will integrate this technology are police and fire vehicles to communicate with each other for safety purposes.

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1 IJEEE, Vol. 1, Issue 4 (August, 2014) e-issn: p-issn: SURVEY OVER VANET ROUTING PROTOCOLS FOR VEHICLE COMMUNICATION 1 Amanpreet Kaur, 2 Dr. Dinesh Arora 1,2 Gurukul Vidyapeeth Institute of Engineering & Technology, Banur, Punjab, India 1 amanprt344@gmail.com, 2 drdinesh169@gmail.com ABSTRACT: VANET (Vehicular Ad-hoc Network) is an appearing new technology with some distinctive characteristics that makes it unique from other ad-hoc networks. Due to rapidly changing the topologies and usually disconnection it is also difficult to design an effective routing protocol for routing the data between vehicles, called V2V or vehicle to vehicle communication and vehicle to road side infrastructure, called V2I. Because of road accident daily happening VANET is one of the impacting areas for the enhancing of Intelligent Transportation System (ITS) which can increase the road safety and give traffic information. The existing routing protocols for VANET are not systematic to meet every traffic framework. Suitable routing protocols are needed to establish communication among vehicles in future for road safety. In this paper, we emphasis the routing protocols which will help to produce new routing protocols or enhancement of existing routing protocol in near future. Keywords: VANET, Routing Protocol, Proactive, Reactive, MANET. I. INTRODUCTION A wireless ad hoc network is a decentralized type of wireless network. The network become ad hoc because it does not rely on a pre existing infrastructure, such as routers in the wired network or access points in managed wireless networks. Instead, each node participates in routing by forwarding data for other nodes, so the verification of which nodes forward data is made vigorously on the basis of network connectivity. In classic routing, ad hoc networks can use overflowing for forwarding data. An ad hoc network typically refers to some set of networks where all devices have equal status on a network and are free to associate with any other ad hoc network device in link range. Ad hoc networks are collection of self-regulating mobile nodes. VANET is the description of MANET. It includes V2V communications and V2I communications and is important component of OTS. Nodes are expected to communicate by means of North American DSRC standard that employs the IEEE 802.iip standard for wireless communication. VANET uses cars as mobile nodes in a MANET to create a mobile network. A VANET turns every participating cars into a wireless router or node, allowing cars approximately upto 300 meters of each other to connect and create a network with a vast range. As cars fall out of the signal range and drop out of the network, other cars can merge and connecting vehicle to one another so that a mobile internet is established. It is determined that the first systems that will integrate this technology are police and fire vehicles to communicate with each other for safety purposes. Various automotive firms promote this technology. VANET is one of the effecting areas for the refinement of Intelligent Transportation System (ITS) in sequence to provide safety and ease to the road users. VANET helps vehicles drivers to communicate and to synchronize between themselves in sequence to avoid some risky situation between vehicle to vehicle (V2V) communication for example vehicle accidents, traffic jams, control the speed of vehicles, free space available on road for emergency vehicles, unseen complications, breakdowns etc. In VANET safety applications also give the comfort applications for road users. The main applications of VANET for safety as Traffic Index, Vision Perfection, Weather Difficulty, Driver Assistance, Automatic Parking, Safety, Searching Roadside Locations and Vehicles Directions, Entertainment, ADASE2 (Advance Driver Assistance Systems), CAMP (Crash Avoidance Matrices Partnership), Fleet Net, CARTALK2000. In VANET mobile nodes act as cars or vehicles, their total mobility rate is also illustrate greater, and then the network become extremely dynamic. There are many protocols have been developed specially for VANET, focusing on various layers including Data Link Layer, Network Layer, Physical Layer. All these protocols have their own merits and demerits and tradeoffs. VANET behaving like MANET represent the objective of providing convenient communication between randomly formed collection of vehicles that are located in geo cast manner. Rapidly changing the topology of network and slowly changing communication situations are challenging conditions for routing protocols in VANET. But there protocols facing problems when the nodes are distributes over the network more elaborated and less systematic. The main advantage of the VANET is that the communication with rest of the world with the help of mobile. The disadvantage is that medium in open manner, limited memory space, limited bandwidth, limited processing power. In VANET, the vehicular nodes are connected that do not depend on the preexisting infrastructure to retain the network connected. Each vehicle supply with communication devices will be a node in the VANET and permit to receive and send the messages over the wireless communication channels. The function of the VANET mainly dependent on the certainty and coordination among the nodes. Each node in the network help to conveying the information related to the topology of the network and share the authority of managing the network. Hence each International Journal of Electrical & Electronics Engineering 1

2 node acting as hosts, each vehicular node perform the function of routing and transmission messages for other vehicular nodes. Vehicle to Vehicle Communication V2V communications for safety is the wireless exchange of data among vehicles travelling in the same vicinity that offers opportunities for significant safety improvements. V2V communications for safety is a key component of the connected vehicle research program within Intelligent Transportation Systems Joint Program Office (ITSJPO) of the U.S. Department of Transportation (USDOT) Research and Innovative Technology Administration (RITA). Through the multimodal program, the ITSJPO and the private sector are able to share information between vehicles to achieve transformative safety benefits for the multimodal transportation sector. V2V communication also known as car-to-car communication. Vehicle to Infrastructure Communication Vehicle-to-infrastructure communications for safety is the wireless exchange for critical safety and operational data between vehicles and highway substructure, intended primarily to avoid or diminish motor vehicle crashes but also to enable a wide range of distinct safety, strength, and environmental benefits. V2I conveyance apply to all vehicle types and all roads, and transform substructure equipment into smart infrastructure through the incorporation of algorithms that use data exchanged between vehicles and infrastructure elements to perform calculations that recognize high-risk situations in advance, resulting in driver alertness and warnings through specific counterbalance. The particularly important advancement is the ability for traffic signal systems to communicate the signal phase and timing (SPAT) information to the vehicle in support of delivering active safety advisories and warning to drivers. Early implementation of the SPAT application can enable near-term benefits from V2I communications in the form of reduced crashes, which in turn manifestation benefits that can help accelerate deployment. The V2I communication program is designed to enable exchange of data over a wireless network which enables each vehicle on-board equipment OBE), device (handheld multi-cellular devices, aftermarket moveable GPS devices), or roadside equipment (RSE) to perf orm calculations and issue driver advisories and warnings to avoid or mitigate crashes through specific advanced safety applications. With the help of this plan, it will conduct the activities that will formalize, rating and evaluate benefits for high value applications and enable national interoperability for the transmission of safety related information exchange (signal phase and timing data) between roadside equipment (RSE) and/or nearby vehicles. For the commercialized vehicle enforcement applications this plan establishes research and demonstration activities to support enforcement regulations and real-time parking information in a wireless environment. Intelligent Transportation System (ITS) Information technology (IT) has transformed many fabrications, from education to health management system to administration, and is now in the early stages of transforming the transportation systems. This system helps to improving a country s transportation system solely means building new roads or repairing aging substructures of the system, the future work of transportation repose not only in concrete and steel, but also used in IT extension. IT enables the various elements within the transportation system like vehicles, roads, traffic lights, message signs, to become self-regulating by inserting them with microchips and sensors and empowering them to communicate with each other through wireless network technology. In the essential nations in the world, ITS fetch the relevant enhancement in transportation system performance, including reduced congestion and increasing safety and traveler convenience. Transportation systems are networks and, much of the value of a network in contained in its information. For example, whether a traffic signal knows there is traffic waiting to pass through an intersection; whether a vehicle is drifting out of its lane; whether two vehicles are likely to collide at an intersection; whether a roadway is congested with traffic; what the true cost of operating a roadway is; etc. Intelligent transportation systems empowers actor in the transportation system-from commuters, to highway and transmit network drivers, to the authentic devices, such as traffic lights, themselveswith useful information to make better-knowledgeable decisions, this decision help to choosing which route to take; when to travel; whether to mode-shift (take mass transmit instead of driving); how to optimize traffic signals; where to build new roadways; and hoe to hold providers of transportation services accountable for results. This information can be used both to maximize the operational performance of the transportation network and to move towards performance based funding for transportation systems. ITS also represent an appearing new framework related to platform, from which a entire hosting of new products and services are properly emerged, many of them can hardly be assuming today. II. OVERVIEW OF ROUTING PROTOCOLS The feature of highly dynamic topology makes the efficient designing for routing protocols for VANET challenging. The routing protocols of VANET can be grouping into five classes such as Topology based Routing Protocol, Position based Routing Protocol, Cluster based Routing Protocol, Ge ocast based Routing Protocol, and Broadcast based Routing Protocol. 1. Topology Based Routing Protocol In Topology based routing protocol, the data packets are send between source and destination within the network by using link s information among nodes. Topology based routing protocol can be further classified into two categories such as proactive (table -driven) and reactive (on-demand) routing. 1.1 Proactive (table-driven) Proactive routing protocols are mostly followed the shortest path algorithms. These protocols are table based so all information of connected nodes are stored in the form of table. Furthermore, the stored information in the tables shared with their neighbor nodes. Whenever the network topology changes then every node in the network updates its routing table. In this network the route identification is not required. For real time applications the latency is low. Unused paths occupy a noteworthy part of the capable bandwidth Fisheye State Routing FSR is a proactive or table driven routing protocol where the every node relate to their neighbors and the International Journal of Electrical & Electronics Engineering 2

3 information of every node fetch from their neighbors nodes. Then the routing table calculated. This protocol is based on the link routing protocol and instance of Global State Routing. In FSR, the consumed bandwidth significantly reduces as it exchanges the updated partial routing information with neighbors nodes. The routing overhead reduces. Updation in routing table will not occur even if there is any link failure in the network because there is no control message for link failure. In small ad hoc networks, the performance is very bad. Knowledge about distant nodes in the network is less. The storage capacity and the processing overhead increase due to increase the network size. The route establishing between the nodes has insufficient information. 1.2 Reactive (On Demand) Reactive routing protocol also named as on demand routing when a node communicate to another node then route discovering process execute and it will find the route from source to destination thus it will reduces the network traffic. The flooding of nodes in the network occur when the network needs to communicate each other among nodes. The network in beaconless manner so it saves the bandwidth of the network. High latency for route finding. Due to excessive flooding of the network, disruption of nodes communication occur Ad Hoc on Demand Distance Vector (AODV) AODV routing protocol is reactive routing protocol in which a route is establish when a node needs to send the data packets. In which unicast and multicast routing process occur. Each node uses a destination sequence number (DestSeqNum) which makes it unique from other on demand routing protocol. By knowing the destination sequence number, the path to destination up-to-date. It reduces too much memory required and redundancy between nodes. AODV respond if any link fail in the network. It can be applicable for large scale ad hoc network. Connection setup between nodes and communication among nodes to establish a route require more time as compared to other approaches. If middle nodes contain old entries, inconsistency in routes occur. For a single route reply packet and multiple route reply packets it will lead to heavy control overhead. Due to periodic beaconing nature it consume additional bandwidth Dynamic Source Routing The Dynamic Source Routing (DSR) mainly represented the source utilized in routing and active routes maintained in the network. DSR has contain two processes like discover the route and maintain the routes. Beacon nature is less. The route establish between nodes, during this process small overload on the network. Then it will use caching process to reduce the load on the network for future discovery process. In DSR periodically updation not required. If the network has huge structure then the route information store in the header which leads to byte overloading. Unwanted flooding load the network. Inadequate to repair the broken links. Due to high mobility model it performs worse Temporally Ordered Routing Protocol (TORA) Temporally Ordered Routing Protocol is establish on the link reversal algorithm that creates a direct acyclic graph like tree tend to destination where the source node acts as a root of the tree. In TORA data packets are broadcasted at sending node and rebroadcasted done by neighbors at receiving node. It follows the DAG, if the sending node at downward position. It creates the DAG when needed. Overhead reduces because all intermediate nodes no need to broadcast the message in the network. In dense network the performance is good. DSR and AODV perform well as compared to TORA so it is not used. It is scalable. 2. Position Based Routing Protocol In position based routing, each node in the network knows it s own and neighbor position, node by node determines the services as GPS. In this protocol any routing table and exchanging the link state information with adjacent nodes does not maintain. Information collected from GPS tool is used for routing decision. There are several types of position based vehicle-to-vehicle protocols are STBR, CAR, GPSR, A-STAR, GSR, GPCR etc. Route finding and organization is not necessary. It is Adaptable in nature. Acceptable for high node mobility pattern. Position determining services are needed. In tunnel GPS device doesn t work because satellite signal is not present there. 2.1 Greedy Perimeter Stateless Routing (GPSR) Greedy Perimeter Stateless Routing using the beacon to select the node which is nearest to the final destination node. Firstly, it uses the greedy forwarding algorithm if it is fail then it uses the perimeter forwarding algorithm for choosing a node through which a packet will proceed from source to destination. To forwarding the packet over the network a node requires to remember only one neighboring node location. Dynamically choosing the path for forwarding the packets in the network. Characteristics of high mobility node, the stale information of neighbors position is stored in the sending node neighbor table. In the packet header the information of destination node is stored and the header moves to the intermediate node, the information is never updated. 2.2 Greedy Perimeter Coordinator Routing (GPCR) Greedy Perimeter Coordinator Routing is also positionbased routing protocol uses the greedy algorithm to forwarding the packet in a pre-selected path in the network. Any external information and global information like static map does not needed in the GPCR. Underlying roads using the planar graph to represent which is based on GPCR. Any planarization problem like planar subgraphs, unidirectional links are not detected. GPCR depends on the junction node. Junction detection approach has two problems, in first approach fails on curve road and in second approach fails on sparse road. 2.3 Connectivity-Aware Routing (CAR) CAR is mainly designed for city and highway environment in which it uses the AODV protocol for discover the path and PCB for data dissemination mode. In CAR guard concept is used to maintain the path among nodes. Digital map is not needed in CAR. There is no local maximum problem occur. Packet delivery ratio is very high as compared to GPCR and GPSR+AGF, so CAR find the shortest path to deliver the packets. The unnecessary paths are also selected for further connectivity. When the traffic environment change, it doesn t adjust with different sub-paths. 2.4 Geographic Source Routing (GSR) GSR routing is the combination of position-based routing and topological knowledge for vehicular ad hoc network in city environment. GSR uses the greedy algorithm International Journal of Electrical & Electronics Engineering 3

4 through pre-selected shortest path and this path is determined by the Dijkstra algorithm. GSR is more flexible and better packet delivery ration as compared to AODV and DSR.In the sparse network there are limited nodes to forward the packets, so GSR abandon this condition. GSR exhibit higher routing overhead as compared to GyTAR because hello messages uses as control messages. 2.5 Anchor-Based Street and Traffic Aware Routing (A- STAR) A-STAR is also position-based routing protocol which is mainly design for inter communication system in city scenario. By using the vehicular traffic bus the ratio of connectivity of packet delivery is very high between endto-end connection. A-STAR determine the end-to-end connection for low density traffic. By contrasting the greedy approach of GSR and perimeter mode of GPSR, A- STAR uses the new local recovery strategy which is more acceptable for city scenarios. A-STAR in which the path selection procedure ensure that the connectivity between nodes is very high and packet delivery ratio is low as compared to GSR and GPSR. Path selection strategy uses the static information to maintain the path between nodes which is based on the city bus routes which causes the connectivity problem on some section of streets. 2.6 Street Topology Based Routing (STBR) Street Topology-Based Routing based on the street map as a planar graph, in which three logical states are mention: master, slave, and forwarder node. In STBR one node is choose for master on the junction, other nodes behave like slaves, adjacent nodes among junctions act as forwarders. For long distance unicast communication least spanning multiple junctions are negotiate. STBR is not suitable for mixed scenario. It is mainly used to send the junction beacon through highway. STBR increase the complexity due to sending the two-hop neighbor table to new master when the old master vacate the junction. 3. Cluster Based Routing Protocol In cluster based routing protocol, clusters created among nodes and vehicles. A group of nodes recognize themselves to be a part of cluster and each cluster has its own cluster-head, through which the communication will occur by two ways: inter and intra-communication. In intra-communication, each cluster is connected through direct link and in inter-communication, each cluster is connected by cluster-head for communicate each other. In this method, cluster-head broadcasting the packet to cluster which gives the more flexibility for huge networks while for high mobility feature of VANET it will increase the network delay and overhead. There are different types of cluster based routing protocols are CBDRP, HCB, CBR, CBLR etc. 3.1 Hierarchical Cluster Based Routing (HCB) HCB uses the clustering approach which is mainly designed for high mobility ad hoc networks. For communication HCB uses the two layer communication architecture. In Layer-1 the nodes have single radio network and through multi-hop path nodes are communicate with each other. In Layer-2 base station helps to communicate among nodes in the network. In intra-cluster routing, each cluster independently executed. Cluster heads interchange the membership information systematically to enable the inter-cluster routing. Due to high packet loss in HCB, the number of retransmission occur more. 3.2 Cluster-Based Directional Routing Protocol (CBDRP) CBDRP is mainly designed for vehicles which are going in same direction. Firstly, the source node passes the packet to cluster header then cluster header passes the packet to same cluster which is in same direction. Cluster header has the main responsibility to forward the packet to destination cluster. This protocol perform same as CBR but the direction and velocity of the vehicle are noticed when the packet forward to the cluster. With the help of CBDRP link stability problem resolved in the VANET. Data transfer in the network through clusters is more reliable and rapidly. During the packets transmit in the clusters, the control packet overhead is low. This protocol is more reliable for transmission the packets due to this the number of retransmission is more occurred. 3.3 Cluster Based Location Routing (CBLR) CBLR is a cluster based protocol and reactive and on demand routing protocol. In this protocol, each cluster head contains its own routing table in which is stored the addresses and locations of the all cluster members in the network. Cluster header also keep the information about all neighboring clusters in the Cluster Neighbor Table. When the packet transmit between source and destination in the network then the source node firstly send the packet to the nearest neighbor of the destination if it is in same direction/cluster. If the destination is not in same cluster then the packet stores in the buffer then the Location Request (LREQ) packet broadcasting and start the timer. This protocol is more suitable for high mobility network. Digital map is used to transmit the packets over the network. The packets transmit in the same cluster due to this reason the overhead of control packet is low. The number of transmission is more because this protocol is used for huge network. 3.4 Cluster Based Routing (CBR) CBR is a routing protocol which is depends on the position and cluster where the geographical area of the cluster is divided into rectangular grids. With the help of geographical information each node send packet to the next node. If there is any vehicle present in the grid is chosen as a cluster header then it widely disseminated a LEAD message to its neighbors and whenever header leave the chosen grid, it will disseminate LEAVE message containing its grid position. Discover the route in the network is not needed do the routing overhead is very less. The important parameter for VANETs are velocity and direction which are not considered in this protocol. 3.5 Location Routing Algorithm with Cluster-Based Flooding (LORA-CBF) LORE-CBF is same as greedy algorithm for routing. The cluster-head is responsible for maintain the information among nodes. When the two clusters is joined by a node then it is known as gateway. When the destination of a node is not mentioned then cluster head and gateways send location request (LREQ) packets. In LORA-CBF packet forwarding same as the greedy routing. The performance of this protocol show the heterogeneous results. 4. Broadcast Based Routing Protocol Broadcast based routing protocol also called flooding based routing protocol which is mainly used in VANET International Journal of Electrical & Electronics Engineering 4

5 for distributing the information between vehicles as when an accident and an event occurs then transfer the information to the maximum possible nodes. Broadcast send the single packet to all nodes available in the network which effect the exponential increase in message emission leads to collisions, consume the bandwidth in large amount and degrade the overall performance of the network. While this protocol implement better when small numbers of nodes are elaborated. Various types of broadcast routing protocols are classified as BROADCOMM, V-TRADE, EAEP, PBSM, DECA, UMB, DV-CASDT, SRB, PGB, POCA etc. 4.1 BROADCOMM BROADCOMM is mainly designed for highway network which is based on hierarchal structure. In this protocol, highway is divided into virtual cells which move alongside with vehicles. For the highway two levels of hierarchy structure design for the nodes. In first level all the nodes in a cell are elaborated. In the second level cell reflectors are represented which are responsible for handle the messages with in the cell nodes and receiving and sending the messages to or from the neighboring cell reflectors. For the simple highway structure which contains the small number of nodes the performance of this protocol is better. Position information of the node which fully depend upon the formation of cells in the network. 4.2 Edge-Aware Epidemic Protocol (EAEP) EAEP is a distinct type of protocol. The procedure of this protocol is that it broadcasting the messages between vehicles and each vehicles has its own piggybacks and piggybacks store the geographical position. After accepting a new rebroadcast message then EAEP take the decision whether nodes will rebroadcast the message or not by using the number of transmission from front and back nodes in a given interval of time period. While any message drop in the network, EAEP does not know about it. Eliminate the hello packets will reduce the control packet overhead. It will control the simple flooding problem. Dropped messages are not recognized by the protocol due to this problem high delay of data transmission arise. If any connection broken in the network are not addressed in this protocol. 4.3 Distributed Vehicular Broadcast Protocol (DV - CAST) DV-CAST is mainly based on the connectivity issues as well connected, infrequently connected, and totally disconnected neighborhood that splits the vehicles into three categories. Well connected neighborhood determination scheme is used, for infrequently connected neighborhood vehicles can directly rebroadcast with vehicles going in the same direction after receiving the broadcast message, for totally disconnected neighborhood vehicles keep the broadcast message until the another vehicle enters into transmission range. When the given interval of time period expired then the packets are discarded. In distributed vehicular broadcast protocol using the flag variable to check whether the packet is redundant or not. Source to destination send the packets take the lot of time period i.e. delay is high for transferring the packets and control overhead is also high. 4.4 Secure Ring Broadcasting (SRB) In Secure Ring Broadcasting the nodes are classified into three groups which are based on receiving power as Inner Nodes, Outer Nodes, and Secure Ring Nodes. The nodes which are close to sending node is marked as Inner Nodes, far away from sending nodes marked as Outer Nodes, preferable distance from sending node marked as Secure Ring Nodes. Less transmission of messages between nodes maintain the stable route between nodes. Control packet overhead is high. 4.5 Parameter Less Broadcasting in Static to highly Mobile Wireless ad hoc (PBSM) In Parameter less broadcasting in static to highly mobile wireless ad Hoc (PBSM) nodes does not require to know the neighboring nodes information. To eliminate the unnecessary broadcasting the nodes in the network it uses the connected dominating sets (CDS) and neighbor eliminating concepts. It contains two lists of neighboring vehicles: R and NR is preserved by each vehicle which help to identify neighbors nodes that are already received and nodes which are not received the packets in the network. When the time interval is finished then it broadcasts the packets again. The terms like vehicle position, direction, and velocity are not considered in this protocol. Control packet overhead is high. 4.6 Preferred Group Broadcast (PGB) This protocol is designed to prevent the broadcast storm problem from route request broadcasting. In PGB each node understand the level of signal strength from its neighbor broadcasting. The messages broadcasting again only for those nodes which has shortest timeout. This protocol reduces the number of RREQ broadcasting. PGB broadcasting protocol is not authentic. 4.7 Urban Multi hop Broadcast Protocol (UMB) UMB is mainly designed to solve the collision problem and hidden node problems through message distributed in the multi hop broadcast. In this protocol without use any prior topology information the sender node tries to select the furthermost node in the broadcasting direction for sending and acknowledging the packet. The performance of UMB is better in higher packet loads and vehicle traffic density scenarios. The advantage of this protocol is that it will overcome the problem of packet collision and hidden node problems. Main disadvantage of this protocol is that it waste the lot of bandwidth 4.8 Vector Based Tracing Detection (V-TRADE) In vector based tracing detection the message broadcasting protocol classified the neighboring nodes into different forwarding groups which are based on the GPS. Firstly, it selects the small subset of vehicle for each group to rebroadcast the message. Bandwidth utilization is small as compared to other protocols. Routing Overhead occurs when it selecting the forwarding node in every hop. 4.9 Density-aware Reliable Broadcasting Protocol (DECA) DECA does not need the positioning knowledge of nodes and for broadcasting the message it selects the neighbor node which has the highest local density information. In this protocol receiving broadcasting messages are included in periodic signal thus a node can recognize the neighbor node, nodes have not received the messages and broadcast the messages again for those neighbors. Before timeout if all nodes do not recognize anyone rebroadcast the message then they will broadcast the message again. 5. Geo cast Based Routing Protocol International Journal of Electrical & Electronics Engineering 5

6 Geo cast routing protocol is a location based multicast routing protocol which define the geographical region and this is used to send a message to all vehicles in pre-defined geographical region. The selected area of communication is known Zone of Relevance or ZOR. The main objective is that sender node not keep the packets of nodes beyond the ZOR. In geo cast direct flooding procedure is used because with the help of direct flooding the amount of overhead and network congestion is reduced. The different types of Geo cast routing protocols are ROVER, DTSG, IVG, DG-CASTOR, DRG. 5.1 Inter-Vehicle Geo cast (IVG) IVG is also designed for highways which is used to distributed the safety messages to vehicles on highways. For forwarding the messages in network, it is used the timer based mechanism. For overcoming the network fragmentation periodic broadcasting technique is used. 5.2 Robust Vehicular Routing (ROVER) Robust Vehicular Routing is a Geo Cast Based Routing Protocol which has the main aim to send the message to all adjacent vehicles within a particularize Zone of Relevance. In this protocol control messages and data packets following the different strategy to send the packets, control packets are broadcasted in the network and data packets are unicasted. This protocol is a highly reliable geographical multicast protocol. Delay in data transfer is high because of unnecessary messages transfer in the network. Control packet overhead is high. Number of transmission processed high due to overhead. 5.3 Dynamic Time-Stable Geo cast Routing (DTSG) Dynamic Time-Stable geo cast routing is mainly designed for the sparse density networks. Two phases followed by this protocol: Pre-stable phase helps to distributed the messages within the region and Stable-Period transitional node use to store and send procedure for a predefined time with in the region. Number of transmission processed high due to overhead. In this protocol dynamically adjust the network density and vehicle speed for better performance. III. CONCLUSION In this paper, we have emphasis the various routing protocols that are relevant n vehicular communication for the development. There are various existing routing protocols for VANET which are not efficient to meet the traffic framework. Thus design of nay efficient routing protocol has capture expressive observation. By examining the different routing protocols in VANET we have seen that further performance estimation is required to validate the performance of a routing protocol with other routing protocols based on various traffic frameworks. With the comparison of different VANET protocols characteristics is necessary to design a new proposal for VANET. REFERENCES [1] W. Franz, H. Hartenstein, and M. Mauve, Eds., Inter-Vehicle- Communications Based on Ad Hoc Networking Principles-The Fleet Net Project. Karlshue, Germany: Universitatverlag Karlsuhe, November [2] Forderer, D (2005). Street -Topology Based Routing. Master s thesis, University of Mannheim, May [3] Rainer Baumann, Vehicular Ad Hoc Networks, Master s Thesis in Computer Science, ETH Zurich (2004). [4] Perkins, C.; Belding-Royer, E.; Das, S. (July 2003) Ad Hoc On-Demand Vector (AODV) Routing. [5] Johnson, D. B. and Maltz, D. A> (1996), Dynamic Source Routing in Ad Hoc Wireless Networks, Mobile Computing, T. Imielinski and H. Korth, Eds., Ch. 5, Kluwer, 1996, pp [6] Park, V.D., Corson, M.S. (1997), A highly adaptive distributed routing algorithm for mobile wireless networks, INFOCOM 97. Sixteenth Annual Joint Conference of the IEEE Computer and Communication Societies. Proceedings IEEE, vol.3, no., pp vol.3, 7-12 Apr [7] Karp, B. and Kung, H. T (2000), GPSR: greedy perimeter stateless routing for wireless networks. In Mobile Computing and Networking, pages , [8] Lochert, C., Mauve, M., Fussler, H., and Hartenstein, H., Geographic routing in city scenarios, SIGMOBILE Mob. Comput. Commun. Rev., vol.9, no. 1, pp , [9] R. A. Santos, Performance evaluation of routing protocols in vehicular ad hoc networks, [10] Seet, B.-C., G., Lee, B.-S., Foh, C. H., Wong, K. J., Lee, K.- K. (2004), A -STAR: A Mobile Ad Hoc Routing Strategy for Metropolis Vehicular Communications. NETWORKING 2004, [11] A. Bachir, A Multicast Protocol, In Ad Hoc Networks Inter-Vehicle Geocast. April [12] M. Khil, Reliable Geographical Multicast Routing in Vehicular Ad Hoc Networks, [13] M. Sum, GPS-based message broadcasting for intervehicle, (2000). [14] Tao Song, Wei Xia, Tiecheng Song, Lianfeng Shen, A Cluster-Based Directional Routing Protocol in VANET, International Conference on Communication and Mobile Computing, [15] [16] Eriscon, Communication and Mobility by Cellular Advanced Radio International Journal of Electrical & Electronics Engineering 6