CALIBRATION OF TRANSMIT AND RECEIVE CHAINS IN A MIMO COMMUNICATION SYSTEM

• US 20100183088A1
• Filed: 12/23/2008
• Published: 07/22/2010
• Est. Priority Date: 04/02/2004
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Inanoglu, Hakan
• Granted Patent: US 7,991,067 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 17/14 of the whole transmission and reception path, e.g. self-test loop-back
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end

Abstract

Techniques for calibrating the transmit and receive chains at a wireless entity are described. For a pre-calibration, N first overall gains for a receiver unit and N transmitter units in the transmit chain are obtained, where N>1. Each first overall gain is for a combined response for the receiver unit and the associated transmitter unit. N second overall gains for a transmitter unit and N receiver units in the receive chain are also obtained. Each second overall gain is for a combined response for the transmitter unit and the associated receiver unit. The gain of each transmitter unit and the gain of each receiver unit are determined based on the first and second overall gains. At least one correction matrix is then derived based on the gains of the transmitter and receiver units and is used to account for the responses of these units.

Claims

1. A computer-program apparatus for calibrating transmitter units and receiver units at a wireless entity in a multiple-input multiple-output (MIMO) communication system comprising one or more memory units having instructions stored thereon, the instructions being executable by one or more processors and the instructions comprising:

instructions for obtaining a plurality of first overall gains for a first receiver unit and a plurality of transmitter units, one first overall gain for each transmitter unit, each first overall gain indicative of a combined response for the first receiver unit and the associated transmitter unit, wherein the first receiver unit is one of a plurality of receiver units;

instructions for obtaining a plurality of second overall gains for a first transmitter unit and the plurality of receiver units, one second overall gain for each receiver unit, each second overall gain indicative of a combined response for the first transmitter unit and the associated receiver unit, wherein the first transmitter unit is one of the plurality of transmitter units;

instructions for determining a gain of each of the plurality of transmitter units based on the plurality of first overall gains; and

instructions for determining a gain of each of the plurality of receiver units based on the plurality of second overall gains.

2. The computer-program apparatus of claim 1, wherein the instructions for obtaining a plurality of first overall gains for a first receiver unit and a plurality of transmitter units includes, for each of the plurality of transmitter units:

instructions for sending a test signal to the transmitter unit,

instructions for receiving the test signal from the first receiver unit, and

instructions for determining the first overall gain for the first receiver unit and the transmitter unit based on a ratio of the received test signal to the sent test signal.

3. The computer-program apparatus of claim 1, wherein the gain of each transmitter unit is normalized by the gain of the first transmitter unit, and wherein the gain of each receiver unit is normalized by the gain of the first receiver unit.

4. The computer-program apparatus of claim 1, further comprising:

instructions for deriving at least one correction matrix based on gains of the plurality of transmitter units and gains of the plurality of receiver units, wherein the at least one correction matrix is used to account for responses of the plurality of transmitter units and responses of the plurality of receiver units.

5. The computer-program apparatus of claim 1, further comprising:

instructions for deriving a first correction matrix based on gains of the plurality of transmitter units, wherein the first correction matrix is used to account for responses of the plurality of transmitter units; and

instructions for deriving a second correction matrix based on gains of the plurality of receiver units, wherein the second correction matrix is used to account for responses of the plurality of receiver units.

6. The computer-program apparatus of claim 5, wherein the first correction matrix is an inverse of a first diagonal matrix with the gains of the plurality of transmitter units, and wherein the second correction matrix is an inverse of a second diagonal matrix with the gains of the plurality of receiver units.

7. The computer-program apparatus of claim 1, further comprising:

instructions for deriving a correction matrix based on gains of the plurality of transmitter units and gains of the plurality of receiver units, wherein the correction matrix is applied on a transmit path and is used to account for responses of the plurality of transmitter units and responses of the plurality of receiver units.

8. The computer-program apparatus of claim 7, wherein the correction matrix is set to a ratio of a first diagonal matrix with the gains of the plurality of receiver units to a second diagonal matrix with the gains of the plurality of transmitter units.

9. The computer-program apparatus of claim 1, further comprising:

instructions for deriving a correction matrix based on gains of the plurality of transmitter units and gains of the plurality of receiver units, wherein the correction matrix is applied on a receive path and is used to account for responses of the plurality of transmitter units and responses of the plurality of receiver units.

10. The computer-program apparatus of claim 9, wherein the correction matrix is set to a ratio of a first diagonal matrix with the gains of the plurality of transmitter units to a second diagonal matrix with the gains of the plurality of receiver units.

11. The computer-program apparatus of claim 1, wherein the MIMO communication system utilizes orthogonal frequency division multiplexing (OFDM), and wherein the instructions for obtaining a plurality of first overall gains, instructions for obtaining a plurality of second overall gains, instructions for determining a gain of each of the plurality of transmitter units, and instructions for determining a gain of each of the plurality of receiver units are performed for a plurality of subbands.

12. The computer-program apparatus of claim 1, wherein gains of the plurality of transmitter units and gains of the plurality of receiver units are determined for a plurality of operating points.

13. The computer-program apparatus of claim 12, wherein each operating point corresponds to a different gain setting or a different temperature.

14. A computer-program apparatus for calibrating transmitter units and receiver units at a wireless entity in a multiple-input multiple-output (MIMO) communication system comprising one or more memory units having instructions stored thereon, the instructions being executable by one or more processors and the instructions comprising:

instructions for performing a first calibration to obtain a gain of each of a plurality of transmitter units at the wireless entity and to obtain a gain of each of a plurality of receiver units at the wireless entity, wherein the first calibration is performed based on a plurality of test signals sent via the plurality of transmitter units and received via the plurality of receiver units; and

instructions for deriving at least one correction matrix based on gains of the plurality of transmitter units and gains of the plurality of receiver units, wherein the at least one correction matrix is used to account for responses of the plurality of transmitter units and responses of the plurality of receiver units.

15. The computer-program apparatus of claim 14, further comprising:

instructions for performing a second calibration to determine at least one updated correction matrix for the wireless entity, wherein the second calibration is performed based on a channel response estimate for a downlink and a channel response estimate for an uplink in the MIMO system.

16. The computer-program apparatus of claim 14, further comprising:

instructions for performing a third calibration to determine errors in the at least one correction matrix, wherein the third calibration is performed based on two different pilots exchanged with the wireless entity; and

instructions for updating the at least one correction matrix based on the determined errors in the at least one correction matrix.