Unique Word DFT-Spread-OFDM for Fast Time-Varying Channels

Unique Word Discrete Fourier Transform -spread - Orthogonal Frequency Division Multiplexing (UW DFT-s-OFDM) waveform replaces the Cyclic Prefix (CP) with a known sequence which is contained in the symbol itself rather than being appended to it. In this paper, we propose a new UW DFT-s-OFDM design which aims at exploiting such known sequence at the tail of the signal for tracking the variations of the radio channels on a symbol basis, thus overcoming the limited flexibility of DFT-s-OFDM waveforms in multiplexing reference sequences and data. Further, we also present a criterion for efficiently selecting the reference sequences to be adopted by users experiencing fast time-varying channel conditions. Initial simulation results show the capability of the proposed design of improving the link performance of high speed users, even without additional overhead.