A wireless broadband communications system that provides higher performance and increased spectral efficiency in point-to-point and point-to-multipoint applications. The wireless communications system includes a plurality of transceivers and a plurality of transmit and receive antennas. The system can be configured as a 1:n SIMO system that transmits and receives signals over a single channel of information flow, or an n:n MIMO system that transmits and receives signals over multiple channels of information flow, based upon channel state information and average vector error measurement values corresponding to the respective channels of information flow, which are determined by the system via an adaptive modulation technique.