A method performed by a terminal (2c-40) in a wireless communication system, the method comprising: receiving (2j-05), from a base station (2c-25), a radio resource control, RRC, message configuring a first logical channel and at least one serving cell allowed for a second logical channel associated with a carrier aggregation, CA, based packet duplication; mapping (2j-10) the second logical channel to a second serving cell of the at least one serving cell based on the RRC message; receiving (2j-10), from the base station (2c-25), information for activating the CA based packet duplication; transmitting (2j-30), to the base station (2c-25) via a first serving cell, a first packet data convergence protocol, PDCP, protocol data unit, PDU, associated with (2j-20) the first logical channel; and transmitting (2j-30), to the base station (2c-25) via the second serving cell, a second PDCP PDU associated with (2j-20) the second logical channel based on the information, wherein the first serving cell and the second serving cell are different, wherein the second PDCP PDU is a duplicate (2j-20) of the first PDCP PDU, and the CA based packet duplication is performed at a PDCP layer based on the information, wherein the first PDCP PDU associated with the first logical channel is transferred to a medium access control, MAC, entity (2j-15), and the second PDCP PDU associated with the second logical channel is transferred to the MAC entity, wherein data amount for a first logical channel group associated with the first logical channel and data amount for a second logical channel group associated with the second logical channel are transmitted (2j-25) via a buffer status report, BSR, to the base station (2c-25), and wherein the first PDCP PDU and the second PDCP PDU are transmitted (2j-30) through resources allocated based on the BSR. receiving (2j-05), from a base station (2c-25), a radio resource control, RRC, message configuring a first logical channel and at least one serving cell allowed for a second logical channel associated with a carrier aggregation, CA, based packet duplication; mapping (2j-10) the second logical channel to a second serving cell of the at least one serving cell based on the RRC message; receiving (2j-10), from the base station (2c-25), information for activating the CA based packet duplication; transmitting (2j-30), to the base station (2c-25) via a first serving cell, a first packet data convergence protocol, PDCP, protocol data unit, PDU, associated with (2j-20) the first logical channel; and transmitting (2j-30), to the base station (2c-25) via the second serving cell, a second PDCP PDU associated with (2j-20) the second logical channel based on the information, wherein the first serving cell and the second serving cell are different, wherein the second PDCP PDU is a duplicate (2j-20) of the first PDCP PDU, and the CA based packet duplication is performed at a PDCP layer based on the information, wherein the first PDCP PDU associated with the first logical channel is transferred to a medium access control, MAC, entity (2j-15), and the second PDCP PDU associated with the second logical channel is transferred to the MAC entity, wherein data amount for a first logical channel group associated with the first logical channel and data amount for a second logical channel group associated with the second logical channel are transmitted (2j-25) via a buffer status report, BSR, to the base station (2c-25), and wherein the first PDCP PDU and the second PDCP PDU are transmitted (2j-30) through resources allocated based on the BSR. <EOS>