  High peak-to-average power ratio (PAPR) is a critical problem in orthogonal
frequency-division multiplexing (OFDM). The fifth-generation New Radio (5G NR)
facilitates the utilization of multiple heterogeneous bandwidth parts (BWPs),
which complicates the PAPR problem even further and introduces inter-numerology
interference (INI) between the BWPs. This paper proposes two novel schemes to
reduce the PAPR of mixed-numerology OFDM signals. The first scheme is an
original enhanced iterative clipping-and-error-filtering (ICEF) approach that
cancels efficiently the INI along with PAPR reduction. This allows to achieve
efficient PAPR reduction while being compatible with well-known windowed
overlap-and-add (WOLA) processing. The second scheme is based on
fast-convolution (FC) processing, where PAPR reduction is embedded in the FC
filtering carried out using overlapping processing blocks. This allows one to
use any existing block-wise PAPR reduction method to reduce the composite
signals' PAPR with arbitrary BWP waveforms, and it is thus especially well
suited for processing mixed-numerology composite waveforms carrying multiple
BWPs with different OFDM numerologies. The performance of the proposed
algorithms is evaluated in the 5G NR context, and the essential performance
advantages are demonstrated and quantified.
