abstract: This dissertation introduces stochastic ordering of instantaneous channel powers of fading channels as a general method to compare the performance of a communication system over two different channels, even when a closed-form expression for the metric may not be available. Such a comparison is with respect to a variety of performance metrics such as error rates, outage probability and ergodic capacity, which share common mathematical properties such as monotonicity, convexity or complete monotonicity. Complete monotonicity of a metric, such as the symbol error rate, in conjunction with the stochastic Laplace transform order between two fading channels implies the ordering of the two channels with respect to the metric. While it has been established previously that certain modulation schemes have convex symbol error rates, there is no study of the complete monotonicity of the same, which helps in establishing stronger channel ordering results. Toward this goal, the current research proves for the first time, that all 1-dimensional and 2-dimensional modulations have completely monotone symbol error rates. Furthermore, it is shown that the frequently used parametric fading distributions for modeling line of sight exhibit a monotonicity in the line of sight parameter with respect to the Laplace transform order. While the Laplace transform order can also be used to order fading distributions based on the ergodic capacity, there exist several distributions which are not Laplace transform ordered, although they have ordered ergodic capacities. To address this gap, a new stochastic order called the ergodic capacity order has been proposed herein, which can be used to compare channels based on the ergodic capacity. Using stochastic orders, average performance of systems involving multiple random variables are compared over two different channels. These systems include diversity combining schemes, relay networks, and signal detection over fading channels with non-Gaussian additive noise. This research also addresses the problem of unifying fading distributions. This unification is based on infinite divisibility, which subsumes almost all known fading distributions, and provides simplified expressions for performance metrics, in addition to enabling stochastic ordering. / Dissertation/Thesis / Ph.D. Electrical Engineering 2014

Information security has been a very important issue in wireless networks. With the ever-increasing amount of data being exchanged over wireless networks, the confidentiality of information needs to be protected from unauthorized users called eavesdropper. Due to the broadcast nature of the wireless medium, the transmissions between legitimate users maybe overheard and intercepted by the unauthorized parties, which makes wireless transmission vulnerable to potential eavesdropping attacks. The security of wireless communications plays an increasingly important role in the cybercrime defense against unauthorized activities.     We consider the wireless physical layer security which has been explored for the sake of enhancing the protection of wireless communications against eavesdroppers. We consider the problem of secret communication through Rayleigh fading channel in the presence of an eavesdropper in which the transmitter knows the channel state information of both the main and eavesdropper channel. Then, we analyze the average capacity of the main channel and eavesdropper channel from which an expression of secrecy capacity is derived based on the cumulative distribution function and probability density function of the signal to noise ratio. We also analyze an expression for the symbol error rate of the main channel, and the outage probability is obtained for the main transmission. Finally, we perform the numerical results in MATLAB.

Abstract An inevitable trend in wireless communications is the requirement for higher and higher data rates. At the same time, location awareness requires high accuracy for positioning ability. One option fulfilling both of these challenges is the use of an ultra wideband (UWB) physical layer technology due to its extremely large inherent bandwidth. From the two possible solutions to generate UWB signals, this thesis is focused on the singleband approach. This technique is closer to the original idea of impulse radio transmission than the other recently proposed multiband UWB approach. This thesis focuses on UWB coexistence with several selected radio systems; global positioning and cellular systems, and wireless local area networks. The topic was studied analytically and with experimental tests. The analytical part is divided into simulations and theoretical calculations. In the study, two different physical layer concepts, several modulation schemes and pulse waveforms have been used to find the best system performance under interference. From time hopping and direct sequence based approaches (TH and DS, respectively), the latter with binary pulse amplitude modulation was seen to outperform the former one in an interfered multipath channel if compared with bit error rate performance. Therefore, the theoretical calculations are addressed to the DS-UWB approach. The formulation defined makes it possible to rather easily calculate the upper bound for DS-UWB system performance in an AWGN channel and the results can be used to calculate reference bounds, for example, in receiver algorithm studies. The experimental part of the work focused on link level coexistence measurements between UWB and either IEEE802.11b or 3G networks. UWB can cause harmful performance degradation on the victim system if there are unrealistic numbers of active interferers in close vicinity of the victim receiver. However, increasing the separation between the UWB interferer and victim to 40 cm, or 70 cm, in the case of WLAN and 3G, respectively, the impact is insignificant. It was also shown that the activity factor of the UWB transmitter has a great impact on the victim system's performance degradation. UWB activity factors of less than about 5% can be tolerated by the studied victim systems.

This thesis concisely describes essential type of modulation technique for transmission of binary signal. In introductory part there are summarized advantages and disadvantages for each described modulation technique. There are described proceeding of modulation and demodulation too. Next part is specialized mainly to determination of incorrect receiving probability. For each modulation technique are calculated theoretical values of bit error rate and compiled graph. In practical part there are described possibilities of Matlab platform for measurement of bit error rate. In implement Simulink there is built model of communication channel with additional AWGN channel. Graphs are constructed from simulation data by the help of model’s control script. On selected modulation technique are inspected various elements which are reacted with graph. In finale part there are compared theoretical and measured values and summarized analysis.

In todays society the amount of connected devices are increasing. Many of these devices are in need of an interface to enable interaction with users. These devices are built for solving tasks of varying degree of difficulty and the need for user-friendly interfaces are highly relevant. Errors is one attribute that needs to be considered when creating a user interface. Therefore, this thesis project investigates how one can design and evaluate a user interface, which is used in a flight test environment, with regards to usability in terms of low error rate. Based on requirements gathered in the requirements elicitation process together with inspiration from the anchor-based subgoaling design principle, a low-fidelity and a high-fidelity prototype is created. To evaluate these prototypes user testing together with the thinking aloud technique is used. Data regarding the number of errors made by each user, if they complete a task or not and the users general thoughts of the prototypes are also gathered. The whole process of implementation and evaluation is done in an iterative manner. The results show that the users are satisfied with the interface, complete or partially complete each task, make few errors and can recover from the mistakes they make. Based on the results, a conclusion from this thesis can be drawn that by using an iterative design, creating prototypes inspired by the anchor-based subgoaling design principle and conducting user tests together with the thinking aloud technique one can create and evaluate a user interface with regards to usability in terms of low error rate.

[pt] As distorções do sinal induzidas pela Dispersão dos Modos de Polarização (PMD) e pelas Perdas Dependentes da Polarização (PDL) em transmissões ópticas são discutidas no ponto de vista do comportamento estatístico das taxas de erro. Os efeitos isolados da PMD de primeira ordem e da PDL, juntamente com seus efeitos combinados em transmissões digitais foram avaliados através das medidas de penalidade de potência. É mostrado que em efeitos combinados, a PDL aumenta substancialmente as flutuações na BER, podendo este aumento ser maior que nos casos isolados de PMD e PDL. Os resultados obtidos indicam que o chirp da fonte tem um papel importante nos efeitos combinados. / [en] Signal distortion induced by Polarization Mode Dispersion and Polarization Dependent Losses in long-distance high-capacity optical transmissions is discussed from the viewpoint of the statistical behavior of the bit error rates. Pure first order PMD effects, pure PDL effects and combined PMD/PDL effects in digital transmissions were evaluated through power penalties measurements. It is show that PDL strongly enhances PMD effects and that the BER fluctuations may be much higher than those induced by pure PMD or pure PDL. The results obtained indicate that the chirp of the source plays an important role in the combined PMD-PDL effects. / [es] En este trabajo se discute, desde el punto de vista de comportamiento estadístico del error, las distorsiones de señales inducidas por la Dispersión de los Modos de Polarización (PMD) y por las Pérdidas Dependientes de la Polarización (PDL) en transmisiones ópticas. Los efectos alejados de la PMD de primer orden y de la PDL, conjuntamente con sus efectos combinados en transmisiones digitales fueron evaluados a través de las medidas de penalidad de potencia. Se muestra que en efectos combinados, la PDL aumenta substancialmente las flutuaciones en la BER, pudiendo este aumento ser mayor que en los casos isolados de PMD y PDL. Los resultados obtenidos indican que el chirp de la fuente tiene un papel importante en los efectos combinados.

One of the great aims of statistics, the science of collecting, analyzing, and interpreting data, is to protect against the probability of falsely rejecting an accepted claim, or hypothesis, given observed data stemming from some experiment. This is generally known as protecting against a Type I Error, or controlling the Type I Error rate. The extension of this protection against Type I Errors to the situation where thousands upon thousands of hypotheses are examined simultaneously is known as multiple hypothesis testing. This dissertation presents an improvement to an existing multiple hypothesis testing approach, the Focus Level method, specific to gene set testing (a branch of genomics) on Gene Ontology graphs. This improvement resolves a long standing computational difficulty of the Focus Level method, providing more than a 15.000-fold increase in computational efficiency. This dissertation also presents a solution to a multiple testing problem in genetics where a specific approach to mapping genes underlying quantitative traits of interest requires a multiplicity adjustment approach that both corrects for the number of tests while also ensuring logical consistency. The power advantage of the solution is demonstrated over the current standard approach to the problem. A side issue of this model framework led to the development of a new bivariate approach to quantitative trait marker detection, which is presented herein. The overall contribution of this dissertation to the statistics literature is that it provides novel solutions that meet real needs of practitioners in genetics and genomics with the aim of ensuring both that truth is discovered and that discoveries are actually true.

Multiple Input and Multiple Output (MIMO) is one of the techniques used tiimprove the system performance. In this thesis, we improve and evaluate the system performance of MIMO deploying MRT technique at the transmitter and MRCtechnique at the receiver with an assuming that the system can obtain perfect CSI.We derived expressions for outage probability and symbol error rate and simulationgraphs for SISO, SIMO, MISO, and MIMO in terms of outage probability. Our results show that the MIMO system performance is better than other configurations.We also observed that SISO have the least performance where SIMO and MISOhave same performance. The performance also increases as the number of antennasincrease in the system and it is suggested to use MIMO when performance is givehigh priority than cost.

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The current focus on the Internet of Things (IoT) has led to the emergence of many network scenarios with unlimited use cases, including smart homes, smart cities, smart agriculture, and more. Unmanned aerial vehicles (UAVs), also known as drones, have become increasingly popular due to their versatility and ability to collect and transmit data through various sensors and cameras. With real-time data transmission, autonomy, and cost-effectiveness, UAVs have become valuable tools for different applications, including disaster management, agriculture monitoring, and remote area control. Low-power wide-area network (LPWAN) technology plays a crucial role in enabling IoT, and LoRaWAN is one of the specific LPWAN communication technologies that can provide low power consumption and coverage over a wide range. During a catastrophe, wireless communication is critical for analyzing damaged regions, coordinating rescue and relief team actions, saving lives, and reducing economic losses. UAVs can partially replace damaged or overloaded wireless networks as an alternative wireless network provider. This thesis aimed to simulate a LoRa network and investigate the relationship between the UAV coverage radius and elevation angle, as well as the effect of multipath distortion and signal attenuation on UAV and user distance. By calculating signal-to-noise ratio (SNR) and bit error rate (BER) for LoRa in a line-of-sight (LoS) and non-line-of-sight (NLoS) environment, we provided a comprehensive analysis of LoRaWAN performance in real-life environments for long distances. The results indicate that LoRaWAN communication is reliable in various environments, making it a promising technology for emergency and medical communications. / Det nuvarande fokuset på Internet of Things (IoT) har lett till uppkomsten av många nätverksscenarier med obegränsade användningsfall, inklusive smarta hem, smarta städer, smart jordbruk och mer. Obemannade flygfarkoster (UAV), även kända som drönare, har blivit allt populärare på grund av deras mångsidighet och förmåga att samla in och överföra data genom olika sensorer och kameror. Med realtidsdataöverföring, autonomi och kostnadseffektivitet har UAVs blivit värdefulla verktyg för olika applikationer, inklusive katastrofhantering, jordbruksövervakning och fjärrkontroll av områden. Low-power wide-area network (LPWAN)-teknik spelar en avgörande roll för att möjliggöra IoT, och LoRaWAN är en av de specifika LPWAN-kommunikationsteknikerna som kan ge låg strömförbrukning och täckning över ett brett spektrum. Under en katastrof är trådlös kommunikation avgörande för att analysera skadade regioner, koordinera räddnings- och hjälpteams åtgärder, rädda liv och minska ekonomiska förluster. UAV:er kan delvis ersätta skadade eller överbelastade trådlösa nätverk som en alternativ leverantör av trådlöst nätverk. Detta examensarbete syftade till att simulera ett LoRa-nätverk och undersöka sambandet mellan UAV-täckningsradien och höjdvinkeln, såväl som effekten av flervägsdistorsion och signaldämpning på UAV och användaravstånd. Genom att beräkna signal-brusförhållande (SNR) och bitfelsfrekvens (BER) för LoRa i en siktlinje (LoS) och icke-siktlinje (NLoS) miljö, gav vi en omfattande analys av LoRaWAN prestanda i verkliga miljöer för långa avstånd. Resultaten indikerar att LoRaWAN-kommunikation är tillförlitlig i olika miljöer, vilket gör den till en lovande teknik för akut- och medicinsk kommunikation.