Communication In Vehicular Ad Hoc Networks Research Articles

Impact of co-channel interference on the performance of VANETs under [formula omitted] fading

Vehicular Ad hoc Networks (VANETs) are considered to be a novel solution for provisioning of infotainment services and reduction of accidents on the road. However, communication in VANETs is significantly hampered by multipath fading and co-channel interference. In this context, we analytically model VANETs based on the well-known cluster model. The closed form expression for packet error probability is derived in the presence of co-channel interference under α-μ fading. Impact of α and μ on interference is also characterized in detail. We also incorporate the impact of channel estimation errors of main and interfering link to provide more realistic evaluation of packet error probability. We then provide performance evaluation of VANETs under cooperative communication and quantify the improvements in the performance of cluster. We also evaluate the importance of fading parameters α and μ in the presence of interfering signal from nearby cluster. Our findings disclose that an error floor is introduced at high signal-to-noise-ratio (SNR) due to imperfect channel estimation. Additionally, the error probability considerably reduces by applying cooperative scheduling. Extensive simulations are performed in MATLAB to validate our results, which also prove the practicality of our analytical model.

Selective MAC for Obstacle Aware CEV Environmental Model for V2V

<p><span style="font-size: small;">Vehicular adhoc network (VANET) adopts or resembles a similar structure of Mobile adhoc network (MANET).</span><span style="font-size: small;"> </span><span style="font-size: small;">The communication in VANET are generally classified into following three categories such as Vehicle to Infrastructure (V2I), Vehicle to Vehicle (V2V) and Hybrid network which is a combination of V2V and V2I network. VANET using the IEEE 802.11p standard has great potential of achieving objectives of Smart intelligent transport system (SITS) for improving transport and road safety efficiency. As more and more services is been provided for V2V based VANET network. It is a challenging task to provide QoS to end user, due to wireless medium that has limited channel availability for transmission. To guarantee QoS and provide efficient network performance, a prioritized MAC need to be designed. Many priority based MAC has been designed in recent times to improve the quality of data delivery to end user. However these do not consider the impact of environment and presence of obstacle which affects the signal attenuation at the receiver end and affecting the QoS of channel availability. To address, this work present an obstacle based radio propagation model, obstacle based CEV (City, Expressway and Village) environmental model and a selective MAC to provide QoS for different services. The proposed model efficiency is evaluated in term of throughput achieved per channel, Collison and success packet transmission. To evaluate the adaptive performance of proposed AMACexperiment are conducted under CEV environment and are compared with existing MAC NCCMA. The outcome achieved shows that the proposed model is efficient in term of reducing Collison, improving packet transmission and throughput performance considering two types of services.</span></p>

Trusted and Secured Routing Protocol for Vehicular Ad-Hoc Networks

Objectives: To establish a trust based secured routing protocol to accurately distinguish malicious nodes that are dropping the important information and modifying the routes. Efforts are made to identify malicious nodes such as route modifiers and packet droppers. Methods/Statistical Analysis: Vehicular Ad-hoc NETworks (VANETs) is a modern technology which help a vehicle and a driver in several ways. The main characteristics of VANETs are nodes i.e. vehicles with relatively high mobility and constantly changing topology. In case of data communication in VANETs, a source node must depend on the intermediate nodes to send its data packets to the destination node on multi-hop routes. VANETs can give better performance if all its nodes work properly with full cooperation during the communication. In VANETs, a node can generate and broadcast important and essential messages to other nodes in the network for safety reason. However, the generated message by a vehicle may not be reliable every time. In this paper we have proposed a trusted and secured routing protocol that evaluates the trust of a vehicle and also checks the message reliability. The proposed protocol is named as Trusted Vehicular Ad-hoc On-demand Distance Vector (TVAODV) routing protocol which is the modification of Ad-hoc On-demand Distance Vector routing protocol. Since VANETs are mostly attacked by the malicious nodes; therefore better security solution is needed to stop such attacks. The proposed protocol introduces a trust model to establish a malicious node free route for source node to send its data packets to the destination node on multi-hop routes. Findings: The TVAODV protocol is simulated in Network Simulator (NS2) to check the performance and accuracy and also compared to AODV routing protocol. It is found that TVAODV is comparatively better in performance when VANET is in high mobility and versatile topology. The performance of the proposed protocol is evaluated using performance measurement metrics: average end-to-end delay, throughput, routing load and packet delivery ratio. The proposed protocol performance is evaluated in the presence of malicious (route modifiers and packet droppers) vehicles and the results shows that the proposed protocol is achieved better accuracy and it shows better performance compared to AODV routing protocol. Application/Improvements: The proposed protocol may be useful in the process of developing a better traffic management and transportation system. In this paper we have proposed a TVAODV routing protocol which includes trust model to evaluate the trust of vehicles as well as to establish a malicious free route.

A new cooperative communication algorithm for improving connectivity in the event of network failure in VANETs

Communication in Vehicular Ad-Hoc Networks (VANETs) is frequently disrupted by high mobility of nodes, obstacles, and interference-prone links. The communication link between nodes can be maintained using cooperative communication techniques where nodes collaborate with one another to increase the network performance. Implementation of cooperative communication, which requires helpful nodes to collaborate with others, is a difficult task in VANETs due to their inherent characteristics. Selection of a cooperative node which will help during the retransmission process is the most crucial work in the cooperative communication process considering the dynamic nature of nodes. In this study, we formulate a game-theoretic relay selection protocol for MAC-level retransmission, where every node plans to maximize their received incentives, which is determined by an incentive function. Therefore, cooperative neighboring nodes form tree structures to the destination node from transmitter node by using the proposed algorithm, NGOMA. The distributed incentive function stores promiscuous packets in nodes and forms a tree architecture with cooperative nodes to relay messages to the recipient node from the source node in times of packet-loss events. The network formed by the NGOMA protocol by the source and destination node with relay nodes, converges into a Nash network. Numerical results show that NGOMA, which allows nodes to cooperatively store and transmit lost packets to the recipients, reduces the MAC-level retransmission delay by 63% compared to a non-cooperative function, which does not cooperatively relay messages.

Novel Communication Protocol for the EV Charging/Discharging Service Based on VANETs

In this paper, we take advantage of the communication systems which will be adopted for the new vehicle generations in near future and we propose a new electric vehicle (EV) charge/discharge service scheme for large EV density through vehicular ad-hoc networks communications. First, we present a communication protocol for the EV charging/discharging protocol with the uplink and the downlink EV charge /discharge frame format exchanged between EVs and smart grid. Second, we propose our channel access scheme based on a distributed time slot assignment model (DTSA) to allow the EV charging/discharging service negotiations with smart grid before plug-in phase. This DTSA scheme, which is a contention-free channel access mechanism, can improve the EV charging/discharging service access by increasing the successful rate of channel reservation both on control channel (CCH) and service channel (SCH). We propose also three algorithms to manage the EV charge/discharge service reservation and negotiation, respectively, on CCH and SCH. Finally, extensive simulations with NS-2 and MATLAB are conducted to validate the proposed approach and demonstrate the efficiency and effectiveness of the proposed compared to IEEE802.11p and VeMAC while satisfying the defined constraints.

Performance Evaluation for Non-DTN and DTN Geographic based Protocols for VANETS

Vehicular Ad-hoc Network (VANET) is still a recent topology in wireless networks. It is not far different from Mobile Ad-hoc Network (MANET) except VANET is making the benefits of vehicles instead of mobiles. However; the high speed of the vehicles, the rapidly change of VANET topology, and the city environment characteristics, has become today’s issues in terms of wireless communication using vehicles. Thus this type communication has become very famous as a field for researchers. There are two main types of VANET communications as categorized by many researchers, which are vehicle to vehicle (V2V) and vehicle to Infrastructure (V2I). In terms of routing protocols, there are so many protocols that could be used by VANET. However; these protocols are not capable enough to achieve the communication. There are two main types of routing protocols in VANET: VANET routing topology-based and routing position-based. In this current paper we will make an overview about both of them. However; our main focus is to make comparison of geographical-based routing protocols. For example, qualitative comparison of protocols that are used for packages’ carrying and forwarding such as some Delay Tolerant Network (DTN) and non-Delay Tolerant Network Non-DTN geographic routing protocols. Finally, each protocol has its own advantages and disadvantages. So it is important to have an idea about them because at least they will be as a guide lines for the readers to determine their own researches. Depends on this comparison it is observed that hybrid DTN and non-DTN will perform better since it will take the advantages of all DTN and non-DTN.

Rising Issues in VANET Communication and Security: A State of Art Survey

VANET (Vehicular Adhoc Network) has made an evolution in the transportation hi-tech system in most of the developed countries. VANET plays an important role in an intelligent transportation system (ITS). This paper gives an overall survey on the research in VANET security and communication. It also gives parameters considered by the previous researchers. After the survey, it considered the authentication and message forwarding issues required more research. Authentication is first line of security in VANET; it avoids attacks made by the malicious nodes. Previous research has come up with some Cryptographic, Trust based, Id based, and Group signature based authentication schemes. Speed of authentication and privacy preservation are the important parameters in VANET authentication. This paper presented the AECC (Adaptive Elliptic Curve Cryptography), and EECC (Enhanced Elliptic Curve Cryptography) schemes to improve the speed and security of authentication. In AECC, the key size is adaptive, i.e. different sizes of keys are generated during the key generation phase. Three ranges are specified for key sizes: small, large, and medium. In EECC, added an extra parameter during the transmission of information from, the vehicle to the RSU for key generation. This additional parameter gives the information about the vehicle ID, and the location of the vehicle to the RSU and the other vehicle. Under the communication issue of VANET, the paper gives priority based message forwarding for improving the message forwarding scheme. It handles emergency situations more effectively.

On channel estimation in vehicular networks

In vehicular ad hoc network (VANET), the accuracy of the channel estimation plays a key role toward obtaining considerable improvement to the physical layer performance. In this study, least square (LS) and minimum mean square error (MMSE) estimation techniques are discussed and their performances in different VANET transmission scenarios are thoroughly investigated. Furthermore, a modified scheme of these techniques to improve the performance of the system and reduce the complexity in such a way that suits VANET communications is developed. Discreet Fourier transform and singular value decomposition techniques are companied with LS and MMSE to develop a channel estimation scheme which suits VANET channel conditions and ensures performance improvement and remarkable complexity reduction. Comprehensive simulations results show that the developed scheme greatly improves the performance of the system compared with LS and substantially reduces the complexity of MMSE.

An Empirical Study on the Temporal Structural Characteristics of VANETs on a Taxi GPS Dataset

In recent years, vehicular ad hoc networks (VANETs) have received significant interests from both academia and industry because of the ubiquitous communication capabilities they provide. VANETs are expected to support a wide range of applications that may influence our daily life, ranging from road safety applications to entertainment ones. A key to the development of protocols and algorithms for intervehicle communication and services lies in the knowledge of the structural properties of the VANET communication graph. Nonetheless, previous researches represented the VANET communication graph as a set of snapshots and tracked the evolution of some metrics on snapshots at certain time intervals. They neglected to take into account the temporal property of VANETs, which in many real scenarios plays a pivotal role. In this paper, we mainly explore the temporal structural characteristics of VANETs. A time-extended model is first presented to capture the temporal property of VANETs. Based on the model, some key metrics are defined to describe the structural characteristics of VANETs in various aspects. We then employ a real and large-scale urban taxi GPS dataset to provide a comprehensive study of the temporal structural characteristics involved with time-ordered paths, reachability, and connectivity of VANETs. These results are helpful in designing better protocols and algorithms to achieve reliable and low-latency communications.

Performance Study of MANET Routing Protocols in VANET

VANET (Vehicular Ad Hoc Network) is an evolving technology that brings numerous advantages, benefits and features of wireless networks to vehicles. VANET allows vehicles to communicate among themselves or with roadside equipment. Such kind of communication can be utilized for different purposes such as safety, comfort, or even entertainment. In VANET, routing of data, remains a challenging area for researchers due to its dynamic topology and the fast speed at which vehicles move. VANET is a sub class of MANET (Mobile Ad Hoc Network) with some distinct features. The performance of communication in VANET depends on the performance of its underlying network routing protocols. In this work, we performed simulation study to compare the most popular MANET routing protocols (namely: AODV, DSDV and DSR) for VANET by considering a real world scenario of a highway system. We used the famous NCTUns 6.0 network simulator for our comparative study. Numerous key simulation parameters have being considered which include speed, number of nodes, data rate, propagation model, fading and payload. The selected routing protocols were then evaluated in terms of important performance metrics which include throughput, packet drop, packet collision and average end to end delay. Our obtained simulation results show that the performance of the routing protocols depends largely on the application throughput, average delay and QoS (fewer packet drops).

An Efficient Multiple Session Key Establishment Scheme for VANET Group Integration

VANET (vehicular ad hoc network) is used to create communication networks for vehicles or other roadside devices so that they can quickly share and receive messages. However, VANET belongs to a family of wireless networks, which means that its functions are unsafe. To provide safe communication channels, key-agreements technology can be introduced to VANET communication. Traditional key-agreement schemes, however, are inefficient and consume too many resources, especially when handling large or combined groups of users. To improve efficiency, the Chinese remainder theorem is used to build a batch key-agreement protocol. The improved key for VANET environments is a safer and quicker way to establish communication channels.

Comprehensive survey on security services in vehicular ad‐hoc networks

Vehicular ad-hoc networks (VANETs) are the most hopeful approach to provide safety information and other infotainment applications to both drivers and passengers. VANETs are formed by intelligent vehicles equipped with On Board Units and wireless communication devices. Hence, VANETs become a key component of the intelligent transport system. Even though VANETs are used in enormous number of applications, there are many security challenges and issues that need to be overcome to make VANETs usable in practice. A great deal of study has been done towards it, but security mechanisms in VANETs are not effective. This study provides a summary about the VANET, characteristics and security challenges. This study also provides a summary of some major security attacks on security services such as availability, confidentiality, authentication, integrity and non-repudiation and the corresponding countermeasures to make VANET communications more secure.

Interference Issues for VANET Communications in the TVWS in Urban Environments

Within the scenario of the proliferation of smart vehicles, a novel tendency is to exploit the cooperation between vehicles to create vehicular ad hoc networks (VANETs) using the IEEE 802.11p standard. IEEE 802.11p includes dedicated short-range communications (DSRC) between high-speed vehicles and between the vehicles and the roadside infrastructure in the licensed intelligent transportation system (ITS) band at 5.9 GHz. At such frequencies, fading problems caused by the Doppler effect and/or multipath adversely affect propagation, particularly in dense urban environments. To reduce such propagation impairments, the use of lower frequencies has been proposed in literature, namely the TV white spaces (TVWS) in the ultrahigh-frequency (UHF) band. TVWS is the part of the spectrum licensed to broadcasters that is not occupied at a given time in a given geographical area on a noninterfering/nonprotected basis with regard to primary services. This paper analyses coexistence issues between digital video broadcasting—terrestrial (DVB-T)2 and IEEE 802.11p transmission in the TVWS. The aim of this paper is twofold: to evaluate the protection of DVB-T2 broadcasting services interfered by IEEE 802.11p communications and the impact of adjacent DVB-T2 services on IEEE 802.11p communications in the TVWS. The main outcomes of this paper are the maximum transmission power level and bandwidth configuration of an 802.11p signal in the adjacent channel (i.e., TVWS) of an active DVB-T2 system while protecting the broadcast service, as well as the error rate curves for each allowed mode of IEEE 802.11p in the TVWS to evaluate the performance of VANETs communications coexisting with DVB-T2 regular services in the licensed TV band.

Restricted usage of anonymous credentials in vehicular ad hoc networks for misbehavior detection

The automobile industry is entering a new era of digitalization with major impact on human mobility and transportation infrastructures. A result of such a convergence between the automobile and information technologies is vehicular ad hoc network (VANET), a type of mobile ad hoc networks that has recently enjoyed a lot of attention from the industry, the research community, lawmakers and privacy activists. In VANET, vehicles frequently broadcast various types of messages, including location data. This enables innovative applications and improvements in safety and driving experience. As messages broadcasted in the VANET are digitally signed and the receiver must be able to verify the sender's authentication and message integrity, there is a need to ensure broadcast authentication and protect driver's anonymity. However, communication in VANETs takes place with high frequency, and malicious vehicles can hide behind anonymity in order to duplicate packets and get advantage over other vehicles in the network. Indeed, state-of-the-art approaches to privacy-preserving messages broadcast in the VANET typically ensure that each vehicle has a number of pseudonymous certificates that are changed regularly in order to thwart an automated tracing of its activities. However, the possibility of uncontrolled simultaneous use of pseudonyms by misbehaving vehicles remain unaddressed. This paper proposes a set of anonymous credential system based protocols for VANET that enables the detection and limitation of pseudonym/credential overspending. The revocation of the misbehaving vehicle can be also achieved through the proposed solutions. With the prototypical implementation of the proposed protocols, it has been shown that the successful detection of fraud, i.e., pseudonyms overspending and the subsequent revocation of credentials are possible in VANET.

A Novel Real Time Framework for Cluster Based Multicast Communication in Vehicular Ad Hoc Networks

In a vehicular ad hoc network (VANET), the vehicles communicate with each other to develop an intelligent transport system (ITS) which provides safety and convenience while driving. The major challenge of VANET is that the topology changes dynamically due to the high speed and unpredictable mobility of vehicles resulting in an inefficient real time message dissemination, especially in emergency scenarios such as in the accident event where it can cause high level of destruction. To the best of our knowledge, there is no such mechanism in existing literature which can handle real time multicast communication in VANET for both urban and highway scenarios. In this paper, we propose a novel real time vehicular communication (RTVC) framework which consists of a VANET cluster scheme (VCS) and VANET multicast routing (VMR) to achieve efficient vehicle communication within both urban and highway scenarios. The RTVC framework develops stable communication links and achieves high throughput with low overhead despite high mobility by combining the multicast routing with a unique cluster based scheme. In VCS, the cluster head (CH) is elected upon cluster threshold value (CTV) to disseminate the messages within the cluster members (CMs) and to other cluster heads by intercluster communication, which reduces the network overhead. In addition, the vehicles cluster head election (VCHE) procedure is proposed to reduce the number of CHs and CMs switches which results in lower overhead of maintaining the clusters. Moreover, another novelty of the framework is that the CTV of VCHE can be adjusted by speed adjustment factor (SAF) to achieve the desired cluster stability depending upon the required VANET application. The simulation results illustrate that the proposed framework has achieved the goal of stable, efficient, and real time communication despite highly dynamic environment of VANET.

Modelling of Security Principles Within Car-to-Car Communications in Modern Cooperative Intelligent Transportation Systems

Intelligent transportation systems (ITS) bring advanced applications that provide innovative services for various transportation modes in the area of traffic control, and enable better awareness for different users. Communication connections between intelligent vehicles with the use of wireless communication standards, so called Vehicular Ad Hoc Networks (VANETs), require ensuring verification of validity of provided services as well as services related to transmission confidentiality and integrity. The goal of this paper is to analyze secure mechanisms utilised in VANET communication within Cooperative Intelligent Transportation Systems (C-ITS) with a focus on safety critical applications. The practical part of the contribution is dedicated to modelling of security properties of VANET networks via OPNET Modeler tool extended by the implementation of the OpenSSL library for authentication protocol realisation based on digital signature schemes. The designed models simulate a transmission of authorised alert messages in Car-to-Car communication for several traffic scenarios with recommended Elliptic Curve Integrated Encryption Scheme (ECIES). The obtained results of the throughput and delay in the simulated network are compared for secured and no-secured communications in dependence on the selected digital signature schemes and the number of mobile nodes. The OpenSSL library has also been utilised for the comparison of time demandingness of digital signature schemes based on RSA (Rivest Shamir Adleman), DSA (Digital Signature Algorithm) and ECDSA (Elliptic Curve Digital Signature Algorithm) for different key-lengths suitable for real time VANET communications for safety-critical applications of C-ITS.

2FLIP: A Two-Factor Lightweight Privacy-Preserving Authentication Scheme for VANET

Authentication in a vehicular ad-hoc network (VANET) requires not only secure and efficient authentication with privacy preservation but applicable flexibility to handle complicated transportation circumstances as well. In this paper, we proposed a Two-Factor LIghtweight Privacy-preserving authentication scheme (2FLIP) to enhance the security of VANET communication. 2FLIP employs the decentralized certificate authority (CA) and the biological-password-based two-factor authentication (2FA) to achieve the goals. Based on the decentralized CA, 2FLIP only requires several extremely lightweight hashing processes and a fast message-authentication-code operation for message signing and verification between vehicles. Compared with previous schemes, 2FLIP significantly reduces computation cost by 100–1000 times and decreases communication overhead by 55.24%–77.52%. Furthermore, any certificate revocation list (CRL)-related overhead on vehicles is avoided. 2FLIP makes the scheme resilient to denial-of-service attack in both computation and memory, which is caused by either deliberate invading behaviors or jammed traffic scenes. The proposed scheme provides strong privacy preservation that the adversaries can never succeed in tracing any vehicles, even with all RSUs compromised. Moreover, it achieves strong nonrepudiation that any biological anonym driver could be conditionally traced, even if he is not the only driver of the vehicle. Extensive simulations reveal that 2FLIP is feasible and has an outstanding performance of nearly 0-ms network delay and 0% packet-loss ratio, which are particularly appropriate for real-time emergency reporting applications.

AODV Routing Protocol Modification With Dqueue(dqAODV) and Optimization With Neural Network For VANET In City Scenario

Vehicular ad hoc network (VANET) is considered as a sub-set of mobile ad hoc network (MANET). VANET can provide road safety by generating collision warning messages before a collision takes place, lane change assistance; can provide efficient traffic system by introducing cooperation among vehicles; and can also improves in infotainment applications like cooperative file accessing, accessing internet, viewing movies etc. It provides smart Transportation System i.e., wireless ad-hoc communication among vehicles and vehicle to roadside equipments. VANET communication broadly distinguished in two types; 1) vehicle to vehicle interaction, 2) vehicle to infrastructure interaction. The main objective of VANET is to provide safe, secure and automated traffic system. For this automated traffic techniques, there are several types of routing protocols has been developed. MANET routing protocols are not equally applicable in VANET. In the recent past Roy and his group has proposed several study in VANET transmission in [1-3]. In this study, we propose a modified AODV routing protocol in the context of VANET with the help of dqueue introduction into the RREQ header. Recently Saha et al [4] has reported the results showing the nature of modified AODV obtained from the rudimentary version of their simulation code. It is mainly based on packet delivery throughput. It shows greater in-throughput information of packet transmission compare to original AODV. Hence our proposal has less overhead and greater performance routing algorithm compared to conventional AODV. In this study, we propose and implement in the NCTUns-6.0 simulator, the neural network based modified dqueue AODV (dqAODV) routing protocol considering Power, TTL, Node distance and Payload parameter to find the optimal route from the source station (vehicle) to the destination station in VANET communications. The detail simulation techniques with result and output will be presented in the conference.

Performance Analysis of Full-Duplex Cooperative Communication in Vehicular Ad-Hoc Networks

Abstract: This paper evaluates the use of full-duplex nodes to increase the performance of a vehicular ad hoc network (VANET) composed of one transmitter, multiple full-duplex relays and one destination, where the best relay is selected to assist communication. With the use of full-duplex communication, it is possible to obtain a better use of the radio resources, eliminating the multiplexing loss of half duplex systems. We consider Nakagami-m fading, aimed at analyzing the schemes in scenarios with line-of-sight and where the channel condition is critical, for instance a sub-Rayleigh channel, which are typical propagation scenarios to model vehicular networks. Furthermore, the analysis includes the self-interference at the relay node. Results presented in terms of outage probability shown that the full-duplex scheme is suitable for improving communication over vehicular channels.

Historical Spectrum Sensing Data Mining for Cognitive Radio Enabled Vehicular Ad-Hoc Networks

In vehicular ad-hoc network (VANET), the reliability of communication is associated with driving safety. However, research shows that the safety-message transmission in VANET may be congested under some urgent communication cases. More spectrum resource is an effective way to solve transmission congestion. Hence, we introduce cognitive radio (CR) enabled VANET (CR-VANET), where CR device can detect possible idle spectrum for VANET communications and assist to timely broadcast safety-message. Given high-speed mobility of vehicles and dynamically-changing availability of channels, a novel prediction algorithm is proposed to pick out the channel with the greatest probability of availability, which can meet the quality of service (QoS) requirement of urgent communications and effectively avoid conflict with licensed users. Specifically, the spatiotemporal correlations among historical spectrum sensing data are exploited to form prior knowledge of channel availability probability, and Bayesian inference is used to derive posterior probability of channel availability. Comparing with other spectrum detection methods, the proposed algorithm has more than 8 percent detection performance improvement at false alarm probability 0.2, and thus can avoid access conflict with licensed users dramatically. Furthermore, the proposed algorithm always has larger packet reception probability (PRP) and lower transmission delay compared with conventional VANET broadcasting. Hence, the proposed algorithm can improve reliability of safety-message transmission and enhance driving safety significantly.