Electronic Toll Collection (etc) System, Optical Communication Devices

The highway's fast development has greatly advanced the whole social economy of our country. But the automatic level of toll-collection on the highways remains comparatively underdevelopment by contrast with the construction of highways, which causes the situation of heavy traffic more and more serious, and that the driving speed on the highway has been greatly reduced.The electrical toll collection (ETC) system improves the traffic capacity and service level efficiently. On board unite (OBU) and road-side unite (RSU) are the main parts of ETC system. OBU and RSU can communicate with each other by wireless communication equipments, to toll without stop.Compared with radio frequency, optical communication has many advantages, including a huge bandwidth, high security and absence of interference, so the ETC system which based on optical wireless communication has stronger adaptability, lower cost and better performance.In this paper, the communication equipments used for optical ETC system are researched. The main assignments are: accomplished the design of transmitter, receiver, coder and decoder module, control system of OBU and RSU. The communication protocol and the main factors which would influence the communication are also discussed.The optical transmitter consists of an infrared LED cluster and its drive circuit. The optical receiver has a photodiode and an amplifier circuit. An optical filter on infrared band and an optical tube for gathering light are also used. Finally, the design of controller with complex programmed logic device chips and MCU are presented in this thesis, both of the hardware and software included.The system works well at 4Mbit/s. The transmitting distance is more than 15m, the time taken for toll is less than 0.1s, and it allows cars to pass the toll station at a speed of 108km/h.