Decision making approach to prefer route repair technique in aodv routing protocol of manet

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 04 Issue: 02 | Feb-2015, Available @ http://www.ijret.org 9
DECISION MAKING APPROACH TO PREFER ROUTE REPAIR
TECHNIQUE IN AODV ROUTING PROTOCOL OF MANET
Shikha Patle1
, Purushottam Kumar2
1
Research Scholar, Dept. of CSE, Oriental University, Indore (M.P), India
2
Assistant Prof., Dept. of CSE, Oriental University, Indore (M.P), India
Abstract
MANET is a dynamic environment of mobile nodes and suffers link failure problem i.e. due to node mobility, loss of energy, node
failure etc. To overcome the broken link problem, initiated route repair mechanism. The suggested two route repair techniques
are used to repair the broken link of the network. Either the routes can be repaired by re-establishing a new route starting from
the source node or the routes can be repaired by the node that detects the link break along the path. The mechanism is proposed
to prefer route repair techniques on the basis of decision. According to this approach, the different route repair values are defined
on the basis of the active path of network and calculate the link break value of the network for finding in which location the link
break is occurring to initiate route repair mechanism. For implementation, apply the proposed approach on an AODV routing
protocol and check which route repair techniques are used. Simulate the results on the basis of different parameter i.e. sent data
packets, received data packets, dropped data packets and energy consumption.
Keywords: MANET, AODV Routing Protocol, Source Repair, Local Repair
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1. INTRODUCTION
The mobile ad-hoc network (MANET) is an infrastructure
less wireless ad-hoc network. It is self organized and
autonomous network of mobile nodes connected by wireless
links and does not depends on any centralized access point
or base station. Each node in the network may act as a router
or as a host and is free to move independently. In MANET
communication between mobile nodes is possible, when
they are in range of each other. The mobile nodes are
variable in nature and the network topology may be
configured in an arbitrary manner and change dynamically.
Thus the variable topology and node mobility may cause the
link failure problem. MANETs are being used in many
application scenarios such as: military and battlefield, search
and rescue operation, disaster recovery, public safety and
personal area network etc. [1].
MANET is a self creating network of mobile nodes and
suffers link failure problem due to many reasons such as:
node mobility, battery power off and node failure etc. Thus
one of the main challenging issues in MANET routing
protocol is how to deal with link failure problems and how
to repair this link in this situation [2].
Ad-hoc on demand distance vector routing protocol is used
to repair the broken link. It is an efficient reactive routing
protocol for Mobile Ad-hoc Networks with dynamic
topology and creates a path to the destination when required.
AODV also creates the routing table during data
transmission and maintain the routing table information
about the active route of the network [8]. AODV uses two
route repair approaches for repair the broken link. Either the
routes can be repaired by re-establishing a new route starting
from the source node is known as the source repair approach
or the routes can be repaired by the node that detects the link
break along the path is known as the local repair approach
[9]. Instead of the challenges is how to find that which route
repair technique is used to repair the broken link.
In this paper, we define a mechanism for selection of route
repair techniques on the basis of different route repair values
for different network scenario. The simulation result clearly
identifies that which route repair techniques are used in the
different cases of link break and the network performance is
calculated on the basis of different network parameters.
2. OVERVIEW OF AODV ROUTING
PROTOCOL
AODV Ad-hoc On Demand Distance Vector Routing
Protocol is an efficient reactive routing protocol for Mobile
Ad-hoc Networks with dynamic topology and creates a path
to the destination in an on demand manner by broadcasting
RREQ message. It also creates the routing table during
transmission and maintains the routing table information
about active route.
The working of the AODV routing protocol is described as
follows:
2.1 Route Discovery
Route discovery is initiated when the source node wants to
send data packets to the destination node and there is not
valid route information in the routing table. The source node
initiates the new route discovery process by broadcasting the
Route Request Message (RREQ) and waits for Route Reply
Message (RREP).

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Ad-hoc On Demand Distance Vector Routing Protocol uses
three types of message for route discovery.
2.2 Route Request Message
The source node forwards the RREQ message throughout
the network for finding a new active route to the destination.
The RREQ message contains the following fields <
source_add, source_sequence number, Broadcast_id,
destination_add, destination_sequence number and
hop_count >. The pair of source_add and broadcast_id
identifies the new RREQ message and broadcast_id is
incremented every time when the source node initiates a new
route request message. The destination node and neighbour
node respond the RREQ message by generating the RREP
message.
2.3 Route Reply Message
During the communication, if destination node or other
intermediate node receives the RREQ message then this
node respond by sending the corresponding Route Reply
Message (RREP) back to the source node and update the
routing table information. The RREP message contains the
following fields: < source_add, destination_add,
destination_sequence number, hop_count and life_time>.
Route Error Message: During the communication, if any
nodes are moved out of topology then the node generates the
Route Error Message (RERR) and sends back to the source
node and other intermediate nodes.
2.4 Route Maintenance
Every node broadcasts the hello message for local
connectivity and the freshness of the route.
2.5 AODV Route Repair Techniques
The suggested two routes repair techniques are used in
AODV routing protocols to repair the broken link as
described below:
2.5.1 Source Repair
The node that detect the link break and which is nearest to
the source node sends a route error message back to the
source node. Then the source node initiates new route
discovery process to destination node through rebroadcast
the route request message to other intermediate nodes of the
network. If the destination node receives a RREQ message
from source node, then this node responds the RREQ
message by resending the RREP message back to the source
node within the limited period of time and providing the
new route for transmission.
2.5.2 Local Repair
The node that detects the link break and which is located far
away the source node can locally try to repair the link for
initiating new route discovery to destination node for re-
broadcasting RREQ message. If the destination node
receives the new RREQ message then it generates the
corresponding RREP message for repairing node. The node
that initiates the local repair mechanism receives the RREP
message from destination node and provides the new route
for transmission.
3. RELATED STUDY
According to the paper [8] when the link break is occurring
in an active path and the node that detects the link break
locally tries to repair the route. This node broadcasts the
Forward Ant (F-Ant) message to other nodes for searching
active path to the destination. After one or two hops the F-
Ant found the required nodes that have an active route to the
destination. The next new node generates Backward Ant (B-
Ant) message and forward back to the repairing node within
the allotted time. The new route is available and this route is
used for transmission. If the repairing node does not receive
the B-Ant message within the time, it generates the REER
message back to the source node.
According to the paper [9] author defines the route repair
technique for Ad-hoc On Demand Distance Vector (AODV)
routing protocol. Author proposed a fixed and absolute
range of threshold parameter for the selection of which route
repair strategy is to choose.
The link break location parameter Llb as follows:
Llb= hop index of the broken link / total number of hops in
the path.
For examples: Author assumption 5 hop paths exist between
source node to the destination node and the link break has
happened by node 2.
In this scenario link break calculation is as follows:
Llb = 2/5= 0.4
Where: 2 defines the hop index of broken node
Total number of paths from source to destination is 5.
According to the approach, threshold (Tlr) value is 0.5
means that the link break has happened is more than half of
the path then local repair is invoked, otherwise source repair
will perform. Above example shows link break location is
0.4 and Threshold is 0.5, according the approach Llb is less
than Tlr (Llb < Tlr) so perform source repair.
In MANET one of the main challenging issues is routing,
due to the node mobility, dynamic changes of topology,
node power failure, bandwidth constrained its link failure
occurred [10]. In this paper author analyses the different On
Demand Routing Protocol on the basis of the packet delivery
ratio, throughput and delay to propose the solution of link
failure in different situations. If a source node moved out of
topology, then it finds a new route to the destination using
the new route discovery and updates the routing table
information. When link break has occurred by an
intermediate node, then the local repair procedure is used to
repair the path.

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4. PROPOSED METHODOLOGY
The mechanism is proposed to prefer route repair
techniques. According to the approach, calculate the link
break value of the network for finding in which location of
that network the link break is occurring to initiate route
repair mechanism.
The calculation of link break value for active route of the
network is defined as the ratio of:
Lbv = Hi / Total Sum of hops (Hs - Hd) /
Where: Lbv = Link break value
Hi = hops index value of the broken link
Hs - Hd= Sum of hops in the path
(Hs = Hop count of the source node and Hd = Hop count of
the destination node)
The hop index value of the broken link is simply counting
the number of hops starting from the source node to the
broken node and the sum of hops in the path is the total
number of hops from source to destination node along the
active route.
For example: Consider the network scenario for link break
calculation as shown below in figure 1 and figure 2.
Fig 1 Link break calculation
Assuming node B is moved out of topology due to mobility.
Then the link break value of this network is calculated as
follows:
/Lbv = Hi / Total Sum of hops (Hs - Hd)
Where: Hop index value of node B is 1
Total sum of hops in the path from source to destination is 7
Lbv = 1 / 7
Lbv = 0.142
Fig 2 Link break calculation
Assuming node D is moved out of topology due to mobility.
Then the link break value of this network is calculated as
follows:
// Lbv = Hi / Total Sum of hops (Hs - Hd) //
Where: Hop index value of node D is 3
Total sum of hops in the path from source to destination is 7.
Lbv = 3 / 7
Lbv = 0.428
In the proposed solution, the set of different route repair
values is also defined on the basis of the active path of
network i.e.
One fifth part of the path (1/5=0.2)
One fourth part of the path (1/4=0.25)
One third part of the path (1/3=0.33)
Half of the path (1/2=0.5)
After the half of the path (0.5), the broken link is always
repaired by the local repair approach because the half of the
path is already covered by the node and at that time if the
source repair approach is used then it takes more time for the
new route discovery process. That’s why after the half of the
path local repair approach is always preferred as well as in
this research work after half of the path any route repair
value is not defined.
5. SIMULATION AND RESULT ANALYSIS
The proposed approach is simulated in network simulator
(NS-2) considering some simulation parameters which are
given below.
5.1 Simulation Parameter
Table 1 shows the different network parameters and its
respective value.
Table 1 Simulation Parameter
Parameter Values
Number of nodes 7
Route repair values 0.2, 0.25, 0.33, 0.5

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Radio-propagation model Two Ray Ground
Antenna model Antenna/ Omni Antenna
Routing protocol AODV
Simulation area 1000 X 1000
Initial energy in Joules 100
Simulation time 30 seconds
Traffic type TCP
Channel type Channel/ Wireless Channel
Node speed 30m/s
6. RESULT ANALYSIS
The result of proposed approach is analyzed by considering
following network performance evaluation parameters.
6.1 Performance Metrics
The result is analyzed considering scenarios as shown above
in figure 1. The scenario is simulating for node 1, when in
the case of node 1 link is repaired by the source repair
approach. The graph of sent data packets, received data
packets, dropped data packets and energy consumption of
every node as generated.
6.2 First Scenario
Assume in the first scenario node 1 is moved out of topology
and the link is broken between node 0 and node 1, calculate
the link break value and apply the proposed approach. The
link break value is 0.142, which is less than the route repair
value 0.2, as the link is repaired by the source repair
approach and again data transmission is started from source
to destination.
6.3 Sent Data Packets
After repairing the link again data transmission starts from
source to destination and the total number of sending data
packets is 298 by all the nodes as shown below in the figure
3.
Fig 3 Sent data packets graph of node 1 for RRV 0.2
6.4 Received Data Packets
The total number of received data packets graph is shown below in the figure 4. This graph shows that total data packets received
by all nodes are 263.

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Fig 4 Received data packets graph of node 1 for RRV 0.2
6.5 Dropped Data Packets
During data transmission some data packets are dropped by node 0, node 1 and node 2 as shown below in the figure 5. This graph
shows that the total 35 data packets are dropped.
Fig 5 Dropped data packets graph of node 1 for RRV 0.2
6.6 Energy Consumption Graph
The energy consumptions graph of every node as shown below in the figure 6. The graph shows that before simulation every node
has energy of 100 joule and after the simulation every node consumes some amount of energy for sending RREQ and receiving
RREP message.

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Fig 6 Energy consumption graph of node 1 for RRV 0.2
7. PERFORMANCE EVALUATION
To investigate the performance of the AODV routing protocol, we use the packet delivery ratio for comparison between the base
paper result and the research work.
According to the paper [9], author use the range of fixed threshold value for selection of route repair strategy. The threshold (Tlr)
value is 0.5 means that the link break has happened is more than half of the path so local repair is invoked, otherwise source repair
will perform, but in the our proposed approach, we correctly identify the selection of route repair technique and improved the
packet delivery ratio.
After analysis the result of proposed approach and paper [9] approach, we found the following route repair selection strategies as
shown in the table 3.
Table 3 Route Repair Selection Method
Movin
g
Node
Proposed Approach Fixed Threshold Value
Proposed
Mechanis
m
Route
Repair
Techniqu
e
Approac
h
Route Repair
Technique
1
0.142 >
0.2
SR
0.166 >
0
LR
2
0.285 >
0.33
SR
0.33>
.25
LR
4
0.571 >
0.5
LR
0.66>
0.75
SR
Performance of AODV routing protocol on the basis of table 3 results as shown in the figure 7.

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Fig 7 Performance of AODV Routing Protocol
8. CONCLUSION
MANET does not provide the guarantee of delivering data
packets before the complete execution because the mobile
nodes frequently change its topology and leave the network
then the active routes are broken from source to destination.
Then the routing is one of the major challenging issues in
mobile ad-hoc network due to its variable nature. In this
research work, we make a study about the route repair
techniques for routing protocol in highly dynamic nature of
mobile ad-hoc networks. Define the different network
scenarios for simulation, where some mobile nodes change
their positions due to the node mobility. Then find out the
link break value of the network and define the different
route repair values on the basis of the active path of the
network for estimating which route repair technique is used.
Different route repair value is used for each scenario for the
selection of route repair mechanism and finds the optimal
result of route repair techniques.
Implementation and result analysis section clearly identify
that which route repair techniques are used in the different
cases of link break.
AODV supports two route repair approaches such as source
repair or local repair. Either the routes can be repaired by re-
establishing a new route starting from the source node is the
source repair approach or the routes can be repaired by the
node that detects the link break along the path is the local
repair approach.
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Decision making approach to prefer route repair technique in aodv routing protocol of manet

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Decision making approach to prefer route repair technique in aodv routing protocol of manet