Tadeusz Czachórski

Tadeusz Czachórski
Polish Academy of Sciences | PAN · Institute of Theoretical and Applied Informatics

Prof. Dr.

About

146
Publications
15,555
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775
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January 1990 - present
Silesian University of Technology
Position
  • Professor (Full)

Publications

Publications (146)
Chapter
Unmanned Aerial Vehicles (UAVs) are rapidly gaining popularity in a wide variety of applications, e.g., agriculture, health care, environmental management, supply chains, law enforcement, surveillance, and photography. Dones are often powered by batteries, making energy a critical resource that must be optimised during the mission of the drone. The...
Conference Paper
Full-text available
The traffic from the large number of IoT devices connected to the IoT is a source of congestion known as the Massive Access Problem (MAP), that results in packet losses, delays and missed deadlines for real-time data. This paper reviews the literature on MAP and summarizes recent results on two approaches that have been designed to mitigate MAP. On...
Chapter
The traffic from the large number of IoT devices connected to the IoT is a source of congestion known as the Massive Access Problem (MAP), that results in packet losses, delays and missed deadlines for real-time data. This paper reviews the literature on MAP and summarizes recent results on two approaches that have been designed to mitigate MAP. On...
Article
Full-text available
The paper addresses two issues: (i) modeling dynamic flows transmitted in vast TCP/IP networks and (ii) modeling the impact of energy-saving algorithms. The approach is based on the fluid-flow approximation, which applies first-order differential equations to analyze the evolution of queues and flows. We demonstrate that the effective implementatio...
Book
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The book covers the international advances in Modelling, Analysis and Simulation of Computer Systems and Networks and of their Applications
Conference Paper
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A significant challenge of IoT networks is to offer Quality of Service (QoS) and meet deadline requirements when packets from a massive number of IoT devices are forwarded to an IoT gateway. Many IoT devices tend to report their data to their wired or wireless network gateways at closely correlated instants of time, leading to congestion known as t...
Preprint
Full-text available
A significant challenge of IoT networks is to offer Quality of Service (QoS) and meet deadline requirements when packets from a massive number of IoT devices are forwarded to an IoT gateway. Many IoT devices tend to report their data to their wired or wireless network gateways at closely correlated instants of time, leading to congestion known as t...
Article
Full-text available
The increasing use of Software-Defined Networks brings the need for their performance analysis and detailed analytical and numerical models of them. The primary element of such research is a model of a SDN switch. This model should take into account non-Poisson traffic and general distributions of service times. Because of frequent changes in SDN f...
Article
Full-text available
The transmission of massive amounts of small packets generated by access networks through high-speed Internet core networks to other access networks or cloud computing data centres has introduced several challenges such as poor throughput, underutilisation of network resources, and higher energy consumption. Therefore, it is essential to develop st...
Article
Full-text available
In this article, a way to employ the diffusion approximation to model interplay between TCP and UDP flows is presented. In order to control traffic congestion, an environment of IP routers applying AQM (Active Queue Management) algorithms has been introduced. Furthermore, the impact of the fractional controller PIγ and its parameters on the transpo...
Article
Full-text available
It has been observed that Software Defined Networks (SDN) can change the paths of 16 different connections in the network at a relatively frequent pace to improve overall network 17 performance, including delay and packet loss, to establish new paths and remove unused connections, 18 or to respond to other needs such as security. These changes mean...
Chapter
Software-Defined Networks (SDN) dynamically modify the paths of Internet flows in response to the quality of service or security needs, and hence frequently modify traffic levels at network routers. Thus network routers often operate in the transient regime, rather than at steady-state, with significant impact on packet loss probabilities and delay...
Chapter
Today’s telecommunication network infrastructure and services are dramatically changing due partially to the rapid increase in the amount of traffic generation and its transportation. This rapid change is also caused by the increased demand for a high quality of services and the recent interest in green networking strengthened by cutting down carbo...
Article
Full-text available
The article introduces an approach combining diffusion approximation and simulation ones. Furthermore, it describes how it can be used to evaluate active queue management (AQM) mechanisms. Based on the obtained queue distributions, the simulation part of the model decides on package losses and modifies the flow intensity sent by the transmitter. Th...
Book
Full-text available
This book constitutes the post proceedings of the 28th International Symposium on Modelling, Analysis, and Simulation of Computer and Telecommunication Systems, MASCOTS 2020, held online -due to COVID -19- in Nice, France, in November 2020. The 17 full papers presented were carefully reviewed and selected from 124 submissions. The symposium collect...
Book
This book constitutes the refereed post-conference proceedings of the First IFIP TC 5 International Conference on Computer Science Protecting Human Society Against Epidemics, ANTICOVID 2021, held virtually in June 2021. The 7 full and 4 short papers presented were carefully reviewed and selected from 20 submissions. The papers are concerned with a...
Conference Paper
Full-text available
We present a model of a Software Defined Network (SDN) where frequent changes in routing and traffic rates at routers are needed to respond to the security, quality of service (QoS), and energy savings requirements of applications such as the Internet of Things. Such frequent path and traffic changes introduce time-dependent network behaviours, and...
Article
Full-text available
Markov queueing models are a powerful tool to evaluate the performance of computer networks and have been used in telecommunication studies for over 100 years. To apply them to the evaluation of the modern Internet, we should not only adapt them to the contemporary network structures but also include a description of the complex stochastic patterns...
Conference Paper
Full-text available
The broader use of Software Defined Network (SDN) controllers creates periodic changes in topology and traffic rates at routers that adapt the network to changes in network conditions. Thus the transient behaviour of network components, and in particular routers, is becoming of great interest. Since standard queueing models are difficult to analyze...
Preprint
Full-text available
Software Defined Networks (SDN) dynamically modify the paths of Internet flows in response to quality of service or security needs, and hence frequently modify traffic levels at network routers. We therefore investigate the time-dependent performance of a small network of nodes that represent SDN forwarders, modelled as G/G/1/N queueing stations. T...
Chapter
The congestion control is one of the most important questions in modern computer network performance. This article investigates the problem of adaptive neuron based choice of the Active Queue Mechanisms parameters. We evaluate the performance of the AQM mechanism in the presence of self-similar traffic based on the automatic selection of their para...
Book
This book includes a selection papers describing the latest advances and discoveries in the field of human-computer interactions, which were presented at the 6th International Conference on Man-Machine Interactions, ICMMI 2019, held in Cracow, Poland, in October 2019. Human-computer interaction is a multidisciplinary field concerned with the desig...
Chapter
Full-text available
The paper proposes steady state and transient state diffusion approximation models for the design and performance evaluation of multichannel communication networks. We concentrate on \(G/G/c/c+K\) queueing model and highlight some its applications together with numerical examples to illustrate how this models can be used.
Preprint
The article describes the diffusion approximation and the method of its use for evaluation of the effectiveness of active queue management (AQM) mechanisms. The presented model combines the approximation and simulation approaches. The diffusion is used to estimate queue distributions. The goal of the simulation part of the model is the evaluation o...
Article
Full-text available
The aim of the article is to contribute to the modeling and evaluation of TCP/IP traffic control in case of active queue management mechanisms implemented in congestion router. We consider mechanisms based on RED and fractional-order \(PI^\alpha\) controller. A new model based on diffusion approximation is developed and its results are compared wit...
Chapter
HTTP based communication protocols are ubiquitous in modern distributed control/supervision systems, therefore it becomes important to understand the performance of the HTTP protocol working with this type of applications and to develop techniques to investigate the impact of the protocol on the overall performance of these systems. A distributed c...
Chapter
Full-text available
In this paper the performance of AQM mechanism based on three controllers and the impact of traffic self-similarity on network utilization are investigated with the use of discrete event simulation modelling. The queue is divided into several thresholds. Each segment of the queue is controlled by a different mechanism. We analyze in tests the lengt...
Book
Full-text available
The ISCIS series of conferences were launched in Ankara, Turkey, in 1986 at Bilkent University, and the 31st such event took place in Krakow, Poland, in 2016. Recent ISCIS symposia have centered broadly on computer science and engineering. Their proceedings have been published by Springer and attracted hundreds of thou- sands of paper downloads ove...
Chapter
In this paper we present the probability function based on PID controller with non-integer integral and derivative orders. We present how to change the probability of packet dropping during continuous increase in buffer occupancy. The shape of the probability function strictly depends on the parameters selection.
Conference Paper
The article presents a queueing model of a computer network which is installed at a branch of the largest Polish insurance company. The network is used to store and use documents related to company clients. Our model concentrates on the database server and applications used to retrieve and modify the documents. The model is based on measurements ga...
Chapter
Full-text available
The chapter presents an overview of the eight that are part of the European IoT Security and Privacy Projects initiative (IoT-ESP) addressing advanced concepts for end-to-end security in highly distributed, heteroge- neous and dynamic IoT environments. The approaches presented are holistic and include identification and authentication, data prote...
Chapter
We present a model of the edge router between electronic and all optical networks. Arriving electronic packets of variable sizes are stored at a buffer the volume of which is equal to the fixed size of optical packet. When the buffer is filled, its content becomes an optical buffer and dispatched to optical network. To avoid excessive delays, the o...
Chapter
Full-text available
This paper briefly reviews some recent research in Cybersecurity in Europe funded by the European Commission in areas such as mobile telephony, networked health systems, the Internet of Things. We then outline the objectives of the SerIoT Project which started in 2018 to address the security needs of fields such as Smart Cities, Smart Transportatio...
Chapter
Full-text available
The article discusses the problem of choosing the best parameters of the non-integer order \(PI^{\alpha }\) controller used in IP routers Active Queue Management for TCP/IP traffic flow control. The impact of the self-similarity of the traffic on the controller parameters is investigated with the use of discrete event simulation. We analyze the inf...
Preprint
Full-text available
SerIoT is a Research and Innovation Project funded by the European Commission to demonstrate secure networks for the Internet of Things (IoT). This paper presents an overview of the design for smart and secure network infrastructures for the IoT, based on Software Defined Networks (SDN), named the SerCPN system, whose main component is a smart SDN-...
Conference Paper
Transient state queueing models help us to understand better the dynamics of internet transmissions and the performance of traffic control algorithms. Fluid flow approximation, due its simplicity, as it is based on first-order differential equations, is popular and frequently used – but even it, if applied to large topologies, is time and space con...
Conference Paper
Hidden Markov Models (HMM) have been widely used in several areas of computer science. Conventional HMMs are well-known for their efficiency in modeling short-term dependencies between adjacent elements, but some researchers concluded that they cannot grasp long-range interactions between distant elements. Long-range dependence (LRD) of data refers...
Conference Paper
In this paper the performance of fractional order PID controller as AQM mechanism and impact of traffic self-similarity on network utilization are investigated with the use of discrete event simulation models. The researches show the influence of selection of PID parameters and degree of traffic self-similarity on queue behavior. During the tests w...
Conference Paper
Full-text available
Delays in routers are an important component of end-to-end delay and therefore have a significant impact on quality of service. While the other component, the propagation time, is easy to predict as the distance divided by the speed of light inside the link, the queueing delays of packets inside routers depend on the current, usually dynamically ch...
Conference Paper
Full-text available
TCP congestion control algorithms have been design to improve Internet transmission performance and stability. In recent years the classic Tahoe/Reno/NewReno TCP congestion control, based on losses as congestion indicators, has been improved and many congestion control algorithms have been proposed. In this paper the performance of standard TCP New...
Chapter
Mixed reality systems overlay real data with virtual information in order to assist users in their current task. They generally combine several hardware components operating at different time scales, and software that has to cope with these timing constraints. MIRELA, for MIxed REality LAnguage, is a framework aimed at modelling, analysing and impl...
Conference Paper
This paper examines the impact of the degree of self-similarity on the selected AQM mechanisms. During the tests we analyzed the length of the queue, the number of rejected packets and waiting times in queues. We use fractional Gaussian noise as a self-similar traffic source. The quantitative analysis is based on simulation.
Conference Paper
Full-text available
We investigate the use of Markov chains in modeling the queues inside IP routers. The model takes into account the measured size of packets, i.e. collected histogram is represented by a linear combination of exponentially distributed phases. We discuss also the impact of the distribution of IP packets size on the loss probability resulting from the...
Article
Full-text available
In this paper the performance of a fractional order PI controller is compared with that of RED, a well-known active queue management (AQM) mechanism. The article uses fluid flow approximation and discrete-event simulation to investigate the influence of the AQM policy on the packet loss probability, the queue length and its variability. The impact...
Chapter
The article presents an approach to numerical modeling of dynamics of flows in wide area TCP/IP computer networks with the use of SAP HANA in-memory database. The aim is to explore the possibility of transforming a broadly known modeling method—fluid-flow approximation—into database language, overcoming this way the need to develop dedicated soluti...
Book
This book provides an overview of the current state of research on development and application of methods, algorithms, tools and systems associated with the studies on man-machine interaction. Modern machines and computer systems are designed not only to process information, but also to work in dynamic environment, supporting or even replacing huma...
Conference Paper
The paper discusses various models of self-similar Internet traffic and techniques for estimating the intensity of Long-Range Dependence (LRD). In the experimental part real data sets collected in IITiS PAN are used together with synthetic LRD flows generated using Fractional Gaussian noise and Markov modulated Poisson processes. We are especially...
Book
Full-text available
This book provides an overview of the current state of research on development and application of methods, algorithms, tools and systems associated with the studies on man-machine interaction. Modern machines and computer systems are designed not only to process information, but also to work in dynamic environment, supporting or even replacing huma...
Conference Paper
This paper examines various techniques for estimating the intensity of Long-Range Dependence (LRD). Trial data sets with LRD are generated using Fractional Gaussian noise and Markov modulated Poisson process. The real data set collected in IITiS PAN is also used.
Conference Paper
The paper defines a method to extract a part of a graph, which corresponding to a network (Internet) topology covering a certain area. The method refers to data gathered within Opte Project and describing the Internet topology. The extracted parts of graphs have been analyzed in terms of the number of neighbours, longest path length and existence o...
Conference Paper
In convergent access networks, access nodes (composed by optical and wireless components) can serve Base Stations (BSs). In the access node, the wireless receivers are one of the components with high energy consumption level. We can save energy by implementing transmission techniques to receive data in some periods of times, and switching off the w...
Article
Queueing theory is a useful tool in design of computer networks and their performance evaluation. The literature concerning this subject is abundant. However, it is in general limited to the analysis of steady states. It means that flows of customers considered in models are constant and obtained solutions do not depend on time. It is in glaring co...
Book
Full-text available
Man-Machine Interaction is an interdisciplinary field of research that covers many aspects of science focused on a human and machine in conjunction. Basic goal of the study is to improve and invent new ways of communication between users and computers, and many different subjects are involved to reach the long-term research objective of an intuitiv...
Book
Full-text available
The 29th Annual Symposium on Computer and Information Sciences, held in Krakow under the auspices of the Institute of Theoretical and Applied Informatics of the Polish Academy of Sciences, pursues the tradition of a broad-based sym- posium presenting recent advances in scientific and technical aspects of Information Technology. Notable in this year...
Conference Paper
The aim of this paper is to use the superposition of two-state Markov Modulated Poisson Processes to replicate the statistical nature of internet traffic over several time scales. This paper characterizes of network traffic using Bellcore data and LAN traces collected in IITiS PAN. The fitting procedure for matching second-order self-similar proper...
Conference Paper
The paper presents a comparison of two approaches to queuing models used in performance evaluation of computer networks: Diffusion approximation and fluid-flow approximation. Both methods are well known and are used alternatively in similar problems but the differences between their results and the errors they introduce when applied to TCP driven t...
Article
Full-text available
This article presents the use of fluid flow approximation to model interactions between a set of TCP, UDP and XCP flows in the environment of IP routers using AQM (Active Queue Management) algorithms to control traffic congestion. In contrast to other works, independent UDP and TCP streams are considered and the model allows to start and end data t...
Article
The article summarises author's experience in two problems related to the use of queueing models in performance evaluation of computer networks: modelling transient states of queues and computations for queueing network models having large number of nodes. Both issues are not well represented in classical queueing theory, yet important to applicati...
Chapter
The paper presents measurements and analysis of a LAN long-range dependence traffic collected in IITiS PAN (The Institute of Theoretical and Applied Informatics of the Polish Academy of Sciences). Several methods of Hurst parameter estimation were used, the results obtained by the methods differ substantially. The analysis was made for the whole tr...
Chapter
Classical Erlang and Engset formulae determining the availability of channels, loss probability, and characteristics of overflow traffic are still used in telecommunications. Moreover, they are also interesting for traffic management in mobile networks and in Internet. They are based on the assumption of Poisson flows and exponentially distributed...