Abstract
Recently, Intelligent Transport Systems (ITS) have gotten a lot of attention to solve various traffic problems. ITS, which combines humans, roads, and vehicles using state-of-the-art Information Technology (IT) are new transport systems for the purpose of the solution of the road transportation problems, an efficient traffic flow and reduction of the environmental load.
Especially, the achievement of ITS can contribute to the traffic safety. Delays in driver’s recognition and errors in operations and judgment cause about 80% of traffic accident fatalities by causes of traffic accidents. Thus, we research inter-vehicle ranging system. That system gives drivers with information and danger warning, and operational support, should be effective for traffic accidents. Especially, we focus on a inter-vehicle ranging system by inter-vehicle-communication that we call Communication-Base-Ranging (CBR) and the radar which is a conventional inter-vehicle ranging system.
The radar system is encouraged practice use. A vehicle transmits a signal and received a reflected wave from a target, and then detects an existence of the target, a distance to the target, and an angle of the target. On the other hand, the CBR system is more advanced method of vehicular collision avoidance. In this system, vehicles exchange the transmission time and vehicle control information such as acceleration, speed, break signaling, by ultra wideband (UWB) signal, very high temporal resolution, directly to close-by vehicles. At the same time, vehicles are assumed to be able to synchronize each clock accurately. A vehicle which received the signal measures transmission time against receipt time and calculate the exact distance to the transmitting vehicle. Thus, drivers can get the inter-vehicular distance information by accuracy equal with the radar system and can use information of blind area.
However, in order to get that information by using the CBR system, all vehicles must implement this system. When a target vehicle doesn’t have this system, a vehicle which has the CBR system cannot measure the distance, and cannot obtain information of blind area. Consequently, we proposed the hybrid of CBR and radar so that inter-vehicle ranging can be successful to the vehicle which has no system too. In this proposal, first, a vehicle transmits the communication signal which includes transmission time, vehicle control and blind area information. When the target vehicle has the CBR system, vehicles can realize the advanced collision avoidance by the CBR system. When the target vehicle has no CBR system, the vehicle measures the inter-vehicular distance by the radar system to receive that reflected communication signal from the target vehicle. In this paper, we considered about the case that the hybrid system uses a packet structure which has serially-concatenated preamble symbol term and data symbol term. We theoretically derived the packet structure which improves ranging characteristics.
Keywords: ITS, Inter-Vehicle-Ranging, Communication-Base-Ranging, short range radar, DS-UWB (Direct Sequence-Ultra Wideband)