Simulation plays an important role for designing, planning and operating a telecommunication network while assuring the quality of service since they allow one to:

• evaluate different design alternatives, ensuring the choice of the most appropriate option.
• identify and avoid potential system bottlenecks.
• evaluate the performance, capacity and scalability of networks and systems.
• elaborate dimensioning and planning rules in function of the foreseen traffic.

Telecommunications are in a constant and continuous process of transformation due to the proposal, introduction and evolution of new technologies. These technologies are more and more complex, and simulations are frequently the only means for evaluating and analyzing them before they are available to be tested.

In this talk, I will make a survey of the applications of the simulations made by a network operator such as Telefónica as a support of the network evolution. We will start with the application of simulations in legacy circuit switched networks, passing through ATM networks, and arriving to IP networks and future LTE technology. I will describe the simulations of these technologies covering topics such as traffic control (network management, admission controls, TCP protocol), routing strategies and mechanisms, P2P networks, radio access technologies, OSS and BSS systems, and service platforms.

We present our use of simulation in the analysis and design of hierarchical routing systems with support for quality of service (QoS). Hierarchical routing is used in most large networks for routing to scale in size. By using topology aggregation, a multi-level hierarchy of sibling and child clusters can be obtained.

Without revealing its internal structure, a cluster in a hierarchical system can advertise to other clusters its entry-to-exit transit QoS characteristics, such as delay and available bandwidth. These QoS characteristics can be expressed in terms of the parameters of some paths between each of the cluster’s border-node pairs.

When there are multiple QoS characteristics, it is generally not possible to pick a single path that simultaneously optimizes all of the parameters. Given a node pair, a minimum-weight path (in terms of either delay and/or hop count) has the smallest weight among all the paths but not necessarily the most available bandwidth. A widest path has the most available bandwidth, but usually has more delay or hops than a minimum-weight path. As a result, neither of these paths reflects accurately what is actually available inside a cluster to meet user QoS requirements, potentially resulting in sub-optimal routing.

Based on our operational experience and through simulation analysis, we discuss the pros and cons of using these paths by a cluster to advertise its transit QoS characteristics. Moreover, we show that advertising widest paths may interfere with normal operational procedures in the addition or deletion of links. As a practical solution, we propose the use of constrained minimum-weight paths for advertisement, to balance the need for smaller weights and sufficient available bandwidth.

Peer-To-Peer (P2P) traffic represents almost 60 % of Internet traffic, and involves personal computers working during periods of full-time operation (Always-ON). The rational use of shared resources opens up the possibility of reducing energy consumption associated with this type of operation. This paper analyses the results previously obtained from simulating an environment that shares resources among multimedia home networks, called Virtual Home Environment (VHE) and sponsored by the European Network of Excellence EuroFGI. The study analyzes the behavior of basic P2P distributed environments, comparing them to the new environment based on the virtualization of specific processes. This proposal includes a cost model that enables the restriction of behaviors associated with hoarding of resources. As a result, the energy consumption associated with this improvement implies a substantial reduction in the number of Always-ON devices, and the reduction and equalization of activity time around the area of the distributed network. The proposed simulation will be applied in future developments related with the activities proposed by Cost Action IC0804: Energy efficiency in large-scale distributed systems.

The IEEE 802.16 standard provides a full mobility support for stations moving across cell borders. In addition, the WiMAX Forum Network Working Group defines a set of procedures to support handovers in the mobile access network. One of the main characteristics of mobility support is fully controlled and optimized handover (HO), in which a mobile station (MS) migrates from the air interface of one base station (BS) to another one. It is vital to keep the BS transition phase as short as possible to decrease delays and data loss, which is especially crucial for real-time applications, such as VoIP. In this paper we analyze ASN-anchored mobility performance and provide advisable handover related parameters. The obtained results show that it is reasonable to adapt the handover initiation functionality to the environment where the network is deployed.

This paper presents the simulation tasks carried out by CITIC in the framework of the Spanish R&D project Gestión Activa de Demanda (Active Demand Management), with the acronym GAD. Before the actual development of the hardware and software in the GAD project, the entire system architecture was defined. During this initial phase two simulation tasks were performed in order to demonstrate the feasibility and efficiency of GAD communications both inside a potential customer’s home as well as in the upper levels of the electric distribution network. CITIC, working for Ericsson as a research organization, has carried out a specific task to simulate an in-home Broadband over Power Lines (BPL) network, applying the recently developed network simulator ns-3. New features have been added to this simulator in order to complete this task.

In this paper, we want to present a simulation platform for multimedia broadcast over DVB-SH. The platform has been designed and implemented within the context of the ESA study on ``Scalable Video Coding Applications and Technologies for mobile satellite based hybrid networks''. Its main features are realistic modelling of the multimedia encoding/decoding procedures done at the broadcasting head-end and the mobile terminals, a detailed simulation of the DVB-SH link layer, and a representative emulation of the DVB-SH physical layer. With the help of this platform, important use cases for future DVB-SH systems, such as support of heterogeneous devices, graceful degradation of application quality across the coverage area, efficient statistical multiplexing of different services, etc. can be investigated in a straightforward and conclusive manner.

Performance evaluations for enterprise applications running over IT systems are difficult to carry out given the multiplicity and variability of the operational components that constitute the dispersed IT infrastructures. To overcome this challenge, most of the approaches for performance assessment employ benchmarking strategies. While benchmarking methods provide exact indications on the performance capability of the measured facility, the results so obtained mostly apply to specific physical implementations considered in benchmark runs. The information provided by benchmark data thus restricts the ability to carry out meaningful performance analysis unless wide varieties of physical scenarios are generated for comparative studies. Given the logistical drawbacks associated with benchmarking techniques, we therefore propose a flexible model-based approach to determine quantitative performance for applications in IT systems by producing a range of performance models through the use of generic components that are easily assembled in simulation environments. Our approach initially considers a Tier 2 model framework whose components are derived from the SAP Sell-from-Stock application routine running on a multi-core processor server. The modelled framework is extensible enough to provide the definitions of resource consumption patterns of different applications as well as the variety of server hardware systems. The simulations of our initial models developed so far generate results that are comparable to measurements obtained for scenarios in the low and moderate loading levels.

Many complex technical systems today have some basic protocol capability, which is used for example to monitor the quality of production output or to keep track of oil pressure in a modern car. The recorded protocols are usually used to detect deviations from some predefined standards and issue warnings. However, the information in such a protocol is not sufficient to determine the source or cause of the problem, since only part of the system is being observed.

In this paper we present an approach to reconstruct missing information in only partially-observable stochastic systems based only on recorded system output. The approach uses Hidden non-Markovian Models to model the partially-observable system and Proxel-based simulation to analyze the recorded system output.

Experiments were conducted using a production line example. The result of the analysis is a set of possible system behaviors that could have caused the recorded protocol, including their probabilities. We will show that our approach is able to reconstruct the relevant information to determine the source of non-standard system behavior. The combination of Hidden non-Markovian Models and Proxel-based simulation holds the potential to reconstruct unobserved information from partial or even noisy output protocols of a system. It adds value to the information already recorded in many production systems today and opens new possibilities in the analysis of inherently only partially-observable systems.

Bridging the physical world with the virtual one often broadens the possibilities of accelerating and easing embedded system design. This is even more true for WSNs, where generally the developed applications need to be tested and executed in hundreds to thousands of nodes. Often times, it is hard to manage test beds that have huge number of nodes. The most common solution is to rely on simulation frameworks that allow the developers to create virtual sensor nodes and then provides levels of abstraction to specify the applications which will be executed on the nodes. The foremost drawback of this kind of simulation is the absence of direct interfaces with the physical environment. Hence in this paper we propose a hybrid simulation framework for WSN application development that interconnects a virtual network with the physical network and then allows one to simulate the networks as a whole. Moreover, the developers model WSN applications by using high level abstractions which could be used for multi-platform automatic code generation (in TinyOS and Ember ZigBee platforms).

In this paper we want to present a real-time emulation platform for a multi-radio network environment that supports intersystem handover based on the principles of 3GPP System Architecture Evolution (SAE). The testbed is based on Nomor’s Network Emulators for Application Testing (neatbox™) that have been extended with SAE core network components to support handover between different radio access networks. This work has been performed in the context of the EU funded project SEAmless Content Delivery (SEA). It allows the partners within this project to verify the improvement in the perceived quality-of-service (QoS) for mobile video streaming services achievable with their developed technologies. Especially handover situations between different radio technologies, as expected in future heterogeneous network architectures, will remain challenging for applications when it comes to avoid interruption or delay of the service. The efficiency of new technologies that cope with these challenges can be investigated and tested in a straightforward and conclusive manner.

In this tutorial, we investigate techniques to improve supply chain performance using system dynamics modeling and a genetic algorithm to develop robust and capable strategies to reduce overall cost and maximize deliveries. Using the Beer Game as the reference scenario, we show how performance can be greatly enhanced with minor changes to a few key points of the supply chain. This avoids the typical situation of sub-optimizing the entire chain because of the isolated decisions of only a couple of companies in the chain. Participants will try their hands at running a system dynamics-based supply chain model to see if they can improve the project performance over the poor baseline performance. We will begin with a basic model similar to the basic Beer Game model, and then grow in complexity to a supply chain with 15-20 entities. Attendants to the tutorial must bring a laptop running Windows XP (or later) with Windows .NET 3.5 installed.