Method and apparatus of operating multiple time alignment timers in mobile communication system supporting carrier aggregation

A method performed by a terminal supporting carrier aggregation in a wireless communication system, the method comprising:

• receiving, from a base station, first timing advance (TA) information associated with a primary timing advance group (PTAG) which is a group of serving cells using same timing advance value for an uplink transmission and includes a primary cell;
• starting or restarting a first timing alignment timer (TAT) associated with the PTAG based on the first TA information;
• receiving, from the base station, second TA information associated with a secondary timing advance group (STAG) which is a group of serving cells using same timing advance value and does not include the primary cell;
• starting or restarting a second TAT associated with the STAG based on the second TA information;
• receiving downlink data on at least one serving cell in the STAG;
• identifying that a TAT is expired;
• in case that the expired TAT is the second TAT associated with the STAG, notifying a radio resource control (RRC) layer to release at least one physical uplink control channel (PUCCH) for serving cells belonging to the STAG;
• in case that the expired TAT is the first TAT associated with the PTAG, notifying the RRC layer to release at least one PUCCH for all serving cells belonging to the PTAG and the STAG;
• identifying whether the expired TAT is associated with a TAG which includes a serving cell on which hybrid automatic repeat request (HARQ) feedback is to be transmitted and supporting a PUCCH transmission;
• in case that the expired TAT is associated with the TAG including the serving cell, an instruction to generate HARQ positive or negative acknowledgement information for the downlink data is not delivered to a physical layer of the terminal;
• and
• in case that the expired TAT is not associated with the TAG including the serving cell, an instruction to generate the HARQ positive or negative acknowledgement information for the downlink data is delivered to the physical layer.