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Title Nonlinear Characteristics of DFT-Spread WR-OFDM System for Spectrum-efficient Communications
Authors Md. Najmul Hossain; Tetsuya Shimamura; Heung-Gyoon Ryu
Page pp.490-498
ISSN 2287-5255
Keywords WR-OFDM; DFT-spread; PAPR; OOB power reduction; Spectrum efficiency; Windowing; HPA nonlinearity
Abstract Since frequency resources are limited, and power saving is also a vital issue, a more spectrum-efficient and power-saving communications system design is the most important research goal. In this paper, we propose an improved, spectrally efficient new discrete Fourier transform (DFT)-Spread Windowing and Restructuring (WR)-Orthogonal Frequency Division Multiplexing (DFT-Spread WR-OFDM) communications system, in thought of various strengths of high-power amplifier (HPA) nonlinearity for a reasonably allowable peak-to-average power ratio (PAPR) and out-of-band (OOB) power emission reduction. Compensation for HPA nonlinearity becomes a difficult task when properly designing efficient multicarrier schemes and fifth generation (5G)- beyond 5G candidate waveforms for cellular wireless communications systems. In practical communications systems, spectral efficiency and power are highly affected by HPA nonlinearity features, and bit error rate (BER) performance also deteriorates. We implemented a time domain window named Tukey (tapered cosine) and localized subcarrier mapping, and the impact of HPA nonlinearity on BER performance and spectral characteristics is comprehensively analyzed.
Simulation results demonstrate that the proposed system reduces PAPR and OOB power emissions by 3.176 dB and -81 dB, respectively. Additionally, compared to conventional systems, the communication quality of the proposed scheme clearly demonstrates better performance even in HPA nonlinear environments.