Partial Scrambling Overlapped Selected Mapping PAPR Reduction for OFDM/OQAM Systems

Tomoya KAGEYAMA  Osamu MUTA  

IEICE TRANSACTIONS on Communications   Vol.E104-B   No.3   pp.338-347
Publication Date: 2021/03/01
Publicized: 2020/09/24
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2020EBP3042
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
OFDM/OQAM,  peak-to-average power ratio (PAPR),  selected mapping (SLM),  self-synchronized scrambler,  

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Offset quadrature amplitude modulation based orthogonal frequency division multiplexing (OFDM/OQAM) is a promising multi-carrier modulation technique to achieve a low-sidelobe spectrum while maintaining orthogonality among subcarriers. However, a major shortcoming of OFDM/OQAM systems is the high peak-to-average power ratio (PAPR) of the transmit signal. To resolve the high-PAPR issue of traditional OFDM, a self-synchronized-scrambler-based selected-mapping has been investigated, where the transmit sequence is scrambled to reduce PAPR. In this method, the receiver must use a descrambler to recover the original data. However, the descrambling process leads to error propagation, which degrades the bit error rate (BER). As described herein, a partial scrambling overlapped selected mapping (PS-OSLM) scheme is proposed for PAPR reduction of OFDM/OQAM signals, where candidate sequences are generated using partial scrambling of original data. The best candidate, the one that minimizes the peak amplitude within multiple OFDM/OQAM symbols, is selected. In the proposed method, an overlap search algorithm for SLM is applied to reduce the PAPR of OFDM/OQAM signals. Numerical results demonstrate that our PS-OSLM proposal achieves better BER than full-scrambling overlapped SLM (FS-OSLM) in OFDM/OQAM systems while maintaining almost equivalent PAPR reduction capability as FS-OSLM and better PAPR than SLM without overlap search. Additionally, we derive a theoretical lower bound expression for OFDM/OQAM with PS-OSLM, and clarify the effectiveness of the proposed scheme.