OFDM schemes have important limitations such as the high envelope fluctuations of the transmitted signals and its sensibility to carrier frequency errors. When these limitations bear critical we should consider SCFDE schemes (Single-Carrier Frequency Domain Equalization), which allow much higher power efficiency due to the lower envelope fluctuations. This can be further improved if the conventional linear FDE is replaced by an iterative FDE such as an IB-DFE (Iterative Block Decision Feedback Equalizer).
In order to obtain good performance results, accurate channel estimates must be available at the receiver, especially if MIMO (Multiple Input, Multiple Output) and high-order modulations are to be used. 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.
In this paper we consider SC-IB-FDE systems in MIMO 2x2 broadband with high order modulations and channel estimation.