UE aided antenna calibration

A base station of a cellular communications system, the base station comprising:

• a plurality of antenna branches each comprising a respective transmitter coupled to a respective antenna;
• at least one receiver;
• and
• at least one processor associated with the plurality of antenna branches and the at least one receiver, the at least one processor configured to cause the base station to:
• configure a user equipment, UE, for a first plurality of channel state information, CSI, reports associated to a respective first plurality of CSI reporting bands, the respective first plurality of CSI reporting bands being either:
• (a) different subsets of a plurality of sub-bands within a downlink bandwidth of the base station or (b) different downlink bandwidth parts served by the base station;
• receive the first plurality of CSI reports from the UE;
• estimate phase and delay errors for a plurality of transmit antenna branches of the base station;
• and
• compensate for the estimated phase and delay errors for the plurality of transmit antenna branches of the base station.

A method implemented in a base station for a cellular communications system, the method comprising:

• configuring a user equipment, UE, for a first plurality of channel state information, CSI, reports associated to a respective first plurality of CSI reporting bands, the respective first plurality of CSI reporting bands being either:
• (a) different subsets of a plurality of sub-bands within a downlink bandwidth of the base station or (b) different downlink bandwidth parts served by the base station;
• receiving the first plurality of CSI reports from the UE;
• and
• estimating phase and delay errors for a plurality of transmit antenna branches of the base station based on the plurality of CSI reports received from the UE,
• wherein the plurality of CSI reports is only two CSI reports, and wherein the CSI reporting band configuration for each of the two CSI reports is based on a delay range Δτmax.