Performance of dsdv protocol based on different propagation model with vari

International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-
6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 4, July-August (2013), © IAEME
333
PERFORMANCE OF DSDV PROTOCOL BASED ON DIFFERENT
PROPAGATION MODEL WITH VARIOUS TOPOLOGIES
Sanjukta Tanti1
, Sukant Kishoro Bisoy2
, Namita Das3
, Mohit Ranjan Panda4
1,2,3,4
C.V.Raman College of Engineering, Bhubaneswar, India
ABSTRACT
One of the most important factors in evaluating the performance of routing protocols in
MANET is the variation in received signal strength known as fading. Different types of routing
protocols have been proposed based on the propagation models that neglect the effect of fading. The
choice of propagation models have a great impact on performance, so realistic models are necessary
to consider the effect of fading as far as an accurate analysis of performance of the routing protocols
is concerned. In this paper, comparative analysis of proactive protocol is performed using NS2, in
order to study the impact of propagation model with various topologies. The non-fading models such
as free space and two ray ground are simulated for comparison. The simulation results show that the
propagation models have a great role in routing protocol of MANET.
Keywords: MANET, Routing protocol, DSDV, Propagation Model, NS2
1. INTRODUCTION
A mobile Ad Hoc Network is (MANET) is a network consisting of a group of wireless
mobile nodes that communicate with each others without centralized control or established
infrastructure. In this kind of networks, communication between two nodes that are neighbors
requires relying of messages by some intermediate nodes with act as a router as well as
communication end-point. Moreover, the role of routing protocols among nodes becomes a
challenging task because the nodes move independently. A route that is believed to be optimal at a
given time might not work at all a few moments later.There are many routing protocols available in
MANET. Among them ad hoc on demand distance vector (AODV) [1] and dynamic source routing
(DSR) [2] are reactive routing protocols and Destination Sequenced Distance Vector (DSDV) [3] is
proactive routing protocols. Propagation models focused on predicting the average received signal
strength at a given distance from the transmitter, as well as the variability of the signal strength in
close spatial proximity to a particular location. The accuracy of any particular propagation model in
any given condition will depend on the suitability among the constraints required by the model and
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ISSN 0976 – 6367(Print)
ISSN 0976 – 6375(Online)
Volume 4, Issue 4, July-August (2013), pp. 333-340
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334
depend on terrain. A number of propagation models like Free Space and Two Ray ground have been
exist. In this paper the performance of some of the well known ad hoc protocols is studied under
different propagation models.
The rest of the paper is organized as follows: A brief review is presented on current ad hoc
routing protocols in section 2. Section 3 presents two propagation models. Section 4 focused on
simulation environment during the evaluation process. Section5 describes the results and analysis
finally in section 6 the conclusions are presented.
2. AD HOC ROUTING PROTOCOLS
For mobile ad hoc networks, the issue of routing packets between any pair of nodes becomes
a challenging task because the nodes can move randomly within the network. A path that was
considered optimal at a given point in time might not work at all a few moments later. Moreover, the
random properties of the wireless channels add to the uncertainty of path quality [4]. Traditional
routing protocols are proactive in that they maintain routes to all nodes, including nodes to which no
packets are being sent. They react to any change in the topology even if no traffic is affected by the
change, and they require periodic control messages to maintain routes to every node in the network.
Generally routing protocols for ad-hoc networks can be classified in two different classes: pro-active
protocols, re-active protocols based on how they discover the route.
2.1 Ad-hoc On Demand Distance Vector (AODV)
The Ad-hoc on demand Distance Vector Routing protocol enables multi hop routing between
the participating mobile nodes wishing to establish and maintain an ad-hoc network. AODV is a
reactive protocol based upon the distance vector algorithm. The algorithm uses different messages to
discover and maintain links. Whenever a node wants to try and find a route to another node. It
broadcasts a Route Request (RREQ) to all its neighbors. The RREQ propagates through the
network until it reaches the destination or the node with a fresh enough route the destination. Then
the rout is made available by uncasing a RREQ back to the source. Once the RREQ reaches the
destination or an intermediate node with a fresh enough route, the destination or intermediate node
responds by unicasting a route reply (RREP) packet back to the neighbor from which it has received
the first RREQ.The algorithm uses hello message (a special RREQ) that are broadcast periodically
to the immediate neighbors. These hello messages are local advertisements for the continued
Presence of node and neighbors using routes through the broadcasting node will continue to mark the
route as valid .If hello messages stop coming from a particular node, the neighbor can assume that
the node has moved away and mark that link to the node as broken and notify the affected set of
nodes by sending a link failure notification (a special RERR) to that set of nodes.
2.2 Destination Sequenced Distance Vector (DSDV)
This protocol is based on the classical Bell man-ford routing algorithm to apply to mobile ad-
hoc network. In that each node holds a routing table including next- hop information for each
possible destination. Each entry has a sequence number. If a new entry is obtained the protocol
prefers to select sequence number is the same the protocol selects the metrics with the lowest value.
Routing information is transmitted by broadcast, updates have to be transmitted periodically or
immediately when any significant topology change is available. Each routing at each of the stations,
lists all available destinations and the number of hops to each route table entry is tagged with
sequence number which is organized by the destination station. To maintained the consistency of
routing tables in a dynamically topology, each station periodically transmits updates and transmits
updates immediately when significant new information is available.

335
3. RADIO PROPAGATION MODELS
Propagation models are used to predict the propagation characteristics such as received signal
power of each packet. Propagation model is a set of mathematical expressions, diagrams, and
algorithms used to represent the radio characteristics of a given environment [5]. Those models are
very important in the planning process since they can typically predict the path loss along a link or
the effective coverage area of a transmitter. Propagation radio models are three types: path loss,
shadowing and fading. The first type can be expressed as the power loss during the signal
propagation in the free space. The second type is characterized by fixed obstacles on the path of the
radio signal propagation. The third category is the fading which is composed of multiple propagation
distances, the fast movements of transmitters and receivers units and finally the reflectors. Path loss
can be expressed as the ratio of the power of the transmitted signal to the power of the same signal
received by the receiver, on a given path. It is a function of the propagation distance. Estimation of
path loss is very important for designing and deploying wireless communication networks. Path loss
is dependent on a number of factors such as the radio frequency used and the nature of the terrain [6].
We consider Free Space model and Two Ray Ground model for our work.
3.1 Free Space Model
In the free space model, it is assumed that there is only one clear line-of-sight path between
the sender and the receiver. The following equation is used to calculate the received signal power
free space at distance d from the sender. The free space model basically represents the
communication range as a circle around the transmitter. If a receiver is within the circle, it receives
all packets. Otherwise, it loses all packets. H. T. Friis presented the following equation to calculate
the received signal power in free space at distance d from the transmitter [7] [8].
………… (1)
Here Pt = Transmitted signal power, = Antenna gain of the sender
= Antenna gain of the receiver, L (L 1) = System loss, Lambda = Wave length
3.2 Two Ray Ground Model
The two-ray ground reflection model focuses on the direct path and a ground reflection path,
instead of focusing only in the path. It is demonstrate that this model offers better performance in
long distance among nodes than the free-space model. The received power at distance d is predicted
by
Here
= Height of the sender antenna, = Height of the received antenna
= Antenna gain of the sender, = Antenna gain of the receiver
D = distance, L (L >=0) = system loss and Here ht, hr and L =1 is assumed.
The above equation shows a faster power loss than Eqn. (1) as distance increases.
However, the two-ray model does not give a good result for a short distance due to the oscillation
caused by the constructive and destructive combination of the two rays. Instead, the free space model
is still used when d is small. It is shown that this model gives more accurate prediction at a long
distance than the free space model [7] [8].

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4. SIMULATION ENVIRONMENT
In order to evaluate the impact of propagation models in the performance of Ad hoc routing
Protocols, the simulations have been conducted using NS-2.34 [9]. We considered Free Space and
Two Ray Ground as propagation model and DSDV as ad hoc routing protocol for our work. We
evaluate the performance in two different scenarios. In first scenario we arranged all the nodes as
chain toplogy as shown in figure 1. In second scenario nodes are arranged as cross topology as
shown in figure 2. For both scenarios, nodes are separated by 50, 75, 100, 125, 150, 175 meter. By
varying the distance between them we measured the throughput, packet loss, routing overhead and
average end to end delay of DSDV protocol over two propagation models said before. For chain
topology we have two simultaneous flows one is from node 0 to node 1 and another is from node 2 to
node 3. Similarly cross topology have two simulataneous flows: node 0 to node 4 and another is from
node 6 to node 8.The parameters used for our simulations are hsown in table 1. Author in [10],
evaluated the performance of AODV, DSR and OLSR routing protocols in MANETs under CBR
traffic with different network conditions.
Figure 1: Chain topology with 5 nodes Figure 2: Cross topology with 9 nodes
Table 1: Parameter used for simulation
PARAMETER VALUE
Propagation model Two Ray Ground and Free Space
Routing protocol DSDV
Data packet CBR
MAC protocols 802_11
Number of connections 2
Transmission Range 250 m
Data packet size 512 bytes
Channel Type Wireless
Time of simulation 100 Sec
Area of simulation 1000*1000

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5. RESULT AND ANALYSIS
In this section, we analyze the results gathered from the simulated scenarios. The parameters
used for the evaluation are throughput, packet loss, packet loss, routing overhead and average end to
end delay.
5.1 Chain Topology
First we study the effect of propagation model namely free space and two ray groud on
DSDV routing protocol in chain scenario. Intially throughput and packet loss is measured by
uniformly separating the distance between nodes by 50, 75, 100, 125, 150 and 175 meter. From
figure 3 we found throughput of free space model is better than two ray ground model because the
free space propagation model assumes the ideal propagation condition that there is only one clear
line -of-sight path between the transmitter and receiver. But in reality the signal reaches the receiver
through multiple paths because of reflection, refraction and scattering [11]. But throughput of DSDV
gracefully decreases with increase of distance. However there is fewer packet loss in two ray ground
model as compared to free space model (see figure 4).
Figure 3: Throughput Vs Distance in chain topology
Figure 4: Packet loss Vs Distance in chain topology

338
Then we measured the routing overhead and average end to end delay of DSDV over two
propagation model. Figure 5 shows that routing overhead of DSDV protocol is more in two ray
ground model as compared to free space model. It is about 5 % more in two ray ground model. But
all models have maximum 20% overhead for all distance considered for chain topology. On the
otherhand average end to end delay of free space model is higher than two ray ground.
Figure 5: Routing Overhead Vs Distance in chain topology
Figure 6: Average end-to-end Delay Vs Distance in chain topology
5.2 Cross Topology
Next we study the effect of two propagation model over DSDV routing protocol arranging
the nodes as cross toplogy as shown in figure 2. The distance between nodes is same for all nodes as
similar to chain topology. Intially we measured throughput and packet loss of DSDV protocol. As
shown in figure throughput of free space model is higher than two ray ground model for all distance.
There is a slight increase in packet loss with increase of node to node distance as shown in figure 8.
For both topologies the packet loss ranges from 4500 to 4650. But routing overhead of free space is
more than two ray ground over cross topology (see figure 9). Routing overhead in cross topology and
chain tolology are about 25% and 20%, respectively. From figure 10, the average end to end delay of
free space model is higher than two ray ground model over DSDV protocol with cross topology. The
maximum delay in chain topology and cross topology is 0.32 sec and 0.27 sec, respectively.

339
Figure 7: Throughput Vs Distance in cross topology
Figure 8: Packet Loss Vs Distance in cross topology
Figure 9: Routing Overhead Vs Distance in cross topology
Figure 10: Average end-to-end Delay Vs Distance in cross topology

340
6. CONCLUSIONS
This paper focuses on the importance of appropriate propagation model for ad hoc routing
protocol. We explore the performance of DSDV routing protocol with Free Space and Two Ray
Ground propagation model over various topology namely chain and cross topology. We use
throughput, pacekt loss, routing overhead and average end to end delay as performance metrics for
our work. Our result shows that performance of free space model is better than two ray ground model
with respect to throughput and routing overhead over chain and cross topologies. On the other hand
free space model has more packet loss and average end to end delay as compare to two ray ground
model. But most of the situation free space model performs better than two ray ground model.
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