00383nas a2200133   4500000000100000000000100001008004100002260000800043100001300051700002400064700001600088700002200104245012300126       2007                            d  bACM1 aA. Busic1 aTadeusz Czachórski1 aJ. Fourneau1 aKrzysztof Grochla00aLevel Crossing Ordering of Markov Chains: Proving Convergence and Bounding End to End Delays in an All Optical Network01111nas a2200157   4500000000100000000000100001008004100002260003600043100001900079700002400098700002200122700002400144245007000168300001400238520070100252       2010                            d  bIITiS PANaGliwice, Bałtycka 51 aAdam Józefiok1 aTadeusz Czachórski1 aKrzysztof Grochla1 aTadeusz Czachórski00aPerformance evaluation of multiuser interactive networking system  a223–2313 aThe article presents a work in progress aiming at performance evaluation of a large database system at an assurance company. The system includes a server with a database and a local area network with a number of terminals where the company employees run applications that introduce documents or retrieve them from the database. We discuss a model of clients activities. Measurements were collected inside the working system: the phases at each users application were identified and their duration was measured. The collected data are used to construct a synthetic model of applications activities which is then applied to predict the system bahaviour in case of the growth of the number of users.00343nas a2200121   4500000000100000000000100001008004100002260004600043100001600089700002400105700002200129245007000151       2007                            d  c6bWydawnictwo Komunikacji i Łączności1 aA. Brachman1 aTadeusz Czachórski1 aKrzysztof Grochla00aAnaliza wydajności protokołu TCP-NCR w sieciach bezprzewodowych00359nas a2200121   4500000000100000000000100001008004100002260002600043100002400069700002100093700002200114245010100136       2006                            d  bPolitecnico de Torino1 aTadeusz Czachórski1 aJoanna Domańska1 aKrzysztof Grochla00aDynamics of TCP/IP flows in presence of various AQM algorithms, a fluid flow approximation model00338nas a2200121   4500000000100000000000100001008004100002260004200043100002400085700002100109700002200130245006400152       2006                            d  cVIbTechnical University of Catalonia1 aTadeusz Czachórski1 aJoanna Domańska1 aKrzysztof Grochla00aTCP/IP dynamics in wireless environment, a fluid-flow model00327nas a2200121   4500000000100000000000100001008004100002100002400043700002200067700001900089700001600108245008100124       2011                            d1 aTadeusz Czachórski1 aKrzysztof Grochla1 aAdam Józefiok1 aTomasz Nycz00aSimulation, Markov Chain and Diffusion Approximation Models – a Case Study00954nas a2200181   4500000000100000000000100001000000100002008004100003100002400044700002200068700001900090700001600109245009500125300001100220490000700231520052000238022001400758       2011                            d1 aTadeusz Czachórski1 aKrzysztof Grochla1 aAdam Józefiok1 aTomasz Nycz00aPorównanie metod analizy efektywności na przykładzie serwera aplikacji w sieci lokalnej  a7–200 v323 aW artykule przedstawiono model kolejkowy służący do oceny funkcjonowania dużego systemu sieciowego, w skład którego wchodzi rozbudowany system bazodanowy. Opisywany system jest systemem rzeczywistym. Zebrane wyniki pracy systemu posłużyły do budowy modelu działania aplikacji interakcyjnych, na podstawie łańcuchów Markova, aproksymacji dyfuzyjnej i symulacji zdarzeń dyskretnych. Porównanie ich z rzeczywistymi wynikami umożliwiło sprawdzenie przdatności użytych metod w rzeczywistych warunkach.  a1731-226401415nas a2200205   4500000000100000000000100001008004100002260001300043100002400056700002200080700001900102700001600121700002000137700001700157700001700174700002200191245010700213300001400320520087500334       2012                            d  bSpringer1 aTadeusz Czachórski1 aKrzysztof Grochla1 aAdam Józefiok1 aTomasz Nycz1 aFerhan Pekergin1 aErol Gelenbe1 aRicardo Lent1 aGeorgia Sakellari00aPerformance Evaluation of a Multiuser Interactive Networking System: A Comparison of Modelling Methods  a215–2223 aThis article presents a queueing model for performance evaluation of a large database system at an assurance company. The system includes a server with a database and a local area network with a number of terminals where the company employees run applications that introduce documents or retrieve them from the database. We discuss a model of clients activities. Measurements were collected inside the working system: the phases at each users application performance were identified and their duration was measured. The collected data are used to construct a synthetic model of applications activities which is then applied to predict the system behaviour in case of the growth of the number of users. We apply simulation, Markov and diffusion models-their comparison, based on real data, may better verify the utility of particular methods than usual academic examples.01580nas a2200169   4500000000100000000000100001008004100002260002100043100002400064700002200088700002000110700002000130700002100150245005200171300001400223520117300237       2007                            d  c5bSpringeVerlag1 aTadeusz Czachórski1 aKrzysztof Grochla1 aFerhan Pekergin1 aJ. Garcia-Vidal1 al. Cerda-Alabern00aStability and Dynamics of TCP-NCR(DCR) Protocol  a241–2543 aThe fluid-flow approximation models investigate with much success the dynamics and stability of TCP/RED connections. Their main assumption is that the fluctuations of variables characterizing the behaviour of the connections are relatively small, that enables the linearization of model and the use of traditional control analysis tools to obtain such measures as Bode gain, phase margins, tracking error or delay margin. In this article, preserving linear fluid-flow model, we propose its extension to the case when a network is composed of wired and wireless part. We consider a variant of TCP algorithm (TCP-DCR or its new version TCP-NCR) and fluid-flow differential equations representing the size of congestion window, mean queue at the bottleneck router and loss probability at a RED queue are supplemented with terms representing constant loss probability due to transmission in wireless part and probability that a fraction of these errors is recovered by a link level mechanism. The decrease of congestion window due to TCP mechanism is delayed to allow the link protocol to deal with the errors. The model considers the presence of uncontrollable UDP flows.00353nas a2200109   4500000000100000000000100001008004100002100002400043700002200067700002000089245013400109       2008                            d1 aTadeusz Czachórski1 aKrzysztof Grochla1 aFerhan Pekergin00aUn modele d’approximation de diffusion pour la distribution du temps d’acheminement des paquets dans les réseaux de senseurs00311nas a2200109   4500000000100000000000100001008004100002100002400043700002200067700002000089245009200109       2008                            d1 aTadeusz Czachórski1 aKrzysztof Grochla1 aFerhan Pekergin00aEstimation of packet transfer time at sensor networks, diffusion approximation approach00312nas a2200121   4500000000100000000000100001008004100002260000600043100002400049700002200073700002000095245007500115       2008                            d  c21 aTadeusz Czachórski1 aKrzysztof Grochla1 aFerhan Pekergin00aTCP performance for a wireless traffic, a diffusion approxiation model00321nas a2200121   4500000000100000000000100001008004100002260001700043100002400060700002200084700002000106245007300126       2007                            d  c9bIITiS PAN1 aTadeusz Czachórski1 aKrzysztof Grochla1 aFerhan Pekergin00aFluid-flow Approximation Model of TCP-NCR in wired-wireless networks00748nas a2200157   4500000000100000000000100001000000100002008004100003100002400044700002200068700002000090245003400110300001400144490000700158520042500165       2006                            d1 aTadeusz Czachórski1 aKrzysztof Grochla1 aFerhan Pekergin00aA model of TCP flows dynamics  a279–2920 v183 aThe fluid flow approximation models investigate with much success the dynamics and stability of TCP/RED connections. Their main assumption is that the fluctuations of variables characterizing the behaviour of the connections are relatively small, that enables the linearization of model and the use of traditional control analysis tools to obtain such measures as Bode gain, phase margins, tracking error or delay margin00354nas a2200121   4500000000100000000000100001008004100002260000600043100002400049700002200073700002000095245011700115       2006                            d  c91 aTadeusz Czachórski1 aKrzysztof Grochla1 aFerhan Pekergin00aSome contributions to the modelling the dynamics of (TCP,UDP)/RED flows over reliable and unreliable connections01771nas a2200169   4500000000100000000000100001008004100002260011200043100002400155700002200179700001200201700002000213700002400233245007800257300001400335520125200349       2010                            d  c1bInstitute of Theoretical and Applied Informatics of the Polish Academy of SciencesaGliwice, Bałtycka 51 aTadeusz Czachórski1 aKrzysztof Grochla1 aT. Nycz1 aFerhan Pekergin1 aTadeusz Czachórski00aModeling the IEEE 802.11 Networks MAC Layer Using Diffusion Approximation  a429–4423 aAbstract: The article presents an analytical model of wireless networks using the IEEE 802.11 protocol to access the transport medium. The model allows to determine such key factors of the quality of service as transmission delays and losses. The model is based on diffusion approximation approach which was proposed three decades ago to model wired networks. We show that it can be adapted to take into consideration the input streams with general interarrival time distributions and servers with general service time distributions. The diffusion approximation has been chosen because of fairly general assumptions of models based on it, hard to be represented in Markov models. A queueing network model can have an arbitrary topology, the intensity of transmitted flows can be represented by non-Poisson (even self-similar) streams, the service times at nodes can be defined by general distributions. These assumptions are important: because of the CSMA/CA algorithm, the overall times needed to sent a packet are far from being exponentially distributed and therefore the flows between nodes are non-Poisson. Diffusion approximation allows us also to analyse the of transient behaviour of a network when traffic intensity is changing with time.00918nas a2200181   4500000000100000000000100001008004100002260001800043100002400061700002200085700001200107700002000119700002400139700001800163245003700181300001400218520050400232       2012                            d  c12bIITiS PAN1 aTadeusz Czachórski1 aKrzysztof Grochla1 aT. Nycz1 aFerhan Pekergin1 aTadeusz Czachórski1 aMateusz Nowak00aDuration of boot-up storm period  a145–1503 aThe simultaneous boot of multiple virtual machines or networking devices imposes heavy load on the networking infrastructure. In large network of virtual machines the coordination of the reboots and the device registration is required. In the paper we present a simple analytical model to compute the distribution of boot-up time. The model is verified by comparison to a simulation model, and may be used to check the influence of several parameters on the overall boot-up time during a boot storm.01701nas a2200181   4500000000100000000000100001000000100002008004100003100002400044700002200068700001200090700002000102245012000122300001400242490000700256520124200263022001401505       2010                            d1 aTadeusz Czachórski1 aKrzysztof Grochla1 aT. Nycz1 aFerhan Pekergin00aA diffusion approximation model for wireless networks based on IEEE 802.11 standard, Computer Communication Journal  aS86–S920 v333 aThe article presents an analytical model of wireless networks using the IEEE 802.11 protocol to access the transport medium. The model allows to determine such key factors of the quality of service as transmission delays and losses. The model is based on diffusion approximation approach which was proposed three decades ago to model wired networks. We show that it can be adapted to take into consideration the input streams with general interarrival time distributions and servers with general service time distributions. The diffusion approximation has been chosen because of fairly general assumptions of models based on it, hard to be represented in Markov models. A queueing network model can have an arbitrary topology, the intensity of transmitted flows can be represented by non-Poisson (even self-similar) streams, the service times at nodes can be defined by general distributions. These assumptions are important: because of the CSMA/CA algorithm, the overall times needed to sent a packet are far from being exponentially distributed and therefore the flows between nodes are non-Poisson. Diffusion approximation allows us also to analyse the of transient behaviour of a network when traffic intensity is changing with time.  a0140-366400498nas a2200193   4500000000100000000000100001008004100002260004300043100002100086700002200107700002400129700001400153700002000167700002100187700002400208700002500232245004100257490000600298       2006                            d  bWydawnictwo Komunikacji i Łączności1 aJoanna Domańska1 aKrzysztof Grochla1 aTadeusz Czachórski1 aT. Atmaca1 aStefan Węgrzyn1 aLech Znamirowski1 aTadeusz Czachórski1 aStanisław Kozielski00aNowe Technologie Sieci Komputerowych0 v100637nas a2200121   4500000000100000000000100001008004100002100001900043700002100062700002200083245004800105520036200153       2014                            d1 aPawel Foremski1 aMichał Gorawski1 aKrzysztof Grochla00aSource Model of TCP Traffic in LTE Networks3 aWe propose a generator that represents traffic transmitted in wireless mobile networks. It is based on the measurements of traffic in large scale LTE networks. The proposed tool generates TCP flow sizes and duration. We verify the proposed generator by comparison with traces available in the literature and propose application in discrete event simulators.01743nas a2200181   4500000000100000000000100001000000100002008004100003260000600044100001900050700002100069700002200090700001800112245009100130490000700221520131900228022001401547       2015                            d  c91 aPawel Foremski1 aMichał Gorawski1 aKrzysztof Grochla1 aKonrad Połys00aEnergy-Efficient Crowdsensing of Human Mobility and Signal Levels in Cellular Networks0 v153 aThe paper presents a practical application of the crowdsensing idea to measure human mobility and signal coverage in cellular networks. Currently, virtually everyone is carrying a mobile phone, which may be used as a sensor to gather research data by measuring, e.g., human mobility and radio signal levels. However, many users are unwilling to participate in crowdsensing experiments. This work begins with the analysis of the barriers for engaging people in crowdsensing. A survey showed that people who agree to participate in crowdsensing expect a minimum impact on their battery lifetime and phone usage habits. To address these requirements, this paper proposes an application for measuring the location and signal strength data based on energy-efficient GPS tracking, which allows one to perform the measurements of human mobility and radio signal levels with minimum energy utilization and without any engagement of the user. The method described combines measurements from the accelerometer with effective management of the GPS to monitor the user mobility with the decrease in battery lifetime by approximately 20%. To show the applicability of the proposed platform, the sample results of signal level distribution and coverage maps gathered for an LTE network and representing human mobility are shown.  a1424-822001045nas a2200145   4500000000100000000000100001008004100002260005000043100001900093700002200112700001400134245007000148300001200218520066900230       2015                            d  aSpringer International Publishing Switzerland1 aPawel Foremski1 aKrzysztof Grochla1 aPiotr Gaj00aLTE or WiFi? Client-Side Internet link selection for smartphones.  a43–533 aCurrent mobile phones and tablets are equipped with two technologies for accessing the Internet: WiFi and Cellular. Deciding which of these two interfaces provides faster data transfer is often non-trivial, but most of the currently used devices use a simple priority scheme that prefers WiFi to Cellular. In this paper, we propose a novel system that automatically selects the best link available in the current user location. The system periodically probes the bandwidth available on both links and makes statistical predictions, while avoiding excessive data and battery usage. We experimentally validated our approach using a dedicated application for Android.01203nas a2200145   4500000000100000000000100001008004100002100002100043700002200064245007800086300001400164490000800178520085700186022001401043       2014                            d1 aMichał Gorawski1 aKrzysztof Grochla00aReview of mobility models for performance evaluation of wireless networks  a567–5770 v2423 aPerformance evaluation of protocols and mechanisms in wireless networks require a good representation of client mobility. The number of mobility models has been developed, to emulate the changes of location in time of mobile wireless devices in communication networks, such as e.g. mobile phones, tablets, netbooks, palmtops.Mobility models are used to verify the protocols and algorithms developed for wireless networks in simulation and using analytical tools. The mobility patterns of such devices converges with human movement patterns, as the mobile devices bearers. Among many propositions of human mobility modeling in the literature this paper presents and reviews techniques which are most commonly used or that give very good estimation of actual mobile device bearer behavior. The models are divided into 3 groups: random, social and hybrid.  a2194-535700879nas a2200109   4500000000100000000000100001008004100002100002100043700002200064245003900086520064400125       2013                            d1 aMichał Gorawski1 aKrzysztof Grochla00aThe Real-Life Mobility Model: RLMM3 aThe performance evaluation of mobile wireless networks requires a representation of user mobility. Mobility models are the essential part of such evaluation because they assure examples of mobile nodes movement for typical scenarios. Mobility models provide synthetic traces adjusted to user’s needs. We propose a novel RLMM model that produces synthetic traces of a working human and includes clear division on working days and weekend activities. We describe the model and evaluate it using simulation. The model provides better representation of changes in human behavior on different days than the models available in the literature.00332nas a2200121   4500000000100000000000100001008004100002260002300043100002200066700002400088700002100112245007700133       2001                            d  bIITiS PANaGliwice1 aKrzysztof Grochla1 aTadeusz Czachórski1 aArkadiusz Sochan00aA tool for network traffic generation and transmission delay measurement00264nas a2200109   4500000000100000000000100001008004100002260000900043100002200052700002000074245006000094       2005                            d  bWKŁ1 aKrzysztof Grochla1 aAndrzej Grzywak00aNowe technologie w komputerowych systemach zarządzania00646nas a2200109   4500000000100000000000100001008004100002100002200043245008300065300001200148520037600160       2012                            d1 aKrzysztof Grochla00aSimulation analysis of a virtualization system performance in Boot Up Scenario  a21–243 aThe simultaneous boot of multiple virtual machines or networking devices imposes heavy load on the networking infrastructure. In large network of many virtual machines the coordination of the reboots and device registration is required. In the paper few distributed mechanisms for coordination of virtual machine or network device registration are analyzed by simulation.00266nas a2200109   4500000000100000000000100001000000100002008004100003100002200044245008300066490000700149       2008                            d1 aKrzysztof Grochla00aSimulation Comparison of Active Queue Management Algorithms in TCP/IP Networks0 v3900227nas a2200085   4500000000100000000000100001008004100002100002200043245007600065       2007                            d1 aKrzysztof Grochla00aThe Analysis Of Traffic Shaping In Tcp Connection In Laboratory Network00228nas a2200085   4500000000100000000000100001008004100002100002200043245007700065       2007                            d1 aKrzysztof Grochla00aSimulation Analysis of Active Queue Management Algorithms in IP Networks00244nas a2200109   4500000000100000000000100001000000100002008004100003100002200044245006100066490000700127       2001                            d1 aKrzysztof Grochla00aGenerator pakietów w środowisku sieci heterogenicznych0 v2200260nas a2200109   4500000000100000000000100001000000100002008004100003100002200044245007700066490000700143       2001                            d1 aKrzysztof Grochla00aA tool for network traffic generation and transmission delay measurement0 v1300328nas a2200133   4500000000100000000000100001008004100002260001700043100002200060700002400082700001300106700001600119245005900135       2007                            d  c9bIITiS PAN1 aKrzysztof Grochla1 aTadeusz Czachórski1 aA. Busic1 aJ. Fourneau00aSimulation Analysis of Deflection Routing in Hypercube00422nas a2200145   4500000000100000000000100001008004100002260004500043100002200088700002400110700002300134700002100157700002000178245007800198       2004                            d  bWydawnictwa Naukowo-TechniczneaWarszawa1 aKrzysztof Grochla1 aTadeusz Czachórski1 aPrzemysław Głomb1 aArkadiusz Sochan1 aAndrzej Grzywak00aInternet w społeczeństwie informacyjnym - Podstawowe problemy Internetu00293nas a2200109   4500000000100000000000100001008004100002100002200043700002400065700001700089245007700106       2011                            d1 aKrzysztof Grochla1 aTadeusz Czachórski1 aJerzy Klamka00aNumerical Model of Tcp in 802.16 Networks Using Fluid Flow Approximation00899nas a2200133   4500000000100000000000100001008004100002260000800043100002200051700001900073245007700092300001400169520058200183       2015                            d  bACM1 aKrzysztof Grochla1 aPawel Foremski00aDemo: Wireless Link Selection on Smartphone: Throughput vs Battery Drain  a190–1923 aThe method for automatic selection of wireless interface on smart phones is presented. We consider the selection between WiFi and LTE / 3G radios to maximize the throughput of the data transmission and minimize the amount of energy used to scan and measure the throughput of the network. The proposed selection algorithm defines when to measure and how to estimate the network throughput to balance between the accuracy of the selection and the battery drain caused by the measurements. The link speed estimation method optimized for LTE and WiFi networks is also demonstrated.00262nas a2200097   4500000000100000000000100001008004100002100002200043700001600065245008300081       2005                            d1 aKrzysztof Grochla1 aJ. Fourneau00aSimulation Analysis of Eulerian Routing with Shortcuts in All-optical networks00285nas a2200121   4500000000100000000000100001000000100002008004100003100002200044700002300066245006700089490000700156       2002                            d1 aKrzysztof Grochla1 aPrzemysław Głomb00aKształtowanie ruchu w routerach pracujących w systemie Linux0 v2300741nas a2200145   4500000000100000000000100001008004100002260004500043100002200088700002300110700002100133700002000154245006600174520035500240       2004                            d  bWydawnictwa Naukowo-TechniczneaWarszawa1 aKrzysztof Grochla1 aPrzemysław Głomb1 aArkadiusz Sochan1 aAndrzej Grzywak00aWspółczesne problemy sieci komputerowych - Nowe technologie3 aRozdział przedstawia budowę i wyniki badań symulacyjnych mechanizmu sterowania transmisją sieciową skalowalnego strumienia wideo. Skalowalność typu SNR otrzymywana jest z wykorzystaniem transformaty falkowej, a sterowanie zrealizowane jest z użyciem regulatora proporcjonalno-różniczkującego w oparciu o pomiar opóźnień kolejnych ramek.00249nas a2200097   4500000000100000000000100001008004100002100002200043700001600065245007000081       2006                            d1 aKrzysztof Grochla1 aPiotr Pecka00aThe Markov chain model of RED active queuing management algorithm00269nas a2200097   4500000000100000000000100001008004100002100002200043700001600065245009000081       2006                            d1 aKrzysztof Grochla1 aPiotr Pecka00aAnaliza wydajności mechanizmu RED za pomocą łańcuchów Markowa z czasem ciągłym00700nas a2200157   4500000000100000000000100001008004100002260000600043100002200049700002100071245004600092300001200138490000700150520037100157022001400528       2009                            d  c41 aKrzysztof Grochla1 aArkadiusz Sochan00aAdaptive Streaming of Stereographic Video  a87–940 v393 aWe present a tool for online compression and streaming of stereoscopic video and images and consideration on adaptation of the video stream to network conditions. The software allows to use dierent encoding schema for video compression and streams the stereo frames using UDP protocol. We give measurements of the frame delays in the transmission for dierent codecs.  a1865-092900506nas a2200121   4500000000100000000000100001008004100002100002200043700002100065245004500086490000600131520024700137       2000                            d1 aKrzysztof Grochla1 aArkadiusz Sochan00aSieci prywatne oparte na technologii ATM0 v13 aW artykule opisano koncepcję budowania prywatnych sieci ATM przy wykorzystaniu standardu PNNI. Opisane są możliwości konfiguracyjne przełącznika firmy FORE związane z PNNI. Na koniec opisano strukturę sieci ATM zbudowanej w IITiS PAN.00307nas a2200133   4500000000100000000000100001008004100002260000600043100002200049700002100071700002300092700001500115245004300130       2008                            d  c41 aKrzysztof Grochla1 aArkadiusz Sochan1 aPrzemysław Głomb1 a- Borcochi00aTransmission of scalable video streams00747nas a2200145   4500000000100000000000100001008004100002260004500043100002200088700002100110700002300131700002000154245008000174520034700254       2004                            d  bWydawnictwa Naukowo-TechniczneaWarszawa1 aKrzysztof Grochla1 aArkadiusz Sochan1 aPrzemysław Głomb1 aAndrzej Grzywak00aWspółczesne problemy sieci komputerowych - Zastosowanie i bezpieczeństwo3 aRozdział prezentuje jednolity system autoryzacji użytkowników umożliwiający dostęp do wszytskich zasobów sieci za pomocą jednego hasła. Zaprezentowano rozwiązanie wdrożone w IITiS PAN. Autorzy wykorzystali oprogramowanie firmy Microsoft oraz pakiety dostępne na zasadach open source takie jak: Samba, Dovecot, Apache oraz smbpamd.00310nas a2200109   4500000000100000000000100001008004100002260005100043100002300094700002200117245006100139       2006                            d  bInstytut Informatyki Teoretycznej i Stosowanej1 aPrzemysław Głomb1 aKrzysztof Grochla00aRepresenting single-link traffic quality with kernel PCA00232nas a2200097   4500000000100000000000100001008004100002100002300043700002200066245004600088       2005                            d1 aPrzemysław Głomb1 aKrzysztof Grochla00aModeling Connection State with Kernel PCA00295nas a2200121   4500000000100000000000100001000000100002008004100003100002300044700002200067245007700089490000700166       2002                            d1 aPrzemysław Głomb1 aKrzysztof Grochla00aModelowanie stacji roboczych w sieci ATM przy użyciu symulatora OMNeT++0 v2300893nas a2200145   4500000000100000000000100001008004100002260004500043100002300088700002200111700002100133700002000154245007800174520049500252       2004                            d  bWydawnictwa Naukowo-TechniczneaWarszawa1 aPrzemysław Głomb1 aKrzysztof Grochla1 aArkadiusz Sochan1 aAndrzej Grzywak00aInternet w społeczeństwie informacyjnym - Podstawowe problemy Internetu3 aArtykuł prezentuje przegląd i badania zagadnienia skalowalności w stosowanych współcześnie technologiach kodowania sygnału wideo. W pierwszej części prezentowane są modele skalowalności przyjęte w stosowanych i opracowywanych standardach kompresji, w drugiej przedstawione są wyniki badań jakości transmisji skalowalnych strumieni w różnorodnych warunkach obciążenia. Całość zamknięta jest podsumowaniem możliwości sterowania transmisją sieciową takich strumieni.01274nas a2200145   4500000000100000000000100001008004100002260003200043100001700075700002400092700002200116245007800138300001400216520089800230       2011                            d  bIEEE Computer Society Press1 aJerzy Klamka1 aTadeusz Czachórski1 aKrzysztof Grochla00aModelling TCP Connection in WIMAX Network Using Fluid Flow Approximation.  a502–5073 aThe fluid-flow approximation models have been during last few years to analyze the dynamics and stability of TCP/RED connections in wired networks. The model assumes that the fluctuations of parameters of the connections are relatively low. The fluid flow models base on the linearization and use of control theory analysis tools to verify the stability and behavior of the analyzed system. In this article we use some extensions of fluid flow approximation to support time division multiplexing used in WiMAX wireless networks. We describe the modification of fluid flow equations to incorporate the delivery of packets as an on-off source with on and off times modulated by the WiMAX scheduling algorithm. The results of the fluid flow model have been compared to the measurement in a small test bed. We also show how to analyze the stability of the connection using control theory approach.00337nas a2200145   4500000000100000000000100001008004100002260001300043100001800056700002000074700001600094700002200110245004500132300001400177       2011                            d  bSpringer1 aMateusz Nowak1 aSławomir Nowak1 aPiotr Pecka1 aKrzysztof Grochla00aContent Identification in PI CAN Network  a164–17200417nam a2200169   4500000000100000000000100001008004100002260000800043100002000051700002100071700002200092700002000114700002100134700002200155245004800177020002200225       2009                            d  bWSB1 aSławomir Nowak1 aJoanna Domańska1 aKrzysztof Grochla1 aSławomir Nowak1 aJoanna Domańska1 aKrzysztof Grochla00aSymulator zdarzeń dyskretnych OMNeT++v.3.3  a978-83-88936-70-800307nas a2200121   4500000000100000000000100001008004100002260002400043100002000067700002200087245006200109300001400171       2003                            d  bInformation Society1 aSławomir Nowak1 aKrzysztof Grochla00aSimple Traffic Shaping Algorithm for All-optical Networks  a413–41800351nas a2200145   4500000000100000000000100001000000100002008004100003100002000044700002200064245008400086300001400170490000700184022001400191       2003                            d1 aSławomir Nowak1 aKrzysztof Grochla00aWpływ mechanizmów kształtowania ruchu na wydajność sieci czysto optycznych  a221–2280 v2A  a0208-728601130nas a2200181   4500000000100000000000100001008004100002260005000043100002000093700001800113700002200131700002200153700001400175700001300189245007800202300001200280520065600292       2014                            d  bSpringer International Publishing Switzerland1 aSławomir Nowak1 aMateusz Nowak1 aKrzysztof Grochla1 aAndrzej Kwiecień1 aPiotr Gaj1 aP. Stera00aMAGANET - On the need of realistic topologies for AMI network simulations  a79–883 aThe article proposes MAGANET (Map-based Generator of AMI Network Topology), new map-based topology generator, designated for Advanced Metering Infrastructure (AMI) networks as well as for the urban wireless sensor networks (WSNs). The correct, reliable representation of network topology is crucial for the correct performance evaluation on large multihop wireless networks. Most of the current work us different random topologies. In the article we describe proposed new tool and its features. The comparison of the properties of topology provided by MAGANET for three different generation modes: uniform random, grid and map based is also presented.01116nas a2200145   4500000000100000000000100001008004100002260005000043100001800093700002200111700001400133245007500147300001400222520073400236       2015                            d  bSpringer International Publishing Switzerland1 aKonrad Połys1 aKrzysztof Grochla1 aPiotr Gaj00aMobility robustness in LTE based on automatic neighbor relation table.  a232–2413 aWe evaluate the effect of automatic updates to the LTE Neighbor Relation Table (NRT) to optimize the efficiency of handovers in the network. We propose an algorithm which monitors the handovers within the LTE network and detects events when the procedure was started to early (handover to early) or too late (handover too late). Basing on the observed statistics in Operation and Maintenance server (OAM) the proposed algorithm updates the NRT to maximize the network throughput and minimize the probability of loss of connectivity. Performed simulations show that correctly forbidden handovers can reduce number of unnecessary signaling, reduce risk of fail during handover and reduce the time required to perform the handovers.00771nas a2200145   4500000000100000000000100001008004100002260004500043100002100088700002200109700002300131700002000154245007800174520037300252       2004                            d  bWydawnictwa Naukowo-TechniczneaWarszawa1 aArkadiusz Sochan1 aKrzysztof Grochla1 aPrzemysław Głomb1 aAndrzej Grzywak00aInternet w społeczeństwie informacyjnym - Podstawowe problemy Internetu3 aW rozdziale zarysowano koncepcję usług katalogowych i metody dostępu do nich. Przedstawiono architekturę aplikacji WWW i różne rozwiązania stosowane do tworzenia takich aplikacji. Zaprezentowano wyniki badań porównawczych przeprowadzonych dla tych rozwiązań. Na koniec scharakteryzowano opracowaną aplikację WWW korzystającą z usług katalogowych i XML.00774nas a2200145   4500000000100000000000100001008004100002260004500043100002100088700002300109700002200132700002000154245006600174520038800240       2004                            d  bWydawnictwa Naukowo-TechniczneaWarszawa1 aArkadiusz Sochan1 aPrzemysław Głomb1 aKrzysztof Grochla1 aAndrzej Grzywak00aWspółczesne problemy sieci komputerowych - Nowe technologie3 aW rozdziale opisano prace badawcze dotyczące transmisji strumieni MPEG-2 poprzez kanał o zmiennej przepływności bitowej w sieci ATM. Prace miały charakter zarówno doświadczalno-pomiarowy, jak i analityczny. Określono zależność funkcyjną pomiędzy parametrami ruchu sieci ATM, natężeniem strumienia wideo a jakością transmisji multimedialnej. Zależność powiązano z00933nas a2200193   4500000000100000000000100001008004100002260002500043100001400068700002400082700002200106700001200128700002000140700001700160700001200177245003800189300001400227520049800241       2014                            d  c10bSpringeraLondon1 aT. Atmaca1 aTadeusz Czachórski1 aKrzysztof Grochla1 aT. Nycz1 aFerhan Pekergin1 aErol Gelenbe1 aR. Lent00aA model of boot-up storm dynamics  a371–3793 aThe simultaneous boot of multiple virtual machines or networking devices imposes heavy load on the networking infrastructure. In large network of many virtual machines the coordination of the reboots and device registration is required. In the paper we present a simple analytical model computing the distribution of boot-up time, which is verified by comparison to a simulation model and provide analysis of the influence of several parameters on the overall boot-up time during a boot storm.00271nas a2200121   4500000000100000000000100001008004100002260001300043100002200056700001800078245003900096300001400135       2016                            d  bSpringer1 aKrzysztof Grochla1 aKonrad Połys00aUsing Kalman Filters on GPS Tracks  a663–67200306nas a2200109   4500000000100000000000100001008004100002260001000043100002200053700001800075245010300093       2015                            d  bKSTiT1 aKrzysztof Grochla1 aKonrad Połys00a{Dobór parametrów mechanizmu zwielokrotnienia wykorzystania częstotliwości SFR w sieciach LTE}00557nas a2200145   4500000000100000000000100001008004100002260013200043100002200175700002100197700001800218245010100236856005200337020002200389       2015                            d  bICST (Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering)aICST, Brussels, Belgium, Belgium1 aKrzysztof Grochla1 aMichał Gorawski1 aKonrad Połys00aComparison of Measurements and Simulation Model of Indoor Signal Level Variation in LTE Networks  uhttp://dx.doi.org/10.4108/eai.24-8-2015.2261125  a978-1-63190-079-200312nas a2200121   4500000000100000000000100001008004100002260001300043100002200056700001800078245008000096300001400176       2016                            d  bSpringer1 aKrzysztof Grochla1 aKonrad Połys00aSubcarrier Allocation for LTE Soft Frequency Reuse Based on Graph Colouring  a447–45400268nas a2200109   4500000000100000000000100001008004100002100002100043700002200064700001800086245005400104       2015                            d1 aMichał Gorawski1 aKrzysztof Grochla1 aKonrad Połys00a{Variability of LTE Signal in Indoor Environment}00492nas a2200193   4500000000100000000000100001008004100002260001300043100002900056700002100085700002200106700002800128700001800156700001900174700001500193700001600208245006100224300001300285       2014                            d  bSpringer1 aFrancisco Barcelo-Arroyo1 aMichał Gorawski1 aKrzysztof Grochla1 aIsrael Martín-Escalona1 aKonrad Połys1 aAndrea Ribeiro1 aRute Sofia1 aEnrica Zola00aNew Trends in Mobility Modelling and Handover Prediction  a88–11400376nas a2200157   4500000000100000000000100001008004100002260001300043100002200056700001600078700001100094700002200105700001800127245005900145300001400204       2014                            d  bSpringer1 aGiovanni Giambene1 aTara Yahiya1 aVan Le1 aKrzysztof Grochla1 aKonrad Połys00a{Resource Management and Cell Planning in LTE Systems}  a177–19700270nas a2200097   4500000000100000000000100001008004100002100002200043700001800065245008900083       2014                            d1 aKrzysztof Grochla1 aKonrad Połys00aSimplied model of wireless network throughput changes resulting from client mobility00277nas a2200097   4500000000100000000000100001008004100002100002200043700001800065245009600083       2013                            d1 aKrzysztof Grochla1 aKonrad Połys00aInfluence of the Handoff Threshold Hysteresis on Heterogeneous Wireless Network Performance00311nas a2200109   4500000000100000000000100001008004100002260001000043100002200053700001800075245010800093       2016                            d  bKSTiT1 aKrzysztof Grochla1 aKonrad Połys00aAnaliza wpływu mocy nadawania stacji bazowych na mechanizmy równoważenia obciążenia w sieciach LTE00634nas a2200217   4500000000100000000000100001008004100002260004400043100002000087700001800107700002200125700001600147700002400163700001700187700002200204700001700226245008600243856005100329300001400380020002200394       2016                            d  bSpringer International PublishingaCham1 aSławomir Nowak1 aMateusz Nowak1 aKrzysztof Grochla1 aPiotr Pecka1 aTadeusz Czachórski1 aErol Gelenbe1 aKrzysztof Grochla1 aRicardo Lent00aGlobal Queue Pruning Method for Efficient Broadcast in Multihop Wireless Networks  uhttp://dx.doi.org/10.1007/978-3-319-47217-1_23  a214–224  a978-3-319-47217-101417nas a2200145   4500000000100000000000100001008004100002100002000043700001800063700002200081700001600103245011500119300001200234520102500246       2016                            d1 aSławomir Nowak1 aMateusz Nowak1 aKrzysztof Grochla1 aPiotr Pecka00aEfektywne rozgłaszanie w wielohopowej sieci bezprzewodowej. Effective Broadcasts in Multihop Wireless Network  a887-8913 a<p>Znanych jest wiele rozwiązań problemu rozgłaszania wiadomości w sieciach bezprzewodowych typu ad-hoc. Rozwiązania te różnią się w zależności od wielkości sieci, dostępności informacji o topologii, modelu komunikacji, wymagań gwarancji dostarczenia wiadomości itp. Sieci dedykowane są do różnych zastosowań i różnią się specyfiką występujących w nich problemów związanych z komunikacją. W artykule przedstawiono kilka znanych rozwiązań problemu rozgłaszania oraz przedstawiono autorskie rozwiązanie, dedykowane do specyficznego problemu sieci typu AMI (Advanced Metering Infrastructure - zaawansowana infrastruktura pomiarowa). Sieć ta zakładała model komunikacji jeden-do-wielu, stosunkowo niewielką dynamikę zmian w sieci, możliwość istnienia długich ścieżek na drodze transmisji oraz szereg innych wymagań. Analizowane algorytmy nie spełniały postawionych wymagań. Artykuł opisuje opracowaną motodę i porównuje ją do wybranych rozwiązań referencyjncych.</p>
00305nas a2200121   4500000000100000000000100001008004100002260000800043100002000051700001800071700002200089245007200111       2014                            d  cMay1 aSławomir Nowak1 aMateusz Nowak1 aKrzysztof Grochla00aProperties of advanced metering infrastructure networks' topologies00303nas a2200109   4500000000100000000000100001008004100002260000900043100002200052700002200074245009700096       2014                            d  bIEEE1 aMariusz Słabicki1 aKrzysztof Grochla00aThe automatic configuration of transmit power in LTE networks based on throughput estimation00305nas a2200109   4500000000100000000000100001008004100002260001400043100002200057700002200079245009400101       2015                            d  bCRC Press1 aMariusz Słabicki1 aKrzysztof Grochla00aPerformance evaluation of snmp, netconf and cwmp management protocols in wireless network00261nas a2200109   4500000000100000000000100001008004100002260000900043100002200052700002200074245005500096       2015                            d  bIEEE1 aMariusz Słabicki1 aKrzysztof Grochla00aLocal approach to power management in LTE networks00334nas a2200121   4500000000100000000000100001008004100002260001300043100002200056700002200078245009800100300001400198       2016                            d  bSpringer1 aMariusz Słabicki1 aKrzysztof Grochla00aInfluence of the Management Protocols on the LTE Self-configuration Procedures’ Performance  a439–44600419nas a2200169   4500000000100000000000100001008004100002260000900043100001600052700001500068700001800083700001800101700001600119700002200135700002200157245007000179       2015                            d  bIEEE1 aPavel Masek1 aJiri Hosek1 aYahia Zakaria1 aDalibor Uhlir1 aVit Novotny1 aMariusz Słabicki1 aKrzysztof Grochla00aExperimental evaluation of RAN modelling in indoor LTE deployment00300nas a2200109   4500000000100000000000100001008004100002260001000043100002200053700002200075245009300097       2016                            d  cApril1 aMariusz Słabicki1 aKrzysztof Grochla00aPerformance evaluation of CoAP, SNMP and NETCONF protocols in fog computing architecture00308nas a2200121   4500000000100000000000100001008004100002100001300043700002200056700001300078700002200091245007300113       2016                            d1 aP. Masek1 aMariusz Słabicki1 aJ. Hosek1 aKrzysztof Grochla00aTransmission Power Optimization in Live 3GPP LTE-A Indoor Deployment00278nas a2200097   4500000000100000000000100001008004100002100002200043700002200065245009300087       2016                            d1 aMariusz Słabicki1 aKrzysztof Grochla00a{PyLTEs – Python LTE Evaluation Framework for Quick and Reliable Network Optimization}00372nam a2200169   4500000000100000000000100001000000100002008004100003100002400044700001700068700002200085700001700107245004900124250001300173300000800186490000800194       2016                            d1 aTadeusz Czachórski1 aErol Gelenbe1 aKrzysztof Grochla1 aRicardo Lent00aComputer and Information Sciences ISCIS 2016  aSpringer  a5000 v65900313nas a2200109   4500000000100000000000100001008004100002260002000043100001800063700002200081245010000103       2017                            d  c09/2017aWarsaw1 aKonrad Połys1 aKrzysztof Grochla00aModel zmienności przepływności bitowej transmisji w sieciach LTE oparty o łańcuchy Markowa01158nas a2200229   4500000000100000000000100001000000100002008004100003260004400044100002000088700001800108700002200126700001600148700001400164700002200178700002000200245007300220856004800293300001000341520055500351020002200906       2017                            d  bSpringer International PublishingaCham1 aSławomir Nowak1 aMateusz Nowak1 aKrzysztof Grochla1 aPiotr Pecka1 aPiotr Gaj1 aAndrzej Kwiecień1 aMichał Sawicki00aApplication of Fault-Tolerant GQP Algorithm in Multihop AMI Networks  uhttps://doi.org/10.1007/978-3-319-59767-6_6  a70-803 a<p>The paper presents the evaluation of the GQP algorithm in AMI networks using real map based network topologies (low, medium and high density of buildings). The algorithm was compared to the reference algorithms: CB, SBA and DP. It was shown that the GQP algorithm presents the good scalability, relatively optimal number of selected forwarders and by introducing the redundancy factor, good fault tolerance. An improvement to GQP algorithm to add a redundancy factor is proposed, what allows to execute fault tolerant broadcast transmission.</p>
  a978-3-319-59767-600667nas a2200217   4500000000100000000000100001008004100002260001300043100002200056700001800078700001600096700002000112700001400132700001400146700001700160245010900177856006900286300001200355490006000367020002200427       2017                            d  bSpringer1 aKrzysztof Grochla1 aMateusz Nowak1 aPiotr Pecka1 aSławomir Nowak1 aA Zgrzywa1 aK Choroś1 aA Siemiński00aInfluence of message-oriented middleware on performance of network management system: a modelling study.  uhttps://link.springer.com/chapter/10.1007%2F978-3-319-43982-2_33  a379-3930 vAdvances in Intelligent Systems and Computing, Vol. 506  a978-3-319-43981-501184nas a2200145   4500000000100000000000100001008004100002260003800043100001800081700002200099700002100121245008100142520079300223020002201016       2018                            d  bSpringer International Publishing1 aKonrad Połys1 aKrzysztof Grochla1 aMichał Gorawski00aLTE Load Balancing with Tx Power Adjustment and the Real Life Mobility Model3 a<p>The load balancing in the LTE and LTE-A networks allows usage of the radio resources more effectively to improve client satisfaction. The paper provides analysis of the influence of complex user mobility patterns on the load balancing algorithm. The simulation models are used to evaluate the number of unsatisfied clients depending on the mobility model used. Two mobility models are used: RLMM and Random Waypoint. The Tx Power Adjustment method is evaluated, which is based on reconfiguration of a LTE eNodeB TX Power and was proposed by authors in their previous papers. Method proved to be effective and fairly easy in implementation, and the evaluation through series of simulation shown up to 50{%} rise in clients satisfaction with upholding the total network efficiency.</p>
  a978-3-319-92459-500431nas a2200157   4500000000100000000000100001008004100002260002200043100001800065700002200083700002100105700002200126245006300148300001200211490005000223       2019                            d  c06/2019bSpringer1 aKonrad Połys1 aKrzysztof Grochla1 aMichał Gorawski1 aArtur Frankiewicz00aAccuracy of UWB Location Tracking Devices When on the Move  a233-2410 vInternational Conference on Computer Networks01796nas a2200157   4500000000100000000000100001008004100002260001200043100002000055700002200075245010900097856004500206490000700251520136600258022001401624       2019                            d  c04/20191 aKamil Książek1 aKrzysztof Grochla00aAggregation of GPS, WLAN, and BLE Localization Measurements for Mobile Devices in Simulated Environments  uhttps://www.mdpi.com/1424-8220/19/7/16940 v193 a<p>There are multiple available technologies to find the location of a mobile device, such as the Global Positioning System (GPS), Bluetooth Low-Energy beacons (BLE), and Wireless LAN (WLAN) localization. We propose a novel method to estimate the location of a moving device by aggregating information from multiple positioning systems into a single, more precise location estimation. The aggregated location is calculated as the place in which the product of the probability density functions (PDF) of individual methods has the maximum value. The experimental probability density functions of the three analyzed technologies are fitted by gamma distributions based on error histograms found in the literature and measurement data. The location measurements of the individual technologies are provided at different time instants, so the weighted product of the PDFs is used to improve aggregation accuracy. The discrete event-simulation model was used to evaluate the aggregation method with the Gauss–Markov mobility model. Simulations demonstrated that the calculated aggregated location was more accurate than any of the methods taken as the input, and average error was decreased by almost 13% compared to an arithmetic mean of the three considered localization methods, and by more than 36% compared to the single method with the highest accuracy.</p>
  a1424-822001468nas a2200181   4500000000100000000000100001008004100002260001900043100001900062700002200081700001700103700002700120245007300147490000900220520101300229022002201242020002201264       2019                            d  bSpringer, Cham1 aRafał Marjasz1 aKrzysztof Grochla1 aAnna Strzoda1 aZbigniew Łaskarzewski00aSimulation Analysis of Packet Delivery Probability in LoRa Networks.0 v10393 a<p>The LoRa communication standard allows to transmit data in radio networks over distances of few kilometers. Although the LoRa WAN protocol assumes the use of ALOHA channel access, due to the use of multiple channels and multiple spreading factors in LoRa networks the evaluation of collision probability is challenging. We present the simulation model allowing to estimate the per node probability of successful packet delivery ratio. The model is evaluated for different network topologies, based on random distribution of nodes or based on the real location of meters in sample smart city deployments. The results show that the packet delivery ratio varies significantly depending on the location of the end nodes in the network. Due to the higher spreading factor used, the collision probability is very low for nodes located near to the access point. The use of proposed simulation model allows to identify the nodes which experience high collision probability and react e.g. by reconfiguration.</p>
  a978-3-030-21952-9  a978-3-030-21951-200472nas a2200157   4500000000100000000000100001008004100002260003900043100001800082700002000100700001700120700002200137245006700159856006600226020002200292       2019                            d  bSpringeraKamień Śląski, Poland1 aGodlove Suila1 aPiotr Czekalski1 aErnest Molua1 aKrzysztof Grochla00aAn Architectural Framework Proposal for IoT Driven Agriculture  uhttps://link.springer.com/chapter/10.1007/978-3-030-21952-9_2  a978-3-030-21951-202041nas a2200157   4500000000100000000000100001008004100002260002000043100002200063700002200085245008000107856008200187490000700269520159300276022001401869       2019                            d  c 23 August 20191 aKrzysztof Grochla1 aMariusz Słabicki00aTransmit power optimization in cellular networks with nomadic base stations  uhttps://digital-library.theiet.org/content/journals/10.1049/iet-com.2019.01760 v133 a<p>The increasing demand for cellular network capacity can be mitigated through the installation of nomadic eNodeB, which serve a temporal increase of traffic volume in specific area. When nomadic cells are deployed, the transmission power of neighbour base stations needs to be optimised to limit the inter-cell interferences. The authors analyse the problem of neighbourhood selection for the optimisation, to define what part of the networks needs to be reconfigured when new base station is added. They evaluate the iterative approach, with increasing range of neighbouring cells being reconfigured and propose a novel, sampling-based local TX power reconfiguration method, which is evaluated by a numerical model in both regular (honeycomb) topology and in realistic topology reflecting locations of cells in a city. The analysis confirms that the proposed algorithm allows to select small subset of neighbouring cells to be reconfigured (in majority of the cases <span style="font-size:0.87em"> <span style="font-size:120%"><span style="font-family:mathjax_main">&lt;</span><span style="font-family:mathjax_main">10</span></span></span><span style="font-size:0.87em"> </span> cells), and achieve similar efficacy as global optimisation, with total network throughput different by <span style="font-size:0.87em"> <span style="font-size:120%"><span style="font-family:mathjax_main">&lt;</span><span style="font-family:mathjax_main">1</span><span style="font-family:mathjax_main">%</span></span></span><span style="font-size:0.87em"> </span> comparing to the global optimisation.</p>
  a1751-862800340nas a2200121   4500000000100000000000100001008004100002100002100043700002200064245011900086300000700205490000600212       2020                            d1 aMichał Gorawski1 aKrzysztof Grochla00aPerformance Tests of Smart City IoT Data Repositories for Universal Linear Infrastructure Data and Graph Databases  a310 v100357nas a2200121   4500000000100000000000100001008004100002260000900043100002400052700002200076245007900098856005800177       2019                            d  bIEEE1 aTadeusz Czachórski1 aKrzysztof Grochla00aDiffusion Approximation Models for Cloud Computations with Task Migrations  uhttps://ieeexplore.ieee.org/abstract/document/882182400307nas a2200121   4500000000100000000000100001008004100002100002200043700001900065700001800084700001700102245006600119       2019                            d1 aKrzysztof Grochla1 aRafał Marjasz1 aKonrad Połys1 aAnna Strzoda00aKolizje pakietów w sieciach LoRa w zastosowaniach smart city01290nas a2200133   4500000000100000000000100001008004100002260003500043100002100078700002200099245007700121520093600198020002201134       2019                            d  c10.2019bIEEEaDublin, Ireland1 aMichał Gorawski1 aKrzysztof Grochla00a"Graph Representation of Linear Infrastructure in Smart City IoT Systems3 a<p>The cities infrastructure is being populated with a large number of Internet-connected devices used for monitoring and management to create a Smart City system. A large part of the city infrastructure has linear form, such as e.g. roads, energy or water distribution networks. In this paper, we present a solution for representation, processing and providing to external IT systems the data related to linear infrastructure. We present the idea of representation of such networks in a form of a multigraph that is stored in graph database and the graph generator which merges the data gathered from monitoring devices with network topology and other representative structures. We propose the architecture of a sample linear infrastructure management system based on multi-graph representation and discuss how it proposes a performance evaluation method based on data generation on the example of a district heating system.</p>
  a978-1-7281-5763-400480nas a2200169   4500000000100000000000100001008004100002260001300043100002200056700001700078700002400095700001700119700002200136700001700158245008600175856004900261       2018                            d  bSpringer1 aOlumide Akinwande1 aErol Gelenbe1 aTadeusz Czachórski1 aErol Gelenbe1 aKrzysztof Grochla1 aRicardo Lent00aA Reinforcement Learning Approach to Adaptive Forwarding in Named Data Networking  uhttps://doi.org/10.1007/978-3-030-00840-6_2300514nas a2200157   4500000000100000000000100001008004100002260001300043100002400056700001700080700002200097700001700119245019000136490000800326020002200334       2018                            d  bSpringer1 aTadeusz Czachórski1 aErol Gelenbe1 aKrzysztof Grochla1 aRicardo Lent00aComputer and Information Sciences - 32nd International Symposium, ISCIS 2018, Held at the 24th IFIP World Computer Congress, WCC 2018, Poznan, Poland, September 20-21, 2018, Proceedings0 v935  a978-3-030-00839-001346nas a2200133   4500000000100000000000100001008004100002260002000043100002200063700001800085245008400103856005800187520096700245       2020                            d  c07/2020aCyprus1 aKrzysztof Grochla1 aKonrad Połys00aHeuristic Algorithm for Gateway Location Selection in Large Scale LoRa Networks  uhttps://ieeexplore.ieee.org/abstract/document/91484353 a<p>The LoRa networks allow building low-cost longrange networks. The selection of LoRa access point locations in large scale networks requires taking into consideration the spatial distribution of clients, radio signal propagation and the limitation of the number of devices served by a single point of access. We propose a heuristic algorithm for the selection of access point locations within for a given set of candidate locations, based on gradient optimization. The proposed method allows selecting a sub-optimal set of locations which provide full coverage and take into consideration the capacity dimensioning based on spreading factor and expected channel utilization. The algorithm is evaluated in random topologies and in reallife scenario based on city-wide smart meters locations. The analysis shows that it outperforms a manual selection of access points locations, allowing to decrease the number of access points providing the full coverage.</p>
00386nas a2200145   4500000000100000000000100001008004100002260003000043100001900073700001700092700002000109700002200129245006700151020002200218       2019                            d  cJune 2019bSpringer, Cham1 aGodlove Kuaban1 aErnest Molua1 aPiotr Czekalski1 aKrzysztof Grochla00aAn Architectural Framework Proposal for IoT Driven Agriculture  a978-3-030-21951-201441nas a2200205   4500000000100000000000100001008004100002260002200043100002200065700001400087700002200101700002700123700002200150700001800172700002500190700001700215245008000232856003700312520088600349       2020                            d  c01/2021bSpringer1 aArtur Frankiewicz1 aAdam Glos1 aKrzysztof Grochla1 aZbigniew Łaskarzewski1 aJaroslaw Miszczak1 aKonrad Połys1 aPrzemysław Sadowski1 aAnna Strzoda00aLP WAN Gateway Location Selection Using Modified K-Dominating Set Algorithm  uhttps://arxiv.org/abs/2010.045533 a<p>The LP WAN networks use gateways or base stations to communicate with devices distributed on large distances, up&nbsp;to tens of kilometres. The selection of optimal gateway locations in wireless networks should allow providing the complete coverage for a given set of nodes, taking into account the limitations, such as the number of nodes served per access point or required redundancy. In this paper, we describe the problem of selecting the base stations in a network using the concept of <em>k</em>-dominating set. In our model, we include information about the required redundancy and spectral efficiency. We consider the additional requirements on the resulting connections and provide the greedy algorithm for solving the problem. The algorithm is evaluated in randomly generated network topologies and using the coordinates of sample real smart metering networks.</p>
01790nas a2200169   4500000000100000000000100001008004100002260001200043100002100055700002200076700001900098700002200117245011500139856004500254490000700299520131400306       2021                            d  c01/20211 aMichał Gorawski1 aKrzysztof Grochla1 aRafał Marjasz1 aArtur Frankiewicz00aEnergy Minimization Algorithm for Estimation of Clock Skew and Reception Window Selection in Wireless Networks  uhttps://www.mdpi.com/1424-8220/21/5/17680 v213 a<p>The synchronization of time between devices is one of the more important and challenging problems in wireless networks. We discuss the problem of maximization of the probability of receiving a message from a device using a limited listening time window to minimize energy utilization. We propose a solution to two important problems in wireless networks of battery-powered devices: a method of establishing a connection with a device that has been disconnected from the system for a long time and developed unknown skew and also two approaches to follow-up clock synchronization using the confidence interval method. We start with the analysis of measurements of clock skew. The algorithms are evaluated using extensive simulations and we discuss the selection of parameters balancing between minimizing the energy utilization and maximizing the probability of reception of the message. We show that the selection of a time window of growing size requires less energy to receive a packet than using the same size of time window repeated multiple times. The shifting of reception windows can further decrease the energy cost if lower packet reception probability is acceptable. We also propose and evaluate an algorithm scaling the reception window size to the interval between the packet transmission</p>
00293nas a2200109   4500000000100000000000100001008004100002260002400043100002000067700002200087245007400109       2021                            d  bIEEEaHarbin, China1 aKamil Książek1 aKrzysztof Grochla00aFlexibility Analysis of Adaptive Data Rate Algorithm in LoRa Networks01795nas a2200181   4500000000100000000000100001008004100002260002700043100001900070700001700089700001800106700002200124245006500146856011600211300001200327520125200339022002201591       2021                            d  c10/2021bEurosisaRome1 aRafał Marjasz1 aAnna Strzoda1 aKonrad Połys1 aKrzysztof Grochla00aMitigation of LoRa interferences via dynamic channel weights  uhttps://www.researchgate.net/publication/356041519_Mitigation_of_LORA_Interferences_via_Dynamic_Channel_Weights  a150-1543 a<p>The Low Power Wide Area Networks, such as LoRa (Long Range), allow communication over a large area with limited bandwidth and small data rates, using an unlicensed band. LoRa uses multiple channels, but the number of channels available is relatively narrow - e.g. 8 in most countries in Europe. The transmission is subject to interferences due to many other devices transmitting within the same frequencies. In this paper, we evaluate how strong the interferences' influence is by analysing the packet delivery rate in a large scale LoRa network. The measurements have been made over more than seven months and show noticeable variability in packet delivery rate per channel both in space and in time. We propose to estimate the scale of interferences through continuous observation of the number of delivered packets for every channel per LoRa gateway or per selected area. We also discuss how this estimation may mitigate the interferences by assigning the dynamic weights to the LoRa channel selection procedure. We created an algorithm that periodically updates the weights, and a simulation model to evaluate the algorithm. A significant improvement in the efficiency of package delivery is visible, from 12% to 49% less packet loss.</p>
  a978-9-492-85918-101878nas a2200169   4500000000100000000000100001008004100002260005900043100001900102700001800121700001700139700002200156245004500178856006700223520140000290020001801690       2021                            d  bAssociation for Computing MachineryaNew York, NY, USA1 aRafał Marjasz1 aKonrad Połys1 aAnna Strzoda1 aKrzysztof Grochla00aImproving Delivery Ratio in LoRa Network  uhttps://dl.acm.org/doi/10.1145/3479241.3486698?cid=996599133973 a<p>The LoRa (Long Range) radio communication provides large coverage areas, low bandwidth, small data rates, and transmitting limited data sizes, with very low energy usage. Multiple transmission channels are used, but the number of channels available is fairly limited - e.g. 8 in most countries in Europe. The amount of interferences may be estimated by the continuous observation of the number of delivered packets and the received signal strength. We propose to aggregate and analyse those metrics per channel and geographical area. When the proportion of received packets per some of the areas decreases, it is subjected to heavier interferences than other parts of the network and should be used less intensively. Thus we propose to allocate the weights for each channel per geographic area and/or device, defining the probability of the channel usage. Furthermore, we created an algorithm that periodically updates the weights and a simulation model using OMNeT++, FloRa, taking into account possible packets collisions. The algorithm has been validated for both random and realistic network topologies. The simulation evaluations show a significant improvement in the package delivery efficiency, by almost 50% in scenarios with very high interference level simulated and by more than 13% in scenarios fed with real-life measurements of packet delivery probability changes in time.</p>
  a978145039079801636nas a2200157   4500000000100000000000100001008004100002260005500043100001700098700002200115700001500137245007400152856006700226520116300293020002201456       2021                            d  c12/2021bSpringer International PublishingaWrocla1 aDaniel Marek1 aKrzysztof Grochla1 aJakub Duda00aChannel State Information Variability in BLE Positioning Measurements  uhttps://link.springer.com/chapter/10.1007/978-3-030-92604-5_263 a<p>The Bluetooth Low Energy beacon messages are used in indoor positioning systems (IPS) to estimate the distance between the wireless devices. Recent work shows that channel state information and separate measurements for each of the three channels may increase the accuracy of the IPS, especially using the fingerprinting method. We perform a set of measurements presenting RSSI variability per channel in stationary measurements and with a variation of angle between the beacon and the receiver. The estimated standard deviation of the RSSI (received signal strength index) is minimal (less than one dBm) for stationary transmission. However, our measurements show that if the angle is not constant, the signal level of beacons received on different channels changes by up&nbsp;to 8 dBm, and the channel state is not a reliable source of information for distance estimation. We show that since mobile phones antennas are not perfectly omnidirectional and the multipath fading significantly changes even with a slight turn of the receiver, the channel state information in the BLE positioning system has limited applicability in real-life conditions.</p>
  a978-3-030-92604-500491nas a2200193   4500000000100000000000100001000000100002008004100003260004800044100002200092700002400114700001700138700002200155700001800177245006400195300000800259490000800267020002200275       2021                            d  bSpringeraVirtual Event, June 28–29, 20211 aAleksander Byrski1 aTadeusz Czachórski1 aErol Gelenbe1 aKrzysztof Grochla1 aYuko Murayama00aComputer Science Protecting Human Society Against Epidemics  a1250 v616  a978-3-030-86582-501607nas a2200193   4500000000100000000000100001008004100002260001200043100002200055700001700077700001900094700002300113700002000136700002700156245006100183856005900244490000700303520110300310       2022                            d  c11/20221 aKrzysztof Grochla1 aAnna Strzoda1 aRafał Marjasz1 aPrzemysław Głomb1 aKamil Książek1 aZbigniew Łaskarzewski00aEnergy-Aware Algorithm for Assignment of Relays in LPWAN  uhttps://dl.acm.org/doi/10.1145/3544561?cid=996599133970 v183 a<p>The Low Power Wide Area Networks allow maintaining connectivity with devices over a distance of a few kilometres. However, due<br />
to the presence of obstacles the communication range in an urban environment may be shorter, which creates multiple blind spots or<br />
areas with limited coverage. The nodes acting as relays may solve this problem by forwarding the data from other devices with poor<br />
connectivity. We propose and investigate a novel algorithm that assigns devices to the relay role while keeping the battery constraints.<br />
We define the algorithm, describe the simulation testbed, and present performance evaluation in several scenarios, including real-life<br />
topologies of IoT networks. The proposed relay selection scheme allows increasing the lifetime of the network by selecting the relay<br />
taking into account the current battery capacity. Additionally, it outperforms a previously proposed relay selection algorithm for LP<br />
WAN, showing an average 4% decrease in transmission time and an order of magnitude lower computation complexity.</p>
00424nas a2200145   4500000000100000000000100001008004100002260002900043100001700072700002200089700002200111700002700133245006900160856004900229       2022                            d  bIEEEaDubrovnik, Croatia1 aAnna Strzoda1 aKrzysztof Grochla1 aArtur Frankiewicz1 aZbigniew Łaskarzewski00aMeasurements and Analysis of Large Scale LoRa Network Efficiency  uhttps://ieeexplore.ieee.org/document/982431700456nas a2200145   4500000000100000000000100001008004100002100002200043700002200065700001800087700001600105245011000121856007200231490000700303       2025                            d1 aViacheslav Kovtun1 aKrzysztof Grochla1 aOksana Kovtun1 aOleh Yasniy00aThe quality of service assessment of eMBB and mMTC traffic in a clustered 5G ecosystem of a smart factory  uhttps://www.sciencedirect.com/science/article/pii/S11108665240016100 v2901805nas a2200157   4500000000100000000000100001008004100002260006700043100001700110700002200127700001800149245012800167856005500295520127900350020001801629       2022                            d  c10/2022bAssociation for Computing MachineryaMontreal, Canada1 aAnna Strzoda1 aKrzysztof Grochla1 aKonrad Połys00aVariability of BLE Advertisement Packets Received Signal Strength and Delivery Probability in the Presence of Interferences  uhttps://dl.acm.org/doi/abs/10.1145/3551662.35609333 a<p>The Bluetooth Low Energy (BLE) advertisement messages allow estimating the location and distance between mobile devices. We analyse how the signal level varies depending on interferences, distance and the orientation of the transmitting and receiving devices. To provide a representative BLE Received Signal Strength Index (RSSI) dataset, we present a series of experimental measurements, including different receiver antenna orientations for several distances. We analyse the signal level variability as a function of distance and angle in an indoor environment. Our measurements show that the mean RSSI value equals -65.5 dBm, -78.4 dBm, -84.1 dBm and -90.8 dBm for 1m, 5m, 10m, and 16m, respectively. The standard deviation changes from 5.7 dBm through 5.9 dBm, 4.5 dBm to 3.5 dBm for 1m, 5m, 10m, and 16m, respectively. We also investigate the influence of the interference, emulating environment in which devices actively transmit BLE signals with varying intensities; on average, at every 0ms (no additional signals), 4ms and 8ms. The experiments show that from 13% to 40% fewer packets are delivered per second in the presence of interferences. Nevertheless, the RSSI characteristics remain very similar regardless of the presence of emulated traffic or not.</p>
  a978145039482601556nas a2200157   4500000000100000000000100001008004100002260006800043100001700111700001900128700002200147245006200169856006700231520108200298020001801380       2022                            d  c10/2022bAssociation for Computing MachineryaNew York, NY, USA1 aAnna Strzoda1 aRafał Marjasz1 aKrzysztof Grochla00aHow Accurate is LoRa Positioning in Realistic Conditions?  uhttps://dl.acm.org/doi/10.1145/3551662.3561260?cid=996599133973 a<p>The LoRa communication technology has been developed for data transmission, but recent research papers showed that it could also be used to estimate the transmitting devices' location. The location can be found with reasonable accuracy, with median error as low as tens of meters; however, in many cases, it is evaluated in very optimistic transmission conditions, e.g. using line-of-sight communication and on a small data set. We estimate how LoRa localization performs in a realistic scenario, using an extensive data set of a telemetric network of a few thousand devices to calculate the location using the trilateration and estimate the error of the calculation. Within the analysed dataset the true-range multilateration provides highly inaccurate location estimation, with a median error of 588.64 m and an average error of 808.57 m. We argue that the LoRa localization in real-life conditions is ineffective, as the estimation of the distance between the node and the gateway changes heavily depending on the location of the node and radio channel attenuation.</p>
  a978145039482601594nas a2200145   4500000000100000000000100001008004100002260005400043100001700097700001900114700002200133245006800155856004700223520117800270       2022                            d  c12/2022bInfocommunications JournalaNice, France1 aAnna Strzoda1 aRafał Marjasz1 aKrzysztof Grochla00aLoRa Positioning in Verification of Location Data's Credibility  uhttps://www.infocommunications.hu/2022_4_83 a<p>The LoRa is a novel radio communication technology<br />
providing low power and a high range of data transmission.<br />
The LoRa transmission may be used for a low-cost localization<br />
to estimate the network nodes’ location. Some recent research<br />
showed that the location could be found with reasonable accuracy,<br />
with median error as low as tens of meters. Still, such results are<br />
achieved in a controlled environment with low interferences. We<br />
first evaluate the LoRa localization using an extensive data set<br />
of a telemetric network of a few thousand devices. We show that<br />
although the direct positioning based on trilateration provides<br />
limited accuracy, the measurement of LoRa transmission may<br />
be successfully used to evaluate the credibility of location information.<br />
The information about which gateways received the data<br />
and the RSSI measurements allow us to verify if the potential<br />
coordinates of a location are accurate. We propose a metric for<br />
location verification and estimate its credibility on a sample of<br />
measurements from the LoRa telemetry network.</p>
00728nas a2200277   4500000000100000000000100001008004100002100001600043700001900059700002100078700001400099700001700113700002200130700002400152700001700176700001900193700002200212700002000234700001800254700001900272700001700291700001600308700001600324245004700340856006300387       2022                            d1 aAlpen Yegin1 aOlivier Seller1 aDavide Orifiamma1 aXiaobo Yu1 aBrince Thanh1 aDominique Barthel1 aChristopher Buffard1 aInma Carrion1 aLoïc Ferreira1 aKrzysztof Grochla1 aMichael Grudsky1 aAhmed Kasttet1 aMichael Kirwan1 aDave Kjendal1 aMiguel Luis1 aBaozhu Ning00aLoRaWAN® Relay Specification  TS011-1.0.0  uhttps://resources.lora-alliance.org/home/ts011-1-0-0-relay00340nas a2200133   4500000000100000000000100001008004100002260003800043100001700081700002200098700002300120700001800143245004500161       2023                            d  c07/2023bIEEEaMarrakesh, Morocco1 aAnna Strzoda1 aKrzysztof Grochla1 aPrzemysław Głomb1 aAndrzej Madej00aLink failure prediction in LoRa networks01877nas a2200169   4500000000100000000000100001008004100002260003800043100002000081700002200101700002200123700002100145245009300166856005000259300001400309520138400323       2023                            d  c07/2023bIEEEaMarrakesh, Morocco1 aSławomir Nowak1 aKrzysztof Grochla1 aMariusz Słabicki1 aMichał Gorawski00aEfficient Universal Indoor Multicharacteristic Propagation model for indoor environments  uhttps://ieeexplore.ieee.org/document/10183073  a1052-10583 a<p>Accurate indoor radio propagation modelling is a well-known problem that researchers tend to solve in many ways. Related methods differ in terms of accuracy and complexity. The article’s contribution is a new stochastic propagation model, Universal Indoor Multicharacteristic Propagation (UIMP), which results are statistically consistent with those measured in a real environment. The model could be used to verify real- world applications due to the low computational complexity and high accuracy level compared to state-of-the-art methods. This method can be especially beneficial for the efficient modelling of complex environments shared by many users using discrete events simulations (DES) based on a series of measurements in a real environment. In the article, we describe the method and present how to establish the model. The motivation was to develop an efficient method for use in an actual application: using the Bluetooth Low Energy (BLE) signal to estimate the position of users in indoor environments – the use of the proposed UIMP model allowed for a reliable assessment of the developed functionalities. Therefore we also present how the model was used to evaluate an example, real functionality, showing that the use of simplified models may falsify the assessment of the analyzed method and may lead e.g. to incorrect implementation assumptions.</p>
00446nas a2200145   4500000000100000000000100001008004100002260001200043100002200055700002200077700001800099245013000117856004600247490000700293       2023                            d  c11/20231 aViacheslav Kovtun1 aKrzysztof Grochla1 aKonrad Połys00aInvestigation of the Information Interaction of the Sensor Network end IoT Device and the Hub at the Transport Protocol Level  uhttps://www.mdpi.com/2079-9292/12/22/46620 v1200499nas a2200181   4500000000100000000000100001008004100002260002100043100002200064700001900086700002200105700002200127700001800149245008200167856004600249490000700295022001500302       2023                            d  c21 November 20231 aViacheslav Kovtun1 aElena Zaitseva1 aVitaly Levashenko1 aKrzysztof Grochla1 aOksana Kovtun00aSmall Stochastic Data Compactification Concept Justified in the Entropy Basis  uhttps://www.mdpi.com/1099-4300/25/12/15670 v25  a1099-4300 00512nas a2200157   4500000000100000000000100001008004100002260001200043100002200055700002200077700001900099700001800118245016500136856004600301490000700347       2023                            d  c12/20231 aViacheslav Kovtun1 aKrzysztof Grochla1 aWojciech Kempa1 aKonrad Połys00aReliably Controlling Massive Traffic between a Sensor Network End Internet of Things Device Environment and a Hub Using Transmission Control Protocol Mechanisms  uhttps://www.mdpi.com/2079-9292/12/24/49200 v1200507nas a2200157   4500000000100000000000100001008004100002260001200043100002200055700002200077700001900099700002300118245011600141856007800257022001400335       2023                            d  c12/20231 aViacheslav Kovtun1 aKrzysztof Grochla1 aTorki Altameem1 aMohammed Al-Maitah00aEvaluation of the QoS policy model of an ordinary 5G smart city cluster with predominant URLLC and eMBB traffic  uhttps://journals.plos.org/plosone/article?id=10.1371/journal.pone.0295252  a1932-620300531nas a2200181   4500000000100000000000100001008004100002260001200043100002200055700002200077700002600099700001300125700001800138245011000156856006200266490000700328022001400335       2023                            d  c12/20231 aViacheslav Kovtun1 aKrzysztof Grochla1 aViacheslav Kharchenko1 aMohd Haq1 aAndiy Semenov00aStochastic forecasting of variable small data as a basis for analyzing an early stage of a cyber epidemic  uhttps://www.nature.com/articles/s41598-023-49007-2#citeas0 v13  a2045-232201853nas a2200145   4500000000100000000000100001008004100002260001200043100001700055700002200072245010700094856004600201490000700247520145300254       2024                            d  c05/20241 aAnna Strzoda1 aKrzysztof Grochla00aA Nature-Inspired Approach to Energy-Efficient Relay Selection in Low Power Wide Area Networks (LPWAN)  uhttps://www.mdpi.com/1424-8220/24/11/33480 v243 a<p>Despite the ability of Low-Power Wide-Area Networks to offer extended range, they encounter challenges with coverage blind spots in the network. This article proposes an innovative energy-efficient and nature-inspired relay selection algorithm for LoRa-based LPWAN networks, serving as a solution for challenges related to poor signal range in areas with limited coverage. A swarm behavior-inspired approach is utilized to select the relays’ localization in the network, providing network energy efficiency and radio signal extension. These relays help to bridge communication gaps, significantly reducing the impact of coverage blind spots by forwarding signals from devices with poor direct connectivity with the gateway. The proposed algorithm considers critical factors for the LoRa standard, such as the Spreading Factor and device energy budget analysis. Simulation experiments validate the proposed scheme’s effectiveness in terms of energy efficiency under diverse multi-gateway (up to six gateways) network topology scenarios involving thousands of devices (1000–1500). Specifically, it is verified that the proposed approach outperforms a reference method in preventing battery depletion of the relays, which is vital for battery-powered IoT devices. Furthermore, the proposed heuristic method achieves over twice the speed of the exact method for some large-scale problems, with a negligible accuracy loss of less than 2%.</p>
00459nas a2200145   4500000000100000000000100001008004100002260001100043100002200054700002200076700001800098245011800116856007200234490000700306       2024                            d  c5/20241 aViacheslav Kovtun1 aKrzysztof Grochla1 aKonrad Połys00aThe concept of network resource control of a 5G cluster focused on the smart city's critical infrastructure needs  uhttps://www.sciencedirect.com/science/article/pii/S11100168240028250 v9400500nas a2200157   4500000000100000000000100001008004100002260001100043100002200054700001800076700002200094700001800116245015200134856004900286490000700335       2024                            d  c3/20241 aViacheslav Kovtun1 aOksana Kovtun1 aKrzysztof Grochla1 aKonrad Połys00aAssessment of Communication Resource Allocation by the Transmission Control Protocol for the Target Virtual Connection under Competitive Conditions  uhttps://www.mdpi.com/2079-9292/13/7/1180/pdf0 v1301207nas a2200157   4500000000100000000000100001008004100002260003200043100002100075700001900096700002200115700002200137245011700159856005000276520072300326       2024                            d  c08/2024bIEEEaThessaloniki1 aMichał Gorawski1 aRafał Marjasz1 aKrzysztof Grochla1 aArtur Frankiewicz00aComparative Analysis of Energy Consumption in Simulated LoRa Water Meter Reconfiguration vs. Real-world Readings  uhttps://ieeexplore.ieee.org/document/106198613 a<p>Detecting water leaks in distribution networks is crucial for conserving resources and preventing infrastructure damage. However, one of the most basic and significant challenges before employing any leak detection method is collecting data from the water distribution network. The sensors used for data collection are usually battery-powered; thus, the energy consumption of these devices is an essential factor. In this paper, we analyze the battery consumption of real devices placed in an operational water distribution network, and based on the obtained data, we perform a series of complex simulations to validate the preliminary assumptions we plan to use in further research of leak detection methods.</p>
02017nas a2200157   4500000000100000000000100001008004100002260001200043100001900055700002200074700001800096245013600114856005500250490000700305520154700312       2024                            d  c06/20241 aRafał Marjasz1 aKrzysztof Grochla1 aKonrad Połys00aA Comprehensive Algorithm for Vertical Positioning in Multi-Building Environments as an Advancement in Indoor Floor-Level Detection  uhttps://www.nature.com/articles/s41598-024-64824-90 v143 a<p>The proliferation of smartphones has catalyzed diverse services, mainly focusing on indoor localization to determine users’ and devices’ positions within buildings. Despite decades of exploration, the seamless integration of wireless technologies in tracking devices and users has become pivotal in various sectors, including health, industry, disaster management, building operations, and surveillance. Extensive research in laboratory and industrial settings, particularly in wireless sensor networks and robotics, has informed indoor localization techniques. This paper, referencing surveys and original literature reviews, proposes an innovative indoor location system amalgamating GPS and barometer readings. GPS identifies entry through doors, while barometer readings facilitate accurate floor-level tracking. The integration promises continuous real-time location updates, enhancing security, navigation, and emergency response. Notably, the algorithm is infrastructure-independent, relying on the smartphone’s barometer, and versatile, detecting elevator travel when Wi-Fi AP or LTE signals are available. Results indicate high accuracy, with building entry exceeding 93%, elevator recognition achieving 75% sensitivity and 97% specificity, and floor change detection surpassing 95% sensitivity and nearly 98% specificity (which translates to nearly 97% accuracy). This comprehensive solution, emphasizing the critical role of precise vertical positioning, signifies an advancement in tracking within urban structures.</p>
01016nas a2200145   4500000000100000000000100001008004100002260004200043100002100085700001900106700002200125245012700147520057400274020002200848       2024                            d  c06/2024bEUROSIS-ETIaValencia, Spain1 aMichał Gorawski1 aRafał Marjasz1 aKrzysztof Grochla00aPerformance evaluation of the secure multi-tenancy system for smart city IoT environment using open LDAP and Apache Kafka.3 a<p>Supporting multiple users and operators in a single IoT system is vital for large-scale commercial deployments. This involves servicing numerous network operators with one IT system and set of devices, ensuring each operator can manage, reconfigure, and change device settings securely. This paper evaluates a multi-tenancy solution in our test system (TS), utilizing Apache Kafka as a message broker and OpenLDAP as an authorizer. It describes the system design, methods to ensure data separation, security and results of performance evaluation in simulation.</p>
  a978-9-492859-30-300488nas a2200145   4500000000100000000000100001008004100002100002200043700002200065700001800087700002300105245014400128856006300272490000700335       2024                            d1 aViacheslav Kovtun1 aKrzysztof Grochla1 aSaad Aldosary1 aMohammed Al-Maitah00aAnalysis of direct traffic at the transport protocol level in the WiMax-1/2 cluster oriented to offload the smart city's wireless ecosystem  uhttps://royalsocietypublishing.org/doi/10.1098/rsos.2402060 v1101131nas a2200133   4500000000100000000000100001008004100002260003200043100002700075700002200102245010300124856019300227520057700420       2024                            d  c09/2024bSIGMA-NOTaPoznań1 aZbigniew Łaskarzewski1 aKrzysztof Grochla00aEfektywność Schematu Komunikacyjnego Liczników Mediów w Procesie Zdalnego Odczytu Obchodzonego  uhttps://sigma-not.pl/publikacja-150436-efektywno%C5%9B%C4%87-schematu-komunikacji-licznik%C3%B3w-medi%C3%B3w-w-procesie-zdalnego-odczytu-obchodzonego-przeglad-telekomunikacyjny-2024-4.html3 a<p>Liczniki mediów coraz częściej wyposażane są w możliwość zdalnego odczytu wskazań. Jest on realizowany w modelu stacjonarnym lub obchodzonym. W modelu ob- chodzonym najpopularniejszym schematem komunikacji jest periodyczne nadawanie ramek pomiarowych, jednak jak pokazuje analiza w niniejszej pracy, schemat komunika- cji oparty na energooszczędnym nasłuchu (próbkowaniu preambuły) jest bardziej energooszczędny, a także wymaga mniej czasu na realizację transmisji. Wskazane także zostały parametry mające wpływ na wybór schematu komunikacji.</p>
00670nas a2200169   4500000000100000000000100001008004100002260001200043100002200055700002200077700002300099700001800122700002200140245010800162856022300270490000700493       2024                            d  c12/20241 aViacheslav Kovtun1 aKrzysztof Grochla1 aMohammed Al-Maitah1 aSaad Aldosary1 aTetiana Gryshchuk00aCyber epidemic spread forecasting based on the entropy-extremal dynamic interpretation of the SIR model  uhttps://www.sciencedirect.com/science/article/pii/S111086652400135X?utm_campaign=STMJ_219742_AUTH_SERV_PA&utm_medium=email&utm_acid=57370081&SIS_ID=&dgcid=STMJ_219742_AUTH_SERV_PA&CMX_ID=&utm_in=DM523185&utm_source=AC_0 v2802800nas a2200193   4500000000100000000000100001008004100002260001200043100002200055700002200077700002300099700001800122700001900140245009200159856007200251490000700323520226200330022001402592       2024                            d  c12/20241 aViacheslav Kovtun1 aKrzysztof Grochla1 aMohammed Al-Maitah1 aSaad Aldosary1 aWojciech Kempa00aEntropy-extreme model for predicting the development of cyber epidemics at early stages  uhttps://www.sciencedirect.com/science/article/pii/S20010370240027700 v243 a<p>The approaches used in biomedicine to analyze epidemics take into account features such as exponential growth in the early stages, slowdown in dynamics upon saturation, time delays in spread, segmented spread, evolutionary adaptations of the pathogen, and preventive measures based on universal communication protocols. All these characteristics are also present in modern cyber epidemics. Therefore, adapting effective biomedical approaches to epidemic analysis for the investigation of the development of cyber epidemics is a promising scientific research task. The article is dedicated to researching the problem of predicting the development of cyber epidemics at early stages. In such conditions, the available data is scarce, incomplete, and distorted. This situation makes it impossible to use artificial intelligence models for prediction. Therefore, the authors propose an entropy-extreme model, defined within the machine learning paradigm, to address this problem. The model is based on estimating the probability distributions of its controllable parameters from input data, taking into account the variability characteristic of the last ones. The entropy-extreme instance, identified from a set of such distributions, indicates the most uncertain (most negative) trajectory of the investigated process. Numerical methods are used to analyze the generated set of investigated process development trajectories based on the assessments of probability distributions of the controllable parameters and the variability characteristic. The result of the analysis includes characteristic predictive trajectories such as the average and median trajectories from the set, as well as the trajectory corresponding to the standard deviation area of the parameters’ values. Experiments with real data on the infection of Windows-operated devices by various categories of malware showed that the proposed model outperforms the classical competitor (least squares method) in predicting the development of cyber epidemics near the extremum of the time series representing the deployment of such a process over time. Moreover, the proposed model can be applied without any prior hypotheses regarding the probabilistic properties of the available data.</p>
  a2001-037000511nas a2200157   4500000000100000000000100001008004100002260001200043100002200055700002200077700001900099700002200118245012300140856008300263490000700346       2024                            d  c10/20241 aViacheslav Kovtun1 aKrzysztof Grochla1 aElena Zaitseva1 aVitaly Levashenko00aThe concept of effective coverage radius use of the unlicensed high-frequency range in the operation of the 5G network  uhttps://www.sciencedirect.com/science/article/pii/S2405844024158562?via%3Dihub0 v1000442nas a2200145   4500000000100000000000100001008004100002100002200043700002100065700002200086700002200108245010000130856005900230490000700289       2024                            d1 aVolodymyr Dubovoi1 aMaria Yukhimchuk1 aViacheslav Kovtun1 aKrzysztof Grochla00aFunctional Dependability of Distributed Control of Multi-zone Objects under Failures Conditions  uhttps://ieeexplore.ieee.org/abstract/document/105776590 v1200468nas a2200157   4500000000100000000000100001008004100002260001200043100002200055700002200077700001900099700002200118245008500140856007800225490000700303       2024                            d  c04/20241 aViacheslav Kovtun1 aKrzysztof Grochla1 aElena Zaitseva1 aVitaly Levashenko00aThe concept of optimal planning of a linearly oriented segment of the 5G network  uhttps://journals.plos.org/plosone/article?id=10.1371/journal.pone.02990000 v1900382nas a2200109   4500000000100000000000100001008004100002100002200043700002200065245007900087856010600166       2024                            d1 aArtur Frankiewicz1 aKrzysztof Grochla00aOcena wydajności mechanizmu retransmisji TS011_1. 0.0 w sieciach LoRa WAN  uhttps://yadda.icm.edu.pl/baztech/element/bwmeta1.element.baztech-ca38f38f-5189-4f56-b397-df8beb30583801208nas a2200217   4500000000100000000000100001008004100002260003300043653000900076100002400085700002200109700001600131700001700147700001600164700001700180700001600197700001600213245007200229856005000301520063900351       2026                            d  c02/2026bIEEEaLas Vegas USA10aLoRa1 aTadeusz Czachórski1 aKrzysztof Grochla1 aPiotr Pecka1 aAnna Strzoda1 aJ. Fourneau1 aLynda Mokdad1 aMonika Nycz1 aTomasz Nycz00aThe impact of CSMA on LoRaWAN gateways' performance in IoT networks  uhttps://ieeexplore.ieee.org/document/113665363 a<p>The CSMA mode of operation was recently added to the LoRaWAN standard. We investigate, using a queueing model, how the introduction of CSMA in the communication between devices and the gate in LoRaWan may increase the probability of successful transmission. &nbsp;In the proposed model, customers (transmissions) are served by a multichannel station (gate), and the number of channels corresponds to the number of transmissions that can be performed in parallel. We introduce a queueing model with multiple attempts to find a free channel and investigate their impact on transmission throughput and reliability.<br />
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00455nas a2200157   4500000000100000000000100001008004100002260001200043100002200055700002100077700002200098700002200120245013400142490000700276022001400283       2025                            d  c01/20251 aVolodymyr Dubovoi1 aMaria Yukhimchuk1 aViacheslav Kovtun1 aKrzysztof Grochla00aModel-Oriented Training of Coordinators of the Decentralized Control System of Technological Facilities With Resource Interaction0 v13  a2169-353602162nas a2200193   4500000000100000000000100001008004100002260000900043100002200052700002200074700002300096700001800119700002100137245007700158856007200235490000700307520164000314022001401954       2025                            d  c20251 aViacheslav Kovtun1 aKrzysztof Grochla1 aMohammed Al-Maitah1 aSaad Aldosary1 aOleksii Kozachko00aEntropy-extreme concept of data gaps filling in a small-sized collection  uhttps://www.sciencedirect.com/science/article/pii/S11108665250001430 v293 a<p>Annotation The article investigates the process of filling data gaps in a small-sized collection, which generalizes information about periodic measurement of input and output parameters of a target object. To fill the data gaps, a concept is proposed based on generating a committee of entropy-optimal trajectories through sampling probability density functions of parameters from a stochastic parameterized model trained on relevant data. The concept is generalized to cases of filling gaps in output data, input data, and both those data spaces. Filling gaps in output data is implemented using entropy-extreme estimation of probability density functions for parameters of the model and errors of measurement. In the case of addressing missing values in input data, these are interpreted as results of transforming a sequence of independent stochastic vectors introduced into a model structurally identical to that formalized for filling gaps in output data. Thus, the proposed concept inherits the benefits of both parametric estimation and using a trained model of the target process and non-parametric estimation of undefined characteristics that distort data. The proposed concept was tested on the task of filling gaps in a collection consisting of 35 tuples with measurement results of three attributes. It was considered that the imperfection of the measurement procedure caused variability in the obtained data at the level of 15% of their absolute value. Less than 20% of the data from the collection was used to train the corresponding entropy-extreme model. The relative error of the filled missing data was 0.21.</p>
  a1110-866500712nas a2200253   4500000000100000000000100001000000100002008004100003260002500044100002000069700002600089700001900115700001400134700002300148700001800171700002200189700001800211700001800229700002000247245006300267856005500330300001200385490006100397       2025                            d  bIOS PressaAmsterdam1 aZachary Collier1 aRafael Muñoz-Carpena1 aMatthew Warren1 aAnca Rusu1 aOleksandr Chemerys1 aVadym Dodonov1 aKrzysztof Grochla1 aRobert Horton1 aGregory Kiker1 aGábor Komlósi00aUnderstanding Collapse and Recovery: Working Group Summary  uhttps://ebooks.iospress.nl/doi/10.3233/NICSP250012  a39–860 vVolume 67: Digital Technologies for Enhancing Resilience00394nas a2200145   4500000000100000000000100001008004100002260001200043100002200055700002400077700002000101700002100121700001900142245008700161       2025                            d  c04/20251 aKrzysztof Grochla1 aMichał Romaszewski1 aJarosław Sotor1 aPiotr Masłowski1 aBartosz Belter00aTowards AI-assisted Science with PLAI4SCIENCE - new Polish Research Infrastructure01709nas a2200145   4500000000100000000000100001008004100002260004700043100002200090700002200112245009600134856006700230520124400297020002201541       2026                            d  c01/2026bSpringer Nature SwitzerlandaCham1 aArtur Frankiewicz1 aKrzysztof Grochla00aUsing Time Series Analysis to Generate Synthetic Traffic Data for LoRa Network Simulation  uhttps://link.springer.com/chapter/10.1007/978-3-032-04197-5_163 a<p>Modelling radio signal attenuation in Low Power Wide Area Networks (LPWANs) is a complex challenge due to the numerous factors influencing signal propagation and attenuation. Recent advancements in artificial intelligence have enabled the use of neural network-based time series analysis to develop radio attenuation models suitable for radio simulators. In this paper, we evaluate the feasibility of such AI-driven models for discrete event simulations. To train and validate these models, we utilize data collected from a large-scale LoRaWAN network that has been operational for over six years. The trained model is then applied to generate synthetic data for radio network simulations. We compare the AI-generated data with conventional distribution-based generators, assessing their effectiveness in modelling real-world events and analysing the statistical distribution of the generated data. Finally, we discuss the benefits and limitations of using AI-based models for simulation purposes. While traditional generators typically produce data distributions that closely mirror real data, AI algorithms are more effective at capturing specific patterns found in actual datasets what is challenging with conventional methods.</p>
  a978-3-032-04197-500529nas a2200181   4500000000100000008004100001260002600042653004100068100002400109700002200133700001600155700001700171700001800188700001700206700001600223700001600239245009200255       2026                            d  bIEEEaAvignon, France10aDiffusion approximation; LPWAN; CSMA1 aTadeusz Czachórski1 aKrzysztof Grochla1 aPiotr Pecka1 aAnna Strzoda1 aJean Fourneau1 aLynda Mokdad1 aMonika Nycz1 aTomasz Nycz00aThe Impact of CSMA on LoRaWAN Communication Efficiency: A Diffusion Approximation Model