Controlling dl mimo transmissions in a communication system

A method in a base station for controlling transmissions to a user equipment (UE) over a downlink (DL) multiple-input, multiple-output (MIMO) channel, the method comprising:

• determining, by processing hardware, that the UE is configured to support N DL MIMO layers and transmit reference signals over L antenna chains;
• receiving, by the processing hardware, L uplink reference signals, each transmitted by the UE over a respective one of the L antenna chains;
• receiving, by the processing hardware from the UE, one or more additional transmissions including a hybrid automatic repeat request (HARQ) message or a scheduling request;
• in response to determining that L<N, generating, by the processing hardware, channel information for the DL MIMO channel using (i) the L uplink reference signals and (ii) the one or more additional transmissions received from the UE;
• and
• transmitting, by the processing hardware, a plurality of data streams over the DL MIMO channel in accordance with the generated channel information.