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Cooperative Vehicle Safety System for VANETs

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  • T. Sujitha, Final year M.E(CSE),



Vehicular ad hoc networks (VANETs) are a one form of wireless networks used for vehicles communication among themselves on roads. The conventional routing protocols are suitable for mobile ad hoc networks (MANETs). But it’s poorly in VANETs. As communication links break often happen in VANETs compare than in MANETs, the reliable routing is more difficult in the VANET. Research work has been done to the routing reliability of VANETs on highways. In this paper, we use the cooperative vehicle safety system for VANETs. The cooperative vehicle safety system helps to capture the future positions of the vehicles and determines the reliable routes preemptively. This paper is the first to propose a cooperative vehicle safety system for VANETs gives quality-of-service (QoS) support in the routing process. A new mechanism is developed to find the most reliable route in the VANET from the source vehicle to the destination vehicle. Through the simulation results, that the proposed scheme significantly give good result compare than other literature survey.

Keywords- vehicular ad hoc network (VANET),DSRC, IEEE 802.11,sensor,OBU,RSU.


Every day, a most of people die, and many people are injured in traffic accidents around the world. The desire to improve road safety information among vehicles to prevent accidents and improve road safety was the main motivation behind the development of vehicular ad hoc networks (VANETs). VANETs are a promising technology to enable communications among vehicles on roads. They are a special form of mobile ad hoc networks (MANETs) that provide vehicle-to-vehicle communications. It is assumed that each vehicle is equipped with a wireless communication

facility to provide ad hoc network connectivity. VANETs tend to operate without an infrastructure, each vehicle in the network can send, receive, and relay messages to other vehicles in the network.

Figure 1.1 Structure of Vanet Ad-hoc Networks

This way, vehicles can exchange real-time information, and drivers can be informed about road traffic conditions and other travel-related information. The most challenging issue is potentially the high mobility and the frequent changes of the network topology. In VANETs, the network topology could vary when the vehicles change their velocities and/or lanes. These changes depend on the drivers and road situations and are normally not scheduled in advance.

Embedded wireless devices are the main components of evolving cooperative active safety systems for vehicles. These systems, which rely on communication between vehicles, deliver warning messages to drivers and may even directly take control of the vehicle to perform evasive maneuvers. The cyber aspects of such applications, including communication and detection of vehicle information are tightly coupled with physical dynamics of vehicles and drivers behavior. Recent research on such cooperative vehicle safety (CVSS) systems has shown that significant performance improvement is possible by coupling the design of the components of the systems that are related to vehicle dynamics with the cyber components that are responsible for tracking other cars and detecting threats.

The types of possible actions and warnings in vehicle safety systems range from low-latency collision avoidance or warning systems to moderate-latency system that provide heads up information about possible dangers in the non immediate path of the vehicle. The main differences of these systems are the sources and means of information dissemination and acquisition. In active safety systems, vehicles are required to be continuously aware of their neighborhood of few hundred meters and monitor possible emergency information. This task can be achieved by frequent real time communication between vehicles over dedicated short range communication (DSRC) channel. In addition to inter-vehicle communication; roadside devices may also assist vehicles in learning about their environment by delivering traffic signal or pedestrian related information at intersections. The main requirement of these active safety systems is the possibility of delivering real-time acquired information to and between vehicles at latencies of lower than few hundred milliseconds. Prototypes of such systems are being developed by many automotive manufacturers.


In DSRC based safety systems, the cyber components are selected so that they meet the requirements of active safety. Nevertheless, the existing designs fall short of supporting a full-fledged CVSS in which a large number of vehicles communicate and cooperate with each other. The main reason behind the issues with the current designs is the level of separation in the design of different components. Later in this paper we describe methods to achieve better performance by further cooperation of the physical and cyber sub-components. In the next subsection we describe existing active safety CVSS systems and their designs.

Figure 1.2 Communication in VANET systems.

The traditional design of the CVS system, based on the structure depicted, is a straightforward design following the recommendations of an early report by vehicle safety communication consortium (VSCC). According to this report, it is suggested that vehicles should transmit tracking messages every 100ms, to a distance of at least 150m (avg. 250m). Therefore, the message generation module in becomes a periodic process that outputs a sample of the current state of the vehicle in a message every 100msec. The DSRC radio power is set to reach the suggested distance. Given the issues of the above design in crowded networks, several enhancements have recently been proposed to improve the performance of CVS systems beyond the early solutions set forth by VSCC. One such method is the work in [22] that proposes to fairly allocate transmission power across all cars in a max-min fashion; this method helps reduce the load at every point of a formulated 1-D highway and thus reserves bandwidth for emergency messages with higher priorities.

This method assumes a predefined maximum load as the target. In another work, a message dispatcher is proposed to reduce required data rate by removing duplicate elements, here, the idea is that many applications require the same data elements from other vehicles. The message dispatcher at the sender side will group data elements from application layer (i.e., the source) and decides how frequently each data element should be broadcast.

The above methods focus on the computing module, as defined in this section, and try to improve its performance through observing the behavior of the application, or by incorporating limited physical process information in the design of the computing module. While the above improvements do enhance the performance of CVS systems, these designs do not consider the mutual effects of computation, communication and physical processes on each other. In this, try to identify such mutual effects and propose a design that uses the knowledge of the tight coupling of cyber and physical processes to the benefit of a CVSS system.


DSDV is a proactive protocol that maintains route to all the destinations before requirement of the route. Each node maintains a routing table which contains next hop, cost metric towards each destination and a sequence number that is created by the destination itself. This table is exchanged by each node to update route information. A node transmits routing table periodically or when significant new information is available about some route. Whenever a node wants to send packet, it uses the routing table stored locally.

For each destination, a node knows which of its neighbor leads to the shortest path to the destination. DSDV is an efficient protocol for route discovery. Whenever a route to a new destination is required, it already exists at the source. Hence, latency for route discovery is very low. DSDV also guarantees loop-free paths.


Cooperative message authentication protocol, which augments the basic short group signature protocol by mitigating the computation overhead in the regular broadcast phase. According to, the verification time for short group signature is 11ms with a 3 GHz Pentium IV system. In a typical public safety application, each vehicle broadcasts safety messages every 300 ms, which implies that each vehicle can at most process messages from other vehicles in a stable system.

However, according to the measurement, there may exist as many as 87 vehicles broadcasting messages within the 300m communication range of a receiving vehicle, far exceeding its processing capability. Therefore, we propose a cooperative message authentication protocol to fill the gap between the workload and the processing capability.


RSUs broadcast I-public keys, G-public keys of themselves and their neighbor RSUs with certificates and identities of revoked RSUs in their neighborhoods regularly. Authorities employ benign RSUs around compromised RSUs to implement revocation by regular broadcasting those compromised RSUs’ identities. When a vehicle detects the hello message, it starts registration by sending its I-public key and the certificate to the RSU if the RSU is not revoked. Normally, a public key should not be encrypted.

However, in our system model, each vehicle’s I-public key is unique, so it is also an identifier of the vehicle. We encrypt it to protect vehicle’s privacy. The RSU sends the hash value of the G-private key which plans to be assigned to the vehicle and the signature of the hash value, vehicle’s I-public key and RSU’s I-public key to the vehicle. RSU’s I-public key is also unique. The vehicle can identify the RSU’s legitimacy after it verifies this message because the RSU uses its I-private key in the message. The vehicle encrypts its Npri and the timestamp by using authorities’ public key. Then, it sends the encryption data with the timestamp and the signature of corresponding information, message 4, to the RSU.

The encryption of its Npri and the timestamp is a commitment. It can be useed to detect illegitimate users later. Meanwhile, the signature signed by the vehicle binds vehicle’s information and the assigned G-private key. Then, the RSU cannot re-map them because the RSU does not have vehicle’s I-private key. The RSU sends the G-private key to the vehicle. The vehicle finishes registration procedure after it gets a valid G-private key. Then, the RSU stores the information, as in the local database. The signature in the fifth item is the signature that the RSU receives in message. If authorities need the information of a vehicle when there is a dispute, the RSU has to send the vehicle’s corresponding information to authorities.


The performance of the proposed algorithm is evaluated through network simulator version 2. A cooperative message authentication protocol(CMAP) is presented to alleviate vehicles computation burden. In the protocol, because vehicles share their verification results with each other in a cooperative way, the number of safety messages that each vehicle needs to verify will be reduced greatly.

A new research issue of the protocol is how to select verifiers in the city road scenario. Thus, we propose three verifiers selection algorithms, n-nearest method, most-even distributed method and the compound method for the CMAP. Performance metrics are utilized in the simulations for performance comparison.

  1. Packet arrival rate

The ratio of the number of received data packets to the number of total data packets sent by the source.

  1. Energy consumption

The energy consumption for the entire network includes transmission energy consumption for both the data and control packets.

  1. Average end-to-end delay

The average time elapsed for delivering a data packet within a successful transmission.

  1. Control overhead

The average number of transmitted control bytes per second, including both the data packet header and the control packets.

  1. Collision rate

The average Collision rate for the entire data transmission from source to destination is much controlled and reduced when compared to the existing protocol.


ECDSA is Elliptic Curve Cryptosystem (ECC)-based implementation of the commonly used digital signature algorithm. ECC provides the same security level as the other discrete logarithm approaches, while the size of the required ECC credentials is much smaller than that of the discrete logarithm systems. The WAVE security service adopt ECDSA-based message authentication for vehicular communications. Two standard elliptic curves namely P-224 and P-256 have been suggested for general purpose message authentications, and certificate authentications in VANETs.

A VANET entity is required to transmit periodic safety messages containing its current coordinates, speed, acceleration etc. to the neighboring devices. The typical interval for safety message broadcasts ranges from 100 ms to 300 ms. An authentication scheme has to be incorporated in order to provide reliability and trust for the delivered safety information.

Received messages are verified by the receiving entity to ensure the message integrity, and authenticity of sender’s identity. Unfortunately signature verification incurs a cryptographic processing delay at the verifier’s end. Although the verification delay for ECDSA is in the order of milliseconds, with hundreds of vehicles in a dense traffic scenario, an OBU would receive an enormous amount of periodic messages per unit time causing a bottleneck to the authentication process at the receiver end.

If OBUs are configured to broadcast their periodic messages every 100 ms, under a heavy traffic scenario, many of the safety messages would either be discarded due to the constrained buffer size of the verification process, or accepted without any verification.

Therefore in busy traffic hours, a receiver of vehicular messages would either risk a fatal road-traffic consequence, or it would reject a significant portion of received messages without authenticating when its maximum verification capacity is reached. The current WAVE standards do not include an efficient anonymous authentication scheme for vehicular messages, or even an intelligent authentication strategy which can efficiently verify from a massive number of vehicular safety/application messages.


The proposed protocol designed an identity-based anonymous user-authentication scheme and a cross-layer verification approach for WAVE-enabled VANET’s safety messages. A variation of the conventional ECDSA approach is used with the identity-based signature approach where the common geographical area information of signing vehicles is taken as the signer’s identity. This exempts a vehicle from the mandatory inclusion of a trusted third-party certificate with each broadcast message in a VANET while a user is still identifiable by the trusted third-party up on a dispute. A cross-layer message verification scheme verifies the received messages based on their MAC traffic class and traffic intensity. This ensures that under the rush hour congestion or traffic accident most important messages will not be missed by the verifier. Security analysis and performance evaluation justify our authentication and verification approach for WAVE-enabled vehicular communications.


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