Broadcasting with Prediction and Selective Forwarding in Vehicular Networks

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.

Basic Safety Messaging plays a crucial role to provide road safety in vehicular ad-hoc networks (VANETs). To avoid potential accidents, vehicles periodically broadcast safety information to neighboring vehicles. However, due to transmission collisions, fading channels and other factors, vehicular networks usually suffer a low packet delivery ratio (PDR) and a large delay, which are intolerant of many safety applications. To tackle these issues, this paper proposes a hybrid medium access control (MAC) protocol for basic safety message (BSM) dissemination based on the framework of Dedicated Short-Range Communication (DSRC). Its partially centralized and partially distributed characteristic not only can effectively suppress the collisions, but keep compatibility with IEEE 802.11p. In addition, the integration of Physical-Layer Network Coding (PNC) and Random Linear Network Coding (RLNC) further strengthens the reliability and efficiency for BSM dissemination. Both the theoretical analysis and comprehensive simulations indicate that, compared with existing schemes, the proposed protocol can significantly improve the PDR by a range of 20% to 300%. Meanwhile, in terms of normalized throughput, it increases by varying percent between 20% and 160% in different scenarios.

In this paper, two IEEE 802.11-based multihop broadcast protocols, namely urban multihop broadcast and ad hoc multihop broadcast, are proposed to address the broadcast storm, hidden node, and reliability problems of multihop broadcast in vehicular networks. In the proposed protocols, the functions of forwarding and acknowledging the broadcast packet are assigned to only one vehicle by dividing the road portion inside the transmission range into segments and choosing the vehicle in the furthest nonempty segment without a priori topology information. The simulation results confirm that our protocols have very high success rate and efficient channel utilization when compared with other flooding-based protocols. It is also concluded that there is no need for infrastructure support unless the line of sight among different road segments incident to an intersection is blocked with obstacles.

In the recent years, ICT use in vehicular technology has expanded very fast. Inter-vehicle communication (IVC) is seen as the natural next step in this evolution whose availability will give rise to the next generation of smart vehicles. As this technology is deployed, a wide range of services varying from safety to entertainment will become factually accessible to passengers. Many of these envisaged services require a one-to-many communication model which demand for intelligent solutions able to propagate the message in areas of the network where it has not been heard before. To this end, we propose an enhancement of an existent optimal message propagation scheme proposed in the context of one dimensional vehicular networks, namely Fast-Broadcast. Our proposal generalizes the former with the objective of guiding message dissemination to an entire area of interest in generic road topologies. Our proposed scheme exploits bloom filter properties to further advance message propagation into the network. We contrast our approach with the original, lightweight state-of-the-art proposal, showing that it fulfills its design objectives.

Reduction of traveling time of ambulance is very important to the safety of users of the transportation system. Vehicular messaging can be used to improve upon emergency response efforts in traffic accidents. This paper realizes an application for emergency message (EM) transmission for rescue services. A dispatched ambulance might occasionally get stuck in a huge traffic and delayed its arrival. The EM, sent via vehicular network, can be used to inform drivers of the traveling ambulance. The recipients of EM could kindly avoid occupying the engaging route (ER) that the ambulance is about to take, such that the medical services can be delivered as quickly as possible. We propose Emergency Messaging for Ambulance Traveling (EM4AT) to smartly reduce transmission cost of EM and to shorten traveling time of ambulance. We develop the simulation to estimate the advised traffic and travel time on ER. It shows that approximately 80% of drivers can receive EM while only 50~60% of the relevant road links are involved for EM transmission.

Vehicular networks face a typical quandary in their requirement for communications that are at once secure and private. While the messages broadcast between vehicles and between vehicles and the supporting infrastructure must be authentic and non repudiable, they must also ensure the vehicle driver's anonymity. The Dedicated Short Range Communications (DSRC) framework's Wireless Access in Vehicular Environments (WAVE) application development architecture mandates the use of Public Key Infrastructure (PKI) mechanisms for securing messages, consequently compromising the driver's expectation of privacy. In this paper, we propose a WAVE-based protocol for the secure and anonymous propagation of vehicle safety broadcast messages. A hybrid key infrastructure approach is put forth which combines the use of a shared network authorization key for devices that require anonymity and PKI for devices that do not.

Networking methods and applications of the inter-vehicle packet communication system are discussed. In a proposed system, vehicles and roadside beacons broadcast individual ID, position, speed in a cyclic manner using time-dots allocated with a distributed algorithm. Other information is transmitted with the random access. The routing method using 1-hop cyclic information is applied to relay the information packet to farther terminals efficiently. This communication system is extensible and realize its applications efficiently. As a new remarkable application of the inter-vehicle communication system, we propose the drive control of vehicles. >

The main purpose of handoff protocol is to provide high data rate and seamless supporting real-time services in the vehicle communication system. Potentially, Wireless Mesh Network (WMN) is one of the best answers to the vehicle communication system. How to provide efficient handoff protocol in the vehicle communication system is the major issue of our design. We analyzed the mathematical module of the vehicle communication system in this paper. Then considering a typical vehicle communication system, we propose a Cross-layer Fast Handoff Protocol (CFHP) which takes into account the signal strength, hops and link state. Compared with the existing AODV based handoff protocols, our protocol with fast handoff mechanism improves the system throughput and the delivery ratio significantly.

The newly emerged vehicular communication network is seen as a key technology for solving the increasingly serious vehicular traffic congestion as well as improving road safety, and applications of vehicular networks are also emerging at the same time. Predicting vehicular visiting time is vital to both solving the vehicular system problem and building efficient vehicular networking. It is an open and unsolved problem that how much the vehicular staying duration of visits to different areas can be predicted. In this paper, we use real vehicular traces in Beijing and Shanghai and an area partition model to explore the limit of predictability of the vehicular visiting time in different areas in large scale cities and analyze the effect of different precision and slot time on predictability. We conclude that using a proper time slot is an efficient way of prediction and a higher predictability can be achieved if the requirement for precision is reduced. Among all the cases we study, we find the highest potential predictability in Beijing and Shanghai in the case with smallest slot time and lowest requirement for precision.

For vehicular networking purposes the main communication standard approach on global scale is the IEEE 802.11p. This protocol-based system, together with the 3G cellular network, was the main elements of our car communications test-bed network. The developed test-bed implements an intelligent heterogeneous traffic safety network between cars and infrastructure. It also offers the possibility to exploit vehicle based sensor and observation data in order to generate intelligent real-time services and a service platform for vehicles. The main goal was to improve traffic safety with accident and weather condition related accurate services, but also to offer a platform for true bi-directional Internet-like networking experience tailored cost-effectively to vehicular environments. This paper presents the field test results of a new standard system for car communication, IEEE 802.11p vehicular networking measurements in Northern Finland (with supporting simulations). The results achieved in developed heterogeneous networking system (with special services) pilot testing are presented also. Based on the experience gained from both field measurements and pilot deployment, we propose a system deployment strategy for simple scenarios with general system efficiency estimation. It is shown that the solution has clear potential for a comprehensive heterogeneous vehicular communication and safety network.

Inter-Vehicle Communication Systems rely on multi-hop broadcast to disseminate information to locations beyond the transmission range of individual nodes. Message dissemination is especially difficult in urban areas crowded with tall buildings because of the line-of-sight problem. In this paper, we propose a new efficient IEEE 802.11 based multi-hop broadcast protocol (UMB) which is designed to address the broadcast storm, hidden node, and reliability problems of multi-hop broadcast in urban areas. Thisprotocol assigns the duty of forwarding and acknowledging broadcast packet to only one vehicle by dividing the road portion inside the transmission range into segments and choosing the vehicle in the furthest non-empty segment without apriori topology information. When there is an intersection in the path of the message dissemination, new directional broadcasts are initiated by the repeaters located at the intersections. We have shown through simulations that our protocol has a very high success rate and efficient channel utilization when compared with other flooding based protocols.

In this paper, we propose an efficient forwarding node selection and density estimation mechanisms for vehicular networks (VANETs). Density estimation is performed without using beacons. Basically, the transmission range is divided into segments. Then, we apply a superposition based analog signal transmission and exploit multi-user capability of OFDM to collect density in each lane and in each segment. With such fine-grained information, a farthest node can be successfully located and selected as the forwarder. The one hop delay is substantially reduced by reducing the contention time and relying mostly on signals instead of control packets to assist the forwarder node selection process. In the simulations, it is observed that the proposed protocol accurately estimates the node density. Also, it outperforms existing multi-hop broadcast protocols in terms of end-to-end delay.

Vehicular networks provide various applications for vehicles to improve road safety and traffic efficiency as well as infotainment. Security and privacy are of great importance for the deployment of vehicular networks. However, how to efficiently secure vehicular networks with privacy-preserving remains a big challenge. Many solutions have been proposed in the past decade, but most of them either rely too much on the ideal tamper-proofed devices or not being efficient enough for scenarios with high vehicle density. Meanwhile, in recent years, great progresses have been made in both the Long-Term Evolution (LTE) and the fifth-generation (5G) wireless network based vehicular networks. The 5G enabled vehicular networks are envisioned to support higher data transmission rate and a larger number of connected devices than the 802.11p and LTE based networks. Noting the great potential of 5G technology, in this paper we explore a new architecture of 5G software defined vehicular network and propose a secure and efficient privacy preserving authentication scheme for vehicular networks. The proposed scheme uses elliptic-curve public-key cryptography and a registration list to achieve efficient message authentication and to avoid the usage of ever-growing certificate revocation list. The security analysis shows that the proposed scheme has strong security guarantees without using the ideal tamper-proofed devices. Simulation results exhibit that the proposed scheme has ultra low computational overhead and packet loss ratio.

In traffic safety applications for vehicular ad hoc networks (VANETs), emergency messages have to be disseminated quickly and extensively in order to inform as many vehicles as possible in a short period of time. Hence, the broadcast storm problem is prone to occur. In the past, several approaches have been proposed to solve the problem. Among them, we find counter-, distance-, location-, cluster-, and probabilistic-based schemes. In this paper, we analyze existing protocols and present a novel scheme that is designed to mitigate the broadcast storm problem, reduce the end-to-end latency in real urban scenarios, and deal with the faults that occur during transmission. The proposed routing protocol assigns a density adopted dynamic back-off time based on traffic flow theory to vehicle. It ensures the dissemination of the emergency message onto every part of the road, and when there is no relay vehicle, the emergency message will be retransmitted. We use the GrooveNet simulator to demonstrate that the proposed scheme has a low collision probability, low overhead and a short end-to-end latency.

Intelligent Transportation Systems (ITS) are gaining momentum among researchers. ITS encompasses several technologies, including wireless communications, sensor networks, data and voice communication, real-time driving assistant systems, etc. These states of the art technologies are expected to pave the way for a plethora of vehicular network applications. In fact, recently we have witnessed a growing interest in Vehicular Networks from both the research community and industry. Several potential applications of Vehicular Networks are envisioned such as road safety and security, traffic monitoring and driving comfort, just to mention a few. It is critical that the existence of convenience or driving comfort services do not negatively affect the performance of safety services. In essence, the dissemination of safety services or the discovery of convenience applications requires the communication among service providers and service requesters through constrained bandwidth resources. Therefore, service discovery techniques for vehicular networks must efficiently use the available common resources. In this thesis, we focus on the design of bandwidth-efficient and scalable service discovery protocols for Vehicular Networks. Three types of service discovery architectures are introduced: infrastructure-less, infrastructure-based, and hybrid architectures. Our proposed algorithms are network layer based where service discovery messages are integrated into the routing messages for a lightweight discovery. Moreover, our protocols use the channel diversity for efficient service discovery. We describe our algorithms and discuss their implementation. Finally, we present the main results of the extensive set of simulation experiments that have been used in order to evaluate their performance.