Enhancing PAPR performance in optical-waveform for beyond 5G based VLC applications

Abstract

Sixth-generation (6G) optical wireless links require high spectral efficiency at low energy cost, but the high peak-to-average power ratio (PAPR) of direct-current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) forces large LED back-off, causes nonlinear distortion and clipping noise, and lowers electrical-to-optical conversion efficiency. This paper proposes an adaptive tone-reservation and bias-optimization (ATR-BO) scheme for 6G optical DCO-OFDM links. A small set of subcarriers, 8 % of the positive-frequency bins, is reserved for peak cancellation, and a single constrained peak-minimization problem yields both the cancellation coefficients and the minimum feasible optical bias. Because the reserved tones carry no data, no side information is needed at the receiver. Monte-Carlo simulations with 64–512 subcarriers, 16-QAM, four-times oversampling, a nonlinear Rapp LED model, and 10 ⁴ frames show a PAPR reduction of 3.4–4.8 dB at the 10 ⁻³ CCDF level and an SNR gain of about 2 dB at the 10 ⁻² BER level, while the in-band spectrum is preserved. The method is more computationally demanding than conventional DCO-OFDM and selective mapping, and the study is simulation-based; complexity, limitations, and future work are, therefore, also discussed in detail.