said wireless terminal.

30. The wireless terminal of claim 16, wherein the wireless terminal is a fixed wireless terminal, wireless terminal includes a memory with stored pre-programmed wireless terminal position information, and said pre-programmed wireless terminal position is used to determine said relative position of the wireless terminal with respect to the base station.

31. The wireless terminal of claim 16, wherein said wireless terminal further comprises:

an OFDM receiver;

an OFDM transmitter, and

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