Beamforming feedback options for mu-mimo

Abstract

Beamforming may be used in MIMO communication systems to further enhance spectral efficiency. Beamforming refers to beamed transmissions to a single destination (e.g., a station) at a time, to enhance the rate and/or range of transmission. To perform beamforming from a source to one or more destinations, a channel and/or beamforming matrices corresponding to the channel needs to be known at the source, which may be obtained as feedback from the destination. However, the beamforming matrices may not be smooth over frequency as it is fed back from the destination. Therefore, certain aspects of the present disclosure provide beamforming feedback options, resulting in the smoothness of a beamforming matrix.

What is claimed is: 
     
         1 . A method for wireless communications, comprising:
 receiving feedback that is generated by a receiver;   receiving, from the receiver, an indication that maximum-likelihood (ML) detection or minimum mean square error (MMSE) detection is used for reception; and   transmitting signals, to the receiver, based on the feedback and the indication.   
     
     
         2 . The method of  claim 1 , wherein transmitting comprises determining how many spatial streams to beamform based on the indication received. 
     
     
         3 . The method of  claim 1 , wherein transmitting comprises determining to transmit in an open-loop fashion based on the indication received. 
     
     
         4 . The method of  claim 1 , wherein the feedback comprises at least one of channel state information (CSI) feedback, compressed beamforming matrix feedback, and non-compressed beamforming matrix feedback. 
     
     
         5 . An apparatus for wireless communications, comprising:
 logic for receiving feedback that is generated by a receiver;   logic for receiving, from the receiver, an indication that maximum-likelihood (ML) detection or minimum mean square error (MMSE) detection is used for reception; and   logic for transmitting signals, to the receiver, based on the feedback and the indication.   
     
     
         6 . The apparatus of  claim 5 , wherein the logic for transmitting comprises logic for determining how many spatial streams to beamform based on the indication received. 
     
     
         7 . The apparatus of  claim 5 , wherein the logic for transmitting comprises logic for determining to transmit in an open-loop fashion based on the indication received. 
     
     
         8 . The apparatus of  claim 5 , wherein the feedback comprises at least one of channel state information (CSI) feedback, compressed beamforming matrix feedback, and non-compressed beamforming matrix feedback. 
     
     
         9 . An apparatus for wireless communications, comprising:
 means for receiving feedback that is generated by a receiver;   means for receiving, from the receiver, an indication that maximum-likelihood (ML) detection or minimum mean square error (MMSE) detection is used for reception; and   means for transmitting signals, to the receiver, based on the feedback and the indication.   
     
     
         10 . The apparatus of  claim 9 , wherein the means for transmitting comprises means for determining how many spatial streams to beamform based on the indication received. 
     
     
         11 . The apparatus of  claim 9 , wherein the means for transmitting comprises means for determining to transmit in an open-loop fashion based on the indication received. 
     
     
         12 . The apparatus of  claim 9 , wherein the feedback comprises at least one of channel state information (CSI) feedback, compressed beamforming matrix feedback, and non-compressed beamforming matrix feedback. 
     
     
         13 . A computer-program product for wireless communications, comprising a computer-readable medium having instructions stored thereon, the instructions being executable by one or more processors and the instructions comprising:
 instructions for receiving feedback that is generated by a receiver;   instructions for receiving, from the receiver, an indication that maximum-likelihood (ML) detection or minimum mean square error (MMSE) detection is used for reception; and   instructions for transmitting signals, to the receiver, based on the feedback and the indication.   
     
     
         14 . The computer-program product of  claim 13 , wherein the instructions for transmitting comprises instructions for determining how many spatial streams to beamform based on the indication received. 
     
     
         15 . The computer-program product of  claim 13 , wherein the instructions for transmitting comprises instructions for determining to transmit in an open-loop fashion based on the indication received. 
     
     
         16 . The computer-program product of  claim 13 , wherein the feedback comprises at least one of channel state information (CSI) feedback, compressed beamforming matrix feedback, and non-compressed beamforming matrix feedback.