The present invention relates to a wireless communication system. More specifically, the present invention relates to a method for reporting a channel state by a terminal to a serving base station in a wireless communication system, wherein extra channel state information is reported to enable the serving base station to estimate the channel state more accurately. When the base station estimates the channel state with the terminal, the channel state information received from the terminal, the extra channel state information, and traffic information of neighboring base stations are collectively considered to estimate the channel state with the terminal, thereby enabling estimation of the channel state with improved reliability and accuracy.