SC modulation (Single-Carrier) with FDE (Frequency-Domain Equalization) allows excellent performance in severely time-dispersive channels, provided that accurate channel estimates are available at the receiver. For this purpose, pilot symbols and/or training sequences are usually multiplexed with data symbols, which lead to spectral degradation. As an alternative, we can use implicit pilots (i.e., pilots superimposed to data).
In this paper we consider MIMO SC-FDE systems where the channel estimation is based on either multiplexed (explicit) or implicit pilots, for comparison purposes. An iterative receiver with joint equalization, turbo decoding and channel estimation was employed in order to optimize the results, and to reduce the high interference levels between data and pilots (for the implicit pilots). The main differences between the different schemes are discussed and the performance results show that the proposed techniques for channel estimation yield excellent results .