Note the multiple-input multiple-output communication system that supports a user and the sub user is disclosed. The base station belonging to a multiple-input multiple-output communication system for grouping at least one primary user (primary user) and the at least one sub-user (secondary user) corresponding to the at least one primary user according to characteristics of service required by the user scheduler, the at least one main state data for the user (primary data), and performs superposition coding to generate a transmission data stream superposition coding (superposition coding) the sub-data (secondary data) for the at least one sub-user unit, and and a beamformer for beamforming for the transmission data streams. MIMO, Multiple Input Multiple Output, the main user, the sub user, superposition coding, beam, frequency, PPM