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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Implementation and analysis of enhancement in opportunistic network using NS2</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Sandeepak Bhandari</string-name>
          <email>sandeepak525@gmail.com</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>A. Nodes</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Aleksandras Stulginskis University</institution>
          ,
          <addr-line>Kaunas</addr-line>
          ,
          <country country="LT">Lithuania</country>
        </aff>
      </contrib-group>
      <fpage>65</fpage>
      <lpage>73</lpage>
      <abstract>
        <p>-Opportunistic network is a new class of wireless network. This network is based on store-carry-forward mechanism. An architecture and functionality are different from another wireless network such as wireless sensor network or mobile ad hoc network. Unlike mobile ad hoc network opportunistic network do not need end to end path between source and destination nodes for providing communication between them. In this paper, methodology for enhancement in opportunistic network is proposed and implement by using network simulation. Multi-hop relay technique and Virtual-ID used together to enhance the performance of opportunistic network and at last performance of opportunistic network is analyzed by using three different cases in opportunistic network.</p>
      </abstract>
      <kwd-group>
        <kwd>Opportunistic network</kwd>
        <kwd>Bundle layer</kwd>
        <kwd>Storecarry-forward manner and relay technique</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>I. INTRODUCTION</p>
      <p>
        A new network is invented or a class of delay tolerance
network in which some device which is carried by the users
in their daily life and can pass message when they get
opportunity, hence network is called opportunistic network
[
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. It is framed by the hubs having ability to bolster this
system, the hubs are associated wirelessly. The hubs are
versatile or stable so no settled foundation is available in
this system and this system can work even in disconnected
environment [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. Each hub has a limited range in which they
can convey or can forward the message. A hub can forward
a message just when some other hub comes in his range.
The hubs need to store the message until another hub is not
come in his range [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. All hubs need to work in the
storeconvey forward way in this system.
      </p>
      <p>
        In this network, group of intermediate nodes help to send
a message from source to destination. Hubs have no
predefined topology of the system, two hubs may be or
never associated, no fix route between two nodes is use to
send message [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ]. Network topology may change due to
activation and deactivation of the node. If destination node
is not in the range of source node, then it passes the message
to the nearest node in its range and so on node by node
closer to the destination. This system is anything but
difficult to execute in any circumstance or any environment
      </p>
    </sec>
    <sec id="sec-2">
      <title>Copyright © 2017 held by the authors 65 like war and catastrophe inclined territories where correspondence is for brief time furthermore, needs rapidly.</title>
      <p>
        In such environment, we have less time to actualize the
system topology or to make a foundation [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. At such an
area or time this system is extremely helpful to encourage
the client to convey.
      </p>
    </sec>
    <sec id="sec-3">
      <title>II. BASIC TERMS USED IN OPPORTUNISTIC NETWORK</title>
      <p>
        Nodes are the basic component of a network which has
the property of receiving and forwarding the message.
Nodes are may be fixed or moving depends upon the
network. Like a computer with blue tooth, radar, a laptop, a
mobile phone etc. when a source node want to send a
message to a destination it checks its entire closest node and
pass the message to the node which is in its range and
closest to the destination [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ]. After that next closest node
receiving the message and then repeat the above procedure
until message not delivered to the correct location.
      </p>
      <sec id="sec-3-1">
        <title>B. Information Sprinkler</title>
        <p>
          An information sprinkler is a dedicated and a stable node
which is fixed in a dedicated location in a cluster of
opportunistic network or a stable node is present in every
cluster of the opportunistic network [
          <xref ref-type="bibr" rid="ref3">3</xref>
          ] Information
sprinkler works same as other nodes in opportunistic
network it can also forward the message like other
intermediate nodes. It uses data sharing protocol
        </p>
      </sec>
      <sec id="sec-3-2">
        <title>C. Find Opportunity</title>
        <p>In this system hubs, can just forward the message when
they inspire chance to send it. Opportunity is characterized
as the halfway hubs comes in the scope of the hub needs to
send the message at exactly that point they can forward the
message. A hub needs a neighbor hub which is nearest to it
and lies in his range. Presently the message is conveying by
the neighbor hub and a similar idea is currently use by the
neighbor hub to forward the message thus on till the
message is not compasses to the goal hub. At times, the
source hub itself likewise motivated chance to forward the
message to the goal, if goal or source hubs change their area
and inside the scope of each other.</p>
      </sec>
      <sec id="sec-3-3">
        <title>D. Message Exchange</title>
        <p>
          When two nodes discovered each other successfully then
only they can share the message or data [
          <xref ref-type="bibr" rid="ref10">11</xref>
          ]. A node can
exchange data to its closest node within the direct range.
Then nodes pass the data to its closest node and then the
next neighbor node store the message and wait for the
opportunity to forward the message to next node.
        </p>
      </sec>
      <sec id="sec-3-4">
        <title>E. Relay Technique/Toplogy</title>
        <p>
          When the source and destination are interconnected by
means of some nodes. In such a network the source and
destination cannot communicate to each other directly
because the distance between the source and destination is
greater than the transmission range of both of them [
          <xref ref-type="bibr" rid="ref12">12</xref>
          ],
hence the need of intermediate node(s) to relay.
        </p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>III. PROPOSED METHODOLOGY</title>
      <p>
        In opportunistic network, no fixed infrastructure is
available and no end to end path is setup between source and
destination node to provide communication between them.
So, there is no mechanism to find the selfish node [
        <xref ref-type="bibr" rid="ref9">10</xref>
        ] which
is not interested to forward the message from source node or
may edit the original message from source to destination
node [
        <xref ref-type="bibr" rid="ref11 ref7">7,8</xref>
        ]. In opportunistic network message is passes
through multiple intermediate node between source and
destination node. So, three distinct mechanisms are used to
provide a secure communication between source and
destination node regardless number of intermediate nodes to
be used to delivered a message from source to destination
node and vice-versa, three different mechanisms are
authentication, using of virtual-ID and relay technique.
      </p>
      <sec id="sec-4-1">
        <title>A. Authentication</title>
        <p>
          Every node in the opportunistic key has a unique –ID and
password which is stored at the stable node in table form. To
start the communication, each node needs to get Virtual –ID
from the stable node of its cluster. In this simulation set up
[
          <xref ref-type="bibr" rid="ref13">13</xref>
          ], there are two clusters and each cluster has one stable
node. To get the Virtual-ID from the stable node, node needs
to provide its unique-ID and password.
        </p>
      </sec>
      <sec id="sec-4-2">
        <title>B. Using of Virtual-ID</title>
        <p>
          After authentication, and the node is the valid then stable
node issue a Virtual-ID of source node and destination node
along with secure session key and send it to the source and
destination node. The secure session key is used to encrypt
the message at the source end and decrypt at the destination
node [
          <xref ref-type="bibr" rid="ref8">9</xref>
          ]. The Virtual –ID and secure session key is valid for
a single session of communication between source and
destination node [
          <xref ref-type="bibr" rid="ref14">14</xref>
          ]. Whenever a new communication is
beginning between two nodes, a new virtual-ID and a secure
session key is need to communicate
        </p>
      </sec>
      <sec id="sec-4-3">
        <title>C. Relay technique</title>
        <p>At last relay technique is used to provide communication
between source and destination node if both nodes are not
within the range of each other. The default range of mobile
node to receive and forward the message is 250 meters (in
NS 2) but this value can be used by setting value of the
receiving threshold (RXThresh_).</p>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>IV. SIMULATION SETUP</title>
      <p>
        Network Simulator 2 [
        <xref ref-type="bibr" rid="ref16 ref17">16,17</xref>
        ] is used to configure the
opportunistic network with 13 nodes, the network is divided
into two clusters using position based clustering technique
[
        <xref ref-type="bibr" rid="ref15">15</xref>
        ], having three mobile nodes and two stable nodes and all
configuration regarding opportunistic network that is
implemented in this research paper are shown on below table
1. The range of mobile nodes to receive and forward the
message is 250 meters and stable nodes are directly
connected with each other.
      </p>
      <p>In simulation setup, three different simulations are
implemented with different numbers of mobile nodes are
used to provide the communication between source and
destination node and analyze the performance of
opportunistic network in different parameters such as
throughput, packet loss, delay and privacy. In this section,
main idea of enhancement of opportunistic network is shown
through figures of simulation.</p>
      <p>Parameters</p>
      <p>Terrain Area
Simulation Time</p>
      <p>MAC Type
Application Traffic
Routing Protocol</p>
      <p>Data Payload
Number of Nodes
Number of Sources</p>
      <p>Value
800m x 800m
6 seconds
802.11
CBR
AODV
13
1
1000Bytes/Packet</p>
      <p>Set up network with finite number of nodes.</p>
      <p>Network is divided into clusters using cluster estimation techniques.</p>
      <p>Get virtual-ID for communication between source and destination node from stable</p>
      <p>node.</p>
      <p>Provide unique-ID and password to stable node.</p>
      <p>authentication</p>
      <p>Yes
Stable node (from cluster 1) send encrypted message (virtual-ID of source</p>
      <p>And destination node and secure session key) to source node.</p>
      <p>Stable node (from cluster 2) send encrypted message (virtual-ID of source</p>
      <p>And destination node and secure session key) to destination node.</p>
      <p>No
Yes</p>
      <p>Within
Range?</p>
      <p>No
Direct communication began between source and destination node.</p>
      <p>Communication between source and destination</p>
      <p>Using relay technique.</p>
      <p>End</p>
      <p>Above figure demonstrates the simulation setup with 13 hubs along with 2 stable hubs. The opportunistic network is divided
into two clusters using position based clustering technique. One cluster with blue color having 5 nodes and node 2 is stable node
of this cluster and another cluster having 8 nodes and node 8 is stable node. Node 4 and node 10 are the source and destination
node in the opportunistic network.</p>
      <p>In Figure 3, stable node issue virtual ID to the source node and destination node i.e. node 4 and node 10 respectively along
with secure session key which is used at source and destination end for encryption and decryption respectively. Before getting
virtual ID from the stable node, source node must provide its unique ID and password for authentication.</p>
      <p>In Figure 4, source node start communication with destination node by sending message to the intermediate node by using
virtual ID and this message is encrypted with secure session key so intermediate do not understand the message and it simply
forward the message to the next node in which its range and this process repeat until the message received by the destination
node.</p>
      <p>.</p>
      <p>In Figure 5, the message is received by destination node 10. The message passes through the node 1 and node 7 to provide
communication between source node and destination node. In this research paper three different simulations are set up and
implemented. In each simulation, different numbers of mobile nodes are used to analyze the performance the performance of
opportunistic network in different parameters.</p>
    </sec>
    <sec id="sec-6">
      <title>V. SIMULATION RESULTS In this section, the output of the implementation of enhanced opportunistic network using proposed methodology is shown in the form of graphs. The X axis of graph represent the time of simulation in seconds whereas Y axis of graph represent the number of packets.</title>
      <p>
        In above graph (Fig. 6) shows the throughput of enhanced opportunistic network i.e. maximum number of packets successfully
received at the destination end in per second [
        <xref ref-type="bibr" rid="ref18 ref19">18, 19</xref>
        ]. In this research paper the performance of opportunistic network is analyzed
through three different cases by taking different number of mobile nodes. In above graph, there are three different outputs for each
simulation red, green and blue lines shows the output of first (one mobile node), second (two mobile nodes) and third simulat ion
(three mobile nodes) respectively. In each output the throughput of network is continuously increasing.
      </p>
      <p>TIME</p>
      <p>
        In above graph (Fig.7) shows the packet loss of enhanced opportunistic network i.e. number of packets are received at the
destination end with respect to number of packets are send from the source end [
        <xref ref-type="bibr" rid="ref19">19</xref>
        ]. From above graph the packer loss of
opportunistic network is decreasing i.e. in first, second and third cases there is 6, 30 and 20 number of packets are loss
respectively. In below graph (Fig. 8) shows the delays of enhanced opportunistic network i.e. numbers of packets are delay at the
destination end [
        <xref ref-type="bibr" rid="ref20">20</xref>
        ]. As there is no fixed infrastructure in opportunistic network i.e. opportunistic network is collection of mobile
and stable nodes. So, message is delivered only when there is opportunity in network i.e. when two nodes are within the range of
each other, so delay may be high in some cases.
      </p>
      <p>
        In this research paper, three different techniques namely authentication, virtual-id and relay techniques are used together to
improve the performance of opportunistic network. In below table, table II shows the simulation results which depicts that the
proposed methodology improving the performance of opportunistic network by increasing throughput and decreasing the packet
loss and delay. The proposed methodology is better than traditional methodology [
        <xref ref-type="bibr" rid="ref8">9</xref>
        ] in which only relay technique is used to
provide communication source and destination node by comparing the results of both methodology, for instance the delay in
traditional methodology for single mobile node is 5 packets per second [
        <xref ref-type="bibr" rid="ref8">9</xref>
        ] and in proposed methodology the delay for single
mobile node is 2 packets per second which shows that proposed methodology is better than traditional methodology. In proposed
methodology three different simulations are set up with different number of mobile nodes namely case I, case II and Case III to
analyze the performance of opportunistic network while in traditional methodology no such cases are implemented and analyzed.
      </p>
      <p>Parameters
Throughput
Packet loss</p>
      <p>Delay</p>
      <p>Case I
6
6
2</p>
      <p>TIME
In this research paper, the performance of opportunistic
network is enhanced by using proposed methodology, in
which three different mechanisms are used such as
authentication, virtual ID and relay technique. First network
is divided into two clusters using position based clustering.</p>
      <p>When a node wants to communicate, first it must get virtual
ID from its stable node by providing its unique ID and
password to the stable node for the valid authentication of
node. After authentication, node will get virtual ID from
stable node and start its communication with other node by
using virtual ID instead of its actual ID, which enhance the
privacy of node and provide a secure communication. When
source and destination nodes are within the range of each
other then they can directly communicate with each other
otherwise they communicate by using relay technique. From
Simulation results, it shows that proposed methodology is
useful in improving the performance of opportunistic
network in terms of delay, packet loss and throughput
parameters. Along with the performance of opportunistic
network, it also enhanced the privacy of user or node.</p>
    </sec>
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