A method performed by a base station in a wireless communication system, the method comprising: transmitting, to a terminal, a message for configuring a data radio bearer, DRB, the message including first information configuring a transmission when two radio link control, RLC, entities are associated with a protocol data convergence protocol, PDCP, entity for the DRB, wherein the message further includes second information associated with a primary RLC entity of the two RLC entities and third information on a threshold associated with an amount of data, and wherein the two RLC entities configured by the first information belong to different cell groups; and receiving, from the terminal, data packets based on an amount of the data packets and the threshold, the data packets including PDCP protocol data units, PDUs, wherein, in case that the threshold is set to infinity based on the third information, the data packets are transmitted via the primary RLC entity of the terminal.