Antenna array calibration for multi-input multi-output wireless communication systems

• US 20070099573A1
• Filed: 04/17/2006
• Published: 05/03/2007
• Est. Priority Date: 11/02/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Gorokhov, Alexei, Naguib, Ayman
• Granted Patent: US 8,280,430 B2
• Time in Patent Office: Days
• US Class Current: 455/67.11
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices
• CPC Class Codes: H04B 17/12 of transmit antennas, e.g. of the amplitude or phase
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements
• CPC Class Codes: H04B 17/336 Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/063 Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection
• CPC Class Codes: H04L 25/0204 of multiple channels

Abstract

Calibration for a transmit chain of a device transmitting information to multiple devices over wireless links and receive chains of the multiple devices receiving information over one of the wireless links utilizing each of the estimates for different antennas of an access terminal as a separate estimate.

Claims

1. A method of calibrating an antenna array in a wireless network, comprising:

receiving first channel estimate information each corresponding to transmissions to at least two antennas of at least two access terminals;

determining second channel estimate information each corresponding to transmissions from the at least two antennas of the at least two access terminals; and

determining a calibration ratio based upon each of the first channel estimate information and each of the second channel estimate information.

2. The method of claim 1, wherein determining the calibration ratio comprises determining a calibration ratio for each antenna independently.

3. The method of claim 2, wherein determining comprises combining each of the calibration ratios.

4. The method of claim 3, wherein combining comprises averaging each of the calibration ratios.

5. The method of claim 3, wherein each of the calibration ratios comprise a plurality of elements and wherein combining comprises:

normalizing each calibration ratio; and

determining the calibration ratio based upon a matrix including the normalized calibration ratios.

6. The method of claim 5, wherein determining the calibration ratio based upon the matrix comprises decomposing the matrix utilizing singular value decomposition.

7. The method of claim 1, wherein determining the calibration ratio comprises determining a joint calibration ratio based upon first calibration information and the second calibration information.

8. The method of claim 1, wherein determining the calibration ratio comprises solving the equation:

$\begin{array}{c}{g}_{i,k,u}={\mathrm{\gamma <br><br>}}_u·<br><br>{\mathrm{e<br><br>}}^{-{\mathrm{j\omega <br><br>}}_i<br><br>{\mathrm{\tau <br><br>}}_u}·<br><br>\mathrm{diag}<br><br>\left(h_{i,k,u}\right)·<br><br>\mathrm{\eta <br><br>}+n_{i,k,u}\\ ={\mathrm{\gamma <br><br>}}_{i,k,u}·<br><br>Z_{i,k,u}·<br><br>\mathrm{\eta <br><br>}+n_{i,k,u}\end{array}$

where Z_i,k,u is a diagonal matrix whose diagonal elements are the elements of the channel estimate information h_i,k,u, γ

_i,k,u=γ

_u·

e<sup>−

jω

iτ

u</sup>, and the subscripts i,k,u, are the tone, time, and user indexes, respectively.

9. The method of claim 8, wherein solving comprising using an MMSE technique to solve the equation.

10. The method of claim 1, wherein determining the calibration ratio comprises utilizing a joint optimization scheme with the first and second channel estimate information.

11. An wireless communication apparatus comprising:

at least two antennas; and

a processor coupled with the at least two antennas, the processor configured to determine a calibration ratio, based upon first channel estimate information each corresponding to transmissions to at least two antennas of at least two access terminals and second channel estimate information each corresponding to transmissions from the at least two antennas of the at least two access terminals.

12. The wireless communication apparatus of claim 11, wherein the processor is configured to determine a calibration ratio for each access terminal of the plurality and to determine the calibration ratio based upon combining each of the calibration ratios for each of the antennas.

13. The wireless communication apparatus of claim 12, wherein the processor is configured to combine the ratios by averaging each of the calibration ratios.

14. The wireless communication apparatus of claim 12, wherein the processor is configured to combine the ratios by normalizing each calibration ratio and to determine the calibration ratio based upon a matrix including each of the calibration ratios.

15. The wireless communication apparatus of claim 14, wherein the processor is configured utilize singular value decomposition to decompose the matrix to obtain the calibration ratio.

16. The wireless communication apparatus of claim 11, wherein the processor is configured to determine the calibration ratio utilizing a joint calibration ratio.

17. The wireless communication apparatus of claim 11, wherein the processor is configured to determine the calibration ratio by solving the equation:

$\begin{array}{c}{g}_{i,k,u}={\mathrm{\gamma <br><br>}}_u·<br><br>{\mathrm{e<br><br>}}^{-{\mathrm{j\omega <br><br>}}_i<br><br>{\mathrm{\tau <br><br>}}_u}·<br><br>\mathrm{diag}<br><br>\left(h_{i,k,u}\right)·<br><br>\mathrm{\eta <br><br>}+n_{i,k,u}\\ ={\mathrm{\gamma <br><br>}}_{i,k,u}·<br><br>Z_{i,k,u}·<br><br>\mathrm{\eta <br><br>}+n_{i,k,u}\end{array}$

where Z_i,k,u is a diagonal matrix whose diagonal elements are the elements of a reverse link channel vector estimate h_i,k,u, γ

_i,k,u=γ

_u·

e<sup>−

jω

iτ

u</sup>, and the subscripts i,k,u, are the tone, time, and user indexes, respectively.

18. The wireless communication apparatus of claim 17, wherein the processor is configured to solve the equation by using an MMSE technique.

19. The wireless communication apparatus of claim 17, wherein the processor is configured to determine the calibration ratio comprises utilizing a joint optimization scheme with the plurality of first and second channel estimate information.

20. An apparatus comprising:

means for processing first channel estimate information each corresponding to transmissions to at least two antennas of at least two access terminals and received from the at least two access terminals;

means for determining second channel estimate information each corresponding to transmissions from the at least two antennas of the at least two access terminals; and

means for determining a calibration ratio based upon each of the first channel estimate information and each of the second channel estimate information.

21. The apparatus of claim 20, wherein the means for determining the calibration ratio comprises means for determining a calibration ratio for each antenna independently.

22. The apparatus of claim 21, wherein the means for determining the calibration ratio for each antenna independently comprises means for combining each of the calibration ratios.

23. The apparatus of claim 22, wherein the means for combining comprises means for averaging each of the calibration ratios.

24. The method of claim 22, wherein each of the calibration ratios comprise a plurality of elements and wherein the means for combining comprises:

means for normalizing each calibration ratio; and

means for determining the calibration ratio based upon a matrix including the normalized calibration ratios.

25. The apparatus of claim 20, wherein the means for determining comprises means for determining a joint calibration ratio based upon first calibration information and the second calibration information.

26. The apparatus of claim 20, wherein the means for determining the calibration ratio comprises means for solving the equation:

$\begin{array}{c}{g}_{i,k,u}={\mathrm{\gamma <br><br>}}_u·<br><br>{\mathrm{e<br><br>}}^{-{\mathrm{j\omega <br><br>}}_i<br><br>{\mathrm{\tau <br><br>}}_u}·<br><br>\mathrm{diag}<br><br>\left(h_{i,k,u}\right)·<br><br>\mathrm{\eta <br><br>}+n_{i,k,u}\\ ={\mathrm{\gamma <br><br>}}_{i,k,u}·<br><br>Z_{i,k,u}·<br><br>\mathrm{\eta <br><br>}+n_{i,k,u}\end{array}$

where Z_i,k,u is a diagonal matrix whose diagonal elements are the elements of the channel estimate information h_i,k,u, γ

_i,k,u=γ

_u·

e<sup>−

jω

iτ

u</sup>, and the subscripts i,k,u, are the tone, time, and user indexes, respectively.

27. The apparatus of claim 20, wherein the means for determining the calibration ratio comprises means for utilizing a joint optimization scheme with the first and second channel estimate information.

28. A processor-readable medium having stored thereon instructions for use by a processor, the instructions comprise instructions to:

process first channel estimate information each corresponding to transmissions to at least two antennas of at least two access terminals and received from the at least two access terminals;

determine second channel estimate information each corresponding to transmissions from the at least two antennas of the at least two access terminals; and

determine a calibration ratio based upon each of the first channel estimate information and each of the second channel estimate information.