A User Equipment, UE, comprising: a wireless transceiver, configured to perform wireless transmission and reception to and from a cellular station; and a controller, configured to select a downlink reference signal associated with a candidate beam among a plurality of downlink reference signals comprising a combination of Channel State Information-Reference Signal, CSI-RS, resources, Synchronization Signal, SS, blocks, and Physical Broadcast Channel, PBCH, blocks, determine one set from a plurality of sets of Physical Random Access Channel, PRACH, preambles and RACH occasions for the selected downlink reference signal according to an association configured between the downlink reference signals and PRACH resources, and use the determined set of PRACH preamble and RACH occasion to perform a PRACH transmission to the cellular station via the wireless transceiver, characterized in that the association configured between the downlink reference signals and the PRACH resources associates one CSI-RS resource, SS block, or PBCH block to one set of PRACH resources, or associates multiple CSI-RS resources, SS blocks, or PBCH blocks to one set of PRACH resources, wherein, when the association configured between the downlink reference signals and the PRACH resources associates multiple CSI-RS resources, SS blocks, or PBCH blocks to one set of PRACH resources, the controller is further configured to transmit an uplink transmission to the cellular station via the wireless transceiver for identifying which one of the multiple CSI-RS resources, SS blocks, or PBCH blocks is associated with the candidate beam. a wireless transceiver, configured to perform wireless transmission and reception to and from a cellular station; and a controller, configured to select a downlink reference signal associated with a candidate beam among a plurality of downlink reference signals comprising a combination of Channel State Information-Reference Signal, CSI-RS, resources, Synchronization Signal, SS, blocks, and Physical Broadcast Channel, PBCH, blocks, determine one set from a plurality of sets of Physical Random Access Channel, PRACH, preambles and RACH occasions for the selected downlink reference signal according to an association configured between the downlink reference signals and PRACH resources, and use the determined set of PRACH preamble and RACH occasion to perform a PRACH transmission to the cellular station via the wireless transceiver, characterized in that the association configured between the downlink reference signals and the PRACH resources associates one CSI-RS resource, SS block, or PBCH block to one set of PRACH resources, or associates multiple CSI-RS resources, SS blocks, or PBCH blocks to one set of PRACH resources, wherein, when the association configured between the downlink reference signals and the PRACH resources associates multiple CSI-RS resources, SS blocks, or PBCH blocks to one set of PRACH resources, the controller is further configured to transmit an uplink transmission to the cellular station via the wireless transceiver for identifying which one of the multiple CSI-RS resources, SS blocks, or PBCH blocks is associated with the candidate beam. select a downlink reference signal associated with a candidate beam among a plurality of downlink reference signals comprising a combination of Channel State Information-Reference Signal, CSI-RS, resources, Synchronization Signal, SS, blocks, and Physical Broadcast Channel, PBCH, blocks, determine one set from a plurality of sets of Physical Random Access Channel, PRACH, preambles and RACH occasions for the selected downlink reference signal according to an association configured between the downlink reference signals and PRACH resources, and use the determined set of PRACH preamble and RACH occasion to perform a PRACH transmission to the cellular station via the wireless transceiver, characterized in that the association configured between the downlink reference signals and the PRACH resources associates one CSI-RS resource, SS block, or PBCH block to one set of PRACH resources, or associates multiple CSI-RS resources, SS blocks, or PBCH blocks to one set of PRACH resources, wherein, when the association configured between the downlink reference signals and the PRACH resources associates multiple CSI-RS resources, SS blocks, or PBCH blocks to one set of PRACH resources, the controller is further configured to transmit an uplink transmission to the cellular station via the wireless transceiver for identifying which one of the multiple CSI-RS resources, SS blocks, or PBCH blocks is associated with the candidate beam.