Patent ID: 8767674

Claim:
A method for establishing or reestablishing a Radio Resource Control (RRC) connection to a network at a User Equipment (UE) in a mobile communication system using Carrier Aggregation (CA) in which communication is conducted on a plurality of Component Carriers (CCs), the method comprising: performing cell selection or cell reselection; selecting a first downlink CC according to a result of the cell selection or the cell reselection, wherein the first downlink CC is selected among an available CC set for the UE; selecting a first uplink CC linked to the first downlink CC, wherein the first uplink CC is selected among the available CC set for the UE; receiving system information on the first downlink CC from the network after performing the cell selection or the cell reselection, the system information including information about a second uplink CC and a second downlink CC; adding the second uplink CC and the second downlink CC to the available CC set for the UE; selecting a first CC set having the first uplink CC and the first downlink CC or a second CC set having the second uplink CC and the second downlink CC; and establishing or reestablishing an RRC connection to the network using the selected CC set.