Antenna array calibration for wireless communication systems

• US 20060284725A1
• Filed: 04/04/2006
• Published: 12/21/2006
• Est. Priority Date: 06/16/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Naguib, Ayman Fawzy, Gorokhov, Alexei, Agrawal, Avneesh
• Granted Patent: US 8,498,669 B2
• Time in Patent Office: Days
• US Class Current: 340/7.390
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices

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 a plurality of forward link channel estimates received from at least some of the plurality of devices and a plurality of reverse link channel estimates from the plurality of devices.

Claims

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

receiving first channel estimate information corresponding to transmissions to a first access terminal;

determining second channel estimate information corresponding to transmissions from the first access terminal;

receiving third channel estimate information corresponding to transmissions to a second access terminal;

determining fourth channel estimate information corresponding to transmissions from the second access terminal; and

determining a calibration ratio based upon the first, second, third, and fourth channel estimate information for at least the first and second access terminals.

2. The method of claim 1, wherein determining the calibration ratio comprises:

determining a first calibration ratio based upon the first and second channel estimate information;

determining second calibration ratio based upon the third and fourth channel estimate information; and

determining the calibration ratio based upon combining the first and second calibration ratios.

3. The method of claim 2, wherein combining comprises averaging the first and second calibration ratios.

4. The method of claim 2, wherein the first and second calibration ratios comprise a plurality of elements each corresponding to at least one antenna of an access point in communication with the fist and second access terminals, and wherein combining comprises:

normalizing the first calibration ratio;

normalizing the second calibration ratio; and

determining the calibration ratio based upon a matrix including the first and second calibration ratio.

5. The method of claim 4, wherein determining the calibration ratio based upon the matrix comprises decomposing the matrix utilizing singular value decomposition.

6. The method of claim 1, wherein determining the calibration ratio comprises determining a joint calibration ratio based upon the first, second, third, and fourth channel estimate information.

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

$\begin{array}{c}{g}_{i,k,u}={\mathrm{\gamma <br><br>}}_u·<br><br>{\mathrm{e<br><br>}}^{-j<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\omega <br><br>}}_i<br><br>{\mathrm{\tau <br><br>}}_u}·<br><br>\mathrm{diag}<br><br>\left(h_{i,k,u}\right)·<br><br>\mathrm{\eta <br><br>}+n_{i,k,u}\\ ={\mathrm{\gamma <br><br>}}_{i,k,u}·<br><br>Z_{i,k,u}·<br><br>\mathrm{\eta <br><br>}+n_{i,k,u}\end{array}$

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

_i,u=γ

_u·

e<sup>−

jω

iτ

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

8. The method of claim 7, wherein solving comprising using an MMSE technique to solve the equation.

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

10. The method of claim 1, further comprising

receiving fifth channel estimate information corresponding to transmissions to a third access terminal;

determining sixth channel estimate information corresponding to transmissions from the third access terminal; and

determining a calibration ratio based upon the first, second, third, fourth, fifth, and sixth channel estimate information for at least the first, second, and third access terminals.

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 a plurality of forward link channel estimates and reverse link channel estimates from a plurality of access terminals, for communication with each of the plurality of 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 access terminals.

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:

$\begin{array}{c}{g}_{i,k,u}={\mathrm{\gamma <br><br>}}_u·<br><br>{\mathrm{e<br><br>}}^{-j<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\omega <br><br>}}_i<br><br>{\mathrm{\tau <br><br>}}_u}·<br><br>\mathrm{diag}<br><br>\left(h_{i,k,u}\right)·<br><br>\mathrm{\eta <br><br>}+n_{i,k,u}\\ ={\mathrm{\gamma <br><br>}}_{i,k,u}·<br><br>Z_{i,k,u}·<br><br>\mathrm{\eta <br><br>}+n_{i,k,u}\end{array}$

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

_i,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 forward link channel estimates and reverse link channel estimates from the plurality of access terminals.

20. An apparatus comprising:

means for receiving first channel estimate information corresponding to transmissions to at least two access terminals;

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

means for determining a calibration ratio based upon the first and second channel estimate information for at the least first and second access terminals.

21. The apparatus of claim 20, wherein the means for determining the calibration ratio comprises means for determining a different calibration ratio for each of the at least two access terminals and combining the different calibration ratios.

22. The apparatus of claim 21, wherein the means for combining comprises means for averaging the different calibration ratios.

23. The apparatus of claim 21, wherein the different calibration ratios comprise a plurality of elements, and wherein means for determining comprises:

means for normalizing each of the different calibration ratios; and

means for determining the calibration ratio based upon a matrix including the first and second calibration ratio.

24. The apparatus of claim 20, wherein the means for determining the calibration ratio comprises means for determining a joint calibration ratio based upon the first and second channel estimate information for at the least first and second access terminals.

25. 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 for at the least first and second access terminals.

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

determine a plurality of reverse link channel estimates for a plurality of access terminals; and

determine a calibration ratio, based upon a plurality of forward link channel estimates received from at least some of the plurality of access terminals and the plurality of reverse link channel estimates from the plurality of access terminals.