Developing Visible Light Communication Systems Based on OFDM Technique

Abstract

With the rapid growth of wireless data requirements and the exhaustion of radio frequency (RF) capacity, Optical Wireless Communication (OWC) has become a promising candidate to complement classical RF communication, especially for indoor short-range applications. Nevertheless, the quality of the system depends on the distribution and the type of system used. Single carrier modulation waveforms, such as On-Off Keying (OOK), Binary Phase Shift Keying (BPSK), and Pulse-Position Modulation (PPM), have been applied to OWC in a relatively straightforward manner, but they suffer from a low data rate as their modulation order (M) is only 2. Orthogonal Frequency Division Multiplexing (OFDM) is chosen for OWC due to its ability to maximize the reachable data rate. This thesis studies the Optical Orthogonal Frequency Division Multiplexing (O-OFDM) in different scenarios and modulation techniques.

Visible Light Communications (VLC) based on the OFDM technique plays an important role in the field of wireless communications. Researches in this field found techniques to improve the bit Error Rate (BER), data rate performance, and reduce the system complexity. This thesis proposes a system named Asymmetric Symmetric Subcarriers Enhanced Optical OFDM (ASSEO-OFDM) with three receiver approaches applied to VLC based on OFDM technique. An analytical description of the proposed system approaches is introduced in the thesis, each approach aims to develop the output performance than other approaches besides a comparative study with other existing systems. Also, the proposed system enhances the transmitted data rate by a factor of 1/8 compared to Asymmetrically Clipped Optical OFDM (ACO-OFDM) and FLIP-OFDM systems. Keeping the same transmitted data rate as the comparable techniques, simulation results show an enhancement of the Energy per Bit to Noise power spectral density ratio (Eb/No) for the proposed system by at least 0.65dB than Asymmetrically and Symmetrically Clipping Optical OFDM (ASCO-OFDM), by at least 2dB than Asymmetrically Clipped Optical OFDM (ACO-OFDM) and FLIP-OFDM, and by at least 0.9dB than DC-biased Optical OFDM (DCO-OFDM) system at Bit Error Rate (BER) of 10−4.