A method for a base station to receive an uplink transmission from a user equipment configured with multiple uplink component carriers in a wireless communications system. The method according to one embodiment includes transmitting, to the user equipment, Radio Resource Control (RRC) configuration information for a Sounding Reference Signal (SRS), the RRC configuration information including information for periodically receiving the SRS from the user equipment; transmitting, to the user equipment, Layer 2 (L2) control information indicating states of the plurality of uplink component carriers; and performing a procedure for periodically receiving the SRS from the user equipment on a corresponding uplink component carrier in use of the RRC configuration information. According to whether the corresponding uplink component carrier is in an available state or a non-available state at a time for receiving the SRS, the SRS or no SRS is received from the user equipment, respectively.