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  • 401.
    Cambazoglu, Volkan
    et al.
    Uppsala universitet, Datorarkitektur och datorkommunikation.
    Gutkovas, Ramunas
    Uppsala universitet, Datalogi.
    Åman Pohjola, Johannes
    Uppsala universitet, Datalogi.
    Victor, Björn
    Uppsala universitet, Datalogi.
    Modelling and analysing a WSN secure aggregation protocol: A comparison of languages and tool support2015Report (Other academic)
    Abstract [en]

    A security protocol promises protection of a significant piece of information while using it for a specific purpose. Here, the protection of the information is vital and a formal verification of the protocol is an essential step towards guaranteeing this protection. In this work, we study a secure aggregation protocol (SHIA) for Wireless Sensor Networks and verify the protocol in three formal modelling tools (Pwb, mCRL2 and ProVerif). The results of formal verification heavily depend on the model specification and the ability of the tools to deal with the model. Among the three tools, there is difference in data representation, communication types and the level of abstraction in order to represent SHIA. ProVerif and mCRL2 are mature and well-established tools, geared respectively towards security and distributed systems; however, their expressiveness constrains modelling SHIA and its security properties. Pwb is an experimental tool developed by the authors; its relative immaturity is offset by its increased expressive power and customisability. This leads to different models of the same protocol, each contributing in different ways to our understanding of SHIA's security properties.

  • 402.
    Campolo, Claudia
    et al.
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Koucheryavy, Yevgeni
    Department of Communications Engineering, Tampere University of Technology, Tampere, Finland.
    Molinaro, Antonella
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Vinel, Alexey
    Department of Communications Engineering, Tampere University of Technology, Tampere, Finland.
    Characterizing broadcast packet losses in IEEE 802.11p/WAVE vehicular networks2011Conference paper (Refereed)
  • 403.
    Campolo, Claudia
    et al.
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Koucheryavy, Yevgeni
    Department of Communications Engineering, Tampere University of Technology, Tampere, Finland.
    Molinaro, Antonella
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Vinel, Alexey
    Department of Communications Engineering, Tampere University of Technology, Tampere, Finland.
    On the Performance of Beaconing in 802.11p/WAVE Vehicular Ad Hoc Networks2010Conference paper (Refereed)
    Abstract [en]

    Cooperative vehicular applications, like collision avoidance, driver assistance, and cruise control require that vehicles become aware of other vehicles in the surroundings. This cooperative awareness is achieved by beaconing, the exchange of periodical single-hop broadcast short status message that include data about the position, the speed, and the heading of a vehicle. Although several works have studied beaconing techniques both from an analytical point of view and through simulative study, none of the existing works has investigated how beaconing works on top of 802.11p/WAVE (Wireless Access for Vehicular Environment), the upcoming standard intended to deliver both safety and non-safety applications to vehicles on the roads. According to it, safety and control messages are expected to be delivered on a given frequency during a common control channel (CCH) interval set by the WAVE draft standard. The rest of the time, vehicles switch over one of available service channel (SCH) frequencies for non-safety related data exchange. In this paper we discuss and evaluate through numerical results the main effects the WAVE channel switching procedures have on beaconing. © 2010 by IEICE

  • 404.
    Campolo, Claudia
    et al.
    Mediterranea University of Reggio Calabria, Reggio Calabria, Italy.
    Molinaro, Antonella
    Mediterranea University of Reggio Calabria, Reggio Calabria, Italy.
    Berthet, Antoine O.
    Gif-sur-Yvette, CNRS-Centrale Supélec-Université Paris Sud, Gif-sur-Yvette, France.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Full-Duplex Radios for Vehicular Communications2017In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 55, no 6, 182-189 p.Article in journal (Refereed)
    Abstract [en]

    Recent significant advances in self-interference cancellation techniques pave the way for the deployment of full-duplex wireless transceivers capable of concurrent transmission and reception on the same channel. Despite the promise to theoretically double the spectrum efficiency, full-duplex prototyping in off-the-shelf chips of mobile devices is still in its infancy, mainly because of the challenges in mitigating self-interference to a tolerable level and the strict hardware constraints. In this article, we argue in favor of embedding full-duplex radios in onboard units of future vehicles. Unlike the majority of mobile devices, vehicular onboard units are good candidates to host complex FD transceivers because of their virtually unlimited power supply and processing capacity. Taking into account the effect of imperfect SI cancellation, we investigate the design implications of full-duplex devices at the higher-layer protocols of next-generation vehicular networks and highlight the benefits they could bring with respect to half-duplex devices in some representative use cases. Early results are also provided that give insight into the impact of self-interference cancellation on vehicle-to-roadside communications, and showcase the benefits of FD-enhanced medium access control protocols for vehicle-to-vehicle communications supporting crucial road safety applications.

  • 405.
    Campolo, Claudia
    et al.
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Molinaro, Antonella
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    To switch or not to switch: Service discovery and provisioning in multi-radio V2R communications2016In: Proceedings of 2016 8th International Workshop on Resilient Networks Design and Modeling (RNDM) / [ed] Magnus Jonsson, Jacek Rak, Arun Somani, Dimitri Papadimitriou & Alexey Vinel, Piscataway: IEEE Press, 2016, 281-287 p.Conference paper (Refereed)
    Abstract [en]

    Abstract:A rich portfolio of services (e.g., road traffic information, maps download, Internet/cloud access) will be delivered to users on wheels through Vehicular Ad Hoc Networks (VANETs).Most of them will be offered by road-side units (RSUs) sparsely deployed along the roads. The prompt access to such services by passing by vehicles highly relies on the efficiency of service announcement procedures performed by the RSUs. In this paper, we present an analytical framework that models the service discovery and access mechanisms in multi-channel vehicular networks. The model accounts for dual-radio devices under different channel configurations for the delivery of announcements (e.g., on the control channel, on a service channel) and related switching mechanisms. Guidelines are suggested for the setting of service announcements parameters and channel configuration to allow providers to boost service provisioning. ©2016 by IEEE 

  • 406.
    Campolo, Claudia
    et al.
    Mediterranea University of Reggio Calabria, Reggio Calabria, Italy.
    Molinaro, Antonella
    Mediterranea University of Reggio Calabria, Reggio Calabria, Italy.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Understanding Adjacent Channel Interference in Multi-Channel VANETs2014In: 2014 IEEE Vehicular Networking Conference (VNC) / [ed] Falko Dressler, Onur Altintas, Suman Banerjee, Björn Scheuermann & David Eckhoff, Piscataway, NJ: IEEE Press, 2014, 101-104 p., 7013316Conference paper (Refereed)
    Abstract [en]

    Multiple channels have been allocated in the 5 GHz spectrum for vehicular communications worldwide, however, due to the limited allocated bandwidth, simultaneous communications occurring over nearby channels may be affected by adjacent channel interference (ACI). Due to ACI, packet reception may be unsuccessful and transmissions may be delayed. In this work, we investigate the ACI phenomena in multichannel vehicular networks to shed light on their effects, with focus on the transmitter-side. To this purpose, a simple analytical model is introduced along with a preliminary evaluation. Suggestions are also provided about the usage of adjacent channels so to minimize side effects on the communication quality. © 2014 IEEE

  • 407.
    Campolo, Claudia
    et al.
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Molinaro, Antonella
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Vinel, Alexey
    Department of Communications Engineering, Tampere University of Technology, Tampere, Finland.
    Understanding the performance of short-lived control broadcast packets in 802.11p/WAVE Vehicular networks2011In: 2011 IEEE Vehicular Networking Conference (VNC) / [ed] Altintas, O., Chen, W., Heijenk, G. J., Dressler, F., Ekici, E., Kargl, F., Shigeno, H., Dietzel, S., Piscataway, NJ: IEEE Press, 2011, 102-108 p.Conference paper (Refereed)
  • 408.
    Campolo, Claudia
    et al.
    Università Mediterranea di Reggio Calabria, Reggio Calabria, Italy.
    Molinaro, Antonella
    Università Mediterranea di Reggio Calabria, Reggio Calabria, Italy.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Lyamin, Nikita
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Jonsson, Magnus
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Service Discovery and Access in Vehicle-to-Roadside Multi-Channel VANETs2015In: 2015 IEEE International Conference on Communication Workshop, Piscataway, NJ: IEEE Press, 2015, 2477-2482 p.Conference paper (Refereed)
    Abstract [en]

    A wide portfolio of safety and non-safety services will be provided to drivers and passengers on top of Vehicular Ad Hoc Networks (VANETs).

    Non-safety services are announced by providers, e.g., road-side units (RSUs), on a channel that is different from the one where the services are delivered. The dependable and timely delivery of the advertisement messages is crucial for vehicles to promptly discover and access the announced services in challenging vehicle-to-roadside scenarios, characterized by intermittent and short lived connectivity.

    In this paper, we present an analytical framework that models the service advertisement and access mechanisms in multichannel vehicular networks.

    The model accounts for dual-radio devices, and computes the mean service discovery time and the service channel utilization by considering the disruption periods due to the switching of the RSU from the advertising channel (where announcements are transmitted) to the advertised channel (where services are exchanged), under different channel and mobility conditions. It provides quick insights on parameter settings to allow providers to improve service provisioning. © 2015 IEEE

  • 409.
    Campolo, Claudia
    et al.
    University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Molinaro, Antonella
    University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Vinel, Alexey
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Zhang, Yan
    Simula Research Laboratory, Fornebu, Norway.
    Modeling and enhancing infotainment service access in vehicular networks with dual-radio devices2016In: Vehicular Communications, ISSN 2214-2096, Vol. 6, 7-16 p.Article in journal (Refereed)
    Abstract [en]

    A dedicated spectrum portion at 5 GHz is available to provide services in vehicular environments (e.g., road safety, traffic efficiency, comfort and infotainment services). The multitude of non-safety critical services offered by roadside and mobile providers can be accessed by vehicles under radio coverage if they listen to the advertisement messages announcing the service configuration parameters and tune to the announced frequency to access the service. Due to intermittent and short connectivity periods, timely and successful advertisements reception is crucial to enable a vehicle accessing available services while it is still connected to the provider.

    In this paper, we design an analytical model of the service advertisement and access procedure for dual-radio vehicular devices. Moreover, we enhance the advertisement phase with a simple technique of message repetition and channel switching coordination, which helps in making vehicles aware of local services promptly coping with channel impairments and collisions. The model flexibly accounts for channel switching, message repetitions, access prioritization, and interference by contending traffic on the channel where service announcements are regularly transmitted. ©2016 Elsevier Inc. All rights reserved.

  • 410.
    Campolo, Claudia
    et al.
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Molinaro, Antonella
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Reggio Calabria, Italy.
    Vinel, Alexey
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES).
    Zhang, Yan
    Simula Research Laboratory, Fornebu, Norway.
    Modeling Event-Driven Safety Messages Delivery in IEEE 802.11p/WAVE Vehicular Networks2013In: IEEE Communications Letters, ISSN 1089-7798, Vol. 17, no 12, 2392-2395 p.Article in journal (Refereed)
    Abstract [en]

    A stochastic model is designed to assess the delivery performance of event-driven safety messages in IEEE 802.11p/1609.4 vehicular ad-hoc networks (VANETs). The study focuses on the case of a vehicle detecting an unpredictable hazard and broadcasting the alert in the one-hop neighborhood. The model aims at providing quick insights into the impact of the latest WAVE specifications (i.e., traffic differentiation, channel switching) on the delivery of such short-lived alert messages. Results prove that it is accurate in capturing the effect of relevant parameters and show that repeating the alert transmission on the control channel helps to achieve reliable delivery. © 2013 IEEE.

  • 411.
    Campolo, Claudia
    et al.
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria.
    Molinaro, Antonella
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria.
    Vinel, Alexey
    Department of Communications Engineering, Tampere University of Technology.
    Zhang, Yan
    Simula Research Laboratory.
    Modeling Prioritized Broadcasting in Multichannel Vehicular Networks2012In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 61, no 2, 687-701 p.Article in journal (Refereed)
    Abstract [en]

    Effective data broadcasting is essential in vehicular networks not only for road-safety message dissemination but also to aid routing and cooperative driving applications through periodic beaconing and to spread network initialization advertisements that are mandatory to support infotainment applications. Broadcast data are neither acknowledged nor retransmitted in case of failure, which raises the possibility of frame loss due to channel errors and collisions with multiple simultaneous broadcasts. This paper aims at modeling periodic broadcasting on the control channel of IEEE Std. 802.11p vehicular networks with multichannel architecture. Unlike previous related work, the proposed novel analytical approach accounts for mutual influence among nodes, frequent periodic updates of broadcasted data, standard network advertisement procedures, and 802.11p prioritized channel access with multichannel-related phenomena under various link quality conditions. © 2012 IEEE.

  • 412.
    Campolo, Claudia
    et al.
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Italy.
    Vinel, Alexey
    Department of Communications Engineering, Tampere University of Technology.
    Molinaro, Antonella
    Dipartimento di Informatica, Matematica, Elettronica e Trasporti, University Mediterranea of Reggio Calabria, Italy.
    Koucheryavy, Yevgeni
    Department of Communications Engineering, Tampere University of Technology.
    Modeling Broadcasting in IEEE 802.11p/WAVE Vehicular Networks2011In: IEEE Communications Letters, ISSN 1089-7798, Vol. 15, no 2, 199-201 p.Article in journal (Refereed)
    Abstract [en]

    IEEE 802.11p/WAVE (Wireless Access in Vehicular Environments) is an emerging family of standards intended to support wireless access in Vehicular Ad Hoc Networks (VANETs). Broadcasting of data and control packets is expected to be crucial in this environment. Both safety-related and non-safety applications rely on broadcasting for the exchange of data or status and advertisement messages. Most of the broadcasting traffic is designed to be delivered on a given frequency during the control channel (CCH) interval set by the WAVE draft standard. The rest of the time, vehicles switch over to one of available service channels (SCHs) for non-safety related data exchange. Although broadcasting in VANETs has been analytically studied, related works neither consider the WAVE channel switching nor its effects on the VANET performance. In this letter, a new analytical model is designed for evaluating the broadcasting performance on CCH in IEEE 802.11p/WAVE vehicular networks. This model explicitly accounts for the WAVE channel switching and computes packet delivery probability as a function of contention window size and number of vehicles. © 2011 IEEE.

  • 413.
    Campos, Jaime
    Linnaeus University, Faculty of Technology, Department of Informatics. LNU.
    Modelling the Web 2.0 oriented sites for the e-maintenance applications2013In: International congress of condition monitoring and diagnostic engineering management: Congress Proceedings, COMADEM 2013, 11-13 June, Helsiki, 2013, 52-57 p.Conference paper (Refereed)
  • 414.
    Campos, Jaime
    Linnaeus University, Faculty of Technology, Department of Informatics.
    The ICT Systems Developments in Maintenance: From Data Processing into Knowledge Driven Approaches2014In: Proceedings of the 15th European conference on Knowledge management, (ECKM 2014): vol. 1-3 / [ed] Vivas C & Sequeira P, Academic Conferences Limited, 2014, 182-188 p.Conference paper (Refereed)
    Abstract [en]

    The paper goes through the developments of Information and Communication Technologies (ICTs) in the area of Condition Monitoring (CM) and Maintenance with the aim to understand the current state of the ICTs developments in the area of interest as well as their future prospects. The findings are ordered into a framework, which emphasizes the diverse maturity aspects when it comes to the use of these technologies. The results show that the researchers are working with various ICT applications that are in the different eras of the framework. There are findings that support the last era, i.e. the fourth era, but those findings are fewer. However, the applications that support this last era, even if they are at the primary stage, is the e-maintenance approach especially when the knowledge driven approaches are considered in their applications. The e-maintenance approach apart from its integration capabilities also considers other important aspects such as collaboration, cooperation, and organisational learning as well as companies' strategies such as the condition based maintenance, etc. it is, therefore, important to consider the e-maintenance approach as a facilitator for the entrance into the fourth era, which promises sustainability in the use of the ICTs for the domain of interests as well as higher organizational performance

  • 415.
    Campos, Jaime
    et al.
    Linnaeus University, Faculty of Technology, Department of Informatics.
    Jantunen, Erkki
    VTT Technical Research Centre of Finland, Finland.
    Baglee, David
    University of Sunderland, UK.
    Fumagalli, Luca
    Politecnico di Milano, Italy .
    Emmanouilidis, Christos
    Cranfield University, UK.
    Gilabert, Eduardo
    Fundación TEKNIKER, Spain.
    Mobile Information Systems in Maintenance Engineering and Asset Management2016In: Journal of Societal Studies, ISSN 2029-2244, Vol. 8, no 2, 180-197 p.Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to provide a profound insight into important characteristics with regard to the integration of mobile technology into the area of industrial maintenance. The aspects highlighted in the paper uncover, for instance, acceptance models and best practices, as well as the financial impact of mobile technologies in the domain of interest. Moreover, the paper pinpoints some important characteristics that impede full integration of these technologies into this area. In addition, the economic benefits and the current situation with regard to mobile integration are highlighted. In addition, relevant literature and theories are analysed and discussed. Furthermore, the industrial integration of mobile technologies is outlined. The results indicate that there is a tendency to place an emphasis on the technical aspects of mobile devices rather than on understanding the organisational context, which affects the integration of mobile technologies into this domain.

    The work provides a thorough understanding of best practices and aspects to consider for the successful integration of mobile technologies in this area. This is because the use of mobile devices enables maintenance staff to gain access to information and services pertaining to the task in hand in real time, as long as some form of network access is provided. Users of these devices thus become mobile actors who dynamically interact with the physical environment in the workplace and support information systems, leading to a faster response to events and improved organizational performance.

  • 416.
    Campos, Jaime
    et al.
    Linnaeus University, Faculty of Technology, Department of Informatics.
    Jantunen, Erkki
    VTT Technical Research Centre of Finland, Finland.
    Baglee, David
    University of Sunderland, UK .
    Gilabert, Eduardo
    Fundación TEKNIKER, Spain.
    Fumagalli, Luca
    Politecnico di Milano, Italy.
    Emmanouilidis, Christos
    ATHENA Research & Innovation Centre, Greece .
    The Use of Mobile Technologies and Their Economic Benefits in Maintenance2016In: Proceedings of the 10th World Congress on Engineering Asset Management (WCEAM 2015) / [ed] Koskinen, K.T., Kortelainen, H., Aaltonen, J., Uusitalo, T., Komonen, K., Mathew, J., Laitinen, J. (Eds.), Springer, 2016, 113-119 p.Conference paper (Refereed)
    Abstract [en]

    The use of mobile devices enables maintenance staff to gain access to information and services relevant to the task in hand in near real time and wherever some form of network access is provided. Essentially, mobile device users become mobile actors who dynamically interact with the physical environment, i.e. workplace, and supporting information systems, leading to faster response to events and an increased performance. This paper provides insight into the acceptance prospects and best practices of the mobile technologies in the area of maintenance. Furthermore, the potential financial impact is discussed as a key driver for the adoption of mobile technologies in the maintenance practice.

  • 417.
    Campos, Jaime
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics. LNU.
    Kortelainen, Juha
    VTT Technical Research Centre of Finland.
    Jantunen, Erkki
    VTT Technical Research Centre of Finland.
    Product Lifecycle Simulation Applying Semantic Data Management2011In: Product Lifecycle Management: Virtual Product Lifecycles for Green Products and Services:Proceedings of the PLM11 conference held at the Eindhoven University of Technology, The Netherlands, 11-13 July 2011 / [ed] Pels, H.J., Bouras, A., & McMahon, C., 2011, 455-464 p.Conference paper (Refereed)
    Abstract [en]

    Product lifecycle simulation (PLCS) has been given ever moreattention as the manufacturers are competing with the quality and lifecyclecosts of their products. Especially, the need of companies to try to get a strongposition in providing services for their products and thus to make themselvesless vulnerable to changes in the market has led to high interest in PLCS. Ashort summary of current status of PLCS is presented especially related to thepoor integration of data in product lifecycle management systems and in PLCS.The potential of applying semantic data management to solve these problems isthoroughly discussed in the light of recent development. A basic roadmap howthe above-described problems could be tackled with open software solutions ispresented. Finally, this paper reviews the emergent Web technologies such asthe Semantic Web framework and the Web services.

  • 418.
    Campos, Jaime
    et al.
    LNU.
    Sharma, Pankaj
    Indian Institute of Technology Delhi.
    Jantunen, Erkki
    VTT Technical Research Centre of Finland.
    Baglee, David
    Department of Computing, Engineering and Technology, University of Sunderland, UK.
    Fumagalli, Luca
    Politecnico di Milano, Italy.
    Business Performance Measurements in Asset Management with the Support of Big Data Technologies2017In: Management Systems in Production Engineering, Vol. 25, no 3, 143-149 p.Article in journal (Refereed)
  • 419.
    Cao, Le Phuong
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Oechtering, Tobias J.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Optimal transmit strategy for MIMO channels with joint sum and per-antenna power constraints2017In: 2017 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    This paper studies optimal transmit strategies for multiple-input multiple-output (MIMO) Gaussian channels with joint sum and per-antenna power constraints. It is shown that if an unconstraint optimal allocation for an antenna exceeds a per-antenna power constraint, then the maximal power for this antenna is used in the constraint optimal transmit strategy. This observation is then used in an iterative algorithm to compute the optimal transmit strategy in closed-form. Finally, a numerical example is provided to illustrate the theoretical results.

  • 420.
    Cao, Wei Qiu
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A new Content Distribution Network architecture - PlentyCast2004Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Content Distribution Networks have existed for some years. They involve the following problem domains and have attracted attention both in academic research and industry: content replica placement, content location and routing, swarm intelligence, and overlay network self-organization for this type of distributed system. In this project, we propose a novel Content Distribution Network architecture – PlentyCast. This study focuses on improving access latency, network scalability, high content availability, low bandwidth consumption, and improving infrastructure performance for Content Distribution Networks. Outstanding problems such as: Flash crowd, DoS, and difficulty of traffic engineering due to Peer-to-Peer are addressed.

  • 421.
    Carlos, Perez Penichet
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Hermans, Frederik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Augmenting IoT networks with backscatter-enabled passive sensor tags2016In: Proceedings of the 3rd Workshop on Hot Topics in Wireless, 2016, 23-27 p.Conference paper (Refereed)
    Abstract [en]

    The sensing modalities available in an Internet-of-Things (IoT) network are usually fixed before deployment, when the operator selects a suitable IoT platform. Retrofitting a deployment with additional sensors can be cumbersome, because it requires either modifying the deployed hardware or adding new devices that then have to be maintained. In this paper, we present our vision and work towards passive sensor tags: battery-free devices that allow to augment existing IoT deployments with additional sensing capabilities without the need to modify the existing deployment. Our passive sensor tags use backscatter transmissions to communicate with the deployed network. Crucially, they do this in a way that is compatible with the deployed network's radio protocol, and without the need for additional infrastructure. We present an FPGA-based prototype of a passive sensor tag that can communicate with unmodified 802.15.4 IoT devices. Our initial experiments with the prototype support the feasibility of our approach. We also lay out the next steps towards fully realizing the vision of passive sensor tags.

  • 422.
    Carls, Johan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    NGN – Nästa Generations Nätverk (Nätverks- och Riskanalys) för Piteå Kommun2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    My mission has been to technical documentation and identify Piteå Municipality's existing network infrastructure. Everything has been summarized in several different areas: Network Services, Network-related services, Technology, Management/Control and Security. A risk analysis has been developed where I have identified a total of 28 risks and deficiencies in the municipality's existing network infrastructure. 4 risks and deficiencies under Design, 9 risks and deficiencies under Security, 5 risks and deficiencies under Network related services, 2 risks and deficiencies under Network Services, 2 risks and deficiencies under Management/Control and 5 risks and deficiencies under Technology. All risks and deficiencies have been categorized in order of low, medium and high risks and deficiencies of varying action time (0-24 + months). This final report has been the basis for then developing a new future-proof network infrastructure using a Requirements and Vision for the Municipality of Piteå.

  • 423.
    Carlsson, Daniel
    KTH, School of Information and Communication Technology (ICT).
    Dynamics AX in the Cloud: Possibilities and Shortcomings2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The usage of the cloud is rapidly increasing and is something that is of large interest to everyone involved in technology. The purpose of this thesis is to examine the benefits and possible shortcomings of using Microsoft Dynamics AX in the cloud, specifically Microsoft Azure, instead of using local datacenters. This thesis project has been done at Scania IT using their implementation of Dynamics AX.

    This thesis project consists of an extensive literature study regarding both ERP Systems as well as other systems in regards to the cloud. It was decided early on to focus on the new version of Dynamics AX, which currently is only available in the cloud and compare this implementation to the two versions that the majority are using today, AX 2009 and AX 2012. The benefits of AX and Azure both being Microsoft products are clear with the welldesigned integrations and support all the way through the clients to the servers regarding backups and load balancing. It is shown how the developers have to work differently in regards to integrations with outside systems, especially in regards to AX 2009 with the frameworks having changed. The addition of Data Entities mean that the developers can save a lot of time by only needing a reference to the location of the object in the database instead of having to keep track of all the tables themselves.

    The analysis focuses on the differences in four different areas, performance & accessibility, scalability, cost savings as well as security & privacy. The background knowledge that is being used for the analysis primarily comes from the literature study as well as knowledge gained by studying the implementation at Scania today. The result shows that there are clear advantages regarding performance, cost savings and especially accessibility, however it is also clear that laws in a lot of countries still have not caught up with the fact that it is possible to use the cloud for data storage these days. Which in turn means that the best move in the near future for the majority of ERP users would be either a hybrid or private cloud within the borders of the same country.

  • 424.
    Carlsson, Henric
    University of Skövde, School of Informatics.
    Using A Recommender To Influence Consumer Usage2013Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    In this dissertation, the issues of the increased awareness of energy use are considered. Energy technologies are continuously improved by energy retailers and academic researchers. The Smart Grid are soon customary as part of the energy domain. But in order to improve energy efficiency the change must come from the consumers. Consumers should be active decision makers in the Smart Grid domain and therefor a Recommender system suits the Smart Grid and enables customers. Customers will not use energy in the way energy retailers, and politicians advocates instead they will do what fits them. By investigating how a Recommender can be built in the Smart Grid we focus on parameters and information that supports the costumers and enables positive change. An investigation of what customers perceive as relevant is pursued as well as how relevancy can adjust the system. A conceptual model of how to build a Recommender is rendered through a literature review, a group interview and a questionnaire.

  • 425.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Optimized eeeBond: Energy Efficiency with non-Proportional Router Network Interfaces2016In: PROCEEDINGS OF THE 2016 ACM/SPEC INTERNATIONAL CONFERENCE ON PERFORMANCE ENGINEERING (ICPE'16), ACM Digital Library, 2016, 215-223 p.Conference paper (Refereed)
    Abstract [en]

    The recent Energy Efficient Ethernet (EEE) standard and the eBond protocol provide two orthogonal approaches that allow significant energy savings on routers. In this paper we present the modeling and performance evaluation of these two protocols and a hybrid protocol. We first present eeeBond, pronounced ``triple-e bond'', which combines the eBond capability to switch between multiple redundant interfaces with EEE's active/idle toggling capability implemented in each interface. Second, we present an analytic model of the protocol performance, and derive closed-form expressions for the optimized parameter settings of both eBond and eeeBond. Third, we present a performance evaluation that characterizes the relative performance gains possible with the optimized protocols, as well as a trace-based evaluation that validates the insights from the analytic model. Our results show that there are significant advantages to combine eBond and EEE. The eBond capability provides good savings when interfaces only offer small energy savings when in short-term sleep states, and the EEE capability is important as short-term sleep savings improve.

  • 426.
    Carlsson, Robin
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Investigation and Implementation of Coexistence Tool for Antennas2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the increase of the number of radios and antennas on today’s systems, the risk of co-site interference is very high. Intermodulation product and antenna coupling are two common sources of interference. The thesis investigates some features of a radio system, like antenna types, receiver parameters, intermodulation products and isolation, and suggests how this knowledge can be used to minimize the risk of co-site interference. The goal is to maximize the isolation between the antennas, by good frequency planning, the use of filters and taking great care in antenna placement. A first version of an analysis software was developed where transmitters and receivers can be paired and evaluated. An intermodulation product calculator was also implemented, to easily find which products are an issue and where they originate. The goal of the software is to be simple to use and easy to adapt to different setups and situations. It should also be easy to upgrade with new features.

  • 427.
    Carlsson, Stefan
    et al.
    KTH, Superseded Departments, Teleinformatics.
    Halén, Erik
    KTH, Superseded Departments, Teleinformatics.
    Mobile Internet: Content Adaptation for Limited Devices2000Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis investigates how to adapt content on the Web to the limited I/O capabilities of today’s WAP (Wireless Application Protocol) devices and how to translate from HTML to WML (Wireless Markup Language). We also give an overview of WAP and Mobile Internet and a brief analysis of the future of WAP.

    To evaluate different methods of adaptation, two existing Web sites are adapted to WML. Three different methods are tried and evaluated: The first method is a brute force WML re-coding of the site. The second method is an XML based solution that separates the data from the presentation and uses different XSLT (eXtensible Style sheet Language Transformations) style sheets for different devices. The third method uses a proxy that translates a requested page from HTML to WML. The proxy evaluated here is Oracle’s Portal-to-Go in its semi-automated form, i.e. where it is manually pre-configured for every site it adapts.

    An important issue is whether to adapt specifically for each device or whether to use generically written WML for the entire range of WAP devices. Another issue is that a WAP device only can receive a limited amount of information at a time, and this limit varies between different devices.

  • 428.
    Carlsson, Ulrika
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Stenhammar, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Sociala medier: och kundinteraktion i mindre företag 2011Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Title: Social Media – And customer interaction in smaller firms

    Seminar date: 2011-06-10

    Course: Information Logistics, D-level.

    Authors: Marie Stenhammar and Ulrika Carlsson

    Advisor: Jaime Campos

    Key words: Social Media, Web 2.0, Co-creation, Viral marketing, Word of Mouth, smaller firms

    Purpose: This paper aims to describe the relevance of social media to smaller firms, the challenges and opportunities they face and what strategies they use, in the interaction with their customers.

    Methodology: The study is qualitative in nature and has an abductive approach. The empirical material consists of in-depth interviews with chosen companies and Internet observations.

    Theoretical perspectives: Social Media, Web 2.0, Co-creation, Viral marketing, Word of Mouth

    Empirical foundation: The study takes its empirical base from in-depth interviews with representatives from the small companies and internet observations connected to these.

    Conclusions: Smaller companies have great interest in social media. They preferably use Facebook, blogs, YouTube and Twitter. Their strategy is mainly to be very active and update their social media regularly. The opinion of the companies is that social media offer several possibilities such as stronger relationships with customers and the ability to collect information about the market.

  • 429.
    Carrara, Elisabetta
    KTH, Superseded Departments, Teleinformatics.
    Wireless Adaptation of a Security Management Protocol Suite1999Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Internet Security is rapidly increasing in importance, as Internet itself is spreading out so fast. The IETF Security working group has defined the "IP Security Protocol Suite", a set of protocols that aim at securing the IP layer, so providing general security services for all kinds of applications.

    The IPSec Protocol Suite is completed by a protocol for key management and key exchange, the "Internet Security Association and Key Management Protocol (ISAKMP)" . It is currently an IETF Proposed Standard for the Internet.

    In this thesis we describe ISAKMP, and also its use together with the Internet Key Exchange (IKE) protocol, as a negotiation and key exchange protocol for IPSec. A general overview of cryptography is also provided, since ISAKMP widely uses modern cryptographic techniques.

    ISAKMP flexibility is at the cost of complexity and increased packet traffic. This should be faced in constrained communications, such as wireless. Therefore, this thesis introduces some proposals for a compressed version of the protocol, trying to reduce the number of handshakes and the number of transmitted bytes without significantly decreasing the security level.

    The model is based on the use of a Proxy, which follows the compressed version of ISAKMP on the side of the  mobile node, and then switches to the original version of the protocol on the wired side with the second peer. Ad-hoc solutions are adopted, and security implications are taken into account.

  • 430. Casati, Fabio
    et al.
    Daniel, Florian
    Dantchev, Guenadi
    Eriksson, Joakim
    Finne, Niclas
    Karnouskos, Stamatis
    Montera, Patricio Moreno
    Mottola, Luca
    Oppermann, Felix Jonathan
    Picco, Gian Pietro
    Quartulli, Antonio
    Römer, Kay
    Spiess, Patrik
    Tranquillini, Stefano
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Towards business processes orchestrating the physical enterprise with wireless sensor networks2012In: ICSE, 2012, 1357-1360 p.Conference paper (Refereed)
  • 431.
    Casselgren, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Bodin, Ulf
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Reusable road condition information system for traffic safety and targeted maintenance2017In: IET Intelligent Transport Systems, ISSN 1751-956X, E-ISSN 1751-9578, Vol. 11, no 4, 230-238 p.Article in journal (Refereed)
    Abstract [en]

    Driver awareness of current winter road conditions (RCs) is known to affect the frequency of accidents due to sudden changes in these conditions. For example, partially icy roads that appear during autumn in northern areas typically result in collisions and ditch runs unless the drivers are generally aware of the situation. Availing motorists who drive under winter RCs of enhanced information is therefore highly desirable to increase their awareness of hazardous driving conditions. Such conditions need to be predicted ahead of time and presented to drivers before they attempt slippery road sections. Moreover, the identification of slippery RCs should quickly trigger targeted road maintenance to reduce the risk of accidents. This study presents a scalable and reusable collaborative intelligent transport system, herein referred to as an RC information system (RCIS). RCIS provides accurate RC predictions and forecasts based on RC measurements, road weather observations, and short-term weather forecasts. The prediction methods in the context of the distributed RCIS have been tested using a prototype implementation. These tests confirmed that these inputs could be combined into useful and accurate information about winter RCs that can be adapted for different types of users.

  • 432.
    Cavdar, Cicek
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Ruiz, M.
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Velasco, L.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Design of green optical networks with signal quality guarantee2012In: IEEE International Conference on Communications, IEEE , 2012, 3025-3030 p.Conference paper (Refereed)
    Abstract [en]

    Energy consumption of communication networks is growing very fast due to the rapidly increasing traffic demand. Consequently, design of green communication networks gained a lot of attention. In this paper we focus on optical Wavelength Division Multiplexing (WDM) networks, able to support this growing traffic demand. Several energy-aware routing and wavelength assignment (EA-RWA) techniques have been proposed for WDM networks in order to minimize their operational cost. These techniques aim at minimizing the number of active links by packing the traffic as much as possible, thus avoiding the use of lightly loaded links. As a result, EA-RWA techniques may lead to longer routes and to a high utilization on some specific links. This has a detrimental effect on the signal quality of the optical connections, i.e., lightpaths. In this study we quantify the impact of power consumption minimization on the optical signal quality. and address this problem by proposing a combined impairment and energy-aware RWA (IEA-RWA) approach. Towards this goal we developed a complete mathematical model that incorporates both linear and non-linear physical impairments together with an energy efficiency objective. The IEA-RWA problem is formulized as a Mixed Integer Linear Programming (MILP) model where both energy efficiency and signal quality considerations are jointly optimized. By comparing the proposed IEA-RWA approach with existing RWA (IA-RWA and EA-RWA) schemes, we demonstrate that our solution allows for a reduction of energy consumption close to the one obtained by EA-RWA approaches, while still guaranteeing a sufficient level of the optical signal quality.

  • 433. Cea, Mauricio G.
    et al.
    Goodwin, Graham C.
    Wigren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Model predictive zooming power control in future cellular systems under coarse quantization2012In: Proc. 76th Vehicular Technology Conference, Piscataway, NJ: IEEE, 2012Conference paper (Refereed)
  • 434. Cen, M.
    et al.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Mégret, P.
    Moeyaert, V.
    Wuilpart, M.
    Fast and simple fault monitoring for long-reach passive optical networks2014In: 2014 European Conference on Optical Communication, (ECOC), IEEE , 2014, 6964070- p.Conference paper (Refereed)
    Abstract [en]

    We propose a fast and simple monitoring system based on multi-wavelength bi-directional transmission reflection analysis approach for long-reach passive optical networks. Both experimental and simulation results have demonstrated the proposed system can reach high accuracy for fault localization.

  • 435.
    Chabouni (nee Talbi), Sami
    KTH, Superseded Departments, Teleinformatics. KTH, School of Information and Communication Technology (ICT).
    Investigation and Prototyping of a web based manager in a GSM SIM Application Platform1998Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The growing need for communication in the world has increased the use of telephony and has therefore led to several technical innovations and improvements in the field of telecommunications. As countries develop their infrastructure new ways of communicating arise. But the technical innovations do not completely guide the evolution of the infrastructure. Many times, the way people act, i.e., their mentality and traditions, decides how to invest in the infrastructure. As basic infrastructure is being built in some developing countries, others come up with new revolutionary solutions to replace old infrastructure and, for some developing countries the question arises whether to continue to invest several hundreds of millions of dollars in traditional telephony wiring. The cellular technique is revolutionary enough to be applied in countries that haven’t yet built a telephony network covering an adequate area of the country. In these countries, investments might therefore be focused on the cellular technique, rather than continuing to invest in cable networking. Thus adapting cellular technology to a worldwide distribution is necessary when it comes to administration and subscriber payment. The communication providers meet administrative obstacles when it comes to telephony services for a large-scale distribution. Will the subscribers pay for the services we offer them?

    Using Subscriber Identity Modules (SIM) one way to solve this problem is to define a prepaid scheme. It is based on the fact that the subscriber uses a unique identifier to make a connection and is billed using this identifier. The service provider is free to choose if the subscriber is thrustworthy or not and thus must pay in advance for the services or billed retroactively. This general way of solving administration problems does not apply only to developing countries where retroactive billing isn’t a common tradition. It is equally applicable to industrial countries where some people are banned from credibility for a couple of years because they haven’t paid their bills in time, or just because they don’t have employment at the time of their subscription application.

    To be in possession of a telephone is everyone’s right in most of the industrialized countries.

  • 436.
    Chairetakis, Eleftherios
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Alkudhir, Bassam
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Mystridis, Panagiotis
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Deployment of Low Interaction Honeypots in University Campus Network2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Large scale networks face daily thousands of network attacks. No matter the strength of the existing security defending mechanisms, these networks remain vulnerable, as new tools and techniques are being constantly developed by hackers. A new promising technology that lures the attackers in order to monitor their malicious activities and divulge their intentions is emerging with Virtual Honeypots. In the present thesis, we examine an extensive security mechanism based on three different open source low interaction honeypots. We implement this mechanism at our university campus network in an attempt to identify the potential threats and methods used against our network. The data gathered by our honeypots reveal valuable information regarding the types of attacks, the vulnerable network services within the network and the malicious activities launched by attackers.

  • 437.
    Chandhar, Prabhu
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Danev, Danyo
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Massive MIMO as Enabler for Communications with Drone Swarms2016In: 2016 INTERNATIONAL CONFERENCE ON UNMANNED AIRCRAFT SYSTEMS (ICUAS), IEEE , 2016, 347-354 p.Conference paper (Refereed)
    Abstract [en]

    Massive multiple-input multiple-output (MIMO) is an emerging technology for mobile communications, where a large number of antennas are employed at the base station to simultaneously serve multiple single-antenna terminals with very high capacity. In this paper, we study the potentials and challenges of utilizing massive MIMO for unmanned aerial vehicles (UAVs) communication. We consider a scenario where multiple single-antenna UAVs simultaneously communicate with a ground station (GS) equipped with a large number of antennas. Speci[1]cally, we discuss the achievable uplink (UAV to GS) capacity performance in the case of line-of-sight (LoS) conditions. We also study the type of antenna polarization that should be used in order to maintain a reliable communication link between the GS and the UAVs. The results obtained using a realistic geometric model show that massive MIMO is a potential enabler for high-capacity UAV network

  • 438.
    Chandhar, Prabhu
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Danev, Danyo
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    On Ergodic Rates and Optimal Array Geometry in Line-of-Sight Massive MIMO2016Conference paper (Refereed)
    Abstract [en]

    We investigate the achievable ergodic rate of Massive multi-input-multi-output (MIMO) system in environments with high mobility and line-of-sight (LoS). A 3-dimensional geometric model with uniform rectangular array at the basestation (BS) is used for the investigation. We derive a closed formexpression for a lower bound on the uplink ergodic rate takinginto account imperfections of the channel state information,number of BS antennas, antenna spacing, and spatial distributionof user terminals. The results show that, in LoS Massive MIMO, when the terminals are spherically uniformly distributed around the BS, the ergodic rate is maximized for antenna spacing equal to integer multiples of one-half wavelength.

  • 439. Chandu, Chiranjeevi
    Region of Interest Aware and Impairment Based Image Quality Assessment2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 440.
    Chang, Peiliang
    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).
    Area Spectral and Energy Efficiency Analysis of Cellular Networks with Cell DTX2015In: IEEE Globecom 2015 , San Diego, December 6th-10th, 2015, IEEE conference proceedings, 2015, 1-6 p.Conference paper (Refereed)
    Abstract [en]

    Cell discontinuous transmission (DTX) has been proposed as an effective solution to reduce energy consumption of cellular networks. In this paper, we investigate the impact of network traffic load on area spectral efficiency (ASE) and energy efficiency (EE) of cellular networks with cell DTX. Closedform expressions of ASE and EE as functions of traffic load for cellular networks with cell DTX are derived. It is shown that ASE increases monotonically in traffic load, while EE depends on the power consumption of base stations in sleep mode. If this power consumption is larger than a percentage of the active-mode power consumption, EE increases monotonically with traffic load and is maximized when the network is fully loaded. Otherwise, EE first increases and then decreases in traffic load. In this case, ASE and EE are maximized with different loads. The percentage threshold only depends on the path loss exponent of radio propagation environment and is calculated to be 56.2% when the path loss exponent is 4.

  • 441.
    Chang, Peiliang
    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).
    Energy and Spectral Efficiency of Cellular Networks with Discontinuous Transmission2017In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, no 5, 2991-3002 p.Article in journal (Refereed)
    Abstract [en]

    Cell discontinuous transmission (DTX) has been proposed as a solution to reduce energy consumption of cellular networks. This paper investigates the impact of network traffic load on spectral and energy efficiency of cellular networks with DTX. The SINR distribution as a function of traffic load is derived firstly. Then sufficient condition for ignoring thermal noise and simplifying the SINR distribution is investigated. Based on the simplified SINR distribution, the network spectral and energy efficiency as functions of network traffic load are derived. It is shown that the network spectral efficiency increases monotonically in traffic load, while the optimal network energy efficiency depends on the ratio of the sleep-mode power consumption to the active-mode power consumption of base stations. If the ratio is larger than a certain threshold, the network energy efficiency increases monotonically with network traffic load and is maximized when the network is fully loaded. Otherwise, the network energy efficiency firstly increases and then decreases in network traffic load. The optimal load can be identified with a binary search algorithm. The power ratio threshold depends solely on the path loss exponent α, e.g. 56% for α = 4. All these analytic results are further validated by the numerical simulations.

  • 442. Chaporkar, P.
    et al.
    Proutière, Alexandre
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Optimal distributed scheduling in wireless networks under SINR interference model2013In: 2013 51st Annual Allerton Conference on Communication, Control, and Computing, Allerton 2013, IEEE conference proceedings, 2013, 1372-1379 p.Conference paper (Refereed)
    Abstract [en]

    Radio resource sharing mechanisms are key to ensuring good performance in wireless networks. In their seminal paper [1], Tassiulas and Ephremides introduced the Maximum Weighted Scheduling algorithm, and proved its throughput-optimality. Since then, there have been extensive research efforts to devise distributed implementations of this algorithm. Recently, distributed adaptive CSMA scheduling schemes [2] have been proposed and shown to be optimal, without the need of message passing among transmitters. However their analysis relies on the assumption that interference can be accurately modelled by a simple interference graph. In this paper, we consider the more realistic and challenging SINR interference model. We present the first distributed scheduling algorithms that (i) are optimal under the SINR interference model, and (ii) that do not require any message passing. They are based on a combination of a simple and efficient power allocation strategy referred to as Power Packing and randomization techniques. These algorithms are rate-optimal in the sense that they perform as well as the best centralized scheduling schemes in scenarios where each transmitter is aware of the rate at which it should send packets to the corresponding receiver. As shown in [3], rate-optimal algorithms can be extended easily so that they reach throughput-optimality.

  • 443.
    Charalambous, Themistoklis
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Kalyviannaki, Evangelia
    City University London.
    Hadjicostis, Christoforos N.
    Electrical and Computer Engineering Department, University of Cyprus.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Distributed Offline Load Balancing in MapReduce Networks2013In: 2013 IEEE 52ND ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC), IEEE conference proceedings, 2013, 835-840 p.Conference paper (Refereed)
    Abstract [en]

    In this paper we address the problem of balancing the processing load of MapReduce tasks running on heterogeneous clusters, i.e., clusters with different capacities and update cycles. We present a fully decentralized algorithm, based on ratio consensus, where each mapper decides the amount of workload data to handle for a single user job using only job specific local information, i.e., information that can be collected from directly connected neighboring mappers, regarding their current workload and capacity. In contrast to other algorithms in the literature, the proposed algorithm can be deployed in heterogeneous networks and can operate asynchronously in both directed and undirected communication topologies. The performance of the proposed algorithm is demonstrated via simulation experiments on large-scale strongly connected topologies. 

  • 444.
    Charalambous, Themistoklis
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Krikidis, I.
    Medium access control via contention-based distributed power control2012In: 2012 8th International Wireless Communications And Mobile Computing Conference (IWCMC), IEEE , 2012, 555-560 p.Conference paper (Refereed)
    Abstract [en]

    A successful distributed power control algorithm requires only local measurements for updating the power level of a transmitting node, so that eventually all transmitters meet their QoS requirements. Nevertheless, the problem arises when the QoS requirements cannot be achieved for all the users in the network. In this paper, a distributed algorithm for wireless ad hoc networks which is contention-based and makes use of a back off mechanism is proposed. This algorithm aims to eliminate overhead communication, improve fairness, allow nodes to operate asynchronously while establishing some performance level. The performance of the algorithm is evaluated via simulations.

  • 445.
    Chareonvisal, Tanakorn
    KTH, School of Electrical Engineering (EES), Communication Theory.
    ImplementingDistributed Storage System by Network Coding in Presence of Link Failure2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays increasing multimedia applications e.g., video and voice over IP, social networks and emails poses higher demands for sever storages and bandwidth in the networks. There is a concern that existing resource may not able to support higher demands and reliability. Network coding was introduced to improve distributed storage system. This thesis proposes the way to improve distributed storage system such as increase a chance to recover data in case there is a fail storage node or link fail in a network.

    In this thesis, we study the concept of network coding in distributed storage systems. We start our description from easy code which is replication coding then follow with higher complex code such as erasure coding. After that we implement these concepts in our test bed and measure performance by the probability of success in download and repair criteria. Moreover we compare success probability for reconstruction of original data between minimum storage regenerating (MSR) and minimum bandwidth regenerating (MBR) method. We also increase field size to increase probability of success. Finally, link failure was added in the test bed for measure reliability in a network. The results are analyzed and it shows that using maximum distance separable and increasing field size can improve the performance of a network. Moreover it also improves reliability of network in case there is a link failure in the repair process.

  • 446.
    Charvandeh, Jenny
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Location aware web access2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The user's mobile communication device has an increasing sense of where the user is. This location information may be very fine grained or very coarse. Given some amount of location information it is possible to create location aware services.

    This thesis presents and evaluates a system for location aware web browsing. Indoors the user can click on a point on a map (to establish a virtual location using a previously installed user application), outdoors the location can be provided by GPS, or the location might be provided by some other location system (indoors or outdoors), then each HTTP GET request for a URL will be augmented with information about the user's location or their virtual location. Subsequently a web query is created. Then the location information encoded as longitude and latitude is appended to this web query. The web server uses this location information to generate dynamically location aware web pages. Finally a web browser shows the web pages.

  • 447.
    Chatterjee, Saikat
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Hari, K. V. S.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Projection-based atom selection in orthogonal matching pursuit for compressive sensing2012In: 2012 National Conference on Communications, NCC 2012, IEEE , 2012, 6176797- p.Conference paper (Refereed)
    Abstract [en]

    For compressive sensing, we endeavor to improve the atom selection strategy of the existing orthogonal matching pursuit (OMP) algorithm. To achieve a better estimate of the underlying support set progressively through iterations, we use a least squares solution based atom selection method. From a set of promising atoms, the choice of an atom is performed through a new method that uses orthogonal projection along-with a standard matched filter. Through experimental evaluations, the effect of projection based atom selection strategy is shown to provide a significant improvement for the support set recovery performance, in turn, the compressive sensing recovery.

  • 448.
    Chatzaras, Anargyros
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Savvidis, Georgios
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Seamless speaker recognition2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In a technologically advanced society, the average person manages dozens of accounts for e-mail, social networks, e-banking, and other electronic services. As the number of these accounts increases, the need for automatic user identification becomes more essential. Biometrics have long been used to identify people and are the most common (if not the only) method to achieve this task.

    Over the past few years, smartphones have become frequently used gadgets.  These devices have built-in microphones and are commonly used by a single user or a small set of users, such as a couple or a family. This thesis uses a smartphone’s microphone to capture user’s speech and identify him/her. Existing speaker recognition systems typically prompt the user to provide long voice samples in order to provide accurate results. This results in a poor user experience and discourages users who do not have the patience to go through such a process.  The main idea behind the speaker recognition approach presented in this thesis is to provide a seamless user experience where the recording of the user’s voice takes place in the background.

    An Android application is developed which silently collects voices samples and performs speaker recognition without requiring extensive user interaction.  Two variants of the proposed tool have been developed and are described in depth in this thesis. The open source framework Recognito is used to perform the speaker recognition task. The analysis of Recognito showed that it is not capable of achieving high accuracy especially when the voice samples contain background noise. Finally, the comparison between the two architectures showed that they do not differ significantly in terms of performance.

  • 449.
    Chatzidrossos, Ilias
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Maximizing streaming quality in heterogeneous overlays through incentives2009In: Proceedings of the 2009 ACM Conference on Emerging Networking Experiments and Technologies, CoNEXT'09 - Co-located Student Workshop, CoNext Student Workshop '09, 2009, 35-36 p.Conference paper (Refereed)
    Abstract [en]

    The upload contribution of peers in a peer-to-peer streaming system depends on their willingness to contribute as well as their physical limitation. Several incentive schemes have been proposed to enforce non-willing peers to cooperate. But we find it of great interest to see how physically constrained, with respect to resources, peers can be supported by a streaming application. In this paper we investigate how free-riders, namely non-contributing peers, can be served in a peer-to-peer streaming system. We examine different prioritization schemes that are used by high contributing peers to prioritize other contributing peers over free-riders and show that as the level of prioritization increases, contributing peers receive higher quality but the average quality drops. To avoid this, we propose an incentive mechanism that encourages contributing peers to upload to free-riders so that the average quality experienced by the peers in the overlay is maximized.

  • 450. Chatzigiannakis, I.
    et al.
    Strikos, Andreas
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    A decentralized intrusion detection system for increasing security of wireless sensor networks2007In: ETFA 2007: 12th IEEE International Conference on Emerging Technologies and Factory Automation, IEEE , 2007, 1408-1411 p.Conference paper (Refereed)
    Abstract [en]

    Large-scale sensor networks, monitoring an environment at close range with high spatial and temporal resolutions are expected to play an important role in various applications, e.g., assessing the "health" of machines; environmental, medical, food-safety, and habitat monitoring; inventory control, building automation, etc. Ensuring the security of these complex and yet resource-constrained systems has emerged as one of the most pressing challenges for researchers. In this paper (i) we present the major threats, and (ii) we present a new approach for decentralized energy efficient intrusion detection that can be used to improve security from both external and internal adversaries.

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