**3.2.1 Dedicated Short Range Communications**

Dedicated Short Range Communications (DSRC) is a short to medium range communications service that supports both public safety and private operations in V2V and V2I communication environments (DSRC, 2003). DSRC is meant to be a complement to cellular communications by providing very high data transfer rates in circumstances where minimizing latency in the communication link and isolating relatively small communication zones are important.

DSRC is designed for vehicular wireless communications and operates on radio frequencies in the 5.725 to 5.875 GHz (Industrial, Scientific and Medical - ISM) band in Europe and in the 5.850 to 5.925 GHz band in the United States. DSRC systems consist of Road Side Units (RSUs) and On Board Units (OBUs) with transceivers and transponders. The DSRC standards specify the operational frequencies and system bandwidths, but also allow for optional frequencies which are covered (within Europe) by national regulations.

The range of communication using DSRC is up to 1000m with data rates of 6–27 Mb/s, where vehicles may be moving at speeds up to 140 km/h. As mentioned previously, DSRC is divided into two types of communication, namely V2V and V2I. V2V communication is used when vehicles need to exchange data among themselves in order for co-operative applications to work properly, whereas V2I communication is used when roadside units are part of the co-operative application. In co-operative systems, some applications are required to send messages periodically (e.g. every 100ms), whereas other applications send messages when an event occurs.

At this point it should be highlighted that DSRC systems are used in the majority of European Union countries, but these systems are currently not totally compatible. Therefore, standardization is essential in order to ensure pan-European interoperability, particularly for applications such as electronic fee collection, for which the European Union imposes a need for interoperability of systems.

Standardization will also assist with the provision and promotion of additional services using DSRC, and help ensure compatibility and interoperability within a multi-vendor environment.
