Probabilistic model checking is a technique employed for verifying the correctness of computer systems that exhibit probabilistic behaviour. A related technique is controller synthesis, which generates controllers that guarantee the correct behaviour of the system. Not all controllers can be generated offline, as the relevant information may only be available when the system is running, for example, the reliability of services may vary over time. In this thesis, we propose a framework based on controller synthesis for stochastic games at runtime. We model systems using stochastic two-player games parameterised with data obtained from monitoring of the running system. One player represents the controllable actions of the system, while the other player represents the hostile uncontrollable environment. The goal is to synthesize, for a given property specification, a controller for the first player that wins against all possible actions of the environment player. Initially, controller synthesis is invoked for the parameterised model and the resulting controller is applied to the running system. The process is repeated at runtime when changes in the monitored parameters are detected, whereby a new controller is generated and applied. To ensure the practicality of the framework, we focus on its three important aspects: performance, robustness, and scalability. We propose an incremental model construction technique to improve performance of runtime synthesis. In many cases, changes in monitored parameters are small and models built for consecutive parameter values are similar. We exploit this and incrementally build a model for the updated parameters reusing the previous model, effectively saving time. To address robustness, we develop a technique called permissive controller synthesis. Permissive controllers generalise the classical controllers by allowing the system to choose from a set of actions instead of just one. By using a permissive controller, a computer system can quickly adapt to a situation where an action becomes temporarily unavailable while still satisfying the property of interest. We tackle the scalability of controller synthesis with a learning-based approach. We develop a technique based on real-time dynamic programming which, by generating random trajectories through a model, synthesises an approximately optimal controller. We guide the generation using heuristics and can guarantee that, even in the cases where we only explore a small part of the model, we still obtain a correct controller. We develop a full implementation of these techniques and evaluate it on a large set of case studies from the PRISM benchmark suite, demonstrating significant performance gains in most cases. We also illustrate the working of the framework on a new case study of an open-source stock monitoring application.

It is widely acknowledged that enterprise resource planning (ERP) systems suffer from complex user interfaces. The complexity of these user interfaces negatively affects the usability of these systems. Current research has shown that a need exists to improve the overall usability of ERP systems. This research proposes the use of adaptive user interfaces (AUIs) as a means of improving the overall usability of ERP systems. Research has shown that AUIs are capable of improving system usability by reducing user interface complexity and improving the overall user experience. The primary objective of this research was to determine how AUIs could be designed to improve the usability of ERP systems. An adaptation taxonomy, ERP system architecture (incorporating an AUI), a set of AUI components and a set of usability heuristics for ERP systems were proposed to support the design, development and evaluation of AUIs for ERP systems. The proposed adaptation taxonomy provides support for three types of adaptation: content adaptation, presentation adaptation and navigation adaptation. The proposed ERP system architecture is a three-tiered system architecture, consisting of a Presentation Layer (incorporating an AUI), an Application Layer and a Database Layer. The proposed set of AUI components comprise a user model, a task model and a dialog model. The set of proposed usability heuristics aims to identify usability issues of ERP systems within the areas of Navigation, Presentation, Task Support, Learnability and Customisation. An AUI prototype was developed based on selected adaptive techniques from the proposed adaptation taxonomy and selected components from the proposed system architecture. All of the proposed AUI components were implemented. The AUI prototype was developed for an existing ERP system, namely SAP Business One (SBO). This prototype was designed, in order to resolve the usability issues of SBO identified through the use of the proposed set of heuristics. The development of the AUI prototype was made possible through the use of a software development kit (SDK) provided with SBO. The AUI prototype made use of content adaptation, presentation adaptation and navigation adaptation in order to address the identified usability issues. An empirical evaluation was conducted on the AUI prototype to determine whether it provided any usability benefits over the standard SBO system. The results from the empirical evaluation revealed that the AUI presented usability benefits with regard to learnability and satisfaction. Users who used the AUI prototype were able to learn how to use the ERP system a lot quicker and were more satisfied than users of the standard SBO system. The successful implementation of the AUI prototype provided practical evidence that the proposed adaptation taxonomy and the proposed system architecture can be implemented. This research has provided empirical evidence that the use of AUIs can improve the usability of ERP systems. Future research has outlined several possibilities to utilise and enhance the proposed adaptation taxonomy, the ERP system architecture and ERP heuristics, for the purpose of furthering research within the area of AUIs for ERP systems.

There has been little published about the characteristics of computer jobs running on modern time-sharing computer systems, due largely to the lack of appropriate programs and equipment necessary to measure the parameters involved. In this thesis, measures are presented for some of the important characteristics of jobs. The Data Collection Facility, which is part of the Michigan Terminal System, was used to this end. The Michigan Terminal System is a time-sharing operating system for the IBM 360/67 computer, and supports batch and terminal users simultaneously. Chapter 1 gives an outline of the problem, and other work which has been done in this line. It also contains a reasonably detailed description of the Michigan Terminal System. In Chapter 2, measurements of requested CPU service, CPU service obtained, system and user response times, I/O delays, and page waiting times are given. Chapter 3 outlines the storage requirements of jobs, and gives a model which will generate profiles of storage required by jobs over their running times, which are very similar to profiles observed for actual jobs. Some discussion of the results is given in chapter 4, and also a simple model of the system is shown which might be used in a simulation study employing measurements taken in this study. / Science, Faculty of / Computer Science, Department of / Graduate

Spread-spectrum multiple access (SSMA) is conceptually attractive for interactive data communications over broadcast channel shared by a large number of potential users. The present thesis Involves a study of asynchronous direct sequence SSMA interactive data communication systems. The study includes a unified analysis and assessment of system delay-throughput performance. Two important message delay components which are affected by the design of the transmitter/receiver pair result from code acquisition and bit-errors. A new code synchronizer design featuring a number of parallel correlators is developed, and an analysis of synchronizer performance as it relates to SSMA applications is provided. It is shown that average acquisition delay decreases in proportion to Increase In the number of correlators when this number is small. Receiver bit-error probability for any given channel occupancy is derived. Three protocols suitable for SSMA transmissions under different operating conditions are proposed. Using one of these protocols, the expected number of transmissions before a message is received error-free is estimated by averaging bit-error probabilities over a postulated channel occupancy probability distribution. This distribution is verified using data obtained from channel simulations. Delay-throughput characteristics of the SSMA system are thus obtained by evaluating the above delays and other exogenous delays at various traffic levels. Results relevant to the given system and traffic models, transmission protocol, and transmitter/receiver structure are obtained assuming that users' codes are uncorrelated. Subsequently, it is shown that the results are easily modified to account for code cross-correlations. Assessment of SSMA delay-throughput performance Is accomplished by comparisons with pure ALOHA, slotted ALOHA and queueing channels. These comparisons necessitate extension of existing analysis of slotted ALOHA channels to include the effects of Gaussian channel noise, as well as development of an analysis procedure for noisy pure ALOHA channels. It is shown that in power-limited situations, the capacities of ALOHA and queueing channels can be maximized with respect to the transmission bit rate. Delay-throughput comparisons show that at throughput levels much lower than the capacities of these channels, average delays for SSMA are higher than those of the other channels. However, capacities of SSMA channels are generally higher than those of the other channels, which occupy only a fraction of the available bandwidth at power levels favourable to SSMA. In such cases, the throughput which results for a given delay clearly favours SSMA. Comparisons are also performed with respect to m-parallel ALOHA or queueing channels, where ra is the number of channels accommodated by the available bandwidth. In this case the capacities of SSMA channels are generally less than those of m-parallel slotted ALOHA or queueing channels, but approximately equal to those of m-parallel pure ALOHA channels. Therefore, SSMA presents a viable alternative to m-parallel pure ALOHA multiple access for interactive data communications. SSMA is especially favourable for transmissions of long messages In a wide-band broadcast channel with limited power. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

In this thesis, the author pursued two objectives. The first objective was to present a working example of a convenient, "idiot-proof", interactive computer program (designed with the user - not the programmer - in mind). The second objective was to investigate how various types of users interact with the computer, with the intention of reaching some conclusions about which program interfaces were most appropriate and convenient for various user types. In addition, some theories about the effects of various behavioural variables were investigated. The experimental tool used for this research was a simple interactive computer game in which the participants searched for the optimum profit in a three-dimensional space, given a fixed time limit. , Frequent periodic measurements were automatically collected on user performance, attitude, requests for reports, utilization of special features, and other variables; also, the solution protocol of each participant was recorded. The users were cateqorized by coqnitive style (heuristic/analytic), risk attitude, and previous computer experience as determined by a battery of pre-tests and questionnaires. In analyzinq the results, it was found that experience level was the dcminatinq factor on all dimensions: novices were slower, finished less frequently, and were siqnificantly less confident than experienced players. A hiqhly structured proqram interface was found to be more appropriate for these new users., Experience was also the dominating factor in the use of reports, although novices did show a marked learning effect over time - as did all users on most dimensions of performance and behaviour. As previously hypothesized, analytic-types and risk-takers played significantly faster and were more confident than heuristic-types and risk-averters, respectively. Concerning utilization of special program features, it was found that input response defaults influenced users in unfamiliar situations (ones which were new or did not have clear-cut responses), and didn't affect them at all in familiar circumstances. Analytic-types made least use of defaults. Bisk-averters were least likely to abbreviate commands. Also, the extent to which commands were abbreviated depended much upon their length, Finally, in the area of solution protocols, it was indeed found that heuristic-types were much less structured in their approach to solving the problem than analytic-types. . / Business, Sauder School of / Graduate

Denna rapport presenterar ett projekt som syftar till att skapa en applikation med tillhörande hårdvara för att styra en vakuumpump i ett analyslaboratorie som ligger i anslutning till Bolidenägda Aitikgruvan i Gällivare. Vakuumpumpen används för att generera sugkraft till dragskåp, slangar och robotutrustning där giftiga ångor sugs bort när analyseringen av gråberg inträffar. Innan implementeringen av applikationen var pumphaverier ett faktum på grund av för lång tomgångskörning och Boliden beslutade därför att starta pump efter behov istället. Först skrevs en funktionsbeskrivning som vidare applicerades programmeringsmässigt i styrsystemet 800xA tillsammans med nödvändig hårdvara som exempelvis PAC, FRO och I/O-enheter. När applikationen innehöll samtliga funktioner testades den med en simulationscontroller som även kopplade samman applikation och konstruerad processbild. Efter felfri testkörning implementerades den essentiella hårdvaran för att genomföra ett slutgiltigt test på site med alla komponenter inkopplade. Detta test var framgångsrikt och en applikation enligt funktionsbeskrivning hade således konstruerats. Slutsatsen av arbetet är att det går att bygga en applikation för att styra en vakuumpump enligt kravspecifikationen med de applikationskomponenter som använts.

LoRaWAN är ett 4G liknande nätverk som används för en billig och energisnålnätverkslösning för Internet of Things produkter. I Skellefteå består det nuvarande nätverk avtre stycket Kerlink iBTS gateways som utgör hela Skellefteås LoRaWAN nät.Detta nätverk kräver omtanke och behöver uppdateras, då det i nuläget ej fungerar felfritt.Därför har jag under projektets gån uppdaterad felsökt och lagt fram uppdateringar pånätverket för dets framtid. Projektet innefattar att en gateway har uppdaterats men i sambandmed detta slutat att fungera. Problemet uppstod av en fel implementation med statiskaadresser på samtliga gateways istället för DHCP adresser som enligt protokoll ska användas.Nyaste uppdateringen stödjer därför inte längre statiska adresser och därför byttes den tillDHCP och slutade att fungera. Efter genomfört projekt fungerar nu LoRaWAN nätet bättresamt samtliga gateways är uppdaterade.

Replacing a data acquisition system (DAQ) is a substantial and long-term investment. Siemens Energy’s R&D department is considering a new DAQ system. The equipment should be relevant for at least ten years. The system performance needs to reflect today’s requirements but also consider those of the future. Together with measurement engineers at the company, a list of specifications is written, highlighting the DAQ system requirements. Also, two parallel use cases are defined. The general architecture of a data acquisition system is analyzed. Different implementation techniques are compared when navigating through the DAQ system design process. The comparison forms a relation between the architectural constraints and the requirements. Several tradeoffs in DAQ system design have been found and discussed. Furthermore, the review of market trends indicates the technical direction of modern DAQ systems Thus, questioning the current instrument/measurement strategy.

I Software defined networking (SDN) separeras kontrollplanet och dataplanet. Separationenintroducerar säkerhetsrisker, vilket öppnar dörren för olika attacktyper. Denial-of-Service (DoS) är enattacktyp som används för att belasta nätverksresurser, genom att skicka en stor mängd trafik tillnätverket. Det finns många olika metoder för att utföra DoS-attacker, vilket gör det svårt att stoppaattackerna. En DoS-attacktyp som kan vara kritisk mot SDN är SYN-flood. Den här typen av attackriktar sig mot Three-way handshake-processen, som uppstår när en klient vill ansluta mot en server.Avslutas inte processen på rätt sätt kan det missbruka serverns resurser, och påverkanätverkstillgängligheten. Det finns olika säkerhetslösningar som motarbetar SYN-flood-attacker. Deflesta säkerhetslösningarna faller inom kategorierna upptäcka och hantera. Säkerhetslösningar inomkategorin förhindra är relativt få i jämförelse med kategorierna upptäcka och hantera. Syftet med vårtarbete var att jämföra tre typer av SYN-flood-attacker, och undersöka säkerhetslösningar som förhindrarattacktypernas påverkan på SDN. De varianter vi jämförde var SYN-flood, ACK-flood och SYN-ACK-flood. Säkerhetslösningarna vi implementerade i vår studie var Rate-limit, CPU-limit och enkombination av båda. Genom en noggrant utformad fallstudie lyckades vi identifiera SYN-ACK-floodsom attacktypen med störst påverkan på SDN. Kombinationen av Rate-limit och CPU-limit varsäkerhetslösningen som var effektivast på att motarbeta attacktyperna. Vårt arbete bidrar till en ökadkunskap inom SDN-säkerhet.

This research report gives a general description of virtual memory systems. The mechanisms and policies and their effect on the operation and efficiency of virtual memory are explained. A virtual memory using a real time virtual address decoder, to decode a 32 bits of virtual address for the secondary memory to obtain the primary address location discussed. The decoder is developed with the use of associative or content-addressable memories. Replacement algorithms, used for selecting the pages of the main memory to be replaced, are described. The hardware implementation of the least recently used and least often used replacement policies using associative memories is presented.