Thus, implementing a PAPR reduction technique will help minimise the clipping noise and nonlinear distortion. Various solutions for PAPR reduction have been proposed in the literature. These include signal clipping methods in [5; 9], and the classical selected mapping (SLM) algorithm in [5; 9; 10]. Other methods based on the SLM scheme are reported in [11; 12]. The tone injection (TI) scheme is another PAPR reduction method studied in [9], and the tone reservation (TR) technique in [13]. Pilot-assisted (PA) technique was proposed in [5], and it is considered an effective solution for PAPR reduction in optical OFDM-based systems. The PA approach is applied in this work to reduce the high PAPR peaks of the transmitted waveform in PA DCO-OFDM [5]. The PA scheme rotates the phase of the transmitted OFDM data frame using a pilot sequence that is randomly generated to avoid adding the subcarriers coherently as much as possible. The used pilot sequence phase is selected based on the SLM algorithm and recovered at the receiver side by maximum likelihood (ML) algorithm [14].  
The PAPR reduction capabilities of PA technique is studied through simulation in [5], then compared to most widely used PAPR reduction techniques of clipping and classical SLM and the PAPR reduction impact on the system's bit error rate (BER) performance is investigated. In [6], the PA technique is implemented to reduce the peak values of the pulse-amplitude modulated discrete multitone (PAM-DMT)-based VLC system and the system's error performance is experimentally investigated using a blue LED. In [15], the analytical framework of the PAPR distribution of a PA DCO-OFDM and the theoretical analysis of the required DC bias to convert the bipolar PA DCO-OFDM signal to unipolar are presented. In addition, the derivation of the PAPR distribution of PA asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) signal is obtained and the average optical power reduction gain of the PA optical OFDM is investigated. In contrast, this work presents an analytical study of the impact of reducing the high PAPR values on signal clipping that leads to the noise/distortion of the time-domain waveform of DCO-OFDM-based VLC system.  
In this work, the DCO-OFDM modulation technique with the PAPR reduction is considered (PA DCO-OFDM) and the effect of double-sided clipping on its time-domain waveform is investigated. The attenuation factor and the variance of the clipping noise at the received waveform are determined in closed-form, which are included in the derivation of the signal-to-noise ratio (SNR) of the system. The bit error rate (BER) performance of the proposed PA DCO-OFDM system is analytically investigated at three different clipping levels as well as without any clipping. The analytical BER performance is verified through simulation and then compared to that of the conventional DCO-OFDM without a PAPR reduction at the selected clipping levels. Specific contributions of this manuscript are as follows:  
* The analytical investigation of a PAPR reduction in PA DCO-OFDM-based VLC system using the PA technique in the presence of clipping noise.
* The PA technique is applied to reduce clipping/nonlinear distortion and improve the error performance of the system.
* The BER performance of the PA DCO-OFDM is analytically investigated at different clipping levels and compared to the performance of conventional DCO-OFDM without PAPR reduction.
* The analytical comparison is verified through simulation at the selected clipping levels for the compared systems.  
The PA DCO-OFDM-based VLC system has achieved a better BER performance compared to that of conventional DCO-OFDM without PAPR reduction.  
The rest of this manuscript is organised as follows: The VLC system is presented in Section 2, while the PAPR reduction procedure is presented in Section 3. The PA DCO-OFDM clipping noise analysis is described in Section 4, and the results and discussions are in Section 5. The paper is concluded in Section 6.