The aim of this project is to analyze a data log of wireless packet traffic, and to produce: (1) models for dynamic fluctuations in wireless channel and link quality, and, (2) a design for real-time communications over the given wireless channel. The models and designs are useful in setting up real-time communications in a vehicular test track (www.astazero.com). The data log came from experimental measurements at the test track. From this data, we fitted simple models for packet losses and retransmissions in the wireless communication system. These models took the form of a combination of a statistical model for the packet losses, with a deterministic model for retransmissions of lost packets. Such fitted models can be used to predict the average quality of vehicle position monitoring based on periodically transmitted position information. Such predictions help us decide the feasibility of safe and reliable conduct of testing with two or more moving test objects.

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Networked systems, such as telecom networks and cloud infrastructures, generate and hold vast amounts of conguration and operational data. The goal of this work is to make all this data available through a real-time search process named network search , which will enable new real-time management solutions. The thesis contains several contributions towards engineering a network search system. Key elements of our design are a weakly structured information model that includes spatial properties, a query language that supports location- and schema-oblivious search queries, a peer-to-peer architecture, a set of echo protocols for scalable query processing, and an indexing protocol for ecient routing for spatial queries. The data against which network search is performed is maintained in local real-time databases close to the data sources. The design follows a bottom-up approach in the sense that the topology for query routing is constructed from the underlying network topology. We have built a prototype of the system on a cloud testbed and developed applications that use network search functionality. Testbed measurements suggest that it is feasible to engineer a network search system that processes queries at low latency and low overhead and that can scale to 100'000 nodes. Simulation results for spatial queries show that query processing achieves response times and incurs overhead close to an optimal protocol, and that query result remains accurate under signicant churn. / <p>QC 20160411</p>

The wireless network at Björkskolan does not perform optimally where the major issues lies in the hardware used. This prevents the school from separating pupils from staff on different networks. The hardware features contribute to poorer performance on the wireless network. Because of the available hardware more than just the wireless network needs to be reviewed, thus the entire network needs an update. Various plans have been developed to meet the needs of the school, where the most advantageous plan is to acquire a new router and four new accesspoints that are placed over the premises to provide separation between the networks, which in turn provides increased security.

In recent years, the rapid growth in wireless data traffic has posed not only unique opportunities but also great challenges for the wireless industry. In order to meet the growing demand without excessive cost or energy consumption, one feasible option for the operators is to acquire more spectrum for wireless communication. Unlike the lengthy allocation process for exclusive spectrum licenses, secondary spectrum access is deemed as a flexible alternative to obtain additional spectrum at low cost. In particular, the VHF/UHF TV band, so called ’TV White Space’, is considered as the most promising candidate for secondary access thanks to its well defined primary usage and favorable propagation characteristic for building penetration and wide area coverage. Therefore, secondary access in the TV band has been extensively studied by both academic and industry. Most of the research have focused on the detection of ’spectrum holes’ with sensing technologies, while a few others have provided high level analysis of the potential of TV white space with simplistic secondary interference model for single secondary user. Only A limited number of studies have investigated aggregate interference from multiple secondary users, but even these studies have ignored the adjacent channel interference from secondary users close to the TV receivers. Thus, in this thesis we first concentrate on examining the effect of harmful interference on TV reception from short range devices transmitting on adjacent channels, and model the accumulative effect of multi-channel interferences observed in the measurement. Then the basic methodology for evaluating the potential of TV white space is developed in the second part of the thesis, where we propose a new analytical approach for regulating the secondary transmit power that significantly outperforms the existing method in the regulatory framework. Finally, we combine the aggregate interference model and the basic regulation methodology to extend the analysis from single user to multiple user case, first with only users transmitting on different adjacent TV channels and later also including users transmitting on co-channels. Our performance evaluation have shown that the effect of adjacent channel interference at close distance is far from negligible and the accumulative effect of multi-channel interferences has substantial impact on the scalability of a secondary system. In fact, the adjacent channel interference proves to be the primary limiting factor of the TV white space availability for low power short range systems. Nonetheless, because the proposed approach can adapt to varying environmental conditions and consequently utilize the spectrum reuse opportunity more efficiently than existing frameworks, we can still note considerable amount of TV white space available for short range secondary devices. / <p>QC 20121106</p> / QUASAR

Distributed control applications enabled by wireless networks are becoming more and more frequent. The advantages of wireless access are many, as control systems become mobile, autonomous and connected. Examples include platooning and automated factories. However, distributed control systems have stringent requirement on both reliability and timeliness, the latter in terms of deadlines. If the deadline is missed, the packet is considered useless, similarly to a lost or erroneous packet in a system without deadlines. In addition, wireless channels are, by nature, more exposed to noise and interference than their wired counterparts. Consequently, it implies a considerable challenge to fulfill the deadline requirements with sufficient reliability for proper functionality of distributed control applications. However, by taking advantage of cooperative communications, increased reliability can be achieved with little or no additional delay. Reducing the delay until a message is successfully received is a two-fold problem: providing channel access with a predictable maximum delay and maximizing the reliability of each transmission, once granted by the medium access method. To this end, this thesis proposes a framework that provides a bounded channel access delay and handles the co-existence of both time-triggered and event-driven messages encountered in distributed control applications. In addition, the thesis proposes and evaluates an efficient message dissemination technique based on relaying that maximizes the reliability given a certain deadline, or alternatively determines the delay required to achieve a certain reliability threshold for both unicast and broadcast scenarios. Numerical results, which are verified by Monte-Carlo simulations, show significant improvements with the proposed relaying scheme as compared to a conventional scheme without cooperation, providing more reliable message delivery given a fixed number of available time-slots. It also becomes clear in which situations relaying is preferable and in which situations pure retransmissions are preferable, as the relay selection algorithm will always pick the best option. The relay selection algorithm has a reasonable complexity and can be used by both routing algorithms and relaying scenarios in any time-critical application as long as it is used together with a framework that enables predictable channel access. In addition, it can be implemented on top of commercially available transceivers. / ACDC

Digital signage is an emerging new communication technology. It is expected to play an important role in today’s dynamic world as digital signage displays timely information, while reducing the environmental costs associated with traditional printed signage. The main focus of this thesis is the design, implementation, and evaluation of a digital signage system based on a PC to display web contents (or other dynamic information) on digital displays located at one or more locations. The system will display information based upon a “playlist” that can be dynamically updated. It avoids the single point of failure of a television (be it analog or IPTV) based system, since each display has an attached processor and local storage containing both the information to be displayed and the local playlist of what is to be displayed. Additionally, the design allows content to be customized to specific local viewers, i.e., the information displayed can be adapted to the user or users currently in front of the display. The granularity of the schedule (i.e., playlist) is much shorter than in existing digital signage systems – leading to a more visually dynamic experience for viewers. On the basis of our evaluation, we strongly believe that this approach to digital signage will displace existing signage systems. / Digital signage en framväxande ny kommunikationsteknik spelar en viktig roll idagens dynamiska värld. Digital signage visar värdefull och aktuell information förutbildning, näringslivsorganisationer och är viktigt för samhället, eftersom det ger både ettsätt att ge aktuell information och minska de miljömässiga kostnaderna i samband medtraditionella tryckta skyltar. Tyngdpunkten i denna avhandling är att designa, implementeraoch utvärdera en digital signage system baserat på en PC för att visa webb-innehåll (ellerannan dynamisk information) om digitala displayer som finns på en eller flera platser.Systemet kommer att generera värdefull dynamisk information i rätt tid till en grupp avolika tittare. Svarstiden för att visa innehållet på den digitala displayen är mycket snabbjämfört med andra skyltsystem. På grundval av vår utvärdering, tror vi starkt att den kanersätta det finns skyltsystem på marknaden.

Despite advancements in wireless communication worldwide, wireless underwater communication remains a significant challenge. The marine environment presents unique and challenging conditions for wireless communication, rendering radio waves unsuitable for long-distance underwater communication due to the water's absorption of electromagnetic waves. As a result, acoustic waves are often used for underwater communication as they can propagate over longer distances without being quickly attenuated as radio waves. This master's thesis investigates the use of a turbo equalizer, a digital signal processing method, to examine how well it can correct for disruptions and distortions that an acoustic signal encounters while traveling through water. The turbo equalizer aims to estimate and counteract the disturbances that affect the signal during transmission in the underwater environment. Hence enable the ability to reconstruct the original message with minimal bit errors, even in the presence of disturbances from the underwater environment and thereby enabling reliable communication. The outcome of this work was a functional system for transmitting and receiving underwater messages in a water tank. The decoded messages contained some bit errors, but it was demonstrated in hindsight that fault-free communication using the turbo equalization method was possible in some instances. This result indicates that turbo equalization can be applied to real-world applications to mitigate disturbances in wireless underwater communication.

Handheld computers are widely used, be it a mobile phone, personal digital assistant (PDA), or a media player. Although these devices are personal, often a small set of persons can use a given device, for example a group of friends or a family. The most natural way to communicate for most humans is through speech. Therefore a natural way for these devices to know who is using them is for the device to listen to the user’s speech, i.e., to recognize the speaker based upon their speech. This project exploits the microphone built into most of these devices and asks whether it is possible to develop an effective speaker recognition system which can operate within the limited resources of these devices (as compared to a desktop PC). The goal of this speaker recognition is to distinguish between the small set of people that could share a handheld device and those outside of this small set. Therefore the criteria is that the device should work for any of the members of this small set and not work for anyone outside of this small set. Furthermore, within this small set the device should recognize which specific person within this small group is using it. An application for a Windows Mobile PDA has been developed using C++. This application and its underlying theoretical concepts, as well as parts of the code and the results obtained (in terms of accuracy rate and performance) are presented in this thesis. The experiments conducted within this research indicate that it is feasible to recognize the user based upon their speech is within a small group and further more to identify which member of the group is the user. This has great potential for automatically configuring devices within a home or office environment for the specific user. Potentially all a user needs to do is speak within hearing range of the device to identify themselves to the device. The device in turn can configure itself for this user. / Handdatorer används mycket, det kan vara en mobiltelefon, handdator (PDA) eller en media spelare. Även om dessa enheter är personliga, kan en liten uppsättning med personer ofta använda en viss enhet, t.ex. en grupp av vänner eller en familj. Det mest naturliga sättet att kommunicera för de flesta människor är att tala. Därför ett naturligt sätt för dessa enheten att veta vem som använder dem är för enheten att lyssna på användarens röst, till exempel att erkänna talaren baserat på deras röst. Detta projekt utnyttjar mikrofonen inbyggd i de flesta av dessa enheter och frågar om det är möjligt att utveckla ett effektivt system högtalare erkännande som kan verka inom de begränsade resurserna av dessa enheter (jämfört med en stationär dator). Målet med denna högtalare erkännande är att skilja mellan den lilla set av människor som skulle kunna dela en handdator och de utanför detta lilla set. Därför kriterierna är att enheten bör arbeta för någon av medlemmarna i detta lilla set och inte fungerar för någon utanför detta lilla set. Övrigt inom denna lilla set, bör enheten erkänna som specifik person inom denna lilla grupp. En ansökan om emph Windows Mobile PDA har utvecklats med C++. Denna ansökan och det underliggande teoretiska begreppet, liksom delar av koden och uppnådda resultat (i form av noggrannhet hastighet och prestanda) presenteras i denna avhandling. Experimenten som utförs inom denna forskning visar att det är möjligt att känna användaren baserat på deras röst inom en liten grupp och ytterligare mer att identifiera vilken medlem i gruppen är användaren. Detta har stor potential för att automatiskt konfigurera enheter inom en hemifrån eller från kontoret till den specifika användaren. Potentiellt behöver en användare tala inom hörhåll för att identifiera sig till enheten. Enheten kan konfigurera själv för denna användare.

This document presents basic theory about how to setup a network solution fortransferring sensor data and also gives instructions on how to set up some of itsbuilding blocks. This document mainly handles LoRa, LoRaWAN, Chirpstack,Arduino and some other related frameworks. / Denna anvisning går igenom grundläggande teorier om hur man sätter upp ennätverkslösning för att kommunicera sensor data och ger även instruktioner förhur man sätter upp några av dessa enheter. Det här dokumentet handlar omLoRa, LoRAWAN, Chirpstack, Arduino och några andra relaterade ramverk. / <p>Högskoleingengör och/eller Teknisk Kanidat examen 16hp.</p>