Vehicular Ad-Hoc Networks

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Congestion Control in Vehicular Ad Hoc Networks

Congestion Control in Vehicular Ad Hoc Networks

Mobile Computing and Networking Research Laboratory (LARIM), Department of Computer Engineering, Polytechnique de Montréal, Montreal, Canada Abstract Vehicular Ad Hoc Networks (VANets) is considered as a technology which can increase safety and convenience of drivers and passenger. Due to channel congestion in high density situation, VANets’ safety applications suffer of performance degradation. In order to improve performance, reliability, and safety over VANets, congestion control should be taken into account. However, congestion control is a challenging task due to the special characteristics of VANets (e.g. high mobility, high rate of topology change, frequently route break, and so on). In this paper, DySch and TaSch strategies are proposed. Those strategies assign priorities to the safety and service messages based on the content of messages (static factor), state of network (dynamic factor) and size of messages. DySch and TaSch strategies schedule the messages dynamically and heuristically, respectively. Their performance is investigated using highway and urban scenarios while the average delay, average throughput, number of packet loss, packet loss ratio, and waiting delay in queues are considered. Simulation results show that DySch and TaSch strategies can significantly improve the performance of VANets in comparison to the best conventional strategies. Employing the proposed strategies to control congestion in VANets helps increase reliability and safety by giving higher priority to the safety messages.
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Reverse back-off mechanism for safety vehicular ad hoc networks

Reverse back-off mechanism for safety vehicular ad hoc networks

b Université de Toulouse, INP Toulouse, ENSEEIHT, IRIT IRT, 31000, Toulouse, France a b s t r a c t Vehicular ad hoc networks can play an important role in enhancing transportation effi- ciency and improving road safety. Therefore, direct vehicle-to-vehicle communications are considered as one of the main building blocks of a future Intelligent Transportation Sys- tem. The success and availability of IEEE 802.11 radios made this technology the most probable choice for the medium access control layer in vehicular networks. However, IEEE 802.11 was originally designed in a wireless local area network context and it is not opti- mised for a dynamic, ad hoc vehicular scenario. In this paper, we investigate the compat- ibility of the IEEE 802.11 medium access control protocol with the requirements of safety vehicular applications. As the protocols in this family are well-known for their scalability problems, we are especially interested in high density scenarios, quite frequent on today’s roads. Using an analytical framework, we study the performance of the back-off mecha- nism and the role of the contention window on the control channel of a vehicular network. Based on these findings, we propose a reverse back-off mechanism, specifically designed with road safety applications in mind. Extensive simulations are carried out to prove the efficiency of the proposed enhancement scheme and to better understand the characteris- tics of vehicular communications.
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Request Answering in Vehicular Ad-Hoc Networks Based on Adaptive Filters

Request Answering in Vehicular Ad-Hoc Networks Based on Adaptive Filters

Abstract—Vehicles in urban city are equipped with more and more sensing units, which brings about great potentials to the intelligent and green city traffic management. In this paper we propose a filter-based framework called FERA (Filter-based Efficient Request Answering) that combines the concept of fog computing and vehicular sensing. FERA combines the pull/push strategies to adaptively and efficiently gather the requested data in vehicular ad hoc networks. Filters are adopted to control the passage or blockage of the data readings, and requests are directed down to edge nodes or ordinary nodes to further search the requested data. FERA sets and adjusts filters according to their ratio of cost between the push and the pull methods, which effectively pushes the matched data readings upward and blocks the unmatched data readings, saving a large number of message transmissions. Experiments based on real-world road network demonstrate the effectiveness of the proposed scheme in vehicular sensing applications. Up to 85% of the requests could be successfully processed in the proposed scheme, which is better than existing schemes while at the same time with a relatively low transmission cost.
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TDMA scheduling strategies for vehicular ad hoc networks: from a distributed to a centralized approach

TDMA scheduling strategies for vehicular ad hoc networks: from a distributed to a centralized approach

I. I NTRODUCTION AND MOTIVATION Vehicular Ad hoc NETworks, known as VANETs, are a promising communication technology that can meet various requirements of Intelligent Transportation System (ITS) applications which aim to improve traffic safety and efficiency [1]. Through Vehicle-to-Vehicle (V2V) and Vehicle-to- Infrastructure (V2I) communications, each vehicle can exchange information to warn other vehicles about the cur- rent state of the traffic flow or the existence of a potentially dangerous situation such as an accident. Road safety and traffic management applications require a reliable broadcast scheme with minimal transmission delays and collisions, which increases the need for an efficient MAC protocol [2].Recently, Contention-free MAC protocols, notably those that are based on the TDMA technique, have attracted a lot of attention and many protocols have been proposed in the
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Network parameters impact on dynamic transmission power control in vehicular ad hoc networks

Network parameters impact on dynamic transmission power control in vehicular ad hoc networks

Abstract In vehicular ad hoc networks, the dynamic change in transmission power is very effective to increase the throughput of the wireless vehicular network and decrease the delay of the message communication between vehicular nodes on the highway. Whenever an event occurs on the highway, the reliability of the communication in the vehicular network becomes so vital so that event created messages should reach to all the moving network nodes. It becomes necessary that there should be no interference from outside of the network and all the neighbor nodes should lie in the transmission range of the reference vehicular node. Transmission range is directly proportional to the transmission power the moving node. If the transmission power will be high, the interference increases that can cause higher delay in message reception at receiver end, hence the performance of the network decreased. In this paper, it is analyzed that how transmission power can be controlled by considering other different parameter of the network such as; density, distance between moving nodes, different types of messages dissemination with their priority, selection of an antenna also affects on the transmission power. The dynamic control of transmission power in VANET serves also for the optimization of the resources where it needs, can be decreased and increased depending on the circumstances of the network. Different applications and events of different types also cause changes in transmission power to enhance the reachability. The analysis in this paper is comprised of density, distance with single hop and multi hop message broadcasting based dynamic transmission power control as well as antenna selection and applications based. Some summarized tables are produced according to the respective parameters of the vehicular network. At the end some valuable observations are made and discussed in detail. This paper concludes with a grand summary of all the protocols discussed in it.
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A Novel Angle-based Clustering Algorithm for Vehicular Ad Hoc Networks

A Novel Angle-based Clustering Algorithm for Vehicular Ad Hoc Networks

Keywords—VANET, Cluster Protocol, Ad hoc Networks, Mobil- ity Direction, Angle . I. I NTRODUCTION AND MOTIVATION Vehicle-to-Vehicle technology provides communication be- tween vehicles through an ad hoc wireless network and elim- inates the need for a central station to control the network topology. These vehicular ad hoc networks (VANETs) are characterized by the self-organization of the nodes and rapid changes in network topology due to the high speed of the vehicles. As breaks in communication links frequently occur in VANETs, ensuring communication stability is more difficult in VANETs than in standard MANETs. An effective and cheap solution to reduce the impact of mobility and improve the VANET network connectivity consists in establishing a hierarchical clustering structure within the network.
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A Fully Distributed TDMA based MAC Protocol for Vehicular Ad Hoc Networks

A Fully Distributed TDMA based MAC Protocol for Vehicular Ad Hoc Networks

Abstract—The Vehicular Ad-Hoc NETwork (VANET) consists of a set of vehicles moving on roads which can communicate with each other through ad hoc wireless devices. VANET has attracted a lot of attention in the research community in recent years with the main focus on its safety applications. One of the challenges for vehicular network is the design of an efficient Medium Access Control (MAC) protocol due to the hidden node problem, the high speed of the nodes, the frequent changes in topology, the lack of an infrastructure, and various QoS requirements. Motivated by this observation, we design a fully distributed and location- based TDMA scheduling scheme for VANETs networks, named DTMAC. The main goal of this work is to propose a MAC protocol that can provide fairness in accessing the transmission medium, as well as reduce access collision and merging collision under various conditions of vehicular density without having to use expensive spectrum and complex mechanisms such as CDMA or OFDMA. An analytical model of the average access collision probability and throughput are derived which can be used to evaluate the performance of DTMAC protocol as well as to validate the simulation results under different traffic conditions.
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Using Road IDs to Enhance Clustering in Vehicular Ad hoc Networks

Using Road IDs to Enhance Clustering in Vehicular Ad hoc Networks

Keywords—VANET, MANET, Clustering, GPS, MAP, Road ID. I. I NTRODUCTION Research on Vehicular Ad hoc Networks (VANETs) has attracted increasing interest over recent years due to its ca- pability to improve road safety by using Vehicle To Vehicle (V2V) and/or Vehicle To Infrastructure (V2I) communications [1]. It can also be used to improve traffic management con- ditions and to provide on-board infotainment such as Internet access, video streaming, etc. VANETs are characterized by the self-organization of the nodes, where their nodes can be vehicles, roadside units or sensors. Due to the varying vehicular densities caused by high vehicle mobility, supporting network connection requires a high communication overhead for exchanging and updating topology information. For in- stance, in a fully distributed VANET, each vehicle is required to maintain its own connectivity to its one hop neighboring vehicles. Without using expensive components such as central points, establishing a hierarchical clustering structure within the network can reduce the relative mobility between neigh- boring vehicles, thereby reducing communication overhead [2]. Clustering allows the formation of organized groups and is used to coordinate channel access, simplify routing, and security. In VANETs, each vehicle is equipped with a digital road map and a positioning system, e.g. Garmin Nuvi 50 GPS that allows it to obtain the time, its speed and position [3] and the ID of the road on which it is traveling. Therefore a clustering protocol for VANET network can be designed
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Fault tolerant time synchronization using offsets table robust broadcasting protocol for vehicular ad hoc networks

Fault tolerant time synchronization using offsets table robust broadcasting protocol for vehicular ad hoc networks

Fault-tolerant time synchronization Offset table robust broadcasting a b s t r a c t The requirement of time synchronization emerged in distributed systems remains one of the most signif- icant issues that should be addressed to the extent of that systems evolve. As clock synchronization is important for any type of network, Vehicular Ad hoc networks (VANETs) are being considered for their basic communication platforms, but also for providing the ability to detect movement, location, proxim- ity, and other network capabilities. The intrinsic characteristics of VANETs like: the high speed of nodes and the lack of permanent network connectivity generated by an instable environment, which make communication difficult or temporarily impossible, have created new challenges. These challenges make solutions that have been already proposed for classical networks no longer appropriate. Therefore, to overcome this deficiency, new and adaptive clock synchronization mechanisms should be devised and implemented, dealing so with communication and scalability issues. In this paper, we propose ‘‘Offsets Table Robust Broadcasting” (OTRB) algorithm. In this algorithm, instead to each node communicates with its vicinity, a set of nodes is selected to spread the time information over the entire network. The pro- posed time synchronization protocol is well-adapted to random network topology changes, high nodal velocity while offering good precision and robustness against nodal failure and packet loss. The analytical study and protocol simulation for evaluating the system performance, carried out by a combination of VanetMobiSim and NS2 simulators, have yielded convincing results, outperforming those exhibited by the basic referred protocols.
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Reverse back-off mechanism for safety vehicular ad hoc networks

Reverse back-off mechanism for safety vehicular ad hoc networks

a b s t r a c t Vehicular ad hoc networks can play an important role in enhancing transportation effi- ciency and improving road safety. Therefore, direct vehicle-to-vehicle communications are considered as one of the main building blocks of a future Intelligent Transportation Sys- tem. The success and availability of IEEE 802.11 radios made this technology the most probable choice for the medium access control layer in vehicular networks. However, IEEE 802.11 was originally designed in a wireless local area network context and it is not opti- mised for a dynamic, ad hoc vehicular scenario. In this paper, we investigate the compat- ibility of the IEEE 802.11 medium access control protocol with the requirements of safety vehicular applications. As the protocols in this family are well-known for their scalability problems, we are especially interested in high density scenarios, quite frequent on today’s roads. Using an analytical framework, we study the performance of the back-off mecha- nism and the role of the contention window on the control channel of a vehicular network. Based on these findings, we propose a reverse back-off mechanism, specifically designed with road safety applications in mind. Extensive simulations are carried out to prove the efficiency of the proposed enhancement scheme and to better understand the characteris- tics of vehicular communications.
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TDMA-aware Routing Protocol for Multi-hop Communications in Vehicular Ad Hoc Networks

TDMA-aware Routing Protocol for Multi-hop Communications in Vehicular Ad Hoc Networks

‡ RAMSIS Team, CRISTAL Laboratory, 2010 Campus University, Manouba, Tunisia {mohamed.hadded, anis.laouiti}@telecom-sudparis.eu, paul.muhlethaler@inria.fr, leila.saidane@ensi.rnu.tn Abstract—Vehicular Ad-Hoc Networks (VANETs) have be- come an emerging technology due to the variety of their appli- cations in Intelligent Transportation Systems (ITS). By creating a vehicular network, each vehicle can exchange information to inform drivers in other vehicles about the current status of the traffic flow or a dangerous situation. Multi-hop communications is an effective method that can be used for information exchange over distances greater than the transmission range of the transmitting vehicle. However, it is a great challenge to ensure a stable multi-hop communication link with a low delivery delay due to the high mobility of the vehicles involved. The goal of this paper is to design a TDMA aware Routing Protocol for Multi-hop wireless vehicular ad hoc networks (TRPM) in order to provide the ability to transmit/receive packets over long distances. The proposed routing scheme is based on a medium access control protocol, in which the intermediate vehicles are selected based on the TDMA scheduling. The simulation results reveal that our routing protocol significantly outperforms other protocols in terms of average end-to-end delay, average number of relay vehicles and the average delivery ratio.
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A Survey on Vehicular Ad-Hoc Networks Routing Protocols: Classification and Challenges

A Survey on Vehicular Ad-Hoc Networks Routing Protocols: Classification and Challenges

The routing of the Topology-based approach utilizes the link information about the network nodes to forward the data packets. The approach suffers from routing route breaks because of the regular basis changes in the infor- mation about links. Despite its good property of providing low latency for real-time applications, the maintenance of unused paths occupies a significant part of the bandwidth in a highly mobile network. Since they provide a very low communication throughput, the proactive algorithms are not suitable in VANETs. Unlike to proactive routing proto- cols, in an on-demand routing protocol, the routing traffic floods the network only when a route is required. Thus, the nodes in the network exchange no regular routing up- dates. However, the delay generated by the route discov- ery process in finding a route is an issue for vehicular communication especially real-time applications. In addition, the scalability issue is another concern of the approach since the reactive routing protocols are still con- sidered in small-scale networks with a path of a few hops. AODV and DSR are designed for general purpose mobile ad hoc networks and do not maintain routes unless they are needed. Hence, they can reduce overhead, especially in scenarios with a small number of network flows. Thus, certain modification of the ad hoc routing protocols that have been developed to deal with highly dynamic mobility of nodes in the context of VANETs or new routing proto- cols needed to be developed since many of them do not apply well to VANETs. The advantages’ reactive proto- cols are that they offer greater adaptability to the topo- logical changes of highly mobile ad hoc network such as VANET. However, these types use a flooding method for route discovery that initiates more overhead and suffers from the initial route discovery method. Thus, they be- come inadequate for security applications.
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A Centralized TDMA based Scheduling Algorithm for Real-Time Communications in Vehicular Ad Hoc Networks

A Centralized TDMA based Scheduling Algorithm for Real-Time Communications in Vehicular Ad Hoc Networks

creasing, Vehicular Ad hoc NETworks (VANETs) are becoming a promising way to enhance driver and passenger safety by enabling each vehicle to provide a warning in real time when a critical event is predicted. These applications require reliable broadcast schemes with minimum access delay and transmission collisions, which thus increase the need for an efficient Medium Access Control (MAC) protocol. However, the design of an efficient MAC protocol in VANET networks is a challenging task due to the high speed of the nodes, the frequent changes in network topology and various QoS requirements. Motivated by this observation, in this paper we present a Centralized TDMA based MAC protocol named CTMAC for real-time communica- tions in VANETs. In our solution, Road Side Units (RSUs) are used as central coordinators to schedule and maintain time slot assignment for the vehicles in their coverage areas. In this work, we will show how interference between vehicles in the overlapping regions can be avoided without using any complex spectrum mechanisms such as CDMA or OFDMA. The simulation results reveal that CTMAC significantly outperforms the VeMAC and ADHOC MAC protocols. in terms of transmission collisions and the overhead required to create and maintain the TDMA schedules.
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Authentication and consensus overhead in vehicular ad hoc networks

Authentication and consensus overhead in vehicular ad hoc networks

Authentication and consensus overhead in vehicular ad hoc networks Jonathan Petit · Zoubir Mammeri Abstract Vehicular ad hoc networks aim at increasing pas- senger safety by exchanging warning messages between ve- hicles wirelessly. A main challenge is to resist to various malicious abuses and security attacks. However, any secu- rity mechanism comes with overhead. We analyze how the authentication algorithm ECDSA and the consensus mech- anism impact the vehicular network performance and the braking distance. Processing and communication overheads, decision methods for consensus, are analyzed by analytical models and intensive simulations. We propose a formula to assess the total time overhead of the authentication. Results conclude that the authentication key size should be chosen carefully, and the decision method should be adapted to the context.
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Authentication and consensus overhead in vehicular ad hoc networks

Authentication and consensus overhead in vehicular ad hoc networks

9 Conclusion and future work VANETs deployment has the potential to greatly increase vehicular safety and improve driving experience. But, ve- hicular communications need to be secured. Therefore, the DSRC standard for vehicular ad hoc networks is based on the ECDSA algorithm for supporting authentication mecha- nism. But, security mechanisms come with overheads that affect the performance of the V2V communications, and hence that of the safety applications. In this paper, we inves- tigate the total overhead of ECDSA, combining the packet size, processing and communication overheads. We focus on safety applications, and analyze the impact of the au- thentication on the braking distance. We conduct simulation study in order to evaluate the performance of secured beacon safety message dissemination in vehicular ad hoc networks. We pay special attention to safety requirements while study- ing networking performance issues.
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Network parameters impact on dynamic transmission power control in vehicular ad hoc networks

Network parameters impact on dynamic transmission power control in vehicular ad hoc networks

to the needs of the vehicular network that has a dynamic topology as well, so many problems described could be overcome. In vehicular ad hoc networks, the dynamic change in transmission power is very effective to increase the throughput of the network and decrease the delay of the communication. Whenever an event occurs, the reliability of the communication from vehicular node to other vehicular nodes becomes so vital so that event messages should reach to these nodes. More importantly, the connectivity between the moving nodes comes first to achieve the reliability in the network. There is a direct relation between the connectivity and the transmission power, less transmission power means that connectivity between the moving nodes is weak and vice versa. This paper analyzes that how transmission power can be controlled by considering different parameter of the network such as; density, distance between moving nodes, information message priority etc. Optimization of the network could also be met by the dynamic control of transmission power in VANET; where it needs, transmission power can be decreased and increased depending on the circumstances of the network. Transmission range theoretically in DSRC standard is 1000 meter and the data rate can change from 6 Mbps to 27 Mbps. Transmission power versus transmission range is also calibrated in [12]. In the summarized tables some symbols are used to describe the behavior of the parameters of the network. Plus sign ‘++’ shows the increasing and minus sign ‘−−’ show the decreasing or degrading behavior, ‘±’ describes the dynamic changing (increasing and decreasing) behaviors, the equal sign ‘==’ indicates that there is no change; neither increasing nor decreasing.
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Congestion Control in Vehicular Ad Hoc Networks

Congestion Control in Vehicular Ad Hoc Networks

Space Division Multiple Access (SDMA) is a complement for any channel access technique and it has been designed in the context of vehicular networks by Bana and Varaiya [BV01]. The idea behind SDMA is that, if position information is available at every node, the resources (slots, codes, channels, etc.), also called cells, can be assigned depending on the geographical location of the nodes, in order to maximise the distance between two zones using the same resource. Although SDMA is theoretically the best access method in a mobile ad-hoc network, it has to face three major problems. First of all, every node must have very accurate location information, at the level of a road lane. This is very important, because even a small error might result in the assignment of a wrong cell, most probably belonging to a very close neighbour. The current GPS system used in vehicles cannot provide the required precision. The second problem comes from the fact that resources are reserved even for unoccupied locations. Finally, the third issue is related to the one-to-one mapping that is necessary between cells and the road topology, which can be a very difficult task for roads with irregular shapes, as for example highway entries.
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TDMA-based MAC Protocols for Vehicular Ad Hoc Networks: A Survey, Qualitative Analysis and Open Research Issues

TDMA-based MAC Protocols for Vehicular Ad Hoc Networks: A Survey, Qualitative Analysis and Open Research Issues

Mohamed Hadded, Paul Muhlethaler, Anis Laouiti, Rachid Zagrouba, Leila Azouz Saidane Abstract—Vehicular Ad-hoc NETworks (VANETs) have attracted a lot of attention in the research community in recent years due to their promising applications. VANETs help improve traffic safety and efficiency. Each vehicle can exchange information to inform other vehicles about the current status of the traffic flow or a dangerous situation such as an accident. Road safety and traffic management applications require a reliable communication scheme with minimal transmission collisions, which thus increase the need for an efficient Medium Access Control (MAC) protocol. However, the design of the MAC in a vehicular network is a challenging task due to the high speed of the nodes, the frequent changes in topology, the lack of an infrastructure, and various QoS requirements. Recently several Time Division Multiple Access (TDMA)-based medium access control protocols have been proposed for VANETs in an attempt to ensure that all the vehicles have enough time to send safety messages without collisions and to reduce the end-to-end delay and the packet loss ratio. In this paper, we identify the reasons for using the collision-free medium access control paradigm in VANETs. We then present a novel topology-based classification and we provide an overview of TDMA-based MAC protocols that have been proposed for VANETs. We focus on the characteristics of these protocols, as well as on their benefits and limitations. Finally, we give a qualitative comparison, and we discuss some open issues that need to be tackled in future studies in order to improve the performance of TDMA-based MAC protocols for vehicle to vehicle (V2V) communications.
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An Infrastructure-Free Slot Assignment Algorithm for Reliable Broadcast of Periodic Messages in Vehicular Ad hoc Networks

An Infrastructure-Free Slot Assignment Algorithm for Reliable Broadcast of Periodic Messages in Vehicular Ad hoc Networks

in ATSA, when a vehicle accesses the network, it chooses a frame length and competes for one of the time slots available for its direction. Moreover, the frame length is dynamically doubled or shortened based on the binary tree algorithm, and the ratio of two slot sets is adjusted to decrease the probability of transmission collisions. Dang et al. [12] developed and evaluated a Hybrid Efficient and Reliable MAC for Vehicular Ad hoc Networks, called HER-MAC, which is similar to the DMMAC protocol. The goal of this research work is to develop a contention-free Multichannel MAC protocol with an adaptive broadcasting algorithm, which improves data transfer rates for non-safety applications while guaranteeing timely delivery for safety applications in highway scenarios. The architecture and the operation of HER-MAC are similar to DMMAC, differing in that the CRP period is used by a vehicle to reserve a time slot during the ABF period or to exchange a 3-way WSA/RFS (WAVE Service Announcement/Request For Service) handshake. In fact, if a vehicle wishes to exchange non-safety messages, it has to broadcast the WSA during the CRP period to reserve a time slot on a certain SCH. Then, when a vehicle decides to use the service, it sends the RFS to the service provider which will confirm it with an ACK message. On receiving the ACK packet, the vehicles can start exchanging non-safety messages without any risk of collisions
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Broadcast-based Directional Routing in Vehicular Ad-Hoc Networks

Broadcast-based Directional Routing in Vehicular Ad-Hoc Networks

Vehicular ad hoc networks have been essentially developed to enhance driver safety. We believe that to efficiently implement this kind of systems a major problem needs to be solved: ”how to rapidly disseminate the information among the vehicles?”. At the wireless link level, a step has been already made in the 802.11 standard [15] by accelerating the link setup (the IEEE 802.11p removes the need of association between stations before communicating). At the network level, one method that is considered to be very effective is broadcast. It is a technique that does not require a prior end-to-end connection establishment or maintenance. It is cheap and simple in terms of deployment and gives good performance thus its popularity.
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