On the comparison between OFDM and single carrier modulation with a DFE using a frequency-domain feedforward filter

TLDR

Most comparisons between single‑carrier and multicarrier modulations assume frequency‑domain linear equalization of the channel. The study proposes a frequency‑domain decision‑feedback equalizer for single‑carrier modulation that adopts a block‑transmission format similar to OFDM with a cyclic prefix. The FD‑DFE is a nonadaptive DFE with a frequency‑domain feedforward filter and time‑domain feedback, and its design incorporates a reduced‑complexity technique that brings its computational load close to that of OFDM. Simulations and analytical derivations show that the FD‑DFE attains capacity and coded‑frame‑error‑rate performance nearly identical to OFDM, with comparable computational complexity after the reduced‑complexity design.

Abstract

Most comparisons between single carrier and multicarrier modulations assume frequency-domain linear equalization of the channel. We propose a new frequency-domain decision feedback equalizer (FD-DFE) for single carrier modulation, which makes use of a data block transmission format similar to that of the orthogonal frequency-division multiplexing with cyclic prefix (OFDM). The scheme is a nonadaptive DFE where the feedforward part is implemented in the frequency domain, while feedback signal is generated by time-domain filtering. Through simulations in a HIPERLAN-2 scenario, we show that FD-DFE yields a capacity very close to that of OFDM. This result is also confirmed by analytical derivations for a particular case. Furthermore, when no channel loading is considered, FD-DFE performs closely to OFDM for the same averaged frame error rate in a coded transmission. Design methods of the FD-DFE are investigated and a reduced complexity technique is developed, with the result that FD-DFE and OFDM have a similar computational complexity in signal processing.