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PAPR Reduction for Hybrid ACO-OFDM Aided IM/DD Optical Wireless Vehicular Communications

Hybrid asymmetrically clipped optical orthogonal frequency division multiplexing (HACO-OFDM) improves the spectral efficiency compared to asymmetrically clipped optical OFDM (ACO-OFDM) and pulse-amplitude-modulated discrete multitone (PAM-DMT) modulation, while retaining the advantage of high power efficiency. HACO-OFDM has found favor in numerous applications, but its peak-to-average-power ratio (PAPR) has remained a concern in optical wireless communications, since the family of existing PAPR reduction methods cannot be directly invoked for the superimposed HACO-OFDM signals. Hence, we analyze the characteristics of HACO-OFDM signals and develop a specific PAPR reduction technique relying on tone injection. Our numerical results show that the proposed method achieves significantly improved PAPR statistics compared to the conventional methods, leading to a significant bit error ratio (BER) reduction.