APT System For Visible Light Optical Communication Based On Beidou Geography Position Information

The visible light communication(VLC) is a kind of wireless communication technologies which modulates baseband signal on the visible light emitted by LED and transfers the signals in atmosphere channels. It has many merits, such as anti-electromagnetic interference, safety, lightness in equipments, low cost, short time to construct, good flexibility, pure transport protocols. Not only can it be used independently, but also it can be combined with modern ordinary communication technologies as a useful complement. Though the advantages of visible light are clear such as smaller divergence angle and wide direction, it's difficult to establish visible light communication link and maintain communication link between terminals when the VLC is used for outdoor. Therefore, capturing the beacon light before the visible light communication link established and tracking of the beacon light continuously after targeting are important. And the technology which completes perfect alignment between two communication equipments is called APT. It's short as Acquisition, Pointing and Tracking.This thesis designs an APT scheme with the visible light communication based on Beidou geography position information, which is able to catch the beacon light quickly and improve the efficiency of communication. Specifically, the main achievements of this research are as follows: Firstly, it designs an APT system for visible light communication outside based on Beidou geography position information. Secondly, it carries on the detailed design of the capture and track algorithm based on Beidou geography position information. Especially, it calculates the transfer method from the original Beidou geography position to the antenna coordinate, and discusses the influence on azimuth angle and elevation angle under the antenna coordinate introduced by the original position error of Beidou geography position information. After analysis and calculates of the system numerically, the result shows that the proposed method based on Beidou geography position information can reach the precision of tracking, then completes the whole control algorithm of visible light communication based on Beidou geography position information; Thirdly, an additional scheme is proposed to minimize the dependency on Beidou or other system. A CCD is used as the receiver antenna of the communication subsystem, and it is also used as a signal acquisition device of the APT subsystem, so that it is able to complete a continuous tracking of the beacon light; Lastly, it completes the outdoor experiment of optical communication system which verifies the feasibility of the algorithm of APT scheme based on Beidou geographical position information.The experimental results and some computational analysis show that it could capture the beacon light quickly and track target accurately. The system assures a further smooth communication when the APT subsystem works properly.