Method and apparatus to improve channel quality for use in wireless communications systems with multiple-input multiple-output (MIMO) antennas

• US 7,583,982 B2
• Filed: 06/27/2005
• Issued: 09/01/2009
• Est. Priority Date: 08/06/2004
• Status: Expired due to Fees

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Olesen, Robert Lind, Bultan, Aykut, Kwak, Jaeyoung
• Primary Examiner(s): Urban; Edward
• Assistant Examiner(s): Hannon; Christian A
• Application Number:
  US11/167,736
• Publication Number:
  US 20060030364A1
• Time in Patent Office: 1,527 Days
• Field of Search: 455/101, 455/103, 455/500, 455/517, 455/562.1, 455/69, 455/506, 455/65, 455/132, 455/133, 455/67.11, 455/272, 455/450, 455/126, 455/277.1, 455/21, 455/24, 455/63.1, 455/66.1, 375/267, 375/299, 375/146, 375/152
• US Class Current: 455/562.1
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• 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 25/021 Estimation of channel covariance
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• 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

Abstract

A technique which improves SINR in a communication system utilizing MIMO antennas is described. Transmitter and receiver components use fixed transmit and receive beamforming matrices and variable transmit and receive beamforming vectors. A method of channel conditioning using an iterative closed loop process is also described.

Claims

1. A method of wireless multiple-input multiple-output (MIMO) antenna communication for a wireless transmit receive unit (WTRU):

receiving with a receiver having a plurality of N antennas a first set of signals from another WTRU and processing each signal by applying a different N-size RX beamforming vector of a predefined vector set across N signal paths to each signal;

measuring a preferred characteristic of each processed received signal;

selecting the processed received signal with a best characteristic from among the processed received signals;

identifying the RX beamforming vector that was used to produce the processed received signal with the best characteristic as a choice RX beamforming vector and implementing in the receiver the choice RX beamforming vector; and

processing a second set of signals for transmission by a transmitter having a plurality of M transmit (TX) antennas including;

defining a signal path for each of the M TX antennas;

applying a different M-size TX beamforming vector of a predefined vector set across the M signal paths to each signal of the second set of signals; and

processing each signal of the second set of signals with a unitary matrix; and

transmitting each processed signal of the second set of signals by the plurality of M antennas, whereby each transmitted signal of the second set of signals is selectively adjusted in direct correlation with the corresponding TX beamforming vector;

the transmitting each processed signal including transmitting an index of the TX beamforming vector that was used to produce the signal;

receiving an indication of which transmitted signal of the second set of signals had a best receive characteristic whereby the TX beamforming vector that was used to produce that transmitted signal is identified as a choice TX beamforming vector;

the receiving an indication including receiving the index of the TX beamforming vector that was identified as the choice TX beamforming vector to enable implementation of the choice TX beamforming vector in the transmitter; and

implementing in the transmitter the choice TX beamforming vector for further signal transmissions.

2. The method of claim 1 wherein the unitary matrix is a Butler matrix and the RX antennas and the TX antennas are the same antennas.

3. The method of claim 1 wherein the receiving a first set of signals from the other WTRU is performed with respect to a set of signals for which the same beamforming vector was applied in the other WTRU.

4. The method of claim 3 further comprising:

monitoring selected characteristics of signals received from the other WTRU after implementation of the choice RX beamforming vector in the receiver;

reconditioning the channel in response to selectively defined changes in the monitored characteristics by repeating the receiving, processing, measuring, selecting and identifying steps with respect to the predefined set of RX beamforming vectors to re-determine the choice RX beamforming vector; and

implementing the re-determined choice RX beamforming vector in the receiver.

5. A wireless transmit receive unit (WTRU) for use in wireless multiple-input multiple-output (MIMO) antenna communication comprising:

a plurality N of receive (RX) antennas, each having a signal path, configured to receive signals from another WTRU produced by applying a unitary matrix across transmit antenna signal paths;

a processor configured to process the signals received by the N antennas by applying a Hermitian of the unitary matrix and a selected N-size RX beamforming vector, whereby different weights are applied to the signal across the N signal paths in direct correlation with the applied RX beamforming vector;

a beamforming vector selection component associated with said processor configured to select the RX beamforming vector applied by the processor; and

a memory configured to store a plurality of indexed RX beamforming vectors associated with the RX beamforming vector selection component wherein the RX beamforming vector selection component is configured to successively select each indexed RX beamforming vector of a stored predefined vector set for application by the processor in connection with the determination and selection of a choice RX beamforming vector.

6. The WTRU of claim 5 further comprising:

a plurality M of transmit (TX) antennas, each having an associated signal path;

a processor configured to process a signal for transmission by the plurality of M antennas by applying a selectively determined M-size TX beamforming vector and a unitary matrix across the TX antenna signal paths whereby different weights are applied to the signals directed to each TX antenna for transmission in correlation with the applied TX beamforming vector;

a TX beamforming vector selection component associated with said processor configured to select the TX beamforming vector applied by the processor; and

a memory configured to store a plurality of indexed TX beamforming vectors associated with the TX beamforming vector selection component wherein the TX beamforming vector selection component is configured to successively select each indexed TX beamforming vector of a stored predefined vector set for application by the processor in connection with the determination and selection of a choice TX beamforming vector.

7. The WTRU of claim 6 wherein the TX beamforming vector selection component is associated with a receiving component and is configured to change the selection of a TX beamforming vector based on information received from a receiving station that is responsive to signals transmitted from said plurality M of transmit (TX) antennas.

8. The WTRU of claim 6 configured to transmit Orthogonal Frequency Division Multiplex signals wherein the RX antennas and the TX antennas are the same antennas.

9. The WTRU of claim 5 wherein the RX beamforming vector selection component includes:

a measuring device for measuring a preferred characteristic of the received signal; and

a comparator configured to compare measured values of the preferred characteristic to select a received signal with a best characteristic whereby the RX beamforming vector that produced the selected signal is selected as the choice RX beamforming vector.

10. The WTRU of claim 5 further comprising:

a component configured to measure a preferred characteristic of received signals and identify a TX beamforming vector that produced each respective measured signal;

a comparator configured to compare measured values of the preferred characteristic and to select a received signal with a best characteristic; and

a communication component configured to send information identifying TX beamforming vector that produced the selected signal having the best characteristic to the other WTRU.

11. The WTRU of claim 10 wherein the processor is configured to calculate a channel matrix based on a received signal and the beamforming vector selection component is configured to calculate choice RX and TX beamforming vectors based on the channel matrix, select the choice RX beamforming vector for use by the processor and to send information identifying the choice TX beamforming vector to the multi-antenna transmitting station that transmitted the received signal.

12. The WTRU of claim 5 configured to receive Orthogonal Frequency Division Multiplex signals.

13. A receiving station for use in wireless multiple-input multiple-output (MIMO) antenna communication comprising:

a plurality N of receive (RX) antennas, each having a signal path, configured to receive signals from a multi-antenna transmitting station produced by applying a TX beamforming vector and a unitary matrix across transmit antenna signal paths;

a processor configured to process the signals received by the N antennas by applying a Hermitian of the unitary matrix;

a component configured to measure a preferred characteristic of a set of received signals transmitted with different TX beamforming vectors and to identify the TX beamforming vector that produced each respective measured signal;

a comparator configured to compare measured values of the preferred characteristic and to select a received signal with a best characteristic; and

a communication component configured to send information identifying the TX beamforming vector that produced the selected signal having the best characteristic to the multi-antenna transmitting station that transmitted the set of signals.

14. The receiving station of claim 13 configured to receive Orthogonal Frequency Division Multiplex signals.

15. A method of wireless multiple-input multiple-output (MIMO) antenna communication for a receiving station comprising:

receiving by a receiver having a plurality of N receive (RX) antennas a set of signals, where each signal was transmitted by applying a different TX beamforming vector and a unitary matrix across transmit antenna signal paths, including;

defining a signal path for each of the N RX antennas;

processing each received signal of the set of signals with the Hermitian of the unitary matrix; and

applying an N-size RX beamforming vector; and

measuring a preferred characteristic of a set of received signals transmitted with different TX beamforming vectors and identifying the TX beamforming vector that produced each respective measured signal;

comparing measured values of the preferred characteristic and to select a received signal with a best characteristic; and

sending information identifying the TX beamforming vector that produced the selected signal having the best characteristic to the multi-antenna transmitting station that transmitted the set of signals.