This report documents a single-channel architecture offering two-way communication between vehicles and a fixed communication infrastructure. Part I discusses the technical advantages and disadvantages of a dedicated Intelligent Vehicle Highway Systems (IVHS) communications infrastructure versus the use of a hybrid system involving several existing communication networks. Aspects such as spectrum efficiency, message capacity, and network performance are described. Part II proposes a network architecture that offers several transmission services essential to IVHS communications, using only a single (30kHz) radio channel. This narrow bandwidth can accommodate datacasting, packet-switched transmission to and from the vehicle, collection of traffic data from probe vehicles and emergency messages. The proposed architecture may not have enough capacity to support a mature IVHS system, but it provides a scalable method to provide spectrum-efficient wireless access to packet data communications services.

This report summarizes the need for (dedicated) radio spectrum for IVHS communication services. It concludes that, if efficient architectures can be developed, several MHz of spectrum will be needed for large-scale introduction of IVHS services. Compared to most other reported estimates of the spectrum requirements, this report gives a more detailed discussion of the relation between message volume (bit/sec), the required grade of service and spectral bandwidth (Hz).

In this report, the authors describe a method of collecting real-time traffic data from probe vehicles automatically sending traffic reports to one or m ore base stations, connected to a traffic center by a wired communications network. Analyzing and computing road traffic and message traffic flows in the San Francisco Bay Area, the authors study several multi-disciplinary aspects of this data collection technique. The results presented in this report reveal that random access (ALOHA) transmission of traffic messages is a (spectrum) efficient, inexpensive and flexible method for collecting road traffic data and that this approach can provide reliable traffic monitoring. This method allows for the estimation of highly accurate real time link travel times and Automatic Incident Detection (AID) can also be performed.

This study evaluates the performance of radio links and networks to support communication with Automatic Vehicle Control Systems (AVCS). It addresses both vehicle-to-vehicle communication and roadside-to-vehicle communication. The report contributes to the modelling of short range vehicle-to-vehicle channels, not only in terms of documenting measured results and channel parameters, but also in extending existing models to cover antenna mobility at both receiver and transmitter simultaneously. These models are applied to compute the Bit Error Rate performance over radio links. The network aspects considered here are queuing of packets in base station buffers, handovers, and interference from other transmitters in the system.