Method and apparatus for providing closed-loop transmit precoding

• US 20060039489A1
• Filed: 07/15/2005
• Published: 02/23/2006
• Est. Priority Date: 08/17/2004
• Status: Abandoned Application

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Onggosanusi, Eko N., Dabak, Anand G., Hosur, Srinath, Ikram, Muhammad Z., Raghavan, Vasanthan, Varadarajan, Badrinarayanan
• Application Number:
  US11/182,083
• Publication Number:
  US 20060039489A1
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/0639 Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection
• CPC Class Codes: H04B 7/0663 using vector or matrix manipulations
• 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 2025/03802 Signalling on the reverse channel
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0248 Eigen-space methods
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling

Abstract

A method for providing closed-loop transmit precoding between a transmitter and a receiver, includes defining a codebook that includes a set of unitary rotation matrices. The receiver determines which preceding rotation matrix from the codebook should be used for each sub-carrier that has been received. The receiver sends an index to the transmitter, where the transmitter reconstructs the precoding rotation matrix using the index, and precodes the symbols to be transmitted using the preceding rotation matrix. An apparatus that employs this closed-loop technique is also described.

Claims

1. A method for providing closed-loop transmit precoding between a transmitter and a receiver, comprising:

defining a codebook that includes a set of precoding rotation matrices;

determining at the receiver a preceding rotation matrix from the codebook for each transmission sub-carrier that is received;

sending an index to the transmitter for each sub-carrier received;

reconstructing the precoding rotation matrix selected by the receiver for each sub-carrier at the transmitter using the indices sent to the transmitter; and

precoding information to be transmitted by the transmitter to the receiver using the reconstructed preceding rotation matrices.

2. A method as defined in claim 1, wherein the codebook is known to both the transmitter and the receiver.

3. A method as defined in claim 1, wherein the codebook is stored at both the transmitter and the receiver.

4. A method as defined in claim 1, wherein the receiver selects the precoding rotation matrix from among the set of rotation matrices for use for each sub-carrier.

5. A method as defined in claim 4, further comprising:

selecting the precoding rotation matrix from the codebook for use for each sub-carrier by determining which precoding rotation matrix maximizes post-processed signal-to-noise ratio.

6. A method as defined in claim 1, wherein sending the index comprises sending an index having a length of log2N bits, where N is the number of precoding rotation matrices found in the codebook.

7. A method as defined in claim 1, wherein the transmitter and receiver form a 2×

2 MIMO system and the codebook includes a set of N precoding rotation matricies denoted by V, where;

$V_{N_1<br><br>n_2+n_1}=\left[\begin{array}{cc}{\mathrm{e<br><br>}}^{j<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\varphi <br><br>}}_{n_2}}<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\theta <br><br>}}_{n_1}& -{\mathrm{e<br><br>}}^{j<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\varphi <br><br>}}_{n_2}}<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\theta <br><br>}}_{n_1}\\ \sin <br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\theta <br><br>}}_{n_1}& \cos <br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\theta <br><br>}}_{n_1}\end{array}\right],<br><br>{\mathrm{\varphi <br><br>}}_{n_2}=\frac{2<br><br>\mathrm{\pi <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>n_2}{N_2},n_2=0,1,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},N_2-1<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{where},<br><br>{\mathrm{\theta <br><br>}}_{n_1}=\frac{\mathrm{\pi <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>n_1}{2<br><br>N_1},n_1=0,1,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},N_1-1<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{and}$ $N=N_1<br><br>N_2.$

8. A communication system comprising:

a receiver including a codebook that includes one or more precoding rotation matrices; and

a transmitter transmitting information to the receiver using a sub-carrier;

wherein the receiver determines a precoding rotation matrix from the codebook for the sub-carrier and sends an index to the transmitter indicating the preceding rotation matrix the transmitter should use for the sub-carrier.

9. The communication system as defined in claim 8, wherein the transmitter includes a copy of the codebook.

10. The communication system as defined in claim 8, wherein the receiver sends an index to the transmitter for each sub-carrier received from the transmitter.

11. The communication system as defined in claim 8, wherein the communication system comprises an Orthogonal Frequency Division Multiple Access (OFDMA) system.

12. The communication system as defined in claim 8, wherein the index has a length of log₂N bits, where N is the number of precoding rotation matrices found in the codebook.

13. The communication system as defined in claim 8, wherein the precoding rotation matrix is selected from the codebook by the receiver on a metric that maximizes signal-to-noise ratio (SNR).

14. A communication system as defined in claim 13, wherein the transmitter transmits information using the precoding rotation matrix indicated by the index the transmitter received from the receiver.

15. The communication system as defined in claim 8, further comprising a feedback path coupling the receiver and transmitter via which the receiver sends the index to the transmitter.

16. The communication system as defined in claim 8, further defined as a wireless communication device and a remote access point, coupled by a wireless interconnection capability.

17. A receiver, comprising:

a plurality of antennas;

a memory adapted to store a codebook comprising one or more precoding rotation matrices; and

selection logic for choosing a precoding rotation matrix from among the one or more precoding rotation matrices based on information that has been received.

18. The receiver as defined in claim 17, wherein the antennas are further adapted to send an index informing a transmitter the precoding rotation matrix selected by the receiver to be used.

19. The receiver as defined in claim 18, wherein the receiver sends the transmitter an index for each sub-carrier used by the transmitter.

20. The receiver as defined in claim 17, wherein the selection logic selects the preceding rotation matrix which provides the maximum signal-to-noise ratio (SNR).

21. The receiver as defined in claim 17, wherein the receiver comprises an Orthogonal Frequency Division Multiple Access (OFDMA) Multi-Input-Multi-Output (MIMO) receiver.

22. A receiver, comprising:

means for storing one or more precoding rotation matrices; and

means for selecting a preceding rotation matrix from among the one or more precoding rotation matrices based on information that has been received.

23. The receiver as defined in claim 22, further comprising:

means for sending an index which informs a transmitter the precoding rotation matrix selected by the receiver to be used.

24. The receiver as defined in claim 23, wherein the receiver sends the transmitter an index for each sub-carrier used by the transmitter.

25. The receiver as defined in claim 24, wherein the receiver comprises an Orthogonal Frequency Division Multiple Access (OFDMA) Multi-Input-Multi-Output (MIMO) receiver.

26. The receiver as defined in claim 22, wherein the means for selecting the precoding rotation matrix from among the one or more precoding rotation matrices selects the precoding rotation matrix which provides the maximum signal-to-noise ratio (SNR).

27. A transmitter, comprising:

a plurality of antennas;

a memory adapted to store a codebook comprising one or more preceding rotation matrices; and

an indexing logic adapted to select which preceding rotation matrix should be used based on an index received by the antenna.

28. The transmitter as defined in claim 27, wherein the transmitter transmits information using the selected precoding rotation matrix indicated by the index.

29. The transmitter as defined in claim 27, further comprising reconstruction logic adapted to reconstruct the selected preceding rotation matrix using the index.

30. The transmitter as defined in claim 29, further comprising preceding logic adapted to precode information to be transmitted by the transmitter using the reconstructed precoding rotation matrix.