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).
