On-board units (OBUs) are intelligent functional units in motor vehicles. They are used for the automatic recording and billing of tolls for distances traveled. However, they can also be used for other services. For example, for navigation, route planning and for recording and storing diagnostic and emergency data for the motor vehicle. They can also handle car-to-car communication( C2C), car-to-roadside communication( C2R) and car-to- infrastructure communication( C2I). In these concepts, the on-board unit communicates with the roadside units( RSU).
For the classic application, the determination of the driving route, there are several technical solutions that are reflected in the various toll collection systems and thus in the technology of the OBUs. The various techniques for determining the route are used in Switzerland, Austria and Germany. Some toll collection technologies work exclusively with radio and mobile radio technologies, while others, such as the system used in Germany, additionally use satellite navigation.
The on-board unit calculates the tolls to be paid from the distance traveled. In various systems, the distance traveled is determined via stationary radio beacons, which are used for data transfer with the OBU in the motor vehicle. The radio beacon, also known as a radio beacon, transmits a radio signal that is received by the OBU. This radio signal is modulated by the OBU with the data signal and sent back to the beacon. To ensure that the data sent by the OBU also reaches the radio beacon, the OBUs use two different modulation methods. From the stationary position of the radio beacon, the path distance can be determined.
The toll collection system used in Germany combines satellite navigation with mobile communications technology. For this purpose, the OBUs have a GPS receiver with which the navigation signal of the GPS system is received. The data is sent by the OBU in short message service( SMS) via a built-in GSM modem and the GSM network to the toll center, where the toll is calculated. The toll is calculated from the navigation data, taking into account vehicle-specific data such as the vehicle license plate number, the number of vehicle axles and the exhaust gas class and.