COMMUNICATIONS APPARATUS AND METHOD, COMPUTER PROGRAM, AND COMMUNICATION SYSTEM

PROBLEM TO BE SOLVED: To appropriately perform communication operation by applying space division multiple access, in which a radio resource on a spatial axis is shared by a plurality of users. SOLUTION: When high communication quality is high, if a frequency width is made narrow down to 20 MHz, a transmissible data amount can be reduced approximately by half, and a frame length can be extended doubled. If the frame length is too long, the frame length is shortened, by switching to a modulation method with much more states. Meanwhile, in low communication quality, the frame length is extended by switching to a modulation method with much less states. If the frame length is yet insufficient, the frame length is extended by switching to a narrow frequency width. COPYRIGHT: (C)2011,JPO&INPIT