A network architecture of the inter-vehicle packet communication system

We examine the performance of inter-vehicle communication (IVC) systems using the IEEE802.11b standard CSMA scheme and a proposed system in which packet transmission timing is decided by the vehicle position. For the realization of safety cruise-assist systems by IVC systems, the spread of transceivers on vehicles is important. To improve the equipped rate of transceivers on vehicles, it is necessary that the implementation of more simple and cheaper IVC systems. One of the solutions is using conventional wireless LAN systems for IVC systems. So we evaluate the performance of an IVC system using the conventional IEEE802.11b CSMA system. In addition, we propose and evaluate an improvement scheme for solving the performance degradation caused by packet collision. The results of simulation show that the proposed scheme is superior to other schemes when the bit rate is low. Also, it is shown that the proposed scheme has the same or higher performance than the other schemes in high bit rate.

This paper discusses the IVC (Inter Vehicle Communication) system using the UWB (Ultra Wideband) radar. DSUWB (Direct Sequence - UWB) signal is used for this IVC system because it has CDMA (Code Division Multiple Access) Capability. However, there is the near-far problem due to difference of signal power from each vehicles, it becomes the cause of degradation of communication characteristics and detection accuracy of the signal. In this paper, we propose the iterative detection system using the SIC (Successive Interference Cancellation) to improve detection rate of the signal and the bit error rate (BER) performance. The signals except the desired signal detected by the SIC is subtracted from the original received signal. As the result, the performance was improved.

A novel collaborative strategy employing two relays is developed for the multihop inter-vehicle communication (IVC) systems in this paper, which has great complexity degradation. Instead of the traditional terminal collaboration or relay tier space-time coding (STC), a relay tier interaction is proposed. Considering time division multiple access (TDMA) scheme, two spatial adjacent vehicles are conjoined by an interaction radio link to create a virtual antenna array (VAA). Then the collaborative two-relay is integrated into a multihop IVC network mentioned above, which enables a single-antenna terminal to share its antenna with other terminals easily, and avoids the synchronization or other complicated requirements in terminal collaboration or STC systems. Furthermore, except the low complexity in hardware implementation, the proposed method also can enhance the performance of the IVC systems over both the quasi-static fading channel and time varying Rayleigh fading relay channel, which is verified through the Monte-Carlo simulations

Inter-vehicle wireless communication systems are currently being developed as a promising technology to improve traffic safety. Considering their decentralized nature, its deployment faces important challenges to guarantee an efficient and reliable transmission of broadcast safety messages. This paper investigates the dimensioning of such systems by analysing the impact of key operating conditions on its performance. The final aim of this investigation is to identify efficient radio resource management techniques for inter-vehicle wireless systems.

Mutual exchange of status data between vehicles in close proximity is the basis for safe vehicle operation. Application areas range from driver assistance/warning to fully autonomous driving. To enable this data exchange we need an intervehicle communication (IVC) system. Vehicles involved in mutual data exchange form a kind of local area network; however, the characteristics of this network are quite different from those of conventional networks. The configuration of this kind of network changes from time to time, in terms of organization, proximity group, group position, and relative position; therefore, it is very challenging to establish. The authors have been working on this problem from the point of view of communication media and protocol. The characteristics and requirements of IVC are discussed, and several preliminary communication protocols are proposed. The authors also present some experimental results from the implementation of a function integrating communication by infrared ray with a gap-measuring technique by the vision system.

This paper presents results of developing and operating a team of multiple unmanned aircraft system. It is a challenging task since the system complexity increases as the number of the unmanned aircraft increases. Given the autonomy of each vehicle in navigation, guidance, control, and vision-based missions, a system of multiple unmanned aircraft is constructed which is expected to be applied to complicated missions. This paper addresses two essential technologies for automation of such a system: inter-vehicle communication and ground control system. The vehicles can conduct missions by sharing information via inter-vehicle communication without intervention of ground stations. The ground control system is designed to improve situation awareness of the operator managing multiple vehicles. The multiple unmanned aircraft system is verified through flight experiments where the flight scenario is modeled as suppression of enemy air defenses (SEAD) mission, which consists of multisensory target tracking and coordinated formation flying.

Inter-vehicle communication systems may be required to support real-time communication for a network of vehicles in the absence of a base station. Based on this premise, the paper presents the design of a distributed MAC layer protocol, namely the elimination by sieving (ES-DCF) protocol, that incorporates explicit support for real-time traffic in an ad-hoc wireless network. ES-DCF uses the mechanisms of prioritized collision avoidance and deterministic collision resolution in order to provide timely delivery guarantees to different classes of real-time data traffic. The simulation studies performed confirmed that ES-DCF performs well in minimizing the number of hard-real time packets dropped.

Intelligent transportation systems rely heavily on inter-vehicle communication (IVC) systems to support, among other things, safe driving by relaying essential information in real time. It is very important to guarantee the delivery of an imminent collision warning in real time in order to make appropriate actions to avoid it. Several existing MAC layer protocols are modified to address real-time traffic in ad hoc vehicle environment; carrier sense multiple access (CSMA) is one such protocol. This paper implements a priority in CSMA using different backoff time spacing (BTS) to allow higher priority traffic to access the medium faster than those with medium-to-low priority. The backoff time spacing is inversely proportional to the priority; the higher the priority, the lower the backoff time. The paper also proposes a new media access control (MAC) protocol implementation that combines distributed and polling coordination functions to further enhance the BTS-priority-based CSMA and to ensure the absolute delivery of traffic with the highest priority. A computer simulation was carried out to evaluate the performance of the proposed protocol. When compared with the BTS-based CSMA implementation, the simulation results indicate significant improvements in the system throughput and successful packet rate for the traffic with highest priority.

A platooning system, in which vehicles follow a lead vehicle without the road infrastructure, by combining laser radar sensing systems and inter-vehicle communication and navigation system has been developed. It tracks automatically the race line of a lead vehicle. The maximum of five vehicles including a lead vehicle with the minimum inter-vehicle distance of 2 meters ran at the maximum speed of 100 km/h. The accuracy of tracking control was within /spl plusmn/30 cm for the longitudinal direction and /spl plusmn/15 cm for the lateral direction.

In this paper, LMS (Least Mean Square) adaptive array antenna is applied to IVC(Inter-Vehicle Communication) in order to reduce interference which is caused by surrounding vehicles. The LMS adaptive array antenna has a characteristic that the control of directivity is possible according to surrounding radio wave condition, if the receiving vehicle knows the information of the target vehicle. Under the case where the adaptive array antenna is used in IVC systems, packet error rate characteristic, throughput performance and improvement in near-far problem are evaluated by comparing with the performance of the IVC system using omni-directional antenna.

We propose a new way to disperse planning route of transportation using IVC (Inter Vehicle Communication) in this paper. VICS (Vehicle Information and Communication System) has been developed to solve the traffic jam which is one of the ITS (Intelligent Transportation Systems) technologies. The VlCS is able to provide real-time global information with drivers and navigation system which helps drivers to find the fastest route according to the current traffic conditions. However, it is afraid that spatial oscillation of traffic jam "hunting phenomena" will happen if most of cars follow given global information with time delay from VICS. 0n the other hand, IVC is a developing technology which enables cars to exchange various information with others by optical communication, millimeter electromagnetic waves and so on. We therefore propose the combination way to decrease traffic congestion using IVC and VICS. At first we show the hunting phenomena in numerical simulations and the relationship between hunting phenomena and VICS user ratio. We propose a way to disperse planning route by IVC, and then confirm effect of the proposed way in city traffic models in numerical simulations.

Broadcasting in vehicular networks has attracted great interest in research community and industry. Broadcasting on disseminating information to individual vehicle beyond the transmission range is based on inter-vehicle communication systems. It is crucial to broadcast messages to other vehicles as fast as possible because the messages in vehicle communication systems are often emergency messages such as accident warning or alarm. In many current approaches, the message initiator or sender selects the node among its neighbors that is farthest away from it in the broadcasting direction and then assigns the node to rebroadcast the message once the node gets out of its range or after a particular time slot. However, this approach may select a nonoptimal candidate because it does not consider the moving status of vehicles including their moving directions and speeds. In this paper, we develop a new approach based on prediction of future velocity and selective forwarding. The current message sender selects the best candidate that will rebroadcast the message to other vehicles as fast as possible. Key to the decision making is to consider the candidates' previous moving status and predict the future moving trends of the candidates so that the message is spread out faster. In addition, this approach generates very low overhead. Simulations demonstrate that our approach significantly decreases end-to-end delay and improves message delivery ratio.

In this paper, we propose an effective transport system using global information VICS and local information IVC. The VICS (vehicle information and communication system) which is one of the intelligent transport systems, has been developed to release the traffic jam. The VICS is able to give real-time global information to drivers and help drivers to find the fastest route. However, a spatial oscillation of traffic jam will happen, known as hunting phenomena. On the other hand, IVC (inter vehicle communication) is a developing technology which enables cars to give and receive various information by optical communication, millimeter electromagnetic waves and so on. We first investigate the relationship between hunting phenomena and the VICS user ratio, and then realize an effective transport system, in which each car selects a different route and communicate with others by IVC.

We developed the WACNet (wireless ad hoc community network) test system based on IEEE 802.11g and ESPAR antenna. ESPAR antenna is controlled to set sector beam or omni beam due to the several types of packets at the communication situation (Tx and Rx). We can choose the data transmission rate to be adaptive or fixed among the duration through 54 Mbps to 1 Mbps for the purpose of experiment. Routing protocol supporting multihop communication is embedded with the consideration of microwave propagation condition to improve total throughput, total error rate and so on rather than the original protocol. In this paper, we show the structure and wireless communication characteristics and the performance of video streaming at multihop communication with camera and codec connected to WACNet test system on the mobile experimental cars for ITS inter vehicle communications

This paper investigates the propagation characteristics of the inter-vehicle communication system operating in the millimeter band. First, this paper proposes a new propagation model, which takes into account the vehicle traffic, and theoretically derives the path loss and delay profile characteristics using the ray tracing method. Next, this paper investigates the high speed digital transmission performance of the inter-vehicle communication system. Namely this paper theoretically analyzes the bit error rate, required transmission power, and maximum available bit rate of the system. The results show that the vehicle traffic and the antenna size affect the transmission performance. Furthermore, this paper shows the improvement of propagation characteristics by diversity techniques.