Research On Non-Directional Transmission System Of Indoor Visible Optical Communication

LED get rapid development in just a few decades. With the development of LED technology, LED has been widely used for indoor and outdoor illumination. Based on the white LED, visible light communication (VLC) technology, can achieve low-cost lighting and communications at the same time.Applicable to a variety of access scenarios, with no electromagnetic interference, environmental protection.Because of these advantages, the visible light communication (VLC)technology has developed quickly in recent years. At present, the study of visible light communication is focused on how to improve the transmission rate, but the research for the application of visible light communication and indoor optical communication system hardware design and network architecture are relatively weak. Many studies remain in the simulation design and offline experiment stage, there is a certain distance to realize a practical visible light communication system.In the conventional visible light communication, transmitter and the receiver need to be strict alignment and it limits the flexibility of use.Considering the practicability, the dissertation describes the design and realization of the non-directional transmission system of visible light communication. The main work of this dissertation is as follows: The design of the optical receiver with large FOV (Field Of View). And the non-directional transmission of visible light communication can be realized. The experiment shows that this communication system can achieve the 60 °, short-distance non-directional communication.1. In this dissertation, indoor channel model of VLC system is firstly introduced, we analyze that the major pathway of the loss is from the free space loss. With the help of mathematics tools, we get the link design and power budget of the system. And lay the foundation for the overall design of the system.2. The modulation bandwidth of white LED is very narrow and seriously limits the signal transmission rate. Although the performance of the system can be optimized through the use of modulation techniques,equalization techniques are required to further increase the capacity of the system. In this dissertation,the equalization technique is studied, and the analog equalization technique is applied in the visible light communication and experimented.3. The optical receiver is an important part of the VLC system. And a Photodetector plays an important role in an optical receiver. The PD with high sensitivity and high gain can objectively enhance the transmission distance. And the visibility angle (FOV) is increased by optimizing the design of the optical concentrator, and can achieve the 60°,short-distance non-directional communication.