Patent ID: 8848674

Claim:
A user equipment (UE) performing an uplink synchronization in a wireless communication system, the UE comprising: a receiving unit configured for receiving a medium access control (MAC) protocol data unit (PDU) from a base station (BS); and a MAC processing unit configured for: identifying that the MAC PDU includes a MAC header and a MAC control element (CE); obtaining, from the MAC header, a subheader; obtaining, from the subheader, a logical channel identifier (LCID) indicating an index to identify whether the MAC CE is for timing advance command (TAC); obtaining, from the MAC CE, a TAC field with 6 bits indicating a timing alignment value (TAV) and a timing alignment group (TAG) index field with 2 bits identifying a TAG to control uplink timing adjustment identically with the TAV; identifying the TAG to which the TAV is applied based on the TAG index field; and controlling the uplink timing adjustment for at least one serving cell in the identified TAG.