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

Abstract

Apparatus and method that employ a technique which improves SINR in a communication system utilizing MIMO antennas are 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.

1 . A wireless transmit receive unit (WTRU) for use in wireless multiple-input multiple-output (MIMO) antenna communication comprising:
 a plurality of transmit (TX) antennas, each having an associated signal path;   a processor configured to process a signal for transmission by the plurality of TX antennas by applying a selectively determined 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.   
   
   
       2 . The WTRU of  claim 1  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 the plurality of TX antennas. 
   
   
       3 . The WTRU of  claim 1  configured to transmit Orthogonal Frequency Division Multiplex signals. 
   
   
       4 . The WTRU of  claim 1  wherein the processor is configured to apply a Butler matrix across the TX antenna signal paths as the unitary matrix. 
   
   
       5 . The WTRU of  claim 1  further comprising:
 a serial/parallel processor configured to divide the signal for transmission into parallel steams to thereby define the beginning of the respective TX antenna signal paths.   
   
   
       6 . The WTRU of  claim 1  further comprising:
 a modulator configured to modulate the signal for transmission using quadrature amplitude modulation before the processor applies the selectively determined TX beamforming vector.   
   
   
       7 . The WTRU of  claim 1  wherein the processor is configured to process the signal for transmission by inserting a pilot signal on each TX antenna signal path, processing the combined data-pilot signal using an inverse fast Fourier transform (IFFT) on each TX antenna signal path and adding a cyclic prefix on each TX antenna signal path after applying the selectively determined TX beamforming vector and before applying the unitary matrix across the TX antenna signal paths. 
   
   
       8 . The WTRU of  claim 7  further comprising:
 a serial/parallel processor configured to divide the signal for transmission into parallel steams to thereby define the beginning of the respective TX antenna signal paths.   
   
   
       9 . The WTRU of  claim 8  further comprising:
 a modulator configured to modulate the signal for transmission using quadrature amplitude modulation before the processor applies the selectively determined TX beamforming vector.   
   
   
       10 . The WTRU of  claim 9  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 the plurality of TX antennas. 
   
   
       11 . The WTRU of  claim 9  configured to transmit Orthogonal Frequency Division Multiplex signals wherein the processor is configured to apply a Butler matrix across the TX antenna signal paths as the unitary matrix. 
   
   
       12 . A method of wireless multiple-input multiple-output (MIMO) antenna communication comprising:
 processing a set of signals for transmission by wireless transmit receive unit (WTRU) having a plurality of transmit (TX) antennas including:
 defining a signal path for each of the TX antennas; 
 applying a different TX beamforming vector of a predefined vector set across the signal paths to each signal of the set of signals; and 
 processing each signal of the set of signals with a unitary matrix; and 
   transmitting each processed signal of the set of signals by the plurality of TX antennas, whereby each transmitted signal of the set of signals is selectively adjusted in direct correlation with the corresponding TX beamforming vector;   receiving an indication of which transmitted signal of the 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 beamforming vector; and   implementing in the WTRU the choice beamforming vector for further signal transmissions.   
   
   
       13 . The method of  claim 12  wherein the unitary matrix is a Butler matrix. 
   
   
       14 . The method of  claim 12  where the set of stored TX beamforming vectors are indexed wherein:
 the transmitting each processed signal includes transmitting an index of the TX beamforming vector that was used to produce the signal; and   the receiving an indication includes receiving the index of the TX beamforming vector that was identified as the choice beamforming vector to enable implementation of the choice beamforming vector in the transmitter.   
   
   
       15 . The method of  claim 12  further comprising:
 using a serial/parallel processor to divide a signal for transmission into parallel steams to thereby define the set of signals.   
   
   
       16 . The method of  claim 12  further comprising:
 modulating the set of signals using quadrature amplitude modulation before applying the TX beamforming vector.   
   
   
       17 . The method of  claim 12  further comprising:
 inserting a pilot signal;   processing the combined data-pilot signal using an inverse fast Fourier transform (IFFT); and   adding a cyclic prefix   
     with respect to each signal of the set of signals after applying the TX beamforming vector and before applying the unitary matrix across the TX antenna signal paths. 
   
   
       18 . The method of  claim 17  further comprising:
 using a serial/parallel processor to divide a signal for transmission into parallel steams to thereby define the set of signals.   
   
   
       19 . The method of  claim 18  further comprising:
 modulating the set of signals using quadrature amplitude modulation before applying the TX beamforming vector.   
   
   
       20 . The method of  claim 19  where the set of stored TX beamforming vectors are indexed wherein:
 the transmitting each processed signal includes transmitting an index of the TX beamforming vector that was used to produce the signal; and   the receiving an indication includes receiving the index of the TX beamforming vector that was identified as the choice beamforming vector to enable implementation of the choice beamforming vector in the transmitter.