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  • 1.
    Akil, Mahdi
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Martucci, Leonardo
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Hoepman, Jaap-Henk
    Radboud University, The Netherlands.
    Non-Interactive Privacy-Preserving Sybil-Free Authentication Scheme in VANETs2023In: Network and Distributed System Security (NDSS) Symposium: Inaugural Symposium on Vehicle Security and Privacy (VehicleSec 2023), Internet Society , 2023Conference paper (Refereed)
    Abstract [en]

    In vehicular ad hoc networks (VANETs), vehicles exchange messages to improve traffic and passengers’ safety. In VANETs, (passive) adversaries can track vehicles (and their drivers) by analyzing the data exchanged in the network. The use of privacy-enhancing technologies can prevent vehicle tracking but solutions so far proposed either require an intermittent connection to a fixed infrastructure or allow vehicles to generate concurrent pseudonyms which could lead to identity-based (Sybil) attacks. In this paper, we propose an anonymous authentication scheme that does not require a connection to a fixed infrastructure during operation and is not vulnerable to Sybil attacks. Our scheme is built on attribute-based credentials and short lived pseudonyms. In it, vehicles interact with a central authority only once, for registering themselves, and then generate their own pseudonyms without interacting with other devices, or relying on a central authority or a trusted third party. The pseudonyms are periodically refreshed, following system wide epochs.

    Download full text (pdf)
    vehiclesec2023-23007-paper.pdf
  • 2.
    Alay, Özgü
    et al.
    Simula Research Laboratory, Norway.
    Lutu, Andra
    Simula Research Laboratory, Norway.
    Peón-Quirós, Miguel
    IMDEA Networks Institute, Spain.
    Mancuso, Vincenzo
    IMDEA Networks Institute, Spain.
    Hirsch, Thomas
    Celerway Communications, Norway.
    Evensen, Kristian
    Celerway Communications, Norway.
    Hansen, Audun
    Celerway Communications, Norway.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Karlsson, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Safari Khatouni, Ali
    Politecnico di Torino, Italy.
    Mellia, Marco
    Politecnico di Torino, Italy.
    Ajmone Marsan, Marco
    IMDEA Networks Institute, Spain and Politecnico di Torino, Italy.
    Experience: An open platform for experimentation with commercial mobile broadband networks2017In: MobiCom '17 Proceedings of the 23rd Annual International Conference on Mobile Computing and Networking, New York: Association for Computing Machinery (ACM), 2017, p. 70-78Conference paper (Refereed)
    Abstract [en]

    Open experimentation with operational Mobile Broadband (MBB) networks in the wild is currently a fundamental requirement of the research community in its endeavor to address the need of innovative solutions for mobile communications. Even more, there is a strong need for objective data about stability and performance of MBB (e.g., 3G/4G) networks, and for tools that rigorously and scientifically assess their status. In this paper, we introduce the MONROE measurement platform: an open access and flexible hardware-based platform for measurements and custom experimentation on operational MBB networks. The MONROE platform enables accurate, realistic and meaningful assessment of the performance and reliability of 11 MBB networks in Europe. We report on our experience designing, implementing and testing the solution we propose for the platform. We detail the challenges we overcame while building and testing the MONROE testbed and argue our design and implementation choices accordingly. We describe and exemplify the capabilities of the platform and the wide variety of experiments that external users already perform using the system

  • 3.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Impact of TCP Congestion Control on Bufferbloat in Cellular Networks2013In: Proceedings of the 14th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM 2013) / [ed] Angelos Lazaris, Balaji Rengarajan, IEEE Press, 2013Conference paper (Refereed)
    Abstract [en]

    The existence of excessively large and too filled network buffers, known as bufferbloat, has recently gained attention as a major performance problem for delay-sensitive applications. One important network scenario where bufferbloat may occur is cellular networks.

    This paper investigates the interaction between TCP congestion control and buffering in cellular networks. Extensive measurements have been performed in commercial 3G, 3.5G and 4G cellular networks, with a mix of long and short TCP flows using the CUBIC, NewReno and Westwood+ congestion control algorithms. The results show that the completion times of short flows increase significantly when concurrent long flow traffic is introduced. This is caused by increased buffer occupancy from the long flows. In addition, for 3G and 3.5G the completion times are shown to depend significantly on the congestion control algorithms used for the background flows, with CUBIC leading to significantly larger completion times.

  • 4.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Observations of Bufferbloat in Swedish Cellular Networks2013In: Proceedings of the 9th Swedish National Computer Networking Workshop (SNCNW 2013) / [ed] Bengt Ahlgren, 2013Conference paper (Refereed)
  • 5.
    Ali, Usman
    et al.
    Sapienza University of Rome, Italy.
    Caso, Giuseppe
    Ericsson AB, Kista, Sweden.
    De Nardis, Luca
    Sapienza University of Rome, Italy.
    Kousias, Konstantinos
    Simula Research Laboratory, Norway.
    Rajiullah, Mohammad
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alay, Özgü
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013). University of Oslo, Norway.
    Neri, Marco
    Rohde & Schwarz, Italy..
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Di Benedetto, Maria-Gabriella
    Sapienza University of Rome, Italy.
    Data-Driven Analysis of Outdoor-to-Indoor Propagation for 5G Mid-Band Operational Networks2022In: Future Internet, E-ISSN 1999-5903, Vol. 14, no 8, p. 1-27, article id 239Article in journal (Refereed)
    Abstract [en]

    The successful rollout of fifth-generation (5G) networks requires a full understanding of the behavior of the propagation channel, taking into account the signal formats and the frequencies standardized by the Third Generation Partnership Project (3GPP). In the past, channel characterization for 5G has been addressed mainly based on the measurements performed on dedicated links in experimental setups. This paper presents a state-of-the-art contribution to the characterization of the outdoor-to-indoor radio channel in the 3.5 GHz band, based on experimental data for commercial, deployed 5G networks, collected during a large scale measurement campaign carried out in the city of Rome, Italy. The analysis presented in this work focuses on downlink, outdoor-to-indoor propagation for two operators adopting two different beamforming strategies, single wide-beam and multiple synchronization signal blocks (SSB) based beamforming; it is indeed the first contribution studying the impact of beamforming strategy in real 5G networks. The time and power-related channel characteristics, i.e., mean excess delay and Root Mean Square (RMS) delay spread, path loss, and K-factor are studied for the two operators in multiple measurement locations. The analysis of time and power-related parameters is supported and extended by a correlation analysis between each pair of parameters. The results show that beamforming strategy has a marked impact on propagation. A single wide-beam transmission leads, in fact, to lower RMS delay spread and lower mean excess delay compared to a multiple SSB-based transmission strategy. In addition, the single wide-beam transmission system is characterized by a smaller path loss and a higher K-factor, suggesting that the adoption of a multiple SSB-based transmission strategy may have a negative impact on downlink performance.

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    fulltext
  • 6.
    Alizadeh Noghani, Kyoomars
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT (discontinued), Department of Computer Science.
    Taheri, Javid
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Ohlen, Peter
    Ericsson Research, Sweden.
    Curescu, Calin
    Ericsson Research, Sweden.
    Multi-Objective genetic algorithm for fast service function chain reconfiguration2023In: IEEE Transactions on Network and Service Management, ISSN 1932-4537, E-ISSN 1932-4537, Vol. 20, no 3, p. 3501-3522Article in journal (Refereed)
    Abstract [en]

    The optimal placement of virtual network functions (VNFs) improves the overall performance of servicefunction chains (SFCs) and decreases the operational costs formobile network operators. To cope with changes in demands,VNF instances may be added or removed dynamically, resourceallocations may be adjusted, and servers may be consolidated.To maintain an optimal placement of SFCs when conditionschange, SFC reconfiguration is required, including the migration of VNFs and the rerouting of service-flows. However, suchreconfigurations may lead to stress on the VNF infrastructure,which may cause service degradation. On the other hand, notchanging the placement may lead to suboptimal operation,and servers and links may become congested or underutilized,leading to high operational costs. In this paper, we investigatethe trade-off between the reconfiguration of SFCs and theoptimality of their new placement and service-flow routing. Wedevelop a multi-objective genetic algorithm that explores thePareto front by balancing the optimality of the new placementand the cost to achieve it. Our numerical evaluations show thata small number of reconfigurations can significantly reduce theoperational cost of the VNF infrastructure. In contrast, toomuch reconfiguration may not pay off due to high costs. Webelieve that our work provides an important tool that helpsnetwork providers to plan a good reconfiguration strategy fortheir service chains.

  • 7.
    Badariah Asan, Noor
    et al.
    Uppsala University, Sweden; Malaysia.
    Hassan, Emadeldeen
    Umeå universitet, Institutionen för datavetenskap; Egypt.
    Velander, Jacob
    Uppsala University, Sweden.
    Redzwan Mohd Shah, Syaiful
    Uppsala University, Sweden.
    Noreland, Daniel
    Umeå universitet, Institutionen för datavetenskap.
    Blokhuis, Taco J.
    The Netherlands.
    Wadbro, Eddie
    Umeå universitet.
    Berggren, Martin
    Umeå universitet.
    Voigt, Thiemo
    Uppsala University, Sweden.
    Augustine, Robin
    Uppsala University, Sweden.
    Characterization of the Fat Channel for Intra-Body Communication at R-Band Frequencies2018In: Sensors, E-ISSN 1424-8220, Vol. 18, no 9, article id 2752Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate the use of fat tissue as a communication channel between in-body, implanted devices at R-band frequencies (1.7–2.6 GHz). The proposed fat channel is based on an anatomical model of the human body. We propose a novel probe that is optimized to efficiently radiate the R-band frequencies into the fat tissue. We use our probe to evaluate the path loss of the fat channel by studying the channel transmission coefficient over the R-band frequencies. We conduct extensive simulation studies and validate our results by experimentation on phantom and ex-vivo porcine tissue, with good agreement between simulations and experiments. We demonstrate a performance comparison between the fat channel and similar waveguide structures. Our characterization of the fat channel reveals propagation path loss of ∼0.7 dB and ∼1.9 dB per cm for phantom and ex-vivo porcine tissue, respectively. These results demonstrate that fat tissue can be used as a communication channel for high data rate intra-body networks.

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    FULLTEXT01
  • 8.
    Berthold, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Inter-temporal Privacy Metrics2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Informational privacy of individuals has significantly gained importance after information technology has become widely deployed. Data, once digitalised, can be copied, distributed, and long-term stored at negligible costs. This has dramatic consequences for individuals that leave traces in the form of personal data whenever they interact with information technology, for instance, computers and phones; or even when information technology is recording the personal data of aware or unaware individuals. The right of individuals for informational privacy, in particular to control the flow and use of their personal data, is easily undermined by those controlling the information technology.

    The objective of this thesis is to study the measurement of informational privacy with a particular focus on scenarios where an individual discloses personal data to a second party which uses this data for re-identifying the individual within a set of other individuals. We contribute with privacy metrics for several instances of this scenario in the publications included in this thesis, most notably one which adds a time dimension to the scenario for modelling the effects of the time passed between data disclosure and usage. The result is a new framework for inter-temporal privacy metrics.

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  • 9.
    Berthold, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Lundin, Reine
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Re-identification revisitedManuscript (preprint) (Other academic)
  • 10.
    Bozakov, Zdravko
    et al.
    Dell EMC, Ireland.
    Mangiante, Simone
    Dell EMC, Ireland.
    Hernandez Benet, Cristian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013). Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Santos, Ricardo
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Buckley, Donagh
    Dell EMC, Ireland.
    A NEAT framework for enhanced end-host integration in SDN environments2017In: 2017 IEEE Conference on Network Function Virtualization and Software Defined Networks (NFV-SDN), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    SDN aims to facilitate the management of increasingly complex, dynamic network environments and optimize the use of the resources available therein with minimal operator intervention. To this end, SDN controllers maintain a global view of the network topology and its state. However, the extraction of information about network flows and other network metrics remains a non-trivial challenge. Network applications exhibit a wide range of properties, posing diverse, often conflicting, demands towards the network. As these requirements are typically not known, controllers must rely on error-prone heuristics to extract them. In this work, we develop a framework which allows applications deployed in an SDN environment to explicitly express their requirements to the network. Conversely, it allows network controllers to deploy policies on end-hosts and to supply applications with information about network paths, salient servers and other relevant metrics. The proposed approach opens the door for fine grained, application-aware resource optimization strategies in SDNs

  • 11.
    Brunström, Anna
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Han, BoGeorge Mason University, USA.
    5G-MeMU 2021: Proceedings of the 2021 Workshop on 5G Measurements, Modeling, and Use Cases2021Conference proceedings (editor) (Refereed)
  • 12.
    Budzisz, Łukasz
    et al.
    Technische Universität Berlin, Berlin, Germany.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Ferrús, Ramon
    Universitat Politècnica de Catalunya, Barcelona, Spain.
    A taxonomy and survey of SCTP research2012In: ACM Computing Surveys, ISSN 0360-0300, E-ISSN 1557-7341, Vol. 44, no 4, p. -36, article id 18Article in journal (Refereed)
    Abstract [en]

    The Stream Control Transmission Protocol (SCTP) is a relatively recent general-purpose transport layer protocol for IP networks that has been introduced as a complement to the well-established TCP and UDP transport protocols. Although initially conceived for the transport of PSTN signaling messages over IP networks, the introduction of key features in SCTP, such as multihoming and multistreaming, has spurred considerable research interest surrounding SCTP and its applicability to different networking scenarios. This article aims to provide a detailed survey of one of these new features—multihoming—which, as it is shown, is the subject of evaluation in more than half of all published SCTP-related articles. To this end, the article first summarizes and organizes SCTP-related research conducted so far by developing a four-dimensional taxonomy reflecting the (1) protocol feature examined, (2) application area, (3) network environment, and (4) study approach. Over 430 SCTP-related publications have been analyzed and classified according to the proposed taxonomy. As a result, a clear perspective on this research area in the decade since the first protocol standardization in 2000 is given, covering both current and future research trends. On continuation, a detailed survey of the SCTP multihoming feature is provided, examining possible applications of multihoming, such as robustness, handover support, and loadsharing.

  • 13.
    Caso, G.
    et al.
    Simula Metropolitan CDE, NOR.
    Kousias, K.
    Simula Research Laboratory, NOR.
    Alay, O.
    University of Oslo, NOR; Simula Metropolitan CDE, NOR.
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Neri, M.
    Rohde & Schwarz, ITA .
    NB-IoT Random Access: Data-driven Analysis and ML-based Enhancements2021In: IEEE Internet of Things Journal, ISSN 2327-4662Article in journal (Refereed)
    Abstract [en]

    In the context of massive Machine Type Communications (mMTC), the Narrowband Internet of Things (NB-IoT) technology is envisioned to efficiently and reliably deal with massive device connectivity. Hence, it relies on a tailored Random Access (RA) procedure, for which theoretical and empirical analyses are needed for a better understanding and further improvements. This paper presents the first data-driven analysis of NB-IoT RA, exploiting a large scale measurement campaign. We show how the RA procedure and performance are affected by network deployment, radio coverage, and operators’ configurations, thus complementing simulation-based investigations, mostly focused on massive connectivity aspects. Comparison with the performance requirements reveals the need for procedure enhancements. Hence, we propose a Machine Learning (ML) approach, and show that RA outcomes are predictable with good accuracy by observing radio conditions. We embed the outcome prediction in a RA enhanced scheme, and show that optimized configurations enable a power consumption reduction of at least 50%. We also make our dataset available for further exploration, toward the discovery of new insights and research perspectives.

  • 14.
    Caso, Giuseppe
    et al.
    Simula Metropolitan CDE, NOR.
    Alay, Özgü
    University of Oslo, NOR; Simula Metropolitan CDE, NOR.
    De Nardis, Luca De
    Sapienza University of Rome, ITA.
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Neri, Marco
    Rohde&Schwarz.
    Di Benedetto, Maria Gabriella
    Sapienza University of Rome, ITA.
    Empirical Models for NB-IoT Path Loss in an Urban Scenario2021In: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 8, no 17, p. 13774-13788Article in journal (Refereed)
    Abstract [en]

    The lack of publicly available large scale measurements has hindered the derivation of empirical path loss (PL) models for Narrowband Internet of Things (NB-IoT). Therefore, simulation-based investigations currently rely on models conceived for other cellular technologies, which are characterized, however, by different available bandwidth, carrier frequency, and infrastructure deployment, among others. In this paper, we take advantage of data from a large scale measurement campaign in the city of Oslo, Norway, to provide the first empirical characterization of NB-IoT PL in an urban scenario. For the PL average term, we characterize Alpha-Beta-Gamma (ABG) and Close-In (CI) models. By analyzing multiple NBIoT cells, we propose a statistical PL characterization, i.e., the model parameters are not set to a single, constant value across cells, but are randomly extracted from well-known distributions. Similarly, we define the PL shadowing distribution, correlation over distance, and inter-site correlation. Finally, we give initial insights on outdoor-to-indoor propagation, using measurements up to deep indoor scenarios. The proposed models improve PL estimation accuracy compared to the ones currently adopted in NB-IoT investigations, enabling more realistic simulations of urban scenarios similar to the sites covered by our measurements.

  • 15.
    Chahed, Hamza
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Software-Defined Time Sensitive Networks Configuration and Management2021In: 2021 IEEE Conference on Network Function Virtualization and Software Defined Networks: NFV-SDN 2021, Institute of Electrical and Electronics Engineers (IEEE), 2021, p. 124-128Conference paper (Refereed)
    Abstract [en]

    Deterministic real time networking is typically provided by dedicated fieldbus networks which prevents innovation due to their proprietary nature, inflexibility and high-cost. Recently, Time Sensitive Networking (TSN) emerged as a set of Ethernet enhancements, which enables innovation in deterministic networking areas thanks to its openness and capability to serve a variety of traffic types over a converged network infrastructure. However, configuration and management of TSN is difficult due to the complexity of mechanisms that need to be deployed, configured and managed in order to provide real-Time guarantees. Luckily, with recent advancements in the area of software-defined networking (SDN), control plane programmability is simplified, also enabling logically centralized view for network configuration methods. In this paper, we focus on the potential of SDN for the configuration and management of TSN elements. We aim to contribute to an (i) understanding on how SDN can help in the configuration of TSN and (ii) propose a standards compliant TSN network controller, using micro-service architecture for flexibility and scalability. We motivate the potential and discuss the main research questions related to its design.

  • 16.
    De Nardis, Luca
    et al.
    Sapienza University of Rome, Italy.
    Caso, Giuseppe
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alay, Özgü
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013). University of Oslo, Norway.
    Neri, Marco
    Rohde & Schwarz, Italy.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Di Benedetto, Maria-Gabriella
    Sapienza University of Rome, Italy.
    Positioning by Multicell Fingerprinting in UrbanNB-IoT Networks2023In: Sensors, E-ISSN 1424-8220, Vol. 23, no 9, article id 4266Article in journal (Refereed)
    Abstract [en]

    Narrowband Internet of Things (NB-IoT) has quickly become a leading technology in the deployment of IoT systems and services, owing to its appealing features in terms of coverage and energy efficiency, as well as compatibility with existing mobile networks. Increasingly, IoT services and applications require location information to be paired with data collected by devices; NB-IoT still lacks, however, reliable positioning methods. Time-based techniques inherited from long-term evolution (LTE) are not yet widely available in existing networks and are expected to perform poorly on NB-IoT signals due to their narrow bandwidth. This investigation proposes a set of strategies for NB-IoT positioning based on fingerprinting that use coverage and radio information from multiple cells. The proposed strategies were evaluated on two large-scale datasets made available under an open-source license that include experimental data from multiple NB-IoT operators in two large cities: Oslo, Norway, and Rome, Italy. Results showed that the proposed strategies, using a combination of coverage and radio information from multiple cells, outperform current state-of-the-art approaches based on single cell fingerprinting, with a minimum average positioning error of about 20 m when using data for a single operator that was consistent across the two datasets vs. about 70 m for the current state-of-the-art approaches. The combination of data from multiple operators and data smoothing further improved positioning accuracy, leading to a minimum average positioning error below 15 m in both urban environments. 

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  • 17.
    Dely, Peter
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Architectures and Algorithms for Future Wireless Local Area Networks2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Future Wireless Local Area Networks (WLANs) with high carrier frequencies and wide channels need a dense deployment of Access Points (APs) to provide good performance. In densely deployed WLANs associations of stations and handovers need to be managed more intelligently than today.

    This dissertation studies when and how a station should perform a handover and to which AP from a theoretical and a practical perspective. We formulate and solve optimization problems that allow to compute the optimal AP for each station in normal WLANs and WLANs connected via a wireless mesh backhaul. Moreover, we propose to use software defined networks and the OpenFlow protocol to optimize station associations, handovers and traffic rates. Furthermore, we develop new mechanisms to estimate the quality  of a link  between a station and an AP. Those mechanisms allow optimization algorithms to make better decisions about when to initiate a handover. Since handovers in today’s WLANs are slow and may disturb real-time applications such as video streaming, a faster procedure is developed in this thesis.

    Evaluation results from wireless testbeds and network simulations show that our architectures and algorithms significantly increase the performance of WLANs, while they are backward compatible at the same time.

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    KUS_2012_53
  • 18.
    di stasi, Giovanni
    et al.
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    Karlsson, Jonas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Avallone, Stefano
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    Canonico, Roberto
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Combining Multi-Path Forwarding and Packet Aggregation for Improved Network Performance in Wireless Mesh Networks2014In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 68, p. 26-37Article in journal (Refereed)
    Abstract [en]

    Wireless mesh networks (WMNs) based on the IEEE 802.11 standard are becoming increasingly popular as a viable alternative to wired networks. WMNs can cover large or difficult to reach areas with low deployment and management costs. Several multi-path routing algorithms have been proposed for such kind of networks with the objective of load balancing the traffic across the network and providing robustness against node or link failures. Packet aggregation has also been proposed to reduce the overhead associated with the transmission of frames, which is not negligible in IEEE 802.11 networks. Unfortunately, multi-path routing and packet aggregation do not work well together, as they pursue different objectives. Indeed, while multi-path routing tends to spread packets among several next-hops, packet aggregation works more efficiently when several packets (destined to the same next-hop) are aggregated and sent together in a single MAC frame. In this paper, we propose a technique, called aggregation aware forwarding, that can be applied to existing multi-path routing algorithms to allow them to effectively exploit packet aggregation so as to increase their network performance. In particular, the proposed technique does not modify the path computation phase,but it just influences the forwarding decisions by taking the state of the sending queues into account.We demonstrated our proposed technique by applying it to Layer-2.5, a multi-path routing and forwarding paradigm for WMNs that has been previously proposed.We conducted a thorough performance evaluation by means of the ns-3 network simulator, which showed that our technique allows to increase the performance both in terms of network throughput and end-to-end delay.

  • 19.
    Eilu, Emmanuel
    et al.
    Uganda Christian University, Mbale University College, UGA.
    Baguma, RehemaMakerere University, UGA.Pettersson, John SörenKarlstad University, Faculty of Arts and Social Sciences (starting 2013), Karlstad Business School (from 2013).Bhuktar, Ganesh D.Vishwakarma Institute of Technology (VIT), IND.
    Digital Literacy and Socio-Cultural Acceptance of ICT in Developing Countries2021Collection (editor) (Refereed)
    Abstract [en]

    This book discusses the role of human computer interaction (HCI) design in fostering digital literacy and promoting socio-cultural acceptance and usage of the  latest ICT innovations in developing countries. The book presents techniques, theories, case studies, and methodologies in HCI design approaches that have been used to foster digital literacy, break the socio-cultural barriers to ICT adoption, and promote the widespread usage of the latest innovations in the health, agriculture, economic, education and social sectors in developing countries. The authors provide insights on how crossing disciplines in HCI such as usability design, user centered design, user experience, anticipated user experience, technology acceptance design, persuasive design, philosophical designs, motivational design, social-cultural oriented designs, and other HCI design approaches have promoted digital literacy and stimulated socio-cultural acceptance and the usage of the latest ICT innovations. The book is relevant in academic, industry and government.

    Presents theoretical, practical, and socio-cultural approaches to digital literacy challenges in developing countries;Discusses recent ICT and HCI innovations used to transform the health, agriculture, economic, education and social sectors in developing countries;Provides insights on design opportunities and challenges presented in countries where digital literacy is very low and with complex socio-cultural dynamics.

  • 20.
    Eklund, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Grinnemo, Karl-Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Stream-aware Scheduling to Improve Latency for Signaling Traffic using CMT-SCTP2016Conference paper (Refereed)
    Abstract [en]

    To mitigate delay spikes during transmission ofbursty signaling traffic, concurrent multipath transmission(CMT) over several paths in parallel could be an option. Still,unordered delivery is a well known problem when transmittingover asymmetric network paths, leading to extra delay due toHead-of-Line Blocking (HoLB). The Stream Control TransmissionProtocol (SCTP) is designed as a carrier for signaling trafficover IP to reduce the impact of HoLB. SCTP has support fortransmission of separate flows, called SCTP streams. SCTP iscurrently being extended with support for CMT (CMT-SCTP). Inthis paper, we address sender scheduling to optimize latency forsignaling traffic over CMT-SCTP. We present dynamic streamaware(DS) scheduling, which utilizes the SCTP stream concept,and continuously considers the current network status as well asthe data load to make scheduling decisions. We implement a DSScheduler and compare it against a dynamic path (DP) schedulerthat does not consider streams. Our investigation shows that DSscheduling could significantly reduce latency compared to a DPscheduler.

  • 21.
    Fernández, Fátima
    et al.
    Ikerlan Technology Research Center, Spain.
    Zverev, Mihail
    Ikerlan Technology Research Center, Spain.
    Diez, Luis
    Universidad de Cantabria, Spain.
    Juárez, José R.
    Ikerlan Technology Research Center, Spain.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Agüero, Ramón
    Universidad de Cantabria, Spain.
    Flexible Priority-based Stream Schedulers in QUIC2023In: PE-WASUN 2023 - Proceedings of the International ACM Symposium on Performance Evaluation of Wireless Ad Hoc, Sensor, and Ubiquitous Networks, Association for Computing Machinery (ACM), 2023, p. 91-98Conference paper (Refereed)
    Abstract [en]

    The advent of mobile technologies has led to the development of novel services for end-users, with stringent needs and requirements. In the scope of 5G and Beyond 5G systems, non-Terrestrial networks are being considered to meet such demands, with special emphasis on high-speed communications and low latency. QUIC is a new transport protocol designed to reduce communications latency in many ways. Among other features, it enables the use of multiple streams to effectively manage data flows sent through its underlying UDP socket. This paper introduces an implementation of priority-based stream schedulers along with the design of a flexible interface. Exploiting the proposed approach, applications are able to set the required scheduling scheme, as well as the stream priorities. The feasibility of the proposed approach is validated through an extensive experiment campaign, which combines Docker containers and the ns-3 simulator to emulate different connectivity characteristics. The results evince that an appropriate stream scheduler can indeed yield lower delays for strict time-sensitive applications by up to 36% under unreliable conditions. 

  • 22.
    Fida, Mah-Rukh
    et al.
    University of Edinburgh, UK.
    Kousias, Konstantinos
    Simula Research Laboratory, Norway.
    Lutu, Andra
    Simula Research Laboratory, Norway.
    Rajiullah, Mohammad
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alay, Özgü
    Simula Research Laboratory, Norway.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Argyriou, Antonios
    University of Thessaly, Greece.
    Demo: experimentation in controlled and operational LTE settings with FLEX-MONROE2017In: Proceedings of the 11th Workshop on Wireless Network Testbeds, Experimental evaluation & Characterization WiNTECH '17, Association for Computing Machinery (ACM), 2017, p. 93-94Conference paper (Refereed)
    Abstract [en]

    This demo paper presents FLEX-MONROE, a platform that facilitates better understanding of current LTE Mobile Broadband(MBB) networks and enables performance improvementsby allowing experimentation with controllable LTE parameters. The platform enables investigating impact oflow-level network parameter tweaks in LTE infrastructure onthe application performance. We argue that FLEX-MONROEis crucial to provide guidelines on improving application performance both in the current and future MBB networks

  • 23.
    Fischer, Andreas
    et al.
    University of Passau, DEU.
    De Meer, Hermann
    University of Passau, DEU.
    Generating Virtual Network Embedding Problems with Guaranteed Solutions2016In: IEEE Transactions on Network and Service Management, ISSN 1932-4537, E-ISSN 1932-4537, Vol. 13, no 3, p. 504-517Article in journal (Refereed)
    Abstract [en]

    The efficiency of network virtualization depends on the appropriate assignment of resources. The underlying problem, called Virtual Network Embedding, has been much discussed in the literature, and many algorithms have been proposed, attempting to optimize the resource assignment in various respects. Evaluation of those algorithms requires a large number of randomly generated embedding scenarios. This paper presents a novel scenario generation approach and demonstrates how to produce scenarios with a guaranteed exact solution, thereby facilitating better evaluation of embedding algorithms.

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  • 24.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Delay metrics and delay characteristics: A study of four Swedish HSDPA+ and LTE networks2015In: 2015 European Conference on Networks and Communications (EuCNC), IEEE, 2015, p. 234-238Conference paper (Refereed)
    Abstract [en]

    Network delays and user perceived latencies are of major importance in many applications in cellular networks. Delays can be measured with multiple approaches and at different protocol layers. This work involves a detailed examination of several delay metrics from a network, transport, and application perspective. The study explores base delay as well as latency under load, capturing also the effect of buffering. The examination is based on a comprehensive active measurement campaign performed in the networks of four Swedish operators. The results show that the delay captured by different metrics can vary significantly, with delay captured from the TCP three-way-handshake and adaptive ping measurements giving the most consistent results for base network delay in our measurements. As expected, when background traffic is introduced measured delay increases by an order of magnitude due to buffering in the network, highlighting the importance of also capturing latency under load when describing network performance. Finally, using an analytic model of flow completion time, we show that well-selected network measurements can provide a good prediction of higher layer delay performance.

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  • 25.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Estimating data transfer capacity for intermittent connectivity: A transport aware model2016In: 2016 IEEE 27th Annual International Symposium On Personal, Indoor, And Mobile Radio Communications (PIMRC), New York: IEEE, 2016, p. 1-6Conference paper (Refereed)
    Abstract [en]

    Communication performed with mobile devices will experience varying levels of connectivity as the communication device moves in and out of coverage. A subset of mobile communication devices operate under conditions where the connectivity is characterized by relatively short contact periods occurring intermittently. In this paper we propose a model to predict the amount of data that can be transferred during such short contact periods. The model includes aspects of the transport layer slow-start behavior and is validated using data from a long-running measurement campaign in the networks of four Swedish cellular networks. Further validation of the modeling assumptions is performed by employing a numerical optimization technique based on non-linear least squares regression using the iterative Levenberg-Marquardt approach. The model is then used to explore the relevant parameter space.

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    fulltext
  • 26.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Examining TCP Short Flow Performance in Cellular Networks Through Active and Passive Measurements2015In: AllThingsCellular '15 Proceedings of the 5th Workshop on All Things Cellular: Operations, Applications and Challenges / [ed] David Choffnes and Kobus Van der Merwe, Association for Computing Machinery (ACM), 2015, p. 7-12Conference paper (Refereed)
    Abstract [en]

    In this study we examine the conditions in a current cellular network by examining data passively collected in the core of a cellular operator during a 24-hour period. More than 2 billion traffic measurement data points from over 500,000 cellular users are analyzed. The analysis characterizes the Time-of-Day (ToD) variations for traffic intensity and session length and serves as a complement to the active measurements also performed. A comprehensive active measurement campaign was completed in the HSDPA+ and LTE networks of the four major Swedish operators. We collect around 50,000 data points from stationary cellular modems and analyze the ToD variation pattern for underlying network layer metrics such as delay and throughput. In conjunction with the time-varying session size distribution obtained from the passive measurements, we then analyze the ToD impact on TCP flows of varying sizes. The ToD effects are examined using time series analysis with Lomb-Scargle periodograms and differential Bayesian Information Criterion to allow comparison of the relative impact of the network ToD effects. The results show that ToD effects are predominantly impacting longer-running flows, and although short flows are also impacted they are mostly constrained by other issues such as protocol efficiency.

  • 27.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Hurtig, Per
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Deterministic network emulation using KauNetEm2016Conference paper (Other academic)
    Abstract [en]

    This paper presents KauNetEm, an extension to the Linux-based NetEm emulator that provides deterministic network emulation. KauNetEm enables precise and repeatable placement of NetEm emulation effects, a functionality that canconsiderably simplify several aspects of protocol evaluation. KauNetEm can be instructed to drop specific packets, apply a configurable delay or other emulation effects at predefinedpoints in time. The motivation for deterministic emulation, the overall design of KauNetEm, and usage examples are provided

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  • 28.
    Garcia, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Hurtig, Per
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Getting What You Want When You Want It: Deterministic Network Emulation2016Conference paper (Refereed)
    Abstract [en]

    This paper presents KauNetEm, an extension to the Linux-based NetEm emulator that provides deterministic network emulation. KauNetEm enables precise and repeatable placement of NetEm emulation effects, a functionality that can considerably simplify several aspects of protocol evaluation. KauNetEm can be instructed to drop specific packets, apply a configurable delay or other emulation effects at predefined points in time. The motivation for deterministic emulation, the overall design of KauNetEm, and usage examples are provided.

  • 29.
    Hall, Tomas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Garcia, Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Performance Evaluation of KauNet in Physical and Virtual Emulation Environments2012Report (Other academic)
    Abstract [en]

    Evaluation of applications and protocols in the context of computer networking is often necessary to determine the efficiency and level of service they can provide. In practical testing, three different options are available for the evaluation; using a physical network as a testbed, using an emulator to simplify the infrastructure, or using a simulator to remove reliance on infrastructure entirely. As a real network is costly and difficult or even impossible to create for every scenario, emulation and simulation is often used to approximate the behavior of a network with considerably less resources required. However, while a simulator is limited only by the time required to perform the simulation, an emulator is also limited by the hardware and software used. It is therefore important to evaluate the performance of the emulator itself, to determine its ability to emulate the desired network topologies.

    The focus of this document is the KauNet emulator, an extension of Dummynet that adds several new features, primarily deterministic emulation of various network characteristics through the use of pre-generated patterns. A series of tests were per- formed using a testbed with KauNet in both physical and virtual environments, as well as a hybrid environment with both physical and virtual machines. While virtualization greatly increases the flexbility and utilization of resources compared to a pure physical setup, it may also reduce the overall performance and accuracy of the emulation.

    From the results achieved, KauNet performs well in a physical environment, with a high degree of accuracy even at high traffic loads. Virtualization on the other hand, clearly introduces several issues with both processing and packet loss that may make it undesirable for use in experiments, although it may still be sufficient for scenarios where the requirements for accuracy are lower. The hybrid environment represents a compromise, with both performance and flexibility midway between the physical and fully virtualized testbed. 

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  • 30.
    Hassan, Ahmad
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT. Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Hoque, Ahsanul
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Automated Microwave Antenna Alignment of Base Transceiver Station2011Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This master’s thesis is intended for the solution of Microwave (MW) link alignment which has several applications in modern communication systems. MW communication is used for point to point links with small wavelength and simultaneously compact antenna dimensions. Assuring the automated alignment of antennas provides a better communication between switching stations and allow its subscribers to communicate ceaselessly. In the first part of the work; effects of downtime on a network are discussed and at later stage a mechanism is investigated which will reduce the downtime. MW antenna used in communication systems is regularly affected by environmental factor and generally by wear and tear of mounts. These factors cause the precisely directed antennas to be perturbed from respective main lobes. Larger antennas with narrow main lobes require more sophisticated designing while smaller antennas have a broader main lobe. An automated antenna alignment that works without human intervention can decrease the down time and ensure a reliable communication between the near end and far end terminals of the Base Transceiver Station (BTS). The focus has been laid on a system that works autonomously and for that LabVIEW design and RCX Robonics Kit is used.  Results are presented to indicate antenna alignment in automatically synchronized manner.

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  • 31.
    Hassan, Emadeldeen
    et al.
    Umeå universitet, Institutionen för datavetenskap.
    Martynenko, Denys
    Germany.
    Wadbro, Eddie
    Umeå universitet, Institutionen för datavetenskap.
    Fischer, Gunter
    Germany.
    Berggren, Martin
    Umeå universitet, Institutionen för datavetenskap.
    Compact Differential-Fed Planar Filtering Antennas2019In: Electronics, E-ISSN 2079-9292, Vol. 8, no 11, article id 1241Article in journal (Refereed)
    Abstract [en]

    This paper proposes novel low-profile differential-fed planar antennas with embedded sharp frequency selectively. The antennas are compact and easy to integrate with differential devices without matching baluns. The antenna design is formulated as a topology optimization problem, where requirements on impedance bandwidth, directivity, and filtering are used as the design objectives. The optimized antennas operate over the frequency band 6.0-8.5 GHz. The antennas have reflection coefficients below -15 dB, cross-polarization levels below -42 dB, a maximum gain of 6.0 +/- 0.5 dB, and a uniform directivity over more than 130 degrees beamwidth angle in the frequency band of interest. In addition, the antennas exhibit sharp roll-off between the operational band and frequencies around the 5.8 GHz WiFi band and the 10 GHz X-band. One antenna has been fabricated with a good match between simulation and measurement results.

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  • 32.
    Hassan, Emadeldeen
    et al.
    Umeå universitet, Institutionen för datavetenskap.
    Scheiner, Benedict
    Michler, Fabian
    Berggren, Martin
    Umeå universitet, Institutionen för datavetenskap.
    Wadbro, Eddie
    Umeå universitet, Institutionen för datavetenskap.
    Röhrl, Franz
    Zorn, Stefan
    Weigel, Robert
    Lurz, Fabian
    Multilayer Topology Optimization of Wideband SIW-to-Waveguide Transitions2020In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 68, no 4, p. 1326-1339Article in journal (Refereed)
    Abstract [en]

    This article utilizes a topology optimization approach to design planar multilayer transitions between substrate integrated waveguides (SIWs) and rectangular waveguides (RWGs). The optimization problem is formulated based on the modal field analyses and Maxwell's equations in the time domain solved by the finite-difference time-domain (FDTD) method. We present a time-domain boundary condition based on the Klein–Gordon equation to split traveling waves at homogeneous waveguide ports. We employ the boundary condition to compute portal quantities and to devise an adjoint-field system that enabled an efficient computation of the objective function gradient. We solve design problems that include more than 105 000 design variables by using less than 400 solutions of Maxwell's equations. Moreover, a new formulation that effectively combats the development of in-band resonances in the design is presented. The transition configuration allows the direct mount of conventional RWG sections on the circuit board and aims to cover the entire K-band. The guiding structure of the optimized transition requires blind vias, which is realized by a simple and cost-efficient technique. In addition, the transition is optimized for three different setups that can be used to provide different field polarizations. The proposed transitions show less than 1-dB insertion loss and around 15-dB return loss over the frequency interval 18–28 GHz. Several prototypes are fabricated with an excellent match between the simulation and measurement results.

  • 33.
    Hassan, Emadeldeen
    et al.
    Umeå universitet.
    Wadbro, Eddie
    Umeå universitet, Institutionen för datavetenskap.
    Hägg, Linus
    Umeå universitet.
    Berggren, Martin
    Umeå universitet.
    Topology optimization of compact wideband coaxial-to-waveguide transitions with minimum-size control2018In: Structural and multidisciplinary optimization (Print), ISSN 1615-147X, E-ISSN 1615-1488, Vol. 57, no 4, p. 1765-1777Article in journal (Refereed)
    Abstract [en]

    This paper presents a density-based topology optimization approach to design compact wideband coaxial-to-waveguide transitions. The underlying optimization problem shows a strong self penalization towards binary solutions, which entails mesh-dependent designs that generally exhibit poor performance. To address the self penalization issue, we develop a filtering approach that consists of two phases. The first phase aims to relax the self penalization by using a sequence of linear filters. The second phase relies on nonlinear filters and aims to obtain binary solutions and to impose minimum-size control on the final design. We present results for optimizing compact transitions between a 50-Ohm coaxial cable and a standard WR90 waveguide operating in the X-band (8-12 GHz).

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  • 34.
    Hernandez Benet, Cristian
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Nasim, Robayet
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Alizadeh Noghani, Kyoomars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    OpenStackEmu - A Cloud Testbed Combining Network Emulation with OpenStack and SDN2017In: Consumer Communications & Networking Conference (CCNC), 2017 14th IEEE Annual, IEEE, 2017, p. 566-568Conference paper (Refereed)
    Abstract [en]

    OpenStack has been widely acknowledged to be one of the most important open source cloud platforms. In order to perform experimentally driven research in the area of cloud and cloud networking, there is however a big gap, because most researchers do not have access to a large cloud deployment and cannot change networking or compute infrastructure in order to test their algorithms and protocols on a large-scale. We developed OpenStackEmu, which is to the best of our knowledge the first attempt that combines OpenStack infrastructure with a Software Defined Networking (SDN) based controller such as OpenDaylight and a large-scale network emulator CORE (Common Open Research Emulator). The OpenStack compute and control nodes are connected to the CORE emulation server using TUN/TAP interfaces that inject the control (e.g. for VM migration) and data (VM-to-VM traffic) packets into a customizable network topology that is emulated using configurable Open vSwitches using CORE emulator. Experimenters can define e.g. fat-tree or distributed data center topologies and study the behavior of real VMs and services in those VMs under different background loads and SDN routing policies. We integrated the data center traffic generator DCT2Gen that allows to generate realistic background traffic based on traces from real data centers. Experimenters can study the performance impact of different VM migration strategies or different routing and load balancing schemes on real VM and application performance using different emulated topologies. We believe that OpenStackEmu is an important tool for both the SDN and OpenStack community in order to evaluate the performance of novel algorithms and protocols in the area of cloud networking.

  • 35.
    Hesselbäck, Philip
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Nordlund, Fredrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Checkout Automation using RFID: Utilization and Performance Testing2021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Radio-frequency identification (RFID) technology is used for automatic tracking and identification of marked items. RFID technology provides increased efficiency in aspects of time, handling and traceability of items within a supply chain.

    A challenge for an RFID reading technical solution is finding the right tuning and adjustments for an RFID reader, as these changes control the reading behaviour and process.

    In this thesis, the main objective is to implement and tune a technical RFID system. To achieve this, an RFID reading application needs to be designed and implemented with said goal in mind, meaning the application also needs to aid in testing purposes to find the optimal adjustments.

    An application was designed and then implemented in C#, with the ability to read RFID tags from an RFID reader and track reading parameters. To find the right tuning and adjustments for the RFID reading system, the reading parameters were analysed in different test cases.

    The optimal tuning and adjustments for RFID reading were found. The results also confirm that signal blocking materials in the form of metals, need to be taken into consideration when implementing an RFID solution. Furthermore, it was found that in order to ensure reading of RFID tags, RFID tags needs to be put stationary for a short period.

  • 36.
    Hosseini, Ahmad
    et al.
    Umeå universitet, Institutionen för matematik och matematisk statistik.
    Wadbro, Eddie
    Umeå universitet, Institutionen för datavetenskap.
    A feasibility evaluation approach for time-evolving multi-item production-distribution networks2016In: Optimization Methods and Software, ISSN 1055-6788, E-ISSN 1029-4937, Vol. 31, no 3, p. 562-576Article in journal (Refereed)
    Abstract [en]

    Time-dependent multi-item problems arise frequently in management applications, communication systems, and production–distribution systems. Our problem belongs to the last category, where we wish to address the feasibility of such systems when all network parameters change over time and product. The objective is to determine whether it is possible to have a dynamic production–shipment circuit within a finite planning horizon. And, if there is no such a flow, the goal is to determine where and when the infeasibility occurs and the approximate magnitude of the infeasibility. This information may help the decision maker in their efforts to resolve the infeasibility of the system. The problem in the discrete-time settings is investigated and a hybrid of scaling approach and penalty function method together with network optimality condition is utilized to develop a network-based algorithm. This algorithm is analysed from theoretical and practical perspectives by means of instances corresponding to some electricity transmission-distribution networks and many random instances. Computational results illustrate the performance of the algorithm.

  • 37.
    Hurtig, Per
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Alay, Ozgu
    Simula Research Laboratory.
    Ferlin, Simone
    Simula Research Laboratory.
    Yedugundla, Kiran
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Reducing Transport Latency using Multipath Protocols2015Conference paper (Refereed)
  • 38.
    Hurtig, Per
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Enhanced Metric Caching for Short TCP Flows2012In: Proceedings of the IEEE International Conference on Communications (ICC 2012), IEEE Press, 2012, p. 1209-1213Conference paper (Refereed)
    Abstract [en]

    Internet-based applications that require low latency are becoming more common. Such applications typically generate traffic consisting of short, or bursty, TCP flows. As TCP, instead, is designed to optimize the throughput of long bulk flows there is an apparent mismatch. To overcome this, a lot of research has recently focused on optimizing TCP for short flows as well. In this paper, we identify a performance problem for short flows caused by the metric caching conducted by the TCP control block interdependence mechanisms. Using this metric caching, a single packet loss can potentially ruin the performance for all future flows to the same destination by making them start in congestion avoidance instead of slow-start. To solve this, we propose an enhanced selective caching mechanism for short flows. To illustrate the usefulness of our approach, we implement it in both Linux and FreeBSD and experimentally evaluate it in a real test-bed. The experiments show that the selective caching approach is able to reduce the average transmission time of short flows by up to 40%.

  • 39.
    Hurtig, Per
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Petlund, Andreas
    Simula Research Laboratory AS.
    Welzl, Michael
    University of Oslo.
    TCP and Stream Control Transmission Protocol (SCTP) RTO Restart2016In: Internet RFCs, ISSN 2070-1721, no 7765Article in journal (Refereed)
    Abstract [en]

    This document describes a modified sender-side algorithm for managing the TCP and Stream Control Transmission Protocol (SCTP) retransmission timers that provides faster loss recovery when there is a small amount of outstanding data for a connection. The modification, RTO Restart (RTOR), allows the transport to restart its retransmission timer using a smaller timeout duration, so that the effective retransmission timeout (RTO) becomes more aggressive in situations where fast retransmit cannot be used. This enables faster loss detection and recovery for connections that are short lived or application limited.

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  • 40.
    Hurtig, Per
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    MPTCP PathFinder: Datacenter Bandwidth Aggregation2014Conference paper (Refereed)
  • 41.
    Høiland-Jørgensen, Toke
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Hurtig, Per
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    The Good, the Bad and the WiFi: Modern AQMs in a residential setting2015In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 89, p. 90-106Article in journal (Refereed)
    Abstract [en]

    Several new active queue management (AQM) and hybrid AQM/fairness queueing algorithms have been proposed recently. They seek to ensure low queueing delay and high network goodput without requiring parameter tuning of the algorithms themselves. However, extensive experimental evaluations of these algorithms are still lacking. This paper evaluates a selection of bottleneck queue management schemes in a test-bed representative of residential Internet connections of both symmetrical and asymmetrical bandwidths as well as WiFi. Latency under load and the performance of VoIP and web traffic patterns are evaluated under steady state conditions. Furthermore, the impact of the algorithms on fairness between TCP flows with different RTTs, and also the transient behaviour of the algorithms at flow startup is examined. The results show that while the AQM algorithms can significantly improve steady state performance, they exacerbate TCP flow unfairness. In addition, the evaluated AQMs severely struggle to quickly control queueing latency at flow startup, which can lead to large latency spikes that hurt the perceived performance. The fairness queueing algorithms almost completely alleviate the algorithm performance problems, providing the best balance of low latency and high throughput in the tested scenarios. However, on WiFi the performance of all the tested algorithms is hampered by large amounts of queueing in lower layers of the network stack inducing significant latency outside of the algorithms’ control.

    Download full text (pdf)
    fulltext
  • 42.
    Kane, Bridget
    University of Dublin, Trinity College, Ireland.
    An Analysis of Multi-Disciplinary Medical Team Meeting Dynamics: An Investigation into Collaboration and Information Flow at Meetings and the Use of Information Communication Technology2010Book (Other academic)
  • 43.
    Kane, Bridget
    et al.
    University of Dublin, Trinity College, Ireland.
    Groth, Kristina
    Karolinska institutet.
    Randall, Dave
    Manchester university.
    Medical team meetings: utilising technology to enhance communication, collaboration and decision-making2011In: Behavior and Information Technology, ISSN 0144-929X, E-ISSN 1362-3001, Vol. 30, no 4, p. 437-442Article in journal (Other academic)
  • 44.
    Kane, Bridget
    et al.
    University of Dublin, Trinity College, Ireland.
    Luz, Saturnino
    University of Dublin, Trinity College, Ireland.
    Medical teamwork, collaboration and patient-centred care2015In: Journal of Behaviour and Information Technology, ISSN 0144-929X, Vol. 34, no 6, p. 543-547Article in journal (Other academic)
  • 45.
    Karlsson, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Transport-Layer Performance in Wireless Multi-Hop Networks2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wireless communication has seen a tremendous growth in the last decades. Continuing on this trend, wireless multi-hop networks  are nowadays used or planned for use in a multitude of contexts, spanning from Internet access at home to emergency situations.

    The Transmission Control Protocol (TCP) provides reliable and ordered delivery of a data and is used by major Internet applications such as web browsers, email clients and file transfer programs. TCP traffic is also the dominating traffic type on the Internet. However, TCP performs less than optimal in wireless multi-hop networks due to packet reordering, low link capacity, packet loss and variable delay.

    In this thesis, we develop novel proposals for enhancing the network and transport layer to improve TCP performance in wireless multi-hop networks. As initial studies, we experimentally evaluate the performance of different TCP variants, with and without mobile nodes. We further evaluate the impact of multi-path routing on TCP performance and propose packet aggregation combined with aggregation aware multi-path forwarding as a means to better utilize the available bandwidth. The last contribution is a novel extension to multi-path TCP to  enable single-homed hosts to fully utilize the network capacity.

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    2013_01_Karlsson
  • 46.
    Karlsson, Jonas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Di Stasi, Giovanni
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Avallone, Stefano
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    An Aggregation Aware Multi-path Forwarding Paradigm for Wireless Mesh Networks2011In: IEEE MASS 2011. Proceedings of the 8th IEEE International Conference on Mobile Ad-hoc and Sensor Systems, IEEE Computer Society, 2011, p. 765-770Conference paper (Refereed)
    Abstract [en]

    In multi-radio wireless mesh networks, a networkdevice simultaneously transmits packets over different channelsby using multiple radios. Such frequency diversity not only increasesthroughput but makes multi-path routing approaches extremelyinteresting. This is because the channel diversity reducesthe risk for intra- and inter-flow interference. A fundamentalproblem to solve is the forwarding strategy which determineswhich packets to be sent over what multi-path segments atany given time. Ideally, the forwarding strategy should scheduleflows according to the capacity constraints imposed by thechannel assignment. However, the possibility to improve MAClayer efficiency by aggregating small packets into larger onesis reduced when packets are forwarded to different next-hops.In this paper, we develop a novel packet forwarding strategyfor multi-radio mesh networks that combines the benefits ofmulti-path routing with packet aggregation. In our cross-layerapproach, we effectively trade-off aggregation opportunities withchannel diversity. Simulation results show that our approach canimprove network throughput and delay by up to 15 percentand 25 percent, respectively, compared with aggregation unawareforwarding strategies.

    Download full text (pdf)
    meshtec2011
  • 47.
    Karlsson, Jonas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Di Stasi, Giovanni
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Avallone, Stefano
    Computer Science Department, University “Federico II” of Naples, Via Claudio 21, 80125 Naples, Italy.
    An Aggregation Aware Multi-path Forwarding Paradigm for Wireless Mesh Networks : AA-L2R Aggregation Aware Multi-path Routing2011Conference paper (Refereed)
  • 48.
    Karlsson, Jonas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Dimitrov, Velizar G.
    Department of Communication Networks, Technical University of Sofia, boulevard Kliment Ohridski 8, Sofia, Bulgaria.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Nilsson, Jan
    Swedish Defence Research Agency (FOI), Box 1165, SE - 581 11 Linköping, Sweden.
    Hansson, Anders
    Swedish Defence Research Agency (FOI), Box 1165, SE - 581 11 Linköping, Sweden.
    Performance Evaluation for TCP in Tactical Mobile Ad hoc Networks2012In: Proceedings of International Conference on Wireless Information Networks and Systems, SciTePress, 2012, p. 277-282Conference paper (Refereed)
    Abstract [en]

    Tactical networks are used in military and rescue operations to provide timely and accurate information to operating teams.  Tactical networks have traditionally used long distance narrow band radio links. However, although these links provide robust real-time communication the limited bandwidth makes them less suited for high data-rate applications.  To support high-data rate TCP applications such as providing digital images and maps, emerging tactical networks use shorter range but higher data-rate wide band radio links and multi-hop.  Due to the requirement of cheap up-front cost, most MANET research has focused on Carrier Sense Multiple Access (CSMA) networks. However, in tactical networks, where bounded delays are important, Time Division Multiple Access (TDMA) can give better possibility to support the Quality of Service needed for real-time communication.  The purpose of this paper is to assess and compare the throughput of three state-of-the-art TCP versions and two routing protocols over TDMA based MANETs.

  • 49.
    Karlsson, Jonas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    MPTCP PathFinder - finding your ways to aggregated bandwidth2012Report (Other academic)
    Abstract [en]

    Many  networks are multi-path; mobile devices have multiple interfaces, data centers have redundant paths and ISPs forward traffic over disjoint paths to perform load-balancing. Multi-path TCP (MPTCP) is a new mechanism that transparently divides a TCP connection into subflows and distributes them over a host's network interfaces. While this enables multi-homed systems like e.g. smartphones to use several interfaces and thus different, and mostly disjoint, network paths for a single transmission, most end-systems are still single-homed. With one interface, standard MPTCP creates only a single subflow, making single-homed systems unable to benefit from MPTCP's functionality. In this paper we propose PathFinder, an MPTCP extension that tries to estimate the number of subflows required to fully utilize  the network capacity, enabling single-homed hosts to reap the benefits of MPTCP. We evaluate MPTCP with PathFinder and compare its performance to standard MPTCP. The evaluation shows that PathFinder is able to open a limited but sufficient amount of subflows to significantly increase the throughput when compared to using standard MPTCP.

    Download full text (pdf)
    fulltext
  • 50.
    Karlsson, Jonas
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    di Stasi, Giovanni
    University of Naples "Federico II", Italy.
    Impact of Multi-path Routing on TCP Performance2012In: 2012 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM 2012), Washington, DC: IEEE Press, 2012, p. 1-3Conference paper (Refereed)
    Abstract [en]

    Routing packets over multiple disjoint paths towards a destination can increase network utilization by load-balancing the traffic over the network. The drawback of load-balancing is that different paths might have different delay properties, causing packets to be reordered. This can reduce TCP performance significantly, as reordering is interpreted as a sign of congestion. Packet reordering can be avoided by letting the network layer route strictly on flow-level. This will, however, also limit the ability to achieve optimal network throughput. There are also several proposals that try to mitigate the effects of reordering at the transport layer. In this paper, we perform an initial evaluation of such TCP reordering mitigations in multi-radio multi-channel wireless mesh networks when using multi-path routing. We evaluate two TCP reordering mitigation techniques implemented in the Linux kernel. The transport layer mitigations are compared using different multi-path routing strategies. Our findings show that, in general, flow-level routing gives the best TCP performance and that transport layer reordering mitigations only marginally can improve performance.

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