The On-Board Unit (OBU)

The SafeTRIP On-Board Unit (OBU) is the device bringing the functionality of the SafeTRIP platform into the vehicle. It can be installed in cars, buses, or trucks giving driver and passengers access to the advantages of the SafeTRIP platform and the services being offered on the platform through the applications running on the OBU.

Reference Architecture

In the SafeTRIP project, a reference architecture has been defined which is generic enough to leave room for differentiation of terminal manufacturers while being specific enough to ensure availability of the required physical channels and functionalities. A fully operable SafeTRIP OBU needs to offer at least the following functionalities:

-     S-band satellite terminal for broadcasting (DVB-SH), messaging (S-MIM) and bi-directional communication (QS-CDMA);

-     Satellite navigation (Global Navigation Satellite System) receiver;

-     Modem to access existing mobile network infrastructure;

-     Gateway to the car infrastructure (e.g. via CAN bus);

-     General-purpose compute resources to host the Service Enabling Layer middleware and the applications;

-     Human-Machine Interface (HMI) to allow the user to interact with the applications.

If not all possible functionalities of the SafeTRIP platform need to be handled by a specific type of OBU, a sub-set may also be used. To offer, e.g., simple tracking capabilities for fleet management, bi-directional satellite communication capabilities could be omitted and the 3G modem could be replaced by a GPRS component.

The functional architecture of the SafeTRIP OBU is shown in Figure 13. For the SafeTRIP platform, the following three logical parts are of particular interest:

-     The (physical) communication modules; shown in orange.

-     The middleware (Service Enabling Layer) running on the general purpose compute resources.

-     The applications.

The S-band satellite terminal is the communication module concerned with forward and return link processing for messaging and connection-oriented communication. Antennas with small form factors compliant with requirements from automotive industry can be used for reception and transmission of the S-band signals.

Figure 13: Functional architecture of the SafeTRIP OBU

The Service Enabling Layer (SEL) provides an open API to the applications, abstracting away the details of the physical communication channels. It is fully based on the Internet Protocol (IP) and handles the communication requests from the application layer and provides adaptation to the communication modules. The SEL also makes available positioning information from the GNSS terminal.

The application layer implements the functionality of the respective application, converting IP data into user information and user requests into IP datagrams. The Human Machine Interface (HMI) handles interaction with the user. Information from the vehicle can be obtained via the Car Gateway, e.g., using CAN-bus access.