As33259263

Tejal Arvind Sonawale, Dr Shikha Nema / International Journal of Engineering Research and
Applications (IJERA) ISSN: 2248-9622 www.ijera.com
Vol. 3, Issue 3, May-Jun 2013, pp.259-263
259 | P a g e
Comparison of Routing Protocol in MANETs
*Tejal Arvind Sonawale, **Dr Shikha Nema
*M.E(EXTC) V.E.S.I.T,Chembur Mumbai, India
**EXTC V.E.S.I.T,Chembur Mumbai, India
Abstract
AOMDV is widely used protocol these
days. But, its permissive for link failure. It takes
the necessary action after detecting the link
failure thus holding/queuing packets till new
route is discovered after detecting failure in
existing link.. Early Link Failure Detection-
AOMDV (ELFDAOMDV) keeps on monitoring
distance between two mobile nodes. As soon
distance between two nodes crosses specified
threshold then it sends a request to source node
to start discovering new route but continues to
transfer data packets as the link is still up. In
most of the cases, new route is discovered (if some
exists) before link failure. Then using the
intelligence data packets are automatically
shifted to this newly discovered route, thus
preventing the link failure. Hence, the algorithm
is named as Early Link Failure Detection -
AOMDV.
Keywords- Ad hoc networks; Routing protocols;
AODV, DSR, AOMDV.
1. INTRODUCTION
In contrast to infrastructure based wireless
networks, in ad hoc networks all nodes are mobile
are connected dynamically in an arbitrary manner. A
collection of mobile host with wireless network
interfaces may form a temporary network without
the aid of any established infrastructure or
centralized administration.
In the case where only two hosts, within the
transmission range, are involved in the ad hoc
network, no real routing protocol or routing
decisions are necessary. But in many practical ad
hoc networks, two hosts that wish to communicate
may not be close enough within wireless
transmission range of each other. These hosts could
communicate if other nodes between them
participated willfully to forward packets to the
destination or the next hop towards the destination.
So all nodes behave as routers and take part in
discovery and maintenance of routes to other nodes
in the network. Route construction should be done
with minimum overhead and bandwidth
consumption.
1.2 AD-HOC NETWORK DESIGN ISSUES
The Ad Hoc architecture has many benefits,
such as self-reconfiguration, ease of deployment,
and so on. However, this flexibility and convenience
come at a price. Ad hoc wireless networks inherit the
traditional problems of wireless communications,
such as bandwidth optimization, power control, and
transmission quality enhancement, while, in
addition, their mobility, multi-hop nature, and the
lack of fixed infrastructure create a number of
complexities and design issues that are specific to
mobile ad hoc networks.
 Infrastructure-less
 Dynamically Changing Network
Topologies
 Physical Layer Limitations
 Limited Link Bandwidth and Quality
 Variation in Link and Node Capabilities
 Energy Constrained Operation
 Network Robustness and Reliability
 Network Security
 Network Scalability
 Quality of Service

2 ROUTING PROTOCOL
Many protocols have been proposed for ad
hoc networks, all fall in any of the three sets, namely
Table-Driven, Source-Initiated On-Demand, and
Zone based.
2.1Table-Driven Routing Protocols
Table-driven routing protocols attempt to
maintain consistent, up-to-date routing information
from each node to every other node in the network.
These protocols require each node to maintain one or
more tables to store routing information, and they
respond to changes in network topology by
propagating updates throughout the network in order
to maintain a consistent network view. The areas in
which they differ and the number of necessary
routing-related tables and the methods by which
changes in network structure are broadcast
2.2 Source-Initiated On-Demand Routing
A different approach from table-driven
routing is source-initiated on-demand routing. This
type of routing creates routes only when desired by
the source node. When a node requires a route to a
destination, it initiates a route discovery process
within the network. This process is completed once a
route is found or all possible route permutations
have been examined. Once a route has been
established, it is maintained by a route maintenance

260 | P a g e
procedure until either the destination becomes
inaccessible along every path from the source or
until the route is no longer desired.
2.3 Zone Routing Protocol
ZRP divides its network in different zones.
That's the nodes local neighborhood. Each node may
be within multiple overlapping zones, and each zone
may be of a different size. The size of a zone is not
determined by geographical measurement. It is given
by a radius of length, where the number of hops is
the perimeter of the zone. Each node has its own
zone.
Advantage
 less control overhead as in a proactive
protocol or an on demand protocol

Disadvantage
 short latency for finding new routes
3 SECURITY IN AD HOC NETWORK
The security needs of Ad Hoc Network are not
different from the traditional networks
 Confidentiality
 Availability
 Integrity
 Authentication
 Non-repudiation
 Link Level Security
 Secure Routing
Wireless technologies are unequivocally among the
most rapidly progressing technology sectors. There
is a vast range of wireless technologies, applications
and devices, which are either already a substantial
part of our daily life or could play this role in future.
Wireless ad hoc networking is one of these
applications, which can potentially enhance our
abilities to solve real life challenges.
4. ROUTING Protocol Approach
4.1. Adhoc on demand Multi-path distance
vector(AOMDV)
Adhoc On-demand Multi-path Distance
Vector (AOMDV) [12] is an extension to the
AODV. The main difference lies in the number of
routes found in each route discovery. A little
additional overhead is required for the computation
of multiple paths. This protocol does not require any
special type of control packets but makes use of
AODV control packets with a few extra fields in the
packet headers. The AOMDV protocol computes
multiple loop-free and link-disjoint paths. There are
three phases of the AOMDV protocol. The first
phase is the Route Request, second is the Route
Reply and the third phase is the Route Maintenance
phase.
 Route Request:
The protocol propagates RREQ from source
towards the destination. Node S as in AODV
broadcasts multiple requests to its neighboring nodes
1 and 2. This means that request with same
sequence numbers are sent to the destination node.
They further broadcast the request to the other
neighboring nodes, which are further sent to the
destination node D.
 Route Reply:
The protocol establishes multiple reverse
paths both at intermediate nodes as well as
destination. Multiple RREPs traverse these reverse
paths back to form multiple forward paths to the
destination at the source and intermediate nodes. If
the intermediate nodes have the route defined for the
destination then they send the RREP to the source
node S. The protocol is designed to keep track of
multiple routes where the routing entries for each
destination contain a list of next hops together with
the corresponding hop counts. All the hop counts
have the same sequence number then the path with
the minimum hop count is selected and all the other
paths are discarded. The protocol computes multiple
loop-free and link-disjoint paths. Loop-freedom is
guaranteed by using a notion of “advertised hop
count”. Each duplicate route advertisement received
by a node defines an alternative path to the
destination. To ensure loop freedom, a node only
accepts an alternative path to the destination if it has
a lower hop count than the advertised hop count for
that destination. The advertised hop count is
generally the maximum hop count value possible for
a node S to reach a node D. If any value that is
received by the source S is greater than the
advertised hop count value then a loop is formed so
this RREP is discarded. The multiple RREPs are
received by the source via multiple paths and a
minimum hop count route is selected, the other
routes carrying a higher hop count value are
discarded.
Destination is the node where the packet is
destined to, the sequence number to maintain the
freshness of the routes, the advertised hop count that
avoids the formation of loops. The route list consists
of Hop Count required to reach a particular
destination, Next Hop is the next hop the packet is
supposed to take to reach the required destination,
Last Hop is the last hop taken to reach the
destination. If the packet is following the same path
then this value is same as the Next Hop or else it
changes and Expiration Timeout is the time for
which the path will exist. There are multiple entries
for a single destination but the routes that contain the
lowest hop count are only recorded in the routing
table and the other routes are discarded.

261 | P a g e
 Route Maintenance Phase:
The third phase is the Route Maintenance
Phase. This phase works in exactly same as AODV.
If the intermediate nodes are not able to receive a
response of the HELLO message then they broadcast
a Route Error message. After receiving this message
all the nodes that use the particular route to reach the
destination make this particular route as infinity and
inform the source node to run a fresh route
discovery.
There are two types of disjoint paths, one is
the node disjoint and the other is the link disjoint.
Node-disjoint paths do not have any nodes in
common, except the source and destination. The link
disjoint paths do not have any common link.
An AODV protocol is been developed
which develops route on-demand. The biggest
drawback of AODV is with respect to its route
maintenance. If a node detects a broken link while
attempting to forward the packet to the next hop then
it generates a RERR packet that is sent to all sources
using the broken link. The source runs a new route
discovery after receiving RERR packet. The
frequent route breaks cause intermediate nodes to
drop packets because no alternate path to destination
is available. This reduces overall throughput, packet
delivery ratio and increases average end-to-end
delay if there is high mobility. The other drawback is
that multiple RREP packets are received in response
to a single RREQ packet and can lead to heavy
control overhead. The HELLO message leads to
unnecessary bandwidth consumption.
The AOMDV is an extension to the AODV
protocol for computing multiple loop-free and link-
disjoint paths. The protocol computes multiple loop-
free and link-disjoint paths. Loop-freedom is
guaranteed by using a notion of “advertised hop
count”. Each duplicate route advertisement received
by a node defines an alternative path to the
destination. To ensure loop freedom, a node only
accepts an alternative path to the destination if it has
a lower hop count than the advertised hop count for
that destination. With multiple redundant paths
available, the protocol switches routes to a different
path when an earlier path fails. Thus a new route
discovery is avoided. Route discovery is initiated
only when all paths to a specific destination fail. For
efficiency, only link disjoint paths are computed so
that the paths fail independently of each other.
In AOMDV[12] RREQs reaching the node
may not be from disjoint paths, if RREQ is from one
common node one of the RREQ is discarded, this
messages implicitly provide knowledge about the
mobility and accessibility of their sender and
originator. for example, if node A is constantly
receiving messages initiated by another node B, this
implies that node B is relatively stationary to node
A. furthermore a valid route from node A to node B
is available either directly or through other nodes.
Instead of discarding repeated RREQs messages
node can perform additional computation on
available routing data and predict accessibility of
other nodes.
Now AOMDV[8] routing make use of pre-
computed routes determined during route discovery.
These solutions, however, suffer during high
mobility because the alternate paths are not actively
maintained. Hence, precisely when needed, the
routes are often broken. To overcome this problem,
we will go for link breakage prediction. Prediction
will be done only for multiple paths that are formed
during the route discovery process. All the paths are
maintained by means of periodic update packets
unicast along each path. These update packets are
MAC frames which gives the transmitted and
received power from which distance can be
measured. This distance can be used to predict
whether the node is moving inward or outward
relative to the previous distance value that is it give
the signal strength. At any point of time, only the
path with the strongest signal strength is used for
data transmission.
4.2. Early Link Failure Detection AOMDV
(ELFD-AODV)
AODV is widely used protocol these days. But, its
permissive for link failure. It takes the necessary
action after detecting the link failure thus
holding/queuing packets till new route is discovered
after detecting failure in existing link.
ELFD-AOMDV keeps on monitoring distance
between two mobile nodes. As soon distance
between two nodes crosses specified threshold then
it sends a request to source node to start discovering
new route but continues to transfer data packets as
the link is still up. In most of the cases, new route is
discovered (if some exists) before link failure. Then
using the intelligence data packets are automatically
shifted to this newly discovered route, thus
preventing the link failure. Hence, the algorithm is
named as Early Link Failure DetectionAOMDV.
Logic to monitor the distance between two mobile
nodes-
Source mobile node cannot know the
distance till destination mobile node or co-ordinates
of destination mobile node. So, source node cannot
calculate distance from source to destination. It
follows the reverse approach. Algorithm uses the
facts that each node knows the current co-ordinates
of self. While sending packets source nodes inserts
its own co-ordinates in the header. Destination node
receives the pakcet containing the source node
identification and co-ordinates of source node.
Destination node calculates the distance between
source and self as it knows its own co-ordinates and
co-ordiantes of source node which are received in
header. If this distance crosses threshold then
destination nodes informs the source node by

262 | P a g e
sending packet that link may break soon. As soon as
source node receives such packet, it starts looking
for new node.
5. Performance Metrics Comparison
 Packet Delivery Ratio – The ratio of total
number of data packets successfully received by
all the destinations to the total number of data
packets generated by all the sources.
 Throughput: Throughput is total packets
successfully delivered to individual destination
over total time.
SIMULATION RESULT AND ANALYSIS
Channel Type Wireless
Radio Propagation Model TwoRayGround
Network interface type
Phy/WirelessPhy
MAC type
Mac/802_11
Interface Queue Type
DropTail/PriQueue
Antenna Type OmniAntenna
Max Queue Length 50
No. Of Mobile nodes 06
Routing protocol-AOMDV/ELFDAOMDV
Mobility Random Way Point Model
Throughput: Measure how soon the receiver is
able to get a certain amount of data send by the
sender
Throughput in kbps = ((Total size of
packets transferred)/(StopTime -
StartTime)) * (8/1000)
Fig5.1 Throughput ELFD-AOMDV vs AOMDV
 Average throughput of AOMDV== 99.46 kbps
 Average throughtput ELFD-AOMDV
==190.52 Kbps
PACKET DELIVERY RATIO
Fig 5.2 Shows Packet Delivery Ratio of ELFD-
AOMDV and AOMDV
Packet Delivery Ratio = (No. Of Packets received
/No. Of Packets sent) * 100.
 Generated Packets=2400
 Received Packets=1118
 PDR (AOMDV)=46.5833%
 Generated Packets=2572
 Received Packets=2142
 PDR (ELFD-AOMDV)== 83.28%
6 CONCLUSION
In MANETS’s due to movement of the
nodes, network topology may change rapidly and
unpredictably over time. In this decentralized
network, discovering the route and delivering of data
becomes complicated. In mobility scenario already
developed routing algorithms like AOMDV gives
degraded results compared to ELFD-AOMDV
performance characteristics. ELFD-AOMDV came
up with the advantage of Increased Throughput and
Packet Delivery Ratio.
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