This book aims to give an overview of recent developments in indoor near-infrared optical wireless communication technologies and systems, including basic theories, operating fundamentals, system architectures, modelling, experimental demonstrations, advanced techniques, and most recently, the research efforts towards integrations. Both line-of-sight and diffusive-signals-based options will be reviewed, to provide readers a complete picture about this rapidly developing area, which targets the provision of high-speed wireless connectivity to end- users in indoor environments, such as offices, homes and shopping centres, to satisfy the growing high-speed communication requirement.