ared to LTE, where CP-OFDM was already used in the downlink, the Single Carrier Frequency-Division Multiple Access (SC-FDMA) waveform was used in the uplink to reduce the PAPR and achieve higher output power capability from the UE power amplifier. In NR, it is mandatory for the UL to support both CP-OFDM and DFT-s-OFDM: Quadrature Phase Shift Keying (QPSK)-modulated DFT-s-OFDM offers a low PAPR (as does LTE SC-FDMA) but is restrained to single stream operation (cannot be used for Uplink Multiple Input Multiple Output (UL MIMO)) and has limitations in 12.2 Impact of New Physical Layer on RF Performance LTE Ref GFDM Ref UFMC Ref FBMC Ref fOFDM : Ref 2.570 2.575 2.580 2.585 2.590 2.595 2.600 2.605 2.610 2.615 2.620 2.625 2.630 Frequency [MHz] LTE : LTE DUT GFDM : LTE DUT UFMC : LTE DUT FBMC : LTE DUT fOFDM : LTE DUT 2.570 2.575 2.580 2.585 2.590 2.595 2.600 2.605 2.610 2.615 2.620 2.625 2.630 Frequency [MHz] Figure 12.1 Spectrum using with different filtering/windowing techniques at (top) PA input and (bottom) output. 12 5G RF Design Challenges NR Shaped PI/2 BPSK DFT-s-OFDM NR PI/2 BPSK DFT-s-OFDM NR QPSK DFT-s-OFDM LTE QPSK SC-FDMA NR QPSK DFT-s-OFDM NR QPSK CP-OFDM NR 64QAM CP-OFDM 0.001 0.001 Peak to average dB Peak to average dB Figure 12.2 PAPR for (left) single-carrier LTE QPSK VS. 5G DFT-S-OFDM and CP-OFDM waveforms, (right) 5G shaped and un-shaped Pi/2 BPSK vs 5G QPSK DFT-S-OFDM. possible RB allocations that must follow the rule NRB =2xx3xx5. Also, the PAPR increases with higher order modulations. CP-OFDM has an approximately 2.5 dB higher PAPR but is not subject to limitations in RB allocation, and thus it is used for multiple stream links. Although it has a higher PAPR, it does not vary for higher order modulations compared to QPSK (Figure 12.2 left), and thus it is more efficient than DFT-s-OFDM for higher order modulations. While CP-OFDM waveforms increase the PAPR and thus the linearity requirements for the UE power amplifier increases, NR also introduces lower PAPR UL modulation for DFT-s-OFDM wavefor