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  • 1.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Askoxylakis, Ioannis
    FORTH, Institute of Computer Science, Greece.
    Fowler, Scott
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Gundlegård, David
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Traganitis, Apostolos
    FORTH, Institute of Computer Science, Greece.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Security and Resilience in Cognitive Radio Networks2011In: European Research Consortium for Informatics and Mathematics Magazine, ISSN 0926-4981, no 85, p. 48-49Article in journal (Refereed)
    Abstract [en]

    After more than a decade of research, system securityand resilience is now the major technological barrier forthe Cognitive Radio (CR) to be adopted by the telecommunication industry. New ideas are required tomake CR networks secure and robust against attacks taking advantage the inherent characteristics of the CR functionality. This work explores key points that urgentlyneed to be addressed.

  • 2.
    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.

  • 3.
    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.

  • 4.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Chen, Lei
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A Fully Decentralized and Load-Adaptive Fractional Frequency Reuse Scheme2011In: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2011 IEEE 19th International Symposium on, 2011, p. 425-428Conference paper (Refereed)
    Abstract [en]

    A new fully decentralized dynamic fractional frequency reuse (FFR)-based scheme for cellular OFDMA networks is introduced. FFR is a technique to mitigate inter-cell interference to improve the throughput of interference-limited users on the cell edge, to the expense of the rest of the cell's users and the aggregate throughput. The proposed scheme aims to limit the FFR-incurred loss of the center users' throughput, while still providing sufficient bandwidth for the cell edge users' communication. This is done by local information sharing and distributed optimization. The resulting flexibility of frequency reuse can be especially beneficial in scenarios with non-uniform and time-varying load. The optimization task is accomplished by solving a knapsack problem in each cell, where the goal is to maximize the center throughput while maintaining acceptable degradation on the cell edge with respect to the original FFR allocation. The performance improvement resulting from the distributed and dynamic FFR scheme is demonstrated by snapshot simulations on an 81-cells network with asymmetric cell load. The proposed scheme achieves up to a 62% gain in cell-center throughput with a cost of no more than 18% at the edges when compared to the classic FFR scheme. The overall system throughput improvement ranges from 22% to 58%.

  • 5.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Chen, Lei
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Communications and Transport Systems.
    Optimal and Collaborative Rate Selection for Interference Cancellation in Wireless Networks2011In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 15, no 8, p. 819-821Article in journal (Refereed)
    Abstract [en]

    Analysis of wireless systems commonly assumes single-user detection at the receivers. Interference is typically treated as noise. On the other hand, multiuser detection has long been taking advantage of interference cancellation (IC) to increase capacity. We exploit IC by optimal rate selection. Transmission rates are collaboratively optimized to maximize the benefit of IC. A link reduces its rate, if that enables IC to significantly boost the SINR on other links. We provide a complexity analysis and an integer programming model to find the optimal IC pattern. Simulation results indicate that throughput improvement is over 30% in low SINR regimes.

    Download full text (pdf)
    fulltext
  • 6.
    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.

  • 7.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    He, Qing
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    On Emptying a Wireless Network in Minimum Time2012In: 2012 IEEE International Symposium on Information Theory Proceedings (ISIT), Piscataway, NJ, USA: IEEE , 2012, p. 2671-2675Conference paper (Refereed)
    Abstract [en]

    We consider N transmitter-receiver pairs that share a wireless channel and we address the problem of obtaining a schedule for activating subsets of these links so as to empty the transmitter queues in minimum time. Our aim is to provide theoretical insights for the optimality characterization of the problem, using both a cross-layer model formulation, which takes into account the effect of interference on achievable transmission rates, as well as a collision-based model, which does not incorporate the physical layer realities into the problem. We present the basic linear programming formulation of the problem and establish that the optimal schedule need not consist of more than N subset activation frames. We then prove that the problem is NP-hard for all reasonable continuous rate functions. Finally, we obtain sufficient and/or necessary conditions for optimality in a number of special cases.

  • 8.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Gundlegård, David
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Rydergren, Clas
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Rajna, Botond
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Vrotsou, Katerina
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Carlsson, Richard
    Ericsson Research, Services & Software.
    Forgeat, Julien
    Ericsson Research, Services & Software.
    Hu, Tracy H
    Ericsson Research, Services & Software.
    Liu, Evan L
    Ericsson Research, Services & Software.
    Moritz, Simon
    Ericsson Research, Services & Software.
    Zhao, Sky
    Ericsson Research, Services & Software.
    Zheng, Yaotian
    Ericsson Research, Services & Software.
    Mobility modeling for transport efficiency: Analysis of travel characteristics based on mobile phone data2013In: Netmob 2013: Mobile phone data for development / [ed] Vincent Blondel, 2013Conference paper (Refereed)
    Abstract [en]

    Signaling data from the cellular networks can provide a means of analyzing the efficiency of a deployed transportation system and assisting in the formulation of transport models to predict its future use. An approach based on this type of data can be especially appealing for transportation systems that need massive expansions, since it has the added benefit that no specialized equipment or installations are required, hence it can be very cost efficient.

    Within this context in this paper we describe how such obtained data can be processed and used in order to act as enablers for traditional transportation analysis models. We outline a layered, modular architectural framework that encompasses the entire process and present results from initial analysis of mobile phone call data in the context of mobility, transport and transport infrastructure. We finally introduce the Mobility Analytics Platform, developed by Ericsson Research, tailored for mobility analysis, and discuss techniques for analyzing transport supply and demand, and give indication on how cell phone use data can be used directly to analyze the status and use of the current transport infrastructure.

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    fulltext
  • 9.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Papadakis, Stefanos
    FORTH.
    Traganitis, Apostolos
    FORTH & UoC.
    Vasilios, Siris
    AUEB.
    Adjacent Channel Interference in 802.11a Is Harmful: Testbed Validation of a Simple Quantification Model2011In: IEEE COMMUNICATIONS MAGAZINE, ISSN 0163-6804, Vol. 49, no 3, p. 160-166Article in journal (Refereed)
    Abstract [en]

    Wireless LAN radio interfaces based on the IEEE 802.11a standard have lately found widespread use in many wireless applications. A key reason for this was that although the predecessor, IEEE 802.11b/ g, had a poor channelization scheme, which resulted in strangling adjacent channel interference (ACI), 802.11a was widely believed to be ACI-free due to a better channelization combined with OFDM transmission. We show that this is not the case. ACI does exist in 802.11a, and we can quantify its magnitude and predict its results. For this, we present minor modifications of a simple model originally introduced by [1] that allow us to calculate bounding values of the 802.11a ACI, which can be used in link budget calculations. Using a laboratory testbed, we verify the estimations of the model, performing experiments designed to isolate the affected 802.11 mechanisms. This isolation was enabled by not using the wireless medium, and emulating it over cables and attenuators. Our results show clear throughput degradation because of ACI in 802.11a, the magnitude of which depends on the interfering data rates, packet sizes, and utilization of the medium.

  • 10.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Sajid, Muhammad
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Siddiqui, Imran
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A distributed, load-aware, power and frequency bargaining protocol for LTE-based networks2012In: 2012 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), Piscataway, NJ, USA: IEEE , 2012, p. 6525-6529Conference paper (Refereed)
    Abstract [en]

    A distributed, load-aware, joint power and frequency allocation protocol is introduced for LTE-based cellular networks, and system-level simulations are performed. Our proposed scheme aims to cooperatively limit the impact of Fractional Frequency Reuse (FFR) on the center users throughput compared to the Reuse 1 scheme, while providing sufficient throughput for the edge users. This is achieved through an asynchronous, lightweight scheme of local message exchange between neighboring LTE eNodeBs. The proposed scheme facilitates a type of "bargain" where an overloaded sector requests permission to utilize its neighbors edge bands for its center users at a limited set of transmit power levels. Grants are generated at each neighbor by solving a small-scale optimization problem. Using an LTE simulator we evaluate our scheme on a network with 21 sectors of varying load patterns. The proposed schemes performance for center users is consistently improved with respect to FFR-3, while for edge users the performance degradation is controlled by a parameter we set in the optimization problems definitions; compared to Reuse 1 edge users still have gains. Specifically, we observed up to a 46% gain in the sectors center throughput with a cost below 9% at the edges when compared to the classic FFR scheme, while the overall system throughput goes up by up to 26% in heavily loaded scenarios.

  • 11.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Tragos, Elias.Institute of Computer science, Foundation for research and technology, Hellas, FORTH-ICM, Heraklion, Grekland.Pöhls, Henrich C.Institute of IT-security and Security Law, University of Passau, Tyskland .Kapovits, AdamEurescom GmbH, Heidelberg, Germany.Bassi, Alessandro.Alessandro Bassi Consulting, Juan le Pins, Frankrike.
    Designing, developing, and facilitating smart cities: urban design to IoT solutions2017Collection (editor) (Other academic)
    Abstract [en]

    This book discusses how smart cities strive to deploy and interconnect infrastructures and services to guarantee that authorities and citizens have access to reliable and global customized services. The book addresses the wide range of topics present in the design, development and running of smart cities, ranging from big data management, Internet of Things, and sustainable urban planning. The authors cover - from concept to practice – both the technical aspects of smart cities enabled primarily by the Internet of Things and the socio-economic motivations and impacts of smart city development. The reader will find smart city deployment motivations, technological enablers and solutions, as well as state of the art cases of smart city implementations and services. · Provides a single compendium of the technological, political, and social aspects of smart cities; · Discusses how the successful deployment of smart Cities requires a unified infrastructure to support the diverse set of applications that can be used towards urban development; · Addresses design, development and running of smart cities, including big data management and Internet of Things applications.

  • 12.
    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.

  • 13.
    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.

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    fulltext
  • 14.
    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.
    Cacheable and Non-Cacheable Traffic Interplay in a Relay-Assisted Wireless Network2020In: ICC 2020 - 2020 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), Institute of Electrical and Electronics Engineers (IEEE), 2020Conference paper (Refereed)
    Abstract [en]

    We study a discrete-time wireless network that serves both cacheable and non-cacheable traffic with assistance of a relay node with storage capabilities for both types of traffic. We investigate how allocating the storage capacity to cacheable and non-cacheable traffic affects the network throughput. Our numerical results provide useful insights by varying not only the allocation of cacheable to non-cacheable storage but also the rate by which non-cacheable content is transmitted, the rate by which cacheable content is requested, as well as different popularity distributions of the cached files.

  • 15.
    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.
    Cooperative Wireless Networking with Probabilistic On/Off Relaying2015In: 2015 IEEE 81ST VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING), IEEE , 2015Conference paper (Refereed)
    Abstract [en]

    In this work, we investigate the operation of energy efficient relay nodes assisting the transmission of packets from a number of users to a destination node. We study the impact of switching randomly a fraction of the relays on and off to the aggregate throughput, the average queue size and delay per packet of systems with relays transmitting in either Full-or Half-Duplex mode and under different channel transmissions characteristics. Furthermore, we prove analytically and illustrate via simulation means how these network metrics are affected.

  • 16.
    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.

  • 17.
    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.

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    Scheduling Services on an IoT Device Under Time-Weighted Pricing
  • 18.
    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.
    Yuan, Di
    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.
    Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks2017In: IEEE Access, E-ISSN 2169-3536, Vol. 5, p. 7394-7404Article in journal (Refereed)
    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.

  • 19.
    Avgouleas, Ioannis
    et al.
    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.
    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.
    Virtual Network Functions Scheduling under Delay-Weighted Pricing2019In: IEEE Networking Letters, E-ISSN 2576-3156, Vol. 1, no 4, p. 160-163Article in journal (Refereed)
    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.

  • 20.
    Broz, Jiri
    et al.
    Czech Tech Univ, Czech Republic.
    Tichy, Tomas
    Czech Tech Univ, Czech Republic.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Belinova, Zuzana
    Czech Tech Univ, Czech Republic.
    Usage of V2X Applications in Road Tunnels2022In: Applied Sciences, E-ISSN 2076-3417, Vol. 12, no 9, article id 4624Article in journal (Refereed)
    Abstract [en]

    Featured Application This article provides a general overview of technological aspects and limitations of tunnels with respect to smart technologies such as C-ITS. Many smart city applications work with calculated position and time using the Global Navigation Satellite System (GNSS) signals for enhanced precision. However, there are many places where the availability of GNSS is limited, e.g., road tunnels, which are an essential part of transport infrastructure. Tunnels also require greater attention and greater importance of approaches to ensure the safety and security aspects of traffic. The safety, distribution of information, awareness, and smooth traffic can also be ensured by V2X applications, but the current position is also needed. An experimental analysis of data connection and communication availability was performed in the Blanka tunnel (Prague) and its surroundings. The main objective of the work was to find and clearly describe the tunnel blind spots, with an emphasis on communication between cars and potentially between cars and infrastructure. This article summarizes the evaluation results of the V2X tunnel experimental test, the outputs from the analysis of these blind spots, and it provides a future perspective and suggestions that make tunnels smart by using advanced positioning approaches.

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  • 21.
    Chen, Zheng
    et al.
    University of Paris Sud, France.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Kountouris, Marios
    Huawei Technology Co Ltd, Peoples R China.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Throughput Analysis of Smart Objects with Delay Constraints2016In: 2016 IEEE 17TH INTERNATIONAL SYMPOSIUM ON A WORLD OF WIRELESS, MOBILE AND MULTIMEDIA NETWORKS (WOWMOM), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    In this paper, we analyze a shared access network with one primary device and randomly distributed smart objects with secondary priority. Assuming random traffic at the primary device and saturated queues at the smart objects with secondary priority, an access protocol is employed to adjust the random access probabilities of the smart objects depending on the congestion level of the primary. We characterize the maximum throughput of the secondary network with respect to delay constraints on the primary. Our results highlight the impact of system design parameters on the delay and throughput behavior of the shared access network with massive number of connected objects.

  • 22.
    Chen, Zheng
    et al.
    Linköping University, Department of Electrical Engineering, Communication 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.
    Kountouris, Marios
    Huawei Technol Co Ltd, France.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Throughput With Delay Constraints in a Shared Access Network With Priorities2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 9, p. 5885-5899Article in journal (Refereed)
    Abstract [en]

    In this paper, we analyze a shared access network with a fixed primary node and randomly distributed secondary nodes whose spatial distribution follows a poisson point process. The secondary nodes use a random access protocol allowing them to access the channel with probabilities that depend on the queue size of the primary node. Assuming a system with multipacket reception receivers, having bursty packet arrivals at the primary and saturated traffic at the secondary nodes, our protocol can be tuned to alleviate congestion at the primary. We analyze the throughput of the secondary network and the primary average delay, as well as the impact of the secondary node access probability and transmit power. We formulate an optimization problem to maximize the throughput of the secondary network under delay constraints for the primary node; in the case of no congestion control, the optimal access probability can be provided in closed form. Our numerical results illustrate the effect of network operating parameters on the performance of the proposed priority-based shared access protocol.

  • 23.
    Daneshfar, Nader
    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.
    Resource Allocation with Service Availability & QoS Constraints in Mobile Fog Networks2017In: 2017 IEEE CONFERENCE ON COMPUTER COMMUNICATIONS WORKSHOPS (INFOCOM WKSHPS), IEEE , 2017, p. 1018-1019Conference paper (Refereed)
    Abstract [en]

    The evolution of the Internet of Things (IoT) is bringing Cloud services closer to the networks edge. Thus, fog networking presents itself as an approach aiming to utilize more and more resources in network edge devices to provide various networking tasks. This work presents an optimization formulation that minimizes the cost of executing a set of services, taking into account the availability of resources in mobile edge devices.

  • 24.
    Daneshfar, Nader
    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.
    Polishchuk, Valentin
    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.
    Service Allocation in a Mobile Fog Infrastructure under Availability and QoS Constraints2018In: 2018 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), IEEE , 2018Conference paper (Refereed)
    Abstract [en]

    The next generation of mobile networks, namely SG, together with the Internet of Things (IoT) come with a large number of delay sensitive services. To meet their requirements, cloud services are migrating to the edge of the networks to reduce latency. The notion of fog computing, where the edge plays an active role in the execution of services, comes to meet the needs for the stringent requirements. Thus, it becomes of a high importance to address the problem of mapping services demands to infrastructure resources supply. This work addresses it taking into account the randomness of resource availability in a fog infrastructure. We introduce an integer optimization formulation to minimize the total cost under a guarantee of service execution despite the uncertainty of resources availability. Our results illustrate the effect of various system parameters, such as the diversity of the infrastructure server set, the availability of different infrastructure servers in the set, and the probability of service completion required by each service.

  • 25.
    Elshatshat, Mohamed A.
    et al.
    Institute of Computer Science - Foundation for Research and Technology - Hellas (ICS-FORTH), Greece.
    Papadakis, Stefanos
    Institute of Computer Science - Foundation for Research and Technology - Hellas (ICS-FORTH), Greece.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Improving the Spectral Efficiency in Dense Heterogeneous Networks Using D2D-Assisted eICIC2018In: 2018 IEEE 23rd International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD), Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 32-37Conference paper (Refereed)
    Abstract [en]

    Heterogeneous networks (HetNets) that consist of macro base stations (MBSs) and small base stations (SBSs) are a key architectural drive for achieving the high spectral efficiency (SE) in 5G and beyond. Moreover, device-to-device (D2D) communications underlaying mobile networks can provide reliable communications and add SE gains. A major challenge in HetNets is the inter-cell interference (ICI) due to the coexistence of multiple tiers of base stations (BSs). To tackle this challenge, the enhanced inter-cell interference coordination (eICIC) scheme was adopted by 3GPP. In eICIC the MBSs mute their transmission during the so-called ᅵalmost blank subframesᅵ (ABS). This muting strategy causes resources reduction to the MBS users (MUEs). We propose the use of D2D communications to forward the transmission from the SBS to the MUEs during ABS subframes, by using inactive UEs to relay the downlink transmission, when the destination UEs are outside the coverage of the BS. We use a heuristic resource allocation (RA) algorithm based on the traffic load at the SBSs that integrates eICIC with D2D communications to avoid the service degradation during the time-domain muting. Simulation results of a HetNet with D2D-eICIC show that the SE of our approach outperforms other interference management approaches.

  • 26.
    Elshatshat, Mohamed
    et al.
    ICS FORTH, Greece.
    Papadakis, Stefanos
    ICS FORTH, Greece.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Device-to-Device Based Inter-Cell Interference Coordination for Delay-Sensitive 5G Networks2019In: ERCIM News, ISSN 0926-4981, E-ISSN 1564-0094, no 117, p. 22-23Article in journal (Refereed)
    Abstract [en]

    Heterogeneous 5G networks that consist of dense deployment of macro base stations, small base stations and device-to-device communications play a central role in improving the spectral efficiency and the delay performance of real-time applications. Enhanced inter-cell interference coordination based on time-domain coordination mitigates the downlink interference at the small base station users equipment but degrades the delay performance of the macro base station users equipment. In this work we exploit the inactive users equipment to serve as relays between the small base station and the macro base station users equipment which ensures that the delay requirements of real time users are achieved.

  • 27.
    Enlund, Desirée
    et al.
    Linköping University, Department of Thematic Studies, The Department of Gender Studies. Linköping University, Faculty of Arts and Sciences.
    Harrison, Katherine
    Linköping University, Department of Thematic Studies, The Department of Gender Studies. Linköping University, Faculty of Arts and Sciences.
    Ringdahl, Rasmus
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Börütecene, Ahmet
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Löwgren, Jonas
    Linköping University, Department of Science and Technology, Media and Information Technology. 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.
    The role of sensors in the production of smart city spaces2022In: Big Data and Society, ISSN 2053-9517, E-ISSN 2053-9517, Vol. 9, no 2, article id 20539517221110218Article in journal (Refereed)
    Abstract [en]

    Smart cities build on the idea of collecting data about the city in order for city administration to be operated more efficiently. Within a research project gathering an interdisciplinary team of researchers ? engineers, designers, gender scholars and human geographers ? we have been working together using participatory design approaches to explore how paying attention to the diversity of human needs may contribute to making urban spaces comfortable and safe for more people. The project team has deployed sensors collecting data on air quality, sound and mobility in a smart city testbed in Norrköping, Sweden. While these sensors are meant to capture an accurate ?map? of the street and what is going on along it, our interdisciplinary conversations around the sensors have revealed the heterogeneity both of smart city planning and spatial formulations of the city. The discussions have given rise to questions regarding the work that goes into constructing the sensor box itself, as well as the work of deploying it, and how these influence the ?map? that the sensors produce. In this paper, we draw on Lefebvre to explore how the sensors themselves produce smart spaces. We analyze how the box depends on perceived space to function (e.g. requiring electricity), and simultaneously it produces conceptualizations of space that are influenced by the materiality of the box itself (e.g. sensors being affected by heat and noise). Further, we explore how the (in)visibility of sensor technology influences lived space.

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  • 28.
    Fountoulakis, Emmanouil
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Nokia Bell Labs, Germany.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Liao, Qi
    Nokia Bell Labs, Germany.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Univ Maryland, MD 20742 USA.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Dynamic Power Control for Packets with Deadlines2018In: 2018 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), IEEE , 2018Conference paper (Refereed)
    Abstract [en]

    Wireless devices need to adapt their transmission power according to the fluctuating wireless channel in order to meet constraints of delay sensitive applications. In this paper, we consider delay sensitivity in the form of strict packet deadlines arriving in a transmission queue. Packets missing the deadline while in the queue are dropped from the system. We aim at minimizing the packet drop rate under average power constraints. We utilize tools from Lyapunov optimization to find an approximate solution by selecting power allocation. We evaluate the performance of the proposed algorithm and show that it achieves the same performance in terms of packet drop rate with that of the Earliest Deadline First (EDF) when the available power is sufficient. However, our algorithm outperforms EDF regarding the trade-off between packet drop rate and average power consumption.

  • 29.
    Fowler, Scott
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Sarfraz, Jalal
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Abbas, M. Muddassir
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Bergfeldt, Erik
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Evaluation and prospects from a measurement campaign on real multimedia traffic in LTE vs. UMTS2014In: Wireless Communications, Vehicular Technology, Information Theory and Aerospace Electronic Systems (VITAE'14), IEEE 4th International Conference on, IEEE Press, 2014, p. 1-5Conference paper (Refereed)
    Abstract [en]

    The LTE standard has been developed for high-bandwidth mobile access for today’s data-heavy applications. With broadband cellular available already from the UMTS system, users are expecting the LTE network to provide high quality communication. To ensure the quality and correctness of complex systems of LTE, it is important to evaluate the behavior of traffic on a LTE network in relation to UMTS. In this paper, LTE and UMTS measurements on video traffic were performed in a real environment, allowing for greater development, and understanding of network traffic performance.

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  • 30.
    Fowler, Scott
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Sarfraz, Jalal
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Abbas, Muhammad Muddassir
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Gaussian semi-Markov Model based on Real Video Multimedia Traffic2015In: IEEE International Conference on Communications Communications (ICC) 2015 / [ed] IEEE, IEEE Press, 2015, p. 6971-6976Conference paper (Refereed)
    Abstract [en]

    The 3rd Generation Partnership Project (3GPP) introduced the new radio access technology, LTE (Long Term Evolution) and LTE-Advanced, which has the capability to provide larger bandwidth and low latencies on a wireless network in order to fulfill the demand of Users' Equipment (UEs) with acceptable Quality of Service (QoS). One of the data-heavy applications that has exploded on the market is Video. This calls for accurate modeling of video traffic. To ensure the quality and correctness of complex systems with Video traffic, it is important to evaluate the behavior of the traffic in the heterogeneous environment. This paper presents measurements on LTE Video traffic which were performed in a real environment. We derived a semi-Markov model which accurately reproduces the statistics of composite Video measurements over LTE network.

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  • 31.
    Fragkiadakis, Alexandros
    et al.
    Fdn Research and Technology Hellas, Greece .
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Tragos, Elias Z.
    Fdn Research and Technology Hellas, Greece .
    Securing Cognitive Wireless Sensor Networks: A Survey2014In: International Journal of Distributed Sensor Networks, ISSN 1550-1329, E-ISSN 1550-1477, no 393248Article, review/survey (Refereed)
    Abstract [en]

    Wireless sensor networks (WSNs) have gained a lot of attention recently due to the potential they provide for developing a plethora of cost-efficient applications. Although research on WSNs has been performed for more than a decade, only recently has the explosion of their potential applicability been identified. However, due to the fact that the wireless spectrum becomes congested in the unlicensed bands, there is a need for a next generation of WSNs, utilizing the advantages of cognitive radio (CR) technology for identifying and accessing the free spectrum bands. Thus, the next generation of wireless sensor networks is the cognitive wireless sensor networks (CWSNs). For the successful adoption of CWSNs, they have to be trustworthy and secure. Although the concept of CWSNs is quite new, a lot of work in the area of security and privacy has been done until now, and this work attempts to present an overview of the most important works for securing the CWSNs. Moreover, a discussion regarding open research issues is also given in the end of this work.

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  • 32.
    Franco, Antonio
    et al.
    Lund University, Sweden.
    Fitzgerald, Emma
    Lund University, Sweden.
    Landfeldt, Björn
    Lund University, Sweden.
    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.
    LUPMAC: A Cross-Layer MAC Technique to Improve the Age of Information Over Dense WLANs2016In: 2016 23RD INTERNATIONAL CONFERENCE ON TELECOMMUNICATIONS (ICT), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    Age of Information (AoI) is a relatively new metric introduced to capture the freshness of a particular piece of information. While throughput and delay measurements are widely studied in the context of dense IEEE 802.11 Wireless LANs (WLANs), little is known in the literature about the AoI in this context. In this work we study the effects on the average AoI and its variance when a sensor node is immersed in a dense IEEE 802.11 WLAN. We also introduce a new cross layer MAC technique, called Latest UPdate MAC (LUPMAC), aimed at modifying the existing IEEE 802.11 in order to minimize the average AoI at the receiver end. This technique lets the MAC layer keep only the most up to date packets of a particular piece of information in the buffer. We show, through simulation, that this technique achieves significant advantages in the case of a congested dense IEEE 802.11 WLAN, and it is resilient to changes in the variance of the total network delay.

  • 33.
    Fredriksson, Anna
    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.
    Eriksson, Daniel
    RISE, Göteborg, Sverige.
    Eriksson, Linnea
    VTI, Sverige.
    Gundlegård, David
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Lemon, Nina
    RISE, Göteborg, Sverige.
    Löwgren, Jonas
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Ringhdahl, Rasmus
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Sezer, Ahmet Anil
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Störningsfri stad: slutrapport i projektet Visualiserad byggtrafikplanering för en störningsfri stadsutveckling2022Report (Other academic)
    Abstract [sv]

    Störningsfri stad har kombinerat kunskaper inom Trafikplanering, Visualisering, Bygglogistik, Sensorer och Offentlig planering och styrning. Projektet har letts av Linköpings universitet, Institutionen för Teknik och Naturvetenskap och finansierats av Vinnova, IHS. Projektet har löpt mellan slutet av 2018 och 2021 ut. Projektdeltagare har varit VTI, RISE, Norrköpings kommun, Linköpings kommun, Stockholm stad, Uppsala kommun, Trafikverket Projekt Ostlänken, LE Lundbergs Fastigheter, Wiklunds Åkeri, Wellsec, SanktKors, Byggföretagen, Telenor och Logistikia.Projektet har utvecklat en verktygsprototyp som stöttar kollaborativ planering av byggtrafik och stadsplanering genom att visualisera pågående byggprojekts sammanlagda mängd transporter och var i staden (i form av en kartvy) det uppstår störningar i form av förseningar pga dessa. Verktyget bygger på en MATSim trafikmodell (i nuläget Norrköping) inkluderande både persontransporter (modellerat baserat på mobilnätsdata) och byggtrafik (modellerat baserat på data från bygglogistiklösningar). Med hjälp av verktyget kan olika scenarier för att minska störningarna av byggtransporter testas. För att stötta användandet av verktyget har en kollaborativ planeringsprocess som visar på hur de olika aktörerna involverade i planeringen av byggtransporter och stadsutveckling behöver interagera med varandra utvecklats. Projektet också deltagit i utvecklingen av en sensorbox (partiklar, luftfuktighet, temperatur och ljud) samt slangmätningsmetodik för att öka kunskapen om byggtransporter. Baserat på de resultat som projektet har behovsägarna har påbörjat arbeten med att bättre hantera de störningar som uppstår pga byggprojekt i staden.

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  • 34.
    Fredriksson, Anna
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Sezer, Ahmet Anil
    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.
    Gundlegård, David
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Construction related urban disturbances: Identification and linking with an IoT-model2022In: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 134, article id 104038Article in journal (Refereed)
    Abstract [en]

    While being a significant part of the urban development, construction projects disturb different stakeholders in various ways. There are three problems associated with construction disturbances: (i) most of these disturbances are not recognised by the people causing them, (ii) they are not monitored and (iii) if they are to be monitored, data is spread among stakeholders. This paper defines what a disturbance is, presents a list of disturbances, linking disturbances to stakeholders and, categorising them based on their distance from construction sites (responding to (i)). Next, a IoT domain model is developed, demonstrating how IoT in construction needs to be combined with the sensors of smart cities to capture the primitives of these disturbances (responding to (iii)). This is a first step towards enabling large-scale data-gathering of construction transport disturbances (responding to (ii)), which is a necessity to predict them and allow better construction transport planning to decrease disturbances.

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  • 35.
    Harrison, Katherine
    et al.
    Linköping University, Department of Thematic Studies, The Department of Gender Studies. Linköping University, Faculty of Arts and Sciences.
    Börütecene, Ahmet
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Löwgren, Jonas
    Linköping University, Department of Thematic Studies, The Department of Gender Studies. Linköping University, Faculty of Science & Engineering.
    Enlund, Desirée
    Linköping University, Department of Thematic Studies, The Department of Gender Studies. Linköping University, Faculty of Arts and Sciences.
    Ringdahl, Rasmus
    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.
    Sustainability means inclusivity: Engaging citizens in early stage smart city development2021In: PROCEEDINGS OF THE 2020 IEEE INTERNATIONAL SYMPOSIUM ON TECHNOLOGY AND SOCIETY (ISTAS), Institute of Electrical and Electronics Engineers (IEEE), 2021, p. 413-416Conference paper (Refereed)
    Abstract [en]

    The challenge of how cities can be designed and developed in an inclusive and sustainable direction is monumental. Smart city technologies currently offer the most promising solution for long-term sustainability. However, smart city projects have been criticised for ignoring diverse needs of the local population and increasing social divides. A sustainable urban environment depends as much on creating an inclusive space that is safe, accessible and comfortable for a diverse group of citizens as it does on deploying "smart" technologies for energy efficiency or environmental protection. This is because citizens will be more likely to adopt technologies promoting sustainability if they are well-aligned with their lived needs and experiences. In this paper, we present the rationale behind an ongoing interdisciplinary research project that aims to address exactly the problem outlined above by using a participatory design approach. Focusing on a smart city test site in Sweden where sensors are currently being deployed to collect data on noise, particles, vehicle numbers and types (amongst other), the goal is to bring local residents and government representatives into dialogue with technical developers by adopting a "meet-in-the-middle" approach. This paper comprises a brief presentation of early findings and a reflection on this approach.

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  • 36.
    Harrison, Katherine
    et al.
    Linköping University, Department of Thematic Studies, The Department of Gender Studies. Linköping University, Faculty of Arts and Sciences.
    Börütecene, Ahmet
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Löwgren, Jonas
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Enlund, Desirée
    Linköping University, Department of Thematic Studies, The Department of Gender Studies. Linköping University, Faculty of Arts and Sciences.
    Ringdahl, Rasmus
    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.
    Sustainability Means Inclusivity: Engaging Citizens in Early-Stage Smart City Development2021In: IEEE technology & society magazine, ISSN 0278-0097, E-ISSN 1937-416X, Vol. 40, no 3, p. 60-65Article in journal (Refereed)
    Abstract [en]

    The challenge of how cities can be designed and developed in an inclusive and sustainable direction is monumental. Smart city technologies currently offer the most promising solution for long-term sustainability, but the impact of such solutions will be significantly reduced without long-term, widespread adoption by citizens.

  • 37.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks2016In: IEEE Transactions on Control of Network Systems, E-ISSN 2325-5870, Vol. 3, no 3, p. 322-331Article in journal (Refereed)
    Abstract [en]

    We consider a wireless network with a set of transmitter-receiver pairs, or links, that share a common channel, and address the problem of emptying finite traffic volume from the transmitters in minimum time. This, so called, minimum-time scheduling problem has been proved to be NP-hard in general. In this paper, we study a class of minimum-time scheduling problems in which the link rates have a particular structure. We show that global optimality can be reached in polynomial time and derive optimality conditions. Then we consider a more general case in which we apply the same approach and obtain an approximation as well as lower and upper bounds to the optimal solution. Simulation results confirm and validate our approach.

  • 38.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Revisiting Minimum-Length Scheduling in Wireless Networks: An Algorithmic Framework2012In: International Symposium on Information Theory and its Applications (ISITA), 2012, Piscataway, NJ, USA: IEEE , 2012, p. 506-510Conference paper (Refereed)
    Abstract [en]

    We consider the problem of constructing the minimum length schedule required to empty a wireless network with queues of given size. In a recent work we have provided new fundamental insights towards its structure and complexity. Motivated by the problem computational complexity, we demonstrate here how a one-size-fits-all optimal algorithm cannot be expected and introduce a framework that decomposes the problem in two core sub-problems: Selecting which subset of wireless links to activate and for how long. This modular approach enables the construction of algorithms that can yield solutions ranging from simple and intuitive to exact optimal. We provide a comprehensive set of design strategies and results to elucidate how different combinations within the framework modules can be used to approach optimality.

  • 39.
    Klar, Robert
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Swedish Natl Rd & Transport Res Inst VTI, SE-58195 Linkoping, Sweden.
    Arvidsson, Niklas
    Swedish Natl Rd & Transport Res Inst VTI, SE-58195 Linkoping, Sweden.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Digital Twins' Maturity: The Need for Interoperability2023In: IEEE Systems Journal, ISSN 1932-8184, E-ISSN 1937-9234Article in journal (Refereed)
    Abstract [en]

    Digital twins have gained tremendous momentum since their conceptualization over 20 years ago, as more and more domains discover their value in driving efficiencies and reducing costs, while enabling technologies continue to advance. Originally aimed at product optimization and intelligent manufacturing, the range of applications for digital twins now spans entire complex, often highly interconnected systems such as ports, cities, and supply chains. Despite the increasing demand for sophisticated digital twinning solutions across all domains and scopes, their development is often still constrained by differing definitions, different understandings of their functional scope and design, and a lack of concrete methodology toward implementing a comprehensive digital twinning solution. Although there are already papers that evaluate the capabilities of existing digital twinning solutions on the basis of maturity levels, these usually consider the object to be twinned in isolation and are often domain-specific. With this article we address exactly this gap discussing how interoperability of digital twins can break physical boundaries of an isolated system, enabling system of systems joint optimization. We therefore consider interoperable digital twins to be the most mature twinning platforms, thus, we discuss in detail six digital twin maturity levels, departing from the interrelated contexts of ports, cities, and supply chains. Examples drawn from these domains demonstrate the need for interoperability toward optimizing processes and systems in realistic contexts, rather than in assumed isolation.

  • 40.
    Klar, Robert
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Swedish Natl Rd & Transport Res Inst VTI, SE-58195 Linkoping, Sweden.
    Fredriksson, Anna
    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.
    Digital Twins for Ports: Derived From Smart City and Supply Chain Twinning Experience2023In: IEEE Access, E-ISSN 2169-3536, Vol. 11, p. 71777-71799Article in journal (Refereed)
    Abstract [en]

    Ports are striving for innovative technological solutions to cope with the ever-increasing growth of transport, while at the same time improving their environmental footprint. An emerging technology that has the potential to substantially increase the efficiency of the multifaceted and interconnected port processes is the digital twin. Although digital twins have been successfully integrated in many industries, there is still a lack of cross-domain understanding of what constitutes a digital twin. Furthermore, the implementation of the digital twin in complex systems such as the port is still in its infancy. This paper attempts to fill this research gap by conducting an extensive cross-domain literature review of what constitutes a digital twin, keeping in mind the extent to which the respective findings can be applied to the port. It turns out that the digital twin of the port is most comparable to complex systems such as smart cities and supply chains, both in terms of its functional relevance as well as in terms of its requirements and characteristics. The conducted literature review, considering the different port processes and port characteristics, results in the identification of three core requirements of a digital port twin, which are described in detail. These include situational awareness, comprehensive data analytics capabilities for intelligent decision making, and the provision of an interface to promote multi-stakeholder governance and collaboration. Finally, specific operational scenarios are proposed on how the ports digital twin can contribute to energy savings by improving the use of port resources, facilities and operations.

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  • 41.
    Kosta, Antzela
    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.
    Age of Information: A New Concept, Metric, and Tool2017In: Foundations and Trends in Networking, ISSN 1554-057X, Vol. 12, no 3, p. 162-259Article in journal (Refereed)
    Abstract [en]

    Age of information (AoI) was introduced in the early 2010s as a notion to characterize the freshness of the knowledge a system has about a process observed remotely. AoI was shown to be a fundamentally novel metric of timeliness, significantly different, to existing ones such as delay and latency. The importance of such a tool is paramount, especially in contexts other than transport of information, since communication takes place also to control, or to compute, or to infer, and not just to reproduce messages of a source. This volume comes to present and discuss the first body of works on AoI and discuss future directions that could yield more challenging and interesting research.

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    Age of Information: A New Concept, Metric, and Tool
  • 42.
    Kosta, Antzela
    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.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Univ Maryland, MD 20742 USA.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Age and Value of Information: Non-linear Age Case2017Conference paper (Refereed)
    Abstract [en]

    We consider a real-time status update system consisting of a source-destination network. A stochastic process is observed at the source, and samples, so called status updates, are extracted at random time instances, and delivered to the destination. In this paper, we expand the concept of information ageing by introducing the Cost of Update Delay (CoUD) metric to characterize the cost of having stale information at the destination. We introduce the Value of Information of Update (VoIU) metric that captures the reduction of CoUD upon reception of an update. The importance of the VoIU metric lies on its tractability which enables an alternative performance criterion in status update systems.

    Download full text (pdf)
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  • 43.
    Kosta, Antzela
    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.
    Ephremides, Anthony
    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.
    Age of Information and Throughput in a Shared Access Network with Heterogeneous Traffic2018In: IEEE Global Telecommunications Conference (GLOBECOM), 2018, pp. 1-6., 2018Conference paper (Refereed)
    Abstract [en]

    We consider a cognitive shared access scheme consisting of a high priority primary node and a low priority network with N secondary nodes accessing the spectrum. Assuming bursty traffic at the primary node, saturated queues at the secondary nodes, and multipacket reception capabilities at the receivers, we derive analytical expressions of the time average age of information of the primary node and the throughput of the secondary nodes. We formulate two optimization problems, the first aiming to minimize the time average age of information of the primary node subject to an aggregate secondary throughput requirement. The second problem aims to maximize the aggregate secondary throughput of the network subject to a maximum time average staleness constraint. Our results provide guidelines for the design of a multiple access system with multipacket reception capabilities that fulfills both timeliness and throughput requirements.

  • 44.
    Kosta, Antzela
    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.
    Ephremides, Anthony
    Univ Maryland, MD 20742 USA.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Age of Information Performance of Multiaccess Strategies with Packet Management2019In: Journal of Communications and Networks, ISSN 1229-2370, E-ISSN 1976-5541, Vol. 21, no 3, p. 244-255Article in journal (Refereed)
    Abstract [en]

    We consider a system consisting of N source nodes communicating with a common receiver. Each source node has a buffer of infinite capacity to store incoming bursty traffic in the form of status updates transmitted in packets, which should maintain the status information at the receiver fresh. Packets waiting for transmission can be discarded to avoid wasting network resources for the transmission of stale information. We investigate the age of information (AoI) performance of the system under scheduled and random access. Moreover, we present analysis of the AoI with and without packet management at the transmission queue of the source nodes, where as packet management we consider the capability to replace unserved packets at the queue whenever newer ones arrive. Finally, we provide simulation results that illustrate the impact of the network operating parameters on the age performance of the different access protocols.

  • 45.
    Kosta, Antzela
    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.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Univ Maryland, MD 20742 USA.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Non-linear Age of Information in a Discrete Time Queue: Stationary Distribution and Average Performance Analysis2020In: ICC 2020 - 2020 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2020Conference paper (Refereed)
    Abstract [en]

    This paper considers a status update communication system consisting of a source-destination link with timeliness requirements. First, we study the properties of a sample path of the age of information (AoI) process at the destination. Under the assumption of ergodicity, we obtain a general formula of the stationary distribution of the AoI. We relate this result to a discrete time queueing system and provide a general expression of the generating function of AoI in relation with the system time and the peak age of information (PAoI). Furthermore, we consider the first-come-first-served (FCFS) Geo/Geo/1 queue and we obtain closed-form expressions of the generating functions and the stationary distributions of the AoI and the PAoI. We built upon these results to provide a methodology for analyzing general non-linear age functions for this type of systems.

  • 46.
    Kosta, Antzela
    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.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Univ Maryland, MD 20742 USA.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Queue Management for Age Sensitive Status Updates2019In: 2019 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY (ISIT), IEEE , 2019, p. 330-334Conference paper (Refereed)
    Abstract [en]

    We consider a system consisting of a source-destination communication link. At the transmitter of the source there is a buffer that stores packets containing status information. These randomly generated packets should keep the destination timely updated and they can be discarded to avoid wasting network resources for the transmission of stale information. In this setup, we provide an analysis of the age of information (AoI) and peak age of information (PAoI) performance of the system, with and without packet management at the transmission queue of the source node. The analysis indicates the potential performance gains obtained with the use of packet management.

  • 47.
    Kosta, Antzela
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Ericsson Res, Sweden.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Univ Maryland, MD 20740 USA; Univ Maryland, MD 20740 USA.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    The Age of Information in a Discrete Time Queue: Stationary Distribution and Non-Linear Age Mean Analysis2021In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 39, no 5, p. 1352-1364Article in journal (Refereed)
    Abstract [en]

    In this work, we investigate information freshness in a status update communication system consisting of a source-destination link. Initially, we study the properties of a sample path of the age of information (AoI) process at the destination. We obtain a general formula of the stationary distribution of the AoI, under the assumption of ergodicity. We relate this result to a discrete time queueing system and provide a general expression of the generating function of AoI in relation with the system time and the peak age of information (PAoI) metric. Furthermore, we consider three different single-server system models and we obtain closed-form expressions of the generating functions and the stationary distributions of the AoI and the PAoI. The first model is a first-come-first-served (FCFS) queue, the second model is a preemptive last-come-first-served (LCFS) queue, and the last model is a bufferless system with packet dropping. We build upon these results to provide a methodology for analyzing general non-linear age functions for this type of systems, using representations of functions as power series.

  • 48.
    Kosta, Antzela
    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.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Univ Maryland, MD 20740 USA; Univ Maryland, MD 20740 USA.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    The Cost of Delay in Status Updates and Their Value: Non-Linear Ageing2020In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 68, no 8, p. 4905-4918Article in journal (Refereed)
    Abstract [en]

    We consider a status update communication system consisting of a source-destination link. A stochastic process is observed at the source, where samples are extracted at random time instances, and delivered to the destination, thus, providing status updates for the source. In this paper, we expand the concept of information ageing by introducing the cost of update delay (CoUD) metric to characterize the cost of having stale information at the destination. The CoUD captures the freshness of the information at the destination and can be used to reflect the information structure of the source. Moreover, we introduce the value of information of update (VoIU) metric that captures the reduction of CoUD upon reception of an update. Using the CoUD, its by-product metric called peak cost of update delay (PCoUD), and the VoIU, we evaluate the performance of an M/M/1 system in various settings that consider exact expressions and bounds. The optimal server utilization policy is to minimize the time average CoUD and maximize the time average VoIU. Our results indicate that the performance of CoUD differs depending on the cost assigned per time unit, however the optimal policy remains the same for linear ageing and varies for non-linear ageing. When it comes to the VoIU the performance difference appears only when the cost increases non-linearly with time. The study illustrates the importance of the newly introduced variants of age, furthermore supported in the case of VoIU by its tractability.

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  • 49.
    Lei, Lei
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Performance analysis of chunk-based resource allocation in wireless OFDMA systems2012In: Proceedings from the 17th IEEE International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD), September 17-19, 2012, Barcelona, Spain, IEEE , 2012, p. 90-94Conference paper (Refereed)
    Abstract [en]

    In typical resource allocation for Orthogonal Frequency Division Multiple Access (OFDMA), assigning subcarriers to the more favorable users provides beneficial diversity and increased system performance. It is however relevant to consider OFDMA resource allocation with a subcarrier adjacency restriction, grouping a number of adjacent subcarriers into a chunk, both for physical design simplicity and for complexity mitigation. In this paper, we classify different resource allocation policies for chunk-based allocation. We investigate how to optimally allocate resources by using discrete rates and discrete power levels. This is enabled by developing binary integer optimization models to obtain the optimal solution for this comparative study. We present numerical results to evaluate the performance of different resource allocation policies under different parameters and scenarios.

  • 50.
    Li, Yuan
    et al.
    School of Computer, National University of Defense Technology, China.
    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.
    Pioro, Michal
    Institute of Telecommunications, Warsaw University of Technology, Poland.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    On the Resilient Network Design of Free Space Optical Wireless Network for Cellular Backhauling2016In: Optical Wireless Communications / [ed] Murat Uysal, Carlo Capsoni, Zabih Ghassemlooy, Anthony Boucouvalas, Eszter Udvary, Springer, 2016, p. 485-510Chapter in book (Refereed)
    Abstract [en]

    With the densification of nodes in cellular networks, free space optics (FSO) connections are becoming an appealing low cost and high rate alternative to copper and fiber backhaul solutions for wireless communication systems. To en- sure a reliable cellular backhaul, provisions for redundant, disjoint paths between the nodes must be made in the design phase. This chapter aims at finding a cost- effective solution to upgrade the cellular backhaul with pre-deployed optical fibers using FSO links and mirror components. A novel integer linear programming model to approach optimal FSO backhaul design, guaranteeing K-disjoint paths connecting each node pair is presented. Next, a column generation method to a path-oriented mathematical formulation is developed. Applying the method in a sequential man- ner enables high computational scalability. Realistic scenarios are used to demon- strate the proposed approaches which efficiently provide optimal or near-optimal solutions, and thereby allow for accurately dealing with the trade-off between cost and reliability. 

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