Method and apparatus for a cluster specific cloud radio transmission and reception

A cloud radio access network (C-RAN) comprising:

• a reference signals transmission unit configured to:
• transmit a channel state information (CSI) reference signals to a plurality of user equipments (UEs);
• a downlink CSI reception unit configured to:
• receive a measured downlink (DL) CSI from each UE among the plurality of UEs, wherein the DL CSI corresponds to a plurality of antenna ports associated with a set of remote radio heads (RRHs) in a cluster;
• an uplink CSI estimation unit configured to:
• estimate an uplink (UL) CSI for each UE antenna port, wherein the UL CSI is estimated using a pre-defined pilot structure received from each UE;
• and
• a calibration coefficient derivation unit configured to:
• derive a calibration coefficient for each RRH and UE antenna port pair based on the measured DL CSI and the estimated UL CSI.

A computer program product comprising computer executable program code recorded on a computer readable non-transitory storage medium, the computer executable program code when executed causing the actions including:

• transmitting a channel state information (CSI) reference signals to a plurality of user equipments (UEs);
• receiving a measured downlink (DL) CSI from each UE among the plurality of UEs, wherein the DL CSI corresponds to a plurality of antenna ports associated with a set of remote radio heads (RRHs) in a cluster;
• estimating an uplink (UL) CSI for each UE, wherein the UL CSI is estimated using a pre-defined pilot structure received from each UE antenna port;
• and
• deriving a calibration coefficient for each RRH and UE antenna port pair based on the measured DL CSI and the estimated UL CSI.