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University: Universidad Politécnica de Madrid
Enrique Vázquez Gallo 
Department: Ingeniería de Sistemas Telemáticos


Title: Simulation of Quality of Experience of Web Access over HSDPA

This work in progress aims at evaluating the quality of service experimented by users of 3G mobile networks. In particular the study focuses on Web access over UMTS networks with HSDPA (High Speed Downlink Packet Access). The goal is to evaluate the equivalent capacity obtained by one HSDPA user in the presence of multiple users sharing the cell capacity, and the variation of page download times vs. number of users for various traffic profiles.

Title: Simulation of Wireless Mesh Networks

This work (result of a M.Sc. thesis) has focused on building Opnet models for simulation of Wireless Mesh Networks (WMN) in a campus scenario. WMN consist of a set of wireless nodes organized as client (end user) nodes, mesh nodes (wireless routers) and gateways to wired networks. In this work, client nodes have 802.11b/g access, mesh nodes behave as access points for client nodes and have also capabilities for communicating among them (the mesh network) using 802.11a links. Clients can also communicate with nodes in wired networks through the gateways between the WMN and Internet. The developed models have been used for performance evaluation in several scenarios depending on user traffic, number of clients, WMN size, and study of optimum radio channel allocations to the involved nodes.

Title: Simulation of SIP in the 3GPP IP Multimedia Subsystem (IMS)

The SIP-IMS model is an enhancement of the original SIP model provided in the standard model library of OPNET Modeler to allow simulations based on the IMS (IP Multimedia Subsystem). The model includes the IMS session establishment mechanism (comprising UAS and UAC processes, C-CSCF, P-CSCF and I-CSCF intermediaries, multidomain and roaming support), as well as process’ delay control in intermediaries and intermediaries’ redundancy. More information...

The SIP-IMS can be found in OPNET's Contributed Models depot.


Title: Simulation of Iub Interface in UMTS Terrestrial Access Networks

The emergence of new services that differs greatly in nature, due to the advent of the Third Generation mobile systems, will require changes in the transmission infrastructure with respect to the classical synchronous systems used in the current networks. The 3GPP, organization in charge of the UMTS deployment standardisation, proposes, in the current release of the standard, the use of AAL2/ATM as the transmission technology in the transport network of the UTRAN (UMTS Terrestrial Radio Access Network). The use of AAL2 allows the multiplexing of the traffic coming different users into the same ATM connection, providing an efficient utilization of the bandwidth. This adds even more complexity to a system like UMTS.

Due to difficulties involved in the analytical evaluation of the system performance, the use of simulation is an attractive alternative in the study. This work deals with the construction of an Iub interface simulator connecting Node B and RNC elements, by using OPNET Modeler. For that purpose, traffic models for voice (codec AMR) and data service (web) are proposed, and a module that simulates the behaviour of the Iub interface protocols is implemented. Later on, some configuration and results examples are introduced in order to show the capabilities offered by the simulation platform implemented.

See Table of Contents and References. Results obtained: Paper 1, Paper 2. The models used can be found in OPNET's Contributed Models depot.


Title: Evaluation of technologies for multimedia content distribution to mobile devices (ongoing work).

The aim of this work is to evaluate current tecnologies and protocols for the distribution of multimedia content to mobile devices in the framework of the LTE technology. In particular, a deep analysis will be carry out on the MBMS-3GPP tecnology that allows multicast and broadcast in cellular networks; the MIMO technology (Multiple-Input, Multiple-Output) that is employed to increase the transmission rate and reduce the error rate; and protocols like HLS (HTTP Live Streaming) and RTSP (Real Time Streaming Protocol). Several scenarios using different ways of sending multimedia streaming will be defined and simulated. Combinations of protocols and tecnologies will be modelled and the results of simulations will provide the basis to identify the weak points in every scenario.

Courses Using OPNET:

Title: Telematic Services and Network Engineering (LRST)

This course is focused on practical work related to the specification of networks and services that comply with given requirements, connection of user workstations and application installation, network interconnection, and performance analysis. The network environments studied in the laboratory include: IP networks, MPLS, LAN, and Frame Relay. Laboratory work will be performed using network simulators and/or real network environments. See course syllabus.

Title: Simulation of Communication Networks (CNSIM)

This course is an introduction to discrete-event simulation, with practical application to mobile networks. See course syllabus.

Title: Mobile Network simulation

We have used OPNET Modeler to simulate GSM networks with different topologies. The model of GSM is quite detailed, including in particular radio transmission aspects and signalling protocols. Students can simulate the movement of a mobile terminal across cells, measure uplink and downlink received power levels, measure the duration of TDM frames, study the parameters that control the cell selection procedure and the handover procedure, observe how mobiles access the random access channel, etc.

Concerning signalling protocols, they use the animation features of OPNET to trace signalling message sequences for protocols at the radio resource, mobility management, and call control levels, both in the base station subsystem and in the network switching subsystem. They study in detail the main GSM procedures: attachment to the network, location update, mobile originated and mobile terminated calls, and different cases of handovers, e.g. intra BSC, intra MSC, etc. See examples of class work.

The GSM models used can be found in OPNET's Contributed Models depot.

Title: Simulation of Communication Networks

OPNET Modeler is one of the simulation tools covered in the doctorate course "Simulation of Communication Networks". In this course, students learn the basic usage of OPNET Modeler by following some of the online tutorials included with the tool. See course syllabus.

Title: Switching I (CNM1)

This course is focused on principles of multiservice networks, considering key aspects such as efficiency and quality of services. It covers the architecture and functions of fixed and mobile telephone networks (GSM, GPRS, UMTS, LTE), the migration toward "All-IP" architectures, and the evolution to next generation networks (NGN). Some optional activities are being developed in the context of this course to use OPNET to simulate applications behaviour over mobile networks scenarios (UMTS, LTE) by students carrying out their master's thesis. See course syllabus.


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