International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 1- May 2016
Optimized Adhoc On demand Distance Vector
(O-AODV)
Prof. Vallabh G Patel1, Prof. Nishant P Makwana2
1
Assistant Professor, Department of IT, Government Engineering College, Bhavnagar ,Gujarat, India
2
Assistant Professor, Department of CE, Government Engineering College, Bhavnagar ,Gujarat, India
Abstract—MANET using AODV (reactive algorithm)
Routing Protocol has issue related to flooding RREQ
Packets to establish path from source to destination.
Such flooding of RREQ packet creates unnecessary
large traffic. Ultimately path establishment overhead
increases end to end delay and decrease packet
delivery ratio for data packets. To solve issue of
broadcasting of RREQ packets in AODV, we propose
O-AODV (Optimized Adhoc On demand Distance
Vector) algorithm. In this proposed algorithm, we
define prime area for forwarding RREQ packet.
Whenever source wants to send data packets to
particular destination, it first sends RREQ packet to
its neighbor nodes (Intermediate nodes). If
intermediate node is inside prime area, then only it
will forward RREQ packet to others intermediate node
until it reaches final destination. Prime area is circle
constructed with help of positions of source,
destination and intermediate nodes. Here instead of
blind flooding of RREQ packet, they are flooded inside
prime area only. So O-AODV provides better
performance (low end to end delay and high packet
delivery ratio). We are also using load balancing
during path construction. Here load balancing means
keep highly loaded nodes away from being part of new
paths. So O-AODV is better for routing in MANET.
Keywords— MANET, AODV, RREQ Flooding, Load
Balancing, Prime Area, O-AODV.
I. INTRODUCTION
A MANET is a collection of mobile nodes that can
communicate with each other without the use of
pre-defined
infrastructure
or
centralized
administration. Due to self-organize and rapidly
deploy capability, MANET can be applied to different
applications inc luding battlefield communications,
emergency -relief scenarios, public meeting, virtual
class room and other security-sensitive computing
environments. There are some major issues involving
in MANET such as Flooding of RREQ Packets,
Routing, multicasting/broadcasting, Location service,
Mobility management, Power management, Security,
QoS/multimedia. The routing protocol is required
whenever the source needs to transmit and delivers the
packets to the destination. Many routing protocols
have been proposed for mobile ad hoc network. This
paper is about performance improvement of AODV
ISSN: 2231-5381
in-terms of End-to-End Delay and Throughput (QoS
parameter) with our approach-AODV. Section II gives
an AODV Overview. Section III describes Location
Based Approach of AODV protocol. Section IV Load
Balancing in AODV. Section V Problem Identification
in AODV. Section VI Proposed Approach-AODV.
Section VII O-AODV Algorithm and implementation.
Section VIII Simulation and Result of O-AODV.
Section IX Conclusion & Future Work.
II. OVERVIEW OF AODV
AODV, source node and intermediate nodes
store the next hop information corresponding to
each flow for data packet transmission.
 On-demand routing protocol, the source
code floods the RouteRequest (RREQ) packet
in the network when a route is not available for
the desired destination.
 It may obtain multiple routes to different
destinations from a single RouteRequest.
AODV uses a destination sequence-number
DestSeqNum to determine an uptodate path to
the destination.
A node updates its path information only if the
DeptSeqNum of the current packet received is
greater than the last DeptSeqNum stored at the
node.
 A RouteRequest carries source identifier
(SrcID), the destination identifier (DestID), the
source
sequence
number
(SrcSeqNum),destination sequence number
(DestSeqNum),
the broadcast identifier
(BcastID), time to live (TTL) field.
 DestSeqNum indicates the freshness of the
route that is accepted by the source.
 Validity of a route at the intermediate node
is determined by comparing the sequence
number at the intermediate node with the
destination
sequence number in the
RouteRequest packet.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 1- May 2016
Figure 2.1 Basic Distance progress
Figure 1.1 Route Request
(RREQ)
Positive and negative progress: C, A, F
are in forward direction, with a positive progress;
nodes B and E are in backward direction, with a
negative progress. In the compass routing method
(referred here to as the DIR method), the source or
intermediate node A uses the location information of
the destination D to calculate its direction. Then the
message m is forwarded to the neighbor C, such that
the direction AC closest to the direction AD. This
process repeats until the destination is, eventually,
reached. Consider the network on Fig. 2.2, where the
radius is equal to edge EF. The direction AC is closest
to direction AD among candidate directions AS, AB,
AC, and AP. The path selected by DIR method is
SACJKLMND.
Figure 1.2 Route Reply (RREP)
III. LOCATION BASED APPROACH [1]
We can distinguish two main classes of existing
location based routing schemes:
(a) Basic Distance, Progress, and Direction Based
Methods
(b) Partial Flooding
(a) Basic Distance, Progress, and Direction
Based Methods
Given a transmitting node S, the progress of a
node A is defined as the projection onto the line
connecting S and the final destination, of the distance
between S and the receiving node. A neighbor is in
forward direction if the progress is positive (for
example, for transmitting node S and receiving
nodes A, C and F in Fig. 2.1); otherwise it is said to be
in backward direction (e.g. nodes B and E in Fig. 2.1).
Basic Distance, Progress, And Direction Based
Methods use these concepts to select among neighbors
the next routing step. Schemes as the Random
Progress Method, Most Forward within Radius,
Nearest Forward Progress and compass routing , fall
in this class.
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Figure 2.2 DIR
(b) Partial Flooding
In directional flooding-based routing methods, a
node A transmits a message m to several neighbors
whose direction (looking from A) is closest to the
direction of
destination D. In order to control
flooding effect, flooding based method require nodes
to memorize past traffic, to avoid forwarding the same
message more than once.
DREAM belongs to this class. Flooding can be
partial because it is directed towards nodes in a limited
sector of the network because it is stopped after a
certain number of hops (e.g. in flooding GEDIR
family of schemes). Moreover, partial flooding can be
used only for path discovery purpose (e.g. LAR) or for
packet forwarding (e.g. DREAM).
DREAM protocol, m is forwarded to all
neighbors whose direction belongs to the selected
range, determined by the tangents from A to the circle
centered at D and with radius equal to a maximal
possible movement of D since the last location update.
DREAM algorithm is a proactive protocol that uses a
limited flooding of location update messages.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 1- May 2016
IV. LOAD BALANCING[2]
2.2.1 Delay-based Load-Aware On-demand
Routing (D- LAOR)
D-LAOR Protocol for Mobile Ad hoc
Networks‖, which uses the optimal path based on the
estimated total path delay and the hop count as the
route selection criterion. The delay of each node is
calculated based on packet arrival time and packet
transmission time.
The average delay at node includes the
queuing contention and transmission delays. Then
total path delay is calculated by sum of node delay
from source to destination.
2.2.2 Associativity Based Routing (ABR)
Route is selected based on nodes having
associativity states that imply periods of stability.
ABR defines a new metric for routing known as the
degree of association stability. It is free from loops,
deadlock, and packet duplicates. In ABR, a route is
selected based on associativity states of nodes. In this
manner, the routes selected are likely to be long-lived
and hence there is no need to restart frequently,
resulting in higher attainable throughput. Load
balancing is employed during the route discovery
phase. A source first sends a broadcast query (BQ)
message in search of nodes that have a route to the
destination. All intermediate nodes receiving the
query append their addresses and associativity ticks
with their neighbors along with the route relaying load
(RRL) information into the query packet. In this way
the query packet arriving at the destination node
contains associativity ticks and relaying load
information of nodes along the route. The destination
node thus knows, at an appropriate time after
receiving the first BQ packet, all the possible routes
and their qualities. ABR then considers acceptable
routes with nodes that do not exceed the maximum
allowable RRL. From among the acceptable routes,
the destination node chooses the most stable route and
sends a reply back to the source node via the route
selected.
If multiple paths have the same overall degree
of association stability, the route with the minimum
number of hops is selected. In this way ABR avoids
congested nodes.
2.2.3 Dynamic Load Aware Routing (DLAR)
―Dynamic Load Aware Routing in Ad Hoc
Networks‖, it uses the number of packets buffered in
the interface as the primary route selection criteria.
There are three algorithms in selecting the least loaded
route.
DLAR scheme 1 adds the routing load of each
intermediate node and selects the route with the
least sum. If there is a tie, the destination selects the
route with the shortest hop distance. DLAR scheme
2 uses the average number of packets buffered at each
intermediate node along the path. DLAR scheme 3
considers the number of congested intermediate nodes
as the route selection metric. In DLAR protocol only
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the sum of the lengths of instantaneous interface
queues are considered but the instantaneous queue
length doesn’t give exact traffic at a node.
2.2.4 Weighted Load Aware Routing (WLAR)
―Design and Simulation Result of a Weighted
Aware Routing (WLAR) Protocol in Mobile Ad Hoc
Network‖, is an extension of AODV, it distribute the
traffics among ad hoc nodes through load balancing
mechanism. They have used total traffic load, as a
route selection metric. Queue size and sharing nodes
(those avg. queue length is greater than threshold
value) are used to find the total traffic. The total traffic
is the product of average queue size and number of
sharing nodes.
V. PROBLEM IDENTIFICATION IN AODV [2]
MANET is consists of many mobile nodes
and nodes are moving in specific area in random
fashion. Each Node is moving in random direction and
with different speed independently reference to other
nodes. In such mobilized nodes environment AODV
(Ad hoc On demand Distance Vector) algorithm is
efficient compare to other algorithm DSR and DSDV.
AODV is reactive algorithm, means it establishes path
only whenever there is requirement of path to send
data packets. It uses flooding of RREQ (Route
Request Packet) to establish path from source to
destination. This situation is shown in fig. 3.1. Such
flooding of RREQ packet creates unnecessary large
traffic. So there is wastage of bandwidth in path
establishment and this condition creates adverse effect
on data traffic. Ultimately path establishment
overhead increases end to end delay and decrease
packet delivery ratio for data packets.
Figure 3. RREQ packet broadcasting
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International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 1- May 2016
PROBLEM DEFINATION
I2
“We proposed Optimized AODV (O-AODV)
in which we are using limited flooding of RREQ and
node’s packet queue (buffer) based load balancing. By
doing this data packets end to end delay decreases
and throughput of network increases compare to
AODV.”
Intermediate
Nodes
I1
I3
Source Node
Destination Node
VI. PROPOSED APPROACH : O-AODV
In O-AODV we proposed two improvements, one
is related to RREQ packet flooding area and second is
load balancing based on node’s packet queue length.
(i) Whenever any node have data to send to other node
in MANET, Then that node is called source node and
other node is called as destination node. Before
transmission of actual data, there is path establishment
is required between source and destination.
In such situation source node generates
RREQ (route request) packet and broadcast that
packet to all neighbor nodes. Then each neighbor node
rebroadcast that RREQ packet. When destination gets
this RREQ packet, it generates route reply packet
(RREP) and sends RREP to source node by unicast.
Such broadcasting of RREQ packets generates
broadcast packet storms and creates adverse effect on
data traffic. This condition occurs multiple times
during each new connection establishment.
To solve this issue, O-AODV use prime circle
area to establishment connection and RREQ packets
broadcast. Prime Circle Area (PCA) is very small
compare to whole network area. Prime area defined by
circle with radius equal to half distance between
source node and destination node and with centre
point of circle is midpoint of line connecting source
node and destination.
Such Prime Circle Area (PCA) is shown in
following fig.4.1. Source node S generates RREQ
packet and it is forwarded by I1 and I3 nodes.
Whereas I2 node will drop the RREQ packet as node
I2 is outside the PCA. To define PCA we are using
positions/locations of Source node, destination node
and intermediate node. We assumed that every node
equipped with small wireless GPS (Global Positional
System) antenna. Also there exists positional control
system (PCS) to provide location of each node. Such
algorithms are categorized as global routing
algorithm.[1]
ISSN: 2231-5381
S
D
O(xmid,ymid)
(x2,y2)
(x1,y1)
Figure 4. Prime Circle Area
(ii) Second improvement is about load balancing.
During path establishment if we select intermediate
node which is used by other old paths and heavily
loaded for data packet forwarding task, that
intermediate node’s packet queue will start dropping
of packets when it is full and there is loss of data.
To avoid such situation O-AODV exclude node
which packet queue is full more than threshold value
during route discovery.
So we can say that intermediate node forwards the
RREQ packet if and only if intermediate node inside
PCA and its packet queue length is less than threshold
value.
VII.
O-AODV ALGORITHM
To find route for sending data packets.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 1- May 2016
1.
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If Source node(S) has data packet to send destination
node(D)
S generates RREQ packet
S sends RREQ packet to each neighbor node
For each neighbor node, call as a intermediate
node (ID)
If ID packet buffer length more than
threshold(90%)
Free RREQ packet and return
Else
Connect S and D by line
Find midpoint M of this line
Find radius R = line size/2
Draw circle with radius R and M as
center
If ID not inside this circle
Free RREQ packet and
return
Else
If ID is destination
ID sends RREP to S
S sends data packets
by RREP path
Else
ID makes reverse
entry in routing table
Consider ID as S
Go to step 3
End If
End If
End If
End For
End If
End
Here RREQ packet is route request and
RREP means route reply packet. The RREQ
broadcasting circle area for O-ADOV is called as
prime circle area (PCA) by us. PCA is small area
compared to AODV’s RREQ broadcast area which is
whole movement area of all nodes. As above OAODV uses limited broadcast of RREQ packet and
load balancing, so data path finding process (Routing)
does not create adverse effect on data traffic.
Ultimately O-AODV provides lower average end to
end delay and higher packet delivery ratio for data
packets. Performance measurement results are shown
in next chapter. We have implemented above
algorithm in NS2 by modifying aodv.cc file and these
modifications are shown in appendix.
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VIII.
SIMULATION AND RESULT OF O-AODV
TABLE- 1.1 50 Node Scenario for Simulation
Parameter
No. of Nodes
Traffic Type
No. of Connection
Data Rate
Mobility Area
Pause time
Node mobility speed
Simulation Time
Value
50
CBR
25
5 packet/second
1000 * 1000 meter2
5 second
1,3,5,7,9 meter/second
240 second
Table 1.2 Result of O-AODV for 50 nodes
Node Speed
(meter/second)
Packet
Delivery Ratio
(%)
End to End
delay (msec)
1
64.76
847
3
63.64
1472
5
56.00
1292
7
51.88
926
9
53.64
1730
Table 1.3 Result of AODV for 50 nodes
Node Speed
(meter/second)
Packet Delivery
Ratio (%)
End to End
delay (msec)
1
59.88
1038
3
56.60
1854
5
48.52
1691
7
47.73
1356
9
45.39
1779
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International Journal of Engineering Trends and Technology (IJETT) – Volume 35 Number 1- May 2016
O-AODV
AODV
66
64
% (packet delivery ratio)
62
60
58
56
54
52
50
48
46
44
0
1
2
3
4
5
6
7
8
9
Node Speed(m/sec)
Figure 5.1 Node speed v/s Packet delivery ratio for
50 nodes
O-AODV
AODV
2000
End to End Delay(msec)
1800
1600
1400
1200
1000
800
0
1
2
3
4
5
6
7
8
9
Node Speed (m/sec.)
Figure 5.2 Node speed v/s End to End Delay for
50 nodes
that results of O-AODV is better compared to AODV.
We have also selected different cbr traffic rate 5, 10,
15 packets/second and found better result for OAODV. This performance is due to limited broadcast
of RREQ (route request packet) during path
construction phase of O-AODV. RREQ packet
broadcasting area for O-AODV is only prime circle
area (PCA). Whereas in case of AODV, RREQ
broadcast area is whole area of movement of all nodes.
Also we have used node buffer base load balancing
which reduce drop out of data packets. When node
input packet rate is higher than node output packet rate
is low, node stores extra packet in its packet buffer.
When this buffer is full , node starts dropping of
packet. Because of load balancing in O-AODV, node
buffer is rarely full and less chance of dropping of
data packets.
For testing performance we have used
TCL (tool command language) file. This file generates
tr (trace) file. Trace file contains multiple row. Each
row contains information about data packet source
node id, destination node id, packet sent time , packet
receive time etc. We have analyzed this trace file
using java parse trace file as well as using awk script
file. In both case we find same result for packet
delivery ratio and end to end delay.
We have tested O-AODV for different speed of
node, because in real life node is attached with human
being whom speed is not constant, but varying with
time. Node may be mobile phone, laptop or any
electronics system carrying by human. At different
speed we found high packet delivery ratio and low end
to end delay for O-AODV compared AODV.
IX. CONCLUSION
In O-AODV we are allowing RREQ packet’s
limited broadcast in prime circle area, so there is no
storm of broadcast packet. Also we keep heavily
loaded node away from being a part of new path for
load balancing. So packet delivery ratio is high for OAODV and End to End delay is less for O-AODV
compare to AODV. So we can say that O-AODV
performance is better. Because of load balancing
traffic is distributed among multiple nodes, node
energy will not exhaust for long time and network life
time will be increased.
REFERENCES
From graph fig. 5.1 and 5.2 indicates that OAODV performance is better in terms of performance
parameter packet delivery ratio and end to end delay.
Overall conclusion is that O-AODV is far better form
AODV due to proper route establishment technique
and load balancing. O-AODV have 10 % higher
packet delivery ratio and almost 15 % less end to end
delay.
We have tested O-AODV for different
number of nodes (16, 25, 50) and in all cases we found
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