Reference signals and link adaptation for massive mimo

A method for wireless communications by a user equipment (UE), comprising:

• transmitting sounding reference signals (SRS) and at least one of:
• feedback regarding interference or a whitening matrix to a base station (BS);
• receiving beamformed channel state information reference signals (CSI-RS) from the BS;
• determining CSI feedback based on the beamformed CSI-RS;
• and
• transmitting the CSI feedback to the BS.

A method for wireless communications, by a user equipment (UE), comprising:

• transmitting one or more sounding reference signals (SRS) to a base station (BS);
• receiving a data packet from the BS;
• and
• reporting demodulation quality feedback to the BS based on the received data packet.

A method for wireless communications, by a base station (BS), comprising:

• receiving one or more sounding reference signals (SRS) from a user equipment (UE);
• transmitting a data packet to the UE;
• receiving demodulation quality feedback from the UE based on the data packet;
• and
• selecting at least one of:
• a modulation scheme or a coding rate for transmitting to the UE based on the demodulation quality feedback.

An apparatus for wireless communications by a base station (BS), comprising:

• means for receiving sounding reference signals (SRS) and at least one of:
• feedback regarding interference or a whitening matrix from one or more user equipments (UEs);
• means for determining beamforming parameters for transmissions to a group of one or more UEs based, at least in part, on the SRS and at least one of:
• the feedback regarding interference or the whitening matrix;
• and
• means for transmitting channel state information reference signals (CSI-RS) to UEs in the group using the determined beamforming parameters.

An apparatus for wireless communications by a user equipment (UE), comprising:

• means for transmitting sounding reference signals (SRS) and at least one of:
• feedback regarding interference or a whitening matrix to a base station (BS);
• means for receiving beamformed channel state information reference signals (CSI-RS) from the BS;
• means for determining CSI feedback based on the beamformed CSI-RS;
• and
• means for transmitting the CSI feedback to the BS.