Phase Rotation Approach with Mixed-Numerology Architecture for PAPR Reduction in 5G and Beyond

For a wide range of service requirements, the 5G-NR offers significant flexibility based on OFDM with numerous numerologies. However, OFDM is recognized to have a significant disadvantage due to a high PAPR. On the other hand, the PAPR reduction for mixed-numerology OFDM has received little attention compared to single-numerology OFDM, despite there being possible challenges and advantages such as computational complexity and new structure opportunity, respectively. In this paper, the phase rotation PAPR reduction approach on mixed-numerology OFDM is proposed for the first time. Unlike the single-numerology approach, the need for additional IFFT and side information overhead is eliminated, and the mixed-numerology transmitter structure is exploited to provide three novel approaches, namely proposed numerology-based (Proposed-NB), proposed symbol-based (Proposed-SB), and proposed location-based (Proposed-LB). Proposed-NB has the same PAPR performance with a lower complexity compared to the partial transmit sequence (PTS) method for single-numerology OFDM. Moreover, the new ability to use multiple phase factors for the same numerology symbols in the defined largest symbol length enhances the PAPR reduction performance further using Proposed-SB. While all symbols are jointly optimized in the Proposed-SB, Proposed-LB drives a sub-optimal solution developed by optimizing the selected symbols. Due where the presence of different symbols duration between numerologies and also consecutive symbols in the same numerology, PAPR reduction performance in Proposed-LB almost reaches the optimum Proposed-SB performances with a lower computational complexity compared to Proposed-SB. The conducted numerical results validate the superiority of the proposed methods for 5G and beyond compared to PTS and numerology scheduling methods.