A method performed by a terminal, comprising: receiving, from a base station, a radio resource control, RRC, message including data radio bearer, DRB, configuration information for a packet duplication, wherein one or more DRBs are configured for the packet duplication based on the RRC message; receiving, from the base station, a medium access control, MAC, control element, CE, including bitmap information indicating whether to activate the packet duplication of at least one DRB among the one or more DRBs configured for the packet duplication; and determining whether to activate the packet duplication of the at least one DRB among the one or more DRBs configured for the packet duplication based on the DRB configuration information for the packet duplication included in the RRC message and the bitmap information included in the MAC CE, wherein the packet duplication of the at least one DRB among the one or more DRBs configured for the packet duplication is activated based on bits included in the bitmap information, and wherein the bits included in the bitmap are mapped to a sequence of an identifier of the one or more DRBs configured for the packet duplication based on the DRB configuration information, characterized in that the method comprises, if the MAC CE indicates a deactivation of the packet duplication for the at least one DRB among the one or more DRBs configured for the packet duplication, if a transmission mode of the at least one DRB is an RLC acknowledged mode, AM, and if the terminal receives a NACK for a radio link control, RLC, protocol data unit, PDU, or an MAC PDU stored in a buffer of the at least one DRB in which the deactivation of the packet duplication is indicated, the terminal transmits the RLC PDU or the MAC PDU. receiving, from a base station, a radio resource control, RRC, message including data radio bearer, DRB, configuration information for a packet duplication, wherein one or more DRBs are configured for the packet duplication based on the RRC message; receiving, from the base station, a medium access control, MAC, control element, CE, including bitmap information indicating whether to activate the packet duplication of at least one DRB among the one or more DRBs configured for the packet duplication; and determining whether to activate the packet duplication of the at least one DRB among the one or more DRBs configured for the packet duplication based on the DRB configuration information for the packet duplication included in the RRC message and the bitmap information included in the MAC CE, wherein the packet duplication of the at least one DRB among the one or more DRBs configured for the packet duplication is activated based on bits included in the bitmap information, and wherein the bits included in the bitmap are mapped to a sequence of an identifier of the one or more DRBs configured for the packet duplication based on the DRB configuration information, characterized in that the method comprises, if the MAC CE indicates a deactivation of the packet duplication for the at least one DRB among the one or more DRBs configured for the packet duplication, if a transmission mode of the at least one DRB is an RLC acknowledged mode, AM, and if the terminal receives a NACK for a radio link control, RLC, protocol data unit, PDU, or an MAC PDU stored in a buffer of the at least one DRB in which the deactivation of the packet duplication is indicated, the terminal transmits the RLC PDU or the MAC PDU. <EOS>