Embodiments of enabling a secondary cell in a massive MIMO system are generally described herein. An example apparatus of UE may include memory and processing circuitry to configure a MIMO transceiver to establish primary cell transmit and receive channels for communication with an eNodeB, and to receive a secondary cell addition signal that includes a preamble index for a secondary cell. The processing circuitry further configures the MIMO transceiver to receive beam reference signals (BRS), and select one of the BRS from the eNodeB as a secondary cell transmit channel for the secondary cell based on detected BRS receive power. The processing circuitry further configures the MIMO transceiver to provide information for the selected BRS, and provide xPRACH transmissions that include a transmit index to the eNodeB. The processing circuitry further configures the MIMO transceiver to receive selection of one of the xPRACH transmissions as a secondary cell receive channel.