Systems and methods are disclosed herein that related to determining and using a codebook in a virtualized Active Antenna System (AAS). In some embodiments, a first radio node that is configured to communicate with a second radio node comprises a radio interface and processing circuitry configured to transform a first codebook that is in a non-virtualized antenna domain to a second codebook that is in a virtualized antenna domain based on a port to antenna mapping matrix used to transform a signal from the virtualized antenna domain to the non-virtualized antenna domain prior to transmission of the signal in a corresponding virtualized cell or sector. The processing circuitry is further configured to receive a transmit signal from the second radio node to thereby provide a received signal and perform Precoding Matrix Indication (PMI) estimation based on the received signal using the second codebook in the virtualized antenna domain.