FREQUENCY CORRECTION IN A MULTI-CARRIER COMMUNICATION SYSTEM

• US 20090279476A1
• Filed: 12/11/2006
• Published: 11/12/2009
• Est. Priority Date: 12/09/2005
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Neocific Incorporated
• Inventors: Lo, Titus, Li, Xiaodong
• Granted Patent: US 7,957,341 B2
• Time in Patent Office: Days
• US Class Current: 370/328
• CPC Class Codes: H04B 17/24 with feedback of measurements to the transmitter
• CPC Class Codes: H04B 7/015 Reducing echo effects
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase

Abstract

Methods and systems for correction of frequency errors in multi-carrier communication systems. The composite frequency error associated with the downlink signals are used to infer or derive the composite frequency error associated with the uplink signals, which are used to pre-compensate the uplink signals. Special signal components are transmitted by multiple base stations to facilitate frequency-error estimation and other system control functionalities at a mobile device. The mobile device carries out temporal, spatial, or spatial-temporal processing of the composite frequency errors associated with one or more base stations to determine the clock frequency error and the Doppler shift with respect to its serving base station.

Claims

1. A mobile device for operation within a multi-carrier wireless communication system having a plurality of base stations covering a geographic area divided into a plurality of cells, the mobile device comprising:

a receiver for receiving an error detection signal that is transmitted from at least one of the plurality of base stations, the error detection signal enabling the estimation of a frequency error existing on a downlink between the mobile device and at least one of the plurality of base stations;

a processor coupled to the receiver, the processor receiving the error detection signal transmitted by the at least one of the plurality of base stations and processing the error detection signal to produce an estimate of a frequency error that exists between the mobile device and at least one of the plurality of base stations; and

a signal conditioning component coupled to the processor and receiving the estimate of the frequency error from the processor, the signal conditioning component conditioning communication signals prior to transmission on an uplink from the mobile device to at least one of the plurality of base stations, the conditioning based on the estimate of the frequency error and correcting at least in part the effect of the frequency error.

2. The mobile device of claim 1, wherein the frequency error is a Doppler shift.

3. The mobile device of claim 1, wherein the frequency error is a clock frequency error.

4. The mobile device of claim 1, wherein the frequency error is a composite error comprising a Doppler shift and a clock frequency error.

5. The mobile device of claim 1, wherein the processor produces an estimate of the frequency error using spatial-temporal processing.

6. The mobile device of claim 5, wherein the processor comprises a multi-dimensional low-pass filter and the estimate of a frequency error produced by the processor is an estimate of a clock frequency error.

7. The mobile device of claim 6, wherein the processor comprises a linear finite impulse response (FIR) filter.

8. The mobile device of claim 1, wherein the processor produces an estimate of the frequency error using spatial processing.

9. The mobile device of claim 1, wherein the processor produces an estimate of the frequency error using temporal processing.

10. The mobile device of claim 1, wherein the signal conditioning component further conditioning second communication signals that are received from a base station, the conditioning based on the estimate of the frequency error and correcting at least in part the effect of the frequency error.

11. The mobile device of claim 1, wherein the error detection signal comprises a signal component selected from the group comprising:

a preamble, a midamble, a postamble, a code sequence, pilots, a control channel, or a control subchannel.

12. The mobile device of claim 11, wherein the error detection signal is in the frequency domain.

13. The mobile device of claim 11, wherein the error detection signal is in the time domain.

14. The mobile device of claim 1, wherein an error detection signal transmitted by one of the plurality of base stations is orthogonal to an error detection signal transmitted by another of the plurality of base stations.

15. The mobile device of claim 1, wherein an error detection signal transmitted by one of the plurality of base stations is nearly orthogonal to an error detection signal transmitted by another of the plurality of base stations.

16. The mobile device of claim 1, wherein the plurality of base stations transmit the error detection signal simultaneously.

17. The mobile device of claim 1, wherein the signal conditioning component conditions communication signals in a digital domain.

18. The mobile device of claim 1, wherein the signal conditioning component conditions communication signals in an analog domain and a digital domain.

19. The mobile device of claim 1, wherein the signal conditioning component conditions communication signals in an analog domain.

20. A method of correcting a frequency error in a mobile device that operates within a multi-carrier wireless communication system having a plurality of base stations covering a geographic area divided into a plurality of cells, the method comprising:

receiving an error detection signal that is transmitted from at least one of the plurality of base stations, the error detection signal enabling the estimation of a frequency error existing on a downlink between the mobile device and at least one of the plurality of base stations;

processing the received error detection signal to produce an estimate of a frequency error that exists between the mobile device and at least one of the plurality of base stations; and

conditioning communication signals prior to transmission on an uplink from the mobile device to at least one of the plurality of base stations, the conditioning based on the estimate of the frequency error and correcting at least in part the effect of the frequency error.

21. The method of claim 20, wherein the frequency error is a Doppler shift.

22. The method of claim 20, wherein the frequency error is a clock frequency error.

23. The method of claim 20, wherein the frequency error is a composite error comprising a Doppler shift and a clock frequency error.

24. The method of claim 20, wherein the estimate of the frequency error is produced using spatial-temporal processing.

25. The method of claim 20, wherein the estimate of the frequency error is produced using spatial processing.

26. The method of claim 20, wherein the estimate of the frequency error is produced using temporal processing.

27. The method of claim 20, further comprising conditioning second communication signals that are received from a base station, the conditioning based on the estimate of the frequency error and correcting at least in part the effect of the frequency error.

28. The method of claim 20, wherein the error detection signal comprises a signal component selected from the group comprising:

a preamble, a midamble, a postamble, a code sequence, pilots, a control channel, or a control subchannel.

29. The method of claim 28, wherein the error detection signal is in the frequency domain.

30. The method of claim 28, wherein the error detection signal is in the time domain.

31. The method of claim 20, wherein an error detection signal transmitted by one of the plurality of base stations is orthogonal to an error detection signal transmitted by another of the plurality of base stations.

32. The method of claim 20, wherein an error detection signal transmitted by one of the plurality of base stations is nearly orthogonal to an error detection signal transmitted by another of the plurality of base stations.

33. The method of claim 20, wherein the plurality of base stations transmit the error detection signal simultaneously.

34. The method of claim 20, wherein the conditioning of communication signals is performed in a digital domain.

35. The method of claim 20, wherein the conditioning of communication signals is performed in an analog domain and a digital domain.

36. The method of claim 20, wherein the conditioning of communication signals is performed in an analog domain.

37. A base station for operation within a multi-carrier wireless communication system that serves a plurality of mobile devices within a geographic area divided into a plurality of cells, the base station comprising:

a transmitter for transmitting an error detection signal to at least one of a plurality of mobile devices operating in an area served by the base station, the error detection signal enabling a mobile device receiving the error detection signal to estimate a frequency error existing on a downlink between the mobile device and the base station; and

a receiver for receiving a communication signal from a mobile device that received the error detection signal, the received communication signal having been conditioned by the mobile device prior to transmission on an uplink from the mobile device to the base station, the conditioning based on the estimate of the frequency error and correcting at least in part the effect of the frequency error.

38. The base station of claim 37, wherein the frequency error is a Doppler shift.

39. The base station of claim 37, wherein the frequency error is a clock frequency error.

40. The base station of claim 37, wherein the frequency error is a composite error comprising a Doppler shift and a clock frequency error.

41. The base station of claim 37, wherein the error detection signal comprises a signal component selected from the group comprising:

a preamble, a midamble, a postamble, a code sequence, pilots, a control channel, or a control subchannel.

42. The base station of claim 37, wherein the error detection signal is in the frequency domain.

43. The base station of claim 37, wherein the error detection signal is in the time domain.

44. The base station of claim 37, wherein the error detection signal transmitted by the base station is orthogonal to an error detection signal transmitted by another base station that operates within the multi-carrier wireless communication system.

45. The base station of claim 37, wherein the error detection signal transmitted by the base station is nearly orthogonal to an error detection signal transmitted by another base station that operates within the multi-carrier wireless communication system.

46. The base station of claim 37, wherein the base station transmits the error detection signal simultaneously with other base stations operating within the multi-carrier wireless communication system.

47. The base station of claim 37, wherein the error detection signal is periodically transmitted.

48. One or more propagated data signals collectively conveying an error detection signal between a mobile device and a base station in a multi-carrier wireless communication system having a plurality of base stations covering a geographic area divided into a plurality of cells, the one or more propagated data signals comprising:

a signal component that enables the mobile device to estimate a frequency error in a communication downlink between the mobile device in a cell and the base station serving that cell, wherein the signal component is orthogonal to a signal component conveyed between a mobile device and a base station in an adjacent one of the plurality of cells.

49. The one or more propagated data signals of claim 48, wherein the frequency error is a Doppler shift.

50. The one or more propagated data signals of claim 48, wherein the frequency error is a clock frequency error.

51. The one or more propagated data signals of claim 48, wherein the frequency error is a composite error comprising a Doppler shift and a clock frequency error.

52. The one or more propagated data signals of claim 48, wherein the signal component is selected from the group comprising:

a preamble, a midamble, a postamble, a code sequence, pilots, a control channel, or a control subchannel.

53. The one or more propagated data signals of claim 48, wherein the signal component is in the frequency domain.

54. The one or more propagated data signals of claim 48, wherein the signal component is in the time domain.