International Journal of Engineering Trends and Technology (IJETT) – Volume 21 Number 10 – March 2015
A Review - Understanding the Scenario of VANET
Technology
Pankaj Joshi#1, Jaswinder Kaur*2
#
*
M.Tech Scholar, Department of ECE, SBSSTC, Ferozepur, Punjab, India
Assistant Professor, Department of ECE, SBSSTC, Ferozepur, Punjab, India
Abstract— Life is the most precious gift of God. But accidents are it may be device used for specific application or a simple
the serious issue which takes thousands of lives per year. In this device which is capable to access internet.
paper we focus on technology which has major role in avoiding
accidents. Vehicular Ad-hoc Network (VANET) is an application C. Road-side unit (RSU)
of wireless communication which has made our life easier, safer
The RSU is a device fixed along the road at specific
and comfortable. VANET has become the effective area of
locations and act as information hub. The RSU uses
research because it has great potential to avoid accidents,
enhance the vehicle safety, road safety, efficiency of traffic and IEEE802.11p radio technology and other access technologies
comfort and convenience of human beings. We describe the to communicate with other networks. The RSU is responsible
architecture, characteristics, standards, applications, routing for sending the information to OBU and other RSU, providing
safety and non safety applications and providing the internet
protocols and simulators which are helpful to realize VANET.
Keywords—VANET, Routing protocols, VANET Simulators
OMNET++
connectivity to OBUs [1, 2].
I. INTRODUCTION
VANET is one of the emerging technologies which are
growing rapidly in the field of communication technologies. It
is the sub form of mobile Ad-hoc networks (MANET).
VANET allows the vehicles to communicate with other
vehicles and road side infrastructure (RSU). The difference
between MANET and VANET are: MANET contains nodes
which have un-controlled moving patterns whereas in
VANET, movement of vehicles is restricted by factors like
roads, traffic regulations. Nodes are assumed in VANET to
Fig.1 Architecture of VANET
have energy and computing power. In VANET, frequent
disconnection of network occurs due to link between vehicles
II. CHARACTERISTICS OF VANET
changes quickly. The vehicles are equipped with on–board
units and application units which has capability to A. Mobility Modeling
communicate with other vehicles and RSUs. The vehicles can
It is very difficult to predict the position of vehicles and
exchange data with each other and inform each other about
their movements. So for effective network design, it is
different events. The basic components of the network are
important to have a mobility model and prediction of vehicles
OBU, AU and RSU. Fig. 1 describes the basic VANET
based on predefined road layouts in different regions.
architecture.
B. Topology
A. On-board Unit (OBU)
The speed, direction and road layout defines the dynamic
An OBU is a device mounted on a vehicle used for
topology. The vehicles are moving with different speeds in
exchange of information between other OBUs and with RSUs.
different direction which leads to rapid changes in network
It consists of processor, user interface and network device for
topology.
wireless communication and have additional components
according to specific applications. OBU communicate with C. Power Issue
OBU and RSU through a wireless link based on IEEE802.11p
The power requirement is easily fulfilled in VANET
channel.
because the battery in vehicle has the ability to provide
continuous power to the OBU.
B. Application unit (AU)
The AU is a device within the vehicle that provides access D. Frequent Changing Network
to different applications provided by the source. The AU can
Due to the highly dynamic topology, the connection
be connected to OBU through wired and wireless connection, between the vehicles changes rapidly. The vehicle may
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International Journal of Engineering Trends and Technology (IJETT) – Volume 21 Number 10 – March 2015
disappear sometime when the information is sending to that
vehicle.
E. Communication Model
VANET operate in different environment: highways, urban
and rural areas. In highways, the mobility model is simple and
easier to predict. But for urban areas, the buildings, trees,
variable vehicle density and other objects act as obstacles in
communication. So the pattern of mobility is complex and
difficult in urban areas.
F. High Computational Capability
The vehicles are equipped with sensors and other resources
like processors, memory, antenna which are helpful for
effective communication by giving accurate information
regarding speed, position and direction of the vehicle.
G. Provide Safe Environment
VANET technology provides the direct communication
between vehicles. The warning messages(like accident ,
sudden braking, emergency vehicle coming etc) are send to
other vehicle which results in increasing the traffic efficiency
and provide safe and comfort environment to passengers and
drivers[1].
III. ROUTING PROTOCOLS OF VANET
Routing protocols is categorised on the basis of topology
and position. Topology based protocols are further divided
into proactive and reactive protocols. Position based protocols
are MOVE and GSR and proactive protocols are DSDV,
OLSR, FSR while reactive protocols are AODV, DSR and
TORA [3, 4].
dynamically over the time, so updating of routing table is
necessary. The routing table can be updated in two ways: full
dump update and incremental update. In full dump update, the
full routing table is sent to the neighbours whereas; in an
incremental update only those entries which are changed from
the previous one are sent or updated. The update can be time
periodic or event periodic [5].
2) Optimized Link State Routing Protocol (OLSR): OLSR
protocol keeps a routing table which contains information
about all possible paths to network nodes. When the network
topologies change, each node sends information to some
selective node, which again retransmits this information to
other nodes. OLSR protocol is best suitable for warning
applications because of its easy procedure [6].
3) Fisheye State Routing (FSR): It is a proactive routing
protocol which is based on the link state routing and global
state routing. In FSR, every node maintains a table which
contains the information received from the neighbouring
nodes. Each node periodically collects the information from
other nodes and updates it in routing table. The main
disadvantage of FSR routing is that the entries in routing table
increases with network size [7].
2) Reactive Routing Protocols
1) Ad Hoc on Demand Distance Vector (AODV): In AODV
routing, after receiving a broadcast query (RREQ), nodes
record the address of the node which send inquiry in the
routing table. This procedure of recording its previous change
is called backward learning. After reaching the destination, a
reply packet (RREP) is sent over the complete path. The node
would record its previous hop at each stop and establish the
forward path from the source. After the path has been
established, it is maintained as long as the source uses it [8].
2) Temporally Ordered Routing Algorithm (TORA): It is a
link reversal routing in which cyclic graph is built which
directs the flow of packets and ensures that it is reached to all
nodes. If a node has a downward link to destination then it
will broadcast a reply packet otherwise it drops the packet.
Since TORA provides route to all nodes so the maintenance of
routes becomes difficult in highly dynamic environment [9].
Fig.2 Routing Protocols in VANET
3) Dynamic Source Routing (DSR): In DSR, the source
indicates the sequence of intermediate nodes in a data packet
on the routing path. The destination then retrieves the entire
path from the query packet, and uses it to respond to the
source. As a result, the source can establish a path to the
destination. If we allow the destination to send multiple route
replies, the source node may receive and store multiple routes
from the destination. An alternative route can be used when
some link in the current route breaks [10].
A. Topology Based Routing Protocols
There are many protocols which are based on the topology of
B. Position based Routing Protocols
the network. Some of them are discuss below.
1) Proactive Protocols:
1) Destination Sequenced Distance Vector (DSDV): In
DSDV protocol, each mobile station advertises its routing
table to each of its neighbours. The entry in the table changes
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1) Greedy Perimeter Stateless Routing (GPSR) : Every
node frequently broadcasts a beacon message to all its
neighbors. If any node does not receives any beacon
message from a neighbor for a definite period of time,
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International Journal of Engineering Trends and Technology (IJETT) – Volume 21 Number 10 – March 2015
then GPSR router assumes that the neighbor has failed or out
V. VANET APPLICATIONS
of range, and deletes the neighbor from its routing table. It
takes greedy forwarding decisions using information about A. Safety Applications
immediate neighbors in the network. GPSR selects a node
1) Public Safety: Public safety applications provide
which is closest to the final destination by using beacon. It safety messages to the drivers which are helpful in safe and
uses greedy forwarding algorithm if it fails it uses perimeter comport journey to the people. Emergency vehicle
forwarding for selecting a node through which a packet will approaching warning is send to vehicles so as to provide clear
travel to destination [11].
route and on-time arrival of emergency vehicles to the
2) Geographic Source Routing (GSR): GSR routing was destination.
proposed for vehicular ad hoc networks in urban environments
which is the combination of position-based routing with
topological knowledge. It was improved by adding greedy
forwarding of messages along a pre-selected shortest path
& this path is calculated by using Dijkstra algorithm. It
has better packet delivery ratio and uses perimeter mode as a
recovering strategy if there is no node in direction of
destination [12].
3) Greedy Traffic Aware Routing Protocol (GYTAR): It
includes two processes i.e. Junction selection and forwarding
data between junctions. A packet will pass through various
junctions to reach its destination. In junction selection process
a value is assigned to each junction by comparing the traffic
density between the current junction and the next junction.
The highest value junction is selected for packet forwarding.
In second process, each vehicle periodically maintains the
routing table which contains position, velocity and direction
of each neighbor vehicle. GYTAR uses store and forward
strategy in which packet will be stored at some intermediate
node until another vehicle enters in its transmission range
which is closer to the destination junction [13].
IV. COMMUNICATION IN VANET
2) Intersection Collision Avoidance: If there is
probability of accident at intersection, a warning message is
send to vehicles so that they can necessary action to avoid
accident. The different warning messages includes warning
about violating the traffic signal and speed limit sign , left turn
and pedestrian crossing.
3) Vehicle Problem and Maintenance: This application
sends a notification to the drivers about if there is a fault
within the vehicle during the journey. The OBU send a
message to infrastructure and receive a reply message from
the support centre which is helpful in solving the desired
problem.
4) Informing Vehicle about Signs: This application alert
the drivers about the various signs placed over the road side to
prevent any accidents. It involves information about the
specific areas like hospital, school, colleges, companies etc
5) Communication between Vehicles: This application
involves the V-V communication for exchange of information
between vehicles about the various events like forward
collision warning, road condition warning, emergency brake
lights, lane change warning, pre-crash warning and vehicle
overtaking warning.
A. Inter-Vehicle Communication
B. Non–Safety Applications
It involves the communication between the different
Non safety applications aim to provide entertainment and
vehicles i.e. the OBU and AU of vehicles are involved in
increase the comfort levels of the drivers and passengers.
communication. The IVC is totally independent of
They provide the information regarding the current and future
infrastructure .The IVCs are further divided into two types:
weather forecasting and about the traffic over the route. It also
single hop IVC and multi hop IVC. In single hop, the vehicle
displays the location of restaurant, hotels and petrol station.
can send message to other vehicle which are in transmission Passengers can listen latest songs and videos, play online
range only. In multi hop, another vehicle can transmit the games, checking important mails and simple surfing the
message to the target vehicle which is not in the transmission
internet [1].
range of source vehicle. The inter vehicle communication
provides safety applications like collision avoidance,
electronic brake lights, passing assistance etc [14].
B. Vehicle-Roadside Communication
It involves the communication between the vehicle and RSU
and also with other infrastructure networks. It ensures
appropriate strategies for the implementation of privacy,
security and accessibility. The vehicles communicate with
RSU to increase the range of communication applications
(broadcasting warning messages, weather information etc.)
and with infrastructure networks to access the internet .In
vehicle to roadside communication, RSU sends a broadcast
message to all vehicles using high bandwidth link [15].
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Fig.3 Safety Applications
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International Journal of Engineering Trends and Technology (IJETT) – Volume 21 Number 10 – March 2015
Fig.4 Non Safety Applications
VI. STANDARDS IN VANET
Fig.5 Screenshot of SUMO
Dedicated short range communication (DSRC) is a short to
medium range communication technology that operates in 5.9 B. Traffic and network simulator (TraNS)
TraNS is a Java-based application with a visualization tool
GHz band for the purpose of public safety and specific
that
was built to link SUMO and NS-2 specifically designed
applications. DSRC provides high data rates within small
for
VANET simulation [18]. Fig 5 demonstrates the
communication range. At the PHY and MAC layers DSRC
screenshot
of TraNS. It works in two modes: network-centric
utilizes IEEE 802.11p Wireless Access for Vehicular
Environments (WAVE), a modified version of the familiar and application-centric. The network centric mode provides
IEEE 802.11 (Wi-Fi) standard. In the middle of the stack realistic mobility traces from the traffic simulator and used to
DSRC employs a suite of standards defined by the IEEE 1609 evaluate the VANET communication protocols that do not
Working Group: 1609.4 for Channel Switching, 1609.3 for affect the mobility of nodes. The application-specific mode
Network Services and 1609.2 for Security Services. DSRC allows the network simulator to control the mobility of
also supports use of well-known Internet protocols for the vehicles in simulation and used to evaluate VANET
applications. The specific interface known as TraCI is used for
Network and Transport layers. [16].
WAVE has become the standard and adopted all over the coupling road traffic and networking simulators. In both
world for wireless communication in vehicles. In the vehicular modes, the communication channel is set up over a dedicated
environment, many packets are sent directly over the air from TCP/IP connection. The problem with the TraNS architecture
the source to the destination. In order to avoid the packet is that the output obtained from NS-2 cannot be linked to
overhead issues, a new protocol is defined by IEEE 1609 and SUMO.
known as WAVE short message protocol (WSMP). WAVE
defines two types of devices: OBU and RSU which are mobile
and stationary node respectively. The stationary device host
an application that provide a service and the mobile device
uses the application.
VII.
VANET SIMULATORS
A. Simulation of Urban Mobility (SUMO)
It is an open source used for microscopic and multimodal
road traffic simulation.. It main features includes all
applications needed to prepare and perform a traffic
simulation [17]. It provide simulation of Space-continuous
and time-discrete vehicle movement , different vehicle types ,
lane changing , traffic lights , graphical user interface , high
Fig.6 Screenshot of TraNS
execution speed , Interoperability with other applications,
network , edge, vehicle and detector-based outputs . Fig 4 C. NS-2
illustrates the graphical interface of SUMO. It is a open source
NS-2 is a discrete event simulator developed by the VINT
which provides different routing algorithms of simple project research group at the University of California at
microscopic routes and user assigned dynamic algorithms. It Berkeley. The various components of NS2 are, NAM
has high portability and imports network files from other (network animator for visualizing outputs and GUI for
simulators.
different network scenarios), support, pre-processing tools and
post-processing tools (trace analysis: tcl/tk language, traffic
generators, perl, tcl). NS2 consists of two key languages: C++
and Object-oriented Tool Command Language (OTcl). The
C++ language defines the internal mechanism of the
simulation objects and the OTcl assemble and configure the
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International Journal of Engineering Trends and Technology (IJETT) – Volume 21 Number 10 – March 2015
objects as well as schedule discrete events. The C++ and the
OTcl are linked together using TclCL [19].
D. OPNET
Optimized Network Engineering Tool (OPNET) is a
network simulator used for wired and wireless network
simulations. OPNET simulation operates at packet-level and
built for the simulation of fixed networks. Currently OPNET
is licensed under Riverbed technologies. OPNET contains
library models of available network hardware and protocols. It
provides a virtual network environment that models the
behaviour of an entire network including its switches,
routers, protocols and specific application. The major
advantages of OPNET are that it is easier to use, user
Fig.8 Screenshot of OMNET++
friendly graphical user interface and have good quality of
documentation. Opnet’s modelling approach and graphical F. QualNet
user interface (GUI) enable researcher to develop new models
Quality Networking (QualNet) simulator is a highly
and devices with desired output results. OPNET can be used scalable, fastest simulator that supports the wired and wireless
as a research tool or as a network design and analysis tool [20]. network protocol. QualNet provides a comprehensive
environment for designing protocols, creating and animating
network scenarios, and analysing their performance. QualNet
consists of architect design, analyser, packet tracer, file editor
and command line interface. QualNet allows users to design
new protocol design, optimizing the existing models and
analyse the performance of networks. The main advantage of
QualNet is that it runs on both Windows and Unix/Linux
platforms [22].
Fig.7 Screenshot of OPNET
E. OMNET++
OMNeT++ is an object-oriented modular discrete event
network simulation framework in which active modules is
termed as simple modules and can be grouped into compound
modules. It also consists of hierarchically nested modules that
communicate by exchanging messages to each other and is
known as networks. Gates are the input and output interfaces
of modules. Fig 6 represents the base network NED file in
OMNET++. An OMNeT++ model consists of the following
parts:
NED language (.ned files) that describe the simple and
compound module with parameters, gates, connections
etc.
Message definitions (.msg files). OMNeT++ will
translate message definitions into C++ classes.
Module sources definition : These are C++ files,
with .h/.cc
Simulation kernel. This contains the code that manages
the simulation class and library.
User interfaces. OMNeT++ user interfaces are used in
debugging, demonstration and simulation [21].
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Fig.9 Screenshot of QualNet
VIII.
CONCLUSION
This paper provides a good environment for realizing the
VANET technology. It deals with VANET architecture,
routing protocols, characteristics, communication domain,
standards in VANET and various application areas. We
presented different simulators which helps researchers to
select the best simulator for VANET design. A lot of projects
and activities are implemented and running in Europe, US and
Japan. In Europe, the various VANET projects are upgraded
time to time according to new technologies like Car Talk,
NoW, Fleetnet, Pre-Drive and SeVeCom. In USA, two
representative industry/government projects are running i.e.
vehicle
infrastructure
integration,
Vehicle
Safety
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International Journal of Engineering Trends and Technology (IJETT) – Volume 21 Number 10 – March 2015
Communication Application Project. In Japan, the ongoing
projects are Advanced Safety Vehicle Program (ASV),
Smartway .
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