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  • 101.
    Alexander, Karlsson
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Design and Development of a Wireless Multipoint E-stop System for Autonomous Haulers2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Safety-related functions are important in autonomous industrial applications and are featured in an extensive body of work contained within the standards. The implementation of safety-related systems is commonly done by an external company at a great cost and with limited flexibility. Thus, the objective of this thesis was to develop and implement a safety-related system using o-the-shelf products and to analyse how well it can comply with the established standards of safety-related functions. This work has sought to review the current standards for safety-functions, the eectsof harsh radio environments on safety-related systems, and how to validate the safety-function.The system development process was used to gain knowledge by rst building the concept based on pre-study. After the pre-study was nished, the process moved to the development of software, designed to maintain a wireless heartbeat as well as to prevent collisions between the autonomous and manual-driven vehicles at a quarry, and implementation of the system in real hardware. Finally, a set of software (simulations) and hardware (measurements in an open-pit mine) tests were performed to test the functionality of the system. The wireless tests showed that the system adhered to the functional requirements set by the company, however, the evaluated performance level according to ISO 13849-1 resulted in performance level B which is insucient for a safety-related function. This work demonstrates that it is not possible to develop a safety-related system using the off-the-shelf products chosen, without hardware redundancy.

  • 102.
    Alexandru, Iordan
    et al.
    Norwegian University of Science and Technology Trondheim.
    Podobas, Artur
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Programvaru- och datorsystem, SCS.
    Natvig, Lasse
    Norwegian University of Science and Technology Trondheim.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Programvaru- och datorsystem, SCS.
    Investigating the Potential of Energy-savings Using a Fine-grained Task Based Programming Model on Multi-cores2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we study the relation between energy-efficiencyand parallel executions when implemented with a fine-grained task-centricprogramming model. Using a simulation framework comprised of an ar-chitectural simulator and a power and area estimation tool, we haveinvestigated the potential energy-savings when employing parallelism onmulti-cores system. In our experiments with 2 - 8 multi-cores systems,we employed frequency and voltage scaling in order to keep the relativeperformance of the systems constant and measured the energy-efficiencyusing the Energy-delay-product. Also, we compared the energy consump-tion of the parallel execution against the serial one. Our results showthat through judicious choice of load balancing parameters, significantimprovements of around 200 % in energy consumption can be acheived.

  • 103.
    Alfredsson, Stefan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    A Case Study of Recent Mifare Classic Field Deployments From an (In-)Security Perspective2013Ingår i: Proceedings of the 21st International Conference on Software, Telecommunications and Computer Networks (SoftCOM 2013), Split, Croatia: FESB, University of Split , 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Mifare Classic is a very popular near-field communication technology that provides a shared-key, access-controlled, storage. Although the authentication protocol of Mifare Classic is compromised since half a decade, systems are still being deployed based on this technology, e.g. for access control systems and for public transport ticketing. By using commodity hardware, such as NFC enabled smartphones, by passing the security measures in some cases only require the installation and operation of a smartphone app. To this end, we present case studies of a number of recent Mifare Classic systems deployed during the last year, to serve as an illustration of practical security problems and to raise awareness thereof among NFC technology buyers and system implementors.

  • 104.
    Alfredsson, Stefan
    Karlstads universitet, Institutionen för informationsteknologi.
    TCP in Wireless Networks: Challenges, Optimizations and Evaluations2005Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    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.

  • 105.
    Alfredsson, Stefan
    et al.
    Karlstads universitet, Institutionen för informationsteknologi.
    Brunstrom, Anna
    Karlstads universitet, Institutionen för informationsteknologi.
    Bit Error Tolerant Multimedia Transport2004Ingår i: Perspectives on Multimedia: Communication, Media and Information Technology, Chichester: John Wiley & Sons, 2004, s. 175-191Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 106.
    Alfredsson, Stefan
    et al.
    Karlstads universitet, Institutionen för informationsteknologi.
    Brunstrom, Anna
    Karlstads universitet, Institutionen för informationsteknologi.
    TCP-L: Allowing Bit Errors in Wireless TCP2003Ingår i: Proceedings of the 12th IST Summit on Mobile and Wireless Communications: Enabling a Pervasive Wireless World / [ed] Atílio Gameiro, Institute for Operations Research and the Management Sciences (INFORMS), 2003, s. 149-154Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 107.
    Alfredsson, Stefan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Institutionen för informationsteknologi.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Institutionen för informationsteknologi.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    A 4G Link Level Emulator for Transport Protocol Evaluation2004Ingår i: Proceedings of The Second Swedish National Computer Networking Workshop (SNCNW), 2004, s. 19-23Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 108.
    Alfredsson, Stefan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Cross-layer analysis of TCP performance in a 4G system2007Ingår i: Proceedings of the 15th International Conference on Software, Telecommunications and Computer Networks, IEEE Computer Society, 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents results from an experimental study of TCP in a wireless 4G evaluation system. Test-bed results on transport layer performance are presented and analyzed in relation to several link layer aspects. The aspects investigated are the impact of channel prediction errors, channel scheduling, delay, and adaptive modulation switch level, on TCP performance. The paper contributes a cross-layer analysis of the interaction between symbol modulation levels, different scheduling strategies, channel prediction errors and the resulting frame retransmissions effect on TCP. The paper also shows that highly persistent ARQ with fast link retransmissions do not interact negatively with the TCP retransmission timer even for short round trip delays.

  • 109.
    Alfredsson, Stefan
    et al.
    Karlstads universitet, Institutionen för informationsteknologi. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Institutionen för informationsteknologi.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Emulation and Validation of a 4G System Proposal2005Ingår i: Proceedings of RadioVetenskap och Kommunikation 2005: Volume II, 2005, s. 357-362Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 110.
    Alfredsson, Stefan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Impact of 4G Wireless Link Configurations on VoIP Network Performance2008Ingår i: Proceedings of the 2008 IEEE International Symposium on Wireless Communication Systems, IEEE Communications Society, 2008, s. 708-712Konferensbidrag (Refereegranskat)
    Abstract [en]

    The performance of applications in wireless networks is partly dependent upon the link configuration. Link characteristics varies with frame retransmission persistency, link frame retransmission delay, adaptive modulation strategies, coding, and more. The link configuration and channel conditions can lead to packet loss, delay and delay variations, which impact different applications in different ways. A bulk transfer application may tolerate delays to a large extent, while packet loss is undesirable. On the other hand, real-time interactive applications are sensitive to delay and delay variations, but may tolerate packet loss to a certain extent. This paper contributes a study of the effect of link frame retransmission persistency and delay on packet loss and latency for real-time interactive applications. The results indicate that a reliable retransmission mechanism with fast link retransmissions in the range of 2-8 ms is sufficient to provide an upper delay bound of 50 ms over the wireless link, which is well within the delay budget of voice over IP applications.

  • 111.
    Alfredsson, Stefan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Transport Protocol Performance over 4G Links: Emulation Methodology and Results2006Ingår i: Proceedings of the International Symposium on Wireless Communication Systems (ISWCS), IEEE Computer Society, 2006, s. 327-332Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a wireless link and network emulator for 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 the physical and link layers. The emulator has been used to experimentally investigate the resulting interaction between the transport layer and the physical/link layer in such a downlink. The paper introduces the Wireless IP system, describes the emulator design and implementation, and presents experimental results with TCP in combination with various physical/link layer parameters. The impact of link layer ARQ persistency, adaptive modulation, prediction errors and simple scheduling are all considered.

  • 112.
    Alhowaidi, Mohammad
    Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Tekniska högskolan.
    Real-Time Systems with Radiation-Hardened Processors: A GPU-based Framework to Explore Tradeoffs2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Radiation-hardened processors are designed to be resilient against soft errorsbut such processors are slower than Commercial Off-The-Shelf (COTS)processors as well significantly costlier. In order to mitigate the high costs,software techniques such as task re-executions must be deployed together withadequately hardened processors to provide reliability. This leads to a huge designspace comprising of the hardening level of the processors and the numberof re-executions of each task in the system. Each configuration in this designspace represents a tradeoff between processor load, reliability and costs.

    The reliability comes at the price of higher costs due to higher levels of hardeningand performance degradation due to hardening or due to re-executions.Thus, the tradeoffs between performance, reliability and costs must be carefullystudied. Pertinent questions that arise in such a design scenario are — (i)how many times a task must be re-executed and (ii) what should be hardeninglevel? — such that the system reliability is satisfied.

    In order to evaluate such tradeoffs efficiently, in this thesis, we proposenovel framework that harnesses the computational power of Graphics ProcessingUnits (GPUs). Our framework is based on a system failure probabilityanalysis that connects the probability of failure of tasks to the overall systemreliability. Based on characteristics of this probabilistic analysis as well asreal-time deadlines, we derive bounds on the design space to prune infeasiblesolutions. Finally, we illustrate the benefits of our proposed framework withseveral experiments

  • 113.
    Alhuttaitawi, Saif
    Högskolan Kristianstad, Fakulteten för naturvetenskap.
    Storage System for Harvested Energy in IoT Sensors2018Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This work presents an energy system design for wireless sensor networks (WSNs) after applying our design the WSN should theoretically have an infinite lifetime. Energy harvesting sources can provide suitable energy for WSN nodes and reduce their dependence on battery. In this project, an efficient energy harvesting and storage system is proposed. By using (two supercapacitors and four DC/DC converters with step up /step down capabilities) all of them controlled by Microcontroller via switches to consider the best way to save energy to keep the WSN alive as long as possible. The usage of supercapacitors as an energy buffer to supply the sensor components (microcontroller and radio) with energy it needs to work. We could control the energy flow according to a specific voltage levels in supercapacitors to guaranty the full functionality for WSN with minimizing the loss of energy, and that’s leads to long time life for the wireless sensor node WSN. Another important thing we find in our experiment that is the inner leakage of the supercapacitor and how it has a critical effect on how long it can serve our system with energy. This paper contains on two theoretical sections (Part one and part two) which are based on literature reviews, and one experimental section (Part three) based on experimental building the prototype, coding and testing.

  • 114.
    Ali, Akhtar
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Dastgeer, Usman
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Kessler, Christoph
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    OpenCL for programming shared memory multicore CPUs2011Ingår i: Fourth Swedish Workshop on Multi-Core Computing MCC-2011: November 23-25, 2011, Linköping University, Linköping, Sweden / [ed] Christoph Kessler, Linköping: Linköping University , 2011, Vol. S. 65-70, s. 65-70Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In this work, we evaluate the effectiveness of OpenCL for programming multicore CPUs in a comparative case study with OpenMP and Intel TBB for five benchmark applications: matrix multiply, LU decomposition, 2D image convolution, Pi value approximation and image histogram generation.

  • 115.
    Ali, Majid
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Improving the Adaptive Context Views and Evaluate Real-Time Performance2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The versatility and dimension of smart phone applications is   increasing at magnificent rate and getting more and more advanced in a level that could solve complicated real time tasks. One of the important factors for such advancement has been the powerful sensors embedded on a Smartphone devices and sensory networks. Moreover, Context and Context-awareness would have remained a myth without the advent of sensors. The objective of this thesis has been to contribute to the research work carried out under the MediaSense project. Accordingly, the ultimate purpose of the thesis has been to evaluate and study the feasibility of the adaptive context view proposed in MediaSense Platform. In precise words, the thesis has done three core tasks. Firstly, the theoretical presentation of related works and the significance of the research question have been discussed through various social applications. Secondly, a proof-of-concept application has been developed to simulate what has been proposed in the research work. Finally, Android application has been designed and implemented in order to evaluate and study the techniques presented in a practical scenario. Moreover, in the android application known as SundsvallBIGBuddies, we have used the extensions designed for the existing MediaSense platform. The impact of using Android app relaying on a continuous stream of context data has been presented using graphs and tables.  In order to study the impact we used smart phone and tablets from Samsung.

  • 116.
    Ali, Mustafa
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Abid, Hussain
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Wireless and Industrial Network2013Självständigt arbete på grundnivå (kandidatexamen), 5 poäng / 7,5 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The purpose of this report is to implement the wireless network in a company withtwo different sites which is located in Riga and Malmo. The main task of this reportis to implement and configure wireless industrial network. This report is based oninformation we gathered from the ABC Company about their requirements for awireless network.Requirements of this ABC Company is focusing on their infrastructure planning,security and implementing them. Benefits and drawbacks of industrial wirelessnetwork will be described briefly in this report to get some idea how ABC Companywill face the problem when they will implement their wireless network.

  • 117.
    Ali, Nour
    et al.
    Brunel University, London, UK.
    Baker, Sean
    University of Limerick, Ireland.
    O'Crowley, Ross
    Red Orkid Limited, Dublin, Ireland.
    Herold, Sebastian
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Buckley, Jim
    University of Limerick, Ireland.
    Architecture consistency: State of the practice, challenges and requirements (vol 23, pg 224, 2018)2018Ingår i: Journal of Empirical Software Engineering, ISSN 1382-3256, E-ISSN 1573-7616, Vol. 23, nr 3, s. 1868-1869Artikel i tidskrift (Refereegranskat)
  • 118.
    Aliahmadipour, Laia
    et al.
    Department of Applied Mathematics, Faculty of Mathematics and Computer, Shahid Bahonar University of Kerman, Kerman, Iran.
    Torra, Vicenç
    Högskolan i Skövde, Institutionen för informationsteknologi. Högskolan i Skövde, Forskningscentrum för Informationsteknologi.
    Eslami, Esfandiar
    Department of Pure Mathematics, Faculty of Mathematics and Computer, Shahid Bahonar University of Kerman, Kerman, Iran.
    Eftekhari, Mahdi
    Department of Computer Engineering, Faculty of Engineering, Shahid Bahonar University of Kerman, Kerman, Iran.
    A definition for hesitant fuzzy partitions2016Ingår i: International Journal of Computational Intelligence Systems, ISSN 1875-6891, E-ISSN 1875-6883, Vol. 9, nr 3, s. 497-505Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we define hesitant fuzzy partitions (H-fuzzy partitions) to consider the results of standard fuzzy clustering family (e.g. fuzzy c-means and intuitionistic fuzzy c-means). We define a method to construct H-fuzzy partitions from a set of fuzzy clusters obtained from several executions of fuzzy clustering algorithms with various initialization of their parameters. Our purpose is to consider some local optimal solutions to find a global optimal solution also letting the user to consider various reliable membership values and cluster centers to evaluate her/his problem using different cluster validity indices.

  • 119.
    Ali-Eldin, Ahmed
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Capacity Scaling for Elastic Compute Clouds2013Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    AbstractCloud computing is a computing model that allows better management, higher utiliza-tion and reduced operating costs for datacenters while providing on demand resourceprovisioning for different customers. Data centers are often enormous in size andcomplexity. In order to fully realize the cloud computing model, efficient cloud man-agement software systems that can deal with the datacenter size and complexity needto be designed and built.This thesis studies automated cloud elasticity management, one of the main andcrucial datacenter management capabilities. Elasticity can be defined as the abilityof cloud infrastructures to rapidly change the amount of resources allocated to anapplication in the cloud according to its demand. This work introduces algorithms,techniques and tools that a cloud provider can use to automate dynamic resource pro-visioning allowing the provider to better manage the datacenter resources. We designtwo automated elasticity algorithms for cloud infrastructures that predict the futureload for an application running on the cloud. It is assumed that a request is either ser-viced or dropped after one time unit, that all requests are homogeneous and that it takesone time unit to add or remove resources. We discuss the different design approachesfor elasticity controllers and evaluate our algorithms using real workload traces. Wecompare the performance of our algorithms with a state-of-the-art controller. We ex-tend on the design of the best performing controller out of our two controllers anddrop the assumptions made during the first design. The controller is evaluated with aset of different real workloads.All controllers are designed using certain assumptions on the underlying systemmodel and operating conditions. This limits a controller’s performance if the modelor operating conditions change. With this as a starting point, we design a workloadanalysis and classification tool that assigns a workload to its most suitable elasticitycontroller out of a set of implemented controllers. The tool has two main components,an analyzer and a classifier. The analyzer analyzes a workload and feeds the analysisresults to the classifier. The classifier assigns a workload to the most suitable elasticitycontroller based on the workload characteristics and a set of predefined business levelobjectives. The tool is evaluated with a set of collected real workloads and a set ofgenerated synthetic workloads. Our evaluation results shows that the tool can help acloud provider to improve the QoS provided to the customers.

  • 120.
    Ali-Eldin, Ahmed
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    El-Ansary, Sameh
    Nile University.
    Optimizing Replica Placement in Peer-Assisted Cloud Stores2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Peer-assisted cloud storage systems use the unutilizedresources of the clients subscribed to a storage cloudto offload the servers of the cloud. The provider distributesdata replicas on the clients instead of replicating on the localinfrastructure. These replicas allow the provider to providea highly available, reliable and cheap service at a reducedcost. In this work we introduce NileStore, a protocol forreplication management in peer-assisted cloud storage. Theprotocol converts the replica placement problem into a lineartask assignment problem. We design five utility functionsto optimize placement taking into account the bandwidth,free storage and the size of data in need of replication oneach peer. The problem is solved using a suboptimal greedyoptimization algorithm. We show our simulation results usingthe different utilities under realistic network conditions. Ourresults show that using our approach offloads the cloud serversby about 90% compared to a random placement algorithmwhile consuming 98.5% less resources compared to a normalstorage cloud.

  • 121.
    Ali-Eldin, Ahmed
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    El-Ansary, Sameh
    Nile University.
    Replica Placement in Peer-Assisted Clouds: An Economic Approach2011Ingår i: Lecture Notes in Computer Science / [ed] Pascal Felber, Romain Rouvoy, Springer, 2011, s. 208-213Konferensbidrag (Refereegranskat)
    Abstract [en]

    We introduce NileStore, a replica placement algorithm based on an economical model for use in Peer-assisted cloud storage. The algorithm uses storage and bandwidth resources of peers to offload the cloud provider’s resources. We formulate the placement problem as a linear task assignment problem where the aim is to minimize time needed for file replicas to reach a certain desired threshold. Using simulation, We reduce the probability of a file being served from the provider’s servers by more than 97.5% under realistic network conditions.

  • 122.
    Ali-Eldin, Ahmed
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ilyushkin, Alexey
    Ghit, Bogdan
    Herbst, Nikolas Roman
    Papadopoulos, Alessandro
    Losup, Alexandru
    Which Cloud Auto-Scaler Should I Use for my Application?: Benchmarking Auto-Scaling Algorithms2016Ingår i: PROCEEDINGS OF THE 2016 ACM/SPEC INTERNATIONAL CONFERENCE ON PERFORMANCE ENGINEERING (ICPE'16), Association for Computing Machinery (ACM), 2016, s. 131-132Konferensbidrag (Refereegranskat)
  • 123.
    Ali-Eldin, Ahmed
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Kihl, Maria
    Lund University.
    Tordsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Analysis and characterization of a Video-on-Demand service workload2015Ingår i: Proceedings of the 6th ACM Multimedia Systems Conference, MMSys 2015, ACM Digital Library, 2015, s. 189-200Konferensbidrag (Refereegranskat)
    Abstract [en]

    Video-on-Demand (VoD) and video sharing services accountfor a large percentage of the total downstream Internet traf-fic. In order to provide a better understanding of the loadon these services, we analyze and model a workload tracefrom a VoD service provided by a major Swedish TV broad-caster. The trace contains over half a million requests gener-ated by more than 20000 unique users. Among other things,we study the request arrival rate, the inter-arrival time, thespikes in the workload, the video popularity distribution, thestreaming bit-rate distribution and the video duration distri-bution. Our results show that the user and the session ar-rival rates for the TV4 workload does not follow a Poissonprocess. The arrival rate distribution is modeled using a log-normal distribution while the inter-arrival time distributionis modeled using a stretched exponential distribution. Weobserve the “impatient user” behavior where users abandonstreaming sessions after minutes or even seconds of startingthem. Both very popular videos and non-popular videos areparticularly affected by impatient users. We investigate ifthis behavior is an invariant for VoD workloads.

  • 124.
    Ali-Eldin, Ahmed
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Rezaie, Ali
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Mehta, Amardeep
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Razroev, Stanislav
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Sjöstedt-de Luna, Sara
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Seleznjev, Oleg
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Tordsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    How will your workload look like in 6 years?: Analyzing Wikimedia's workload2014Ingår i: Proceedings of the 2014 IEEE International Conference on Cloud Engineering (IC2E 2014) / [ed] Lisa O’Conner, IEEE Computer Society, 2014, s. 349-354Konferensbidrag (Refereegranskat)
    Abstract [en]

    Accurate understanding of workloads is key to efficient cloud resource management as well as to the design of large-scale applications. We analyze and model the workload of Wikipedia, one of the world's largest web sites. With descriptive statistics, time-series analysis, and polynomial splines, we study the trend and seasonality of the workload, its evolution over the years, and also investigate patterns in page popularity. Our results indicate that the workload is highly predictable with a strong seasonality. Our short term prediction algorithm is able to predict the workload with a Mean Absolute Percentage Error of around 2%.

  • 125.
    Ali-Eldin, Ahmed
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Seleznjev, Oleg
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Sjöstedt-de Luna, Sara
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Tordsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Measuring cloud workload burstiness2014Ingår i: 2014 IEEE/ACM 7th International Conference on Utility and Cloud Computing (UCC), IEEE conference proceedings, 2014, s. 566-572Konferensbidrag (Refereegranskat)
    Abstract [en]

    Workload burstiness and spikes are among the main reasons for service disruptions and decrease in the Quality-of-Service (QoS) of online services. They are hurdles that complicate autonomic resource management of datacenters. In this paper, we review the state-of-the-art in online identification of workload spikes and quantifying burstiness. The applicability of some of the proposed techniques is examined for Cloud systems where various workloads are co-hosted on the same platform. We discuss Sample Entropy (SampEn), a measure used in biomedical signal analysis, as a potential measure for burstiness. A modification to the original measure is introduced to make it more suitable for Cloud workloads.

  • 126.
    Ali-Eldin, Ahmed
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Tordsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Kihl, Maria
    Lund University.
    WAC: A Workload analysis and classification tool for automatic selection of cloud auto-scaling methodsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Autoscaling algorithms for elastic cloud infrastructures dynami-cally change the amount of resources allocated to a service ac-cording to the current and predicted future load. Since there areno perfect predictors, no single elasticity algorithm is suitable foraccurate predictions of all workloads. To improve the quality ofworkload predictions and increase the Quality-of-Service (QoS)guarantees of a cloud service, multiple autoscalers suitable for dif-ferent workload classes need to be used. In this work, we intro-duce WAC, a Workload Analysis and Classification tool that as-signs workloads to the most suitable elasticity autoscaler out of aset of pre-deployed autoscalers. The workload assignment is basedon the workload characteristics and a set of user-defined Business-Level-Objectives (BLO). We describe the tool design and its maincomponents. We implement WAC and evaluate its precision us-ing various workloads, BLO combinations and state-of-the-art au-toscalers. Our experiments show that, when the classifier is tunedcarefully, WAC assigns between 87% and 98.3% of the workloadsto the most suitable elasticity autoscaler.

  • 127.
    Ali-Eldin, Ahmed
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Tordsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Kihl, Maria
    Department of Electrical and Information Technology, Lund University, Lund, Sweden.
    Workload Classification for Efficient Auto-Scaling of Cloud Resources2013Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Elasticity algorithms for cloud infrastructures dynamically change the amount of resources allocated to a running service according to the current and predicted future load. Since there is no perfect predictor, and since different applications’ workloads have different characteristics, no single elasticity algorithm is suitable for future predictions for all workloads. In this work, we introduceWAC, aWorkload Analysis and Classification tool that analyzes workloads and assigns them to the most suitable elasticity controllers based on the workloads’ characteristics and a set of business level objectives.

    WAC has two main components, the analyzer and the classifier. The analyzer analyzes workloads to extract some of the features used by the classifier, namely, workloads’ autocorrelations and sample entropies which measure the periodicity and the burstiness of the workloads respectively. These two features are used with the business level objectives by the clas-sifier as the features used to assign workloads to elasticity controllers. We start by analyzing 14 real workloads available from different applications. In addition, a set of 55 workloads is generated to test WAC on more workload configurations. We implement four state of the art elasticity algorithms. The controllers are the classes to which the classifier assigns workloads. We use a K nearest neighbors classifier and experiment with different workload combinations as training and test sets. Our experi-ments show that, when the classifier is tuned carefully, WAC correctly classifies between 92% and 98.3% of the workloads to the most suitable elasticity controller.

  • 128.
    Ali-Eldin Hassan, Ahmed
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Workload characterization, controller design and performance evaluation for cloud capacity autoscaling2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis studies cloud capacity auto-scaling, or how to provision and release re-sources to a service running in the cloud based on its actual demand using an auto-matic controller. As the performance of server systems depends on the system design,the system implementation, and the workloads the system is subjected to, we focuson these aspects with respect to designing auto-scaling algorithms. Towards this goal,we design and implement two auto-scaling algorithms for cloud infrastructures. Thealgorithms predict the future load for an application running in the cloud. We discussthe different approaches to designing an auto-scaler combining reactive and proactivecontrol methods, and to be able to handle long running requests, e.g., tasks runningfor longer than the actuation interval, in a cloud. We compare the performance ofour algorithms with state-of-the-art auto-scalers and evaluate the controllers’ perfor-mance with a set of workloads. As any controller is designed with an assumptionon the operating conditions and system dynamics, the performance of an auto-scalervaries with different workloads.In order to better understand the workload dynamics and evolution, we analyze a6-years long workload trace of the sixth most popular Internet website. In addition,we analyze a workload from one of the largest Video-on-Demand streaming servicesin Sweden. We discuss the popularity of objects served by the two services, the spikesin the two workloads, and the invariants in the workloads. We also introduce, a mea-sure for the disorder in a workload, i.e., the amount of burstiness. The measure isbased on Sample Entropy, an empirical statistic used in biomedical signal processingto characterize biomedical signals. The introduced measure can be used to charac-terize the workloads based on their burstiness profiles. We compare our introducedmeasure with the literature on quantifying burstiness in a server workload, and showthe advantages of our introduced measure.To better understand the tradeoffs between using different auto-scalers with differ-ent workloads, we design a framework to compare auto-scalers and give probabilisticguarantees on the performance in worst-case scenarios. Using different evaluation cri-teria and more than 700 workload traces, we compare six state-of-the-art auto-scalersthat we believe represent the development of the field in the past 8 years. Knowingthat the auto-scalers’ performance depends on the workloads, we design a workloadanalysis and classification tool that assigns a workload to its most suitable elasticitycontroller out of a set of implemented controllers. The tool has two main components;an analyzer, and a classifier. The analyzer analyzes a workload and feeds the analysisresults to the classifier. The classifier assigns a workload to the most suitable elasticitycontroller based on the workload characteristics and a set of predefined business levelobjectives. The tool is evaluated with a set of collected real workloads, and a set ofgenerated synthetic workloads. Our evaluation results shows that the tool can help acloud provider to improve the QoS provided to the customers.

  • 129.
    Alipour, Mehdi
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Carlson, Trevor E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    A Taxonomy of Out-of-Order Instruction Commit2017Ingår i: 2017 Ieee International Symposium On Performance Analysis Of Systems And Software (Ispass), Los Alamitos: IEEE Computer Society, 2017, s. 135-136Konferensbidrag (Refereegranskat)
    Abstract [en]

    While in-order instruction commit has its advantages, such as providing precise interrupts and avoiding complications with the memory consistency model, it requires the core to hold on to resources (reorder buffer entries, load/store queue entries, registers) until they are released in program order. In contrast, out-of-order commit releases resources much earlier, yielding improved performance without the need for additional hardware resources. In this paper, we revisit out-of-order commit from a different perspective, not by proposing another hardware technique, but by introducing a taxonomy and evaluating three different micro-architectures that have this technique enabled. We show how smaller processors can benefit from simple out-oforder commit strategies, but that larger, aggressive cores require more aggressive strategies to improve performance.

  • 130.
    Alirezaie, Marjan
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Kiselev, Andrey
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Längkvist, Martin
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Klügl, Franziska
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Loutfi, Amy
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    An Ontology-Based Reasoning Framework for Querying Satellite Images for Disaster Monitoring2017Ingår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 17, nr 11, artikel-id 2545Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a framework in which satellite images are classified and augmented with additional semantic information to enable queries about what can be found on the map at a particular location, but also about paths that can be taken. This is achieved by a reasoning framework based on qualitative spatial reasoning that is able to find answers to high level queries that may vary on the current situation. This framework called SemCityMap, provides the full pipeline from enriching the raw image data with rudimentary labels to the integration of a knowledge representation and reasoning methods to user interfaces for high level querying. To illustrate the utility of SemCityMap in a disaster scenario, we use an urban environment—central Stockholm—in combination with a flood simulation. We show that the system provides useful answers to high-level queries also with respect to the current flood status. Examples of such queries concern path planning for vehicles or retrieval of safe regions such as “find all regions close to schools and far from the flooded area”. The particular advantage of our approach lies in the fact that ontological information and reasoning is explicitly integrated so that queries can be formulated in a natural way using concepts on appropriate level of abstraction, including additional constraints.

  • 131.
    Alirezaie, Marjan
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Loutfi, Amy
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Towards Automatic Ontology Alignment for Enriching Sensor Data Analysis2013Ingår i: Communications in Computer and Information Science, ISSN 1865-0929, E-ISSN 1865-0937, Vol. 415, s. 179-193Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work ontology alignment is used to align an ontology comprising high level knowledge to a structure representing the results of low-level sensor data classification. To resolve inherent uncertainties from the data driven classifier, an ontology about application domain is aligned to the classifier output and the result is recommendation system able to suggest a course of action that will resolve the uncertainty. This work is instantiated in a medical application domain where signals from an electronic nose are classified into different bacteria types. In case of misclassifications resulting from the data driven classifier, the alignment to an ontology representing traditional microbiology tests suggests a subset of tests most relevant to use. The result is a hybrid classification system (electronic nose and traditional testing) that automatically exploits domain knowledge in the identification process.

  • 132.
    Alirezaie, Marjan
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Pecora, Federico
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Loutfi, Amy
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Context Recognition: Towards Automatic Query Generation2015Ingår i: Ambient Intelligence: 12th European Conference, AmI 2015, Athens, Greece, November 11-13, 2015, Proceedings, Springer, 2015, s. 205-218Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present an ontology-based approach in designing knowledge model for context recognition (CR) systems. The main focus in this paper is on the use of an ontology to facilitate the generation of user-based queries to the CR system. By leveraging from the ontology, users need not know about sensor details and the structure of the ontology in expressing queries related to events of interest. To validate the approach and demonstrate the flexibility of the ontology for query generation, the ontology has been integrated in two separate application domains. The first domain considers a health care system implemented for the GiraffPlus project where the query generation process is automated to request information about activities of daily living. The second application uses the same ontology for an air quality monitoring application in the home. Since these two systems are independently developed for different purposes, the ease of applying the ontology upon them can be considered as a credit for its generality.

  • 133.
    Alirezaie, Marjan
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Renoux, Jennifer
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Köckemann, Uwe
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Kristoffersson, Annica
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Karlsson, Lars
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Blomqvist, Eva
    RISE SICS East, Linköping, Sweden.
    Tsiftes, Nicolas
    RISE SICS, Stockholm, Sweden.
    Voigt, Thiemo
    RISE SICS, Stockholm, Sweden.
    Loutfi, Amy
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    An Ontology-based Context-aware System for Smart Homes: E-care@home2017Ingår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 17, nr 7, artikel-id 1586Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Smart home environments have a significant potential to provide for long-term monitoring of users with special needs in order to promote the possibility to age at home. Such environments are typically equipped with a number of heterogeneous sensors that monitor both health and environmental parameters. This paper presents a framework called E-care@home, consisting of an IoT infrastructure, which provides information with an unambiguous, shared meaning across IoT devices, end-users, relatives, health and care professionals and organizations. We focus on integrating measurements gathered from heterogeneous sources by using ontologies in order to enable semantic interpretation of events and context awareness. Activities are deduced using an incremental answer set solver for stream reasoning. The paper demonstrates the proposed framework using an instantiation of a smart environment that is able to perform context recognition based on the activities and the events occurring in the home.

  • 134.
    Alizadeh Noghani, Kyomaars
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Kassler, Andreas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    SDN enhanced Ethernet-VPN for Data Center Interconnect2017Ingår i: The Proceedings of the 2017 IEEE 6th International Conference on Cloud Networking (CloudNet), IEEE, 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ethernet Virtual Private Network (EVPN) is an emerging technology that addresses the networking challenges presented by geo-distributed Data Centers (DCs). One of the major advantages of EVPN over legacy layer 2 VPN solutions is providing All-Active (A-A) mode of operation so that the traffic can truly be multi-homed on Provider Edge (PE) routers. However, A-A mode of operation introduces new challenges. In the case where the Customer Edge (CE) router is multi-homed to one or more PE routers, it is necessary that only one of the PE routers should forward Broadcast, Unknown unicast, and Multicast (BUM) traffic into the DC. The PE router that assumes the primary role for forwarding BUM traffic to the CE device is called the Designated Forwarder (DF). The proposed solution to select the DF in the EVPN standard is based on a distributed algorithm which has a number of drawbacks such as unfairness and intermittent behavior. In this paper, we introduce a Software-Defined Networking (SDN) based architecture for EVPN support, where the SDN controller interacts with EVPN control plane. We demonstrate how our solution mitigates existing problems for DF selection which leads to improved EVPN performance

  • 135.
    Alm, Anton
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för datavetenskap (DV).
    Björling, Joakim
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för datavetenskap (DV).
    Prestandautvärdering av firmwares baserade på öppen källkod för routrar/brandväggar på MIPS-arkitektur: Jämförelse mellan Open-WRT, DD-WRT och Tomato firmware2014Självständigt arbete på grundnivå (högskoleexamen), 80 poäng / 120 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Den här undersökningen jämför prestanda hos tre olika firmwares som är baserade på öppen källkod. DD-WRT, Open-WRT samt Tomato Firmware för MIPS-arkitektur. Testerna följer två RFC som beskriver hur en prestandaanalys av ett nätverk ska genomföras.

    De sammanfattade resultaten pekar på en vinnare som presterat generellt bättre genom alla tester och det var Tomato firmware. Dessa resultat är hämtade från tre olika tester: genomströmningstest, svarstidstest och test med samtidiga sessioner.

    Undersökningen visar också att prestandan rent generellt är väldigt jämlik över alla firmwares i de olika testerna. En viktig aspekt är att det finns ingen överlägsen vinnare, vilket beror på, till exempel, hur konsekventa resultaten varit. Detta hänger även ihop med en möjlig slutsats där firmwaresen presterar olika bra beroende på vilken typ av uppgift det gäller.

    Som fortsatt arbete rekommenderas prestanda och funktionsanalys av liknande verktyg som varje firmware innehåller. Även en undersökning gällande gränssnittet för varje firmware skulle vara intressant.

  • 136.
    Almgren, David
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi.
    Alshammari, Hussam
    Högskolan i Halmstad, Akademin för informationsteknologi.
    SmartBand Alert: Ett armband för säkerhet2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Safety is a topic that is frequently discussed and spoken of in today’s society. An enhanced security for each individual is something many strive for in various industries. One of these is how to make the public feel more secure when the person in question, for example, is out walking late at night. The goal of this bachelors thesis is thus to describe and explain the product that has been developed to get ordinary people to feel more secure wherever they are. The chosen solution for this issue was hence to develop the product SmartBand Alert which consists of two parts. A bracelet and an application for IOS and Android. This bracelet should, by certain connectivity cooperate with the user’s phone to notify family members and/or others when the person thinks or knows that he or she is in danger. These persons will be notified with information about the person who has activated the alarm to simply and easily take the necessary actions to help the person. The product is designed to be used by anyone regardless of gender, age, and other characteristics individuals may hold.

  • 137.
    Almquist, Mathias
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Almquist, Viktor
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    A study on Android games: 3G energy consumption, CPU-utilization and system calls2015Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The popularity of mobile games has increased drastically during the recent years andmany people use them as their main source of entertainment. Mobile gamescommunicate with other devices over the network which consumes a lot of energy,especially when connected to cellular networks (e.g., 3G). This high energy expensecan feel unjustified to the player since always-on network connectivity is not requiredin order to play most games.Furthermore, the number of malware-infected applications in offical applicationstores has increased significantly in the recent years. These malware-infectedapplications can gain unrestricted access and control of users phones which can be athreat to security. Information about the behaviour characteristics of games can beused to develop or improve systems for detecting malware applications.In this thesis, 20 popular Android games are analysed with a focus on the datacommunication, CPU utilization and system call behaviour. The main subject of thedata communication study is the 3G communication energy consumed by games. Thesystem call study aims at quantifying the number and type of calls used by games.This may be useful in a further study of harmful behaviour by apps.The profiling results presented in this report show that the communication energyvaries drastically among games. Games with a very similar gameplay can consumevery different amounts of energy which indicates that there is room for improvementsin many of the games. Ad-free games consume significantly less energy than gamesthat use in-app advertisements. The results show that improving the advertisementfetching policy could reduce the energy consumption of these games. The majority ofthe games can be played without network connectivity and therefore thecommunication energy consumed could be completely avoided. The thesis alsoshows that games use a wide variety of system calls and that many of the system callsare common among the games.

  • 138.
    Almquist, Mathias
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Almquist, Viktor
    Linköpings universitet, Institutionen för datavetenskap.
    Analysis of 360° Video Viewing Behaviours2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this thesis we study users' viewing motions when watching 360° videos in order to provide information that can be used to optimize future view-dependent streaming protocols. More specifically, we develop an application that plays a sequence of 360° videos on an Oculus Rift Head Mounted Display and records the orientation and rotation velocity of the headset during playback. The application is used during an extensive user study in order to collect more than 21 hours of viewing data which is then analysed to expose viewing patterns, useful for optimizing 360° streaming protocols. 

  • 139.
    Almér, Alexander
    et al.
    Chalmers University of Technology and Gothenburg University, Sweden.
    von Hautwitz, Rickard
    Chalmers University of Technology and Gothenburg University, Sweden.
    Dodig-Crnkovic, Gordana
    Chalmers University of Technology and Gothenburg University, Sweden.
    Collective Cognition and Distributed Information Processing from Bacteria to Humans: Proc. AISB Conference Kent 2015.2015Ingår i: 41st Annual Convention of the Society for the Study of Artificial Intelligence and the Simulation of Behaviour: (AISB 2015), 2015, s. 119-124Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of this paper is to propose a general infocomputational model of cognition that can be applied to living organisms from the level of a single cell´s cognition to the level of groups of increasingly complex organisms with social, distributed cognition. We defend the project of new cognitivism, which unlike the old one acknowledges the central role of embodiment for cognition. Information processing going on in a cognising agent range from transduction of chemical signals and “quorum sensing” in bacteria, via simple local rules of behaviour that insects follow and that manifest themselves as “swarm intelligence”, to human level cognition with full richness of human languages and other systems of communication.

  • 140.
    Alnervik, Erik
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Evaluation of the Configurable Architecture REPLICA with Emulated Shared Memory2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    REPLICA är en grupp av konfigurerbara multiprocessorer som med hjälp utav ett emulerat delat minne realiserar PRAM modellen.

    Syftet med denna avhandling är att genom benchmarking av olika beräkningsproblem på REPLICA, liknande (SB-PRAM och XMT) och mindre lika (Xeon X5660 och Tesla M2050) parallella arkitekturer, utvärdera hur REPLICA står sig mot andra befintliga arkitekturer. Både prestandamässigt och hur enkel arkitekturen är att programmera effektiv, men även försöka ta reda på om REPLICA är speciellt lämpad för några särskilda typer av beräkningsproblem.

    Genom att använda välkända Berkeley dwarfs applikationer och opartisk indata från bland annat The University of Florida Sparse Matrix Collection och Rodinia benchmark suite, säkerställer vi att det är relevanta beräkningsproblem som utförs och mäts.

    Vi visar att dagens parallella arkitekturer har problem med prestandan för applikationer med oregelbundna minnesaccessmönster, vilken REPLICA arkitekturen kan vara en lösning på. Till exempel, så behöver REPLICA endast vara klockad med några få MHz för att matcha både Xeon X5660 och Tesla M2050 för algoritmen breadth first search, vilken lider av just oregelbunden minnesåtkomst. Genom att jämföra effektiviteten för REPLICA gentemot en CPU (Xeon X5660), visar vi att det är lättare att programmera REPLICA effektivt än dagens multiprocessorer.

  • 141.
    Aloisi, Alessandro
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem. University of Bologna (Italy).
    Enabling communication between Wireless Sensor Networks and The Internet-of-Things: A CoAP communication stack2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The thesis focuses on enabling the communication between Wireless Sensor Networks and Internet-of-Things applications.  In order to achieve this goal, the first step has been to investigate the concept of the Internet-of-Things and then to understand how this scenario could be used to interconnect multiple Wireless Sensor Networks in order to develop context-aware applications which could handle sensor data coming from this type of network. 

    The second step was to design and implement a communication stack which enabled Wireless Sensor Networks to communicate with an Internet-of-Things platform. The CoAP protocol has been used as application protocol for the communication with the Wireless Sensor Networks. The solution has been developed in Java programming language and extended the sensor and actuator layer of the Sensible Things platform. 

    The third step of this thesis has been to investigate in which real world applications the developed solution could have been used. Next a Proof of Concept application has been implemented in order to simulate a simple fire detection system, where multiple Wireless Sensor Networks collaborate to send their temperature data to a control center. The last step was to evaluate the whole system, specifically the responsiveness and the overhead introduced by the developed communication stack.

  • 142.
    Al-Otaibi, Ahmad
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Data- och elektroteknik.
    Hamed Oraibi, Yaser
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Data- och elektroteknik.
    AUTOMOTIVE BUS SYSTEM SCALABILITY2015Självständigt arbete på grundnivå (kandidatexamen), 180 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Sammanfattning

    Syfte: syftet med studien var att skapa en djupare förståelse om CAN-FD och hur den fungerar med Partial Network.

    Metod: Studien är en allmän litteraturstudie som är baserad på facklitteratur, datablad och intervju.

    Resultat: Studien visade att skalbarheten skiljde sig inte mellan CAN och CAN-FD. De största skillnader var hastigheten och datamängd mellan protokollen. Studien fann även att CAN-FD inte fungerade med Partial Network.

    Implikationer: Denna litteraturstudie är en bra introduktion och förhållning till företag som intresserar sig av CAN-FD. Studien kan bidra till ökat kunskap hos företagen om CAN-FD.

    Begränsningar: En kvantitativ metod skulle vara en användbar metod att utföra studien med. Detta skulle ge verkliga resultat som kan baserar på litteratur som använts i föreliggande studie. Ett problem som författarna upplevde var brist på vetenskaplig forskning om CAN-FD. Av den anledningen kan författarna inte dra en ren slutsats. 

  • 143.
    Al-Shishtawy, Ahmad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Self-Management for Large-Scale Distributed Systems2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Autonomic computing aims at making computing systems self-managing by using autonomic managers in order to reduce obstacles caused by management complexity. This thesis presents results of research on self-management for large-scale distributed systems. This research was motivated by the increasing complexity of computing systems and their management.

    In the first part, we present our platform, called Niche, for programming self-managing component-based distributed applications. In our work on Niche, we have faced and addressed the following four challenges in achieving self-management in a dynamic environment characterized by volatile resources and high churn: resource discovery, robust and efficient sensing and actuation, management bottleneck, and scale. We present results of our research on addressing the above challenges. Niche implements the autonomic computing architecture, proposed by IBM, in a fully decentralized way. Niche supports a network-transparent view of the system architecture simplifying the design of distributed self-management. Niche provides a concise and expressive API for self-management. The implementation of the platform relies on the scalability and robustness of structured overlay networks. We proceed by presenting a methodology for designing the management part of a distributed self-managing application. We define design steps that include partitioning of management functions and orchestration of multiple autonomic managers.

    In the second part, we discuss robustness of management and data consistency, which are necessary in a distributed system. Dealing with the effect of churn on management increases the complexity of the management logic and thus makes its development time consuming and error prone. We propose the abstraction of Robust Management Elements, which are able to heal themselves under continuous churn. Our approach is based on replicating a management element using finite state machine replication with a reconfigurable replica set. Our algorithm automates the reconfiguration (migration) of the replica set in order to tolerate continuous churn. For data consistency, we propose a majority-based distributed key-value store supporting multiple consistency levels that is based on a peer-to-peer network. The store enables the tradeoff between high availability and data consistency. Using majority allows avoiding potential drawbacks of a master-based consistency control, namely, a single-point of failure and a potential performance bottleneck.

    In the third part, we investigate self-management for Cloud-based storage systems with the focus on elasticity control using elements of control theory and machine learning. We have conducted research on a number of different designs of an elasticity controller, including a State-Space feedback controller and a controller that combines feedback and feedforward control. We describe our experience in designing an elasticity controller for a Cloud-based key-value store using state-space model that enables to trade-off performance for cost. We describe the steps in designing an elasticity controller. We continue by presenting the design and evaluation of ElastMan, an elasticity controller for Cloud-based elastic key-value stores that combines feedforward and feedback control.

  • 144.
    Al-Shishtawy, Ahmad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Programvaru- och datorsystem, SCS.
    Fayyaz, Muhammad Asif
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Programvaru- och datorsystem, SCS.
    Popov, Konstantin
    Swedish Institute of Computer Science (SICS), Kista, Sweden.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Programvaru- och datorsystem, SCS.
    Achieving Robust Self-Management for Large-Scale Distributed Applications2010Ingår i: Self-Adaptive and Self-Organizing Systems (SASO), 2010 4th IEEE International Conference on: SASO 2010, IEEE Computer Society, 2010, s. 31-40Konferensbidrag (Refereegranskat)
    Abstract [sv]

    Achieving self-management can be challenging, particularly in dynamic environments with resource churn (joins/leaves/failures). Dealing with the effect of churn on management increases the complexity of the management logic and thus makes its development time consuming and error prone. We propose the abstraction of robust management elements (RMEs), which are able to heal themselves under continuous churn. Using RMEs allows the developer to separate the issue of dealing with the effect of churn on management from the management logic. This facilitates the development of robust management by making the developer focus on managing the application while relying on the platform to provide the robustness of management. RMEs can be implemented as fault-tolerant long-living services. We present a generic approach and an associated algorithm to achieve fault-tolerant long-living services. Our approach is based on replicating a service using finite state machine replication with a reconfigurable replica set. Our algorithm automates the reconfiguration (migration) of the replica set in order to tolerate continuous churn. The algorithm uses P2P replica placement schemes to place replicas and uses the P2P overlay to monitor them. The replicated state machine is extended to analyze monitoring data in order to decide on when and where to migrate. We describe how to use our approach to achieve robust management elements. We present a simulation-based evaluation of our approach which shows its feasibility.

  • 145.
    Al-Shishtawy, Ahmad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    ElastMan: Autonomic elasticity manager for cloud-based key-value stores2013Ingår i: HPDC 2013 - Proceedings of the 22nd ACM International Symposium on High-Performance Parallel and Distributed Computing, 2013, s. 115-116Konferensbidrag (Refereegranskat)
    Abstract [en]

    The increasing spread of elastic Cloud services, together with the pay-as-you-go pricing model of Cloud computing, has led to the need of an elasticity controller. The controller automatically resizes an elastic service in response to changes in workload, in order to meet Service Level Objectives (SLOs) at a reduced cost. However, variable performance of Cloud virtual machines and nonlinearities in Cloud services complicates the controller design. We present the design and evaluation of ElastMan, an elasticity controller for Cloud-based elastic key-value stores. ElastMan combines feedforward and feedback control. Feedforward control is used to respond to spikes in the workload by quickly resizing the service to meet SLOs at a minimal cost. Feedback control is used to correct modeling errors and to handle diurnal workload. We have implemented and evaluated ElastMan using the Voldemort key-value store running in a Cloud environment based on OpenStack. Our evaluation shows the feasibility and effectiveness of our approach to automation of Cloud service elasticity.

  • 146.
    Al-Shishtawy, Ahmad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    ElastMan: Autonomic Elasticity Manager for Cloud-Based Key-Value Stores2012Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The increasing spread of elastic Cloud services, together with the pay-asyou-go pricing model of Cloud computing, has led to the need of an elasticity controller. The controller automatically resizes an elastic service, in response to changes in workload, in order to meet Service Level Objectives (SLOs) at a reduced cost. However, variable performance of Cloud virtual machines and nonlinearities in Cloud services, such as the diminishing reward of adding a service instance with increasing the scale, complicates the controller design. We present the design and evaluation of ElastMan, an elasticity controller for Cloud-based elastic key-value stores. ElastMan combines feedforward and feedback control. Feedforward control is used to respond to spikes in the workload by quickly resizing the service to meet SLOs at a minimal cost. Feedback control is used to correct modeling errors and to handle diurnal workload. To address nonlinearities, our design of ElastMan leverages the near-linear scalability of elastic Cloud services in order to build a scale-independent model of the service. Our design based on combining feedforward and feedback control allows to efficiently handle both diurnal and rapid changes in workload in order to meet SLOs at a minimal cost. Our evaluation shows the feasibility of our approach to automation of Cloud service elasticity.

  • 147.
    Al-Shishtawy, Ahmad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    ElastMan: Elasticity manager for elastic key-value stores in the cloud2013Ingår i: Proceedings of the 2013 ACM Cloud and Autonomic Computing Conference, New York, NY, USA: Association for Computing Machinery (ACM), 2013, s. 7:1-7:10Konferensbidrag (Refereegranskat)
    Abstract [en]

    The increasing spread of elastic Cloud services, together with the pay-as-you-go pricing model of Cloud computing, has led to the need of an elasticity controller. The controller automatically resizes an elastic service in response to changes in workload, in order to meet Service Level Objectives (SLOs) at a reduced cost. However, variable performance of Cloud Virtual Machines and nonlinearities in Cloud services, such as the diminishing reward of adding a service instance with increasing the scale, complicates the controller design. We present the design and evaluation of ElastMan, an elasticity controller for Cloud-based elastic key-value stores. ElastMan combines feedforward and feedback control. Feedforward control is used to respond to spikes in the workload by quickly resizing the service to meet SLOs at a minimal cost. Feedback control is used to correct modeling errors and to handle diurnal workload. To address nonlinearities, our design of ElastMan leverages the near-linear scalability of elastic Cloud services in order to build a scale-independent model of the service. We have implemented and evaluated ElastMan using the Voldemort key-value store running in an OpenStack Cloud environment. Our evaluation shows the feasibility and effectiveness of our approach to automation of Cloud service elasticity.

  • 148.
    Altenbernd, Peter
    et al.
    University of Applied Sciences Darmstadt, Germany.
    Ermedahl, Andreas
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Lisper, Björn
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Gustafsson, Jan
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Automatic Generation of Timing Models for Timing Analysis of High-Level Code2011Ingår i: 19th International Conference on Real-Time and Network Systems (RTNS2011), 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Traditional timing analysis is applied only in the late stages of embedded system software development, when the hardware is available and the code is compiled and linked. However, preliminary timing estimates are often needed already in early stages of system development, both for hard and soft real-time systems. If the hardware is not yet fully accessible, or the code is not yet ready to compile or link, then the timing estimation must be done for the source code rather than for the binary. This paper describes how source-level timing models can be derived automatically for given combinations of hardware architecture and compiler. The models are identified from measured execution times for a set of synthetic "training programs" compiled for the hardware platform in question. The models can be used to derive source-level WCET estimates, as well as for estimating the execution times for single program runs. Our experiments indicate that the models can predict the execution times of the final, compiled code with a deviation up to 20%.

  • 149.
    Altenbernd, Peter
    et al.
    University of Applied Sciences, Germany.
    Gustafsson, Jan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Lisper, Björn
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Stappert, Friedhelm
    Siemens VDO Automotive AG, Germany.
    Early execution time-estimation through automatically generated timing models2016Ingår i: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 52, nr 6, s. 731-760Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Traditional timing analysis, such as worst-case execution time analysis, is normally applied only in the late stages of embedded system software development, when the hardware is available and the code is compiled and linked. However, preliminary timing estimates are often needed in early stages of system development as an essential prerequisite for the configuration of the hardware setup and dimensioning of the system. During this phase the hardware is often not available, and the code might not be ready to link. This article describes an approach to predict the execution time of software through an early, source-level timing analysis. A timing model for source code is automatically derived from a given combination of hardware architecture and compiler. The model is identified from measured execution times for a set of synthetic training programs, compiled for the hardware platform in question. It can be used to estimate the execution time for code running on the platform: the estimation is then done directly from the source code, without compiling and running it. Our experiments show that, using this model, we can predict the execution times of the final, compiled code surprisingly well. For instance, we achieve an average deviation of 8 % for a set of benchmark programs for the ARM7 architecture.

  • 150.
    Al-Trad, Anas
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Optimized Composition of Parallel Components on a Linux Cluster2012Självständigt arbete på avancerad nivå (masterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
    Abstract [en]

    We develop a novel framework for optimized composition of explicitly parallel software components with different implementation variants given the problem size, data distribution scheme and processor group size on a Linux cluster. We consider two approaches (or two cases of the framework). 

    In the first approach, dispatch tables are built using measurement data obtained offline by executions for some (sample) points in the ranges of the context properties. Inter-/extrapolation is then used to do actual variant-selection for a given execution context at run-time.

    In the second approach, a cost function of each component variant is provided by the component writer for variant-selection. These cost functions can internally lookup measurements' tables built, either offline or at deployment time, for computation- and communication-specific primitives.

    In both approaches, the call to an explicitly parallel software component (with different implementation variants) is made via a dispatcher instead of calling a variant directly.

    As a case study, we apply both approaches on a parallel component for matrix multiplication with multiple implementation variants. We implemented our variants using Message Passing Interface (MPI). The results show the reduction in execution time for the optimally composed applications compared to applications with hard-coded composition. In addition, the results show the comparison of estimated and measured times for each variant using different data distributions, processor group and problem sizes.

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