Frequency Domain Pre-Equalization With Precoding for Broadband SDMA Systems

Single carrier frequency domain equalization (SC-FDE) has been recently receiving much attention as an alternative to orthogonal frequency-division multiplexing (OFDM) to deal with the detrimental effects of multipath fading. In this paper, we consider transmit frequency domain pre-equalization (FD-PRE) in the downlink transmission of space-division multiple access (SDMA) systems, where the FD-PRE is combined with the Tomlinson-Harashima precoding (THP) technique at the base station so that the mobile station requires limited processing. We propose two FD-PRE MIMO schemes, with parallel and successive precoding, based on the minimum mean square error (MMSE) criterion. In contrast to the previous FD-PRE with THP design, where the THP is only for co-channel interference (CCI) pre-cancellation, the proposed parallel and successive precoders are designed by taking both inter-symbol interference (ISI) and CCI into account. Numerical results will demonstrate the significant performance improvement of our proposed schemes compared to the conventional FD-PRE MIMO schemes. We will also investigate the channel estimation errors and channel variation effects on the proposed systems. It will be shown that by applying channel prediction such detrimental effects can be greatly reduced.