Dynamic Transmitting Power Adjustment in Cooperative Vehicular Safety Applications

Cooperative vehicular safety application is a critical ITS service in traffic management. Each On Board Unit (OBU) must periodically broadcast its current status to its neighboring vehicles. Because of lacking the transmitting power adjustment, each OBU always uses the maximum transmitting power. From the authors' experiments, at heavy traffic flow, the higher transmitting power causes the wireless channel contentions and packet collisions to be more serious. This paper identifies these problems and proposes the dynamic transmitting power architecture to soften these situations based on the car’s speed, position, and vehicle density. The authors also present three procedures, which are safety broadcast procedure, event-driven warning procedure, and hazard detecting procedure, not only to reduce traffic accidents but also to increase the delivery rate of safety packet dissemination. Finally they verify the results by simulations and make conclusions.