Dedicated Short Range Communication (DSRC) is currently standardized as a leading technology for the implementation of Vehicular Networks. Non-safety application in DSRC is emerging beyond the initial safety application. However, it suffers from a typical issue of low data delivery ratio in urban environments, where static and moving obstacles block or attenuate the radio propagation, as well as other technical issues such as temporal-spatial restriction, capital cost for infrastructure deployments and limited radio coverage range. On the other hand, Content-Centric Networking (CCN) advocates ubiquitous in-network caching to enhance content distribution. The major characteristics of CCN are compatible with the requirements of vehicular networks so that CCN could be available by vehicular networks. In this paper, we propose a CCN-based vehicle-to-vehicle (V2V) communication scheme on the top of DSRC standard for content dissemination, while demonstrate its feasibility by analyzing the frame format of Beacon and WAVE service advertisement (WSA) messages of DSRC specifications. The simulation-based validations derived from our software platform with OMNeT++, Veins and SUMO in realistic traffic environments are supplied to evaluate the proposed scheme. We expect our research could provide references for future more substantial revision of DSRC standardization for CCN-based V2V communication.

In this paper, we propose an analysis of broadcasting in the IEEE 802.11p MAC protocol. We consider multi-channel operation which is specifically designed for VANET (Vehicular Ad hoc Networks) applications. This protocol supports channel switching; the device alternates between the CCH (Control Channel) and the SCH (Service Channel) during the fixed synchronization interval. It helps vehicles with a single transceiver to access the CCH periodically during which time they acquire or broadcast safety-related messages. Confining the broadcasting opportunity to the deterministic CCH interval entails a non-typical approach to the analysis. Our analysis is carried out considering 1) the time dependency of the system behavior caused by the channel switching, 2) the mutual influence among the vehicles using a multi-dimensional stochastic process, and 3) the generation of messages distributed over the CCH interval. The proposed analysis enables the prediction of the successful delivery ratio and the delay of the broadcast messages. Furthermore, we propose a refinement of the analysis to take account of the effects of hidden nodes on the system performance. The simulation results show that the proposed analysis is quite accurate in describing both the delivery ratio and delay, as well as in reflecting the hidden node effects. The benefits derived from the distributed generation of traffic are also evidenced by the results of experiments.

The emerging Wireless Access in Vehicular Environment (WAVE) architecture, which aims to provide critical traffic information and Internet services, has recently been standardized in the IEEE 802.11p specification. A typical WAVE network consists of one road-side-unit (RSU) and one or more on-board-units (OBUs), wherein the RSU supports one control channel (CCH) and one or more service channels (SCH) for the OBUs to access. Generally, an OBU is equipped with a single transceiver and needs to periodically switch between the CCH and one of the SCHs in order to receive emergency messages and service information from the CCH and to deliver Internet traffic over an SCH. Synchronizing all OBUs to alternatively access the CCH and SCHs is estimated to waste as much as 50% of the channel's resources. To improve efficiency, we propose an innovative scheme, namely coordinated interleaving access (CIA) scheme, which optimizes the SCH throughput by smartly grouping the OBUs to let them access the CCH and SCHs in an interleaved and parallel manner. To further the capability of CIA scheme, an enhanced version is also proposed to handle the case where OBUs with multiple transceivers. Performance analysis and evaluation indicates that the proposed CIA scheme achieves a significant improvement in resource. Thus it can be advantageous to adapt it into the IEEE 802.11p protocol for its adoption in multi-channel wireless vehicular networks.

Intelligent Transport System (ITS), aiming to provide innovative services related to traffic management, road safety and convenience, has drawn much attention in academic and industrial worlds in recent years. Japan has been considered as an advanced country in ITS development. This paper first gives an overview of the current ITS operated in Japan including Vehicle Information and Communication System (VICS), Electronic Toll Collection System (ETC), and ITS-spot system. Then this paper introduces the trends and the directions of future ITS including the development of driver-assistant type of road safety system in Japan and USA, and the potential use of white space to meet the additional ITS needs in the future.

Dedicated Short Range Communication (DSRC) employs one control channel for safety-oriented applications and six service channels for non-safety commercial applications. However, most existing multi-channel schemes require all neighboring vehicles periodically (e.g. every 100 milliseconds) tune to the control channel for a full update of safety-oriented data before they can switch to the service channels for non-safety services. The safety exchange interval increases with the increase of traffic density. Consequently, under high traffic densities, the service channels are often completely idle while the control channel is congested. We propose a RSU Assisted Multi-channel Coordination MAC (RAMC) protocol that fully utilizes all channels to provide simultaneous safety and non-safety communications. Within the radio range of a roadside unit (RSU), vehicles are free to tune to any service channel. The RSU monitors all the safety messages being transmitted in both the control and service channels. Periodically, the RSU broadcasts a consolidated traffic view report to all neighboring vehicles in all channels. Therefore, a vehicle can operate in a service channel as long as it needs to achieve high throughput for non-safety applications, while maintaining adequate and timely safety awareness. Our simulation results show that the proposed RAMC protocol consistently achieves very high percentage of non-safety usage, while maintaining high safety message delivery ratios in various traffic density conditions.

A QoS management technique based on an autonomous decentralized mobility system, which is an autonomous decentralized system enhanced to provide mobile stations with information about urgent roadway situations, is proposed in this paper. This technique enables urgent messages to be flexibly and quickly transmitted to mobile stations by multiple decentralized base stations using dedicated short range communication. It also supports the easy addition of additional base stations. Each station autonomously creates information-delivery communities based on the urgency of the messages it receives through the roadside network and the distances between the senders and receivers. Each station dynamically determines the urgency of messages according to the message content and the speed of the mobile stations. Evaluation of this technique applied to the Smart Gateway system, which provides driving-assistance services to mobile stations through dedicated short-range communication, demonstrated its effectiveness and that it is suitable for actual systems.

We previously proposed an architecture for software defined radio called the reconfigurable packet routing-oriented signal processing platform (RPPP). This architecture was suited to wireless signal processing applications, which require radio functions to be selected in real time depending on the transmitted signal. A number of radio standards are used in DSRC systems for vehicle communication and vehicle equipment is required to transmit and receive the radio signals used on each particular occasion. An implementation of RPPP is described in this paper that enables the dynamic handling of two ARIB standards for DSRC. After an explanation of the basic architecture and an analysis of RPPP, the implementation of a reconfigurable DSRC transceiver for ASK and π/4 shift-QPSK is described. The implementation is then discussed, evaluated in terms of the number of logic units needed. We concluded that our platform is 27.6% more efficient in utilizing logic than that achieved with fixed design.

Electromagnetic (EM) wave absorbers have been used for improving the EM environment of an electronic toll collection (ETC) system on an express highway or a wireless local area network (LAN) system in an indoor environment. In this paper, an efficient multi-ray propagation model, which uses 3D geometry and image techniques to trace multiple signal rays from transmitter to receiver, is employed to analyze the EM environment of a dedicated short-range communication (DSRC) system on an express highway. The validity of the model employed is discussed by the comparison with the results obtained by an experiment on the highways. The analysis shows that the possible undesired communications between onboard equipment that acts as a receiver and DSRC beacon which transmits the radio signals, is improved by increasing the EM wave-absorption capability of the sidewalls and the pavement of the highway. Another advantage of the employed model is that it is effective for investigating the location of wave absorbers to be set up on the highway, and it takes only a fraction of a minute for computation.

In this paper we propose a new reconfigurable signal processing platform for SDR, having capability to change its processing parameters dynamically. On our proposed platform, while the wiring and processing scheme remain fixed, processing parameters and connections between processing modules together with the associated dataflow can be changed. We also demonstrate that our proposed signal processing platform has the new ability of easily composing new signal processing models dynamically, simultaneously with other tasks, and attaining high efficiency of logic usage.

It is known that the thickness of the λ/4 type EM wave absorber having a resistive film with the capacitive reactance is thinner than 1/4 wavelength. This paper investigates EM wave absorbers using the resistive film with capacitive reactance. We introduced the impedance into the resistive film, and then clarified the relationship between the impedance and the matching thickness in the single layer EM wave absorber. Practically, we carried out to grasp the impedance of the resistive films, which were prepared using the conductive flake powder. As the results, we have proven that the matching thickness in the single layer EM wave absorber could be realized 0.17 λ-0.09 λ in the frequency range from 2 GHz to 8 GHz by using these resistive films. We also fabricated the single resistive layer and the double resistive layers EM wave absorber using these resistive films for Dedicated Short Range Communications (DSRC) and wireless Local Area Network (LAN), in which the matching thickness could be reduced to 45% and 30%, respectively, as compared with the each absorber using the non-capacitive reactance.

Electronic Toll Collection (ETC), an application of Dedicated Short Range Wireless Communication (DSRC), had suffered from wrong operations due to multipath problems. To solve this problem, we proposed to apply a simple configured path determination scheme for the ETC system. The system consists of a vector network analyzer, low-noise amplifier, and X-Y positioner and achieves an automatic measurement of the spatial transfer function with emphasis on accurate measurement and reproducibility. For the reliable identification of the propagating paths, 3-D Unitary ESPRIT and SAGE algorithms were employed. Having developed the system, field experiments at the toll gate of the highway was carried out. In the measurements, we could determine many propagation paths so that the dominant propagation phenomena at the toll gate was identified. They included a ground-canopy twice reflected wave, which was a potential path that caused wrong operation. Consequently, their reflection coefficients and polarization characteristics were investigated. From the results, applicability of the path determination system for short range on-site measurement was confirmed.

This paper presents experimental results of a future road-to-vehicle communications system with handover function. The proposed handover scheme, based on the current Dedicated Short Range Communication System (DSRC) standard (ARIB STD-T75) in Japan, maintains the continuity of data transmissions over multiple radio zones by transferring received and remaining data between base stations located along the roadside. Moreover, a link connection/disconnection method is newly proposed to avoid repetition of link connection and disconnections around the cell entrance and to actualize smooth handover between cells. The proposed method determines the link connection and disconnection timing by measuring the received signal strength and observing the results of CRC (Cyclic Redundancy Code) error checks of the control channel. By applying the proposed method to mobile stations (MS) in the DSRC system, the communication link between the MS and the base station (BS) can be smoothly connected. Field experiments were conducted to evaluate the performance and validity of the proposed methods using actual equipment. Experimental results show that the proposed methods perform a smooth link connection between cells and achieve a very short handover processing delay of less than 42 milliseconds.

In order to realize a future seamless high-speed road-vehicle communication system, we have proposed using code division multiplexing (CDM) radio transmission scheme by using cyclic shifted-and-extended (CSE) codes as spread codes. As the CSE codes are generated by cyclically shifting and extending a conventionally used code, the number of codes generated from a code is limited to the length of the shift interval and the tolerable period of delayed waves also depends on the length. In this paper, based on CSE codes, we propose a method to minimize the length of the shift interval and a cancellation technique with a simple calculation in order to eliminate the interference from delayed waves caused by the reduction of the length of shift interval. The concept and the BER performances in AWGN, two-paths, and multi-path fading environments are described in this paper. As a result, the maximum transmission rate of CSE-based-CDM transmission per one-code using the newly proposed transmission scheme is 3 times as large as that using conventional CSE codes and DQPSK-CDM transmission scheme.

A number of mobile hosts might be densely staying in an area caused by traffic congestions. The greater part of the mobile hosts will require commonly useful data, such as traffic information, parking information and other driving related information in such environment. Simultaneous data transmission broadcasts using a common link are regarded as a suitable means to distribute this location-dependent information. However, there is no guarantee that mobile hosts can finish receiving the information completely within a limited time. In this paper, we propose a data retransmission method for communications between a base station and mobile hosts and a data recovery processing method for use between base stations. The data retransmission method called "TOA" (The Order of Arrival) schedules retransmission data specified in the first NACK request received after retransmission processing. We have proposed "Advanced" Join system in which a base station makes consolidated join requests to a multicast group on behalf of mobile hosts. Applying the TOA method to resending in the Advanced Join system, data-receiving efficiency is higher than with the simple Advanced Join system and the absolute number of completed mobile host data reception is higher. Using the TOA method, even with the base station disposition rate of 50% the number of completed reception is higher than with the Advanced Join system at 80%. The proposed reliable multicasting system to the DSRC-based ITS network can realize an efficient base station arrangement in the ITS network infrastructure and contribute to the deployment of a superior ITS.

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.