Abstract: A base station (1) in a radio communication system is provided with an antenna array 2, 3 for communication with a plurality of mobile stations (4, 5). The transmissions of the base station (1) are optimised by adjusting the phase between the signals transmitted by each antenna (2, 3) so that the product of the propagation channel estimates is maximised. The invention has particular application to CDMA-TDD modes of operation where it has been shown to perform favourably in comparison with known transmit diversity techniques. A further advantage is that it does not require added complexity in the channel estimation at each mobile station (4, 5).

Abstract: In a method for wireless data communication between a base station and a subscriber unit in a wireless communication system, groups of symbols of an input data stream are commutated to produce a plurality of commutated data streams. The plurality of commutated data streams are then transformed to produce a plurality of transformed data streams. Next, each transformed data stream is spread with a selected one of a plurality of spreading codes to produce a plurality of antenna signals. Finally, each of the plurality of antenna signals is transmitted using a selected one of a plurality of spaced apart antennas, wherein the plurality of spaced apart antennas are spaced apart to provide transmit diversity. In one embodiment, the transform is a space-time transform.