This document summarizes an article that proposes improvements to the Ad hoc On-Demand Distance Vector (AODV) routing protocol for use in Vehicular Ad hoc Networks (VANETs). It first provides background on VANETs and discusses different types of routing protocols used in VANETs, including topology-based, position-based, and hybrid protocols. It then focuses on improvements made to the reactive AODV routing protocol, including adding link layer security checks and a method to reduce packet delay called AODV_BD. The goal of these improvements is to create more stable routes and reduce packet delay for safety communications between vehicles.

1. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-
6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 4, July-August (2013), © IAEME
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IMPROVEMENT OVER AODV ROUTING PROTOCOL IN VANET
Miss. P.A. Kamble Dr. M.M. Kshirsagar
Ph. d. Scholar, G.H. Raisoni college of engg. Dean Student Activities, YCCE Nagpur
Autonomous Institute Affiliated to Autonomous Institute Affiliated to
Nagpur University Nagpur University
Asst. Professor, CT Dept. PCE, Hingna Road, Hingna Road, Nagpur- 440019(MH),India
Nagpur-440019(MH),India
ABSTRACT
Vehicular Ad Hoc Network (VANET) is a sub class of mobile ad hoc networks. VANET is
most superior technology for intelligent transportation system provides wireless communication
between vehicles and vehicle to road side equipments, according to IEEE 802.11 p standard for end
to end communication between vehicles. For end to end communication between vehicles a routing
protocols is used to find a route based on link properties. One of the most vital routing protocols used
in ad hoc networks is AODV. This protocol is connectivity based reactive protocol that searches
routes only when they are needed because bandwidth is limited and topology frequently changed. It
always exchanges control packets between neighbor nodes for routing. This article presents the
cross layer technique that find channel security at link layer to AODV routing protocol to improve
the communication in vehicles for safety purpose. To reduce the packet delay in AODV, propose the
routing protocol (AODV_BD). It reduces the packet delay in AODV and makes routes more stable.
Keywords: Ad hoc network; VANET; AODV; AODV_BD;
I. INTRODUCTION
Vehicular Ad hoc Network (VANET) is measured as a special type of Mobile Ad hoc
Network (MANET), which gains attention from many researchers. In VANET each vehicle acts as a
router to exchange data between nodes in the network. It is designed for vehicle-to-vehicle (V2V)
and infrastructure-to-vehicle (IVC) communication. Such networks are used in traffic control
applications, safety applications, driver assistance and location based services. In VANETs power
consumption and storage capacity are not limited and the position of the nodes can be determined by
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using GPS. VANET has inimitable characteristics like high mobility with the constraint of road
topology, initially low market penetration ratio, unbounded network size, infrastructure support that
differentiate it from MANET. From the above mentioned characteristics, it is obvious that
conventional MANET routing protocols has difficulties from finding stable routing paths in VANET
environments. Therefore, more and more researchers have concentrated on proposing suitable
routing protocols to deal with the highly dynamic nature of VANET. The routing protocols in
VANET are categorized into six types: Topology based, Position based, Geocast based, Cluster
based, broadcast based and Infrastructure based. The rest of the paper is organized as follows.
Section 2 deals with Topology based protocols, Section 3 on Improvement over AODV, Section 4 on
Security Techniques Used In AODV, Section 5 on To Reduce Packet Delay In AODV: AODV_BD,
Section 6 Issues and Challenges and Section 7 Conclusions, Section 8 gives References
II. TOPOLOGY BASED PROTOCOLS
These protocols discover the route and maintain it in a table before the sender starts
transmitting data. They are further divided into Proactive, Reactive and hybrid protocols.
A. PROACTIVE PROTOCOLS
The proactive protocol is also known as table driven routing protocol. These protocols work
by periodically exchanging the information of topology among all the nodes of the network. The
proactive protocols do not have initial route discovery delay but consumes lot of bandwidth for
periodic updates of topology. There are several routing protocols that fall under this category.
Fisheye state routing (FSR) [3]: It is similar to link state routing protocol (LSR). Each node
maintains a topology table based on the latest information received from neighborhood nodes. It uses
different exchange period for different entries in routing table to reduce the size of control messages
in large networks. The disadvantage in FSR routing, is the size of the routing table increases with
increase in network size. Route discovery may fail if the destination node lies out of scope of source
node. Due to high mobility in VANET, route to remote destination become less accurate.
Optimized Link State Routing Protocol (OLSR) [5]: It is an optimization of a pure link state
protocol for mobile ad hoc networks. Each node in the network selects a set of neighbor nodes called
as multipoint relays (MPR) which retransmits its packets. The neighbor nodes which are not in its
MPR set can only read and process the packet. This procedure reduces the number of retransmissions
in a broadcast procedure.
Topology Dissemination Based on Reverse-Path Forwarding (TBRPF) [8]: It is a link-state
routing protocol designed for ad-hoc networks. Every node constructs a source tree which contains
paths to all reachable nodes by using topology table. Nodes are periodically updated with only the
differences between the previous and current network state using HELLO messages. Therefore,
routing messages are smaller, can therefore be sent more frequently to neighbors.
B. REACTIVE PROTOCOLS
These protocols are called as on-demand routing protocols as they periodically update the
routing table, when some data is there to send. But these protocols use flooding process for route
discovery, which causes more routing overhead and also suffer from the initial route discovery
process, which make them incompatible for safety applications in VANET.

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AODV [2]: Is a source initiated routing protocol and uses HELLO messages to identify its
neighbors. Source node broadcasts a route request to its neighbors which fill forward to the
destination. Then the destination unicast a route reply packet to the sender. Every node maintains
broadcast-id which increments for new RREQ. When a RREQ arrives at a node, it checks the
broadcast id if it is less than or equal to previous message then it will reject the packet.
DSR [1]: It Uses source routing in its place of depending on intermediate node routing table. So
routing overhead is always dependent on the path length. The restriction of this protocol is that the
route maintenance process does not locally repair a broken link. The performance of the protocol
briskly decreases with increasing mobility.
Temporally-Ordered Routing Algorithm (TORA) [15]: Each node constructs a directed cyclic
graph by broadcasting query packets. On receiving a query packet, if the node has a route to
destination it will send a reply packet, else it drops the packet. A node on receiving a reply packet
will update its height only if the height of packet is minimum than other reply packets. It gives a
route to all the nodes in the network, but the maintenance of all these routes is difficult in VANET.
C. HYBRID PROTOCOL
The hybrid protocols are introduced to reduce the control overhead of proactive routing
protocols and decrease the initial route discovery delay in reactive routing protocols.
Zone routing protocol (ZRP) [24]: In this the network is divided into overlapping zones. The
zone is defined as a collection of nodes which are in a zone radius. The size of a zone is determined
by a radius of length α where α is the number of hops to the perimeter of the zone. In ZRP, a
proactive routing protocol (IARP) is used in intra-zone communication and an inner-zone reactive
routing protocol (IARP) is used in intra-zone communication. Source sends data directly to the
destination if both are in same routing zone otherwise IERP reactively initiates a route discovery.
ZRP aims to find loop free routes to the destination. It uses border casting method to construct
multicast trees to flood the query packets instead of standard flooding to discover the destination
route.
HARP [17]: It divides entire network into non-overlapping zones. It aims to establish a stable
route from a source to a destination to improve delay. It applies route discovery between zones to
limit flooding in the network, and choose best route based on the stability criteria. In HARP routing
is performed on two levels: intra-zone and inter-zone, depending on the position of destination. It
uses proactive and reactive protocols in intrazone and inter-zone routing respectively. It is not
applicable in high mobility ad hoc networks.
III. IMPROVEMENT OVER AODV
The ad hoc on-demand distance vector routing protocol (AODV) joins mechanism of DSR
(Dynamic Source Routing protocol) and DSDV (Destination-Sequenced Distance-Vector Routing).
The periodic beacon, hop-by- hop routing and sequence numbers of DSDV(Destination sequence
distance vector ) which based on Bellman –ford algorithm and pure on –demand mechanism of route
discovery and route maintenance from DSR are combined, which is not scalable for the long
distance. AODV routing consists of three phases: route discovery, data transmission and route
maintenance. Route discovery phase starts when a node wants to transmit data and has no route to
destination. Now, AODV call route discovery process. In this phase, source node broadcasts a Route

4. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-
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Request Packet (RREQ) to its neighbor. Nodes that receive RREQ packets divide into three
categories: the receiver nodes the destination of route, the node that has a route to destination or none
of both. In the two first, receiver uncast a Route Reply (RREP) packet to the route that received
Route Request (RREQ) packet. The route that RREP packet traverses, selected as one of the main
routes for source that has been sent RREQ packet. [4] Route maintenance phase maintain the nodes
analysis the link status of their next hop neighbors in active routes .The route detecting a link break
sends a ROUTE ERROR message to each of its upstream neighbors to invalidate this route and these
propagate the ROUTE ERROR to their neighbors. This continue until the source node is reached.
Each node periodically transmit a HELLO message to detect the link breakage. The failure of
reception of three consecutive HELLO message from a neighbor is handles as link error [5].
IV. SECURITY TECHNIQUES USED IN AODV
The Secure Ad hoc On-Demand Distance Vector (SAODV) addresses the problem of
securing a VANET network. SAODV is an extension of the AODV [4] routing protocol that can be
used to protect the route discovery mechanism improvising security features like integrity,
authentication and non-repudiation. SAODV assumes that each ad hoc node has a signature key pair
from a suitable asymmetric cryptosystem. Further, each ad hoc node is capable of securely verifying
the association between the address of a given ad hoc node and the public key of that node.
Achieving this is the job of the key management scheme. Two mechanisms are used to secure the
AODV messages: digital signatures to authenticate then on-mutable fields of the messages, and hash
chains to secure the hop count information (the only mutable information in the messages). This is
because for the non-mutable information, authentication can be performed in a point-to point
manner, but the same kind of techniques cannot be applied to the variable information. Route error
messages are protected in a different manner because they have a big amount of variable
information. In addition, it is not relevant which node started the route error and which nodes are just
forwarding it. The only relevant information is that a neighbor node is informing to another node that
it is not going to be able to route messages to certain destinations anymore. Therefore, every node
(generating or forwarding a route error message) uses digital signatures to sign the whole message
and that any neighbor that receives verifies the signature [9].
V. TO REDUCE PACKET DELAY IN AODV: AODV_BD
IN VANET because of fast moving nodes, frequent topology changed and slow convergence
of routing protocol, data packet wait more time not to find the suitable which causes more delay and
lowers packet delivery rate, to decrease these hurdles AODV-BD works properly. when the link
breaks between source and destination node by sending the a routing a routing request packet and a
routing reply packet, at the same time the data packets have been cached. When the route is set up it
not only increases the delay, but also leads to the invalid routing because of change in the newly
created topology [3]. AODV-BD establish a routing to the destination node by the broadcasting the
data packet when the local repair is going on. Data packet broadcast not only the request packet, but
also the data packets. When nodes find any interrupt it will broadcast the packet rather than the
RREQ .the packet header in packet establish the reverse routing and finding the routing. when the
data packet reach the intermediate nodes ,they record the reverse routing and then re–broadcast this
data packet, when it reach the destination, it will send a RREP and at the same time receive the data
packets, in this way it not only set up the link but also reduce the delay.

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VI. ISSUES AND CHALLENGES
Uncooperative behavior in VANET, such as message modification and dropping, could
substantially lower the message delivery ratio and further affect the safety of other vehicles. In
broadcasting or flooding the data item lot of bandwidth loss took place. It may cause the congestion
in network, deceases the throughput and delay increases. Therefore, new distributed mechanisms like
AODV-BD designed to promote cooperation in VANET for packet delay. But some problems like
Search latency may degrade the performance of interactive application and the quality of a path is
not known a priori. Route caching, a mechanism typically employed by on demand protocol, proves
useless in high mobility situation as routes change too frequently. To send data from source to
destination flooding technique is the most reliable method in terms of coverage but too many
redundant messages are generated. However, drawbacks incurs such as long delay time resulted from
beacon messages among neighboring nodes and packet collisions due to many packets sent[6].it is
minimize with help of AODV-BD up to some limit but some issues are still present in AODV like If
intermediate nodes contain old entries it can lead inconsistency in the route. For a single route reply
packet if there has multiple route reply packets this will lead to heavy control overhead - Because of
periodic beaconing it consume extra bandwidth .we will work on these issues.
VII. CONCLUSIONS
This article has presented the different strategy of efficiency improvement of AODV routing
protocol in VANET, reduces packet delay by using the AODV-BD protocol by broadcasting the data
packet when local repair is going on. SAODV uses digital signature to authenticate non mutable
fields and hash chains to authenticate the hop- mutable fields and hash chains to authenticate the hop
count field in both RREQ and RREP message
VIII. REFERENCES
[1] Noppakun Yaw an and Phongsak Keeratiwintakorn “Efficiency Improvement of AODV for
Vehicular Networks with Channel Availability Estimation” The 8th Electrical Engineering
electronics, Computer, Telecommunications and Information Technology (ECTI) Association
of Thailand - Conference 2011.
[2] Omid Abedi and Reza Barangi andM. Abdollahi Azgomi” Improving route stability and
overhead of the AODV routing protocol and making it usable for VANETs” 2009 29th IEEE
International Conference on Distributed Computing Systems Workshops
[3] Baozhu Li, Yue Liu and Guoxin Chu “Improved AODV Routing Protocol for Vehicular Ad
hoc Networks “, 20IO 3rd International Conference on Advanced Computer Theory and
Engineering (ICACTE) [
4] Omid Abedi, Reza Barangi and M. Abdollahi Azgomi,:” Improving route stability and
overhead of the AODV routing protocol and makeing it usable for VANETs”, 2009 29th IEEE
International Conference on Distributed Computing Systems Workshops
[5] Evjola spaho ,leonard barolli and jigjig Mino. ”performance Evaluation of AODV, OLSR and
DYMO protocol for vehicular network udsing CAVENET”,2010 13th international
conference on network based information system.
[6] Gongjun Yan, Nathalie Mitten, and Xu Li2,”Reliable Routing in Vehicular Ad hoc
Networks”, 2010 IEEE 30th International Conference on Distributed Computing Systems
Workshops.

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[7] Nur Diana Mohd. Nuri, Halabi Hasbullah.” Strategy for Efficient Routing in VANET”, 978-1-
4244-6716-711 0/$26.00 ©20 1 0 IEEE [8] Bijan Paul, Md. Ibrahim.” VANET Routing
Protocols: Pros and Cons” International Journal of Computer Applications (0975 –
8887)Volume 20– No.3, April 2011 [9] Monis Akhlaq, M Noman Jafri, Muzammil A Khan,
and Baber Aslam,” Addressing Security Concerns Of Data Exchange in AODV Protocol”
World Academy of Science, Engineering and Technology 16 2006.
[8] A Study of Improved Aodv Routing Protocol in Vanet Annu Mor Research Scholar, Dept. of
Computer Science Applications, Kurukshetra University, Kurukshetra.
[9] Mitul K. Patel, “Study of Localization Techniques in Vehicular Ad-Hoc Networks”,
International journal of Computer Engineering & Technology (IJCET), Volume 4, Issue 4,
2013, pp. 194 - 202, ISSN Print: 0976 – 6367, ISSN Online: 0976 – 6375.
[11] T.Priyadarsini, B.Arunkumar, K.Sathish and V.Karthika, “Traffic Information Dissemination
in Vanet using IEEE-802.11”, International Journal of Electronics and Communication
Engineering & Technology (IJECET), Volume 4, Issue 1, 2013, pp. 294 - 303, ISSN Print:
0976- 6464, ISSN Online: 0976 –6472.
[10] R.Boopathi and R.Vishnupriya, “Performance Evaluation of AODV and OLSR in VANET
under Realistic Mobility Pattern”, International Journal of Electronics and Communication
Engineering & Technology (IJECET), Volume 4, Issue 2, 2013, pp. 58 - 71, ISSN Print:
0976- 6464, ISSN Online: 0976 –6472.