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Performance Evaluation and Enhancement of Mobile Node: MIH

Info: 1794 words (7 pages) Essay
Published: 27th Sep 2017 in Computer Science

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4.1 Introduction

NS2 is associate open-source simulation tool that runs on Linux, it’s a discreet event machine targeted at networking analysis and provides substantial support for simulation of routing, multicast protocols and informatics protocols, like UDP, TCP, RTP and SRM over wired and wireless (local and satellite) networks. Its several blessings that build it a great tool, like support for multiple protocols and therefore the capability of diagrammatically particularization network traffic. In addition, NS2 supports many algorithms in routing and queuing. Local routing and broadcasts are a part of routing algorithms. Queuing algorithms embody honest queuing, deficit round-robin and FIFO.

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NS is associate object oriented machine, written in C++, with associate OTcl interpreter as a frontend. The machine supports a category hierarchy in C++ (also referred to as the compiled hierarchy during this document), and an identical category hierarchy inside the OTcl interpreter (also referred to as the taken hierarchy during this document). The 2 hierarchy’s square measure closely associated with every other; from the user’s perspective, there’s a matched correspondence between a category within the taken hierarchy and one within the compiled hierarchy, the basis of this hierarchy is that the category Tcl Object. Users produce new machine objects through the interpreter; these objects square measure instantiated inside the interpreter, and square measure closely reflected by a corresponding object within the compiled hierarchy. The taken category hierarchy is mechanically established through strategies outlined within the category TclClass. User instantiated objects square measure reflected through strategies outlined within the category TclObject.

NS2 is extensively utilized by the networking analysis community. It provides substantial support for simulation of communications protocol, routing, multicast protocols over wired and wireless (local and satellite) networks, etc. The machine is event-driven and runs in a very non-real-time fashion. It consists of C++ core strategies and uses Tcl and Object Tcl shell as interface permitting the computer file (simulation script) to explain the model to simulate.

Users will outline arbitrary network topologies composed of nodes, routers, links and shared media. A chic set of protocol objects will then be hooked up to nodes, sometimes as agents. The machine suite conjointly includes a graphical beholder referred to as network animator (NAM) to help the users get additional insights regarding their simulation by visualizing packet trace information.

NS is an occasion driven network machine developed at UC Berkeley that simulates style of informatics networks. It implements network protocols like communications protocol and UPD, traffic supply behavior like FTP, Telnet, Web, cosmic microwave background and VBR, router queue management mechanism like Drop Tail, RED and CBQ, routing algorithms like Dijkstra, and more. NS conjointly implements multicasting and a few of the mac layer protocols for computer network simulations.  

4.2 A Short History 

NS2 started as a variant of the $64000 network machine in 1989 (see Resources). REAL could be a network machine originally supposed for the real the dynamic behavior of flow and congestion management schemes in packet-switched information networks.

NS2 is associate degree object-oriented machine developed as a part of the VINT project at the University of American state in Berkeley. The project is funded by government agency together with XEROX Palo Alto research center (PARC) and Lawrence Berkeley National Laboratory (LBNL).

NS2 is accessible on many platforms like Linux, Ubuntu, FreeBSD, SunOS and Solaris. NS2 conjointly builds and runs underneath Windows.

Large scenarios benefit from large amounts of memory. Additionally, NS2 requires the following packages to run these scenarios Tcl has released Tcl8.3.2, Tk has released Tk 8.3.2, OTcl has released OTcl 1.0a7 and also TclCL has released TclCL 1.0b11.

4.3 C++ and OTCL Duality

In this means, the controls of the C++ objects area unit given to OTcl. It’s conjointly attainable to feature member functions and variables to a C++ connected OTcl object. The objects in C++ that don’t have to be controlled during a simulation or internally utilized by another object don’t have to be connected to OTcl. Likewise, associate degree object (not within the information path) is entirely enforced in OTcl.


Fig 4.1: C++ and OTcl: The Duality

In this means, the controls of the C++ objects area unit given to OTcl. It’s conjointly attainable to feature member functions and variables to a C++ connected OTcl object. The objects in C++ that don’t have to be controlled during a simulation or internally utilized by another object don’t have to be connected to OTcl. Likewise, associate degree object (not within the information path) is entirely enforced in OTcl.

Figure 5.1 shows associate degree object hierarchy example in C++ and OTcl. One factor to notice within the figure is that for C++ objects that have associate degree OTcl linkage forming a hierarchy, there’s an identical OTcl object hierarchy terribly just like that of C++.

NS was inbuilt C++ and provides a simulation interface through OTcl, associate degree object-oriented idiom of Tcl. The user describes a constellation by writing OTcl scripts, so the most ns program simulates that topology with mere parameters.

The NS2 makes use of flat earth model within which it assumes that the atmosphere is flat with none elevations or depressions. But the real world will have geographical options like valleys and mountains.NS2 fails to capture this model in it.

Many researchers have planned the additions of latest models to NS2.Shadowing Model in NS2 makes an attempt to capture the shadow impact of signals in real world, however will that inaccurately.NS2’s shadowing model doesn’t think about correlations: a true shadowing impact has sturdy correlations between 2 locations that area unit near one another. Shadow attenuation ought to be sculptured as a 2 dimensional log-normal random method with exponentially decaying spacial correlations.

4.4 Screenshot of Network Animator


Fig 4.2: Network Animator Window

NS animator window is shown in the above figure 4.2 which can be used to view the connection between the mobile and the network towers, it shows the movement packet drops which take place during simulation.

4.5 NIST’s Media Independent Handover module

4.5.1 Introduction

Wireless network types Handover are off two types, Horizontal handovers also called Homogenous Handover and Vertical handovers also called Heterogeneous handovers. If Handover take place in same access technology (WiFi <-> WiFi) or (WIMAX<->WIMAX) is Horizontal and if Handover takes place within the different access technology (WiFi <-> WiMAX) or (WIMAX<->WIFI) is Vertical Handover. If Longer the handover duration, then higher the packet drop and poor QoS [7]. IEEE with 802.21 MIH addressed vertical handover, which separates the different access technology in a mobile device from the upper layers in the protocol stack. NIST has provided the 802.21 MIH add-on modules [3] for network simulator (ns2.29). These module support the two of the MIH functions, events and commands.

4.5.2 Supporting Technologies of 802.21 in ns-2

Ns-2.29 supports the access technologies in IEEE 802.21 scenarios are: WiMAX (802.16), Wi-Fi (802.11), UMTS and Ethernet (802.3).

4.5.3 Implementation of Nodes with Multiple Interfaces in ns-2

NS-2 does not support the heterogeneous multiple interfaces of a mobile node (MN), because node structure do not necessarily follow the same as the one defined in the basic model by external packages. Hence to resolve this issue, NIST add-on module created the concept of multiFace node also called super node, which is a mobile node which can links to other mobile nodes, these interfaces for the multiFace node, and the multiFace node can be viewed as as “supernode”. This concept is illustrated in Fig. 4.1.


Fig. 4.1: High Level View of MultiFace Node


Fig. 4.2: Power boundaries defined in NS2

The interface nodes activate the events and forwards them to the super node. The MIH Users on the super node are often ready to register and to receive these events.

4.5.4 Power Boundaries are often outlined in Wifi and WiMAX Cells

In order to spot power boundaries which may be utilized in the simulation, 3 variables are outlined in ns-2.29, that is shown in Fig. 5.2. Theses variable are often outlined as:

CSTresh: accustomed outline the minimum power level to sense wireless packets and conjointly switch the mac layer, if mac layer is idle then it are often switched to busy,

RX Tresh: are often accustomed outline the minimum power level to receive wireless packets with error free;

pr_limit: are often perpetually equal or superior to one and is employed within the equation (RX Tresh) * (pr_limit), then this equation are going to be shaping the minimum power level that Associate in Nursing interface senses Link taking place event before triggering.

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In the above figure Fig 4.2, shows the ability boundaries between WLAN and WiMAX base station with its vary wherever the highest most layer is Cs thresh_, middle layer is rx thresh_ and also the inner layer is rx thresh_ * pr limit_.

Dept. of CSE, VKIT 2014-20151


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