00637nas 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. a1424-822000473nas a2200157 4500000000100000000000100001008004100002260005000043100002100093700002100114700001600135700002000151700002100171245009800192020002500290 2013 d bOficyna Wydawnicza Politechniki Wrocławskiej1 aMichał Gorawski1 aLeszek Borzemski1 aAdam Grzech1 aJerzy Świątek1 aZofia Wilimowska00aIntelligent Information Systems, Knowledge Discovery, Big Data and High Performance Computing aISBN 978-83-7493-80000336nas a2200121 4500000000100000000000100001008004100002100002000043700002100063700002200084245009200106300001600198 2013 d1 aMarcin Gorawski1 aMichał Gorawski1 aStanisław Dyduch00aUse of grammars and machine learning in ETL systems that control load balancing process a1709–171401203nas 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.00344nas a2200121 4500000000100000000000100001008004100002100002000043700001500063700002100078245010900099300001400208 2013 d1 aMarcin Gorawski1 aDamian Lis1 aMichał Gorawski00aThe use of a Cloud Computing and the CUDA architecture in zero-latency Data Warehouses Computer Networks a312–32200331nas a2200121 4500000000100000000000100001008004100002100002000043700001700063700002100080245009400101300001400195 2013 d1 aMarcin Gorawski1 aPaweł Marks1 aMichał Gorawski00aModeling Data Stream Intensity in Distributed Stream Processing System, Computer Networks a372–38300557nas 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 a978-1-63190-079-200268nas 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 a88–11400379nas a2200145 4500000000100000000000100001008004100002260003800043100002000081700002300101700002100124700001800145245005800163300001200221 2015 d bSpringer International Publishing1 aMarcin Gorawski1 aMirosław Skrzewsk1 aMichał Gorawski1 aAnna Gorawska00aNeural networks in petrol station objects calibration a714-72301184nas 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

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.

 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 Networks00340nas a2200121 4500000000100000000000100001008004100002100002100043700002200064245011900086300000700205490000600212 2020 d1 aMichał Gorawski1 aKrzysztof Grochla00aPerformance Tests of Smart City IoT Data Repositories for Universal Linear Infrastructure Data and Graph Databases a310 v101290nas a2200133 4500000000100000000000100001008004100002260003500043100002100078700002200099245007700121520093600198020002201134 2019 d c10.2019bIEEEaDublin, Ireland1 aMichał Gorawski1 aKrzysztof Grochla00a"Graph Representation of Linear Infrastructure in Smart City IoT Systems3 a

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.

 a978-1-7281-5763-401790nas 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

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

00923nas a2200133 4500000000100000000000100001000000100002008004100003100002100044245007700065300000900142490000700151520063100158 2017 d1 aMichał Gorawski00aLoad Balancing and Processing Data From Internet of Things Smart Devices a5-180 v383 a

The evolution of Internet of Things and Information and Communication Technology is determined by systems’ ability to efficiently store and process massive amount of data connected with rapid flow of information. The smart devices creating Internet of Things produce massive amount of data, and while smart devices are independent, data analyst needs an effective mechanism to collect all these data, aggregate them and analyse. In this paper author presents Distributed Spatio- Temporal Data Warehouse systems as a platform to collect and analyse Internet of Things data such as smart sensor data and mobility data

01648nas a2200133 4500000000100000000000100001008004100002260003300043100002100076700001800097245014200115856005000257520120700307 2023 d c03/2023bIEEEaHainan, China1 aMichał Gorawski1 aKonrad Połys00aLocalization of mobile nodes in graphs using the True-range multilateration with node sorting (TriSort) approach in an indoor environment uhttps://ieeexplore.ieee.org/document/100746423 a
Mobile device localization is still an actual research problem. In many cases, we have a lack in all the positions but there is enough data to calculate position with the use of the multilateration. Our research proves that the order in which we calculate the positions with multilateration matters. We consider a network with mobile and stationary devices which are represented in the form of a graph with calculated distances as edges. Our contribution to solving the problem of indoor localization is true-range multilateration with a node sorting approach (TriSort). We based our research on an existing problem of smartphone localization in an enclosed indoor space using the BLE connection. The proposed algorithm is evaluated in a simulator. The distances are calculated using the BLE signal level estimation. We use the Genetic Algorithm commonly used for such problems to assess our TriSort approach. We compare the results of both methods according to obtained errors and their processing times, showing that the proposed TriSort method provides a minimal decrease in accuracy compared to global optimization (below 14%), with almost four orders of magnitudes lower complexity.
02088nas a2200145 4500000000100000000000100001008004100002100002000043700002300063700001800086700002100104245009000125856007200215520165500287 2023 d1 aMarcin Gorawski1 aKrzysztof Pasterak1 aAnna Gorawska1 aMichał Gorawski00aThe stream data warehouse: Page replacement algorithms and quality of service metrics uhttps://www.sciencedirect.com/science/article/pii/S0167739X230000313 a

The stream data warehouse is an answer to the rapidly changing world of data analysis, which demands reliable and up-to-date results, obtained in a near real-time manner. Therefore it is a subject of recent research involving such areas as continuous updates and low-latency response, for example. In this paper, we study the stream adaptation of the OLAP cube and, in particular – its memory paging mechanism. It is driven by the page replacement algorithm, which manages the efficient data transfer and thus supplies users with constantly updatable data cubes. The following paper introduces an entirely novel approach to this topic. By perceiving the page replacement process as a multi-objective optimization problem, we propose three new algorithms that constantly analyze their varying environment and adapt to those changes by adjusting their behavior. Moreover, they consider user-provided constraints, which impose maximal values of specific parameters that cannot be exceeded. In addition to the page replacement algorithms, we propose two distinct quality of service metrics that measure the overall efficiency of data transfer inside the stream data warehouse. In order to verify and compare the new algorithms with their older counterparts, a series of experiments were conducted. Their results have confirmed that the proposed algorithms meet their requirements and visibly outperform the original solutions. The average wait time decreased between 25% and 66% (from 1.3x to 3.0x respectively, depending on the chosen algorithm), whereas the peak wait time decreased by approximately 99% (between 100x and 190x respectively).

01877nas 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

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.

01207nas 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

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.

00578nas a2200193 4500000000100000000000100001008004100002260001200043100002000055700002400075700002300099700002500122700002100147700001600168700001900184700001800203700002000221245014300241 2024 d c06/20241 aMichał Cholewa1 aMichał Romaszewski1 aPrzemysław Głomb1 aKatarzyna Kołodziej1 aMichał Gorawski1 aJakub Koral1 aWojciech Koral1 aAndrzej Madej1 aKryspin Musioł00a‘Just One More Sensor is Enough’ – Iterative Water Leak Localization with Physical Simulation and a Small Number of Pressure Sensors01016nas 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

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.

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