SC (Single-Carrier) modulations are known to be suitable for high data rate transmission over severely time-dispersive channels such as the ones inherent to wireless systems. When combined with an appropriate CP (Cyclic Prefix), they present an efficient alternative to MC (Multi-Carrier) modulations such as OFDM (Orthogonal Frequency Division Multiplexing), with similar overall complexity. In this paper we study the theoretical performance of SC-FDE schemes (SC with Frequency-Domain Equalization) employing iterative receivers based on the IB-DFE (Iterative Block Decision Feedback Equalization). We present a simple, yet accurate analytical model for obtaining the corresponding BER (Bit Error Rate) performance.