A network entity and an operating method thereof in a communication system are provided. The method includes establishing a first connection with a user equipment (UE) using a first access technology; receiving, from the UE, via the first connection, capability information on communication with a second cell using a second access technology different from the first access technology; transmitting a first signal to the UE via the first connection; and transmitting, to the UE, via the first connection, configuration information related to the second cell for establishing a second connection between the UE and the second cell. The first cell and the second cell are simultaneously active for the UE.