Yes / Computer simulation is a powerful and convenient tool for the design and performance evaluation of free-space optical (FSO) communication systems. In this article, we present two simulation frameworks that incorporate not only the effects of atmospheric turbulence but also the impact of the angular fluctuations of the transmitter and receiver in FSO systems. In the first framework, the waveform of the optical signal is calculated sequentially from the transmitter to the receiver. Thus, it takes very long to run the simulation numerous times to obtain the statistical performance of the system. This is because the vast majority of simulation time is spent on the split-step beam propagation. In the second framework, we propose to isolate the beam propagation through atmospheric channel from the other effects. We compare the two frameworks in terms of accuracy and simulation time. We show that the second framework reduces the simulation time by more than a factor of 10 without sacrificing the accuracy under various conditions. / 10.13039/501100003725-National Research Foundation of Korea HR&D Center Funded by the Ministry of Science and ICT (Grant Number: 2022M1A3C2069728)

Along with playing an ever-increasing role in the integration of other communication networks and expanding in application diversities, the current Internet suffers from serious overuse and congestion bottlenecks. Efficient congestion control is fundamental to ensure the Internet reliability, satisfy the specified Quality-of-Service (QoS) constraints and achieve desirable performance in response to varying application scenarios. Active Queue Management (AQM) is a promising scheme to support end-to-end Transmission Control Protocol (TCP) congestion control because it enables the sender to react appropriately to the real network situation. Analytical performance models are powerful tools which can be adopted to investigate optimal setting of AQM parameters. Among the existing research efforts in this field, however, there is a current lack of analytical models that can be viewed as a cost-effective performance evaluation tool for AQM in the presence of heterogeneous traffic, generated by various network applications. This thesis aims to provide a generic and extensible analytical framework for analyzing AQM congestion control for various traffic types, such as non-bursty Poisson and bursty Markov-Modulated Poisson Process (MMPP) traffic. Specifically, the Markov analytical models are developed for AQM congestion control scheme coupled with queue thresholds and then are adopted to derive expressions for important QoS metrics. The main contributions of this thesis are listed as follows: • Study the queueing systems for modeling AQM scheme subject to single-class and multiple-classes Poisson traffic, respectively. Analyze the effects of the varying threshold, mean traffic arrival rate, service rate and buffer capacity on the key performance metrics. • Propose an analytical model for AQM scheme with single class bursty traffic and investigate how burstiness and correlations affect the performance metrics. The analytical results reveal that high burstiness and correlation can result in significant degradation of AQM performance, such as increased queueing delay and packet loss probability, and reduced throughput and utlization. • Develop an analytical model for a single server queueing system with AQM in the presence of heterogeneous traffic and evaluate the aggregate and marginal performance subject to different threshold values, burstiness degree and correlation. • Conduct stochastic analysis of a single-server system with single-queue and multiple-queues, respectively, for AQM scheme in the presence of multiple priority traffic classes scheduled by the Priority Resume (PR) policy. • Carry out the performance comparison of AQM with PR and First-In First-Out (FIFO) scheme and compare the performance of AQM with single PR priority queue and multiple priority queues, respectively.

Disertační práce je zaměřena na metody a systémy pro měření vzdálenosti a lokalizaci RFID tagů pracujících v pásmu UHF. Úvod je věnován popisu současného stavu vědeckého poznání v oblasti RFID prostorové identifikace a stručnému shrnutí problematiky modelování a návrhu prototypů těchto systémů. Po specifikaci cílů disertace pokračuje práce popisem teorie modelování degenerovaného kanálu pro RFID komunikaci. Detailně jsou rozebrány metody měření vzdálenosti a odhadu směru příchodu signálu založené na zpracování fázové informace. Pro účely lokalizace je navrženo několik scénářů rozmístění antén. Modely degenerovaného kanálu jsou simulovány v systému MATLAB. Významná část této práce je věnována konceptu softwarově definovaného rádia (SDR) a specifikům jeho adaptace na UHF RFID, která využití běžných SDR systémů značně omezují. Diskutována je zejména problematika průniku nosné vysílače do přijímací cesty a požadavky na signál lokálního oscilátoru používaný pro směšování. Prezentovány jsou tři vyvinuté prototypy: experimentální dotazovač EXIN-1, měřicí systém založený na platformě Ettus USRP a anténní přepínací matice pro emulaci SIMO systému. Závěrečná část je zaměřena na testování a zhodnocení popisovaných lokalizačních technik, založených na měření komplexní přenosové funkce RFID kanálu. Popisuje úzkopásmové/širokopásmové měření vzdálenosti a metody odhadu směru signálu. Oba navržené scénáře rozmístění antén jsou v závěru ověřeny lokalizačním měřením v reálných podmínkách.

Along with playing an ever-increasing role in the integration of other communication networks and expanding in application diversities, the current Internet suffers from serious overuse and congestion bottlenecks. Efficient congestion control is fundamental to ensure the Internet reliability, satisfy the specified Quality-of-Service (QoS) constraints and achieve desirable performance in response to varying application scenarios. Active Queue Management (AQM) is a promising scheme to support end-to-end Transmission Control Protocol (TCP) congestion control because it enables the sender to react appropriately to the real network situation. Analytical performance models are powerful tools which can be adopted to investigate optimal setting of AQM parameters. Among the existing research efforts in this field, however, there is a current lack of analytical models that can be viewed as a cost-effective performance evaluation tool for AQM in the presence of heterogeneous traffic, generated by various network applications. This thesis aims to provide a generic and extensible analytical framework for analyzing AQM congestion control for various traffic types, such as non-bursty Poisson and bursty Markov-Modulated Poisson Process (MMPP) traffic. Specifically, the Markov analytical models are developed for AQM congestion control scheme coupled with queue thresholds and then are adopted to derive expressions for important QoS metrics. The main contributions of this thesis are listed as follows: iii ¿ Study the queueing systems for modeling AQM scheme subject to single-class and multiple-classes Poisson traffic, respectively. Analyze the effects of the varying threshold, mean traffic arrival rate, service rate and buffer capacity on the key performance metrics. ¿ Propose an analytical model for AQM scheme with single class bursty traffic and investigate how burstiness and correlations affect the performance metrics. The analytical results reveal that high burstiness and correlation can result in significant degradation of AQM performance, such as increased queueing delay and packet loss probability, and reduced throughput and utlization. ¿ Develop an analytical model for a single server queueing system with AQM in the presence of heterogeneous traffic and evaluate the aggregate and marginal performance subject to different threshold values, burstiness degree and correlation. ¿ Conduct stochastic analysis of a single-server system with single-queue and multiple-queues, respectively, for AQM scheme in the presence of multiple priority traffic classes scheduled by the Priority Resume (PR) policy. ¿ Carry out the performance comparison of AQM with PR and First-In First-Out (FIFO) scheme and compare the performance of AQM with single PR priority queue and multiple priority queues, respectively.

The objective of this work is to enhance the awareness of the indoor propagation behaviour, by a set of investigations including simulations and measurements. These investigations include indoor propagation behaviour, local mean power estimation, proposing new indoor path loss model and introducing a case study on 60 GHz propagation in indoor environments using ray tracing and measurements. A summary of propagation mechanisms and manifestations in the indoor environment is presented. This comprises the indoor localization techniques using channel parameters in terms of angle of arrival (AOA), time of arrival (TOA) and received signal strength (RSS). Different models of path loss, shadowing and fast fading mechanisms are explored. The concept of MIMO channels is studied using many types of deterministic channel modelling such as Finite Difference Time Domain, Ray tracing and Dominant path model. A comprehensive study on estimating local average of the received signal strength (RSS) for indoor multipath propagation is conducted. The effect of the required number of the RSS data and their Euclidian distances between the neighbours samples are investigated over 1D, 2D and 3D configurations. It was found that the effect of fast fading was reduced sufficiently using 2D horizontal’s arrangement with larger spacing configuration. A modified indoor path loss prediction model is presented namely effective wall loss model (EWLM). The modified model with wall correction factors is compared to other indoor path loss prediction models using simulation data (for 2.4, 5, 28, 60 and 73.5 GHz) and real-time measurements (for 2.4 and 5 GHz). Different operating frequencies and antenna polarizations are considered to verify the observations. In the simulation part, EWLM shows the best performance among other models. Similar observations were recorded from the experimental results. Finally, a detailed study on indoor propagation environment at 60 GHz is conducted. The study is supported by Line of Sight (LoS) and Non-LoS measurements data. The results were compared to the simulated ones using Wireless-InSite ray tracing software. Several experiments have confirmed the reliability of the modelling process based on adjusted material properties values from measurements.

No description available.

The door lock - a key function in every modern home, as well as a product which is today undergoing drastic change. The digital revolution has not left the door lock untouched, and there is today a wide variety of digital door locks utilizing technologies ranging from touch displays to fingerprint readers. The premises of the project was to try a different approach to the digital door lock and implement it schoolyard-style using a secret knock sequence, set by the user. The secret sequence would consist of two elements, both a rhythmical and a positional pattern. To unlock the door, the user would therefore need to simultaneously knock the correct rhythm and knock at the correct positions. To record and analyze the knock vibrations, piezo electric sensors connected to an Arduino Uno were used. To unlock the door, a small servo motor, two gears and a timing belt were used to turn the lock turning knob . Despite a short time frame and hardships due to the limitations caused by the coronavirus outbreak, a fully functional prototype which fulfilled both reliability and consistency was achieved. It could with good consistency recognize the test sequence, which was the intro rhythm to ”We Will Rock You” knocked in a square pattern. But even with flawless functionality, the conclusion would have been the same. The security of the system may be exceptional from a technical perspective, but it falls flat when the human factor is taken into account. The ability for a potential burglar to simply watch as one executes the secret knock is too much of a security hazard for the system to ever be considered as a competitor to other alternatives. The usage of the system is therefore better suited for applications where the thrill of using the product is more important than the actual security of it. / Dörrlåset - en grundläggande funktion i varje modernt hem, och samtidigt en produkt som idag genomgår drastisk förändring. Som resultat av den digitala revolutionen finns det idag en uppsjö av olika digitala dörrlås som utnyttjar allt från touchskärmar till fingeravtrycksläsare. Syftet med projektet var att testa en annorlunda tappning på det digitala dörrlåset, och förverkliga något många hade drömt om i barndomen - ett dörrlås aktiverat genom ett eget hemligt knackningsmönster. Det hemliga knackningsmönstret skulle då bestå av både ett rytmiskt och ett positionellt mönster. Därmed skulle den som ville öppna dörren behöva knacka både rätt rytm, och på rätt ställen på dörren. För att spela in och analysera vibrationerna från knackningarna användes piezoelektriska sensorer kopplade till en Arduino Uno. Mekanismen som styrde själva upplåsningen bestod av en liten servomotor, två kugghjul och en kuggrem som kopplade samman det hela. Trots en begränsad tidsram och motgångar orsakade av coronaviruset lyckades en fullt fungerande prototyp med hög pålitlighet färdigställas. Den kunde med hög tillförlitlighet känns igen testsekvensen, som var introrytmen till ”We Will Rock You” knackat i mönstret av en kvadrat. Men även med felfri prestanda hade slutsatsen varit densamma. Säkerheten för systemet må vara exeptionell ur ett rent tekniskt perspektiv, men den faller platt när den mänskliga faktorn tas med i beräkningen. Risken att en potentiell inbrottstjuv helt enkelt tittar på när någon knackar det hemliga mönstret är för stor för att systemet någonsin skulle kunna betraktas som en seriös konkurrent till andra digitala dörrlås. Produkten är därmed bäst lämpad för användningsområden där nöjet av att använda den är av högre prioritet än själva säkerheten.

Master of Science / Department of Industrial & Manufacturing Systems Engineering / Malgorzata J. Rys / Emergency department (ED) overcrowding is a nationwide problem affecting the safety and preparedness of our health care system. Many hospital EDs face significant short and intense surges in demand on a daily basis. However, the surge in demand during disaster event is not short and intense, but it is a sustained one. In order to meet this sudden surge as defined above, hospital EDs need to be more prepared and efficient to cater to increased volume of demand involving huge uncertainties. This thesis looks at the creation and use of discrete event simulation modeling using ARENA 10.0 software. In this thesis, an attempt is made to show how the different arrival patterns and time durations for which victims keep arriving affect the EDs ability to treat the patients. It is shown, how the model can be used to estimate additional resources that would be required to accommodate additional patients within the ED. Various shapes of arrival distributions were tested for different time durations. It was found that the arrival distribution with parameters (3, 4), (3, 3), (4, 2) and (2, 4) did not challenge the institutional capacity. In other words, the hospital was able to treat all the patients without compromising the quality of care up to 24 hours. However, distribution with parameter (3, 2), (2, 2), (3, 1), (1, 2), (2, 3), (2, 1), (1, 4), (1, 3), (1, 1) and (0.5, 2) did affect the system performance. Under these distributions, there was at least one patient who was either dead, LWBS or diverted. This indicates the immediacy with which victims arriving under these distributions overwhelmed the limited resources Our aim was to study, how many more resources would the ED need in order to have zero critical expire, zero Left without Being Seen (LWBS) and zero patients diverted. Arrival distribution (1, 2) was randomly selected to study this objective and it was found that for a 24 hours of simulation run time, an additional of two full trauma resources were required in order to have zero critical expire in trauma rooms area and additional of five ED beds and three nurses were required in treatment area for patients with moderate severity to have zero LWBS. With these additional resources, the ED was also able to treat all the non disaster related patients thereby having zero patients diverted. The same procedure can be used to determine the number of additional resources ED would require to treat all the victims arriving with the rest of the arrival distribution for different time periods. The simulation model built would help the emergency planners to better allocate and utilize the limited ED resources in order to treat maximum possible patients. It also helps estimate the number of additional resources that would be required in a particular scenario.

Syfte - Syftet med detta examensarbete är att studera hur idag två helt skilda verksamheter; SAAB Training & Simulation och SAAB Avionics Systems, arbetar med spedition- och ankomstprocesser. Detta för att undersöka bakgrunden till vad som utformat processerna och för att säkerställa att dessa tillfredsställs då de tillsammans ska bedriva godsmottagning från och med 2017. I studien ingår även att ge förslag på hur godsmottagningen organisatoriskt ska bedrivas vid en integrerad struktur. Metod - En jämförelse av de båda företagens sätt att arbeta utförs genom en flödeskartläggning på vardera företag utifrån principerna för en fallstudie. För att möjliggöra kartläggningen och för att samla fakta har intervjuer genomförts löpande under studiens gång. En litteraturstudie har även genomförts för att kunna koppla verkligheten mot aktuella teorier och ge välgrundade förslag. Resultat - Studien mynnar ut i två processkartor. En för hur SAAB organisatoriskt ska bedriva godsmottagning direkt efter att SAAB Avionics flyttat sin verksamhet och en för hur godsmottagningen organisatoriskt ska bedrivas inom en femårsperiod. Till de båda processkartorna följer rekommendationer och konkreta åtgärdsförslag för hur detta ska gå till och vad som bör beaktas vid utformning av spedition- och ankomstprocesser mellan två företag. Implikationer - Eftersom resultatet är fördelat på två tidsperioder kan de förslag och resultat som avser den första tidsperioden betraktas som applicerbara, dessa resultat har fokuserats till att skapa ett funktionellt flöde. Medans de förslag och resultat som avser den andra tidsperioden kan ses som en förstudie för fortsatt forskning eller vidare fördjupning ifrån företagens sida. Begränsningar - Då en fullständig analys av hur den gemensamma godsmottagningen ska bedrivas är för omfattande, är denna studie begränsad till hur detta organisatoriskt ska bedrivas. Nyckelord - Godsmottagning, verksamhetsflytt, processkartläggning, spedition- och ankomst, kundkrav. / Purpose - The purpose of this thesis is to study how two separate operations; SAAB Training & Simulation and SAAB Avionics Systems, are managing forwarding and arrival processes. This in order to investigate the background of what have framed the processes and thereby enable them to corporate on a common goods reception starting 2017. Further, this study includes organizational suggestions on how the integrated goods reception should be managed. Method - A comparison between the two companies were made by conducting a process map on each of the operations. This approach was conducted in accordance with the principles of a case study. By continuously collecting data throughout in-depth interviews, a clear connection to the purpose was ensured. Further, a literature review was conducted in order to connect reality to current theories, and thereby present legitimate suggestions. Findings - This study propose two process maps. The first one focus on how SAAB should manage their goods reception from an organizational perspective, immediately after SAAB Avionics move their operations. Contrary to the first, the second process map aims to present a solution during a five year-period of time. Both maps include recommendations and concrete suggestions on how this should be done, as well as what companies should take into account when designing forwarding and arrival processes in general. Implications - Because of how the result is distributed between two time periods, the first time frame could only be regarded as applicable, as these are the results that have been used to create a functioning flow. The implications and results regarding the second time frame could thereby be seen as a pre-study, or suggestions for future research on the basis of the company’s own incentives. Delimitations - Due to the exhaustive character of conducting a full analysis of the common goods reception, this study is delimited to how this process should be managed from an organizational perspective. Key terms - Goods reception, moving of an operation, process mapping, forwarding and arrival processes, customer requirements.

Radar (RAdio Detection And Ranging) uses radio waves to detect the presence of a target and measure its position and other properties. This sensor has found many civilian and military applications due to advantages such as possible large surveillance areas and operation day and night and in all weather. The contributions of this thesis are within applied signal processing for radar in two somewhat separate research areas: 1) radar with array antennas and 2) radar with micro-Doppler measurements. Radar with array antennas: An array antenna consists of several small antennas in the same space as a single large antenna. Compared to a traditional single-antenna radar, an array antenna radar gives higher flexibility, higher capacity, several radar functions simultaneously and increased reliability, and makes new types of signal processing possible which give new functions and higher performance. The contributions on array antenna radar in this thesis are in three different problem areas. The first is High Resolution DOA (Direction Of Arrival) Estimation (HRDE) as applied to radar and using real measurement data. HRDE is useful in several applications, including radar applications, to give new functions and improve the performance. The second problem area is suppression of interference (clutter, direct path jamming and scattered jamming) which often is necessary in order to detect and localize the target. The thesis presents various results on interference signal properties, antenna geometry and subarray design, and on interference suppression methods. The third problem area is measurement techniques for which the thesis suggests two measurement designs, one for radar-like measurements and one for scattered signal measurements. Radar with micro-Doppler measurements: There is an increasing interest and need for safety, security and military surveillance at short distances. Tasks include detecting targets, such as humans, animals, cars, boats, small aircraft and consumer drones; classifying the target type and target activity; distinguishing between target individuals; and also predicting target intention. An approach is to employ micro-Doppler radar to perform these tasks. Micro-Doppler is created by the movement of internal parts of the target, like arms and legs of humans and animals, wheels of cars and rotors of drones. Using micro-Doppler, this thesis presents results on feature extraction for classification; on classification of targets types (humans, animals and man-made objects) and human gaits; and on information in micro-Doppler signatures for re-identification of the same human individual. It also demonstrates the ability to use different kinds of radars for micro-Doppler measurements. The main conclusion about micro-Doppler radar is that it should be possible to use for safety, security and military surveillance applications.