ocated in the extended symbol edges by raised-cosine window coefficients is a widely used realization as chosen by windowed OFDM and weighted overlap-and-add OFDM waveforms. This 346 Chapter 3 Af = 1/T Af=alT (a<1) ATAF<1 F = alT ATAF = 1 x(t) = s(n)*h(t-nT) x(t) = s(n)*h(t-ndT,) Nyquist ISI criterion Faster-than-Nyquist ISI criterion Time-frequency sampling Faster-than-Nyquist sampling 1 W fs Frequency Nyquist sampling Frequency Channel Interleaver Modulator encoder mapper FTN transmitter Pulse sampler shaper Channel Equalizer demapper interleaver decoder Matched Whitening filter sampler filter FTN receiver Figure 3.26 Illustration of FTN concept and transmitter and receiver architecture [44]. technique generally has little or no effect on PAPR increase and has lower complexity com- pared to that of filtering techniques. Nevertheless, the detection performance might be degraded because of ISI caused by symbol extension. The linear processing of input data prior to IFFT is usually known as precoding, and may be helpful to improve OOB emissions and PAPR reduction. One example is DFT-S-OFDM New Radio Access Physical Layer Aspects (Part 1) 347 Windowed CP-OFDM Windowed GFDM Windowed DFT-S-OFDM Zero-tail DFT-S-OFDM QPSK single-carrier (SC) QPSK + hybrid PSK SC PAPR (dB) Figure 3.27 Comparison of PAPR performance of some prominent variants [47]. waveform that was adopted in LTE uplink transmission because of its low PAPR properties relative to conventional OFDM. Some variants of DFT-S-OFDM were proposed for NR such as zero-tail (ZT) DFT-S-OFDM by omitting the CP and letting the tail samples taper to zero. The DFT-S-OFDM-based waveforms, in contrast to filter-based waveforms, usu- ally make it easier to maintain PA linear operation with less deterioration from lowering OOB emissions. Moreover, an appropriate modification of modulation schemes, such as 2-BPSK can greatly assist such waveforms in achieving an extremely low PAPR. Note that in the absence of redundant intervals, ISI can still occur. Among DFT-based precod-