We have developed a dedicated onboard “sensor” utilizing wireless communication devices for collision avoidance around road intersections. The “sensor” estimates the positions of transmitters on traffic participants by comparing the strengths of signals received by four ZigBee receivers installed at the four corners of a vehicle. On-board sensors involving cameras cannot detect objects in non line-of-sight (NLOS) area caused by buildings and other vehicles. Although infrastructure sensors for vehicle-to-infrastructure (V2I) cooperative systems can detect such hidden objects, they are substantially more expensive than on-board sensors. The on-board wireless “sensor” developed in this work would function as an alternative tool for collision avoidance around intersections. Herein, we extend our previous work by considering a road surface reflection model to improve the estimation accuracy. By using this model, we succeeded in reducing the error mismatches between the observed data and the calibration data of the estimation algorithm. The proposed system will be realized on the basis of these enhancements.

A stacked rectangular microstrip antenna with a shorting plate and a helical pin is proposed as a car antenna for triple band operation in ITS. The proposed antenna operates as a conventional stacked microstrip antenna at the highest frequency band. At the middle and the lowest frequency bands, the antenna radiates at low elevation angles from the helical pin and the shorting plate. In this paper, as an example of triple band antennas in the ITS, an antenna is designed that supports PHS, VICS and ETC. The proposed antennas have the proper radiation pattern for each application and are small in size.

An atmospheric visibility measurement system capable of quantifying the most common operating range of onboard exteroceptive sensors is a key parameter in the creation of driving assistance systems. This information is then utilized to adapt sensor operations and processing or to alert the driver that the onboard assistance system is momentarily inoperative. Moreover, a system capable of either detecting the presence of fog or estimating visibility distances constitutes in itself a driving aid. In this paper, we first present a review of different optical sensors likely to measure the visibility distance. We then present our stereovision based technique to estimate what we call the "mobilized visibility distance". This is the distance to the most distant object on the road surface having a contrast above 5%. In fact, this definition is very close to the definition of the meteorological visibility distance proposed by the International Commission on Illumination (CIE). The method combines the computation of both a depth map of the vehicle environment using the "v-disparity" approach and of local contrasts above 5%. Both methods are described separately. Then, their combination is detailed. A qualitative evaluation is done using different video sequences. Finally, a static quantitative evaluation is also performed thanks to reference targets installed on a dedicated test site.

The performance of the vehicular communication links used for Intelligent Transport Systems is investigated. Intervehicle communication (IVC) and combined vehicular communication implemented by IVC and additional communication media are studied and their performance is explicitly described. Through numerical studies, it is shown that performance varies according to parameter values such as the mean space headway, the speed of the vehicles, and the penetration ratio of the IVC device. To achieve a given level of performance, I propose (i) a design of the information delivery delay of additional communication media and (ii) a method determining the appropriate delay.

This paper introduces a state-of-art on an ultra-wideband (UWB) technology in intelligent transport systems (ITS). To examine the detection performance of a UWB short-range radar for vehicular applications, we developed a 26-GHz band short-range UWB radar system with an embedded compact MMIC-based RF module. In this paper, we briefly comment on the current regulatory environment for UWB radar systems by outlining the structure of an international organization involved in examining the regulatory status of these systems. We then describe the principles of detection and system design for impulse radar, the radar system that we developed, and a MMIC-based RF module as well as the performance of these devices. We measured their performance in a series of laboratory experiments and also measured UWB radar cross sections of an automobile. The results of our experiments suggest that our radar system is capable of detecting targets with a range resolution of around 9 cm.

The roadside network system for ITS services uses microcells in its access infrastructure. For the roadside network that provides the uninterrupted communication using microcells such as DSRC, an effective communication control scheme must be established so as to manage the communication passes to vehicles in the network. One of the fundamental requirements for the communication control scheme for the roadside network is to assure fault-tolerance, which means in this system that the communication control mechanism needs to be managed even in part of the base stations in the network might be in fault. On the other hand, for the communication control in the roadside network using microcells, issues to be solved are the handover mechanism for taking over connection information to provide uninterrupted communication environment, which causes the degradation of the end-to-end throughput. In order to solve those problems, the authors developed a communication control scheme. We implemented the scheme as the specific 'ADS algorism' to control the communication zone dynamically, which works effectively on the Autonomous Decentralized System (ADS) communication platform. Furthermore, we also developed the specific ADS algorism to assure fault-tolerance for the communication zone control, which can reconfigure the communication zone in case the BSs in the roadside network are in fault and can keep the operations by the reconfigured communication zone. We evaluated the ADS algorism for the communication zone control by computer simulation. The results show the effectiveness of the ADS algorism for the dynamic communication zone control mechanism and for the fault-tolerant mechanism for communication zone reconfiguration on fault.

In order to achieve a transponder antenna for intersection collision avoidance systems in Intelligent Transport Systems, a lens horn antenna that generates a cosecant squared beam is developed. This paper clarifies the method for designing the antenna to achieve accurate radiation pattern synthesis. A H-plane sectral horn is selected. The ray tracing method is employed in the design of the lens shape. The aperture of the horn is determined to be seven wavelengths based on a comparison of calculated radiation patterns and the desired cosecant squared beam shape. Accurate electrical performance, such as radiation patterns and electrical fields in the horn, is calculated using Finite Difference Time Domain software. Electrical field disturbances caused by reflected waves at the lens surfaces expanded widely inside the small horn. As a result, sidelobe levels of the radiation patterns are increased. In order to eliminate these disturbances, matching layers are attached to the shaped lens surface. Then, electrical field distributions in the horn are recovered and disturbances disappear. Measured radiation patterns become almost the same as that designed using the ray tracing method. The results show that application of the ray tracing method to radiation pattern synthesis of a small lens horn antenna is effective. We clarify the electrical field disturbances caused by reflections at the lens surfaces and show that eliminating the reflection at the lens surface by attaching matching layers is very important to achieving radiation pattern synthesis.

In this paper, we propose a new content delivery platform on the ITS (Intelligent Transport Systems) road-vehicle communication system on the basis of ROF (Radio over Fiber). The platform is strongly motivated by the ROF communication system capabilities of (1) broadband access, (2) integrated multiple service transmission interface, and (3) simultaneous use of a single and downsized vehicle terminal shared among multiple services based on a multi-mode software radio system. Content is delivered on per reservation basis, as is carefully envisaged as a primary service which is subjected to immaturity of early ITS road-vehicle communication systems, and is provided in limited service areas such as parking on main highways. After the reservation, requested content is stored in a cache connected to a ROF local station via optical fiber. At the designated time, the content is delivered from the cache to a target terminal by way of the ROF local station at high-speed. It can also be done by moving the content from the cache to another cache depending on the target terminal location in a flexible and reliable manner, even if the target terminal could not reach the place at the time designated in the reservation. Such flexibility and reliability are required for consequent practical application, and are provided using information given in the reservations. We implement a preliminary system to evaluate the proposed platform from the viewpoints of (1) processing time from logging into the system for a reservation to delivering content to the target terminal and (2) amount of control traffic required for the delivery. The results show that the proposed platform in which content is delivered from a cache connected with a ROF local station distributed geographically is effective. We also evaluate content delivery throughput using the system connected with an actual ROF local station, and show that the effective throughput is 40 Mbps and the proposed platform is a promising ITS service platform. The paper concludes by discussing future study toward realizing a more promising and practical system.

As a center of mobile multimedia of the 21st century, it is very much looking forward to explosion of R&D and business of the next generation of mobile communication systems and the ITS (Intelligent Transport Systems) because ITS will enable information-oriented in the field of the road, traffic and vehicles, by using the most advanced technologies of mobile communications and devices, for the various purposes such as decrease of the traffic accident, the reduction of traffic jam, the increase in efficiency of the logistics and the harmony with the earth environment. This invited paper will first briefly introduce evolution of mobile communications and ITS in ministries, industries and academia in Japan. Then core communication technologies for ITS will be overviewed such as spread spectrum CDMA, adaptive antenna array, and software radio or software defined radio. Demands of SoC (System on a Chip) to carry out the core technologies will be addressed.

CRL (Communications Research Laboratory, Independent Administrative Institution Japan) is developing a road to vehicle multiple-service communication system based on RoF (Radio over Fiber) technology in a millimeter-wave frequency region of 36-37 GHz. In the experimental system, vehicle can receive three wireless services such as PHS (Personal Handy-phone System), ETC (Electronic Toll Collection system), SB (Satellite Broadcasting). In this paper, the system concept and experimental system configuration are introduced. Furthermore, SDR (Software Defined Radio) mobile terminal technology is mentioned and a new concept for a next generation mobile communication network system based on RoF is proposed.

Mobile computing networks make it possible to offer information access to mobile users. In order to transfer data over mobile networks efficiently, appropriate data transmission control methods for mobile terminals must be established. This paper focuses on spot communication systems to transmit data at high speeds between base stations and mobile terminals. It proposes a flexible and efficient data transmission method that is suitable for spot communication systems. The proposed method transfers subsets of the data to the base stations that are best sited relative to the mobile terminal. This helps to reduce the traffic load of the network significantly. Simulation results confirm the validity of the proposed method. Furthermore, the data receiving time of the mobile terminal, which is an important measure in evaluating the Quality of Service (QoS) for data transmission is analyzed. The result shows that the traffic load in the network is reduced significantly while the QoS is well maintained.

Image processing about the vehicle is considered in this paper. When a vehicle is in a factory, image processing is applied for design and inspection, and when vehicle is on the road image processing is useful for Intelligent Transport Systems, which recently have been developed widely. There have been many researches and implementations using image sensors to get information for traffic control and vehicle control. The image seen from camera located beside or upon the road can be used for vehicle detection, velocity of car or car group measurement, parking car detection, etc. Moreover the image seen from camera located in vehicle can be used for preceding car detection, measurement of the distance to preceding car, obstacle detection, lane detection, etc. In this paper, studies about Image Processing for vehicle on the road are described.

This paper describes code assignment and the multicode sense scheme for an inter-vehicle CDMA communication network. When considering an inter-vehicle broadcasting CDMA communication network, spreading code assignment and notification problems arise. In such a CDMA network, the use of common codes is a solution. Then an objective function of common code assignment in an IVCN is formulated as a combinatorial optimization problem. In addition, a multicode sense (MCS)/CDMA system is proposed as a simple code assignment scheme. Computer simulations show that the MCS/CDMA system can autonomously perform spatial rearrangement of the common codes using only local information that each vehicle can obtain by sensing the code channels.

In the ITS (Intelligent Transport Systems), it is an essential condition (mixed environment) that vehicles that have communication equipment and vehicles that do not have it simultaneously run in the same road. In this paper, a vehicular driving assistant system that is applicable to the mixed environment is proposed. The proposed system uses spread spectrum techniques and consists of several new systems such as a PN code assignment system, new vehicle position systems, and a vehicle map update system. In the proposed system, the wireless broadcast CDMA is used for inter-vehicle communications. This paper also shows preexaminations of the proposed system by using an autonomous traffic flow simulator including inter-vehicle communications. It is shown that the traffic safety can be improved by using inter-vehicle communications.