The present invention relates to a wireless communication system, and more particularly, to a method of uplink transmission, in which a user equipment transmits a signal in uplink in a wireless communication system. The present invention includes switching an uplink transmission mode used in transmitting the signal to a base station to either a first transmission mode or a second transmission mode, generating a plurality of signals to transmit to the base station via a plurality of component carriers (CCs), and transmitting a plurality of the signals to the base station according to the switched uplink transmission mode, wherein the first transmission mode allows multi-carrier characteristics for the signal transmitted via a plurality of the component carriers and wherein the second transmission mode requests single carrier characteristics for the signals transmitted via a plurality of the component carriers.