Method and device for activating secondary carrier in wireless communication system for using carrier aggregation technique

A method by a terminal, the method comprising:

• receiving a control message for activating a secondary cell from a base station in a first sub-frame;
• transmitting first channel status information (CSI) of the secondary cell in a second sub-frame;
• and
• transmitting sounding reference signal (SRS) for the secondary cell no earlier than the second sub-frame,
• wherein, if the first CSI of the secondary cell is invalid, the first CSI of the secondary cell is set to 0, and
• wherein if the first CSI of the secondary cell is valid, the valid first CSI of the secondary cell is selected from 1 to 15 based on actual measurement of the secondary cell.