In this study, we compare the single-carrier (SC) waveform adopted in IEEE 802.11ad and unique word discrete Fourier transform spread orthogonal frequency division multiplexing (UW DFT-s-OFDM) waveform. We provide equivalent representations of up-sampling and down-sampling operations of the SC waveform by using discrete Fourier transform (DFT) and inverse DFT to enable explicit comparison of these two similar waveforms. By using this representation, we discuss why the IEEE 802.11ad SC waveform can cause suboptimal performance in multipath channel and discuss how to improve it with UW DFT-s-OFDM. With comprehensive link-level simulations, we show that replacing the 802.11ad SC waveform with UW DFT-spread OFDM can result in 1 dB gain in peak throughput without affecting the IEEE 802.11ad packet structure. We also evaluate the cross links where the transmitter is UW-DFT-s-OFDM and the receiver is traditional SC-FDE or vice versa. We demonstrate that UW DFT-s-OFDM receiver can decode an IEEE 802.11ad SC waveform with a slight SNR loss while IEEE 802.11ad SC receiver can decode a UW DFT-spread OFDM waveform with an interference floor.
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