A base station for use in a wireless network communicating with a plurality of subscriber stations. The base station transmits in a downlink channel to a first subscriber station using a plurality of transmit antennas. The base station transmits to the first subscriber station using either a transmit diversity scheme or a beamforming scheme according to the amount of correlation between the transmit antennas observed at the first subscriber station. The base station also transmits to the first subscriber station using a cyclic delay diversity scheme having either zero delay or non-zero delay according to the amount of antenna/channel correlation observed at the first subscriber station.