A method for processing a data unit by a Packet Data Convergence Protocol (PDCP) entity of a user equipment includes configuring three or more Radio Link Control (RLC) entities with the PDCP entity; activating a first duplication mode for first and second RLC entities among the three or more RLC entities; providing the data unit to the first and second RLC entities by duplicating the data unit; receiving a duplication mode change command from a network; changing the first duplication mode to a second duplication mode for the first RLC entity and a third RLC entity; and providing the data unit to the first and third RLC entities by duplicating the data unit, wherein the first and second RLC entities is configured with a first Media Access Control (MAC) entity, and wherein the third RLC entity is configured with a second MAC entity.