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ISSN (Online) 2278-1021
ISSN (Print) 2319-5940
International Journal of Advanced Research in Computer and Communication Engineering
Vol. 4, Issue 5, May 2015
Copyright to IJARCCE DOI 10.17148/IJARCCE.2015.4585 388
Review on classification of different VANET
Protocols based on routing information
Ghanishtha Narang1, Yogesh Juneja2
Student, M. Tech (ECE), PDM College of Engineering, Bahadurgarh, India1
Assistant Professor (ECE), PDM College of Engineering, Bahadurgarh, India2
Abstract: Vehicular Ad-hoc Networks (VANETs) are the special class of Mobile Ad-hoc Networks (MANETs) with
high mobility and frequent changes of topology. It is a type of highly dynamic wireless network that can be formed
without the need for any pre-existing infrastructure which aims to improve the transportation system by integrating
sensors, wireless networks, GPS, 2G and 3G technologies with the Ad-hoc networks. Due to higher mobility of nodes
(vehicles), routing becomes the most challenging task in VANETs. A variety of research has been done on routing and
several protocols have been proposed with their implementation. As VANET (Vehicular Ad-hoc Network) research
field is growing very fast. It has to serve a wide range of applications under different scenarios (City, Highway). It has
various challenges to adopt the protocols that can serve in different topology and scenario. The main objective of
Vehicular Ad-hoc Networks is to build a robust network between mobile vehicles so that vehicles can talk to each other
for the safety of human beings. This paper deals with the study of classification of different Ad Hoc routing protocols
and their different routing techniques.
Keywords: VANET (Vehicular Ad-hoc Network), MANET (Mobile Ad-hoc Network), routing protocols, AODV,
AOMDV.
I. INTRODUCTION
Driving means changing location constantly. This means a
constant demand for information on the current location
and specifically for data on the surrounding traffic, routes
and much more. This information can be grouped together
in several categories. A very important category is driver
assistance and car safety. This includes many different
things mostly based on sensor data from other cars. We
could think of brake warning sent from preceding car and
collision warning, information about road condition and
maintenance, detailed regional weather forecast,
premonition of traffic jams, caution to an accident behind
the next bend, detailed information about an accident for
the rescue team and many other things. We could also
think of local updates of the cars navigation systems or an
assistant that helps to follow a friend’s car.
Another category is infotainment for passengers. For
example internet access, chatting and interactive games
between cars close to each other. The kids will love it.
Next category is local information as next free parking
space (perhaps with a reservation system), detailed
information about fuel prices and services offered by the
next service station or just tourist information about sights.
A possible other category is car maintenance. For example
online help from your car mechanic when your car breaks
down or just simply service information. So far no inter-
vehicle communication system for data exchange between
vehicles and between roadside and vehicles has been put
into operation. But there are several different research
projects going on [1] [2]. VANET is one of those.
In 1999, the Federal Communications Commission of the
United States allocated 75 MHz of bandwidth in the 5.9-
GHz band for the new generation of a nationwide
VANET. This wireless spectrum is commonly known as
the dedicated short-range communication (DSRC)
spectrum, which has been used for vehicle-to-vehicle
(V2V) and vehicle-to-infrastructure (V2I) communications
[3]. In August 2006, the European Telecommunications
Standards Institute has also allocated 30 MHz of spectrum
in the 5.8-GHz band for ITS [4].
IEEE 802.11p is a new upcoming standard using the
DSRC spectrum. It extends the IEEE 802.11 standard for a
high-speed vehicular environment, which covers the data
link layer and the physical layer of the wireless access in
vehicular environments (WAVE) protocol stack.
Meanwhile, IEEE 1609, which is a family of standards,
has been developed to define the five upper layers of the
WAVE. The latest version of IEEE 802.11p has been
approved and published in July 2010 [5].
IEEE 802.11p supports data communication between
vehicles, in turn supports Intelligent Transportation
Systems (ITS) applications. The channel capacity is 10
MHz, and there are two safety channel, one control
channel and six service channel. Radio communication
range is about 300 to 1000 meters and data rate is 6 to 27
Mbps [6 and 7]. This paper deals with study of different
types of routing protocols for VANET.
II. VANET ARCHITECTURE
An VANET system architecture consists of different
domains and many individual components as depicted in
Figure1 [8].
ISSN (Online) 2278-1021
ISSN (Print) 2319-5940
International Journal of Advanced Research in Computer and Communication Engineering
Vol. 4, Issue 5, May 2015
Copyright to IJARCCE DOI 10.17148/IJARCCE.2015.4585 389
Fig 1: VANET System Architecture [8]
In-vehicle domain
This consists of an on-board unit (OBU) and one or more
application units (AU) inside a vehicle. AU executes a set
of applications utilizing the communication capability of
the OBU. An OBU is at least equipped with a (short
range) wireless communication device dedicated for road
safety, and potentially with other optional communication
devices (for safety and non safety communications). The
distinction between AU and OBU is logical; they can also
reside in a single physical unit [9].
Ad hoc domain
An ad hoc domain is composed of vehicles equipped with
OBUs and road-side units (RSUs), forming the VANET.
OBUs form a mobile ad hoc network which allows
communications among nodes without the need for a
centralized coordination instance. OBUs directly
communicate if wireless connectivity exists among them;
else multi-hop communications are used to forward data
[9].
Infrastructure domain
The infrastructure consists of RSUs and wireless hotspots
(HT) that the vehicles access for safety and non-safety
applications. While RSUs for internet access are typically
set up by road administrators or other public authorities,
public or privately owned hot spots are usually set up in a
less controlled environment [9]. Easy way to comply with
the conference paper formatting requirements is to use this
document as a template and simply type your text into it.
III. AD HOC ROUTING PROTOCOLS
VANET has some special characteristics that distinguish it
from other mobile ad hoc networks; the most important
characteristics that differentiate VANETs from MANETs
are: high mobility, self-organization, distributed
communication, road pattern restrictions, and no
restrictions of network size. All these characteristics made
VANETs environment a very challenging task for
developing efficient routing protocols. We have a number
of ad hoc routing protocols for MANETs but when we are
dealing with a VANET then we require ad hoc routing
protocols which must adapt continuously according to the
unreliable conditions. MANET routing protocols are not
suited for VANET because it is difficult for MANET
routing protocols to find stable routing paths in VANET
environments. Many routing protocols have been
developed for VANET environments, which can be
classified in many ways, according to different aspects;
such as: protocols characteristics, techniques used, routing
information, quality of services, network structures,
routing algorithms, and so on.
VANET routing protocols can be classified into five
classes based on the routing protocols characteristics and
techniques used: topology-based, position-based,
multicast-based, broadcast, and cluster-based protocols
[10], [11], [12]. Also these routing protocols can be
classified according to the network structures, into three
classes: hierarchical routing, flat routing, and position-
based routing. Moreover, according to routing strategies
these protocols can be categorized into two classes:
proactive and reactive [14]. On the other hand geographic-
based and topology-based are the two categories according
to the routing information used in packet forwarding [13].
Based on the quality of services, there are three types of
protocols that are dealing with network topology
(hierarchical, flat, and position aware), that concerning
with route discovery (reactive, proactive, hybrid and
predictive), or based on the MAC layer interaction [15].
We are hereby considering the classification based on
routing information used in packet forwarding.
TOPOLOGY BASED ROUTING
Several MANET routing protocols have used topology
based routing approach. Topology based routing protocols
use link’s information within the network to send the data
packets from source to destination [17]. Topology based
routing approach can be further categorized into three
groups:
1. Proactive routing
2. Reactive routing
3. Hybrid routing
1. Proactive Routing
Proactive routing protocols are mostly based on shortest
path algorithms. They keep information of all connected
nodes in form of tables because these protocols are table
based [16]. Furthermore, these tables are also shared with
their neighbors. Whenever any change occurs in network
topology, every node updates its routing table. Strategies
implemented in proactive algorithms are Link-state
routing (e.g. OLSR) and distance-vector routing (e.g.
DSDV). The working details for proactive routing
protocols are as follows: Destination Sequence Distance
ISSN (Online) 2278-1021
ISSN (Print) 2319-5940
International Journal of Advanced Research in Computer and Communication Engineering
Vol. 4, Issue 5, May 2015
Copyright to IJARCCE DOI 10.17148/IJARCCE.2015.4585 390
Vector Routing (DSDV) [16] use Distance Vector shortest
path routing algorithm, it provides loop free single path to
the destination. DSDV sends two types of packets ―full
dump‖ and ―incremental‖. In full dump packets, all the
routing information is send while in incremental only
updates are send. It decreases bandwidth utilization by
sending only updates instead of complete routing
information. The incremental still increases the overhead
in the network, because these incremental packets are so
frequent that makes it unsuitable for large scale networks.
Optimized link state routing (OLSR) [16] maintains
routing information by sending link state information.
After each change in the topology every node sends
updates to selective nodes. By doing so, every node in the
network receive updates only once. Unselected packets
cannot retransmit updates; they can only read updated
information. Source-Tree Adaptive Routing (STAR) [16]
is another link State protocol. In STAR, preferred routes to
every destination are saved in each router. It reduces
overhead on the network by eliminating periodic updates.
There is no need of sending updates unless any event
occurs. This protocol can be suitable for large scale
networks but it needs large memory and processing
because it has to maintain large trees for whole network.
Proactive based routing protocols may not be suitable for
high mobility nodes because distance vector routing takes
much bandwidth to share routing information with
neighbors. Furthermore, size of the table is also quite big
while discussing about large networks and in case of link
state routing a lot of memory and processing may also be
required. As in VANET, nodes (vehicles) have high
mobility and moves with high speed. Proactive based
routing is not suitable for it. Proactive based routing
protocols may fail in VANET due to consumption of more
bandwidth and large table information.
1.1 Destination Sequence Distance Vector Routing
(DSDV)
This protocol is based on classical Bellman-Ford routing
algorithm designed for MANETS. Each node maintains a
list of all destinations and number of hops to each
destination. Each entry is marked with a sequence number.
It uses full dump or incremental update to reduce network
traffic generated by rout updates. The broadcast of route
updates is delayed by settling time. The only improvement
made here is avoidance of routing loops in a mobile
network of routers. With this improvement, routing
information can always be readily available, regardless of
whether the source node requires the information or not.
DSDV solve the problem of routing loops and count to
infinity by associating each route entry with a sequence
number indicating its freshness. In DSDV, a sequence
number is linked to a destination node, and usually is
originated by that node (the owner). The only case that a
non-owner node updates a sequence number of a route is
when it detects a link break on that route. An owner node
always uses even-numbers as sequence numbers, and a
non-owner node always uses odd-numbers. With the
addition of sequence numbers, routes for the same
destination are selected based on the following rules: 1) a
route with a newer sequence number is preferred; 2) in the
case that two routes have a same sequence number, the
one with a better cost metric is preferred.
2. Reactive Routing
On demand or reactive routing protocols were designed in
such a manner to overcome the overhead that was created
by proactive routing protocols. This is overcome by
maintaining only those routes that are currently active
[16]. Routes are discovered and maintained for only those
nodes that are currently being used to send data packets
from source to destination. Route discovery in reactive
routing can be done by sending RREQ (Route Request)
from a node when it requires a route to send the data to a
particular destination. After sending RREQ, node then
waits for the RREP (Route Reply) and if it does not
receive any RREP within a given time period, source node
assumes that either route is not available or route expired
[18]. When RREQ reaches the particular destination and if
source node receives RREP then by using unicasting,
information is forwarded to the source node in order to
ensure that route is available for communication. Reactive
routing can be classified either as source routing or hop-
by-hop routing. In source routing complete route
information from source to destination is included in data
packets. When these data packets are forwarded to other
intermediate nodes in the network, each node takes route
information from the data packet and stores it in the
header of data packet.
As a result, each intermediate node does not need to
update all route information in order to send packet to the
particular destination [16]. The main drawback of source
routing is that it may not be suitable for large scale
networks, where numbers of nodes are quite high and their
behavior is highly dynamic such as VANET. The first
reason is that as numbers of nodes are larger in large scale
ad hoc networks hence it may result in route failure. The
second reason is that as numbers of intermediate nodes are
increasing, thus network overhead may occur and route
information in the header of each node may also increase.
Hop-by-hop reactive routing is better than on demand
source routing as each data packet in it contains next hop
and destination addresses. Thus intermediate nodes from
source to destination contain the routing table information
in order to send data packet to a particular destination.
This can be quite helpful for accommodating sudden
changes in network topology. Thus when topology
changes nodes receives fresh routing table information and
selects new routes accordingly. As a result these selected
routes are now used to send data packets to destination.
These types of routing protocols continuously update their
routing information and carried knowledge of each
neighboring node Therefore this type of reactive routing
can be adopted in highly mobile ad hoc networks such as
VANET [16]. Many reactive routing protocols have been
proposed so far but in this section we briefly described
about Ad Hoc On Demand Distance Vector Routing
(AODV) and Ad-hoc On-demand Multipath Distance
Vector Routing (AOMDV). Moreover we check the
suitability of these protocols for VANET.
ISSN (Online) 2278-1021
ISSN (Print) 2319-5940
International Journal of Advanced Research in Computer and Communication Engineering
Vol. 4, Issue 5, May 2015
Copyright to IJARCCE DOI 10.17148/IJARCCE.2015.4585 391
2.1 Ad Hoc On Demand Distance Vector Routing-
AODV
Ad Hoc On Demand Distance Vector Routing (AODV) is
an example of pure reactive routing protocol. AODV
belongs to multihop type of reactive routing. AODV
routing protocol works purely on demand basis when it is
required by network, which is fulfilled by nodes within the
network. Route discovery and route maintenance is also
carried out on demand basis even if only two nodes need
to communicate with each other. AODV cuts down the
need of nodes in order to always remain active and to
continuously update routing information at each node. In
other words, AODV maintains and discovers routes only
when there is a need of communication among different
nodes. AODV uses an efficient method of routing that
reduces network load by broadcasting route discovery
mechanism and by dynamically updating routing
information at each intermediate node. Change in topology
and loop free routing is maintained by using most recent
routing information lying among the intermediate node by
utilizing Destination Sequence Numbers of DSDV.
2.2 Ad Hoc On Demand Multipath Distance
Vector Routing- AOMDV
The AOMDV [19] [20] [21] routing protocol is an
extension of AODV. It is a reactive (on-demand) routing
protocol as compared to proactive OLSR protocol. Thus
the route is calculated only when needed not in advance as
in OLSR protocol. Like AODV it also involves two
methods: route discovery and route maintenance. But it is
multi-path routing protocol as compared to single path
based AODV protocol. Therefore, it is suitable for highly
dynamic ad-hoc networks like vehicular ad-hoc networks
where network partitioning and route breakdown occur
very frequently. For dealing with such network scenario
AOMDV protocol determines multiple paths during the
procedure of route discovery. As a result in case of link
failure in the network there is no need to find the new
route every time due to availability of other routes while
the AODV protocol require an additional burden related
with the route discovery procedure to be invoked every
time to find the new route whenever route breaks causing
a delay in data transfer. So AOMDV is said to be an
improved form of AODV routing protocol.
3. Hybrid Routing
Hybrid routing combines characteristics of both reactive
and proactive routing protocols to make routing more
scalable and efficient [16]. Mostly hybrid routing
protocols are zone based; it means the number of nodes is
divided into different zones to make route discovery and
maintenance more reliable for MANET. Haas and
Pearlman [19] proposed a hybrid routing protocol and
named it as ZRP (Zone routing protocol). The need of
these protocols arises with the deficiencies of proactive
and reactive routing and there is demand of such protocol
that can resolve on demand route discovery with a limited
number of route searches. ZRP limits the range of
proactive routing methods to neighboring nodes locally,
however ZRP uses reactive routing to search the desired
nodes by querying the selective network nodes globally
instead of sending the query to all the nodes in network.
ZRP uses ―Intrazone‖ and ―Interzone‖ routing to provide
flexible route discovery and route maintenance in the
multiple ad hoc environments. Interzone routing performs
route discovery through reactive routing protocol globally
while intrazone routing based on proactive routing in order
to maintain up-to-date route information locally within its
own routing range [19]. The overall characteristic of ZRP
is that it reduces the network overhead that is caused by
proactive routing and it also handles the network delay
that is caused by reactive routing protocols and perform
route discovery more efficiently. The drawback of ZRP is
that it is not designed for such environments in which the
nodes behavior is highly dynamic and rapid changes in
topology such as VANET. In other words we can say this
routing protocol is specifically designed for such networks
where nodes are not highly mobile and network size is
depend on limited number of nodes. Pure proactive or
reactive routing protocols can be suitable to some extent in
a highly dynamic environment like VANET as compared
to Hybrid routing.
Fig 2: VANET routing protocols classification
IV. GEOGRAPHIC (POSITION ) BASED
ROUTING
In geographic (position-based) routing, the forwarding
decision by a node is primarily made based on the position
of a packet’s destination and the position of the node’s
one-hop neighbors. The position of the destination is
stored in the header of the packet by the source. The
position of the node’s one-hop neighbors is obtained by
the beacons sent periodically with random jitter (to
ISSN (Online) 2278-1021
ISSN (Print) 2319-5940
International Journal of Advanced Research in Computer and Communication Engineering
Vol. 4, Issue 5, May 2015
Copyright to IJARCCE DOI 10.17148/IJARCCE.2015.4585 392
prevent collision). Nodes that are within a node’s radio
range will become neighbors of the node. Geographic
routing assumes each node knows its location, and the
sending node knows the receiving node’s location by the
increasing popularity of Global Position System (GPS)
unit from an onboard Navigation System and the recent
research on location services (Flury, 2006; Li, 2000; Yu,
2004), respectively. Since geographic routing protocols do
not exchange link state information and do not maintain
established routes like proactive and reactive topology-
based routings do, they are more robust and promising to
the highly dynamic environments like VANETs. In other
words, route is determined based on the geographic
location of neighboring Figure 2 sub-classifies Geographic
routing into three categories of non-Delay Tolerant
Network (non-DTN), Delay Tolerant Network (DTN), and
hybrid. The non-DTN types of geographic routing
protocols do not consider intermittent connectivity and are
only practical in densely populated VANETs whereas
DTN types of geographic routing protocols do consider
disconnectivity. However, they are designed from the
perspective that networks are disconnected by default.
Hybrid types of geographic routing protocols combine the
non-DTN and DTN routing protocols to exploit partial
network connectivity.
IV. CONCLUSION
In this review paper we can conclude that MANET routing
protocols are not suited for VANET environment because
of their high mobility, distributed communication, road
pattern restrictions and self-organization and no
restrictions of network size. Also we have reviewed the
criteria on which different VANET protocols are
categorized. The classification based on routing
information used in packet forwarding is Topology based
routing and Geographic routing and this has been
discussed here.
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