Pragmatic frequency domain equalization for robust waveforms

Frequency domain equalization (FDE) has been proposed as a means of achieving the low-complexity equalization characteristic of orthogonal frequency-division modulation (OFDM) in broadband single-carrier systems. FDE studies to-date have focused on either uncoded systems or those employing relatively weak codes. This paper investigates the application of FDE to a waveform incorporating a strong modern code and robust constant envelope modulation. It is shown that the effect of noise enhancement due to nulls in the modulation spectrum is manifestly different for uncoded/weakly coded systems and strongly coded systems. For the former case, a novel FDE algorithm is developed that outperforms existing minimum mean-squared error techniques at high signal-to-noise ratios with comparable complexity. For the latter case, a family of iterative FDE algorithms is derived and studied via simulation.