California Partners for Advanced Transportation Technology

This report describes the design and implementation of a wireless token bus protocol for local area networks. This is the second wireless token passing protocol that has been jointly designed by the PATH program and the faculty and students of the EECS department at UC Berkeley.

The first wireless token bus protocol, designed by Duke Lee and Professor Pravin Varaiya, was successfully implemented to provide the wireless network required by an automated vehicle platoon. The token passing mode of wireless medium access control was chosen to provide the delivery time guarantees required by the safety critical control data transport required by the platoon. This protocol is currently also being used for safe automated vehicle merging maneuvers.

The token bus protocol described in this report represents a significant advance over the first version. The earlier protocol did not permit the wireless radios to dynamically join and leave the network while still maintaining the quality of service for those remaining in the network. This version does. The earlier version also worked only when each wireless radio in the network was within range of every other radio in the network at all times. This version relaxes this requirement. Since mobile wireless LAN’s frequently encounter hidden or exposed terminal configurations, these advances greatly enhance the usefulness of the protocol.