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Linear space-time precoding for OFDM based on channel state information

We develop a new linear space-time precoding scheme for OFDM systems based on channel state information at the transmitter. The filter is derived for frequency-selective MlSO as well as for SISO channels using a minimum mean square error criterion with a constraint on transmit power. The guard interval of the resulting transmitted signal is no longer cyclic extension. Drawbacks of OFDM systems such as severe performance degradation for long channel delays exceeding the guard interval and vulnerability to possible nulls of the channel frequency response are addressed. Unlike existing equalizer variants at the receiver, our proposal combats these drawbacks by introducing computational complexity only at the transmitter while the receiver is kept simple as it is an advantage of OFDM systems against single carrier systems. Performance improvement has been confirmed by computer simulations.