A new DC additionless optical OFDM design based on orthogonal conversion for visible light communication systems

Due to the developing technologies and the need for fast access to information, the radio frequency bands reserved for wireless mobile communication are rapidly filling up and approaching the upper limits of the RF band. Therefore, it will inevitably become too difficult or impossible to operate in higher frequency bands above the possible frequency bands to be adjusted for 5G systems. In this case, a new technology is needed. Visible Light Communication (VLC) systems, which is a communication system orthogonal to RF technology, can be preferred as an alternative. In visible light communication, light emitting diodes (Light Emitting Diode, LED) are preferred for data transfer and room lighting. The fully networked version of VLC, called Light Fidelity, LiFi, is considered a complementary solution for RF-based wireless connectivity (Wireless Fidelity, WiFi). Orthogonal Frequency Division Multiplexing (OFDM) is used to encode data in VLC. OFDM provides high data rates and is resistant to Intersymbol Interference (ISI). However, OFDM symbols are complex and bipolar. Therefore, OFDM symbols need to be converted to real and unipolar in order to be used for intensity modulation and direct detection (Intensity Modulation/Direct Detection, IM/DD). Some of the unipolar forms of OFDM are direct current (Direct Current, DC) biased optical OFDM (DCO-OFDM), asymmetrically clipped optical OFDM (ACO-OFDM), and non-DC biased optical OFDM (NDC-O-OFDM). In this master's thesis, in studies on improving the performance of MIMO and VLC-OFDM-based original transmission techniques, in order to further increase the performance of the NDC-O-OFDM system, a new DC biasless optical OFDM based on Lifting wavelet transform (LWT-NDC-O-OFDM) system is recommended. In this proposed system, MIMO technology is used and complex OFDM signals are divided into positive-negative and real-imaginary parts and the signals are transmitted over the MIMO-VLC channel. It has been seen that the proposed system gives more successful results compared to the existing systems in the literature.