ipped in the transmitter power amplifier, because of its limited dynamic range or nonlinearity. Higher output back-off is required to prevent BER degradation and intermodulation products spilling into adjacent channels. However, clipping of an OFDM signal has sim- ilar effect as impulse interference against which an OFDM system is inherently robust. Computer simulations show that for a coded OFDM system, clipping of 0.5% of the time results in a BER degradation of 0.2 dB. At 0.1% clipping, the degradation is less than 0.1 dB. 10 In tone reservation method, the transmitter and the receiver reserve a subset of tones or subcarriers for gener- ating PAPR reduction signals. Those reserved tones are not used for data transmission. New Radio Access Physical Layer Aspects (Part 1) 323 BPSK with -90degrees phase rotation QPSK with -90degrees phase rotation PAPR (dB) Figure 3.12 CDF of OFDM PAPR with BPSK/QPSK modulation and NFFT = 128 [30]. Fig. 3.12 shows the CDF of OFDM PAPR for BPSK and QPSK modulation assuming a 40 MHz channel bandwidth and NFFT = 128. We further applied 90 degrees phase rotation to the subcarriers in the upper 20 MHz of the channel and investigated the effect on the PAPR reduction [47]. It is shown that large PAPR values are less likely to occur with large FFT sizes as suggested earlier. The PAs have generally a nonlinear amplitude response, where the output power is saturated for large input signals. Most applications require operation in the linear region of the PA where the output power is a linear function of the input. The larger the linear operation region or alternatively the higher saturation point, the more expensive the PA. Therefore, it is imperative to reduce the PAPR of the OFDM signal before processing through the PA. The wider bandwidth of NR compared to LTE increases the PAPR of the transmitted signal and makes it harder to achieve the same power efficiency as an LTE frontend. Current esti- mates suggest that for a single PA supplying an average transmit power of 23 dBm at the antenna