TR2010-101

Safety Message Transmission in Vehicular Communication Networks



Emerging vehicular safety applications require low latency communications and reliable packet dissemination for life saving safety messages. Significant developments have taken place over the past few years. IEEE WAVE and ISO CALM have been developed as international standards for ITS applications. Both WAVE and CALM support multichannel operations and use CSMA/CA as channel access mechanism. WAVE may impose a latency of 54 milliseconds for enabling multi-channel operations. CSMA/CA method can experience unpredictable delay and packet drop when channel is congested. In this paper, we propose an innovative technique to increase channel coverage and reduce latency for safety messages in multi-channel vehicular environments. We also propose an efficient congestion control protocol for vehicular communication networks that use CSMA/CA channel access mechanism. The proposed congestion control protocol guarantees that safety messages gain channel access while contending with other messages. Technologies presented in this paper improve reliability of the safety message dissemination and reduce latency for safety message transmission.