“Wireless Communications for Vehicle Safety:Radio Link Performance & Wireless Connectivity Methods” 2006-21-0030

Many accidents occur today when distant objects or roadway impediments are not quickly detected. To help avoid these accidents, longer-range safety systems are needed with real-time detection capability and without requiring a line-of-sight (LOS) view by the driver or sensor. Early detection at intersections is required for obstacle location around blind corners and dynamic awareness of approaching vehicles on intersecting roadways.

Many of today's vehicular safety systems require short LOS distances to be effective. Such systems include forward collision warning, adaptive cruise control, and lane keeping assistance. To operate over longer LOS distances and in Non-LOS (NLOS) conditions, cooperative wireless communications systems are being considered. This paper describes field results for LOS and NLOS radio links for one candidate wireless system: 5.9GHz Dedicated Short Range Communications (DSRC).

In implementing vehicle safety systems with multiple channels and using vehicles with a single transceiver, consideration must be given to how a group of vehicles in a localized area becomes aware in real-time of potentially dangerous situations. Given that wireless vehicle safety systems may use multiple links, channels, and message priorities, one might ask how these resources could be used in an organized fashion to optimize the efficiency of a wireless system. This paper discusses a method called Multi-channel Management, which enables vehicles to use DSRC resources to synchronize with each other, receive high-priority safety messages with low transmission latency, accommodate any range of safety message traffic, and participate in non-safety services by sharing capacity on other channels. Given that the DSRC system requires that safety-of-life messages have the highest priority, the described method essentially achieves “continuous wireless connectivity” for high-priority safety messages transmitted and received within a localized group of vehicles.

With prolific worldwide growth in the use of wireless local area network (WLAN) adapters to obtain broadband Internet access at WLAN hotspots, automotive OEMs are considering in-vehicle WLAN radio installation. Further, the wireless industry is investigating how handoffs between WLAN and cellular networks could provide connectivity to vehicles when they are out-of-range of hotspots. With this motivation, this paper discusses an approach for providing continuous vehicular links to the Internet using cellular-WLAN roaming.