Studies On Optical Wireless Communication System Based On Turbo Code

Optical wireless communication (OWC) system bonds the advantage of fiber communication and radio communication, it springs up again along with the development of the progress of the semiconductor lasers and optoelectronic detectors. The main advantages of OWC system are that high bandwidth, large capacity, quick deployment, flexibility, low cost, license-free allocation, so it has widely promising application. However the OWC system's transmission medium is atmospheric channel, the atmospheric channel seriously impact the communication quality. In this dissertation, we focus on turbo coded OWC system in order to eliminate atmospheric channel disturb, several theoretical studies and systematic design have been carried out as the following:(1) The OWC system's developmental history and application classification are systematically summarized in brief, the technical advantage and disadvantage are analyzed, and the domestic and foreign researches status is introduced.(2) The main factors which influence the OWC system's signal transmission are presented. The theoretical models of atmospheric attenuation, atmospheric turbulence, systemic table swaying and background light noise are analyzed, the optical table swaying theoretical model is simulated particularly.(3) The Shannon channel coding theory is analyzed in detailed, the various channel coding projects in history are compared, atmospheric light channel capacity's model is established, and the model is simulated by Monte Carlo method.(4) Turbo code's coding structure and principle are analyzed particularly, the MAP decoding arithmetic of turbo coded OWC system based on OOK, BPSK, BPPM are deduced, and OWC system's performance based on different modulated models are compared.(5) The coding and decoding principle of a novel turbo code named as twofold turbo code are analyzed for the first time, twofold turbo code is applied to OWC system, the application of common and twofold turbo code to OWC system are compared.(6) The laser used in OWC system is selected, and the laser's driving circuit and power controlling circuit are designed, the transmitting and receiving optical antennas are compared and selected. (7) A set of OWC system are accomplished, and the OWC system are tested for a long time in indoor and outdoor.