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  • 1.
    Abarghouyi, Hadis
    et al.
    IUST, Iran; MTNi Co, Iran.
    Razavizadeh, S. Mohammad
    IUST, Iran.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    QoE-Aware Beamforming Design for Massive MIMO Heterogeneous Networks2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 9, p. 8315-8323Article in journal (Refereed)
    Abstract [en]

    One of the main goals of the future wireless networks is improving the users quality of experience (QoE). In this paper, we consider the problem of the QoE-based resource allocation in the downlink of a massive multiple-input multiple-output heterogeneous network. The network consists of a macrocell with a number of small cells embedded in it. The small cells base stations (BSs) are equipped with a few antennas, while the macro BS is equipped with a massive number of antennas. We consider the two services Video and Web Browsing and design the beamforming vectors at the BSs. The objective is to maximize the aggregated mean opinion score (MOS) of the users under constraints on the BSs powers and the required quality of service of the users. We also consider extra constraints on the QoE of users to more strongly enforce the QoE in the beamforming design. To reduce the complexity of the optimization problem, we suggest suboptimal and computationally efficient solutions. Our results illustrate that increasing the number of antennas at the BSs and also increasing the number of small cells antennas in the network leads to a higher user satisfaction.

  • 2.
    Abd-Elmagid, Mohamed A.
    et al.
    Virginia Tech, VA 24061 USA.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Dhillon, Arpreet S.
    Virginia Tech, VA 24061 USA.
    On the Role of Age of Information in the Internet of Things2019In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 57, no 12, p. 72-77Article in journal (Refereed)
    Abstract [en]

    In this article, we provide an accessible introduction to the emerging idea of Age of Information (AoI) that quantifies freshness of information and explore its possible role in the efficient design of freshness-aware Internet of Things (IoT). We start by summarizing the concept of AoI and its variants with emphasis on the differences between AoI and other well-known performance metrics in the literature, such as throughput and delay. Building on this, we explore freshness-aware IoT design for a network in which IoT devices sense potentially different physical processes and are supposed to frequently update the status of these processes at a destination node (e.g., a cellular base station). Inspired by recent interest, we also assume that these IoT devices are powered by wireless energy transfer by the destination node. For this setting, we investigate the optimal sampling policy that jointly optimizes wireless energy transfer and scheduling of update packet transmissions from IoT devices with the goal of minimizing long-term weighted sum-AoI. Using this, we characterize the achievable AoI region. We also compare this AoI-optimal policy with the one that maximizes average throughput (throughput-optimal policy), and demonstrate the impact of system state on their structures. Several promising directions for future research are also presented.

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  • 3.
    Abdul Aziz Hasan Ali, Aamir
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Shahzad, Muhammad Adil
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A Joint Subcarrier/Power allocation Scheme for OFDMA-based Cellular Networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The assignment of this master thesis consists of initiating power, subcarrier allocation in a dynamic FFR based scheme designed for multi-cell OFDMA networks and to enhance the throughput of all center users in bandwidth hungry borrower cells (overloaded cells) which was previously degraded by original FFR3 scheme as a result of partitioning of system bandwidth into center and edge bands respectively. The method uses band borrowing to compensate center user’s throughput loss in a semi and fully overloaded system. The scheme uses dynamic programming method (0/1 knapsack problem) to bargain an edge band on various power levels and tends to check the best combination (power and sub-carrier) which the system can utilize while still maintaining acceptable throughput loss for the users at the edge of the neighboring cell (lender cell).

    The algorithm consists of generating a borrowing request to neighboring cells for utilizing their edge bands by the overloaded borrower cell if their average center user throughput reaches below a minimum threshold value set in the system. The borrowing method uses 0/1 knapsack problem to capture an edge band based on limiting factors of total cost in average throughput losses by neighbors (Ci) and Un (tolerable mean user edge user throughput loss by lending cell). While solving knapsack problem the lender (neighbors) will check Ci and Un before granting the right to use its edge band. The later stage requires reducing subcarrier power level in order to utilize the lenders edge band using "soft borrower" mode. The borrowed sub-carriers will be activated take power from the original center band sub-carriers of the overloaded cell by taking into account the interference between the lender and the borrower. In case of negative (0) reply from the lender cell after the first request, multiple requests are generated at reduce power level at every step to order to acquire more bands. If a neighbor has band borrowing requests from multiple overloaded base stations, the band will be granted to the one which gives minimal loss in terms of throughput to the lender cell.

    The simulation results are analyzed w.r.t reuse-1 and FFR3 scheme of a multi cell regular and irregular scenarios comprising of lightly to heavily overloaded cells with various subcarrier allocation patterns. An overhead and time assessment is also presented between borrower and lender cells. Simulation results show an increase of 60% in center user’s throughput w.r.t original FFR3 scheme with an acceptable loss of 18% at the edges in complex overloaded scenarios while the overall system throughout increases by 35%.

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  • 4.
    Abrahamsson, Olle
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Danev, Danyo
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Structural Balance Considerations for Networks with Preference Orders as Node Attributes2022In: 2022 56TH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS, AND COMPUTERS, IEEE , 2022, p. 1255-1261Conference paper (Refereed)
    Abstract [en]

    We discuss possible definitions of structural balance conditions in a network with preference orderings as node attributes. The main result is that for the case with three alternatives (A, B, C) we reduce the (3!)(3) = 216 possible configurations of triangles to 10 equivalence classes, and use these as measures of balance of a triangle towards possible extensions of structural balance theory. Moreover, we derive a general formula for the number of equivalent classes for preferences on n alternatives. Finally, we analyze a real-world data set and compare its empirical distribution of triangle equivalence classes to a null hypothesis in which preferences are randomly assigned to the nodes.

  • 5.
    Ahlström, Christer
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Swedish Natl Rd & Transport Res Inst, S-58195 Linkoping, Sweden.
    Diederichs, Frederik
    Fraunhofer Inst Optron, Germany.
    Teichmann, Daniel
    Univ Southern Denmark, Denmark; MIT, MA 02139 USA.
    Technologies for Risk Mitigation and Support of Impaired Drivers2022In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 23, no 5, p. 4736-4738Article in journal (Other academic)
    Abstract [en]

    This editorial serves as an extended introduction to the Special Issue on Technologies for Risk Mitigation and Support of Impaired Drivers. It gives the context to recent advances in assisted and automated driving and the new challenges that arise when modern technology meets human users. The Special Issue focuses on the development of robust sensors and detection algorithms for driver state monitoring of fatigue, stress, and inattention, and on the development of personalized multimodal, user-oriented, and adaptive information, warning, actuation, and handover strategies. A summary of more recent developments serves as a motivation for each article that follows.

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  • 6.
    Ahmad, Ijaz
    et al.
    University of Oulu, Finland.
    Kumar, Tanesh
    University of Oulu, Finland.
    Liyanage, Madhusanka
    University of Oulu, Finland.
    Okwuibe, Jude
    University of Oulu, Finland.
    Ylianttila, Mika
    University of Oulu, Finland.
    Gurtov, Andrei
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    5G Security: Analysis of Threats and Solutions2017In: 2017 IEEE CONFERENCE ON STANDARDS FOR COMMUNICATIONS AND NETWORKING (CSCN), IEEE , 2017, p. 193-199Conference paper (Refereed)
    Abstract [en]

    5G will provide broadband access everywhere, entertain higher user mobility, and enable connectivity of massive number of devices (e.g. Internet of Things (IoT)) in an ultrareliable and affordable way. The main technological enablers such as cloud computing, Software Defined Networking (SDN) and Network Function Virtualization (NFV) are maturing towards their use in 5G. However, there are pressing security challenges in these technologies besides the growing concerns for user privacy. In this paper, we provide an overview of the security challenges in these technologies and the issues of privacy in 5G. Furthermore, we present security solutions to these challenges and future directions for secure 5G systems.

  • 7.
    Ahmad, Ijaz
    et al.
    Univ Oulu, Finland.
    Liyanage, Madhusanka
    Univ Oulu, Finland.
    Ylianttila, Mika
    Univ Oulu, Finland.
    Gurtov, Andrei
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Analysis of Deployment Challenges of Host Identity Protocol2017In: 2017 EUROPEAN CONFERENCE ON NETWORKS AND COMMUNICATIONS (EUCNC), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    Host Identity Protocol (HIP), a novel internetworking technology proposes separation of the identity-location roles of the Internet Protocol (IP). HIP has been successful from the technological perspectives for network security and mobility, however, it has very limited deployment. In this paper we assess HIP to find the reasons behind its limited deployment and highlight the challenges faced by HIP for its commercial use. We propose technological development and outline deployment strategies for the wide use of HIP. Furthermore, this paper investigates the use of HIP in Software Defined Networks (SDN) to evaluate its performance in new disruptive networking technologies. In a nutshell, this paper presents revealing challenges for the deployment of innovative networking protocols and a way ahead for successful and large scale deployment.

  • 8.
    Ahmed, Atheeq
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Human Detection Using Ultra Wideband Radar and Continuous Wave Radar2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A radar works by radiating electromagnetic energy and detecting the reflected signal returned from the target. The nature of the reflected signal provides information about the target’s distance or speed. In this thesis, we will be using a UWB radar and a CW radar to help detect the presence and rough location of trapped survivors by detecting their motions. Range is estimated in the UWB radar using clutter removal with SVD and for the dual frequency CW Radar using STFT and median filtering. The effect of the algorithm parameters on their performance was analyzed. The performance of the implemented algorithms with regards to small motion detection, distance estimation and penetration capability was analyzed. Both systems are certainly capable of human detection and tracking.

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  • 9.
    Ahmed, Zubair
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Design of Autonomous Low Power Sensor for Soil Moisture Measurement.2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Drought is the most severe disaster compared to other disasters in human civilization and their impacts are serious which can cause hungur, thrist, food shortages, loss of livestock directly effects the human life. The main objective of this project is to develop an early warning system (EWS) [3] for drought indices by using wireless sensor networks (WSNs) which is the only way forward for an on-site monitoring and validation of locally defined drought indices [3].The designed wireless sensor network (WSN) consisting of a sensor unit, a master unit and a sensor power management unit (PMU). The sensor unit measures the moisture of the soil and transmitt the measured data through ZigBee module to the master unit. A real time clock (RTC) is also used in the sensor unit which records the information of second, minute, hour, day, month of day and year about when or what time the measurement taken. The master unit consisting of a SD-card and Bluetooth module. SD-card is used to store measured data from other sensor units and it is possible to take out the reading of measured data from the master unit by accessing the SD-card via Bluetooth inside the master unit to a PC or a smartphone mobile.To manage the power in the sensor unit and to make sensor alive for several years, the power management unit (PMU) manages the power level between two energy storage buffers (i.e., a supercapacitor and a Li+ ion battery) for a sensor node.

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  • 10.
    Ahola, David
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Yin To, Jie
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    To be entered/Green Cargo2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Schemakonstruktion för järnvägspersonal är en stor utmaning. En orsak är att arbetsuppgifterna vid järnvägen kräver olika kunskaps- och kompetenskrav, samt att det finns många arbetsregler som utgör restriktioner för schemakonstruktionen. I detta examensarbete har en fallstudie utförts för datorstödd schemakonstruktion för personalbemanning. Examensarbetet har utförts vid avdelningen för bemanningsplanering som ansvarar för planering av personal vid två av Green Cargos olika bangårdar. Huvudsyftet med det här examensarbetet är att utreda skillnaderna i scheman som skapats manuellt respektive automatiskt med hjälp av programvaran BP. Schemajämförelserna ska också redovisa nyttan av det automatiska planeringssättet där det finns applicerat. Under arbetet genomfördes litteraturstudier samt en fallstudie. I fallstudien genomfördes testkörningar med olika schemakonstruktionsmetoder på två bangårdar. Det numeriska resultatet visar att den datorassisterade bemanningsmetoden innebär en förbättrad bemanningsplanering ur företagets synvinkel då produktionsbehovet kan täckas utan ökade kostnader. Detta innebär också en ökad flexibilitet i produktionsplaneringen då tjänstgöringsturer enkelt kan ändras. Det gör det också mycket enklare att tilldela personal olika arbetsuppgifter som de har kompetens för. Den optimeringsbaserade bemanningsplanen innebär inte en ökad arbetsbelastning för medarbetaren. Trots att fler bangårdstjänster kan bemannas genom att använda den datorassisterade metoden visar det sig att den totala utlagda arbetstiden inte alls ökar eller att den bara ökar marginellt för vissa medarbetare. När planering sker med programvaran styrs denna av parametrar som är lätta att ändra. Dessa inställningar av parametrar är avgörande för utseendet på schemat. Indata kan vara fridagsplanering, kompetenstillgång och produktionsbehov. De i sin tur avgör i betydande grad på hur balansen mellan livs- och ekonomiska kvalitetsmåtten ser ut för medarbetarna.

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  • 11.
    Aijaz, Adnan
    et al.
    Toshiba Europe Ltd, England.
    Dawy, Zaher
    Amer Univ Beirut, Lebanon.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Simsek, Meryem
    Int Comp Sci Inst Berkeley, CA USA.
    Oteafy, Sharief
    Depaul Univ, IL 60604 USA.
    Holland, Oliver
    Adv Wireless Technol Grp Ltd, England.
    The IEEE P1918.1 Reference Architecture Framework for the Tactile Internet and a Case Study2020In: 2020 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), IEEE , 2020Conference paper (Refereed)
    Abstract [en]

    The term Tactile Internet broadly refers to a communication network that is capable of delivering control, touch, and sensing/actuation information in real-time. The Tactile Internet is currently a topic of interest for various standardization bodies. The emerging IEEE P1918.1 standards working group is focusing on defining a framework for the Tactile Internet. The main objective of this work is to present the IEEE P1918.1 reference architecture framework for the Tactile Internet. The paper provides an in-depth survey of various architectural aspects including the key entities, the interfaces, the functional capabilities, and the protocol stack. A case study has been presented as a manifestation of the architecture. Performance evaluation demonstrates the impact of functional capabilities and the underlying enablers on user-level utility pertaining to a generic Tactile Internet application.

  • 12.
    Alarcon, Alvaro
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Xavier, Guilherme B.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    A few-mode fiber Mach-Zehnder interferometer for quantum communication applications2020In: Frontiers in Optics / Laser Science / [ed] B. Lee, C. Mazzali, K. Corwin, and R. Jason Jones, Optical Society of America, 2020, article id LM1F.6Conference paper (Refereed)
    Abstract [en]

    We show that telecom few-mode fiber Mach-Zehnder interferometers can be used for quantum communication protocols where the LP01 and LP11a modes are employed to encode spatial qubits.

  • 13. Order onlineBuy this publication >>
    Alarcón Cuevas, Alvaro
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    A Few-Mode-Fiber Platform for Quantum Communication Applications2022Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Society as we know it today would not have been possible without the explosive and astonishing development of telecommunications systems, and optical fibers have been one of the pillars of these technologies.

    Despite the enormous amount of data being transmitted over optical networks today, the trend is that the demand for higher bandwidths will also increase. Given this context, a central element in the design of telecommunications networks will be data security, since information can often be confidential or private.

    Quantum information emerges as a solution to encrypt data by quantum key distribution (QKD) between two users. This technique uses the properties of nature as the fundamentals of operation rather than relying on mathematical constructs to provide data protection. A popular alternative to performing QKD is to use the relative phase between two individual photon paths for information encoding. However, this method was not practical over long distances. The time-bin- based scheme was a solution to the previous problem given its practical nature, however, it introduces intrinsic losses due to its design, which increases with the dimension of the encoded quantum system.

    In this thesis we have designed and tested a fiber-optic platform using spatial-division- multiplexing techniques. The use of few-mode fibers and photonic lanterns are the cornerstone of our proposal, which also allow us to support orbital angular momentum (OAM) modes. The platform builds on the core ideas of the phase-coded quantum communication system and also takes advantage of the benefits proposed by the time-bin scheme. We have experimentally tested our proposal by successfully transmitting phase-coded single-photon states over 500 m few-mode fiber, demonstrating the feasibility of our scheme. We demonstrated the successful creation of OAM states, their propagation and their successful detection in an all in-fiber scheme. Our platform eliminates the post-selection losses of time-bin quantum communication systems and ensures compatibility with next-generation optical networks and opens up new possibilities for quantum communication.

    List of papers
    1. A few-mode fiber Mach-Zehnder interferometer for quantum communication applications
    Open this publication in new window or tab >>A few-mode fiber Mach-Zehnder interferometer for quantum communication applications
    2020 (English)In: Frontiers in Optics / Laser Science / [ed] B. Lee, C. Mazzali, K. Corwin, and R. Jason Jones, Optical Society of America, 2020, article id LM1F.6Conference paper, Published paper (Refereed)
    Abstract [en]

    We show that telecom few-mode fiber Mach-Zehnder interferometers can be used for quantum communication protocols where the LP01 and LP11a modes are employed to encode spatial qubits.

    Place, publisher, year, edition, pages
    Optical Society of America, 2020
    Series
    OSA Technical Digest
    Keywords
    Few mode fibers, Quantum communications, Quantum key distribution, Single mode fibers, Space division multiplexing, Step index fibers
    National Category
    Atom and Molecular Physics and Optics Communication Systems
    Identifiers
    urn:nbn:se:liu:diva-184461 (URN)10.1364/LS.2020.LM1F.6 (DOI)9781943580804 (ISBN)
    Conference
    Laser Science 2020, Washington, DC, United States, 14–17 September 2020
    Note

    Funding: The authors acknowledge support from Ceniit Linköping University, the Swedish Research Council (VR 2017-04470), the Knut and Alice Wallenberg Foundation through the Wallenberg Center for Quantum Technology (WACQT) and by the QuantERA grant SECRET (VR grant no. 2019-00392).

    Available from: 2022-04-22 Created: 2022-04-22 Last updated: 2024-01-10Bibliographically approved
    2. Creating Spatial States of Light for Quantum Information with Photonic Lanterns
    Open this publication in new window or tab >>Creating Spatial States of Light for Quantum Information with Photonic Lanterns
    2021 (English)In: Applied Industrial Optics 2021 / [ed] G. Miller, A. Smith, I. Capraro, and J. Majors, Optical Society of America, 2021, article id W2A.2Conference paper, Published paper (Refereed)
    Abstract [en]

    We demonstrate an all-fiber platform for the generation and detection of spatial photonic states where combinations of LP01, LP11a and LP11b modes are used. This scheme can be employed for quantum communication applications.

    Place, publisher, year, edition, pages
    Optical Society of America, 2021
    Series
    OSA Technical Digest
    Keywords
    Few mode fibers, Quantum communications, Quantum cryptography, Quantum information, Space division multiplexing, Spatial light modulators
    National Category
    Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:liu:diva-184462 (URN)10.1364/AIO.2021.W2A.2 (DOI)9781943580934 (ISBN)
    Conference
    Applied Industrial Optics: Spectroscopy, Imaging and Metrology 2021, Washington, DC, United States, 26–28 July 2021
    Available from: 2022-04-22 Created: 2022-04-22 Last updated: 2024-01-10Bibliographically approved
    3. Few-Mode-Fiber Technology Fine-tunes Losses in Quantum Communication Systems
    Open this publication in new window or tab >>Few-Mode-Fiber Technology Fine-tunes Losses in Quantum Communication Systems
    2021 (English)In: Physical Review Applied, E-ISSN 2331-7019, Vol. 16, no 3, article id 034018Article in journal (Refereed) Published
    Abstract [en]

    A natural choice for quantum communication is to use the relative phase between two paths of a single photon for information encoding. This method was nevertheless quickly identified as impractical over long distances, and thus a modification based on single-photon time bins has become widely adopted. It, how-ever, introduces a fundamental loss, which increases with the dimension and limits its application over long distances. Here solve this long-standing hurdle by using a few-mode-fiber space-division-multiplexing platform working with orbital-angular-momentum modes. In our scheme, we maintain the practicability provided by the time-bin scheme, while the quantum states are transmitted through a few-mode fiber in a configuration that does not introduce postselection losses. We experimentally demonstrate our proposal by successfully transmitting phase-encoded single-photon states for quantum cryptography over 500 m of few-mode fiber, showing the feasibility of our scheme.

    Place, publisher, year, edition, pages
    AMER PHYSICAL SOC, 2021
    National Category
    Other Physics Topics
    Identifiers
    urn:nbn:se:liu:diva-179872 (URN)10.1103/PhysRevApplied.16.034018 (DOI)000698660300003 ()
    Note

    Funding Agencies|Ceniit Linkoping University; Swedish Research CouncilSwedish Research CouncilEuropean Commission [2017-04470]; QuantERA SECRET [2019-00392]; Knut and Alice Wallenberg Foundation through the Wallenberg Center for Quantum Technology; Fondo Nacional de Desarrollo Cientifico y TecnologicoComision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)CONICYT FONDECYT [1200859]; ANID Millennium Science Initiative program [ICN17_012]

    Available from: 2021-10-06 Created: 2021-10-06 Last updated: 2024-01-10
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  • 14.
    Alesand, Elias
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Identification of Flying Drones in Mobile Networks using Machine Learning2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Drone usage is increasing, both in recreational use and in the industry. With it comes a number of problems to tackle. Primarily, there are certain areas in which flying drones pose a security threat, e.g., around airports or other no-fly zones. Other problems can appear when there are drones in mobile networks which can cause interference. Such interference comes from the fact that radio transmissions emitted from drones can travel more freely than those from regular UEs (User Equipment) on the ground since there are few obstructions in the air. Additionally, the data traffic sent from drones is often high volume in the form of video streams. The goal of this thesis is to identify so-called "rogue drones" connected to an LTE network. Rogue drones are flying drones that appear to be regular UEs in the network. Drone identification is a binary classification problem where UEs in a network are classified as either a drone or a regular UE and this thesis proposes machine learning methods that can be used to solve it. Classifications are based on radio measurements and statistics reported by UEs in the network. The data for the work in this thesis is gathered through simulations of a heterogenous LTE network in an urban scenario. The primary idea of this thesis is to use a type of cascading classifier, meaning that classifications are made in a series of stages with increasingly complex models where only a subset of examples are passed forward to subsequent stages. The motivation for such a structure is to minimize the computational requirements at the entity making the classifications while still being complex enough to achieve high accuracy. The models explored in this thesis are two-stage cascading classifiers using decision trees and ensemble learning techniques. It is found that close to 60% of the UEs in the dataset can be classified without errors in the first of the two stages. The rest is forwarded to a more complex model which requires more data from the UEs and can achieve up to 98% accuracy. 

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    Alesand - Identification of Flying Drones in Mobile Networks using Machine Learning
  • 15.
    Ali, Rahman
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Design of Building Blocks in Digital Baseband Transceivers for Body-Coupled Communication2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Advances in communication technologies continue to increase information sharing among the people.~Short-range wireless networking technologies such as Bluetooth or ZigBee, which are mainly used for data transfer over short range, will, however, suffer from network congestion, high power consumption and security issues in the future.

    The body-coupled communication (BCC), a futuristic short-range wireless technology, uses the human body as a transmission medium. In BBC channel, a small electric field is induced onto the human body which enables the propagation of a signal between communication devices that are in the proximity or direct contact with the human body. The direct baseband transmission and simple architecture make BCC an attractive candidate for a future short-range wireless communication technology in particular applications such as body area network.

    The main focus of this thesis is on the design and implementation of digital baseband transmitter and receiver for the body-coupled communication. The physical layer (PHY) implementation of the digital baseband transmitter and receiver is inspired from the IEEE 802.3 Ethernet transmission protocol. The digital design is implemented at RTL level using hardware description language (VHDL). The functionality of the digital baseband transmitter and receiver is demonstrated by developing data transfer application layers.

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  • 16.
    Allander, Martin
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Channel Equalization Using Machine Learning for Underwater Acoustic Communications2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wireless underwater acoustic (UWA) communications is a developing field with various applications. The underwater acoustic communication channel is very special and its behavior is environment-dependent. The UWA channel is characterized by low available bandwidth, and severe motion-introduced Doppler effect compared to wireless radio communication. Recent literature suggests that machine learning (ML)-based channel estimation and equalization offer benefits over traditional techniques (a decision feedback equalizer), in UWA communications. ML can be advantageous due to the difficultly in designing algorithms for UWA communication, as finding general channel models have proven to be difficult. This study aims to explore if ML-based channel estimation and equalization as a part of a sophisticated physical layer structure can offer improved performance. In the study, supervised ML using a deep neural network and a recurrent neural network will be utilized to improve the bit error rate. A channel simulator with environment-specific input is used to study a wide range of channels. The simulations are utilized to study in which environments ML should be tested. It is shown that in highly time-varying channels, ML outperforms traditional techniques if trained with prior information of the channel. However, utilizing ML without prior information of the channel yielded no improvement of the performance.

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  • 17.
    Almquist, Mathias
    et al.
    Linköping University, Department of Computer and Information Science.
    Almquist, Viktor
    Linköping University, Department of Computer and Information Science.
    Analysis of 360° Video Viewing Behaviours2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    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. 

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  • 18.
    Almquist, Mathias
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Almquist, Viktor
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Vergara Alonso, Ekhiotz Jon
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Communication Energy Overhead of Mobiles Games2015In: MobiGames '15: Proceedings of the 2nd Workshop on Mobile Gaming, Association for Computing Machinery (ACM), 2015, p. 1-6Conference paper (Other academic)
    Abstract [en]

    Although a significant proportion of the mobile apps are games there has been little attention paid to their specific characteristics with respect to communication energy. In this paper we select 20 mobile games among the top 100 free Android games, and study their data patterns and communication energy use over a total of 25 hours of playing. The analysis of the energy for communication over 3G networks indicates that there is a wide variation among the games, the largest footprint being 8 times higher than the lowest one. The results also indicates both app-specific and category-specific relations between data pattern and energy use, as well as variations in CPU utilisation.

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  • 19.
    Almér, Louise
    Linköping University, Department of Electrical Engineering, Information Coding.
    Evaluation of the Perceived Speech Quality for G729D and Opus: With Different Network Scenarios and an Implemented VoIP Application2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Communication has always been a vital part of our society, and day-to-day communication is increasingly becoming more digital. VoIP (voice over IP) is used for real-time communication, and to be able to send the information over the internet must the speech be compressed to lower the number of bits needed for transmission. Codecs are used to compress the speech, or any other type of data transmitting over a network, which can introduce some noise if lossy compression is used. Depending on the bandwidth, bit rate, and codec used can distortion be minimized which would result in higher perceived speech quality.

    In the thesis, two codecs, G729D and Opus, were tested and evaluated with two different objective perceive speech quality metrics, POLQA and PESQ. The codecs were also tested with different emulated network scenarios, 2G, 3G, 4G, satellite two-hop, and LAN. Furthermore, Opus was tested with and without VAD (voice activity detection) to see how VAD could affect the perceived speech quality. The different network scenarios did not impact the results of the evaluation, since the main difference between the network scenarios was latency, which POLQA and PESQ do not consider in the evaluation. Opus achieved a higher MOS-LQO (mean opinion score listening quality objective) than G729D. However, when VAD was enabled with Opus for a low bit rate, 8 kbit/s, the MOS-LQO was lower than without VAD. 

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  • 20.
    Alodeh, Maha
    et al.
    Univ Luxembourg, Luxembourg.
    Spano, Danilo
    Univ Luxembourg, Luxembourg.
    Kalantari, Ashkan
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering. Univ Luxembourg, Luxembourg.
    Tsinos, Christos G.
    Univ Luxembourg, Luxembourg.
    Christopoulos, Dimitrios
    Newtec Satcom, Belgium.
    Chatzinotas, Symeon
    Univ Luxembourg, Luxembourg.
    Ottersten, Bjorn
    Univ Luxembourg, Luxembourg.
    Symbol-Level and Multicast Precoding for Multiuser Multiantenna Downlink: A State-of-the-Art, Classification, and Challenges2018In: IEEE Communications Surveys and Tutorials, E-ISSN 1553-877X, Vol. 20, no 3, p. 1733-1757Article in journal (Refereed)
    Abstract [en]

    Precoding has been conventionally considered as an effective means of mitigating or exploiting the interference in the multiantenna downlink channel, where multiple users are simultaneously served with independent information over the same channel resources. The early works in this area were focused on transmitting an individual information stream to each user by constructing weighted linear combinations of symbol blocks (codewords). However, more recent works have moved beyond this traditional view by: 1) transmitting distinct data streams to groups of users and 2) applying precoding on a symbol-persymbol basis. In this context, the current survey presents a unified view and classification of precoding techniques with respect to two main axes: 1) the switching rate of the precoding weights, leading to the classes of block-level and symbol-level precoding and 2) the number of users that each stream is addressed to, hence unicast, multicast, and broadcast precoding. Furthermore, the classified techniques are compared through representative numerical results to demonstrate their relative performance and uncover fundamental insights. Finally, a list of open theoretical problems and practical challenges are presented to inspire further research in this area.(1)

  • 21.
    Al-Salihi, Hayder
    et al.
    The Department of Informatics, King’s College London, UK.
    Van Chien, Trinh
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Le, Tuan Anh
    The Department of Design Engineering and Mathematics, Middlesex University, London, UK.
    Nakhai, Mohammad Reza
    The Department of Informatics, King’s College London, London, UK.
    A Successive Optimization Approach to Pilot Design for Multi-Cell Massive MIMO Systems2018In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, no 5, p. 1086-1089Article in journal (Refereed)
    Abstract [en]

    In this letter, we introduce a novel pilot designapproach that minimizes the total mean square errors of theminimum mean square error estimators of all base stations (BSs)subject to the transmit power constraints of individual users inthe network, while tackling the pilot contamination in multicellmassive MIMO systems. First, we decompose the originalnon-convex problem into distributed optimization sub-problemsat individual BSs, where each BS can optimize its own pilotsignals given the knowledge of pilot signals from the remainingBSs. We then introduce a successive optimization approach totransform each optimization sub-problem into a linear matrixinequality form, which is convex and can be solved by availableoptimization packages. Simulation results confirm the fast convergenceof the proposed approach and prevails a benchmarkscheme in terms of providing higher accuracy.

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  • 22.
    Anchora, Luca
    et al.
    IMT of Lucca.
    Badia, Leonardo
    Università degli Studi di Padova.
    Karipidis, Eleftherios
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Zorzi, Mikele
    Università degli Studi di Padova.
    Capacity Gains due to Orthogonal Spectrum Sharing in Multi-Operator LTE Cellular Networks2012In: Proceedings of the Ninth International Symposium on Wireless Communication Systems (ISWCS), 2012, p. 286-290Conference paper (Refereed)
    Abstract [en]

    Static spectrum allocation leads to resource wastage and inter-operator spectrum sharing is a possible way to improve spectrum efficiency. In this work, we assume that two cellular network operators agree upon sharing part of their spectrum, which can then be dynamically accessed by either of them in a mutually exclusive way. Our goal is to numerically assess the gain, in terms of cell capacity, due to such orthogonal spectrum sharing. Hence, we propose a centralized algorithm that performs coordinated scheduling, in order to numerically evaluate an upper bound on the achievable sum capacity. The algorithm is centralized and exploits complete information on both networks to perform the optimum allocation. The simulation results illustrate the impact of the multiuser diversity and the asymmetry in the traffic load among the networks on the overall achievable gain.

  • 23.
    Anchora, Luca
    et al.
    IMT of Lucca.
    Badia, Leonardo
    Università degli Studi di Padova.
    Zhang, Haibin
    TNO ICT.
    Fahldieck, Torsten
    Bell Labs, Alcatel-Lucent.
    Zhang, Jianshu
    Ilmenau University of Technology.
    Szydelko, Michal
    Wroclaw Research Centre EIT+ .
    Schubert, Martin
    Fraunhofer Institute for Telecommunications HHI.
    Karipidis, Eleftherios
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Haardt, Martin
    Ilmenau University of Technology.
    Resource Allocation and Management in Multi-Operator Cellular Networks with Shared Physical Resources2012In: Proceedings of the Ninth International Symposium on Wireless Communication Systems (ISWCS), IEEE , 2012, p. 296-300Conference paper (Refereed)
    Abstract [en]

    In this paper, we focus on next-generation cellular networks and discuss physical resources sharing among the operators. This implies cooperative usage of the available radio frequencies and also infrastructure sharing. In particular, we analyze the spectrum sharing gain achievable at different time scales and the main factors impacting on it. Then, we move towards a wider idea of resource sharing and consider a joint spectrum and infrastructure sharing (full sharing). We describe a two-layer resource management architecture that enables operators to reduce costs while still guaranteeing a good service level. The main findings of our investigations are to quantify the effectiveness of resource sharing and open up new perspectives for the operators of next-generation networks.

  • 24.
    Andersson, Martin
    Linköping University, Department of Electrical Engineering, Information Coding.
    Parametric Prediction Model for Perceived Voice Quality in Secure VoIP2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    More and more sensitive information is communicated digitally and with thatcomes the demand for security and privacy on the services being used. An accurateQoS metric for these services are of interest both for the customer and theservice provider. This thesis has investigated the impact of different parameterson the perceived voice quality for encrypted VoIP using a PESQ score as referencevalue. Based on this investigation a parametric prediction model has been developedwhich outputs a R-value, comparable to that of the widely used E-modelfrom ITU. This thesis can further be seen as a template for how to construct modelsof other equipments or codecs than those evaluated here since they effect theresult but are hard to parametrise.

    The results of the investigation are consistent with previous studies regarding theimpact of packet loss, the impact of jitter is shown to be significant over 40 ms.The results from three different packetizers are presented which illustrates theneed to take such aspects into consideration when constructing a model to predictvoice quality. The model derived from the investigation performs well withno mean error and a standard deviation of the error of a mere 1:45 R-value unitswhen validated in conditions to be expected in GSM networks. When validatedagainst an emulated 3G network the standard deviation is even lower.v

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  • 25.
    Anemyr, Mattias
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Optimization of Production Scheduling at IKEA Industry Hultsfred2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    IKEA Industry has factories in several locations where one location is in Hultsfred, Småland. IKEA Industry Hultsfred produces IKEA:s wardrobe collection PAX. In 2018, 2.8 million wardrobes were manufactured in Hultsfred. This thesis covers the subject of constructing and developing an optimization model which has the same characteristics as the plinth production at IKEA Industry Hultsfred. This means that the optimization model must consider production sequence; the setup time is different depending on which products that have been produced in the machine earlier. The thesis also covers to investigate how much time that is necessary to produce the plinths to Hultsfred, Portugal, and Germany under different circumstances. This thesis also balances inventory levels and setup time. I.e., how the inventory levels are changed if more emphasis is put into minimizing setup time, and the other way around. The results show that lower inventory levels and setup times are achievable over seven days if the production planning technique is changed.

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  • 26.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Avgouleas, Ioannis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Fitzgerald, Emma
    Lund University, Sweden.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD 20742 USA.
    Allocation of Heterogeneous Resources of an IoT Device to Flexible Services2016In: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 3, no 5, p. 691-700Article in journal (Refereed)
    Abstract [en]

    Internet-of-Things (IoT) devices can be equipped with multiple heterogeneous network interfaces. An overwhelmingly large amount of services may demand some or all of these interfaces available resources. Herein, we present a precise mathematical formulation of assigning services to interfaces with heterogeneous resources in one or more rounds. For reasonable instance sizes, the presented formulation produces optimal solutions for this computationally hard problem. We prove the NP-completeness of the problem and develop two algorithms to approximate the optimal solution for big instance sizes. The first algorithm allocates the most demanding service requirements first, considering the average cost of interfaces resources. The second one calculates the demanding resource shares and allocates the most demanding of them first by choosing randomly among equally demanding shares. Finally, we provide simulation results giving insight into services splitting over different interfaces for both cases.

  • 27.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Avgouleas, Ioannis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Flexible allocation of heterogeneous resources to services on an IoT device2015In: 2015 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 99-100Conference paper (Refereed)
    Abstract [en]

    In the Internet of Things (IoT), devices and gateways may be equipped with multiple, heterogeneous network interfaces which should be utilized by a large number of services. In this work, we model the problem of assigning services' resource demands to a device's heterogeneous interfaces and give a Mixed Integer Linear Program (MILP) formulation for it. For meaningful instance sizes the MILP model gives optimal solutions to the presented computationally-hard problem. We provide insightful results discussing the properties of the results on the properties of the derived solutions with respect to the splitting of services to different interfaces.

  • 28.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Efrat, Alon
    University of Arizona, AZ 85721 USA.
    Packer, Eli
    IBM Research Haifa, Israel.
    Polishchuk, Valentin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Sedov, Leonid
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    BBTM: New life for old ATM2016In: 2016 IEEE/AIAA 35TH DIGITAL AVIONICS SYSTEMS CONFERENCE (DASC), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    This paper investigates algorithmic questions related to the possibility of managing UAV traffic with beacon-based navigation, which we dub BBTM - Beacon-Based Traffic Management. The specific problem addressed is: How to install the minimum number of beacons in a mountainous terrain to ensure connectivity among a given set of UAS terminals on the terrain? BBTM is relevant for low-cost UAVs operating in remote areas not on time-critical missions, and may also be used as a backup system for better-equipped UAS in case the precise positioning or control information is lost, spoofed or jammed. We give algorithms for the beacon tower placement and evaluate their performance both on synthetic and real-world terrain data; the experiments suggest that our solutions can be used to efficiently quantify costs of establishing direct-visibility routing networks for UAS management.

  • 29.
    Arestrom, Erik
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Early Online Classification of Encrypted Traffic Streams using Multi-fractal Features2019In: IEEE CONFERENCE ON COMPUTER COMMUNICATIONS WORKSHOPS (IEEE INFOCOM 2019 WKSHPS), IEEE , 2019, p. 84-89Conference paper (Refereed)
    Abstract [en]

    Timely and accurate flow classification is important for identifying flows with different service requirements, optimized network management, and for helping network operators simultaneously operate networks at higher utilization while providing end users good quality of experience (QoE). With most services starting to use end-to-end encryption (HTTPS and QUIC), traditional Deep Packet Inspection (DPI) and port-based approaches are no longer applicable. Furthermore, most flow-level-based approaches ignore the complex non-linear characteristics of internet traffic (e.g., self similarity). To address this challenge, in this paper, we present and evaluate a classification framework that combines multi-fractal feature extraction based on time series data (which captures these non-linear characteristics), principal component analysis (PCA) based feature selection, and man-in-the-middle (MITM) based flow labeling. Our detailed evaluation shows that the method is able to quickly and effectively classify traffic belonging to the six most popular traffic types (video streaming, web browsing, social networking, audio communication, text communication, and bulk download) and to distinguish between video-on-demand (VoD) and live streaming sessions delivered from the same services. Our results show that good accuracy can be achieved with only information about the timing of the packets within a flow.

  • 30.
    Aria, Erfan
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Investigation of automated vehicle effects on driver’s behavior and traffic performance2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Advanced Driver Assistance Systems (ADAS) offer the possibility of helping drivers to fulfill their driving tasks. Automated vehicles are capable of communicating with surrounding vehicles (V2V) and infrastructure (V2I) in order to collect and provide essential information about driving environment. Studies have proved that automated vehicles have a potential to decrease traffic congestion on road networks by reducing the time headway, enhancing the traffic capacity and improving the safety margins in car following. Furthermore, vehicle movement and driver’s behavior of conventional vehicles will be affected by the presence of automated vehicles in traffic networks. Despite different encouraging factors, automated driving raises some concerns such as possible loss of situation awareness, overreliance on automation and degrading driving skills in absence of practice. Moreover, coping with complex scenarios, such as merging at ramps and overtaking, in terms of interaction between automated vehicles and conventional vehicles need more research. This thesis work aims to investigate the effects of automated vehicles on driver’s behavior and traffic performance. A broad literature review in the area of driving simulators and psychological studies was performed to examine the automated vehicle effects on driver’s behavior. Findings from the literature survey, which has been served as setup values in the simulation study of the current work, reveal that the conventional vehicles, which are driving close to the platoon of automated vehicles with short time headway, tend to reduce their time headway and spend more time under their critical time headway. Additionally, driving highly automated vehicles is tedious in a long run, reduce situation awareness and can intensify driver drowsiness, exclusively in light traffic. In order to investigate the influences of automated vehicles on traffic performance, a microscopic simulation case study consisting of different penetration rates of automated vehicles (0, 50 and 100 percentages) was conducted in VISSIM software. The scenario network is a three-lane autobahn segment of 2.9 kilometers including an off-ramp, on-ramp and a roundabout with some surrounding urban roads. Outputs of the microscopic simulation in this study reveal that the positive effects of automated vehicles on roads are especially highlighted when the network is crowded (e.g. peak hours). This can definitely count as a constructive point for the future of road networks with higher demands. In details, average density of autobahn segment remarkably decreased by 8.09% during p.m. peak hours in scenario with automated vehicles. Besides, Smoother traffic flow with less queue in the weaving segment was observed. Result of the scenario with 50% share of automated vehicles moreover shows a feasible interaction between conventional vehicles and automated vehicles. Meaningful outputs of this case study, based on the input data from literature review, demonstrate the capability of VISSIM software to simulate the presence of automated vehicles in great extent, not only as an automated vehicle scenario but also a share of them, in traffic network. The validity of the output values nonetheless needs future research work on urban and rural roads with different traffic conditions.

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  • 31.
    Arvanitaki, Antonia
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Mohapatra, Parthajit
    Indian Institute of Technology, Tirupati, India.
    Secrecy in Congestion-Aware Broadcast Channels2021In: Proc. Wireless Days Conference (WD) 2021, Institute of Electrical and Electronics Engineers (IEEE), 2021Conference paper (Refereed)
    Abstract [en]

    Congestion-aware scheduling in the case of traditional downlink cellular communication has neglected the heterogeneity in terms of secrecy among different clients. In this paper, we study a two-user congestion-aware broadcast channel with heterogeneous traffic and different security requirements. The traffic with security requirements is intended for a legitimate user and it has bursty nature. The incoming packets are stored in a queue at the source. Furthermore, there is a second traffic flow intended for another user, it is delay tolerant and does not have secrecy constraints. The receiver which needs to be served with confidential data has full-duplex capabilities, and it can send a jamming signal to hinder eavesdropping of its data at the other user. We consider two randomized policies for selecting which packets to transmit, one is congestion-aware by taking into consideration the queue size, whereas the other one is non-congestion-aware. We analyse the throughput and the delay performance under two decoding schemes at the receivers and provide insights into their relative security performance and into how congestion control at the queue holding confidential information can help decrease the average delay per packet. We show that the two policies have the same secrecy performance for large random access probabilities. The derived results also take account of the self-interference caused at the receiver for whom confidential data is intended due to its full-duplex operation while jamming the communication at the other user.

  • 32.
    Arvanitaki, Antonia
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Mohapatra, Parthajit
    Indian Inst Technol, India.
    Burdakov, Oleg
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Performance analysis of congestion-aware secure broadcast channels2021In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2021, no 1, article id 178Article in journal (Refereed)
    Abstract [en]

    Congestion-aware scheduling in case of downlink cellular communication has ignored the distribution of diverse content to different clients with heterogeneous secrecy requirements. Other possible application areas that encounter the preceding issue are secure offloading in mobile-edge computing, and vehicular communication. In this paper, we extend the work in Arvanitaki et al. (SN Comput Sci 1(1):53, 2019) by taking into consideration congestion and random access. Specifically, we study a two-user congestion-aware broadcast channel with heterogeneous traffic and different security requirements. We consider two randomized policies for selecting which packets to transmit, one is congestion-aware by taking into consideration the queue size, whereas the other one is congestion-agnostic. We analyse the throughput and the delay performance under two decoding schemes at the receivers, and provide insights into their relative security performance and into how congestion control at the queue holding confidential information can help decrease the average delay per packet. We show that the congestion-aware policy provides better delay, throughput, and secrecy performance for large arrival packet probabilities at the queue holding the confidential information. The derived results also take account of the self-interference caused at the receiver for whom confidential data is intended due to its full-duplex operation while jamming the communication at the other user. Finally, for two decoding schemes, we formulate our problems in terms of multi-objective optimization, which allows for finding a trade-off between the average packet delay for packets intended for the legitimate user and the throughput for the other user under congestion-aware policy.

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  • 33.
    Arvidsson, Simon
    et al.
    Linköping University, Department of Computer and Information Science.
    Ekblom, Tobias
    Linköping University, Department of Computer and Information Science.
    Marknadsplatsapplikation för Android2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Målet med examensarbetet är att utveckla en marknadsplatsapplikation för Android. Marknadsplatsapplikationen ska tillhandahålla funktioner för att ge användaren förutsättningar att hitta och ladda ner applikationer över Internet ifrån marknadsplatsens serversida. Marknadsplatsapplikationen kommer likt en tunn klient vara helt beroende av innehåll från en serversida. Vid examensarbetets utförande existerade dock ingen serversida då denna ännu inte var färdigutvecklad.

    För att utveckla marknadsplatsapplikationen utan närvaron av en serversida, implementerades en emulerad serversida som utåt sett hade funktionaliteten av en framtida serversida. En mjukvaruarkitektur implementerades bestående av tre lager: användargränsnitt (GUI), kärnfunktionalitet (Core) och webbkommunikation (WebCom). Syftet med arikitekturen var dels att begränsa inverkan av övergången från en emulerad serversida till en riktig serversida, och dels att avgränsa och avlasta användargränsnittet från tunga operationer för att därigenom uppnå god responsivitet.

    Marknadsplatsapplikationen implementerades med all funktionalitet som planerades. Arkitekturen med tydlig separation mellan GUI, Core ochWebCom, förväntas leda till en smidig övergång till en riktig serversida. Även ett tydligt öde för att hämta och skicka data mellan marknadsplatsapplikationen och serversida förväntas underlätta att implementera ny funktionalitet som är beroende av en serversida. Användargränsnittet uppvisar fortfarande brist på responsivitet. Arkitekturen med endast en asynkron klass GuiWorker, som hanterar exekveringen av tunga operationer på bakgrundstrådar, förväntas dock kunna uppnå ett responsivt användargränsnitt.

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  • 34.
    Aslam, Mohammed Zahid
    et al.
    Siradel.
    Corre, Yoann
    Siradel.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Lostanlen, Yves
    Siradel.
    Massive MIMO Channel Performance Analysis Considering Separation of Simultaneous Users2018Conference paper (Refereed)
    Abstract [en]

    One of the key aspects of massive MIMO (mMIMO) is its ability to spatially differentiate between multiple simultaneous users. The spatial separability improves as the number of base station (BS) antenna elements is increased. In real BS deployments, the number of BS array elements will be fixed, and expected to provide the required service to a certain number of simultaneous users in the existing propagation environment. The mMIMO performance is investigated in this paper, in an urban macro-cell scenario, using three kinds of channel models with different complexity levels: the independent and identically distributed Rayleigh fading model, a geometry-based stochastic model, and a physical ray-based software. Two performance indicators are analyzed: the favorable propagation metric and the multi-user eigenvalue distribution. Two frequencies (2 GHz and 28 GHz) and two antenna array shapes (linear and circular) are considered and compared.

  • 35.
    Aspnäs, Frida
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Eliminating Right-Turn-on-Red (RTOR) at Key Intersections in a City Core2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The City of Fredericton is the capital of New Brunswick, located in eastern Canada. Rightturn-on-red (RTOR) is a general practice at any traffic intersection in this maritime province. Many collisions between pedestrians and vehicles have been recorded at signalized intersections in the downtown area of the city. Due to the number of collisions, the City of Fredericton was interested in investigating how a restriction against RTOR could affect vehicular traffic. The purpose and goal of this project was to develop a calibrated traffic model of the downtown area of Fredericton that could be used for simulation studies. Two main changes were investigated: 1) a restriction against RTOR for each of eleven key intersections in the downtown area, and 2) a restriction against left-turns at one selected intersection. The traffic simulation model was also used for analyzing how factors such as pedestrian volumes, lane channelization, and turning proportions affect the changes in traffic conditions due to permitting, or prohibiting, right-turn-on-red.

    The traffic simulation model was created in the TSIS/CORSIM software. Several different scenarios were generated for analysis. The results of the simulation show that the traffic conditions in the whole downtown area will be affected when introducing a restriction against RTOR. Certain intersections show a relatively high change while others show no significant change at all. Several different factors were seen to affect the number of RTOR that could be performed at an intersection. One main factor was lane channelization. With a shared lane, the proportion of right-turning vehicles at the intersection was found to highly affect how many RTOR can be performed. Pedestrian volumes prove to be a third factor affecting the number of RTOR at an intersection.

    Overall results demonstrate that there are only a few intersections where it is suitable for the City of Fredericton to implement a restriction against RTOR.

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  • 36.
    Avazkonandeh Gharavol, Ebrahim
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Robust Joint Optimization of MIMO Interfering Relay Channels with Imperfect CSI2011In: 2001 4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP), Piscataway, NJ, USA: IEEE , 2011, , p. 5p. 209-212Conference paper (Refereed)
    Abstract [en]

    In this paper we deal with the problem of the joint optimization of the precoders, equalizers and relay beamformer of a multiple-input multiple-output interfering relay channel. This network can be regarded az a generalized model for both one-way and two-way relay channels with/without direct interfering links. Unlike the conventional design procedures, we assume that the Channel State Information (CSI) is not known perfectly. The imperfect CSI is described using the norm bounded error framework. We use a system-wide Sum Mean Square Error (SMSE) based problem formulation which is constrained using the transmit power of the terminals and the relay node. The problem at hand, from a worst-case design perspective, is a multilinear, and hence, a nonconvex problem which is also semiinfinite in its constraints. We use a generalized version of the Peterson’s lemma to handle the semi-infiniteness and reduce the original problem to a single Linear Matrix Inequality (LMI). However, this LMI is not convex, and to resolve this issue we propose an iterative algorithm based on the alternating convex search methodology to solve the aforementioned problem. Finally simulation results, i.e., the convergence of the proposed algorithm and the SMSE properties, are included to asses the performance of the proposed algorithm.

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  • 37.
    Avazkonandeh Gharavol, Ebrahim
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Robust Joint Optimization of Non-regenerative MIMO Relay Channels with Imperfect CSI2011In: Conference Record of the Forty Fifth Asilomar Conference on Signals, Systems and Computers (ASILOMAR), 2011, IEEE Computer Society, 2011, p. 1589-1593Conference paper (Refereed)
    Abstract [en]

    In this paper, we deal with the problem of joint optimization of the source precoder, the relay beamformer and the destination equalizer in a nonregenerative relay network with only a partial knowledge of the Channel State Information (CSI).

    We model the partial CSI using a deterministic norm bounded error model, and we use a system-wide mean square error performance measure which is constrained based on the transmit power regulations for both source and relay nodes.

    Most conventional designs employ the average performance optimization, however, we solve this problem from a worst-case design perspective.

    The original problem formulation is a semi-infinite trilinear optimization problem which is not convex.

    To solve this problem we extend the existing theories to deal with the constraints which are semi-infinite in different independent complex matrix variables.

    We show that the equivalent approximate problem is a set of linear matrix inequalities, that can be solved iteratively.

    Finally simulation results assess the performance of the proposed scheme.

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  • 38.
    Avazkonandeh Gharavol, Ebrahim
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    The Sign-Definiteness Lemma and Its Applications to Robust Transceiver Optimization for Multiuser MIMO Systems2013In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 61, no 2, p. 238-252Article in journal (Refereed)
    Abstract [en]

    We formally generalize the sign-definiteness lemma to the case of complex-valued matrices and multiple norm-bounded uncertainties. This lemma has found many applications in the study of the stability of control systems, and in the design and optimization of robust transceivers in communications. We then present three different novel applications of this lemma in the area of multi-user multiple-input multiple-output (MIMO) robust transceiver optimization. Specifically, the scenarios of interest are: (i) robust linear beamforming in an interfering adhoc network, (ii) robust design of a general relay network, including the two-way relay channel as a special case, and (iii) a half-duplex one-way relay system with multiple relays. For these networks, we formulate the design problems of minimizing the (sum) MSE of the symbol detection subject to different average power budget constraints. We show that these design problems are non-convex (with bilinear or trilinear constraints) and semiinfinite in multiple independent uncertainty matrix-valued variables. We propose a two-stage solution where in the first step the semi-infinite constraints are converted to linear matrix inequalities using the generalized signdefiniteness lemma, and in the second step, we use an iterative algorithm based on alternating convex search (ACS). Via simulations we evaluate the performance of the proposed scheme.

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  • 39.
    Avgouleas, Ioannis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    IoT Networking Resource Allocation and Cooperation2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Internet of Things (IoT) promises that "anything that can be connected, will be connected". It comprises of Information and Communication Technologies that interconnect billions of physical and visual things with some "basic" intelligence. The emerging IoT services will be able to react with minimal human intervention and further contribute to the big data era that requires real-time, ultrareliable, ubiquitous, scalable, and heterogeneous operation.

    This thesis is the result of our investigations on problems dealing with the evolution of such technologies. First, we explore the potential of using relay i.e., intermediate, nodes that assist users to transmit their packets in a a cellular network. Paper I provides insights into how adapting the cooperation of the relay's receiver and transmitter optimizes the network-wide throughput while the relay's queue stability is guaranteed.

    The next part of the thesis copes with the resource allocation of services on IoT devices equipped with multiple network interfaces. The resources are heterogeneous and can be split among dierent interfaces. Additionally, they are not interchangeable. In paper II, we develop optimization models for this resource allocation problem, prove the complexity of the models, and derive results that give intuition into the problems. Moreover, we propose algorithms that approximate the optimal solution and show under which circumstances this is possible.

    Finally, in paper III, we present a resource allocation problem specically for smart cities services. In comparison to the previous problem denition, resources are of one type but the IoT network device can oer capacities that vary over time. Furthermore, services have a tolerance regarding their preferred scheduling, namely, their allocation over time. We parametrize each service with a pricing function to indicate its tolerance to be served at the beginning of the scheduling window. We prove that the problem is computationally hard and provide numerical results to gain insight into how different pricing weight functions impact the allocations' distribution within the scheduling window.

    List of papers
    1. Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks
    Open this publication in new window or tab >>Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks
    2017 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 5, p. 7394-7404Article in journal (Refereed) Published
    Abstract [en]

    In this paper, we analyze the probabilistic cooperation of a full-duplex relay in a multiuser random-access network. The relay is equipped with on/off modes for the receiver and the transmitter independently. These modes are modeled as probabilities by which the receiver and the transmitter are activated. We provide analytical expressions for the performance of the relay queue, such as arrival and service rates, stability conditions, and the average queue size. We optimize the relays operation setup to maximize the network-wide throughput while, simultaneously, we keep the relays queue stable and lower the relays receptions and transmissions. Furthermore, we study the effect of the SINR threshold and the self-interference coefficient on the per-user and network-wide throughput. For low SINR threshold, we show under which circumstances it is beneficial to switch off the relay completely, or switch off the relays receiver only.

    Place, publisher, year, edition, pages
    IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017
    Keywords
    Cooperative communication; relays; relay networks; multiaccess communication; multiple access interference; internet of things (IoT); internet; wireless sensor networks (WSNs); body sensor networks (BSNs)
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-139423 (URN)10.1109/ACCESS.2016.2642540 (DOI)000403140800053 ()
    Note

    Funding Agencies|European Union [609094, 612361]

    Available from: 2017-08-07 Created: 2017-08-07 Last updated: 2019-11-08
    2. Allocation of Heterogeneous Resources of an IoT Device to Flexible Services
    Open this publication in new window or tab >>Allocation of Heterogeneous Resources of an IoT Device to Flexible Services
    Show others...
    2016 (English)In: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 3, no 5, p. 691-700Article in journal (Refereed) Published
    Abstract [en]

    Internet-of-Things (IoT) devices can be equipped with multiple heterogeneous network interfaces. An overwhelmingly large amount of services may demand some or all of these interfaces available resources. Herein, we present a precise mathematical formulation of assigning services to interfaces with heterogeneous resources in one or more rounds. For reasonable instance sizes, the presented formulation produces optimal solutions for this computationally hard problem. We prove the NP-completeness of the problem and develop two algorithms to approximate the optimal solution for big instance sizes. The first algorithm allocates the most demanding service requirements first, considering the average cost of interfaces resources. The second one calculates the demanding resource shares and allocates the most demanding of them first by choosing randomly among equally demanding shares. Finally, we provide simulation results giving insight into services splitting over different interfaces for both cases.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2016
    Keywords
    Internet of Things (IoT); mixed integer linear programming; network interfaces; optimization; resource management; scheduling algorithms
    National Category
    Communication Systems
    Identifiers
    urn:nbn:se:liu:diva-135000 (URN)10.1109/JIOT.2016.2535163 (DOI)000393047800006 ()
    Note

    Funding Agencies|Excellence Center at Linkoping-Lund in Information Technology; European Union [324515, 612316, 609094]

    Available from: 2017-03-06 Created: 2017-03-06 Last updated: 2019-11-08Bibliographically approved
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  • 40.
    Avgouleas, Ioannis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Utilizing multiple full-duplex relays in wireless systems with multiple packet reception2014In: 2014 IEEE 19th International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD), IEEE, 2014, p. 193-197Conference paper (Refereed)
    Abstract [en]

    Relay nodes with physical layer cooperation have been used extensively to assist users' transmissions in wireless networks. This network level cooperation has been lately been gaining popularity and analytical expressions of the performance of a network with up to two relay nodes exist in recent literature. In this work, we give simulation results outlining the potential network level benefits of using multiple full-duplex relay nodes. We examine configurations where multiple full-duplex transceivers offer consistent improvement and provide guidelines on using them different network conditions.

  • 41. Order onlineBuy this publication >>
    Avgouleas, Ioannis M.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Cooperation and Resource Allocation in Wireless Networking towards the IoT2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Internet of Things (IoT) should be able to react with minimal human intervention and contribute to the Artificial Intelligence (AI) era requiring real-time and scalable operation under heterogeneous network infrastructures. This thesis investigates how cooperation and allocation of resources can contribute to the evolution of future wireless networks supporting the IoT.

    First, we examine how to allocate resources to IoT services which run on devices equipped with multiple network interfaces. The resources are heterogeneous and not interchangeable, and their allocation to a service can be split among different interfaces. We formulate an optimization model for this allocation problem, prove its complexity, and derive two heuristic algorithms to approximate the solution in large instances of the problem.

    The concept of virtualization is promising towards addressing the heterogeneity of IoT resources by providing an abstraction layer between software and hardware. Network function virtualization (NFV) decouples traditional network operations such a routing from proprietary hardware platforms and implements them as software entities known as virtualized network functions (VNFs). In the second paper, we study how VNF demands can be allocated to Virtual Machines (VMs) by considering the completion-time tolerance of the VNFs. We prove that the problem is NP-complete and devise a subgradient optimization algorithm to provide near-optimal solutions. Our numerical results demonstrate the effectiveness of our algorithm compared to two benchmark algorithms.

    Furthermore, we explore the potential of using intermediate nodes, the so-called relays, in IoT networks. In the third paper, we study a multi-user random-access network with a relay node assisting users in transmitting their packets to a destination node. We provide analytical expressions for the performance of the relay's queue and the system throughput. We optimize the relay’s operation parameters to maximize the network-wide throughput while maintaining the relay's queue stability. A stable queue at relay guarantees finite delay for the packets. Furthermore, we study the effect of the wireless links' signal-to-interference-plusnoise ratio (SINR) threshold and the self-interference (SI) cancellation on the per-user and network-wide throughput.

    Additionally, caching at the network edge has recently emerged as an encouraging solution to offload cellular traffic and improve several performance metrics of the network such as throughput, delay and energy efficiency. In the fourth paper, we study a wireless network that serves two types of traffic: cacheable and non-cacheable traffic. In the considered system, a wireless user with cache storage requests cacheable content from a data center connected with a wireless base station. The user can be assisted by a pair of wireless helpers that exchange non-cacheable content as well. We devise the system throughput and the delay experienced by the user and provide numerical results that demonstrate how they are affected by the non-cacheable packet arrivals, the availability of caching helpers, the parameters of the caches, and the request rate of the user.

    Finally, in the last paper, we consider a time-slotted wireless system that serves both cacheable and non-cacheable traffic with the assistance of a relay node. The latter has storage capabilities to serve both types of traffic. We investigate how allocating the storage capacity to cacheable and non-cacheable traffic affects the system throughput. Our numerical results provide useful insights into the system throughput e.g., that it is not necessarily beneficial to increase the storage capacity for the non-cacheable traffic to realize better throughput at the non-cacheable destination node.

    List of papers
    1. Allocation of Heterogeneous Resources of an IoT Device to Flexible Services
    Open this publication in new window or tab >>Allocation of Heterogeneous Resources of an IoT Device to Flexible Services
    Show others...
    2016 (English)In: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 3, no 5, p. 691-700Article in journal (Refereed) Published
    Abstract [en]

    Internet-of-Things (IoT) devices can be equipped with multiple heterogeneous network interfaces. An overwhelmingly large amount of services may demand some or all of these interfaces available resources. Herein, we present a precise mathematical formulation of assigning services to interfaces with heterogeneous resources in one or more rounds. For reasonable instance sizes, the presented formulation produces optimal solutions for this computationally hard problem. We prove the NP-completeness of the problem and develop two algorithms to approximate the optimal solution for big instance sizes. The first algorithm allocates the most demanding service requirements first, considering the average cost of interfaces resources. The second one calculates the demanding resource shares and allocates the most demanding of them first by choosing randomly among equally demanding shares. Finally, we provide simulation results giving insight into services splitting over different interfaces for both cases.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2016
    Keywords
    Internet of Things (IoT); mixed integer linear programming; network interfaces; optimization; resource management; scheduling algorithms
    National Category
    Communication Systems
    Identifiers
    urn:nbn:se:liu:diva-135000 (URN)10.1109/JIOT.2016.2535163 (DOI)000393047800006 ()
    Note

    Funding Agencies|Excellence Center at Linkoping-Lund in Information Technology; European Union [324515, 612316, 609094]

    Available from: 2017-03-06 Created: 2017-03-06 Last updated: 2019-11-08Bibliographically approved
    2. Virtual Network Functions Scheduling under Delay-Weighted Pricing
    Open this publication in new window or tab >>Virtual Network Functions Scheduling under Delay-Weighted Pricing
    2019 (English)In: IEEE Networking Letters, E-ISSN 2576-3156, Vol. 1, no 4, p. 160-163Article in journal (Refereed) Published
    Abstract [en]

    We consider a cost minimization problem for High Volume Servers (HVS) equipped with Virtual Machines (VMs) to serve Virtual Network Functions (VNF) demands for resources. Given a scheduling period, a central scheduler decides which VM to use for each VNF demand. Each VM can be activated or disabled with different costs. Each VNF has a delay-weighted pricing function to indicate its completion time tolerance. We prove the NP-completeness of the problem and develop an algorithm based on Lagrangian relaxation and subgradient optimization to deal with this computational complexity. Finally, our numerical results demonstrate our algorithm’s effectiveness compared to two benchmarks.

    Place, publisher, year, edition, pages
    IEEE, 2019
    Keywords
    Optimization, Linear programming, Resource management, Pricing, Network function virtualization, Complexity theory, Servers
    National Category
    Computer Engineering
    Identifiers
    urn:nbn:se:liu:diva-161731 (URN)10.1109/LNET.2019.2937237 (DOI)
    Available from: 2019-11-08 Created: 2019-11-08 Last updated: 2020-10-29Bibliographically approved
    3. Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks
    Open this publication in new window or tab >>Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks
    2017 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 5, p. 7394-7404Article in journal (Refereed) Published
    Abstract [en]

    In this paper, we analyze the probabilistic cooperation of a full-duplex relay in a multiuser random-access network. The relay is equipped with on/off modes for the receiver and the transmitter independently. These modes are modeled as probabilities by which the receiver and the transmitter are activated. We provide analytical expressions for the performance of the relay queue, such as arrival and service rates, stability conditions, and the average queue size. We optimize the relays operation setup to maximize the network-wide throughput while, simultaneously, we keep the relays queue stable and lower the relays receptions and transmissions. Furthermore, we study the effect of the SINR threshold and the self-interference coefficient on the per-user and network-wide throughput. For low SINR threshold, we show under which circumstances it is beneficial to switch off the relay completely, or switch off the relays receiver only.

    Place, publisher, year, edition, pages
    IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017
    Keywords
    Cooperative communication; relays; relay networks; multiaccess communication; multiple access interference; internet of things (IoT); internet; wireless sensor networks (WSNs); body sensor networks (BSNs)
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-139423 (URN)10.1109/ACCESS.2016.2642540 (DOI)000403140800053 ()
    Note

    Funding Agencies|European Union [609094, 612361]

    Available from: 2017-08-07 Created: 2017-08-07 Last updated: 2019-11-08
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  • 42.
    Avgouleas, Ioannis
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    A wireless caching helper system with heterogeneous traffic and random availability2021In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2021, no 1, article id 69Article in journal (Refereed)
    Abstract [en]

    Multimedia content streaming from Internet-based sources emerges as one of the most demanded services by wireless users. In order to alleviate excessive traffic due to multimedia content transmission, many architectures (e.g., small cells, femtocells, etc.) have been proposed to offload such traffic to the nearest (or strongest) access point also called "helper". However, the deployment of more helpers is not necessarily beneficial due to their potential of increasing interference. In this work, we evaluate a wireless system which can serve both cacheable and non-cacheable traffic. More specifically, we consider a general system in which a wireless user with limited cache storage requests cacheable content from a data center that can be directly accessed through a base station. The user can be assisted by a pair of wireless helpers that exchange non-cacheable content as well. Files not available from the helpers are transmitted by the base station. We analyze the system throughput and the delay experienced by the cached user and show how these performance metrics are affected by the packet arrival rate at the source helper, the availability of caching helpers, the caches parameters, and the users request rate by means of numerical results.

    Download full text (pdf)
    fulltext
  • 43.
    Avgouleas, Ioannis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Performance Evaluation of Wireless Caching Helper Systems2019In: 2019 INTERNATIONAL CONFERENCE ON WIRELESS AND MOBILE COMPUTING, NETWORKING AND COMMUNICATIONS (WIMOB), IEEE , 2019Conference paper (Refereed)
    Abstract [en]

    In this work, we evaluate a wireless system in which we distinguish between cacheable and non-cacheable traffic. More specifically, we consider a general system in which a wireless user with limited cache storage requests cacheable content from a data center that can be directly accessed through a base station. The user can be assisted by a pair of wireless helpers that exchange non-cacheable content. Packets arrive at the queue of the source helper in bursts. Each helper has its own caches to assist the users requests for cacheable content. Files not available from the helpers are transmitted by the base station. We analyze the system throughput and the delay experienced by the user and show how they are affected by the packet arrival rate at the source helper, the availability of caching helpers, the caches parameters, and the users request rate by means of numerical results.

  • 44.
    Avgouleas, Ioannis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Scheduling Services on an IoT Device Under Time-Weighted Pricing2017In: Conference Proceedings IEEE 28th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC): Workshop on "Communications for Networked Smart Cities", IEEE conference proceedings, 2017, p. 1-5Conference paper (Refereed)
    Abstract [en]

    The emerging vision of smart cities necessitates the use of Internet of Things (IoT) network devices to implement sustainable solutions that will improve the operations of urban areas. A massive amount of smart cities services may demand allocation of computational resources, such as processing power or storage, that IoT devices offer. Within this context, we present an IoT network device comprising interfaces with one specific computational resource available. The efficient utilization of available IoT resources would improve the Quality of Service (QoS) of the IoT network that serves the smart city. All resource allocations must be completed within a given scheduling window and every service is parametrized by a pricing weight function to indicate its tolerance to be served at the beginning of the scheduling window. We propose a mathematical optimization formulation to minimize the total cost of allocating all demands within the scheduling window considering the tolerance level of each service at the same time. Moreover, we prove that the problem is computationally hard and we provide numerical results to gain insight into the impact of different pricing weight functions on the allocations’ distribution within the scheduling window.

    Download full text (pdf)
    Scheduling Services on an IoT Device Under Time-Weighted Pricing
  • 45. Order onlineBuy this publication >>
    Axell, Erik
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Spectrum Sensing Algorithms Based on Second-Order Statistics2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cognitive radio is a new concept of reusing spectrum in an opportunistic manner. Cognitive radio is motivated by recent measurements of spectrum utilization, showing unused resources in frequency, time and space. Introducing cognitive radios in a primary network inevitably creates increased interference to the primary users. Secondary users must sense the spectrum and detect primary users' signals at very low SNR, to avoid causing too much interference.This dissertation studies this detection problem, known as spectrum sensing.

    The fundamental problem of spectrum sensing is to discriminate an observation that contains only noise from an observation that contains a very weak signal embedded in noise. In this work, detectors are derived that exploit known properties of the second-order moments of the signal. In particular, known structures of the signal covariance are exploited to circumvent the problem of unknown parameters, such as noise and signal powers or channel coefficients.

    The dissertation is comprised of six papers, all in different ways related to spectrum sensing based on second-order statistics. In the first paper, we considerspectrum sensing of orthogonal frequency-division multiplexed (OFDM) signals in an additive white Gaussian noise channel. For the case of completely known noise and signal powers, we set up a vector-matrix model for an OFDM signal with a cyclic prefix and derive the optimal Neyman-Pearson detector from first principles. For the case of completely unknown noise and signal powers, we derive a generalized likelihood ratio test (GLRT) based on empirical second-order statistics of the received data. The proposed GLRT detector exploits the non-stationary correlation structure of the OFDM signal and does not require any knowledge of the noise or signal powers.

    In the second paper, we create a unified framework for spectrum sensing of signals which have covariance matrices with known eigenvalue multiplicities. We derive the GLRT for this problem, with arbitrary eigenvalue multiplicities under both hypotheses. We also show a number of applications to spectrum sensing for cognitive radio.

    The general result of the second paper is used as a building block, in the third and fourth papers, for spectrum sensing of second-order cyclostationary signals received at multiple antennas and orthogonal space-time block coded (OSTBC) signals respectively. The proposed detector of the third paper exploits both the spatial and the temporal correlation of the received signal, from knowledge of the fundamental period of the cyclostationary signal and the eigenvalue multiplicities of the temporal covariance matrix.

    In the fourth paper, we consider spectrum sensing of signals encoded with an OSTBC. We show how knowledge of the eigenvalue multiplicities of the covariance matrix are inherent owing to the OSTBC, and propose an algorithm that exploits that knowledge for detection. We also derive theoretical bounds on the performance of the proposed detector. In addition, we show that the proposed detector is robust to a carrier frequency offset, and propose another detector that deals with timing synchronization using the detector for the synchronized case as a building block.

    A slightly different approach to covariance matrix estmation is taken in the fifth paper. We consider spectrum sensing of Gaussian signals with structured covariance matrices, and propose to estimate the unknown parameters of the covariance matrices using covariance matching estimation techniques (COMET). We also derive the optimal detector based on a Gaussian approximation of the sample covariance matrix, and show that this is closely connected to COMET.

    The last paper deals with the problem of discriminating samples that containonly noise from samples that contain a signal embedded in noise, when the variance of the noise is unknown. We derive the optimal soft decision detector using a Bayesian approach. The complexity of this optimal detector grows exponentially with the number of observations and as a remedy, we propose a number of approximations to it. The problem under study is a fundamental one andit has applications in signal denoising, anomaly detection, and spectrum sensing for cognitive radio.

    List of papers
    1. Optimal and Sub-Optimal Spectrum Sensing of OFDM Signals in Known and Unknown Noise Variance
    Open this publication in new window or tab >>Optimal and Sub-Optimal Spectrum Sensing of OFDM Signals in Known and Unknown Noise Variance
    2011 (English)In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 29, no 2, p. 290-304Article in journal (Refereed) Published
    Abstract [en]

    We consider spectrum sensing of OFDM signals in an AWGN channel. For  the case of completely known noise and signal powers, we set up  a vector-matrix model for an OFDM signal with a cyclic prefix and  derive the optimal Neyman-Pearson detector from first  principles. The optimal detector exploits the inherent correlation  of the OFDM signal incurred by the repetition of data in the cyclic  prefix, using knowledge of the length of the cyclic prefix and the  length of the OFDM symbol. We compare the optimal detector to the energy  detector numerically. We show that the energy detector is  near-optimal (within 1 dB SNR) when the noise variance is  known. Thus, when the noise power is known, no substantial gain can  be achieved by using any other detector than the energy detector.

    For the case of completely unknown noise and signal powers, we  derive a generalized likelihood ratio test (GLRT) based onempirical second-order statistics of  the received data. The proposed GLRT detector exploits the  non-stationary correlation structure of the OFDM signal and does not  require any knowledge of the noise power or the signal power. The  GLRT detector is compared to state-of-the-art OFDM signal detectors,  and shown to improve the detection performance with 5 dB SNR in  relevant cases.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2011
    Keywords
    spectrum sensing, signal detection, OFDM, cyclic prefix, subspace detection, second-order statistics
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-58515 (URN)10.1109/JSAC.2011.110203 (DOI)000286676500003 ()
    Note

    ©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Erik Axell and Erik G. Larsson, Optimal and Sub-Optimal Spectrum Sensing of OFDM Signals in Known and Unknown Noise Variance, 2011, IEEE Journal on Selected Areas in Communications, (29), 2, 290-304. http://dx.doi.org/10.1109/JSAC.2011.110203

    The previous status of this article was Manuskript.

    Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2017-12-12Bibliographically approved
    2. A Unified Framework for GLRT-Based Spectrum Sensing of Signals with Covariance Matrices with Known Eigenvalue Multiplicities
    Open this publication in new window or tab >>A Unified Framework for GLRT-Based Spectrum Sensing of Signals with Covariance Matrices with Known Eigenvalue Multiplicities
    2011 (English)In: Proceedings of the IEEE International Conference on Acoustics, Speech and SignalProcessing (ICASSP), IEEE conference proceedings, 2011, p. 2956-2959Conference paper, Published paper (Refereed)
    Abstract [en]

    In this paper, we create a unified framework for spectrum sensing of signals which have covariance matrices with known eigenvalue multiplicities. We derive the generalized likelihood-ratio test (GLRT) for this problem, with arbitrary eigenvalue multiplicities under both hypotheses. We also show a number of applications to spectrum sensing for cognitive radio and show that the GLRT for these applications, of which some are already known, are special cases of the general result.

    Place, publisher, year, edition, pages
    IEEE conference proceedings, 2011
    Series
    IEEE International Conference on Acoustics, Speech and SignalProcessing, ISSN 1520-6149
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-64320 (URN)10.1109/ICASSP.2011.5946277 (DOI)000296062403092 ()
    Note
    ©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Erik Axell and Erik G. Larsson, A Unified Framework for GLRT-Based Spectrum Sensing of Signals with Covariance Matrices with Known Eigenvalue Multiplicities, 2011, Proceedings of the IEEE International Conference on Acoustics, Speech and SignalProcessing (ICASSP), 2956-2959. http://dx.doi.org/10.1109/ICASSP.2011.5946277 Available from: 2011-01-19 Created: 2011-01-19 Last updated: 2016-08-31
    3. Multiantenna Spectrum Sensing of a Second-Order Cyclostationary Signal
    Open this publication in new window or tab >>Multiantenna Spectrum Sensing of a Second-Order Cyclostationary Signal
    2011 (English)In: Proceedings of the 4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP'11), 2011, p. 329-332Conference paper, Published paper (Refereed)
    Abstract [en]

    We consider spectrum sensing of a second-order cyclostationary signal receivedat multiple antennas. The proposed detector exploits both the spatial andthe temporal correlation of the received signal, from knowledge of thefundamental period of the cyclostationary signal and the eigenvaluemultiplicities of the temporal covariance matrix. All other parameters, suchas the channel gains or the noise power, are assumed to be unknown. The proposeddetector is shown numerically to outperform state-of-the-art detectors forspectrum sensing of anOFDM signal, both when using a single antenna and with multiple antennas.

    Keywords
    spectrum sensing, multiple antennas, cyclostationarity, GLRT
    National Category
    Communication Systems Signal Processing
    Identifiers
    urn:nbn:se:liu:diva-70858 (URN)10.1109/CAMSAP.2011.6136017 (DOI)978-1-4577-2103-8 (ISBN)
    Conference
    4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP), December 13-16 2011, San Juan, Puerto Rico (USA)
    Funder
    eLLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsSwedish Research Council
    Available from: 2011-09-20 Created: 2011-09-20 Last updated: 2016-08-31Bibliographically approved
    4. Spectrum Sensing of Orthogonal Space-Time Block Coded Signals with Multiple Receive Antennas
    Open this publication in new window or tab >>Spectrum Sensing of Orthogonal Space-Time Block Coded Signals with Multiple Receive Antennas
    2010 (English)In: Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Institute of Electrical and Electronics Engineers (IEEE), 2010, p. 3110-3113Conference paper, Published paper (Other academic)
    Abstract [en]

    We consider detection of signals encoded with orthogonal space-time block codes (OSTBC), using multiple receive antennas. Such signals contain redundancy and they have a specific structure, that can be exploited for detection. We derive the optimal detector, in the Neyman-Pearson sense, when all parameters are known. We also consider unknown noise variance, signal variance and channel coefficients. We propose a number of GLRT based detectors for the different cases, that exploit the redundancy structure of the OSTBC signal. We also propose an eigenvalue-based detector for the case when all parameters are unknown. The proposed detectors are compared to the energy detector. We show that when only the noise variance is known, there is no gain in exploiting the structure of the OSTBC. However, when the noise variance is unknown there can be a significant gain.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2010
    Series
    Acoustics Speech and Signal Processing (ICASSP), ISSN 1520-6149, E-ISSN 2379-190X
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-51745 (URN)10.1109/ICASSP.2010.5496088 (DOI)000287096003014 ()9781424442959 (ISBN)9781424442966 (ISBN)
    Conference
    IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2010, 14-19 March, Dallas, Texas, U.S.A.
    Note

    ©2010 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.: Erik Axell and Erik G. Larsson, Spectrum Sensing of Orthogonal Space-Time Block Coded Signals with Multiple Receive Antennas, 2010, Proceedings of the 35th IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP'10).

    The previous status of this articel was Manuscript.

    Available from: 2009-11-17 Created: 2009-11-17 Last updated: 2018-02-02Bibliographically approved
    5. Spectrum Sensing of Signals with Structured Covariance Matrices Using Covariance Matching Estimation Techniques
    Open this publication in new window or tab >>Spectrum Sensing of Signals with Structured Covariance Matrices Using Covariance Matching Estimation Techniques
    2011 (English)In: Proceedings of the IEEE Global Communications Conference (GLOBECOM), 2011, p. 1-5Conference paper, Published paper (Refereed)
    Abstract [en]

    In this work, we consider spectrum sensing of Gaussian signals with structured covariance matrices. We show that the optimal detector based on the probability distribution of the sample covariance matrix is equivalent to the optimal detector based on the raw data, if the covariance matrices are known. However, the covariance matrices are unknown in general. Therefore, we propose to estimate the unknown parameters using covariance matching estimation techniques (COMET). We also derive the optimal detector based on a Gaussian approximation of the sample covariance matrix, and show that this is closely connected to COMET.

    Keywords
    spectrum sensing, sample covariance, COMET
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-69639 (URN)10.1109/GLOCOM.2011.6133506 (DOI)978-1-4244-9267-1 (ISBN)978-1-4244-9266-4 (ISBN)
    Conference
    IEEE Global Communications Conference (GLOBECOM), 3-7 December, Anaheim, California, USA
    Available from: 2011-07-08 Created: 2011-07-08 Last updated: 2016-08-31
    6. A Bayesian Approach to Spectrum Sensing, Denoising and Anomaly Detection
    Open this publication in new window or tab >>A Bayesian Approach to Spectrum Sensing, Denoising and Anomaly Detection
    2009 (English)In: Proceedings of the 34th IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP'09), 2009, p. 2333-2336Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper deals with the problem of discriminating samples that contain only noise from samples that contain a signal embedded in noise. The focus is on the case when the variance of the noise is unknown. We derive the optimal soft decision detector using a Bayesian approach. The complexity of this optimal detector grows exponentially with the number of observations and as a remedy, we propose a number of approximations to it. The problem under study is a fundamental one and it has applications in signal denoising, anomaly detection, and spectrum sensing for cognitive radio. We illustrate the results in the context of the latter.

    Series
    Acoustics, Speech and Signal Processing, ISSN 1520-6149 ; 2009
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-25592 (URN)10.1109/ICASSP.2009.4960088 (DOI)978-1-4244-2354-5 (ISBN)978-1-4244-2353-8 (ISBN)
    Conference
    34th IEEE international conference on acoustics, speech and signal processing,19-24 April, Taipei, Taiwan
    Note
    ©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Erik Axell and Erik G. Larsson, A Bayesian Approach to Spectrum Sensing, Denoising and Anomaly Detection, 2009, Proceedings of the 34th IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP'09), 2333-2336. http://dx.doi.org/10.1109/ICASSP.2009.4960088Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2016-08-31Bibliographically approved
    Download full text (pdf)
    Spectrum Sensing Algorithms Based on Second-Order Statistics
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    omslag
  • 46.
    Axell, Erik
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Multiantenna Spectrum Sensing of a Second-Order Cyclostationary Signal2011In: Proceedings of the 4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP'11), 2011, p. 329-332Conference paper (Refereed)
    Abstract [en]

    We consider spectrum sensing of a second-order cyclostationary signal receivedat multiple antennas. The proposed detector exploits both the spatial andthe temporal correlation of the received signal, from knowledge of thefundamental period of the cyclostationary signal and the eigenvaluemultiplicities of the temporal covariance matrix. All other parameters, suchas the channel gains or the noise power, are assumed to be unknown. The proposeddetector is shown numerically to outperform state-of-the-art detectors forspectrum sensing of anOFDM signal, both when using a single antenna and with multiple antennas.

  • 47.
    Babu, Bibin
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Connected Me: Hardware for high speed BCC2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Body coupled communication (BCC) is a hot topic in personal networking domain. Many works arepublished suggesting different architectures for BCC since its inception in 1995 by Zimmerman. The number ofelectronic gadgets used by a single person increases as time pass by. Its a tedious job to transfer data betweenthen from a user point of view. Many of these gadgets can share their resources and save power and money.The existing wired or wireless networks does not meet the requirements for this network like scalable data rate,security etc. So here comes the novel idea of using human body as communication medium. The aim of thisthesis is to realize a hardware for BCC based on wide band signaling as part of a big project.The human body consists of 70% of water. This property makes the human body a fairly good conductor.By exploiting this basic property makes the BCC possible. A capacitance is formed if we place a metal platenear to the human body with the skin as a dielectric. This capacitance forms the interface between the humanbody and the analog front-end of the BCC transceiver. Any other metal structures near to the human body canattenuate the signal.A first-order communication link is established in software by the human body model and the transceiver inthe loop along with noise and interference. This communication link is used to verify the human body modeland the base band model done as part of the same big project. Based on the results a hardware prototype isimplemented. Measurements are taken in different scenarios using the hardware setup. The trade-off betweendesign parameters are discussed based on the results. At the end, it suggests a road map to take the projectfurther.

    Download full text (pdf)
    Connected Me: Hardware for high speed BCC
  • 48.
    Bae, Cheolyong
    et al.
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    Gustafsson, Oscar
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    Finite Word Length Analysis for FFT-Based Chromatic Dispersion Compensation Filters2021In: Signal Processing in Photonic Communications 2021, OPTICA , 2021Conference paper (Refereed)
    Abstract [en]

    Finite word length effects for frequency-domain implementation of chromatic dispersion compensation is analyzed. The results show a significant difference for the different factors when it comes to power consumption and receiver penalty.

    Download full text (pdf)
    fulltext
  • 49.
    Bai, Jianan
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering. Virgnia Tech, VA 24060 USA.
    Song, Hao
    Virginia Tech, VA 24060 USA.
    Yi, Yang
    Virginia Tech, VA 24060 USA.
    Liu, Lingjia
    Virginia Tech, VA 24060 USA.
    Multiagent Reinforcement Learning Meets Random Access in Massive Cellular Internet of Things2021In: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 8, no 24, p. 17417-17428Article in journal (Refereed)
    Abstract [en]

    Internet of Things (IoT) has attracted considerable attention in recent years due to its potential of interconnecting a large number of heterogeneous wireless devices. However, it is usually challenging to provide reliable and efficient random access control when massive IoT devices are trying to access the network simultaneously. In this article, we investigate methods to introduce intelligent random access management for a massive cellular IoT network to reduce access latency and access failures. Toward this end, we introduce two novel frameworks, namely, local device selection (LDS) and intelligent preamble selection (IPS). LDS enables local communication between neighboring devices to provide cluster-wide cooperative congestion control, which leads to a better distribution of the access intensity under bursty traffics. Taking advantage of the capability of reinforcement learning in developing cooperative multiagent policies, IPS is introduced to enable the optimization of the preamble selection policy in each IoT clusters. To handle the exponentially growing action space in IPS, we design a novel reinforcement learning structure, named branching actor-critic, to ensure that the output size of the underlying neural networks only grows linearly with the number of action dimensions. Simulation results indicate that the introduced mechanism achieves much lower access delays with fewer access failures in various realistic scenarios of interests.

  • 50.
    Bana, Alexandru-Sabin
    et al.
    Aalborg Univ, Denmark.
    de Carvalho, Elisabeth
    Aalborg Univ, Denmark.
    Soret, Beatriz
    Aalborg Univ, Denmark.
    Abrao, Taufik
    Univ Estadual Londrina, Brazil.
    Marinello, Jose Carlos
    Univ Estadual Londrina, Brazil.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Popovski, Petar
    Aalborg Univ, Denmark.
    Massive MIMO for Internet of Things (IoT) connectivity2019In: Physical Communication, ISSN 1874-4907, E-ISSN 1876-3219, Vol. 37, article id UNSP 100859Article in journal (Refereed)
    Abstract [en]

    Massive MIMO is considered to be one of the key technologies in the emerging 5G systems, but also a concept applicable to other wireless systems. Exploiting the large number of degrees of freedom (DoFs) of massive MIMO is essential for achieving high spectral efficiency, high data rates and extreme spatial multiplexing of densely distributed users. On the one hand, the benefits of applying massive MIMO for broadband communication are well known and there has been a large body of research on designing communication schemes to support high rates. On the other hand, using massive MIMO for Internet-of-Things (IoT) is still a developing topic, as IoT connectivity has requirements and constraints that are significantly different from the broadband connections. In this paper we investigate the applicability of massive MIMO to IoT connectivity. Specifically, we treat the two generic types of IoT connections envisioned in 5G: massive machine-type communication (mMTC) and ultra-reliable low-latency communication (URLLC). This paper fills this important gap by identifying the opportunities and challenges in exploiting massive MIMO for IoT connectivity. We provide insights into the trade-offs that emerge when massive MIMO is applied to mMTC or URLLC and present a number of suitable communication schemes. The discussion continues to the questions of network slicing of the wireless resources and the use of massive MIMO to simultaneously support IoT connections with very heterogeneous requirements. The main conclusion is that massive MIMO can bring benefits to the scenarios with IoT connectivity, but it requires tight integration of the physical-layer techniques with the protocol design. (C) 2019 Elsevier B.V. All rights reserved.

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    fulltext
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