A carrier sense multiple access method capable of improving throughput in a wireless network is disclosed. This method is implemented in a wireless network—for example, a wireless LAN (100)—having an AP (110) that is equipped with a multi-beam antenna (111) that forms a directional beam and that is capable of SDMA, and a STA (120, 130, 140) that communicate with the AP (110). With this method, the AP (110) allots the STA (120 to 140) to a beam group defined by a coverage area of the directional beam, according to the location of the STA (120 to 140). Then, the allocated STA (120 to 140) is assigned a signature signal for group identification, the signature signal being unique to the group.