The Design Of OBU System Architecture And Implementation Of DSRC Layer 2 For ETC Applications

Intelligent Transport Systems (ITS) applies Computer, Communication, Sensor, and Electronic technologies into traditional transport management. The combination of these high technologies provides a decent solution for many unresolved issues of manual transport management, like the bottle-neck issue of highway entrance, etc. Efficient management of traffic makes almost everything more efficient in our normal life.Since communication technology is an essential component of ITS, a feasible solution should be provided as the core commnunication solution for ITS. Dedicated Short-Range Communication (DSRC) protocol is a mainstream communication protocol for ITS solutions. This protocol is a kind of communication protocol dedicated to transportation system. It defines two entities: On-Board Unit (OBU) and Road-Side Unit (RSU). All communications in DSRC involve these two entities. Nowadays, the primary application for DSRC is Electronic Toll Collection (ETC). It defines an automatic fee collection system for highway usage. Many European countries, US, and Japan put ETC into practice in some area. China is also doing research and testing of ETC applications, as well as DSRC standard.This paper proposes a complete system architecture of OBU for ETC applications based on DSRC protocol. This architecture, which is based on non-OS embedded system design, provides a whole structure of low level system components and some essential OS-like system components. The components as well as the architecture are designed with DSRC real-time constrains in mind. Some components are especially designed and optimized for making OBU feasible in real environments.Based on the whole system architecture and low level components, I also implemented the data link layer of DSRC protocol. The data link layer of DSRC consists of MAC and LLC sublayers. These two layers addresses media access control and basic transmission issues. My implementation has all the features defined by DSRC specification. Although the low level component (STR71x HDLC controller), which has some limitations in noise immunity and timing, is not suitable for DSRC application, the high level implementation of DSRC data link layer can be ported to other platform with very little modification.