Bh4103368374

Vinay. P.Viradia Int. Journal of Engineering Research and Applications
ISSN : 2248-9622, Vol. 4, Issue 1( Version 3), January 2014, pp.368-374

RESEARCH ARTICLE

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OPEN ACCESS

Improved AODV Routing Protocol for MANET
Vinay. P.Viradia
Charotar University of Science and Technology, Gujarat, India
Abstract- Efficient protocols are used to forward data packets without much packet loss. Ad hoc on
Demand Distance Vector Routing Protocol (AODV) is one among the effective Reactive Routing
Protocol in MANET. The main causes for link break are mobility between nodes such as node failure
and node power off. Quality of Service (QoS) is one of the main issues for any network and due to
bandwidth constraint and dynamic topology of mobile ad hoc networks, supporting Quality of Service
(QoS) is extremely a challenging task. The objective of this paper is to enhance the network
performance of AODV, when frequent link failure in network due to mobility of the nodes in the
network.
This paper proposed a new protocol Enhanced AODV (E-AODV) which is a modified version of
AODV with enhanced packet delivery ratio and minimized end to end delay.
Index Terms- Ad Hoc Network, Routing Protocol, AODV, Packet delivery ratio, end to end delay.
I.

INTRODUCTION

Mobile Ad hoc Network (MANET)
[1,2] is a wireless i.e., access control and security.
Routing in MANET means the directed flow of data
from source to destination maximizing the network
performance.
The characteristics of these networks are summarized
as follows:
• Communication via wireless Network.
• No centralized controller and infrastructure.
• Dynamic network topology.
• Frequent routing updates.
• Nodes can perform the roles of both hosts and
routers.
• Intrinsic mutual trust.
• Some of the applications of MANETs are
• Disaster relief operations.
• Defense Development.
• Urgent Business meetings.
• Mine site operations.
Network Simulator (NS-2) is an event driven,
object oriented network simulating tool, very
much used by the researchers,
professors
and
students. Simulation is the process of creating a
model with its behavior. There are numerous
network simulating tools available such as NS-2,
GloMoSim, OPNET, QualNet, etc. NS-2 is the
outperforms among all the other tools. The Routing
protocols of MANET such as DSDV, DSR, AODV is
implemented using NS-2 and it’s available as free
open source programs. In this paper, AODV protocol

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is considered and its network performance is
enhanced by E-AODV.
The rest of the paper is organized as follows: Section
II gives an overview of Routing Protocols of
MANET and Section III describes the Reactive
Routing Protocol AODV, Section IV discusses
the proposed topology used for E-AODV, Section
V describes NS-2 implementation of EAODV, section VI discusses about simulation
results and analysis and final network of collection of
independent mobile nodes that Section VII discusses
about
conclusion
derived
from
the can
communicate to each other via radio waves. The
mobile nodes that are in radio range of each
other can directly communicate, whereas others
needs the aid of intermediate nodes to route their
packets. These networks are fully distributed, and can
work at any place without the help of any
infrastructure. This property makes these networks
highly flexible and robust. The dynamic change in
MANET topology [3, 4] makes routing as a
challenging task, as the existing path is rendered
inefficient and infeasible. The major issues for
mobile ad hoc networks are medium access control
(MAC), routing, security and quality of service
provisioning. The paper addresses the routing
problem in a mobile ad hoc network without
considering the other issues, Implemented results.

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II.

ROUTING PROTOCOLS FOR
MANET

Routing protocols in ad hoc networks vary
depending on the type of the network [3, 4, 5].
Typically, ad hoc network routing protocols are
classified into three major categories based on the
routing information updated mechanism. They are
proactive (table driven routing Protocols), reactive
(on-demand routing protocols) and hybrid routing
protocols. In addition, protocols can also be classified
according to the utilization of specific resources,
such as power aware routing protocol and load
aware routing protocols and so on.
A. Proactive Routing Protocols
Routes to all destinations are maintained
by sending periodical control messages. There is
unnecessary bandwidth wastage for sending control
packets. Proactive routing protocols are not suitable
for larger networks, as it needs to maintain route
Information every node’s routing table. This
causes more overhead leads to consumption of
more bandwidth. Ex: DSDV [10, 11].
B. Reactive Routing Protocols
Routes are found when there is a need (on
demand). Hence, it reduces the routing overhead. It
does not need to search for and maintain the routes
on which there is no route request. Reactive routing
protocols are very pleasing in the resourcelimited environment. However the source node
should wait until a route to the destination is
discovered. This approach is best suitable when the
network is static and traffic is very light. Ex: DSR,
AODV. [15, 16].
C. Hybrid Routing
The Ad Hoc network can use the hybrid
routing protocols that have the advantage of both
proactive and reactive routing protocols to balance
the delay and control overhead (in terms of control
packages). The difficulty of all hybrid routing
protocols is the complexity of organizing the
network according to network parameters. The
common disadvantage of hybrid routing protocols is
that the nodes that have high level topological
information maintains more routing information,
which leads to more memory and power
consumption.
D. ANALYSIS
There are two approaches to evaluate
routing protocols:
• Network Environment Parameters like
network size, connectivity, mobility, link
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capacity etc.
General Performance Metrics of Routing
Protocols like
message delivery ratio, control overhead, hop count,
end to end delay, etc. [13,14]
In this paper packet delivery ratio and average end
to end delay performance parameters are
considered.
•

III.

AODV PROTOCOL

AODV protocol allows mobile nodes to
quickly obtain routes for new destinations, and it
does not require nodes to maintain routes to
destinations
that
are
not
in
active
communication. Also, AODV routing permits
mobile nodes to respond link breakages and
changes in network topology in a timely manner.
The main objectives of the protocol is quickly and
dynamically adapt to changes of conditions on the
network links, for example, due to mobility of
nodes the AODV protocol works as a pure ondemand route acquisition system. Control messages
[8, 9] used in
AODV are:
• Route Request Message (RREQ)
• Route Reply Message (RREP)
• Route Error Message (RERR)
• Route Reply Acknowledgment (RREP-ACK)
Message
• HELLO Messages
A) Route discovery:
When a source node desires to send a
message to some destination node, and doesn’t
have a valid route to the destination, it initiates a
path discovery process to locate the other node. It
broadcasts a route request (RREQ) control packet to
its neighbors, which then forward the request to
their neighbors, and so on, either the destination or an
intermediate node with a new
route to the
destination is located. The AODV protocol utilizes
destination sequence numbers to ensure that all routes
contain the most recent route information. Each node
maintains its own sequence number. During the
forwarding process the RREQ intermediate nodes
record the address of the neighbor from which the
first copy of the broadcast packet is received in their
route tables, thereby establishing a reverse path. Once
the RREQ reaches the destination or an intermediate
node with a fresh enough route, the destination or the
intermediate node responds by unicasting a route
reply (RREP) control packet back to the neighbor
from which first received the RREQ [6,7].
B) Route Maintenance
A route discovered between a source node
and destination node is maintained as long as needed
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by the source node. The destination node or some
intermediate node moves, the node upstream of the
break initiates Route Error (RERR) message to the
affected
active
upstream
neighbors/nodes.
Consequently, these nodes propagate the RERR to
their predecessor nodes. This process continues until
the source node is reached. When RERR is received
by the source node, it can either stop sending the data
or reinitiate the route discovery mechanism by
sending a new RREQ message if the route is still
required[9,10].

IV.

PROPOSED METHODOLOGY

In this section new methodology is
described to show the difference between the EAODV and the AODV routing protocols during
transmission with the following simple topology.
There are four nodes in this network, and the initial
topology is a grid and the method shown in Table-1.
According to the scenario, at the beginning of the
transmission of nodes, the two pairs are not
interference with each other. At 10s, Node 2 moves
towards the direction of Node 0 with a speed of 10
m/s. The distance between Node 0 and Node 2
becomes smaller and smaller, and at time 15 s, these
two nodes begin to be in each others carrier sensing
range, which means that these two nodes begin to
share the same channel. The maximum bandwidth of
the channel is around 3.64 Mbps. In AODV, where
there is no QoS requirement, when Node 2 is in the
interference range of Node 0,
traffics are kept on and some packets are lost
during the transmission, whereas, in E-AODV, the
QoS is ensured. When the promised data rate cannot

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Table 1: Scenario descriptions for proposed
topology
In the topology there were 30 nodes and the
simulation environment was as described in Table1.
The area size is 870 m * 870 m, and 30 nodes are
in this area. 50 s is added at the beginning of
each simulation to stabilize the mobility model.
Every simulation runs 500 s in total. Each data
point in the results represents an average of ten runs
with same traffic models but different randomly
generated mobility scenarios. For fair comparisons,
same mobility and traffic scenarios are used in both
the AODV and the E-AODV routing protocols.

V.

SIMULATION TRAFFIC
PATTERN

The Random Waypoint model provided by
NS2 is used as the mobility model [12]. The traffic
type in the application layer is CBR with packet size
of 512 bytes and in transport layer User Datagram
Protocol (UDP) is used. The traffic pattern that used
in the simulation is shown in Table 2. It is the
same as what the Reference [4] uses.
Table 2: Simulation traffic pattern

Setting the traffic flow in such a manner aims at
greater interference impact when sessions overlap.
The source node and the destination node of each
traffic flow are chosen by using function cbrgen.tcl
randomly.

VI.

SIMULATION RESULTS AND
ANALYSIS

For comparing various routing protocols
using UDP transport layer protocol,
two
performance metrics Average End to End delay and
Packet Delivery Ratio are used to evaluate the
performance of the AODV and the E-AODV
routing protocols.
be satisfied any more, traffic of Node 2 is stopped at
once. From this case, we could see that the E-AODV
achieved the function of ensuring the QoS not only at
the route discovery stage, but also during the
transmission. Once the QoS is not satisfied, the
traffic is stopped [8, 9].
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6.1 Data Rate
In this set of simulations, a group of data
rates ranging from 50 kbps to 1800 kbps is applied.
The mobility scenario is with a pause time of 30
seconds and the maximum node speed is 10 m/s.
Three parameters defined above are calculated. The
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results are shown in the following figures (figure. 1
and figure.2).
6.1.1 Packet Delivery Ratio
From figure.1 we see that, either we use
the E-AODV routing protocol or the AODV
routing protocol, the packet delivery ratio
decreases with the increase of the data rate of
traffic flows.

Fig. 1: Packet delivery ratio with different data rates

Fig. 2: Average End to End delays with different
data rates
That is because the increasing data rate of
flows increases traffic in the network. When the
maximum throughput of nodes cannot satisfy the ongoing traffic, queues at nodes begin to be

full; the packets in the end of queues of nodes are
dropped both at source nodes and at intermediate
nodes.
The packet delivery ratio with the Ewww.ijera.com

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AODV always lower than the AODV because the
source node takes ore time to find a suitable route in
E-AODV and during this period of time, the source
which keeps on sending packets from the
application layer of the node, it cause drops of
packets at the end of the queue when the queue is
full. Also, the traffic session can be paused anytime
when the local available data rate of nodes in the
path is not satisfied during the transmission in the
E-AODV routing protocol. There are strict
requirements
in
terms
of
data
rate for traffic flow with access admission control.
When data rate increases from 1500 kbps to 1800
kbps, only paths with hop count 1 or 2 can be
admitted. As a result, there is more decrease
in PDR with the E-AODV than in AODV when
the data rate increases from 1500 kbps to 1800 kbps.
It is hard to explain why the PDR increase in AODV
when data rate increases from 1500 kbps to 1800
kbps .
For the above reason, the packet delivery ratio
with the E-AODV routing protocol is lower than
the one with the AODV routing protocol is that EAODV routing protocol has more restrictions to
the route for transmission. Actually, the packets
which are not delivered and dropped at the source
node because of the delay for searching for a more
suitable route in the E-AODV routing protocol
should be dropped. The reason is that if
these packets are sent, and the route chosen is not
satisfying the requirements, packets have more
probability to be dropped at the intermediate node or
packets may arrives at the destination node
late because of the long duration of wait at the
intermediate node. In other words, the E-AODV
routing protocol also helps to prohibit the packets,
which have more probability to be dropped during
the transmission or that, arrived the destination node
late, to be transmitted on the network. It helps to
save the data rate as well.
6.1.2 Average end to end delay
From figure.2, it can be seen that AODV
routing protocol performs better than E-AODV
routing protocol when data rate is low (below 600
kbps). The E-AODV routing protocol got higher
average end to end delay at the low data rate than
the AODV because intermediate nodes are not
allowed to perform local route repairs in case of
link failures with the E-AODV routing protocol,
thus, there is higher route recovery latency which
results in higher end-to-end delay compared with
the AODV routing protocol at low data rate.
Another reason could be that, with the EAODV routing protocol, the number of transmitted
routing packets is larger than the number of routing
packets transmitted in the AODV routing protocol.
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In the E-AODV routing protocol, routing packets
including Hello messages which have higher
priority always transmitted firstly and data packets
are queued nodes. With the AODV routing protocol,
when the traffic is low in the network, no matter
which route the traffic flow chose, the route chosen
can provide enough data rate at most of the time. As
a result, the end to end delay with the AODV routing
protocol is not high and can be lower than the EAODV routing protocol at low data rate. If
we can take more time for simulation for each
data rate comparatively accurate results can be
found. For these above reasons, end to end delay in
E-AODV is higher than the AODV at low data rate.
The average end to end delay of the E-AODV is
always below 240ms ,whereas, the end to end
delay of the AODV increases badly when the data
rate of each traffic flow increases from 600 kbps to
1200 kbps. It shows that networks with the EAODV routing protocol can provide lower end to
end delay for traffic flows than the AODV since the
E-AODV always choose to find a route with
satisfying data rate. During the transmission, the
QoS of the traffic is monitored in the E-AODV
routing protocol. Once the QoS is not satisfied as it
promised, the traffic stopped. All in all, with the EAODV routing protocol, the average end to end
delay is low even the load on the network
increases to very high which is not true for the
AODV routing protocol. This performance is very
significant for real time traffic transmissions.
6.2 Maximum Node Moving Speed
In the following simulations, the data rate
is fixed at 1200 kbps. The maximum node moving
speed is increased to see the behaviors of the
AODV and the E-AODV in a fairly high
mobility mode. Maximum node moving speed is
changing in the range 1 m/s to 20 m/s. The results
are shown in terms of average end to end delay,
packet delivery ratio and normalized routing load
shown in figure:3 and figure:4.
6.2.1 Packet Delivery Ratio
In figure. 3 with low max moving speed the
packet delivery ratio in E-AODV is higher than the
AODV but with the increase of mobility speed the
performance is lower than AODV. When the
maximum moving speed is up to 20 m/s, almost half
of the packets are dropped in E-AODV. The
reason that why more packets are dropped in EAODV and how they are dropped has been explained
in the previous part of this section.

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To sum up, the E-AODV routing protocol does
decrease end to end delay significantly when the data
rate of traffic flows is high.

VII.

Fig. 3: Packet delivery ratio with different Max.
moving speeds.

CONCLUSION

In this paper, the description is given about
the importance of QoS( in terms of packet delivery
ratio and average end to end delay) routing in
Mobile Ad-Hoc networks, challenges came
across, and the approach taken. After observing the
simulation and analyzing the data, it is found that
packets could get less end to end delay with a QoS
based routing protocol when the traffic
on the network is high. This low end to end delay is
meaningful for real time transmissions. When the
traffic is relatively high on the network, not all the
routes that are found by the AODV
routing protocol have enough free data rate for
sending packets ensuring the low end to end delay of
each packet. As a result, the E-AODV protocol
works well and shows its effects when the
traffic on the network is relatively high. People who
work on the area of ad hoc networks with the aim of
improving QOS in terms of reduced the average end
to
end
delay
and
enhanced
packet
delivery ratio for ad hoc networks can get benefit
from this E-AODV protocol.
In the further work other additional network
parameters will be considered.

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Fig. 4: Average end to end delay with different
Max. moving speeds
6.2.2 Average end to end delay
As shown in figure:4, with the increase of
the maximum moving speed, the average end to
end delay does not increase much in E-AODV as
compared with the AODV routing protocol, it means
that, this protocol is quite suitable for scenarios
with different moving speeds.
In comparison, with the AODV routing
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obviously seen that, the end to end delay in EAODV is always much lower than the one in the
AODV routing protocol. The low end to end delay
of packets ensures the on time transmissions
required by real time traffic transmissions.
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