Disclosed is a method for mapping a subscriber to a mobile network operator in a fifth-generation New Radio (5G NR) cellular telecommunication radio access network (RAN). The method is performed by a Radio Unit (RU) device operated by a first network operator and includes: transmitting system information including first information indicating network slices and second information indicating Physical Random Access Channel (PRACH) occasions mapped to the network slices, receiving a preamble of a Random Access Channel (RACH) during one of the PRACH occasions indicated by the second information, determining a second network operator based on the one of the PRACH occasions during which the preamble of the RACH is received, and transmitting the preamble of the RACH to a Distributed Unit (DU) device that is operated by the second network operator determined based on the one of the PRACH occasions during which the preamble of the RACH is received.