Adaptive downlink multi user multiple input multiple output (MU-MIMO)precoding using uplink signal subspace tracking for active antenna systems AAS

A method for a base station configured to communicate with a plurality of user equipments, UEs, the method comprising:

• tracking a downlink signal subspace for each UE of the plurality of UEs;
• and
• determining a Multi-User Multiple-Input Multiple-Output, MU-MIMO, precoder based on the tracked downlink signal subspace for each UE of the plurality of UEs, the MU-MIMO precoders being configured to at least in part suppress intra-cell MU-MIMO interference.

A first user equipment, UE, configured to communicate with a base station, the first UE comprising processing circuitry configured to:

• perform wireless communication using Multi-User Multiple-Input Multiple-Output, MU-MIMO, precoders, the MU-MIMO precoders being based on tracking of a downlink signal subspace for each UE of a plurality of UEs, the plurality of UEs including the first UE, the MU-MIMO precoders being configured to at least in part suppress intra-cell MU-MIMO interference.

A method of a first user equipment, UE, configured to communicate with a base station, the method comprising:

• performing wireless communication using Multi-User Multiple-Input Multiple-Output, MU-MIMO, precoders, the MU-MIMO precoders being based on tracking of a downlink signal subspace for each UE of a plurality of UEs, the plurality of UEs including the first UE, the MU-MIMO precoders being configured to at least in part suppress intra-cell MU-MIMO interference.