Abstract
In visible light communication systems, the intensity modulation/direct detection channel inherently restricts the transmitted signal to be unipolar (nonnegative only) and incoherent. Those restrictions limit the types of transceivers that can be used in visible light communication systems; indeed, the intensity modulation/direct detection transceivers can be readily utilized, whereas classic radio frequency methods (e.g., schemes such as pulse amplitude modulation, quadrature amplitude modulation and orthogonal frequency division multiplexing) require adjustments that reduce their conventional efficiency. A continuous effort has been made to adapt radio frequency transceiver techniques to visible light communication; however, up to date, the proposed solutions came at the expense of the energy efficiency of the systems. In turn, it severely affects the bit error rate performance of the system. In light of this, the topic of this thesis is to design energy efficient transmission schemes to expand the set of legacy radio frequency modulation methods that can be efficiently used in visible light communication systems. Thus, the first contribution of this dissertation is a unipolar transmission technique that allows conveying bipolar symbols through the intensity modulation/direct detection channel without severely consuming the amount of transmit power. The second contribution is proposing a new technique to simultaneously transmit the two parts of two-dimensional signals over the intensity modulation/direct detection channel. The schemes are proposed with the objective of minimizing the transmitted power and reducing the direct current component of two-dimensional transmit signals by relying on multi-waveform transmission techniques, and, in turn, providing a high-energy efficient transmission scheme for two-dimensional signals. The third contribution is a low complex multi-input multi-output system capable of transmitting unipolar two-dimensional signals. Finally, the error rate expressions of our proposed transceivers in this work are derived, and the performance gains of the proposed schemes are evaluated through Monte-Carlo simulations. The findings show that our schemes could enhance the energy efficiency of the existing transmission techniques in visible light communication systems.