Patent ID: 7586893

Claim:
A radio communication system comprising: a base station equipped with a sector antenna, the base station configured to transmit to a mobile station in accordance with a transmission frame; and the mobile station equipped with an omnidirectional antenna, the mobile station configured to transmit to the base station in accordance with the transmission frame, wherein the transmission frame is divided into slots to perform multiple access, and each of the slots comprises: region 1 in which the base station transmits a directional busy tone through the sector antenna used for the mobile station in an uplink mode, and the mobile station does not transmit; region 2 in which the mobile station in a downlink mode transmits a reference signal through the omnidirectional antenna to the base station, and the base station does not transmit; region 3 in which the base station transmits a directional busy tone through the sector antenna used for the mobile station in the downlink mode, and the mobile station does not transmit; and region 4 in which the mobile station in the uplink mode transmits the reference signal through the omnidirectional antenna to the base station, and the base station does not transmit.