METHOD AND APPARATUS FOR TRANSMITTING DATA IN A TIME DIVISION DUPLEXED (TDD) COMMUNICATION SYSTEM

• US 20080107048A1
• Filed: 12/21/2007
• Published: 05/08/2008
• Est. Priority Date: 06/22/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Jalali, Ahmad, Wallace, Mark, Smee, John
• Granted Patent: US 7,729,444 B2
• Time in Patent Office: Days
• US Class Current: 370/280
• CPC Class Codes: H04B 7/0434 using multiple eigenmodes
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0013 Rate matching, e.g. puncturing or repetition of code symbols
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0032 Without explicit signalling
• CPC Class Codes: H04L 1/0034 where the transmitter decides based on inferences, e.g. use of implicit signalling
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0023 Time-frequency-space

Abstract

Techniques to process data for transmission in a time division duplexed (TDD) communication system. In one aspect, the frequency response of a forward link is estimated at a base station based on reverse link transmissions (e.g., pilots) from a terminal. Prior to a data transmission on the forward link, the base station determines a reverse transfer function based on the pilots transmitted by the terminal, “calibrates” the reverse transfer function with a calibration function to derive an estimate of a forward transfer function, and preconditions modulation symbols based on weights derived from the forward transfer function. In another aspect, the terminal estimates the “quality” of the forward link and provides this information to the base station. The base station then uses the information to properly code and modulate data prior to transmission such that the transmitted data can be received by the terminal at the desired level of performance.

Claims

1. A method for performing data processing in a wireless communication system, the method comprising:

calibrating at least one communication link between a base station and a terminal;

obtaining a channel response estimate for the at least one communication link based on one or more pilots; and

deriving at least one eigenvector from the channel response estimate usable for spatial processing of the at least one communication link.

2. The method of claim 1 wherein deriving comprises decomposing a matrix corresponding to the channel response estimate.

3. The method of claim 1 further comprising performing spatial processing for data transmissions on at least one communication link using the at least one eigenvector.

4. The method of claim 1 wherein performing spatial processing comprises transmitting a pilot on a second link, in a direction opposite the first link, using the one or more eigenvectors.

5. The method of claim 1—

wherein calibrating comprises calibrating based upon a calibration function.

6. The method of claim 5 further comprising determining the calibration function based upon a forward link calibration function and a reverse link calibration function.

7. The method of claim 1 wherein the wireless communication system implements orthogonal frequency division modulation (OFDM), and wherein the at least one communication link comprises a plurality of frequency subchannels.

8. The method of claim 1 wherein the wireless communication system communication system implements multiple-input multiple-output (MIMO), and wherein the communication link comprises a plurality of spatial subchannels.

9. The method of claim 1 wherein the at least one communication link comprises a plurality of propagation paths, each propagation path corresponding to a path between a particular antenna at the base station and a particular antenna at the terminal.

10. The method of claim 1 wherein the channel response estimate relates to frequency response of propagation paths used to transmit to the terminal.

11. An apparatus for performing data processing in a wireless communication system comprising:

means for calibrating at least one communication link between a base station and a terminal;

means for obtaining a channel response estimate for the at least one communication link based on one or more pilots; and

means for decomposing the channel response estimate to obtain one or more eigenvectors usable for spatial processing of the one or more communication links.

12. The apparatus of claim 11 wherein the means for calibrating comprises:

means for determining a reverse link calibration function; and

means for applying the forward link calibration function and a reverse link calibration function.

13. The apparatus of claim 11 wherein the means for calibrating comprises means for calibrating based upon a calibration function.

14. The apparatus of claim 13 wherein the means for calibrating comprises means for determining the calibration function based upon a forward link calibration function and a reverse link calibration function.

15. The apparatus of claim 11 wherein the wireless communication system implements orthogonal frequency division modulation (OFDM), and wherein the at least one communication link comprises a plurality of frequency subchannels.

16. The apparatus of claim 11 wherein the wireless communication system communication system implements multiple-input multiple-output (MIMO), and wherein the communication link comprises a plurality of spatial subchannels.

17. The apparatus of claim 11 wherein the channel response estimate relates to frequency response of propagation paths used to transmit to the terminal.

24. The apparatus of claim 11 wherein the estimated characteristics relate to frequency response of propagation paths used to transmit from the wireless communication unit.

18. A wireless communication unit in a time division duplexed (TDD) communication system, comprising:

a processor configured to estimate characteristics of a communication link based on a received first transmission, to derive a calibration function indicative of a difference between the first transmission and a second transmission, and to precondition modulation symbols based on weights derived at least in part from the estimated characteristics and on the calibration function; and

a plurality of antennas coupled with the processor.

19. The wireless communication unit of claim 18 wherein the processor is further configured to determine the calibration function by determining a difference between a first transfer function determined based upon the first transmission and a second transfer function determined based upon the second transmission.

20. The wireless communication unit of claim 18 wherein the first transmission comprise pilot symbols.

21. The wireless communication unit of claim 18 wherein the second transmission comprises an estimate of pilot transmissions transmitted in a direction opposite of the first transmission.

22. The wireless communication unit of claim 18 wherein the wireless communication unit implements orthogonal frequency division modulation (OFDM), and wherein the communication link comprises a plurality of frequency subchannels.

23. The wireless communication unit of claim 18 wherein the communication link comprises a plurality of spatial subchannels.