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  • 201.
    Blomberg, Patrik
    KTH, Superseded Departments, Teleinformatics.
    Construction and Implementation of a Walkstation Mobile-distributed File System Testbed1995Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this Master's Thesis an investigation, design and implementation of an object-oriented prototype of a new kind of client-agent-server based distributed file system, suited for wireless mobile computing, are presented. An overview is given of the characteristics and the inherent problems of mobile-wireless computing. Some solutions and techniques to reduce the effects of these problems are described. A presentation of a project (the Walkstation project) that tries to solve these problems is also given. Software to support a mobile-distributed file system is designed and implemented. Various software development techniques and mobile file system design solutions are proposed, and used in the implementation. An integrated caching and prefetching scheme with dynamically loadable cache and prefetch manager objects is designed and implemented. It is proposed that different cache and prefetch algorithms should be used for different kinds of network links. A cache/prefetch-manager object architecture with automatically location-dependant dynamical swapping of network specific manager objects at run-time is therefore proposed and implemented. A mechanism is designed with which an application optionally can be mobility-aware by subscribing for network-change events. Finally, an expedient example of a methodology to achieve easy-understandable and well-designed code, and good extensibility possibilities is explained and used in the development. This is done by utilizing an object-oriented software development methodology in the entire software development cycle.

  • 202. Boccardi, Federico
    et al.
    Andrews, Jeffrey
    Elshaer, Hisham
    Dohler, Mischa
    Parkvall, Stefan
    KTH, School of Electrical Engineering (EES), Communication Theory. Univ Calif San Diego, San Diego.
    Popovski, Petar
    Singh, Sarabjot
    Why to Decouple the Uplink and Downlink in Cellular Networks and How To Do It2016In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 54, no 3, p. 110-117Article in journal (Refereed)
    Abstract [en]

    Ever since the inception of mobile telephony, the downlink and uplink of cellular networks have been coupled, that is, mobile terminals have been constrained to associate with the same base station in both the downlink and uplink directions. New trends in network densification and mobile data usage increase the drawbacks of this constraint, and suggest that it should be revisited. In this article we identify and explain five key arguments in favor of downlink/uplink decoupling based on a blend of theoretical, experimental, and architectural insights. We then overview the changes needed in current LTE-A mobile systems to enable this decoupling, and then look ahead to fifth generation cellular standards. We demonstrate that decoupling can lead to significant gains in network throughput, outage, and power consumption at a much lower cost compared to other solutions that provide comparable or lower gains.

  • 203.
    Bodinger, Ronnie
    KTH, Superseded Departments, Teleinformatics.
    An MPLS Connection Manager for an Edge Router1998Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Internet has been growing rapidly over the last couple of years. The increasing demand for network bandwidth is becoming a huge problem. To solve this problem, new methods must be developed. Ericsson’s solution is the use of MultiProtocol Label Switching (MPLS). MPLS has the potential to have a major impact on IP networking. It has the simplicity and dynamic nature of an IP network, but retains the performance of an ATM network. Furthermore, from an administrator’s point of view, MPLS will drastically simplify network management.

    The key principle behind MPLS is to be able to forward by switching packets through a network instead of routing packets. In order to do this, paths are established at the data link layer throughout the MPLS network. A fixed length identifier known as “label” identifies each path. Then the packets are simply forwarded on the path using layer two switching, instead of performing layer three routing.

    By using MPLS, performance is increased and it provides a good basis for traffic engineering, Quality of Service (QoS) guarantees, and Virtual Private Networks (VPN).

    I have implemented an MPLS ATM driver for an Ericsson AXI 510 Edge Router. The driver is responsible for converting generic MPLS labels into standard ATM labels (VPI/VCI). The driver also modifies the forwarding process in the router so that ATM paths are used to forward the packets, instead of the conventional forwarding methods. This implementation has been partly tested and it complies with MPLS current Internet drafts so far.

  • 204.
    Bogdanov, Kirill
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Enabling Fast and Accurate Run-Time Decisions in Geo-Distributed Systems: Better Achieving Service Level Objectives2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Computing services are highly integrated into modern society and used  by millions of people daily. To meet these high demands, many popular  services are implemented and deployed as geo-distributed applications on  top of third-party virtualized cloud providers. However, the nature of  such a deployment leads to variable performance. To deliver high quality  of service, these systems strive to adapt to ever-changing conditions by  monitoring changes in state and making informed run-time decisions, such  as choosing server peering, replica placement, and redirection of requests. In  this dissertation, we seek to improve the quality of run-time decisions made  by geo-distributed systems. We attempt to achieve this through: (1) a better  understanding of the underlying deployment conditions, (2) systematic and  thorough testing of the decision logic implemented in these systems, and (3)  by providing a clear view of the network and system states allowing services  to make better-informed decisions.  First, we validate an application’s decision logic used in popular  storage systems by examining replica selection algorithms. We do this by  introducing GeoPerf, a tool that uses symbolic execution and modeling to  perform systematic testing of replica selection algorithms. GeoPerf was used  to test two popular storage systems and found one bug in each.  Then, using measurements across EC2, we observed persistent correlation  between network paths and network latency. Based on these observations,  we introduce EdgeVar, a tool that decouples routing and congestion based  changes in network latency. This additional information improves estimation  of latency, as well as increases the stability of network path selection.  Next, we introduce Tectonic, a tool that tracks an application’s requests  and responses both at the user and kernel levels. In combination with  EdgeVar, it decouples end-to-end request completion time into three  components of network routing, network congestion, and service time.  Finally, we demonstrate how this decoupling of request completion  time components can be leveraged in practice by developing Kurma, a  fast and accurate load balancer for geo-distributed storage systems. At  runtime, Kurma integrates network latency and service time distributions to  accurately estimate the rate of Service Level Objective (SLO) violations, for  requests redirected between geo-distributed datacenters. Using real-world  data, we demonstrate Kurma’s ability to effectively share load among  datacenters while reducing SLO violations by a factor of up to 3 in high  load settings or reducing the cost of running the service by up to 17%. The  techniques described in this dissertation are important for current and future  geo-distributed services that strive to provide the best quality of service to  customers while minimizing the cost of operating the service.  

  • 205.
    Bogdanov, Kirill
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Latency Dataset for the paper "The Nearest Replica Can Be Farther Than You Think"2015Data set
  • 206.
    Bogdanov, Kirill
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Reducing Long Tail Latencies in Geo-Distributed Systems2016Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Computing services are highly integrated into modern society. Millions of people rely on these services daily for communication, coordination, trading, and accessing to information. To meet high demands, many popular services are implemented and deployed as geo-distributed applications on top of third party virtualized cloud providers. However, the nature of such deployment provides variable performance characteristics. To deliver high quality of service, such systems strive to adapt to ever-changing conditions by monitoring changes in state and making run-time decisions, such as choosing server peering, replica placement, and quorum selection.

    In this thesis, we seek to improve the quality of run-time decisions made by geo-distributed systems. We attempt to achieve this through: (1) a better understanding of the underlying deployment conditions, (2) systematic and thorough testing of the decision logic implemented in these systems, and (3) by providing a clear view into the network and system states which allows these services to perform better-informed decisions.

    We performed a long-term cross datacenter latency measurement of the Amazon EC2 cloud provider. We used this data to quantify the variability of network conditions and demonstrated its impact on the performance of the systems deployed on top of this cloud provider.

    Next, we validate an application’s decision logic used in popular storage systems by examining replica selection algorithms. We introduce GeoPerf, a tool that uses symbolic execution and lightweight modeling to perform systematic testing of replica selection algorithms. We applied GeoPerf to test two popular storage systems and we found one bug in each.

    Then, using traceroute and one-way delay measurements across EC2, we demonstrated persistent correlation between network paths and network latency. We introduce EdgeVar, a tool that decouples routing and congestion based changes in network latency. By providing this additional information, we improved the quality of latency estimation, as well as increased the stability of network path selection.

    Finally, we introduce Tectonic, a tool that tracks an application’s requests and responses both at the user and kernel levels. In combination with EdgeVar, it provides a complete view of the delays associated with each processing stage of a request and response. Using Tectonic, we analyzed the impact of sharing CPUs in a virtualized environment and can infer the hypervisor’s scheduling policies. We argue for the importance of knowing these policies and propose to use them in applications’ decision making process.

  • 207.
    Bogdanov, Kirill
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Peón-Quirós, Miguel
    Complutense University of Madrid.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Kostic, Dejan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    The Nearest Replica Can Be Farther Than You Think2015In: Proceedings of the ACM Symposium on Cloud Computing 2015, Association for Computing Machinery (ACM), 2015, p. 16-29Conference paper (Refereed)
    Abstract [en]

    Modern distributed systems are geo-distributed for reasons of increased performance, reliability, and survivability. At the heart of many such systems, e.g., the widely used Cassandra and MongoDB data stores, is an algorithm for choosing a closest set of replicas to service a client request. Suboptimal replica choices due to dynamically changing network conditions result in reduced performance as a result of increased response latency. We present GeoPerf, a tool that tries to automate the process of systematically testing the performance of replica selection algorithms for geodistributed storage systems. Our key idea is to combine symbolic execution and lightweight modeling to generate a set of inputs that can expose weaknesses in replica selection. As part of our evaluation, we analyzed network round trip times between geographically distributed Amazon EC2 regions, and showed a significant number of daily changes in nearestK replica orders. We tested Cassandra and MongoDB using our tool, and found bugs in each of these systems. Finally, we use our collected Amazon EC2 latency traces to quantify the time lost due to these bugs. For example due to the bug in Cassandra, the median wasted time for 10% of all requests is above 50 ms.

  • 208.
    Bogdanov, Kirill
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Peón-Quirós, Miguel
    Complutense University of Madrid.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Kostić, Dejan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Toward Automated Testing of Geo-Distributed Replica Selection Algorithms2015In: Proceedings of the 2015 ACM Conference on Special Interest Group on Data Communication, Association for Computing Machinery (ACM), 2015, p. 89-90Conference paper (Refereed)
    Abstract [en]

    Many geo-distributed systems rely on a replica selection algorithms to communicate with the closest set of replicas.  Unfortunately, the bursty nature of the Internet traffic and ever changing network conditions present a problem in identifying the best choices of replicas. Suboptimal replica choices result in increased response latency and reduced system performance. In this work we present GeoPerf, a tool that tries to automate testing of geo-distributed replica selection algorithms. We used GeoPerf to test Cassandra and MongoDB, two popular data stores, and found bugs in each of these systems.

  • 209.
    Bogdanov, Kirill
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Reda, Waleed
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab). Université catholique de Louvain.
    Kostic, Dejan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Canini, Marco
    KAUST.
    Kurma: Fast and Efficient Load Balancing for Geo-Distributed Storage Systems: Evaluation of Convergence and Scalability2018Report (Other academic)
    Abstract [en]

    This report provides an extended evaluation of Kurma, a practical implementation of a geo-distributed load balancer for backend storage systems. In this report we demonstrate the ability of distributed Kurma instances to accurately converge to the same solutions within 1% of the total datacenter’s capacity and the ability of Kurma to scale up to 8 datacenters using a single CPU core at each datacenter.

  • 210.
    Bogdanov, Kirill
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS.
    Reda, Waleed
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS.
    Maguire Jr., Gerald Q.
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS.
    Kostic, Dejan
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS.
    Canini, M.
    Fast and accurate load balancing for geo-distributed storage systems2018In: SoCC 2018 - Proceedings of the 2018 ACM Symposium on Cloud Computing, Association for Computing Machinery (ACM), 2018, p. 386-400Conference paper (Refereed)
    Abstract [en]

    The increasing density of globally distributed datacenters reduces the network latency between neighboring datacenters and allows replicated services deployed across neighboring locations to share workload when necessary, without violating strict Service Level Objectives (SLOs). We present Kurma, a practical implementation of a fast and accurate load balancer for geo-distributed storage systems. At run-time, Kurma integrates network latency and service time distributions to accurately estimate the rate of SLO violations for requests redirected across geo-distributed datacenters. Using these estimates, Kurma solves a decentralized rate-based performance model enabling fast load balancing (in the order of seconds) while taming global SLO violations. We integrate Kurma with Cassandra, a popular storage system. Using real-world traces along with a geo-distributed deployment across Amazon EC2, we demonstrate Kurma’s ability to effectively share load among datacenters while reducing SLO violations by up to a factor of 3 in high load settings or reducing the cost of running the service by up to 17%.

  • 211. Bohge, Mathias
    et al.
    Gross, James
    Wolisz, Mathias
    Optimal Power Masking in Soft Frequency Reuse based OFDMA Networks2009Conference paper (Refereed)
    Abstract [en]

    Soft frequency reuse is a strong tool for co-channel interference mitigation in cellular OFDMAILTE networks. The performance of such networks significantly depends on the configuration of the power masks that implement the soft frequency reuse patterns. In this paper, we investigate the performance of different power mask configurations against the optimal case, in which a central entity optimally distributes power and resource blocks among the users of the network. It is shown that large differences exist between the performance of different mask types and the optimal case in both, the overall cell throughput, as well as the cell-edge user performance.

  • 212.
    Bohge, Mathias
    et al.
    TU Berlin.
    Naghibi, Farshad
    TU Berlin.
    Wolisz, Adam
    TU Berlin.
    The use of guard bands to mitigate multiple access interference in the OFDMA uplink2008In: Proceedings of the 13th International OFDM-Workshop (InOWo),, 2008, p. 75-79Conference paper (Refereed)
    Abstract [en]

    The usual approach to mitigate multiple access interference (MAI) in the uplink of cellular OFDMA based systems is to use relatively large cyclic prefixes as time domain guard periods. In this paper, we suggest to use a combination of short time domain guard periods and frequency domain guard bands to protect against MAI instead. Guard bands can be added and removed as necessary and, thus, increase the MAI protection flexibility. We show that, if optimally applied, the use of guard bands can significantly increase the system’s uplink capacity or minimum capacity per user.

  • 213.
    Borges Vieira, Alex
    et al.
    Universidade Federal de Juiz de Fora, DCC-UFJF.
    Couto da Silva, Ana Paula
    Universidade Federal de Juiz de Fora, DCC-UFJF.
    Henrique, Francisco
    Universidade Federal de Juiz de Fora, DCC-UFJF.
    Goncalves, Glauber
    Universidade Federal de Minas Gerais, DCC-UFMG.
    de Carvalho Gomes, Pedro
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    SopCast P2P live streaming: live session traces and analysis2013In: Proceedings of the 4th ACM Multimedia Systems Conference: MMSys 2013, Association for Computing Machinery (ACM), 2013, p. 125-130Conference paper (Refereed)
    Abstract [en]

    P2P-TV applications have attracted a lot of attention fromthe research community in the last years. Such systemsgenerate a large amount of data which impacts the networkperformance. As a natural consequence, characterizingthese systems has become a very important task to developbetter multimedia systems. However, crawling data fromP2P live streaming systems is particularly challenging bythe fact that most of these applications have privateprotocols. In this work, we present a set of logs from a verypopular P2P live streaming application, the SopCast. Wedescribe our crawling methodology, and present a briefSopCast characterization. We believe that our logs and thecharacterization can be used as a starting point to thedevelopment of new live streaming systems.

  • 214.
    Borgström, Kristofer
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Multimedia Messaging Service Components for Web 2.02008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this master’s thesis is to simplify the exchange (in both directions) of multimedia content between mobile phones and network attached web servers. The solution proposed in this report specifically concerns displaying Multimedia Messaging Service (MMS) messages via a web browser connected to a network-attached web server and graphically authoring MMS messages via a web interface.

    This thesis project is important because it brings multimedia content, in the form of MMS messages, from isolation in the telecommunication world closer to wide availability via the Internet. This transition is very important as the Internet is where media is shared with the world today. This approach brings added value to end users who want to share content generated using their phone on a web site. It also provides added value to operators who want to increase the amount of MMS traffic in their networks.

    The solution is non-trivial because there are a number of complexities at both ends. This is because the MMS messages that are authored at mobile phones differ between both handset models and manufacturers. Moreover, the format used for MMS (MMS SMIL) is not widely used on the Internet, thus a transformation to an Internet browser supported format must be performed. The thesis examines to what extent this transformation can be completely automatic and how MMS messages can be authored through a web interface.

    The results show that MMS messages can be successfully transformed to HTML and embedded directly in web pages, thus providing a seamless experience for viewing MMS messages. Depending on the content of the MMS message in question, the current browser and which media player plug-ins are available, the generated HTML will be displayed differently. The results also show that MMS messages can be composed in real time* through a web interface with good results.

  • 215.
    Borison, Torbjorn
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Object Synchronization and Security for Mobile Communications Devices2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The main objective of this master’s thesis project was to investigate and find solutions to the problem of how to combine the SyncML synchronisation specification with object security and thus protection of personal information, such as contacts and calendar entries in mobile devices.

    SyncML is a new synchronisation specification agreed upon by major device developers (Ericsson, Palm, Motorola, etc.) and the major synchronisation server developers (Starfish, Puma, fusionOne, etc.). It is independent of transport (HTTP, WSP, or OBEX) platform, operating system, and application and simplifies synchronisation of personal information between dissimilar SyncML supportive devices.

    SyncML compliant devices are fully capable of synchronising information with a third party operated Internet based server and a desktop computer. This allows us to access, up-date and maintain information independent of Intranets or geographical position. However, synchronising and storing confidential personal information on an third party operated Internet based server entails weaknesses in our personal information security. Even if transport and storage security are used, how secure is the server where this information is stored since this server has the highest probability of being attacked. Can we really trust that an employee or other person with valid appropriated administrators access to the storage facility with the appropriate knowledge, working together with the third party server operator, won’t try to access our stored information? To prevent this, the personal information’s confidentiality must be guaranteed before the information leaves the device.

    When synchronising and exchanging personal information, the information is often marked according to a specific format. The three de-facto standard PIM formats are: (1) vCard (contact information), (2) vCalendar, and (3) iCalendar (calendar and scheduling information). These formats divide the personal information into properties. Each property is assigned to contain a small piece of the personal information entry (e.g. a telephone number, an e-mail address, the time when the calendar event begins, etc.).

    Furthermore to preserve the interoperability between different devices given by SyncML, authorised recipients must automatically be able to reverse the encryption process and decrypt the encrypted property value. Therefore general cryptographic formats are used (e.g. CMS, PGP and the newly developed XML Encryption). They add information needed by the recipients (e.g. algorithm used, padding method used on the plain text, etc.), encrypt the plaintext into cipher text, and decrypt the cipher text into plain text given the correct key.

  • 216.
    Borsub, Jatesada
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Papadimitratos, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Hardened registration process for participatory sensing2018In: WiSec 2018 - Proceedings of the 11th ACM Conference on Security and Privacy in Wireless and Mobile Networks, Association for Computing Machinery, Inc , 2018, p. 281-282Conference paper (Refereed)
    Abstract [en]

    Participatory sensing systems need to gather information from a large number of participants. However, the openness of the system is a double-edged sword: by allowing practically any user to join, the system can be abused by an attacker who introduces a large number of virtual devices. This poster proposes a hardened registration process for Participatory Sensing to raise the bar: registrations are screened through a number of defensive measures, towards rejecting spurious registrations that do not correspond to actual devices. This deprives an adversary from a relatively easy take-over and, at the same time, allows a flexible and open registration process.

  • 217.
    Boström, Tomas
    et al.
    KTH, Superseded Departments, Teleinformatics.
    Lindroos, Olle
    KTH, Superseded Departments, Teleinformatics.
    Hellström, Lennart
    KTH, Superseded Departments, Teleinformatics.
    Simple Mobile IP1999Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis describes an implementation and evaluation of an IP mobility management protocol, Simple Mobile IP. The protocol enables dynamic address allocation and configuration of mobile terminals through utilisation of DHCP.

    Simple Mobile IP provides IP mobility within one administrative domain, in contrast to the global mobility in conventional Mobile IP. Both protocols use IP tunnelling but in Simple Mobile IP the tunnel runs along the optimised route, thus avoiding triangular routing.

    The protocol was implemented on the Linux platform and evaluated in a wireless LAN environment. The solution detects subnet transitions at the link layer, resulting in loss of IP connectivity for approximately 100 ms when mobile terminals move between subnets. The overhead, introduced by IP tunnelling, reduces the throughput by 3.8% in a wireless LAN environment.

  • 218.
    Bratu, Vlad-Ioan
    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.
    Beckman, Claes
    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.
    Antenna Tilt Load Balancing in Self-Organizing Networks2013In: International Journal of Research in Wireless Systems, ISSN 2320-3617, Vol. 2, no 1, p. 21-26Article in journal (Other academic)
    Abstract [en]

    Base station antenna tilt is a powerful tuning parameter in traditional cellular network optimization. With theintroduction of Self-Organizing Networks (SON), this parameter may now be used also in the context of self-optimization.One envisioned scenario is load balancing (LB), where the coverage shaping properties of the antenna radiation pattern canbe used to control the cell borders. In this paper, a generalized framework for antenna tilt LB is presented and discussed. Inorder to assess the performance of antenna tilt as a tool for load balancing, simulations are performed to determine theeffect of tilt angle, vertical beamwidth and handover offset. The results show that there is a direct relation between theseparameters and the number of users that can be shifted towards neighboring cells. In conclusion, it is found that usingantennas with narrow vertical beamwidths together with small hand over offsets is an efficient way of performing loadbalancing but results also in high SIR variations.

  • 219.
    Bratu, Vlad-Ioan
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Beckman, Claes
    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.
    Base station antenna tilt for load balancing2013In: 2013 7th European Conference on Antennas and Propagation (EUCAP), New York: IEEE , 2013, p. 2039-2043Conference paper (Refereed)
    Abstract [en]

    The coverage shaping and interference reduction ability of base station antenna tilt are important tools in cellular network optimization. Through tilt changes, the coverage area of a serving cell may also be either reduced or expanded. Therefore, antenna tilt has the potential to be used for load balancing purposes. This paper gives an overview of base station antennas performance and antenna tilt. Simulations are performed in order to determine the impact of tilt changes when used for load balancing. The results show that while antenna tilt load balancing can improve the Grade of Service (GoS) in a congested cell, it will also influence the user bit rates and total cell throughput for both the congested cell and the neighbors.

  • 220.
    Bratu, Vlad-Ioan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Beckman, Claes
    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.
    Base Station Antenna Tilt for Load Balancing and Potential use in Self-Optimizating Networks2013Conference paper (Other academic)
    Abstract [en]

    The coverage shaping and interference reduction ability of base station antenna tilt are important tools in cellular network optimization. Through tilt changes, the coverage area of a serving cell may also be either reduced or expanded. Therefore, antenna tilt has the potential to be used for load balancing purposes. With the introduction of Self-Organizing Networks (SON) in the mobile communications, this parameter may now be used also in the context of self-optimization, to address the common situation where traffic has an uneven spatial distribution between serving cells. This work gives an overview of base station antennas and antenna tilt. Simulations are performed in order to determine the impact of tilt changes when used for load balancing. The effect of tilt angle, vertical beam width and handover offset are analyzed also. The results show that there is a direct relation between these parameters and the number of users that can be shifted towards neighboring cells. In conclusion, it is found that using antennas with narrow vertical beam widths together with small hand over offsets is an efficient way of performing load balancing but results also in high SIR. Although antenna tilt load balancing can improve the Grade of Service (GoS) in a congested cell, it will also influence the user bit rates and total cell throughput for both the congested cell and the neighbors.

  • 221.
    Brazalez, Astrid Algaba
    et al.
    Ericsson AB, Ericsson Res, Gothenburg, Sweden..
    Manhohni, Lars
    Ericsson AB, Ericsson Res, Gothenburg, Sweden..
    Johansson, Martin
    Ericsson AB, Ericsson Res, Gothenburg, Sweden..
    Mattsson, Martin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Implementation of a compact Ka-band parallel plate Luneburg lens based on a hybrid dielectric/metasurface unit cell2019In: 13th European Conference on Antennas and Propagation, EuCAP 2019, IEEE, 2019, article id 8740306Conference paper (Refereed)
    Abstract [en]

    The complete implementation and numerical validation of a compact cost-effective multiport parallel plate Luneburg lens antenna operating at 28 GHz is described in this paper. The lens design consists of two parallel plates separated by a gap where each of them contains a metasurface structure based on a new type of combined dielectric/holey unit cell periodically arranged in a glide-symmetric configuration. The required refractive index is achieved by a combination of coarse control by adding a dielectric in the gap, and fine tuning by changing the height of the holes. The simulations of the final prototype including a flare to ensure a smooth wave transition from the parallel plate configuration to air, as well as a coaxial-to-waveguide-to-parallel plate feeding, show a 20% bandwidth for 11.5 dB return loss, and the crosstalk remains below -15 dB for the same frequency band.

  • 222.
    Brejcha, Mikael
    KTH, Superseded Departments, Teleinformatics. KTH, School of Information and Communication Technology (ICT).
    Talaria: A Distributed Architecture for Supporting Monitoring and Collaborative Information Retrieval1999Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

     As the amount of information available via the Internet continues to explode, new means of finding and keeping oneself updated on sources of information must be found. This report presents a system that monitors sources of information on behalf of a user and also introduces new sources of information that potentially could be of interest to the user. As monitored information updates it can be directed to a variety of different displaying devices, ranging from simple pagers to advanced desktop computers. Ideas behind the design of the architecture are explained. The report explains why the system will scale as the number of users increases. The report describes measures taken to ensure user privacy.

  • 223.
    Bremstedt Pedersen, Ivan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Andersson, Alfred
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    More than downloading: Visualization of data produced by sensors in a home environment2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A home automation system usually contains a set of tools that users use to control devices in their homes, often remotely. These devices often include but are not limited to light switches, thermostats, thermometers, window blinds, and climate controls. The potential for these kinds of systems is huge because of the sheer number of devices that could be controlled and managed with minimal and inexpensive extra hardware. Many of the appliances in a normal home could benefit from being connected to a system that allows the owner to manage and control the devices in their home. Thus the number of potential devices is orders of magnitude larger than the number of homes connected to the system. There are several systems on the market that provide systems to monitor and control a home environment, however these systems only support specific in system devices. This uncovers a problem where a homeowner only has the opportunity to use specific products that fit into these systems. By introducing an open platform for the public that are not bound to any system we can allow more devices to be integrated in the home and contribute to further development of smarter homes.

    The goal with this project was to provide a scalable open platform with the possibility of asynchronous updating. This has been done by implementing multiple logical parts to both provide a web interface for the user and to allow us to handle communication and storage of data. All these parts are linked together to form a system of servers that handles all background operations. This thesis discusses and presents implementations of all of these servers, how they are implemented, communicate with each other, provide secure connections and how they can scale with increasing usage. In this process we also discuss and present techniques that were used, how to use them and their benefits, to help us reach our goal.

  • 224.
    Brenning, Magnus
    et al.
    KTH, School of Technology and Health (STH).
    Olander, Björn
    KTH, School of Technology and Health (STH).
    Orhan, Ibrahim
    KTH, School of Technology and Health (STH), Medical Engineering.
    Vennberg, Johan
    KTH, School of Technology and Health (STH).
    Lindh, Thomas
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering. 2Laboratory for communication networks, School of Electrical Engineering, KTH.
    NeTraWeb - A Web-Based Traffic Flow Performance Meter2006In: 4th Swedish National Computer Networking Workshop SNCNW 2006, 2006Conference paper (Refereed)
    Abstract [en]

    This paper presents a web-based traffic flow performance meter. The NeTraWeb tool configures and automates the measurement activities, including storage and presentation of the main performance parameters.

  • 225.
    Brewka, Lukasz
    et al.
    DTU.
    Sköldström, Pontus
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Gavler, Anders
    Acreo AB.
    Nordell, Viktor
    Acreo AB.
    Wessing, Henrik
    DTU.
    Dittmann, Lars
    DTU.
    ALPHA Proposal of mapping QoS parameters between UPnP home network and GMPLS access2011In: ACCESS NETWORKS, 2011, p. 226-239Conference paper (Refereed)
    Abstract [en]

     This paper is treating the interdomain QoS signaling between the home and access domains with a focus on applying it for providing QoS between a UPnP-QoS based home network and GMPLS based access network. The work presented here is defining a possible approach for an interface between UPnP-QoS and GMPLS in order to move towards end-to-end QoS establishment as well as investigating the complexity of such a solution. We present the QoS parameters and mechanisms in both UPnP-QoS and GMPLS and how they can be matched to create a coherent QoS architecture.

  • 226.
    Brewka, Lukasz
    et al.
    DTU.
    Sköldström, Pontus
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Telecommunication Systems Laboratory, TSLab (closed 2012-01-01).
    Gavler, Anders
    Acreo AB.
    Nordell, Viktor
    Acreo AB.
    Wessing, Henrik
    DTU.
    Dittmann, Lars
    DTU.
    QoS enabled resource allocation over an UPnP-QoS/€”GMPLS controlled edge2011In: 2011 IEEE Consumer Communications and Networking Conference, CCNC'2011, 2011, p. 218-222Conference paper (Refereed)
    Abstract [en]

    This paper focuses on the problem of coherent resource allocation within home and access networks. The interdomain QoS signaling discussed here enables the initiation of the QoS provisioning in the home and access from the end device in users home. The home network considered in this paper is UPnP-QoS enabled while the access network is GMPLS based. We propose and implement an interface between aforementioned network segments allowing for end-to-end QoS establishment. We present the QoS parameters and mechanisms in both UPnP-QoS and GMPLS and how they can be matched to create a coherent QoS architecture. Additionally we investigate the complexity of such a solution and present implementation results.

  • 227.
    Briat, Corentin
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jönsson, Ulf
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Nonlinear state-dependent delay modeling and stability analysis of internet congestion control2010In: 49TH IEEE CONFERENCE ON DECISION AND CONTROL (CDC), 2010, p. 1484-1491Conference paper (Refereed)
    Abstract [en]

    It is shown that the queuing delay involved in the congestion control algorithm is state-dependent and does not depend on the current time. Then, using an accurate formulation for buffers, networks with arbitrary topologies can be built. At equilibrium, our model reduces to the widely used setup by Paganini et al. Using this model, the delay-derivative is analyzed and it is proved that the delay time-derivative does not exceed one for the considered topologies. It is then shown that the considered congestion control algorithm globally stabilizes a delay-free single buffer network. Finally, using a specific linearization result for systems with state-dependent delays from Cooke and Huang, we show the local stability of the single bottleneck network.

  • 228.
    Briat, Corentin
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jönsson, Ulf T.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Yavuz, Emre Altug
    KTH, School of Electrical Engineering (EES), Communication Networks.
    An axiomatic fluid-flow model for congestion control analysis2011In: 2011 50th IEEE Conference on Decision and Control andEuropean Control Conference (CDC-ECC), 2011, p. 3122-3129Conference paper (Refereed)
    Abstract [en]

    An axiomatic model for congestion control isderived. The proposed four axioms serve as a basis for theconstruction of models for the network elements. It is shownthat, under some assumptions, some models of the literature canbe recovered. A single-buffer/multiple-users topology is finallyderived and studied for illustration.

  • 229.
    Briat, Corentin
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Yavuz, Emre A.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A conservation-law-based modular fluid-flow model for network congestion modeling2012In: 2012 Proceedings - IEEE INFOCOM, IEEE Computer Society, 2012, p. 2050-2058Conference paper (Refereed)
    Abstract [en]

    A modular fluid-flow model for network congestion analysis and control is proposed. The model is derived from an information conservation law stating that the information is either in transit, lost or received. Mathematical models of network elements such as queues, users, and transmission channels, and network description variables, including sending/ acknowledgement rates and delays, are inferred from this law and obtained by applying this principle locally. The modularity of the devised model makes it sufficiently generic to describe any network topology, and appealing for building simulators. Previous models in the literature are often not capable of capturing the transient behavior of the network precisely, making the resulting analysis inaccurate in practice. Those models can be recovered from exact reduction or approximation of this new model. An important aspect of this particular modeling approach is the introduction of new tight building blocks that implement mechanisms ignored by the existing ones, notably at the queue and user levels. Comparisons with packet-level simulations corroborate the proposed model.

  • 230.
    Broman, Fredrik
    et al.
    KTH, Superseded Departments, Teleinformatics.
    Tarberg, Fredrik
    KTH, Superseded Departments, Teleinformatics.
    Implementation andAnalyses of theMobile-IP Protocol1996Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report is the result of a masters degree project conducted at the Department of Teleinformatics at the Royal Institute of Technology during the autumn 1995. The area investigated is the Mobile Internet Protocol, especially its implementation and efficiency.

    The thesis work is divided into three areas. The first area includes the development and implementation of a Management Information Base for the Mobile-IP protocol. The second area deals with the porting of a Mobile-IP implementation for SunOS to MachOS and Solaris. The last area covers the tests done to measure the throughput and latency of the protocol.

  • 231.
    Broms, Daniel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Access restrictions in surrogates using Portable Channel Representation2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This Master thesis investigates how content with access restrictions can be handled in a Content Distribution Network (CDN). The thesis focuses on CDNs where the distribution is made using Portable Channel Representation (PCR), a description of content that enables installation on any platform. There has been a demand from customers for access restriction support when distributing web sites. Ranging from personal homepages wanting to restrict access using some simple password authentication protocol to corporate websites wanting HTTPS support.

    This thesis starts with a survey of available authentication mechanisms as well as available publication protocols with support for protection. This provided the basis for the design of the new protection element for PCR spanning most protection requirements. The PCR model is realized using XML in the Lokomo Software Suite. The new design has been implemented in the context of the Lokomo Software Suite. The protection has been shown to correctly install basic authentication on both Apache’s HTTP Server and Microsoft’s Internet Information Server.

  • 232.
    Brundin, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    LESpy - PCM Link Analyzer2002Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report will discuss the design of a test tool, a PCM link analyzer, LESpy. The development of LESpy is based upon reuse of C++ source code from previous test equipment from INEO, LESim. The purpose of LESpy is a tool for analyzing two telephony interfaces in Ericsson’s ”Radio in the Local Loop” system RAS 1000. Monitoring the Channel Associated Signaling (CAS) interface was the primary goal. As second goal was to find a solution to analyze the ISDN interface.

    The report presents some background information about telephony, computer telephony, the RAS 1000 system, and the development and target environment (IBM’s operating system OS/2). It also describes building blocks and functionality, i.e. the nodes, components, classes, and use cases of LESpy through UML diagrams.

    The result of the project is a test tool where most of the requirements were fulfilled through inheritance of new classes and new functionality by polymorphism. As required supervision and address signaling could be monitored and saved to a file.

  • 233.
    Buchegger, Sonja
    EPFL.
    A Robust Reputation System for Peer-to-Peer and Mobile Ad-hoc Networks2004In: Proceedings of Third Workshop on Economics of Peer-to-Peer Systems (P2PEcon), 2004, 2004Conference paper (Refereed)
  • 234.
    Buchegger, Sonja
    EPFL.
    Coping with Misbehavior in Mobile Ad-hoc Networks2004Doctoral thesis, monograph (Other academic)
    Abstract [en]

    n this work, we address the question of how to enable a system to operate despite the presence of misbehavior. Specifically, in a mobile ad-hoc network, how can we keep the network functional for normal nodes when other nodes do not route and forward correctly? Node misbehavior due to selfish or malicious reasons or faulty nodes can significantly degrade the performance of mobile ad-hoc networks. Existing approaches such as economic incentives or secure routing by cryptographic means alleviate some of the problems, but not all. For instance, nodes can still forward packets on bogus routes. We propose a protocol called CONFIDANT (Cooperation Of Nodes --- Fairness In Dynamic Ad-hoc NeTworks) to cope with misbehavior. It enables nodes to detect misbehavior by first-hand observation and use of second-hand information provided by other nodes. The view a node has about the behavior of another node is captured in a reputation system, which is used to classify nodes as misbehaving or normal. Once a misbehaving node is detected, it is isolated from the network. Reputation systems can, however, be tricked by the spread of false reputation ratings, be it false accusations or false praise. Simple solutions such as exclusively relying on one`s own direct observations have drawbacks, as they do not make use of all the information available. To solve this problem, we propose a fully distributed reputation system that can cope with false information and effectively use second-hand information in a safe way. Our approach is based on a modified Bayesian estimation and classification procedure. In our approach, each node maintains a reputation rating and a trust rating about all other nodes it cares about. Reputation ratings capture the quality of the behavior of a node as an actor in the network performing routing and forwarding tasks. From time to time first-hand reputation information is exchanged with others; using a modified Bayesian approach we designed, second-hand reputation information is only accepted if it is compatible with the current reputation rating. Reputation ratings are only slightly modified by accepted information. Trust ratings capture the quality of a node as an actor in the reputation system and reflect whether the reported first hand information summaries published by node are likely to be true. Trust ratings are updated based on the compatibility of second-hand reputation information with prior reputation ratings. We enable node redemption and prevent the sudden exploitation of good reputation built over time by introducing reputation fading. Data is entirely distributed, the reputation and trust value of a node is the collection of ratings maintained by others. We use simulation to evaluate and demonstrate the performance. We found that CONFIDANT can keep the network performance high even when up to half of the network population misbehaves. We show that our approach of using second-hand information significantly speeds up the detection of misbehaving nodes while keeping the number of false positives and negatives negligibly low.

  • 235.
    Buchegger, Sonja
    Deutsche Telekom Laboratories, TU Berlin.
    Economics of Self-Organized Networks2009Other (Refereed)
  • 236.
    Buchegger, Sonja
    et al.
    Deutsche Telekom Laboratories, TU Berlin.
    Chuang, John
    UC Berkeley.
    Economics-Informed Network Design2007Conference paper (Refereed)
  • 237.
    Buchegger, Sonja
    et al.
    Deutsche Telekom Laboratories, TU Berlin.
    Chuang, John
    UC Berkeley.
    Encouraging Cooperation Among Network Entities2007In: Cognitive Wireless Networks: Concepts, Methodologies and Visions / [ed] Frank Fitzek, Marcos Katz, Springer, 2007, p. 87-107Chapter in book (Refereed)
  • 238.
    Buchegger, Sonja
    et al.
    Deutsche Telekom Laboratories, TU Berlin.
    Krishnamurthy, Sudha
    Deutsche Telekom Laboratories, TU Berlin.
    Sensor Network Economics2007In: Handbook on Sensor Networks / [ed] Yang Xiao, Hui Chen, Frank H. Li, World Scientific, 2007, p. 835-852Chapter in book (Refereed)
  • 239.
    Buchegger, Sonja
    et al.
    EPFL.
    Le Boudec, Jean-Yves
    EPFL.
    Self-Policing Mobile Ad-hoc Networks2004In: Handbook on Mobile Computing, CRC Press, 2004, p. 395-413Chapter in book (Refereed)
  • 240.
    Buchegger, Sonja
    et al.
    EPFL.
    Tissieres, Cedric
    EPFL.
    Le Boudec, Jean-Yves
    EPFL.
    A Test-Bed for Misbehavior Detection in Mobile Ad-hoc Networks: How Much can Watchdogs Really Do?2004In: SIXTH IEEE WORKSHOP ON MOBILE COMPUTING SYSTEMS AND APPLICATIONS, PROCEEDINGS, 2004, p. 102-111Conference paper (Refereed)
    Abstract [en]

    Several misbehavior detection and reputation systems have been proposed for mobile ad-hoc networks, relying on direct network observation mechanisms, so-called watchdogs. While these approaches have so far only been evaluated in simulations and restricted to selfish packet dropping, we are interested in the capabilities of a watchdog detection component in a real network. In this paper we present our test-bed implementation of misbehavior detection. Following an evaluation of both the feasibility and detectability of attacks on routing and forwarding in the Dynamic Source Routing (DSR) protocol, we present the design of our test-bed. In order to add detection capabilities, we extend the concept of passive acknowledgment by mechanisms for partial dropping, packet modification, and fabrication detection. We combine DSR with Netfilter and APE to enable detection. We implement both attackers and detection and show their feasibility and limitations.

  • 241.
    Bude, Cristian
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Kervefors Bergstrand, Andreas
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Internet of Things: Exploring and Securing a Future Concept2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Internet of Things (IoT) is a concept that encompasses various objects and methods of communication to exchange information. Today IoT is more a descriptive term of a vision that everything should be connected to the internet. IoT will be fundamental in the future because the concept opens up opportunities for new services and new innovations. All objects will be connected and able to communicate with each other, while they operate in unprotected environments. This later aspect leads to major security challenges.

    Today, IoT is in great need of standardization and clear architectures that describe how this technology should be implemented and how IoT devices interact with each other in a secure manner. The security challenges are rooted in the technology and how information is acquired and manipulated by this technology. This thesis provides an introduction to what the IoT is and how it can be used as well as some of the threats that IoT may face in regards to information security. In addition, the thesis provides the reader with some suggestions about how to potentially solve the fundamental need for authentication and secure communications. The solutions presented are based on both contemporary solutions and technologies that are under development for the future. Contemporary solutions are based on security protocols such as IPSec and DTLS. These protocols are being used in an environment that extends across the Internet and into a 6LoWPAN network. The proposed authentication solution has been developed based on a public key infrastructure and trust models for certificate management.

    As future work, the thesis presents several research areas where this thesis can be used as a basis. These specialization areas include further analysis of vulnerabilities and an implementation of the proposed solutions.

  • 242.
    Bugiel, Sven
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture (Closed 20120101), Communication Systems, CoS (closed 2012-01-01).
    Ekberg, J. -E
    Implementing an application-specific credential platform using late-launched mobile trusted module2010In: STC '10 Proceedings of the fifth ACM workshop on Scalable trusted computing, 2010, p. 21-30Conference paper (Refereed)
    Abstract [en]

    Contemporary trusted execution environments provide a good foundation for implementing secure user credentials, but these are not properly bound to the application instances that implement their use. This paper introduces a framework for application-specific credentials and provides a prototype implementation using TCG MTM and DRTM technologies. Measurements and a security analysis is presented for the realised architecture.

  • 243.
    Bui, Minh N.
    et al.
    Concordia University.
    Jaumard, Brigitte
    Concordia University.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Mukherjee, Biswanath
    University of California - Davis.
    Design of a survivable VPN topology over a service provider network2013In: 2013 9th International Conference on the Design of Reliable Communication Networks (DRCN), IEEE conference proceedings, 2013, p. 71-78Conference paper (Refereed)
    Abstract [en]

    Survivability in IP-over-WDM networks has alreadybeen extensively discussed in a series of studies. Up to date,most of the studies assume single-hop working routing of trafficrequests. In this paper, we study the multi layer survivable designof a logical topology in the context of multiple-hop workingrouting for IP layer traffic requests. The design problem iscomposed of two problems which are simultaneously solved:(i) Finding the most efficient or economical multi-hop routingof the IP traffic flows with different bandwidth granularitiesover the logical topology, which involves some traffic grooming,(ii) Ensuring that the logical topology is survivable throughoutan appropriate mapping of the logical links over the physicaltopology, if such a mapping exists.In order to solve such a complex multi layer resilient networkdesign problem, we propose a column generation ILP model. Itallows exploiting the natural decomposition of the problem andhelps devising a scalable solution scheme.We conducted numerical experiments on a German networkwith 50 nodes and 88 physical links. Not only we could solve muchlarger data instances than those published in the literature, butalso observe than multi-hop routing allows a saving of up to 10%of the number of lightpaths, depending on the traffic load.

  • 244. Bulakci, O.
    et al.
    Gutierrez-Estevez, D. M.
    Ericson, M.
    Prasad, A.
    Pateromichelakis, E.
    Calochira, G.
    Belschner, J.
    Arnold, P.
    Moya, F. Sanchez
    Ibrahim, A. M.
    Bronzino, F.
    Čelik, Haris
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Fodor, G.
    An Agile Resource Management Framework for 5G2017Conference paper (Refereed)
    Abstract [en]

    This paper presents the design foundations of an agile resource management (RM) framework for the fifth generation (5G) radio access network (RAN) by describing essential building blocks (BBs). Overall, the presented RM framework provides holistic RM solutions that consider and exploit the novel aspects of 5G systems, such as, diverse service requirements, co-existence of multiple air interface (AI) variants (AIVs) in the overall AI, dynamic radio topologies, and novel communication modes. The proposed framework encompasses the following key BBs: Advanced interference management techniques for dense and dynamic deployments; dynamic traffic steering mechanisms that aim to attain the optimum mapping of 5G services to any available resources when and where needed by considering the peculiarities of different AIVs; tight interworking between novel 5G AIVs and evolved legacy AIVs such as Longterm Evolution (LTE); sharing of a common RAN by multiple network slices; RAN moderation techniques to attain energy efficiency gains; and functional extensions in the device measurement context to enable all the above new functionalities. The BBs are analyzed from the perspectives of key findings and RAN design implications.

  • 245. Byamukama, Maximus
    et al.
    Nannono, Janet Nakato
    Ruhinda, Kabonire
    Pehrson, Björn
    KTH.
    Nsabagwa, Mary
    Akol, Roselyn
    Olsson, Robert
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Bakkabulindi, Geoffrey
    Kondela, Emmanuel
    Design Guidelines for Ultra-low Power Gateways in Environment Monitoring Wireless Sensor Networks2017In: 2017 IEEE AFRICON / [ed] Cornish, D R, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1472-1478Conference paper (Refereed)
    Abstract [en]

    We explore techniques that can be used to reduce the power consumption of gateways in wireless sensor networks deployed in environment monitoring applications, such as Automatic Weather Stations (AWS). The challenge is the deployment of these networks in locations that are far from a consistent power source, such as a national grid. Such stations must be autonomous and power consumption must be minimized. We present test scenarios illustrating the impact of the suggested techniques. We explore hardware and software based methods of power reduction, assess the impact of each, the constraints to be expected and how to overcome them. We then provide a reference implementation of a gateway in which we integrate these techniques. We show that power consumption can be reduced by 48 - 85% when comparing best and worst case scenarios. The reference implementation we provide consumes 27mW at 3V.

  • 246.
    Byttner, Anders
    KTH, Superseded Departments, Teleinformatics.
    Internet Telephony using the Session Initiation Protocol2000Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Session Initiation Protocol (SIP) is a highly extensible signaling protocol that provides mechanisms for establishing, modifying, and tearing down Internet telephony calls. Together with other Internet protocols and API’s it can create a flexible, dynamic, and scalable telephony environment, where services can be developed and deployed rapidly and by a wide range of users.

    This report investigates some proposed extensions to SIP and some of the API's that aim to standardize how telephony services can be defined in a SIP enabled network. The report describes some changes and improvements to these proposals and demonstrates how different services can be implemented using them.

  • 247.
    Börjesson, Martin
    KTH, Superseded Departments, Teleinformatics.
    Creation & Deployment of Voice Browsing Services1999Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Making the World Wide Web accessible trough audio interfaces (voice browsing) would provide many benefits. Far more people today have access to phones than have access to computers, further more, cellular phones allow user-mobility. Traditional Interactive Voice Response (IVR) applications have so far been restricted to the POTS network. However, a combination of Internet and IVR technologies could make voice browsing on the WWW possible. IVR services can with many benefits be described with customised markup languages instead of the traditional programming languages that are used today. The services can be published on the web using the same tools as in graphical Web publishing.

    In this paper, existing conversational markup languages are presented and evaluated together with suggestions for improvements. The benefits of the Extensible Markup Language in web publishing are studied with the conclusion that it would provide the best available base a future conversational markup standard.

    Requirements for a voice browser are suggested and possible media platforms are evaluated and discussed. The design of a voice browser is presented and discussed together with experiences gained from an implementation task.

    This paper concludes that voice browsing on the WWW will become a common way of web interaction within a not too distant future. The techniques necessary already exists. The benefits and opportunities that it offers will drive the development of necessary standards as well as the growth of content provide[r]s and users[.]

  • 248.
    Bülow, Jonas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Mobile IP and AAA Services2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Networks providing Authentication, Authorization and Accounting services are found all over the world. The number of mobile devices is growing rapidly and the need to have a seamless, user friendly, and stable integration between mobile devices and AAA enabled networks is an important development trend right now.

    This thesis will give an overview of the work taking place in the field of AAA and Mobile IP. Issues when Mobile IP and AAA meet will be discussed.

    The thesis will describe sample tests of a Mobile IP network and a simple test using the forthcoming AAA protocol Diameter.

    Conclusions based on these tests are described along with some obvious future work.

  • 249. Caballero Bayerri, Juan
    et al.
    Malmkvist, Daniel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Experimental Study of a Network Access Server for a public WLAN access network2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wireless access networks have gained popularity due to the flexibility they allow the user, who is able to move away from his or her desk while still being able to access information. Among the different Wireless LAN standards, the most widespread, by far, is IEEE 802.11.

    Public WLAN access networks are being set up in hotspots, i.e. areas expected to have high demand for bandwidth. Access to the Internet and to corporate networks is provided at these hotspots with limited coverage but high available bandwidth. Airports and hotels have often been the first targeted locations for these hotspots, but conference centres, cafes, and train stations follow. In the near future, any person who owns at least one access point and has a connection to the Internet can become a small operator and offer access to the Internet using these resources.

    Existing solutions for such WLAN access networks lack support for security, flexible accounting, mobility, multiaccess, roaming and user-friendly login. The aim of this Master's Thesis was to study if it was possible to solve these problems and how to integrate all this new functionality into existing public WLAN access networks by building and evaluating a prototype of a public WLAN access network

    System requirements were defined, currently available solutions analysed and a prototype was built. Most of the functionality of the prototype is placed in the Network Access Server, which is the main element providing security, mobility, and accounting.

    Flexible accounting, improvements in security, an easy and fast way to login the user, a feedback module to provide information about the current session and integration of the RADIUS architecture with the Mobile IP distribution have all been implemented.

  • 250.
    Cabarkapa, Dragan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Authorization Architecture for SWoT2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Social Web of Things (SWoT) is a user centric framework which facilitates interaction between software agents deployed on smart things and in the cloud. Software agents deployed on smart things are remotely accessible, host sensitive resources, and often represent high value targets. SWoT currently does not feature adequate security mechanisms which could protect software agents from unauthorized access. In this thesis, we aim to rectify this deficiency by introducing platform independent, exible, and user centric authorization mechanism inSWoT.

    We derive requirements and design of abstract authorization architecture from the preceding seminal work performed in SENSEI project. SENSEI and SWoT share same problem domain, but while SENSEI addresses enterprise use cases SWoT focusses on consumer use cases. This single but fundamental difference motivates adaptations of SENSEI contributions for application in SWoT. To realize concrete authorization architecture we perform extensive study of various authorization solutions. Results of our study indicate that novel User Managed Access (UMA) protocol represents promising solution for SWoT.

    We present the Authorization as a Service solution for SWoT framework, based on UMA protocol. This solution enables users to manage and control communication between software agents deployed on smart things and in the cloud from single centralized location. It also features runtime association of software agents, management, evaluation, and enforcement of access permissions for resources provided by software agents.

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