The aim of this work is to study methods of handover used in WiMAX and WLAN networks, next suggest the posibility of simulation methods for WLAN handover in the simulation environment OPNET Modeler. This work is focused primarily on obtaining the information about neighboring AP and subsequent selection of a new AP using such information. The work describes in detail each processes solutions that are used to implement newscanning methods

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / This paper discusses channel simulation using OPNET Modeler in support of iNET. It shows how wireless communication is simulated, how to simulate the special aeronautical channel of iNET, and how to deliver the aeronautical channel, test article, and ground station as reusable components for future simulation. Network simulation is a critical tool for iNET and it enables design decisions that cannot be made analytically due to the complexity of the problem. This work addresses the incorporation of the aeronautical channel into the OPNET Modeler tool set as this piece of iNET is unique and is not available in OPNET Modeler.

No description available.

The main aim of this work was to study the issue of the SNMP protocol and MIB database in order to focus on management and configuration of MIB database using the SNMP protocol. The Master's thesis in detail describes especially creating a communications model of the Manager - Agent type in an OPNET Modeler. In this modeling tool we created exchange of information from the side of the Manager to the side of the Agent via SNMP packets. The Master's thesis is mainly focused on the creation of the SNMP packet according to defined rules, then on reading of information from the MIB database on the side of the Agent and saves this information to the Manager’s MIB database. Exchange of informations is realized via the messages of type GetRequest, GetNext and GetResponse. These models are programmed in language C/C++ and then implemented into the environment of OPNET Modeler.

This thesis describes simulation models for Local Multipoint Distribution Service (LMDS) systems, and uses simulation to examine the performance of two different multiple access schemes and two different duplexing schemes. LMDS is a broadband wireless point-to-multipoint access network that aims to improve network access capacity for end-users by solving the "last mile" problem. This study involves building a parameterized simulation model for symmetric LMDS systems and comparing performance of the systems for different multiple access and duplexing schemes. The report describes the LMDS system and briefly discusses other broadband access networks. Objectives of this study are discussed and methodology is chosen. The simulation model design is explained. Further, the experimental design is discussed. The simulation results are presented and discussed, and conclusions are drawn. The multiple access schemes under study are Time Division Multiple Access (TDMA), and Frequency Division Multiple Access (FDMA). The duplexing schemes under study are Time Division Duplexing (TDD), and Frequency Division Duplexing (FDD). For the system under study, it was observed that TDMA results in lower end-to-end (ETE) delay per packet, but higher jitter, than FDMA. In addition, TDD results in lower ETE delay per packet than FDD. Specifically, TDMA in conjunction with TDD was found to result in lowest ETE delay per packet among the configurations under study. In addition, FDMA in conjunction with FDD was found to result in lowest jitter among the configurations under study. / Master of Science

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / This paper discusses simulating iNET's protocol stack using OPNET Modeler. It shows an example of a custom protocol simulated in OPNET Modeler, and how to model the test article, and ground station as reusable components for future simulation. Network simulation is a critical tool for iNET as it enables design decisions that cannot be made analytically due to the complexity of the problem. This work addresses the incorporation of iNET's protocol stack into the OPNET Modeler tool set as this piece of iNET is unique and is not available in OPNET Modeler.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / Distributed Denial of Service (DDoS) attacks have been gaining popularity in recent years. Most research developed to defend against DDoS attacks have focused on analytical studies. However, because of the inherent nature of a DDoS attack and the scale of a network involved in the attack, analytical simulations are not always the best way to study DDoS attacks. Moreover, because DDoS attacks are considered illicit, performing real attacks to study their defense mechanisms is not an alternative. For this reason, using packet/network simulators, such as OPNET Modeler, is the best option for research purposes. Detection of an ongoing DDoS attack, as well as simulation of a defense mechanism against the attack, is beyond the scope of this paper. However, this paper includes design recommendations to simulate an effective defense strategy to mitigate DDoS attacks. Finally, this paper introduces network links failure during simulation in an attempt to demonstrate how the network recovers during and following an attack.

Η παρούσα διπλωματική εργασία πραγματεύεται την προσομοίωση του πρωτοκόλλου Mobile Internet Protocol version 4 (MIPv4), το οποίο έχει προταθεί για τη διαχείριση της κινητικότητας των χρηστών, έχοντας ως στόχο τη διατήρηση των ενεργών συνδέσεών τους. Το βασικό πλεονέκτημα του πρωτοκόλλου MIPv4 αναφέρεται στη διατήρηση των διεπαφών του πρωτοκόλλου με ανώτερα υποστρώματα, όπως το Transmission Control Protocol – TCP, τα οποία ενεργούν με βάση μία σταθερή ΙΡ διεύθυνση, ενώ παράλληλα παρέχουν αδιάλειπτες υπηρεσίες, ανεξάρτητα από τη θέση του τελικού χρήστη. Ωστόσο, το πρωτόκολλο MIPv4 παρουσιάζει κάποια σημαντικά μειονεκτήματα, όπως η τριγωνική δρομολόγηση και η ενθυλάκωση πακέτου, σε περιπτώσεις υποστήριξης υπηρεσιών πραγματικού χρόνου, όπως το Voice over IP – VoIP. Αυτές οι διεργασίες έχουν ως αποτέλεσμα την εμφάνιση αυξημένης συνολικής καθυστέρησης, διεύρυνσης της διακύμανσης της καθυστέρησης (jitter) και εμφάνισης επιπλέοντος επίβαρου στο δίκτυο, κυρίως λόγω των ενθυλακωμένων πακέτων. Στην παρούσα διπλωματική εργασία, η προσομοίωση του πρωτοκόλλου MIPv4 στοχεύει στην μελέτη της επίδρασης αυτών των παραμέτρων, ώστε να γίνουν κατανοητοί οι μηχανισμοί υποστήριξης της κινητικότητας των χρηστών, οι οποίοι χρησιμοποιούν εφαρμογές πραγματικού χρόνου. Η υλοποίηση της προσομοίωσης του πρωτοκόλλου πραγματοποιήθηκε με τη χρήση του λογισμικού προσομοίωσης ΟΡΝΕΤ, το οποίο παρέχει στο χρήστη τη δυνατότητα της ολοκληρωμένης μελέτης πρωτοκόλλων δικτύου, και την πολύπλευρη διερεύνηση των αποτελεσμάτων της προσομοίωσης. / In this diploma thesis, the simulation of the Mobile Internet Protocol version 4 (MIPv4) is presented and analyzed. The MIPv4 has been developed in order to deal with the user mobility problem, by targeting on the continuity of the active connections. The main advantage of the MIPv4 is the provision of uninterrupted applications, while taking into account that upper layer protocols, such as the Transmission Control Protocol (TCP) consider a single (and constant) IP address throughout the connection duration. However, the MIPv4 has a number of disadvantages, such as the triangular routing and the packet encapsulation that limits the performance of the protocol in cases where mobile users activate real-time applications. The degradation of the protocol’s performance is realized through the increase of the end-to-end delay, the enhanced delay jitter and the higher network overload, mainly due to the packet encapsulation. This diploma thesis targets on the study of the effect of these parameters through simulation, in order to provide an insight of the mechanisms that support the user mobility when real-time applications are activated. The simulation environment is developed by using the OPNET simulation tool, which provides a comprehensive implementation of all network layers and offers a versatile investigation of simulation results.

Voice over Internet Protocol (VoIP) provides a new telephony approach where the voice traffic passes over Internet Protocol shared traffic networks. VoIP is a significant application of the converged network principle. The research aim is to model VoIP over a hybrid Universal Mobile Telecommunications System (UMTS) network and to identify an improved approach to applying the ITU-T Recommendation G.107 (E-Model) to understand possible Quality of Service (QoS) outcomes for the hybrid UMTS network. This research included Modeling the hybrid UMTS network and carrying out simulations of different traffic types transmitted over the network. The traffic characteristics were analysed and compared with results from the literature. VoIP traffic was modelled over the hybrid UMTS network and the VoIP traffic was generated to represent different loads on the network from light to medium and heavy VoIP traffic. The VoIP over hybrid UMTS network traffic results were characterized and used in conjunction with the E-Model to identify VoIP QoS outcomes. The E-Model technique was implemented and results achieved were compared with results for other network types highlighted in the literature. The research identified an approach that permits accurate Modeling of VoIP QoS over a hybrid UMTS network. Accurate results should allow network design to facilitate new approaches to achieving an optimal network implementation for VoIP.

The aim of this work is to give information about the structure and elements of the IP Multimedia Subsystem, using signaling protocol and transferring messages between the terminal and elements of IMS. Create model, which implements messages transfer between terminal and IMS elements, by environment tools OPNET Modeler. This work describes system function IMS, its architecture, basic elements, architecture of using signaling protocol SIP and its elements, SIP and SDP messages format and the way of ensuring Quality of Services. There is a project of model terminal registration and reservation data flow by terminal in the IMS. These models were realized in a simulation environment called OPNET Modeler by using tools: project editor, node editor and process editor. In the last part of this work, the method of verification correct function of realized models was created by simulation tools called Debbuger. This tool is one of the environment tools OPNET Modeler.