In a communications system which complies with LTE including a base station 2 which transmits data by using an OFDM (Orthogonal Frequency Division Multiplexing) method as a downlink access method, and a mobile terminal 3, in a case in which an uplink scheduling request signal SR is transmitted by using an S-RACH when an Ack/Nack signal is being transmitted by using an Ack/Nack exclusive channel, the transmission of the Ack/Nack signal is stopped while the uplink scheduling request signal SR is transmitted.

Methods, systems, and apparatuses are provided for a User Equipment (UE) in a wireless communication system receiving, from a network, a first signaling indicative of cell configuration of a cell, receiving, from the network, a second signaling indicative of switching a Special Cell (SpCell) of the UE to the cell or adding the cell as a serving cell, receiving, from the network, a third signaling indicative of a first time alignment information associated with the first Timing Advance Group (TAG), and in response to the second signaling: (1) switching the SpCell of the UE to the cell or adding the cell as the serving cell, (2) applying the first time alignment information on the first TAG, and (3) initiating a random access procedure on the cell when no time alignment information associated with the second TAG is in the third signaling.

Disclosed are a method, an apparatus, and a system for transmitting a signal using multiple carriers. In detail, provided are a wireless communication apparatus including a communication module; and a processor, wherein the processor obtains a common back-off counter for a carrier set on which data is to be transmitted, wherein the carrier set includes at least one component carrier, performs back-off of each of the component carriers using the obtained common back-off counter, and simultaneously transmits data through at least one component carrier in which the back-off is completed and a wireless communication method using the same.