الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
In the last few years, Visible Light Communication (VLC) has shown significant growth, primarily due to the development and popularity of Light-Emitting Diodes (LEDs). Moreover, it is green, low-cost, and has broad license-free bandwidth. Accordingly, dimming control is a critical technique in VLC to handle the lighting and energy consumption constraints. There are two techniques for applying dimming to LEDs: analog dimming and digital dimming. Analog dimming is the most popular technique because it is simple to implement. However, its main disadvantage is the inaccurate dimming level. The alternative technique is the digital dimming control, which determines the required dimming level significantly and accurately. On the other hand, the Optical Orthogonal Frequency Modulation (O-OFDM) technique has achieved a high bit rate. In O-OFDM, signals are transmitted parallel on a few subcarriers at different frequencies. In the VLC system, the Enhanced Asymmetrically Clipped DC Biased Optical OFDM (EADO-OFDM) is efficient and has adequate power and spectrum efficiency. Usually, Quadrature Amplitude Modulation (QAM) modulates each subcarrier. In this thesis, the Adaptive Digital Dimming Optical - OFDM (ADDO-OFDM) is proposed to combine the EADO-OFDM and Negative EADO-OFDM (NEADO-OFDM) based on the Pulse Width Modulation (PWM). Thus, the desired illumination is achieved by adjusting the duty cycle of PWM. Moreover, the EADO-OFDM scheme ensures that the data stream stays stable during dimming level adjustment.