Low Complexity Transmit Diversity Scheme for SCFDE Transmissions Over Time-Selective Channels

In this paper, a low complexity transmit diversity scheme for single carrier-frequency domain equalization (SCFDE) is proposed, which is robust in high time-selective channels, (i.e. in high mobility environments), when the channel cannot be assumed constant over two consecutive processed symbols. The proposed scheme is equivalent to space-frequency block code (SFBC) for orthogonal frequency division multiplexing (OFDM) systems. However, the extension of SFBC to SCFDE systems is not straightforward since in SCFDE systems there is no direct access to subcarriers at the transmitter. The proposed scheme outperforms SCFDE-space-time block code (STBC) over fast fading channels also in high frequency selective channels, with a slight decrease in the overall complexity (in terms of complex multiplications).