A closed loop MIMO feedback system is described in which the number of available antenna ports is less than the number of antenna elements. In one implementation, sounding reference signals, received from a number of UEs, may be used, by a base station, to generate and transmit a number of OFDMA Channel State Information Reference Signals (CSI-RSs). The OFDMA CSI-RSs may be determined based on the top eigen beams associated with an average channel covariance matrix determined based on the received sounding reference signals. A UE, in response to receiving the OFDMA CSI-RSs, may determine a preferred eigen beam and transmit a quantized version of the preferred eigen beam back to the eNB. Subsequent communications with the UE may be made using beamforming techniques that are based on the quantized version of the preferred eigen beam.