International Journal of Scientific & Engineering Research, Volume 4, Issue 10, October-2013 666

ISSN 2229-5518

A Comparative Analysis of Experimental

and Simulation Based network to enhance the performance and reliably of Wireless network

Rajiv Mahajan

Ph.D Scholar Singania University Rajasthan

ABSTRACT --- In wireless networking performance is one of the most important factor but it is very difficult to estimate the performance of the system because it require a lot of time cost and equipment specially in case of the large network, So in order to estimate the more accurate figure or data before implementation simulation results play a vital role. In this paper we compare the result of the experimental and simulation setup for packet size, throughput, packet loss and round trip delay with different communication protocol and it is find that result variation between experimental and simulators lies between 10-20%. Further we find that UDP perform well as compared to TCP which is a guidelines to setup a wireless network to improve the performance of the Academic network with slight modification of the existing parameters

Index Terms --- Opnet, AODV, UDP, TCP, Round Trip Delay, Throughput, Packet Loss Rate,

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1. INTRODUCTION

For significant information results, it is important that the model on which the simulator is based matches as much as possible the physical experimental design. For most researchers it is extremely expensive and impractical to build a large complex network. There are not enough resources and time available. One of the most important advantages of network simulators is scalability, which allows the simulation of a large number of networking devices without going to the expense of purchasing the real equipment. Simulation provides an economic and effective way for developing and validating new theories. Simulation results will not always be in favor of the original theory.
It is very important to validate the results in order
to collect the more accurate information and it is
difficult to setup the large network to perform the experiment physically so it is better to use some simulator to perform the same scale experiment

*Rajiv Mahajan is currently Pursuing Ph.D in CSE from

Singania University Rajasthan (India)

Before the implementation at the physical level. OPNET is the best tools to perform the experiment based upon the simulation. So in this section Opnet is used to perform the experiment and then it is compared with the physical results then it is used to scale the experiment to large extend to find the result for large networks.

2. METHODOLOGY

This experiment is conducted in order to
investigate the effect of changing packet size on the
performance of Ad-hoc networks. The aim of this
experiment is to choose the optimal packet size
that is going to be used throughout the thesis.
Transmitting large packets over wireless networks helps to reduce header overhead, but may have an adverse effect on packet loss rate due to corruptions in the radio link. Packet loss rate in the lower layers, however, is typically hidden from the upper protocol layers by link or MAC layer protocols. For this reason, errors in the physical layer are observed by the application as higher variance in end-to-end delay rather than increased packet loss rate 56.Five wireless PC’s named as node 1 to five with Manual IP address Located in the Academic Organization are used to collect Different scenario are used to find the throughput of network and AODV are used for routing. In first scenario only two nodes involved in the

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communication, node2 is sending TCP traffic to node4 in the second scenario node2 and node3 are communicating simultaneously with node4 sending TCP traffic In third node 4 is receiving TCP traffic generated and sent at the same time from node2, node3, and node5 In fourth node2 is sending TCP traffic to node5 (node2 is not within the range of node5 so node2 uses other nodes as relay nodes) in fifth only two nodes involved in the communication, node2 is sending UDP traffic to node4 in sixth node2 and node3 are communicating simultaneously with node4 sending UDP traffic in seventh node 4 is receiving UDP traffic generated and sent at the same time from node2, node3, and node5 node2 is sending UDP traffic to node5 (node2 is not within the range of node5 so node2 uses other nodes as relay nodes). In order to find the accuracy of the results experiment is tested for 30 times to collect the average. All five nodes were set up at the different location of the organization in different buildings. In the same ways results are validated using OPNET.

3. RESULTS ANALYSIS

3.1 PACKET SIZE

In this experiment only two nodes are involved in the communication. Node2 generates TCP traffic and sends it to node4. The same experiment is repeated while node2 sends UDP traffic. This is done to check the effect of changing the transport layer protocol on the performance of Ad-hoc networks. The packet size ranges from just 100 bytes up to 2000 bytes. Each test is repeated 30 times due to variations in obtained results. The results of this experiment are summarized in Figure 3

Figure 3 (a)

The graphs in this figure show that the throughput first attains a maximum at around 1300 to 1500 after that it get decreased so in order to find the more accurate size of the packet. The packet size is further investigate with small interval that in the
range of 1300 to 1500 bytes which corresponds to MTU of 1500 bytes, IP header of 20 bytes, and UDP header of 8 bytes. Similarly in case of physical experiments, it was notice that there is a sharp decrease in throughput once packet size reaches
1460 bytes.

Table 3.1: Average throughput variation with respect to change in packet size.

Table clearly shows that around about at packet size 1470 we find the maximum figure of throughput and after that it slowly goes down that mean it the optimize value where both TCP and UDP traffic having the maximum value so it can be used for the investigation in future.

4. PERFORMANCE MEASUREMENT

4.1 PACKET LOSS RATE

Packet loss rate is another parameter used in this thesis to evaluate the performance of wireless networks. The packet loss rate at nodeX for transmission between nodeX and nodeY describes the percentage of packets transmitted from nodeX over the network that did not reach nodeY. Packet losses specify the ability of the system to reliably transfer a packet from the source to its destination. Dropped packets have a serious impact on the performance of many applications and in particular streaming media. The number of lost and/or dropped packets seems to be a lot higher within wireless environments compared to the wired equivalent.
Table shows clearly that the more nodes
communicating with a single node the higher the packet loss. node2, node3, and node5. This can be explained by noting that a bottleneck situation at

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International Journal of Scientific & Engineering Research, Volume 4, Issue 10, October-2013 668

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the receiving node is formed. When the number of simultaneous nodes trying to communicate with the same destination node increases, the transmission delay at the wireless interface increases. Consequently, packets may experience increasing queuing delays, forming a bottleneck situation at the wireless interface.

Table 4.1 (a) : packet loss rate with TCP traffic

Table 4.1 (b) : Packet Loss Rate with UDP traffic

4.2 THROUGHPUT

In this section, only the throughput of the sending node is collected so it can be compared with the physical experimental results. We find almost the same result as that of the physical experiment the table shown below the summery of average throughput during the simulation.
The throughput usually decreases with the hop count for three reasons:
• Stations in communication range need to share the common channel.
• Stations in interference range may transmit at the
same time resulting in a collision and requiring a
retransmission.
• The transmission delay increases with the hop
count.
It is also clear from these values that the
throughput decreases with the number of nodes
trying to communicate simultaneously with node4.
This can be justified by noting that the cause may
again be related to the formation of a bottleneck
situation at node4.
It is also noticeable from this table that, as
expected, the throughput values, when nodes are
communicating using UDP traffic, are higher
compared to when nodes send TCP traffic. This
can be explained by noting that UDP does not require acknowledgments that compete for transmission time over the shared channel.

4.3 ROUND TRIP DELAY

As discussed before, the round trip delay indicates how long it takes to send a packet of data from its source to destination and back. It is usually described in seconds or milliseconds. Simulation base results are as shown below in table

Table 4.3 (a): Average Round trip Delay in ms with TCP Traffic

Table 4.2(a): Average throughput with TCP traffic

Table 4.2 (b): Average throughput with UDP traffic

Table 4.3 (b): Average Round trip Delay in ms with UDP Traffic

It is clear from the values in this table that the round trip delay increases as a function of the nodes that communicate concurrently with the same node. This can be described by noting that when more nodes communicate with node4, there

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is a relatively larger queue forming at node4’s interface. Therefore, an average packet experiences a higher amount of queuing delay until it is actually transmitted by the interface.
As expected, it is also apparent from the values in
Table 4-3 that the round trip delay, when nodes
send UDP traffic, is lower compared to when they
send TCP traffic. This is due to the flow and
congestion control of TCP that scarifies the transmission time to achieve more reliable data transport.

5. COMPARISON OF EXPERIMENTAL AND

SIMULATION RESULTS

Validation is an essential process to check the accuracy of the simulation outcome. This can be achieved by comparing the results collected from the physical experiments with those collected from the simulation.

5.1 THROUGHPUT COMPARISON

TCP Based Traffic Throughput Comparison
UDP Based Traffic Throughput Comparison

5.3 ROUND TRIP DELAY COMPARISON

TCP Based Traffic Throughput Comparison

UDP Based Traffic Throughput Comparison

UDP Based Traffic Throughput Comparison

5.2 PACKET LOSS RATE COMPARISON

TCP Based Traffic Throughput Comparison

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