Connected Vehicle Project Reveals Ambiguity in Communication Standard

The U. S. Department of Transportation (USDOT) Connected Vehicle (CV) Pilot program has made a significant contribution to the development of vehicular communications standards.

The CV Pilot program is sponsored by the USDOT Joint Program Office for Intelligent Transportation Systems (ITS) to pioneer the deployment of connected vehicle technologies in three U.S. locations. The three locations (New York City, NY, Tampa FL, and the state of Wyoming) are in the design phase, making detailed plans for hardware, software, and communications standards to implement ultra-fast vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I) and vehicle-to-pedestrian (V2P) communication. Trucks, buses, private automobiles, and pedestrians with smart phones will all be equipped with devices to communicate with each other to provide safety-related warnings and to reduce congestion and travel times.

In the area of communications, the projects are using established standards wherever possible, but in many cases, they are trying out standards in the field for the first time, or are implementing messages for which no national or international standards have yet been established.  In such cases, the experience and recommendations of the deployers will be of great assistance to the Standards Development Organizations (SDOs) as they create and update standards that will guide and enable eventual nationwide deployment of connected vehicle technology.

A key component of connected vehicle communication is Dedicated Short Range Communication (DSRC) in the 5.9 GHz band.  Within this band are several channels.  Channel 172 is the primary channel, carrying safety-related information and WAVE Service Announcements (WSAs) that advertise the availability of other information and services on other channels.  The IEEE 1609.4 standard addresses multi-channel operation for Wireless Access in Vehicular Environments (WAVE), and as such is the “official” set of rules for wireless messages by the CV Pilot sites.

The New York and Tampa teams plan to use dual radios in each vehicle: one to listen to channel 172 and the other to listen to other channels for supplementary information such as Traveler Information Messages.    The Wyoming team, on the other hand, originally planned to use a single radio, listening to channel 172 most of the time, but switching to other channels to listen for other messages.  Such a channel-switching plan is consistent with IEEE 1609.4 specifications.  However, the 1609.4 committee and several manufacturers who are looking ahead to implementation of DSRC required by a ruling from the National Highway Traffic Safety Administration (NHTSA), maintain strongly that it is not safe to switch away from Channel 172, because a safety-critical message on that channel might be missed.

The Wyoming team has agreed to re-design its communications design to include dual radios.  However, the discovery that a single channel-switching radio is technically compliant to the 1609.4 standard is a major loophole in the standard that must be addressed and corrected by the 1609.4 committee.

Thus, the experience of the CV Pilot program has made a significant contribution to the eventual nationwide deployment of CV technology.  USDOT expects that the experience of the CV Pilot teams as they design, build, and operate their systems will provide numerous additional valuable inputs to the communications standards development and update process.
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