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  • 151.
    Astély, David
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    MLSE and Spatio-Temporal Interference Rejection Combining with Antenna Arrays1998In: Proceedings of Eusipco-98, Ninth European Signal Processing Conference, Island of Rhodes, Greece, 1998, p. 1341-1344Conference paper (Refereed)
  • 152.
    Athanasiou, George
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Weeraddana, Pradeep Chathuranga
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Orten, P.
    Communication infrastructures in industrial automation: The case of 60 GHz millimeterWave communications2013In: IEEE International Conference on Emerging Technologies and Factory Automation, ETFA, 2013Conference paper (Refereed)
    Abstract [en]

    Wireless sensor networks for industrial automation applications must offer timely, reliable, and energy efficient communications at both low and high data rate. While traditional communication technologies between 2.4 GHz and 5 GHz are sometimes incapable to efficiently achieve the aforementioned goals, new communication strategies are emerging, such as millimeterWave communications. In this overview paper, the general requirements that factory and process automation impose on the network design are reviewed. Moreover, this paper presents and qualitatively evaluates the 60 GHz millimeterWave communication technology for automation. It is argued that the upcoming 60 GHz millimeterWave technology brings an enormous potential and can influence the design of the future communication infrastructures in factory and process automation.

  • 153.
    Athanasiou, Georgios
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Weeraddana, Pradeep Chathuranga
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Auction-Based Resource Allocation in MillimeterWave Wireless Access Networks2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 11, p. 2108-2111Article in journal (Refereed)
    Abstract [en]

    The resource allocation problem of optimal assignment of the stations to the available access points in 60 GHz millimeterWave wireless access networks is investigated. The problem is posed as a multi-assignment optimization problem. The proposed solution method converts the initial problem to a minimum cost flow problem and allows to design an efficient algorithm by a combination of auction algorithms. The solution algorithm exploits the network optimization structure of the problem, and thus is much more powerful than computationally intensive general-purpose solvers. Theoretical and numerical results evince numerous properties, such as optimality, convergence, and scalability in comparison to existing approaches.

  • 154.
    Athanasiou, Georgios
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Weeraddana, Pradeep Chathuranga
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Tassiulas, Leandros
    University of Thessaly, Volos, Greece.
    Optimizing Client Association for Load Balancing and Fairness in Millimeter Wave Wireless Networks2015In: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 23, no 3, p. 836-850Article in journal (Refereed)
    Abstract [en]

    Millimeter-wave communications in the 60-GHz band are considered one of the key technologies for enabling multigigabit wireless access. However, the special characteristics of such a band pose major obstacles to the optimal utilization of the wireless resources, where the problem of efficient client association to access points (APs) is of vital importance. In this paper, the client association in 60-GHz wireless access networks is investigated. The AP utilization and the quality of the rapidly vanishing communication links are the control parameters. Because of the tricky non-convex and combinatorial nature of the client association optimization problem, a novel solution method is developed to guarantee balanced and fair resource allocation. A new distributed, lightweight, and easy-to-implement association algorithm, based on Lagrangian duality theory and subgradient methods, is proposed. It is shown that the algorithm is asymptotically optimal, that is, the relative duality gap diminishes to zero as the number of clients increases.

  • 155.
    Atiiq, Syafiq Al
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Adaptive Counteraction Against Denial of Service Attack2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Internet of Things (IoT) is the next generation of networked society where billions of, everyday-life, devices are directly connected to the Internet and able to communicate with each other. In particular, the Constrained Application Protocol (CoAP) has become the de-facto IoT standard for communication at the application layer, as a lightweight web transfer protocol affordable also for resource-constrained platforms. However, as IoT devices are directly connected to the Internet, they are especially vulnerable to a number of security attacks including Denial of Service (DoS), which can seriously worsen their performance and responsiveness, and even make them totally unavailable to serve legitimate requests.

    In this Master's Thesis project, we have developed a cross-layer and context-aware approach that adaptively counteracts DoS attacks against CoAP server devices, by dynamically adjusting their operative state according to the attack intensity. This considerably limits the impact of DoS attacks and preserves service availability of victim devices to the best possible extent. The proposed approach leverages a trusted Proxy that adaptively shields victim devices, while effectively forwarding and caching messages if needed. We have made a proof-of-concept implementation of our solution for the Californium framework and the CoAP protocol, and experimentally evaluated its effectiveness in counteracting DoS and preserving availability of devices under attack.

    This Master's Thesis project has been conducted in collaboration with RISE SICS, a research institute for applied information and communication technology in Sweden.

  • 156.
    Augustian, Midhumol
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    ur Réhman, Shafiq
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Sandvig, Axel
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience. Norwegian University of Science and Technology (NTNU), Norway.
    Kotikawatte, Thivra
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Yongcui, Mi
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Evensmoen, Hallvard Røe
    Norwegian University of Science and Technology (NTNU), Norway.
    EEG Analysis from Motor Imagery to Control a Forestry Crane2018In: Intelligent Human Systems Integration (IHSI 2018) / [ed] Karwowski, Waldemar, Ahram, Tareq, 2018, Vol. 722, p. 281-286Conference paper (Refereed)
    Abstract [en]

    Brain-computer interface (BCI) systems can provide people with ability to communicate and control real world systems using neural activities. Therefore, it makes sense to develop an assistive framework for command and control of a future robotic system which can assist the human robot collaboration. In this paper, we have employed electroencephalographic (EEG) signals recorded by electrodes placed over the scalp. The human-hand movement based motor imagery mentalization is used to collect brain signals over the motor cortex area. The collected µ-wave (8–13 Hz) EEG signals were analyzed with event-related desynchronization/synchronization (ERD/ERS) quantification to extract a threshold between hand grip and release movement and this information can be used to control forestry crane grasping and release functionality. The experiment was performed with four healthy persons to demonstrate the proof-of concept BCI system. From this study, it is demonstrated that the proposed method has potential to assist the manual operation of crane operators performing advanced task with heavy cognitive work load.

  • 157.
    Augustine, Robin
    Uppsala University.
    BAN Antenna Design Using Ferrite Polymer Composite2009Conference paper (Refereed)
  • 158.
    Augustine, Robin
    Uppsala University.
    Biocompatibility study of biphasic-chitosan-soyameal composite Bioceramic Implants and their use as Phantoms for Medical Imaging. Applications2008Conference paper (Refereed)
  • 159. Augustine, Robin
    Biocompatibility study of hydroxy apatite and chitosan composites for applications at microwave frequencies2010In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 46, no 3, p. 197-199Article in journal (Refereed)
    Abstract [en]

    Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) bioceramic and chitosan (poly [(β-1-4) d-glucosamine]) biopolymer show good biocompatibility in vivo. They have biological origin and show excellent interactions with microwave. Microwave study of HAp made using different drying techniques and their composites with chitosan in the ISM band is presented. Pastes are made using HAp and chitosan with different ratios of mixing. The dielectric properties of this composites match with that of human fat, collagen tissues. Some of the compositions exhibit dielectric property close to that of natural bone. This makes them more biocompatible and better substitutes for natural bone. Thus composite bioceramics can be considered as phantom model constituents for imaging purposes. Their dielectric properties prove that they are biocompatible. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2931–2934, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23806

  • 160.
    Augustine, Robin
    Uppsala University.
    Dielectric Studies of Calcium Hydroxyapatite at Microwave Frequency2005Conference paper (Refereed)
  • 161. Augustine, Robin
    Développement d’un modèle humain dans la bande millimétrique pour les applications2011Conference paper (Refereed)
  • 162.
    Augustine, Robin
    Université Paris-Est.
    Electromagnetic modelling of human tissues and its application on the interaction between antenna and human body in the BAN context2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this age of wireless technology, Body Area networks (BAN) is revolutionising the concept of patient care and health monitoring. BAN provides people good assessment of their health status at any time, wherever they are physically. The increased interest in developing effective body (in, on & off) communication systems made phantoms which can mimic the electrical properties of an actual human body necessary. Wearable antennas which are the indispensable part of BAN got to be low pro file and above all influences that human body can make. There should also be a way to reduce the effect of antennas on human body namely specific absorption rate (SAR). In this work effort has been made to develop phantoms suitable for both On body and In body communications. The base materials which are selected for the study are of biological origin (bio ceramics and biopolymers) whose behaviour is closer to that of human tissues. As these phantoms are biocompatible they are essentially non toxic where the conventionally available phantoms are toxic in nature. Different kinds of low profile conformal wearable antennas working at 2.4GHz ISM band were developed and studied in the BAN perspective. Antennas suffer much in terms of matching and efficiency when they are in contact or in the premises of human body. This is a major hurdle in the way to setting up a good body communication network. This work encompasses various techniques adopted to limit the body interferences to an acceptable level. The techniques adopted (Such as Backing Ground Plane, High Impedance Surface & Polymeric Ferrite Sheets) proved to be effective in reducing the sway in antenna characteristics when they are mounted on body. Specific absorption rate is also brought to acceptable levels and thus avoiding the formation of hot spots due to microwave absorption. A safer and cost effective BAN can be set up using this work which will lead to a safer, mobile and healthy future.

  • 163. Augustine, Robin
    Permittivity Spectra of Biological Solutions in the Millimeter-Wave Range at Room andHuman Body Temperatures2011Conference paper (Refereed)
  • 164.
    Augustine, Robin
    Uppsala University.
    SAR reduction of wearable antennas using polymeric ferrite sheets2010Conference paper (Refereed)
  • 165.
    Augustine, Robin
    Uppsala University.
    Topology Optimization of Wideband Directive Antennas2015In: Progress in Electromagnetics Research, Vol. 2A1, no SC4, p. 636-639Article in journal (Refereed)
  • 166.
    Augustine, Robin
    Uppsala University.
    Wide Band Impedance matching For Transducers2005Conference paper (Refereed)
  • 167. Augustine, Robin
    et al.
    Thierry, Alves
    Sarrebourse, T.
    Poussot, B.
    Mathew, K. T.
    Laheurte, J. -M.
    Polymeric ferrite sheats for SAR reduction of Wearable ANtennas2010In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 46, no 3, p. 197-198Article in journal (Refereed)
    Abstract [en]

    Reduction of specific absorption rate (SAR) has now become a buzz word because of the growing health concerns over microwave exposure. Ferrites are found to be effective in diminishing electromagnetic influence. In this reported work, flexible polymeric ferrite sheets are characterised on the basis of their shielding efficiencies. SAR measurements are carried out with a planar wearable antenna and polymeric ferrite shielding to confirm its competence.

  • 168.
    Aujla, Gagangeet Singh
    et al.
    Thapar University, Patiala, India.
    Chaudhary, Rajat
    Thapar University, Patiala, India.
    Kumar, Neeraj
    Thapar University, Patiala, India.
    Rodrigues, Joel J. P. C.
    National Institute of Telecommunications (Inatel), Santa Rita do Sapucaí, Brazil; University of Beira Interior, Covilhã, Portugal; ITMO University, St. Petersburg, Russia; University of Fortaleza (Unifor), Fortaleza, Brazil.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Data Offloading in 5G-Enabled Software-Defined Vehicular Networks: A Stackelberg-Game-Based Approach2017In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 55, no 8, p. 100-108Article in journal (Refereed)
    Abstract [en]

    Data offloading using vehicles is one of the most challenging tasks to perform due to the high mobility of vehicles. There are many solutions available for this purpose, but due to the inefficient management of data along with the control decisions, these solutions are not adequate to provide data offloading by making use of the available networks. Moreover, with the advent of 5G and related technologies, there is a need to cope with high speed and traffic congestion in the existing infrastructure used for data offloading. Hence, to make intelligent decisions for data offloading, an SDN-based scheme is presented in this article. In the proposed scheme, an SDNbased controller is designed that makes decisions for data offloading by using the priority manager and load balancer. Using these two managers in SDN-based controllers, traffic routing is managed efficiently even with an increase in the size of the network. Moreover, a single-leader multi-follower Stackelberg game for network selection is also used for data offloading. The proposed scheme is evaluated with respect to several parameters where its performance was found to be superior in comparison to the existing schemes. © Copyright 2017 IEEE

  • 169.
    Avazkonandeh Gharavol, Ebrahim
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Robust Joint Optimization of MIMO Interfering Relay Channels with Imperfect CSI2011In: 2001 4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP), Piscataway, NJ, USA: IEEE , 2011, , p. 5p. 209-212Conference paper (Refereed)
    Abstract [en]

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

  • 170.
    Avazkonandeh Gharavol, Ebrahim
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Robust Joint Optimization of Non-regenerative MIMO Relay Channels with Imperfect CSI2011In: Conference Record of the Forty Fifth Asilomar Conference on Signals, Systems and Computers (ASILOMAR), 2011, IEEE Computer Society, 2011, p. 1589-1593Conference paper (Refereed)
    Abstract [en]

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

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

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

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

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

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

    Finally simulation results assess the performance of the proposed scheme.

  • 171.
    Avazkonandeh Gharavol, Ebrahim
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    The Sign-Definiteness Lemma and Its Applications to Robust Transceiver Optimization for Multiuser MIMO Systems2013In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 61, no 2, p. 238-252Article in journal (Refereed)
    Abstract [en]

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

  • 172.
    Avesand (nee Sjöquist), Stefan
    KTH, Superseded Departments, Teleinformatics. KTH, School of Information and Communication Technology (ICT).
    Secure Database Access in Java Applets1998Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    For many years the web has only been used as a way ofdistributing information, but the need for more interaction isgrowing stronger. To accomplish this one can use Javaapplets, HTML forms, Active X, Javascript and a few othertechniques. One problem is that you must store the data theusers create, and change, somewhere and somehow. As thetitle reveals, this thesis will analyze a few ways to do this inJava applets.

  • 173.
    Avgeropoulos, Konstantinos
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Service Policy Management for User-Centric Services in Heterogeneous Mobile Networks,2004Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Session Initiation Protocol (SIP) is a signaling protocol for IP-based media services that will be the de facto standard for future media-over-IP services. Since SIP User Agents (UAs) support a limited number of service types (usually one or two), we assume that the future user will need to operate several UAs simultaneously. These UAs will constitute the user's personal service network. In this thesis, we investigate architectures for policy-based management of this network so that it can be used in an efficient manner. To achieve this, we propose a new SIP entity, called the SIP Service Manager (SSM), which lies in the core of the management system. Finally, we evaluate our proposal by implementing one version of the SIP Service Manager.

  • 174.
    Avgouleas, Ioannis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    IoT Networking Resource Allocation and Cooperation2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

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

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

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

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

  • 175.
    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.

  • 176.
    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: IEEE 28th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC): Workshop on "Communications for Networked Smart Cities", IEEE conference proceedings, 2017Conference 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.

  • 177.
    Avni, G.
    et al.
    IST Austria, Klosterneuburg, Austria.
    Goel, S.
    IIT Bombay, Mumbai, India.
    Henzinger, T. A.
    IST Austria, Klosterneuburg, Austria.
    Rodriguez-Navas, Guillermo
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Computing scores of forwarding schemes in switched networks with probabilistic faults2017In: Lecture Notes in Computer Science, Volume 10206, Springer Verlag , 2017, p. 169-187Conference paper (Refereed)
    Abstract [en]

    Time-triggered switched networks are a deterministic communication infrastructure used by real-time distributed embedded systems. Due to the criticality of the applications running over them, developers need to ensure that end-to-end communication is dependable and predictable. Traditional approaches assume static networks that are not flexible to changes caused by reconfigurations or, more importantly, faults, which are dealt with in the application using redundancy. We adopt the concept of handling faults in the switches from non-real-time networks while maintaining the required predictability. We study a class of forwarding schemes that can handle various types of failures. We consider probabilistic failures. For a given network with a forwarding scheme and a constant ℓ, we compute the score of the scheme, namely the probability (induced by faults) that at least ℓ messages arrive on time. We reduce the scoring problem to a reachability problem on a Markov chain with a “product-like” structure. Its special structure allows us to reason about it symbolically, and reduce the scoring problem to #SAT. Our solution is generic and can be adapted to different networks and other contexts. Also, we show the computational complexity of the scoring problem is #P-complete, and we study methods to estimate the score. We evaluate the effectiveness of our techniques with an implementation.

  • 178.
    Axberg, Stefan
    et al.
    Swedish National Defence College.
    Brynielsson, Joel
    Swedish National Defence College.
    Norsell, Martin
    Swedish National Defence College.
    A Sensor Concept for Superior Surveillance2007In: Proceedings of the Ninth International Symposium on Protection against Chemical and Biological Warfare Agents, 2007Conference paper (Refereed)
    Abstract [en]

    A highly developed aerial surveillance concept is presented. When fully implemented, the outlined surveillance system enhances situational awareness in two ways: it enhances the overall situational awareness in a large, possibly multinational, area and it provides the possibility to gain additional awareness in critical sites. The system is intended to be beneficial within various kinds of crisis management situations, e.g., disaster relief situations, humanitarian crises, chemical discharges, etc. In particular, the combination of large-area coverage with the possibility to instantly gain local situational awareness is believed to allow for pan-European collaboration and interoperability. Another targeted area includes critical ground sites such as ground transportation and infrastructure. The proposed concept uses surveillance at different altitudes and passes on near real-time information to a variety of end users through its embedded sensor and communications architecture.

  • 179.
    Axell, Erik
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Spectrum Sensing Algorithms Based on Second-Order Statistics2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

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

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

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

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

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

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

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

  • 180.
    Axell, Erik
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Multiantenna Spectrum Sensing of a Second-Order Cyclostationary Signal2011In: Proceedings of the 4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP'11), 2011, p. 329-332Conference paper (Refereed)
    Abstract [en]

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

  • 181.
    Axelsson, Andreas
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Ambrosius, Christian
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Nya lagar och avtal: Hur kan de komma att förändra svenskarnas fildelningsvanor?2012Independent thesis Basic level (university diploma), 5 credits / 7,5 HE creditsStudent thesis
    Abstract [sv]

    I många år nu har det varit vanligt förekommande att människor suttit hemma vid sin dator och med några få klick laddat ner filmer, musik och programvaror, till en början helt lagligt, men med åren har lagar kommit till som har gjort det mer och mer olagligt.Oavsett om det har varit lagligt eller inte, så är det troligt att många artister, filmmakare och liknande gått miste om stora summor pengar i förlorade inkomster på grund av att folk inte har betalat för att ta del av deras verk, utan istället valt att ladda ner dem över Internet.

    Det faktum att fildelning har blivit så pass vanligt och att folk inte har sett det som ett särskilt allvarligt brott, har lett till att fildelning länge har varit ett hett omdiskuterat ämne i media, bland upphovsrättsinnehavare och bland folk i allmänhet. Upphovsmän och upphovsrättsinnehavare, såsom filmbolag, författare och artister har legat på och debatterat för att försöka få till en hårdare lagstiftning för att försvåra fildelning och kopiering av upphovsrättsskyddat material, samt för att få till hårdare straff mot fildelning.

    Flera försök från beslutsfattare har gjorts för att råda bot på problemet, nya lagar har stiftats och avtal har skrivits under. Frågan är om de nya lagarna och avtalen gör någon nytta? Blir folk avskräckta från att fildela eller fortsätter de som förut? Många har säkert under många år blivit bortskämda med att kunna sitta hemma vid datorn och på några minuter få hem de senaste filmerna och den nyaste musiken helt gratis, vilket säkert gör det svårt att helt plötsligt sluta fildela och börja betala för film och musik igen.

  • 182.
    Axelsson, Johannes
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    WAN-optimering för sjöfarten: En möjlighet att effektivisera datakommunikationen till sjöss2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Shipboard operations have become more reliant of data communication and many of the duties on board may be facilitated if the crew can access information stored elsewhere. The broadband connection between ship and shore is mostly done via satellite communication where long distances and limited data rate results in inefficient data communication. This study examines network optimization and the performance improvement this can have regarding slow WAN connections via satellite. The survey showed that the biggest issue with data communication via satellite is the signal delay caused by the long transmission distance which means that there will be performance degradation for data traffic and users will experience the data communication as slow. To solve this there is equipment that enhances the performance of the connection and handles the data communication by implementing various techniques. To investigate how much the performance improvement can be this study carried out a number of experiments with network optimization equipment.  The experiments evaluated file transfer with and without network optimization. The results show that the network optimization gives a major performance improvement regarding file transfer.

  • 183.
    Ayrault, Cécile
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Service discovery for Personal Area Networks2004Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the increasing use of electronic devices, the need for affordable wireless services specifically context-aware services, in a so-called Personal Area Network (PAN) is becoming an area with significant potential. Service discovery is a basic function.

    Even though a number of service discovery protocols have been implemented, a specific protocol for a PAN environment may need to be developed, as the characteristics of a PANs differ from other networking environments. Thus, the specific requirements for service discovery from a PAN perspective were studied. Methods for service discovery will be described that take into account both local and remote services.

    These methods will then be evaluated in a SIP telephony infrastructure to decide where a call should be delivered. The location of a person is done by using the implemented service discovery.

  • 184.
    Ayyagari, Nitin Reddy
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Databases For Mediation Systems: Design and Data scaling approach2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Context: There is continuous growth in data generation due to wide usage of modern communication systems. Systems have to be designed which can handle the processing of these data volumes efficiently. Mediation systems are meant to serve this purpose. Databases form an integral part of the mediation systems. Suitability of the databases for such systems is the principle theme of this work.

    Objectives: The objective of this thesis is to identify the key requirements for databases that can be used as part of Mediation systems, gain a thorough understanding of various features, the data models commonly used in databases and to benchmark their performance.

    Methods: Previous work that has been carried out on various databases is studied as a part of literature review. Test bed is set up as a part of experiment and performance metrics such as throughput and total time taken were measured through a Java based client. Thorough analysis has been carried out by varying various parameters like data volumes, number of threads in the client etc.

    Results: Cassandra has a very good write performance for event and batch operations. Cassandra has a slightly better read performance when compared to MySQL Cluster but this differentiation withers out in case of fewer number of threads in the client.

    Conclusions: On evaluation of MySQL Cluster and Cassandra we conclude that they have several features that are suitable for mediation systems. On the other hand, Cassandra does not guarantee ACID transactions while MySQL Cluster has good support. There is need for further evaluation on new generation databases which are not mature enough as of now.

  • 185.
    Azari, Amin
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Energy Efficient Machine-Type Communications over Cellular Networks: A Battery Lifetime-Aware Cellular Network Design Framework2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Internet of Things (IoT) refers to the interconnection of uniquely identifiable smart devices which enables them to participate more actively in everyday life. Among large-scale applications, machine-type communications (MTC) supported by cellular networks will be one of the most important enablers for the success of IoT. The existing cellular infrastructure has been optimized for serving a small number of long-lived human-oriented communications (HoC) sessions, originated from smartphones whose batteries are charged in a daily basis. As a consequence, serving a massive number of non-rechargeable machine-type devices demanding a long battery lifetime is a big challenge for cellular networks.

    The present work is devoted to energy consumption modeling, battery lifetime analysis, and lifetime-aware network design for massive MTC services over cellular networks. At first, we present a realistic model for energy consumption of machine devices in cellular connectivity, which is employed subsequently in deriving the key performance indicator, i.e. network battery lifetime. Then, we develop an efficient mathematical foundation and algorithmic framework for lifetime-aware clustering design for serving a massive number of machine devices. Also, by extending the developed framework to non-clustered MTC, lifetime-aware uplink scheduling and power control solutions are derived. Finally, by investigating the delay, energy consumption, spectral efficiency, and battery lifetime tradeoffs in serving coexistence of HoC and MTC traffic, we explore the ways in which energy saving for the access network and quality of service for HoC traffic can be traded to prolong battery lifetime for machine devices.

    The numerical and simulation results show that the proposed solutions can provide substantial network lifetime improvement and network maintenance cost reduction in comparison with the existing approaches.

  • 186.
    Azari, Amin
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Energy-efficient scheduling and grouping for machine-type communications over cellular networks2016In: Ad hoc networks, ISSN 1570-8705, E-ISSN 1570-8713, Vol. 43, p. 16-29Article in journal (Refereed)
    Abstract [en]

    In this paper, energy-efficient scheduling for grouped machine-type devices deployed in cellular networks isinvestigated. We introduce a scheduling-based cooperation incentivescheme which enables machine nodes to organize themselveslocally, create machine groups, and communicate through grouprepresentatives to the base station. This scheme benefits from anovel scheduler design which takes into account the cooperationlevel of each node, reimburses the extra energy consumptionsof group representatives, and maximizes the network lifetime.As reusing cellular uplink resources for communications insidethe groups degrades the Quality of Service (QoS) of theprimary users, analytical results are provided which present atradeoff between maximum allowable number of simultaneouslyactive machine groups in a given cell and QoS of the primaryusers. Furthermore, we extend our derived solutions for theexisting cellular networks, propose a cooperation-incentive LTEscheduler, and present our simulation results in the context ofLTE. The simulation results show that the proposed solutionssignificantly prolong the network lifetime. Also, it is shown thatunder certain circumstances, reusing uplink resource by machinedevices can degrade the outage performance of the primary userssignificantly, and hence, coexistence management of machinedevices and cellular users is of paramount importance for nextgenerations of cellular networks in order to enable group-basedmachine-type communications while guaranteeing QoS for theprimary users.

  • 187.
    Azari, Amin
    et al.
    Wireless Multimedia Communications Laboratory, Center of Excellence on Applied Electromagnetic Systems, University of Tehran, Iran .
    Harsini, Jalil
    Lahouti, Farshad
    Performance Analysis of Ad-Hoc Routing in Heterogeneous Clustered Multi-hop Wireless Networks2015In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 80, p. 144-154Article in journal (Refereed)
    Abstract [en]

    This paper analyzes the performance of clustered decode-and-forward multi-hop relaying (CDFMR) wireless Rayleigh fading networks, and sheds light on their design principles for energy and spectral efficiency. The focus is on a general performance analysis (over all SNR range) of heterogeneous wireless networks with possibly different numbers of relays in clusters of various separations. For clustered multi-hop relaying systems, hop-by-hop routing is known as an efficient decentralized routing algorithm which selects the best relay node in each hop using local channel state information. In this article, we combine hop-by-hop routing and cooperative diversity in CDFMR systems, and we derive (i) a closed-form expression for the probability distribution of the end-to-end SNR at the destination node; (ii) the system symbol error rate (SER) performance for a wide class of modulation schemes; and (iii) exact analytical expressions for the system ergodic capacity, the outage probability and the achievable probability of the SNR (power) gain. We also provide simple analytical asymptotic expressions for SER and the outage probability in high SNR regime. Numerical results are provided to validate the correctness of the presented analyses.

  • 188.
    Azari, Amin
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Battery Lifetime-Aware Base Station Sleeping Control with M2M/H2H Coexistence2016In: 2016 IEEE Global Communications Conference, GLOBECOM 2016 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7841624Conference paper (Refereed)
    Abstract [en]

    Fundamental tradeoffs in green cellular networkswith coexistence of machine-oriented and human-oriented trafficsare investigated. First, we present a queuing system to modelthe uplink transmission of a green base station which servestwo types of distinct traffics with strict requirements on delayand battery lifetime. Then, the energy-lifetime and energydelaytradeoffs are introduced, and closed-form expressions forenergy consumption of the base station, average experienceddelay in data transmission, and expected battery lifetime ofmachine devices are derived. Furthermore, we extend the derivedresults to the multi-cell scenario, and investigate the impacts ofsystem and traffic parameters on the energy-lifetime and energydelaytradeoffs using analytical and numerical results. Numericalresults show the impact of energy saving for the access network onthe introduced tradeoffs, and figure out the ways in which energycould be saved by compromising on the level of performance.

  • 189.
    Azari, Amin
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Energy Efficient MAC for Cellular-Based M2M Communications2014In: Signal and Information Processing (GlobalSIP), 2014 IEEE Global Conference on, IEEE conference proceedings, 2014, p. 128-132Conference paper (Refereed)
    Abstract [en]

    In Machine-to-Machine (M2M) networks, an energyefficient scalable medium access control (MAC) is crucial forserving massive battery-driven machine-type devices. In thispaper, we investigate the energy efficient MAC design to minimizebattery power consumption in cellular-based M2M communications.We present an energy efficient MAC protocol that notonly adapts contention and reservation-based protocols for M2Mcommunications in cellular networks, but also benefits frompartial clustering to handle the massive access problem. Then weinvestigate the energy efficiency and access capacity of contentionbasedprotocols and present an energy efficient contention-basedprotocol for intra-cluster communication of the proposed MAC,which results in huge power saving. The simulation results showthat the proposed MAC protocol outperforms the others in energysaving without sacrificing much delay or throughput. Also, thelifetimes of both individual nodes and the whole M2M networkare significantly extended.

  • 190.
    Azari, Amin
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Fundamental Tradeoffs in Resource Provisioning forIoT Services over Cellular Networks2017In: Proceedings of the 2017 IEEE International Conference on Communications, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7996885Conference paper (Refereed)
    Abstract [en]

    Performance tradeoffs in resource provisioningfor mixed internet-of-things (IoT) and human-orientedcommunications(HoC) services over cellular networks are investigated.First, we present a low-complexity model of cellularconnectivity in the uplink direction in which both accessreservation and scheduled data transmission procedures areincluded. This model is employed subsequently in derivinganalytical expressions for energy efficiency, spectral efficiency,and experienced delay in data transmission of connected devicesas well as energy consumption of base stations. The derivedexpressions indicate that the choice of uplink resource provisioningstrategy introduces tradeoffs between battery lifetime forIoT communications, quality of service (QoS) for HoC, spectralefficiency and energy consumption for the access network. Then,the impacts of system and traffic parameters on the introducedtradeoffs are investigated. Performance analysis illustrates thatimproper resource provisioning for IoT traffic not only degradesQoS of high-priority services and decreases battery lifetime ofIoT devices, but also increases energy consumption of the accessnetwork. The presented analytical and simulations results figureout the ways in which spectral/energy efficiency for the accessnetwork and QoS for high-priority services could be traded toprolong battery lifetimes of connected devices by compromisingon the level of provisioned radio resources.

  • 191.
    Azari, Amin
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Lifetime-Aware Scheduling and Power Control for Cellular-based M2M Communications2015In: Wireless Communications and Networking Conference (WCNC), 2015 IEEE: , IEEE conference proceedings, 2015, p. 1171-1176Conference paper (Refereed)
    Abstract [en]

    In this paper the uplink scheduling and transmit powercontrol is investigated to minimize the energy consumption forbattery-driven devices deployed in cellular networks. A lifetimemetric based on the accurate energy consumption model for cellularbasedmachine devices is provided and used to formulate theuplink scheduling and power control problems as network lifetimemaximization problems. Then, lifetime-aware uplink scheduling andpower control protocols which maximize the overall network lifetimeare investigated based on the different lifetime definitions. Besidesthe exact solutions, the low-complexity suboptimal solutions arepresented in this work which can achieve near optimal performancewith much lower computational complexity. The performance evaluationshows that the network lifetime is significantly extended underproposed protocols.

  • 192.
    Azari, Amin
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Lifetime-Aware Scheduling and Power Control for M2M Communications in LTE Networks2015In: Vehicular Technology Conference (VTC Spring), 2015 IEEE 81st, IEEE conference proceedings, 2015Conference paper (Refereed)
    Abstract [en]

    In this paper the scheduling and transmit powercontrol are investigated to minimize the energy consumptionfor battery-driven devices deployed in LTE networks. To enableefficient scheduling for a massive number of machine-typesubscribers, a novel distributed scheme is proposed to let machinenodes form local clusters and communicate with the base-stationthrough the cluster-heads. Then, uplink scheduling and powercontrol in LTE networks are introduced and lifetime-aware solu-tions are investigated to be used for the communication betweencluster-heads and the base-station. Beside the exact solutions,low-complexity suboptimal solutions are presented in this workwhich can achieve near optimal performance with much lowercomputational complexity. The performance evaluation showsthat the network lifetime is significantly extended using theproposed protocols.

  • 193.
    Azari, Amin
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Network Life time Maximization for Cellular-Based M2M Networks2017In: IEEE Access, E-ISSN 2169-3536, Vol. 5, p. 18927-18940, article id 8045999Article in journal (Refereed)
    Abstract [en]

    High energy efficiency is critical for enabling massive machine-type communications (MTC) over cellular networks. This paper is devoted to energy consumption modeling, battery lifetime analysis, lifetime-aware scheduling, and transmit power control for massive MTC over cellular networks. We consider a realistic energy consumption model for MTC and model network battery-lifetime. Analytic expressions are derived to demonstrate the impact of scheduling on both the individual and network battery lifetimes. The derived expressions are subsequently employed in the uplink scheduling and transmit power control for mixed-priority MTC traffic in order to maximize the network lifetime. Besides the main solutions, low complexity solutions with limited feedback requirement are investigated, and the results are extended to existing LIE networks. In addition, the energy efficiency, spectral efficiency, and network lifetime tradeoffs in resource provisioning and scheduling for MTC over cellular networks are investigated. The simulation results show that the proposed solutions can provide substantial network lifetime improvement and network maintenance cost reduction in comparison with the existing scheduling schemes.

  • 194.
    Azari, Amin
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Network Lifetime Maximization for Cellular-Based M2M Networks2017In: IEEE Access, E-ISSN 2169-3536Article in journal (Refereed)
    Abstract [en]

    High energy efficiency is critical for enabling massivemachine-type communications (MTC) over cellular networks.This work is devoted to energy consumption modeling,battery lifetime analysis, lifetime-aware scheduling and transmitpower control for massive MTC over cellular networks. Weconsider a realistic energy consumption model for MTC andmodel network battery-lifetime. Analytic expressions are derivedto demonstrate the impact of scheduling on both the individualand network battery lifetimes. The derived expressions aresubsequently employed in uplink scheduling and transmit powercontrol for mixed-priority MTC traffic in order to maximizethe network lifetime. Besides the main solutions, low-complexitysolutions with limited feedback requirement are investigated,and the results are extended to existing LTE networks. Also,the energy efficiency, spectral efficiency, and network lifetimetradeoffs in resource provisioning and scheduling for MTC overcellular networks are investigated. The simulation results showthat the proposed solutions can provide substantial networklifetime improvement and network maintenance cost reductionin comparison with the existing scheduling schemes.

  • 195.
    Azfar, Abdullah
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Multiple Escrow Agents in VoIP2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Using a Key escrow agent in conjunction with Voice over IP (VoIP) communication ensures that law enforcements agencies (LEAs) can retrieve the session key used to encrypt data between two users in a VoIP session. However, the use of a single escrow agent has some drawbacks. A fraudulent request by an evil employee from the LEA can lead to improper disclosure of a session key. After the escrow agent reveals the key this evil person could fabricate data according to his/her needs and encrypt it again (using the correct session key). In this situation the persons involved in the communication session can be accused of crimes that he or she or they never committed. The problems with a single escrow agent becomes even more critical as a failure of the escrow agent can delay or even make it impossible to reveal the session key, thus the escrow agent might not be able to comply with a lawful court order or comply with their escrow agreement in the case of data being released according to this agreement (for example for disaster recovery).

    This thesis project focused on improving the accessibility and reliability of escrow agents, while providing good security. One such method is based on dividing the session key into M chunks and escrowing the chunks with M escrow agents. Using threshold cryptography the key can be regenerated by gathering any N-out-of-M chunks. The value of M and N may differ according to the role of the user. For a highly sophisticated session, the user might define a higher value for M and N for improved, availability, reliability, and security. For a less confidential or less important session (call), the value of M and N might be smaller. The thesis examines the increased availability and increased reliability made possible by using multiple escrow agents.

  • 196.
    Azzolin de Carvalho Pires, Gustavo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Multi-Cell Admission Control for WCDMA Networks2006Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It has long been recognized that in multi-cell WCDMA networks the admission of a new session into the system can have undesirable impact on the neighboring cells. Although admission control algorithms that take into account such multi-cell impact have been studied in the past, little attention has been paid to multi-cell admission and rate control algorithms when traffic is elastic. In this thesis, we propose a model for multi-cell multi-service WCDMA networks to study the impact of multi-cell admission and rate control algorithms on key performance measures such as the class-wise blocking and outage probabilities, block error rates, and the noise rise violation probabilities. By means of simulation we compare the performance of load based multi-cell algorithms with that of a single cell algorithm. We find that with multi-cell based algorithms the system capacity and performance (in terms of the above mentioned measures) are (in some cases significantly) better in homogeneous load scenarios as well as in the heterogeneous ’hotspot’ and ’hotaround’ scenarios.

  • 197.
    B. da Silva Jr., Jose Mairton
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control. Ericsson Research.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Spectral Efficient and Fair User Pairing for Full-Duplex Communication in Cellular Networks2016In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 15, no 11, p. 7578-7593Article in journal (Refereed)
    Abstract [en]

    —A promising new transmission mode in cellular networks is the three-node full-duplex mode, which involves a base station with full-duplex capability and two half-duplex user transmissions on the same frequency channel for uplink and downlink. The three-node full-duplex mode can increase spectral efficiency, especially in the low transmit power regime, without requiring full-duplex capability at user devices. However, when a large set of users is scheduled in this mode, self-interference at the base station and user-to-user interference can substantially hinder the potential gains of full-duplex communications. This paper investigates the problem of grouping users to pairs and assigning frequency channels to each pair in a spectral efficient and fair manner. Specifically, the joint problem of user uplink/downlink frequency channel pairing and power allocation is formulated as a mixed integer nonlinear problem that is solved by a novel joint fairness assignment maximization algorithm. Realistic system level simulations indicate that the spectral efficiency of the users having the lowest spectral efficiency is increased by the proposed algorithm, while a high ratio of connected users in different loads and self-interference levels is maintained.

  • 198. Babaheidarian, P.
    et al.
    Salimi, S.
    Papadimitratos, Panagiotis
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    Preserving confidentiality in the Gaussian broadcast channel using compute-and-forward2017In: 2017 51st Annual Conference on Information Sciences and Systems, CISS 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7926077Conference paper (Refereed)
    Abstract [en]

    We study the transmission of confidential messages across a wireless broadcast channel with K > 2 receivers and K helpers. The goal is to transmit all messages reliably to their intended receivers while keeping them confidential from the unintended receivers. We design a codebook based on nested lattice structure, cooperative jamming, lattice alignment, and i.i.d. coding. Moreover, we exploit the asymmetric compute-and-forward decoding strategy to handle finite SNR regimes. Unlike previous alignment schemes, our achievable rates are attainable at any finite SNR value. Also, we show that our scheme achieves the optimal sum secure degrees of freedom of 1 for the K-receiver Gaussian broadcast channel with K confidential messages and K helpers.

  • 199.
    Babu, Bibin
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Connected Me: Hardware for high speed BCC2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

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

  • 200.
    Backlund, Ola
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Policy-based IP services over UMTS2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Providing services over IP with real-time characteristics are one of the challenges that the next generation UMTS operators arefacing. Offering these services with adequate quality will be an important task in the management of their networks, which to alarge extent will be built on IP technology. Policy-based network management is an approach to improving network performanceand QoS. This is a network management model, suitable for highlevel service management that has been proposed as a promisingsolution for dynamic QoS. It is well suited for networks with hierarchical service models, which is the situation encountered inUMTS.

    The aim of this Master thesis is to examine IP services providedover UMTS based on the ideas from policy-based network technology and how they can be applied to this next generation ofcellular systems. A framework for policy-based QoS management support is outlined for the packet domain of UMTS, which is basedon the principles and experience derived from policy-based network technology found in fixed networks. A description of thefunctions and capabilities of a policy-based management system designed for UMTS is given, and the QoS related problems inUMTS are identified in order to evaluate the bottlenecks for improving service quality. The report ends with a proposal to howTelia may provide UMTS access to a IP access node that is currently being tested and developed in co-operation with othermanufacturers. Two possible solutions are described and evaluated from a QoS and architectural perspective.

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