TABLE OF CONTENTS Wireless communications to support IV applications is a quite extensive topic, encompassing technical details, spectrum allocation, and a variety of commercial factors which may drive or impede deployment. A fundamental premise is that early users of such systems must have communications partners to gain value from their investment in communications equipment. In this section, we will provide an overview of the major approaches and trends in this domain.
Electronic toll collection, a very basic form of vehicle-roadside communications, has proven to be a hit all over the world by reducing wait times at toll collection points. These systems operate at a very short range and only require relatively low data rates. What type of expanded data services might vehicles use as they travel the roads in the future? Various applications call for image and video transfer, Internet access, infotainment (movies and music), vehicle status (for real-time diagnostics), traffic and road-relevant information (for traffic management), route guidance, car to car safety messaging, advertising, and yellow page services.
The primary modes of communications supporting CVHS can be distinguished as follows:
Vehicle to/from roadside: requires the use of roadside transponders and supports both vehicle-specific data as well as locally relevant data broadcast to vehicles.
Vehicle to/from external entity (not at roadside): using commercial wireless communications media to a central entity or the Internet via cellular or satellite-based data services.
Vehicle to vehicle: Via ad hoc networking or command/response protocols. V-V modes...
