# Optical-OFDM VLC System: Peak-to-Average Power Ratio Enhancement and Performance Evaluation
## 1 Introduction  
The proliferation of smartphones and the Internet of Things (IoT) has led to a paradigm shift in communication requirements, necessitating high-throughput and low-latency networks to facilitate real-time applications and seamless connectivity. Wireless Fidelity (WiFi) is becoming a common method of offering rapid internet and network connections in households and businesses. The well-known issue of spectrum crunch, arising from the shortage of usable natural frequency spectrum in wireless networks, necessitates solutions for developing next-generation communication systems. Based on the ITU's global forecast for mobile data traffic, mobile data usage is anticipated to increase by approximately 55% annually from 2020 to 2030. This growth is expected to reach 607 exabytes (EB) by 2025 and an astounding 5016 EB by 2030 [1]. As a result, it is critical to make optimum use of the spectrum in order to support the growing number of high-data-rate devices. Visible Light Communication (VLC) has emerged as a viable and promising solution to mitigate the limitations inherent in conventional wireless network technologies [2, 3]. VLC technology is widely used for precise positioning, the fast streaming of videos, data broadcasting indoors, and underwater transmission. It is also common in vehiclecommunication and electromagnetic interference-sensitive environments like aviation and hospitals, supporting music and audio signals with 3 GPP audio coders [4; 5; 6; 7]. VLC, in conjunction with intensive wavelength division multiplexing, is used in cutting-edge communication technologies such as 6G mobile communication systems [1]. VLC employs an intensity modulation and direct detection (IM/DD) scheme to transmit data at speeds that surpass the persistence of the human eye by modulating the intensity of Light-Emitting Diodes (LEDs) [8]. Compared to traditional Radio Frequency (RF) technology, VLC offers several advantages, such as data transfer with higher speeds, security enhancement, access to a broader, unregulated bandwidth, remarkable efficiency in terms of energy consumption, and comparatively cost-effective infrastructure [9]. One of the most prevalent applications of LED technology in VLC systems is its unique ability to serve both as a source of illumination and a means of high-speed data transmission [2]. This dual functionality presents two primary challenges: addressing the flickering effect and achieving effective dimming control. Furthermore, modern lighting devices now offer dimming capabilities, allowing for precise control of brightness levels. Given the potential for energy preservation, brightness control is a vital characteristic in the context of VLC. As a result, selecting proper modulation formats becomes critical in order to efficiently solve the difficulties of flicker reduction, dimming control, and providing reliable high-speed data connection [10]. In the realm of VLC, modulation techniques can be broadly organized into single-carrier modulation (SCM) and multicarrier modulation (MCM) techniques [4]. SCM techniques like analog pulse modulation types and on-off keying are employed to construct VLC systems, resulting in lower data rates. To mitigate this drawback, MCM techniques, such as O-OFDM, have been introduced [9; 11]. O-OFDM modulation offers a promising approach to enhancing the data transmission capacity of LEDs by effectively utilizing a wider range of light frequencies, enabling faster data communication. Consequently, various modified O-OFDM systems have been explored, considering factors such as spectral efficiency, power efficiency, computational complexity, BER, and LED nonlinearity [12]. The optical-OFDM depends on the DC bias, also known as the DCO-OFDM approach, which has the benefit of obtaining the maximum data rate in VLC systems. It achieves higher data rates at the cost of applying a DC bias to transform the output bipolar samples into unipolar samples. Nonetheless, this leads to ineffective power utilization and influences the system's BER performance [13].