a method of managing ta functionality for a communication device of a wireless communication system which supports carrier aggregation that multiple component carriers are aggregated to support wider transmission bandwidth is disclosed . the method comprises receiving a rrc message indicating a usage of a timing advance command for each of a plurality of component carriers configured to the communication device , from a cell in a network of the wireless communication system , when the timing advance command has been received from the cell for each of the plurality of component carriers , applying the timing advance functionality corresponding to each of the plurality of component carriers , for updating a timing advance value for each of the plurality of component carriers , and when updating the timing advance value for each of the plurality of component carriers , starting or restarting a time alignment timer for each of the plurality of component carriers .