A method for exchanging channel information between a transmitter and a receiver each including antennas. A request frame including a first preamble, second preamble, and channel information feedback request is transmitted to the receiver, wherein the first preamble is transmitted from one of the antennas of the transmitter, the second preamble is transmitted from each of the antennas, and the channel information feedback request is transmitted from the one of the antennas. The request frame is received at the receiver, and the channel information feedback request is detected by a decoding based on the first preamble. Channel information is estimated using the second preamble, and a notification frame including the estimated information is constructed and transmitted to the transmitter.