A method of decoding a control channel in a wireless communication system is provided. In the method, a terminal calculates the number of sub-bursts to be used during a next decoding and positions of the sub-bursts, based on a signal-to-noise ratio of at least one of a first burst or a second burst. Then, the terminal compares the calculated number of sub-bursts with a reference value. When the calculated number of sub-bursts is greater than the reference value, the terminal does not receive more bursts or sub-bursts and instead enters into a sleep state. When the calculated number of sub-bursts is smaller than or equal to the reference value, the terminal receives and decodes only sub-bursts at the calculated positions.