Using multiple antennas in the transmitter and/or in the receiver and exploiting all available knowledge about the channel in both the receiver and transmitter, the link capacity can be increased or the transmit power can be decreased. CDMA signals in frequency-selective channels can be preprocessed in the transmitter and postprocessed in the receiver with FIR filters to maximize the SNR at the receiver. The generalized selection combining (GSC) multiple input -multiple output (MIMO) eigen-precoder optimizes the SNR for reduced complexity receivers and transmitters. The capacity gains for different antenna configurations and frequency-selective channels are given.