Directional communication system for short-range vehicular communications

Improving safety in vehicles is achieved today by improving their ability to perceive and react to threats in the environment. Much effort is directed towards increasing the safety envelope around each vehicle with the introduction of increasingly sophisticated sensor technology (e.g., ultrasound, video, thermal imaging, and LIDAR). This envelope can also be increased by leveraging the exchange of safety messages between neighboring vehicles through localized communications between and among vehicles. This paper describes the requirements for messaging in a nearest-neighbor data interchange for several types of safety threats and makes a case for directional communications. The results of our analysis indicate performance limitations for omnidirectional communications and favors a directional scheme. The packet delay approaches 300ms for IEEE 802.11 at a density of 100 vehicles/km in saturation mode for backoff window parameter (W=128). This value is equivalent or close to the human reaction time and is considered unsuitable for safety messaging applicaitons. The design and development of a prototype directional communication system implemented with optical transceivers is described; its related application in providing improved situational awareness in conjunction with an in-car computer platform connected to a local GPS unit and on-board data monitoring interface is also described.