A method performed by a terminal in a wireless communication system, the method comprising: receiving, from a base station, a radio resource control, RRC, message including configuration information including information associated with a packet duplication in carrier aggregation or dual connectivity and information on at least two logical channels; duplicating uplink packets in case that the packet duplication is activated; transmitting, to the base station, the duplicated uplink packets on a first logical channel and a second logical channel based on the information on the at least two logical channels, the first logical channel and the second logical channel being included in the at least two logical channels; receiving, from the base station, a first downlink packet on the first logical channel; and receiving, from the base station, a second downlink packet on the second logical channel, wherein the first logical channel corresponds to a first radio link control, RLC, entity and the second logical channel corresponds to a second RLC entity; wherein the first downlink packet is different from the second downlink packet, wherein a pre-processing procedure is performed for the uplink packets before receiving an uplink grant including resource allocation information, wherein RLC sequences associated with the uplink packets are allocated to the uplink packets after receiving the uplink grant, and wherein the pre-processing procedure includes a procedure of header compression, integrity, and ciphering performed by a packet data convergence protocol, PDCP, entity of the terminal and a procedure for generating a PDCP header, an RLC header, and a medium access control, MAC, header. receiving, from a base station, a radio resource control, RRC, message including configuration information including information associated with a packet duplication in carrier aggregation or dual connectivity and information on at least two logical channels; duplicating uplink packets in case that the packet duplication is activated; transmitting, to the base station, the duplicated uplink packets on a first logical channel and a second logical channel based on the information on the at least two logical channels, the first logical channel and the second logical channel being included in the at least two logical channels; receiving, from the base station, a first downlink packet on the first logical channel; and receiving, from the base station, a second downlink packet on the second logical channel, wherein the first logical channel corresponds to a first radio link control, RLC, entity and the second logical channel corresponds to a second RLC entity; wherein the first downlink packet is different from the second downlink packet, wherein a pre-processing procedure is performed for the uplink packets before receiving an uplink grant including resource allocation information, wherein RLC sequences associated with the uplink packets are allocated to the uplink packets after receiving the uplink grant, and wherein the pre-processing procedure includes a procedure of header compression, integrity, and ciphering performed by a packet data convergence protocol, PDCP, entity of the terminal and a procedure for generating a PDCP header, an RLC header, and a medium access control, MAC, header.