Syftet med examensarbetet är att göra en trådlös version av det elektriska lås som tillverkas av Electec System AB.

För att göra ett trådlöst elektriskt lås måste ett batteri monteras i låset. Batteriet måste hållas uppladdat hela tiden för att kunna driva motorn och ge strömförsörjning till elektroniken i låset. Alla signaler mellan låset och styrenheten ska dessutom överföras trådlöst istället för med kabel. Signalerna måste kodas innan sändning så att ingen obehörig kan läsa signalen och sedan öppna dörren.

Det svåraste i ett trådlöst elektriskt lås är att överföra effekt från dörrkarmen till låset eftersom utrymmet är begränsat och avståndet mellan låsblecket i karmen och låset i dörren kan uppgå till 10 mm. För att överföra effekt från dörrkarmen till låset konstruerades en transformator. Förlusterna i transformatorn ökar kraftigt då luftgapet ökas.

Det visar sig att motor och övriga kretsar kan drivas med ett avstånd mellan kärnorna på upp till 7 mm. Luftgapet kan sannolikt ökas när andra transformatorkärnor används. Dessa fanns dock inte tillgängliga under examensarbetets gång på grund av lång leveranstid. I jämförelse med överföring av effekt är problemet att koda och överföra signaler mellan styrenheten och låset enklare och kan lösas med hjälp av färdiga kretsar.

This thesis presents research on transport layer behavior in wireless networks. As the Internet is expanding its reach to include mobile devices, it has become apparent that some of the original design assumptions for the dominant transport protocol, TCP, are approaching their limits. A key feature of TCP is the congestion control algorithm, constructed with the assumption that packet loss is normally very low, and that packet loss therefore is a sign of network congestion. This holds true for wired networks, but for mobile wireless networks non-congestion related packet loss may appear. The varying signal power inherent with mobility and handover between base-stations are two example causes of such packet loss. This thesis provides an overview of the challenges for TCP in wireless networks together with a compilation of a number of suggested TCP optimizations for these environments. A TCP modification called TCP-L is proposed. It allows an application to increase its performance, in environments where residual bit errors normally give a degraded throughput, by making a reliability tradeoff. The performance of TCP-L is experimentally evaluated with an implementation in the Linux kernel. The transport layer performance in a 4G scenario is also experimentally investigated, focusing on the impact of the link layer design and its parameterization. Further, for emulation-based protocol evaluations, controlled packet loss and bit error generation is shown to be an important aspect.

This paper presents a technique to improve the performance of TCP and the utilization of wireless networks.Wireless links exhibit high rates of bit errors, compared to communication over wireline or fiber. Since TCP cannotseparate packet losses due to bit errors versus congestion,all losses are treated as signs of congestion and congestionavoidance is initiated. This paper explores the possibility of accepting TCP packets with an erroneous checksum, toimprove network performance for those applications that can tolerate bit errors. Since errors may be in the TCP header aswell as the payload, the possibility of recovering the headeris discussed. An algorithm for this recovery is also presented.Experiments with an implementation have been performed,which show that large improvements in throughput can beachieved, depending on link and error characteristics.

This paper presents a wireless link and networkemulator, based upon the "Wireless IP" 4G system proposalfrom Uppsala University and partners. In wireless fading down-links (base to terminals) link-level frames are scheduled andthe transmission is adapted on a fast time scale. With fastlink adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteractedat the physical and link layers. A purpose of the emulatoris to investigate the resulting interaction with transport layer protocols. The emulator is built on Internet technologies, andis installed as a gateway between communicating hosts. The paper gives an overview of the emulator design, and presentspreliminary experiments with three different TCP variants. The results illustrate the functionality of the emulator by showing theeffect of changing link layer parameters on the different TCP variants.

This paper presents a wireless link and network emulator,along with experiments and validation against the "Wireless IP" 4G system proposal from Uppsala University and partners. In wireless fading downlinks (base to terminals) link-level frames are scheduled and the transmission is adapted on a fast time scale. With fast link adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteracted at thephysical and link layers. The emulator has been used to experimentally investigate the resulting interaction between the transport layer and the link layer. The paper gives an overview of the emulator design, and presents experimental results with three different TCP variants in combination with various link layer characteristics.

Internet and mobile communications have had a profound effect on today’s society. New services are constantly being deployed, in which an increasing amount of personal data is being processed in return for personally tailored services. Further, the use of electronic surveillance is increasing. There is the risk that honest citizens will have their privacy invaded for “the greater good”. We argue that it is of uttermost importance to retain the individuals’ control over their personal spheres.

One approach for enhancing the users’ privacy is to deploy technical measures for safeguarding privacy, so-called Privacy-Enhancing Technologies (PETs). This thesis examines a set of PETs for enabling anonymous communication, so-called anonymous overlay networks,which eliminate the processing of personal data altogether by allowing the users act anonymously when communicating in a networked environment.

This thesis focuses mainly on mobile networks. These are of great interest because on the one hand they lay the groundwork for new innovative applications, but on the other hand they pose numerous novel challenges to privacy. This thesis describes the implementation

and performance evaluation of mCrowds – an anonymous overlay network for mobile Internet that enables anonymous browsing. It also describes the ongoing investigation on how to design anonymous overlay networks in order to make them suitable for mobile ad hoc

networks, a required building block for ambient intelligence.

The PRIME project develops privacy enhancing identity management systems that allow users in various application areas such as e-commerce to regain control over their personal spheres. This paper introduces the PRIME technical architecture that also includes special trust-enhancing mechanisms, and shows how PRIME technologies can enhance privacy and trust of e-shopping customers. It also discusses the socio-psychological factors and HCI aspects influencing the end user's trust in privacy enhancing identity management, and shows why HCI research, user studies, and socio-psychological research, are necessary efforts to accompany system design.

For this project I was planning to construct a clock that could be synchronized with an external source. The clock should be able to keep the time between synchronizations as these may be sparse. It also needed to be able to store the current time in a memory and keep a register of stored times. The current time and the register must be viewable by the user and the clock must also have the ability to count down the last five seconds prior to a minute selected by the user. I have performed this work at home with my own equipments.

As an external source for the synchronization I have chosen the DCF-77 clock signal broadcasted from Germany. To receive this signal I used a cheap AM receiver built specifically for this purpose. For the actual clock I used a PIC microcontroller which I programmed in C. The chip had all I needed including an oscillator and a RAM memory. I also connected a 3x16 character LCD display to the clock as well as 4 1-pole buttons for the user interface.

The program is built upon an interrupt routine that with help of an internal timer is set to execute once every hundreds of a second. During this interrupt routine all other functions are executed. These functions include a DCF decoder, an internal clock to keep the time, an LCD driver and a user interface.

I have managed to read the clock signal from the receiver but due to interferences from the computer I used to program the PIC chip, I have not been able to get any good reception close to the computer. Apart from this setback the clock works as it should and it meets all other criteria.

This bachelor’s report is based upon an assignment specified by the company IT Resource AB, located in Årjäng Värmland.

The goal of this bachelor’s project was to create an API to extend the functionality of PHP. The API shall simplify and make the work more efficient for IT Resource AB when developing web applications. The simplification and the increased efficiency that the API offers are the possibilities to reuse and easily add new functions to the API when needed.

The functionality that the API will offer is an enhanced capability to handle variables and strings generated from a web page written in PHP. The enhanced capability refers to the possibility to store variables and strings from a web page written in PHP.

The API created consists of 2 parts, a client and a server. The client in the client/server system is an external module which contains the functionality for the communication with both PHP and the server. This means that the client in the client/server system will act as an interface between PHP and the server.

The implementation of the API’s functionality is found in the server part of the client/server system. The functionality implemented in the server is the possibility to store variables and strings in the main memory.

The result of this project is an API that increases the functionality of PHP. The API can, when needed, be extended further, and IT Resource AB can benefit from using it when developing web applications that make use of PHP.

We present a prototype of the user interface of a transparency tool that displays an overview of a user's data disclosures to different online service providers and allows them to access data collected about them stored at the services' sides. We explore one particular type of visualization method consisting of tracing lines that connect a user's disclosed personal attributes to the service to which these attributes have been disclosed. We report on the ongoing iterative process of design of such visualization, the challenges encountered and the possibilities for future improvements.

Possible attacks on mobile smart devices demand higher security for applications handling payments or sensitive information. The introduction of a tamper-proof area on future generations of mobile devices, called Trusted Execution Environment (TEE), is being implemented. Before devices with embedded TEEs can be deployed to the public, investigations on usability aspects of Trusted User Interfaces (TUI) are needed. This article describes the process we have followed at gathering requirements, prototyping and testing suitable designs for TUIs in combination with a touch-screen biometric system. At the end, we present relevant findings of a pilot study that we have conducted using an Experience Sampling Method (ESM) as part of our ongoing work.

In the last decade, we have seen an explosive growth in the deployment of multimedia applications on the Internet. However, the transport service provided over the Internet is not always feasible for these applications, since the network was originally designed for other types of applications. One way to better accommodate the service requirements of some of these applications is to provide a partially reliable transport service. A partially reliable transport service does not insist on recovering all, but just some of the packet losses, thus providing a lower transport delay than a reliable transport service. The work in this thesis focuses on the design, implementation, and evaluation of a partially reliable transport protocol called PRTP. PRTP has been designed as an extension to TCP in order to show that such a service could be effectively integrated with current protocol standards. An important feature of PRTP is that all modifications for PRTP are restricted to the receiver side, which means that it could be very easily deployed. The thesis presents performance results from various experiments on a Linux implementation of PRTP. The results suggest that transfer times can be decreased significantly when using PRTP as opposed to TCP in networks in which packet loss occurs. Furthermore, the thesis includes a study that investigates how users perceive an application that is based on a partially reliable service. Specifically, how users select the trade-off between image quality and latency when they download Web pages is explored. The results indicate that many of the users in the study could accept less than perfect image quality

if the latency could be shortened.

The purpose of this chapter is to expose and explain some problems on conceptual modelling in multimedia databases. By way of introduction after a short orientation of the problem a description is made of the idea of conceptual modelling starting from the ISO report of van Griethuysen (1987) where some fundamental concepts and definitions is considered. A discussion is carried out considering the modelling techniques and their capability and/or limitations concerning modelling environments in order to create multimedia databases. The discussion indicates that the general concepts and definitions in conceptual modelling suggested in the ISO report comprises the foundation to analyse more complex information such as multimedia contexts. The paper also proposes that the interactivity, communication (especially the pragmatic and semantic layers of communication) and information of information are all key factors in the process of understanding how conceptual modelling can support multimedia databases

The best - or possibly only - way to model data bases is to use conceptual modelling. This is true for traditional data bases, but does it also apply to data bases where information from various data sources is stored? Is it reasonable to work with the concepts objects, variables and relations when modelling user views of images, sounds or video data, separately or in combination? Is it even possible to adopt a conceptual approach to experiences of pictures or pieces of music? What happens when we move outside the traditional application areas of the model? Does the method provide an opportunity to model more unstructured and complex information? This chapter conducts a line of reasoning about some consequences of using conceptual modelling in the design of multimedia data bases. This study is explorative and part of a research work

This graduation work was done as a assignment from Fiber Optic City company based in Hudiksvall Sweden. The base assignment was to create an automated payment system for a Hotspot network and a company web page. The hotspot system should work as a standalone service. The company has already a working free-of-charge service that is offered to its customers and is based on Public IP system.

The company webpage was done with the help of a development suite called Flex2 and the result was an Adobe Flash application. To increase webpage dynamics a second page was developed for the company to have the ability to change and configure the main company webpage. An authentication service was deployed to configuration page to increase its security. As an engine and a substitute for lack of functionality and security in Adobe Flash simplePHP web service was used to connect Flash with a PHP script on its server.

The payment system was developed with the help of PHP, MySQL and JavaScript. The system uses Paypal IPN service for money transaction and transaction validation

A standalone web server with Apache2, PHP 5.0 and MySQL was deployed to the hotspot system to reduce the need of having an authentication system on a commercial Internet based web hotel.

Syftet med den här C-uppsatsen är att skapa en användarmanual för ett system som används inom TeliaSonera. Bakgrunden till uppsatsen är att det saknas en bra och enkel dokumentation till systemet.

Användarmanualen får sin utformning genom interjuver med användare, systemförvaltare samt arbetsledare. De får bestämma hur den ska se ut och vad den skall innehålla. Tanken med detta är att få en så användarvänlig manual som möjligt. Den färdiga dokumentationen testas med hjälp av verkliga fall från den dagliga verksamheten och användarna kommer med förslag på eventuella förändringar.

Manualen är företagsintern och finns endast i den slutna uppsatsvarianten.

Voice over IP (VoIP) traffic in a multi-hop wireless mesh network (WMN) suffers from a large overhead due to mac/IP/UDP/RTP headers and time collisions. A consequence of the large overhead is that only a small number of concurrent VoIP calls can be supported in a WMN[17]. Hop-to-hop packet aggregation can reduce network overhead and increase the capacity. Packet aggregation is a concept which combines several small packets, destined to a common next-hop destination, to one large packet. The goal of this thesis was to implement packet aggregation on a Linux distribution and to increase the number of concurrent VoIP calls. We use as testbed a two-hop WMN with a fixed data rate of 2Mbit/s. Traffic was generated between nodes using MGEN[20] to simulate VoIP behavior. The results from the tests show that the number of supported concurrent flows in the testbed is increased by 135% compared to unaggregated traffic.

During the past few years Internet telephony has advanced rapidly, and as the technology has evolved, more and more have come to consider it an alternative to making phone calls through the telephone network. Besides being cheaper, Internet telephony also provides several revolutionary services. It is likely though that the telephone network will remain in use for several years to come, and it still offers by far the best stability and is accepted by most people. If the two networks are to coexist, with their respective users, it would be useful if they could be made to interact, so that users of one network can call users of the other, and vice versa. This can be done with a VoIP/PSTN gateway, which translates control information and voice traffic between the two networks.

Our dissertation is about the work we have performed for TietoEnator in Karlstad. The assignment was to develop a prototype of a VoIP/PSTN gateway. Initially the system was meant to support phone calls initiated either from an “ordinary” phone or from an IP telephone. Also the voice traffic was supposed to be translated with the use of appropriate hardware. To manage this we first needed to study all the relevant protocols for communication used in the telephone network and on the Internet, to get an idea of how these could be made to interact. We also had to learn existing systems, libraries and tools in order to see how we could create our own system. Due to a long learning period and technical problems in the beginning, and because the necessary hardware equipment for translation of voice traffic did not arrive in time, the assignment was limited to include only calls initiated from the ordinary phone to the IP telephone, without voice transmission. Never the less, the efforts have produced results, and our work is explained in detail in this dissertation.

IT ses idag som ett strategiskt verktyg med krav på uppnådd lönsamhet i alla IT-relaterade investeringar och projekt. Lönsamhet och kostnadseffektivitet är tillsammans med nya lagar och förordningar för bolagsstyrning viktiga faktorer som fordrar bättre IT-styrning. Att bedöma och värdera affärsnytta och nyttoeffekter av IT innebär att se vad IT’s egentliga värde är för verksamheten och dess affärsprocesser. Genom att använda någon av de nyare metoderna för nyttobedömning som också har fokus på oväntade och dolda kostnader men framför allt inkluderar skattning av snabba/långsamma nyttor och direkta/indirekta nyttor, så uppnår man bättre kontroll över verksamheten och att man fokuserar på rätt saker och gör dem på rätt sätt. Alla dessa delar inkluderas i fenomenet IT-styrning med vilket man har som övergripande mål att på olika sätt få ett bättre stöd till affärsverksamheten av IT. IT-styrning kan idag avsevärt underlättas genom användning av standardiserade ramverk som t ex ITIL och/eller COBIT. Dessa ramverk inkluderar metodik, anvisningar och processer baserade på ”best practices”. Undersökningen har visat att de medverkande företagen, åtminstone på IT-verksamhetsnivå, oftast anser att IT är en strategisk lönsamhetsfaktor. Som ett bevis för detta använder man sig också av ovan beskrivna ramverk för IT-styrning. Dock kan inget av företagen egentligen peka på någon reell användning av de nyare metoderna för nyttobedömning. Undersökningen kan inte bevisa påståendet att företagsledningen inte i tillräckligt omfattande grad inser IT’s vikt för affärerna, men det finns indikationer som talar för ett visst ointresse för IT på ledningsnivå. IT-styrningen kan genom sitt affärsfokus dock komma att ändra på det.

This book contains a range of keynote papers and submitted papers presented at the 9th IFIP WG 9.2, 9.5, 9.6/11.7, 11.4, 11.6/SIG 9.2.2 International Summer School, held in Patras, Greece, in September 2014. The 9 revised full papers and 3 workshop papers included in this volume were carefully selected from a total of 29 submissions and were subject to a two-step review process. In addition, the volume contains 5 invited keynote papers. The regular papers are organized in topical sections on legal privacy aspects and technical concepts, privacy by design and privacy patterns and privacy technologies and protocols.

"We adopt component-based systems development" is a frequently used statement in the present IT-world, and there are many who demand their share of this recent trend in Internet commerce. Those with a judicious disposition may well wonder what a component actually is, and whats so good about it, but their musings will, all too often, be interrupted by a zealous vendor asserting that, without ActiveX and JavaBeans, you run a serious risk of going bankrupt within a year. The question is, what is the significance of the con¬cept "component-based systems development"? Is it becoming a watered down notion, just like "object-orientation" or "multimedia"? Indeed, many regard component-based systems development as the rescuer in their hour of need

Today, the most frequently used signaling system for telecommunication is called Signaling System No. 7 (SS7). The growing usage of mobile telephones and mobile data communica-tion, and the development of new services mean that the risk of intrusion and exploitation of the SS7 signaling networks increases. The increasing problem with unauthorized access to sensitive information and the operators’ growing demand for security is the origin of our work. This thesis presents a prototype design and implementation of a Security Gateway (SEG), which is a fundamental part of the TCAP user security (TCAPsec) concept. TCAPsec is a security concept for introducing security mechanisms to the signaling system. The proto-type includes three different protection modes that provide security services, ranging from almost no protection to full protection with the use of encryption algorithms. The thesis also contains an evaluation study of the delay penalties caused by the use of these security services. With regards to the restrictions on the prototype, the conclusion drawn from the evaluation results was that the protection mechanisms in the different protection modes did not inflict any significant time penalties. Instead, the results of the study indicate that the routing process of messages in the network is a more significant delaying part in the communication between different nodes. This result implies that the routing process takes longer time than the security services. The thesis also presents a number of discovered features that will require further investigation and development before the TCAPsec concept can be realized.

One of the ambitions when designing the Stream Control Transmission Protocol was to offer a robust transfer of traffic between hosts. For this reason SCTP was designed to support multihoming, which presumes the possibility to set up several paths between the same hosts in the same session. If the primary path between a source machine and a destination machine breaks down, the traffic may still be sent to the destination, by utilizing one of the alternate paths. The failover that occurs when changing path is to be transparent to the application.

This paper describes the results from experiments concerning SCTP failover performance, which means the time between occurrence of a break on the primary path until the traffic is run smoothly on the alternate path. The experiments are performed mainly to verify the Linux Kernel implementation of SCTP (LK-SCTP) and is run on the Emulab platform. The results will serve as a basis for further experiments.

The experiments are performed in a network without concurrent traffic and in conclusion the results from the experiments correspond well to the values found in other studies and they are close to the theoretical best values. As expected the parameter Path.Max.Retrans has a great impact on the failover time. One observation is that the failover time and the max transfer time for a message are dependent upon the status in the network when the break of the primary path occurs.

Cloud computing is becoming a key IT infrastructure technology being adopted progressively by companies and users. Still, there are issues and uncertainties surrounding its adoption, such as security and how users data is dealt with that require attention from developers, researchers, providers and users. The A4Cloud project tries to help solving the problem of accountability in the cloud by providing tools that support the process of achieving accountability. This paper presents the contents of the first A4Cloud tutorial. These contents include basic concepts and tools developed within the project. In particular, we will review how metrics can aid the accountability process and some of the tools that the A4Cloud project will produce such as the Data Track Tool (DTT) and the Cloud Offering Advisory Tool (COAT).

This paper elaborates HCI (Human-Computer Interaction) requirementsfor making cloud data protection tools comprehensible and trustworthy.The requirements and corresponding user interface design principles are derivedfrom our research and review work conducted to address in particular the followingHCI challenges: How can the users be guided to better comprehend theflow and traces of data on the Internet and in the cloud? How can individual endusers be supported to do better informed decisions on how their data can be usedby cloud providers or others? How can the legal privacy principle of transparencyand accountability be enforced by the user interfaces of cloud inspectiontools? How can the user interfaces help users to reassess their trust/distrust inservices? The research methods that we have used comprise stakeholderworkshops, focus groups, controlled experiments, usability tests as well as literatureand law reviews. The derived requirements and principles are groupedinto the following functional categories: (1) ex-ante transparency, (2) exercisingdata subject rights, (3) obtaining consent, (4) privacy preference management,(5) privacy policy management, (6) ex-post transparency, (7) audit configuration,(8) access control management, and (9) privacy risk assessment. This broadcategorization makes our results accessible and applicable for any developerwithin the field of usable privacy and transparency-enhancing technologies forcloud service chains.

The main purpose of this thesis is, on the behalf of ÅF, to examine how stored information can be gathered online in a timely fashion. Consideration must be taken to the server and network load. During our investigation we were able to optimize SQL queries that resulted in a reduction of the total execution time by 24 seconds at the server side. One analysis tool that was very useful during our assignment was QlikView, which turned out to be a database independent analysis and reporting tool. We have clarified some alternatives of the questions and answers by developing a graphical interface, which is the basis for putting together the information.

Our paper is about the work we performed for Prevas AB in Karlstad. The assignment was to synchronize three different systems calendar functions, so that what’s going into one calendar is visible in all the others. To manage this we needed first to survey how the three systems functioned, which split the work into an examination phase and a construction phase. The examination phase led to us limiting the work to only concern a one-way communication between two of the systems in the construction phase. This construction work is explained in detail in this paper.

Residual bit-errors in wireless environments are well known to cause difficulties for congestion controlled protocols like TCP. In this study we focus on a receiver-based loss differentiation approach to mitigating the problems, and more specifically on two different loss notification schemes. The fully receiver-based 3-dupack scheme uses additional dupacks to implicitly influence the retransmission behavior of the sender. The second TCP option scheme uses a TCP option to explicitly convey a corruption notification. Although these schemes look relatively simple at first glance, when examining the details several issues exist which are highlighted and discussed. A performance evaluation based on a FreeBSD kernel implementation show that the TCP option scheme works well in all tested cases and provides a considerable throughput improvement. The 3-dupack scheme also provide performance gains in most cases, but the improvements varies more between different test cases, with some cases showing no improvement over regular TCP.

The stability and performance of the Internet to date have in a large part been due tothe congestion control mechanism employed by TCP. However, while the TCP congestioncontrol is appropriate for traditional applications such as bulk data transfer, it hasbeen found less than ideal for multimedia applications. In particular, audio and videostreaming applications have difficulties managing the rate halving performed by TCP inresponse to congestion. To this end, the majority of multimedia applications use eithera congestion control scheme which reacts less drastic to congestion and therefore oftenis more aggressive than TCP, or, worse yet, no congestion control whatsoever. Sincethe Internet community strongly fears that a rapid deployment of multimedia applicationswhich do not behave in a fair and TCP-friendly manner could endanger the currentstability and performance of the Internet, a broad spectrum of TCP-friendly congestioncontrol schemes have been proposed. In this report, a survey over contemporary proposalsof TCP-friendly congestion control mechanisms for multimedia traffic in the Internetis presented. A classification scheme is outlined which shows how the majority of theproposed congestion control schemes emanate from a relatively small number of designprinciples. Furthermore, we illustrate how these design principles have been applied ina selection of congestion control scheme proposals and actual transport protocols.

The mismatch between the services offered by the two standard transport protocols inthe Internet, TCP and UDP, and the services required by distributed multimedia applicationshas led to the development of a large number of partially reliable transportprotocols. That is, protocols which in terms of reliability places themselves betweenTCP and UDP. This paper presents a taxonomy for retransmission based, partially reliabletransport protocols, i.e., the subclass of partially reliable transport protocols thatperforms error recovery through retransmissions. The taxonomy comprises two classificationschemes: one that classifies retransmission based, partially reliable transportprotocols with respect to the reliability service they offer and one that classifies themwith respect to their error control scheme. The objective of our taxonomy is fourfold:to introduce a unified terminology; to provide a framework in which retransmissionbased, partially reliable transport protocols can be examined, compared, and contrasted;to make explicit the error control schemes used by these protocols; and, finally, to gainnew insights into these protocols and thereby suggest avenues for future research. Basedon our taxonomy, a survey was made of existing retransmission based, partially reliabletransport protocols. The survey shows how protocols are categorized according to ourtaxonomy, and exemplifies the majority of reliability services and error control schemesdetailed in our taxonomy.

PRTP is proposed to address the need of a transport service that is more suitable forapplications with soft real-time requirements, e.g., video broadcasting. It is an extensionfor partial reliability to TCP. The main idea behind PRTP is to exploit the fact thatmany soft real-time applications tolerate a limited amount of packet loss. In particular,PRTP enables an application to trade some of the reliability offered by TCP for improvedthroughput and interarrival jitter. This paper describes the design of PRTP andgives a detailed description of a simulation based performance evaluation. The performanceevaluation involved the performance of PRTP compared to TCP in long- as wellas in short-lived connections and showed that PRTP probably would give significantimprovements in performance, both in terms of throughput and interarrival jitter, for awide range of applications. The performance evaluation also suggested that PRTP is notTCP-friendly and altogether fair against competing flows and thus is not suitable for usein an environment where the main reason for packet loss is congestion, e.g., in a fixedInternet environment. We believe, however, that PRTP could be a viable alternative forwireless applications in error prone environments.

An ignition system is needed to control an engine. This ignition system has to be able to provide the right energy at the right time. Due to the lack of efficiency in older mechanical and early electronic systems, we planned to design and construct a capacitive discharge ignition system. This system includes a microcontroller that will calculate the spark timing. The system controls the spark timing depending on the engine speed. The engine speed is measured using a sensor mounted near the engine flywheel. The basic idea is to split the system into three subsystems, the charge subsystem, the ignition subsystem and the controller. The first step was to design, simulate and construct each subsystem. The next step was to merge these subsystems into a working unit. The result was a fully functional capacitive ignition system.

The main result of this chapter is an integrated framework of enterprise modelling and its coherence analysis. In a coherence analysis we investigate the relationship between system communication flows and internal state changes. The framework focuses on the modelling of static and behavioural aspects, where several actors co-operate to achieve their goals. Integration of various dependencies lies in the foreground of the suggested enterprise modelling approach. In this approach, we can show how to bring together static and dynamic diagrams of processes and to combine insights from the point of view of different goals. The ultimate goal is to introduce new principles for integration of various approaches in information system analysis. These principles are useful to check coherence of semantic diagrams. The presented framework is illustrated by examples from a case study in the forest industry

The focus of this paper is on the modelling primitives which are not only taking into account semantic models of traditional approaches for information system development, but also put a communication aspect into the foreground of system analysis. Integration of static, dynamic and non-traditional communication dependencies is considered as a most important feature of the suggested framework. In this paper is presented an integrated set of the basic semantic modelling primitives that is adequate to analyse the static and dynamic aspects of business processes. It is useful for the purpose of understanding and reasoning about information systems at the enterprise modelling level