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  • 1.
    Abad Camarero, Daniel
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Performance analysis of IPv4 / IPv6 protocols over the third generation mobile network2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Currently, the IPv4 protocol is heavily used by institutions, companies and individuals, but every day there is a higher number of devices connected to the network such as home appliances, mobile phones or tablets. Each machine or device needs to have its own IP address to communicate with other machines connected to Internet. This implies the need for multiple IP addresses for a single user and the current protocol begins to show some deficiencies due to IPv4 address space exhaustion. Therefore, for several years experts have been working on an IP protocol update: the IPv6 128-bit version can address up to about 340 quadrillion system devices concurrently. With IPv6, today, every person on the planet could have millions of devices simultaneously connected to the Internet.

    The choice of the IP protocol version affects the performance of the UMTS mobile network and the browsers as well. The aim of the project is to measure how the IPv6 protocol performs compared to the previous IPv4 protocol. It is expected that the IPv6 protocol generates a smaller amount of signalling and less time is required to fully load a web page. We have analysed some KPIs (IP data, signalling, web load time and battery) in lab environment using Smartphones, to observe the behaviour of both, the network and the device.  The main conclusion of the thesis is that IPv6 really behaves as expected and generates savings in signalling, although the IP data generated is larger due to the size of the headers. However, there is still much work as only the most important webpages and the applications with a high level of market penetration operate well over the IPv6 protocol.

  • 2.
    Abdi Kelishami, Alireza
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Secure Privacy-Friendly Instant Messaging (IM) for Guidepal2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It is fascinating, and yet often neglected, that a user’s privacy can be invaded notonly by the absence of security measures and mechanisms, but also by improperor inadequate usage of security services and mechanisms. When designingsecure systems, we must consider what services are needed and what is not.The work in this thesis revolves around privacy-friendly instant messaging (IM)systems. In such a system, an inadequate usage of security measures leads tohaving IM servers being able to intercept or gather users’ private conversations.An improper usage of security measures could bring about non-repudiationwhich is desirable when signing contracts, but unwelcome in IM and privateconversations.We will look into requirements of the desired IM system, study the currentstate-of-the-art solutions, deploy an IM server, and briefly extend an existingmodern privacy-friendly IM protocol and an open source mobile application tomeet our security and privacy requirements. This extended IM application iscalled Guidepal-IM and is available as open source1The thesis work is introduced and carried out at Guidepal, a startup companyin Stockholm. It is therefore supervised partly at Guidepal and partly at KTH.Since Guidepal is also looking into possibilities of integrating an IM featureto its current social media apps, our contribution would also briefly extend tostudying the limitations and recommendations for Guidepal’s social media appto help user privacy preservation.

  • 3.
    Adam, Constantin
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Implementation and evaluation of a middleware for self-organizing decentralized web services2006In: Integrated Network Management IX: MANAGING NEW NETWORKED WORLDS, 2006, Vol. 3996, 1-14 p.Conference paper (Refereed)
    Abstract [en]

    We present the implementation of Chameleon, a peer-to-peer middleware for self-organizing web services, and we provide evaluation results from a test bed. The novel aspect of Chameleon is that key functions, including resource allocation, are decentralized, which facilitates scalability and robustness of the overall system. Chameleon is implemented in Java on the Tomcat web server environment. The implementation is non-intrusive in the sense that it does not require code modifications in Tomcat or in the underlying operating system. We evaluate the system by running the TPC-W benchmark. We show that the middleware dynamically and effectively reconfigures in response to changes in load patterns and server failures, while enforcing operating policies, namely, QoS objectives and service differentiation under overload.

  • 4.
    Adam, Constantin
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Service middleware for self-managing large-scale systems2007In: IEEE Transactions on Network and Service Management, ISSN 1932-4537, Vol. 4, no 3, 50-64 p.Article in journal (Refereed)
    Abstract [en]

    Resource management poses particular challenges in large-scale systems, such as server clusters that simultaneously process requests from a large number of clients. A resource management scheme for such systems must scale both in the in the number of cluster nodes and the number of applications the cluster supports. Current solutions do not exhibit both of these properties at the same time. Many are centralized, which limits their scalability in terms of the number of nodes, or they are decentralized but rely on replicated directories, which also reduces their ability to scale. In this paper, we propose novel solutions to request routing and application placementtwo key mechanisms in a scalable resource management scheme. Our solution to request routing is based on selective update propagation, which ensures that the control load on a cluster node is independent of the system size. Application placement is approached in a decentralized manner, by using a distributed algorithm that maximizes resource utilization and allows for service differentiation under overload. The paper demonstrates how the above solutions can be integrated into an overall design for a peer-to-peer management middleware that exhibits properties of self-organization. Through complexity analysis and simulation, we show to which extent the system design is scalable. We have built a prototype using accepted technologies and have evaluated it using a standard benchmark. The testbed measurements show that the implementation, within the parameter range tested, operates efficiently, quickly adapts to a changing environment and allows for effective service differentiation by a system administrator.

  • 5.
    Adam, Constantin
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Tang, Chunqiang
    Steinder, Malgorzata
    Spreitzer, Michael
    A service middleware that scales in system size and applications2007In: 2007 10TH IFIP/IEEE INTERNATIONAL SYMPOSIUM ON INTEGRATED NETWORK MANAGEMENT (IM 2009): VOLS 1 AND 2, NEW YORK: IEEE , 2007, 70-79 p.Conference paper (Refereed)
    Abstract [en]

    We present a peer-to-peer service management middleware that dynamically allocates system resources to a large set of applications. The system achieves scalability in number of nodes (1000s or more) through three decentralized mechanisms that run on different time scales. First, overlay construction interconnects all nodes in the system for exchanging control and state information. Second, request routing directs requests to nodes that offer the corresponding applications. Third, application placement controls the set of offered applications on each node, in order to achieve efficient operation and service differentiation. The design supports a large number of applications (100s or more) through selective propagation of configuration information needed for request routing. The control load on a node increases linearly with the number of applications in the system. Service differentiation is achieved through assigning a utility to each application which influences the application placement process. Simulation studies show that the system operates efficiently for different sizes, adapts fast to load changes and failures and effectively differentiates between different applications under overload.

  • 6.
    Afridi, Ayaz Khan
    KTH, School of Electrical Engineering (EES), Communication Networks.
    MACRO AND FEMTO NETWORK ASPECTS FOR REALISTIC LTE USAGE SCENARIOS2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 7.
    Aghakhanian Fereydani, Behrooz
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Secure Vehicular Communication Systems: Cross-Domain VPKI, Design and Implementation2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Enabling communication among vehicles on the road has advantages, but it also introduces a number of security drawbacks. A Vehicular PKI (VPKI) provides an infrastructure that brings security and privacy within the VPKI domain. But when it comes to establishing a trust model among multiple VPKI domains, a new trust model is needed in order to facilitate travelling across domains. This project proposes an approach and partially implements a scalable and efficient Cross-Domain VPKI trust model that, first, enables VPKI domains to establish different levels of trust with each other and, second, it suggests that a Domain CA (DCA) in each domain to evaluate trustworthiness of vehicle’s Long Term Certificate (LTC). As result, CAs in VPKI domains will have more granular control over issuing pseudonym Foreign Certificates for a vehicle that travels into their domain.

  • 8.
    Agrawal, Vivek
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Performance evaluation of Group Signature schemes in Vehicular Communication: A feasibility study for Vehicular Communication2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this work is to show the effectiveness of techniques that allow a user to maintain its privacy and anonymity while participating in real word scenario. Users need to communicate with each other in many situations in order to share information. This creates the danger of the user’s privacy being breached and it can discourage users from taking active participation in any information sharing task. There are many real scenarios or application where users want to remain anonymous while having their communication secured. This is so in vehicular communication systems.

    Group signatures are versatile cryptographic tools that are suitable when we need security and privacy protection. A group signature scheme allows members of a group to sign messages on behalf of the group. Any receiver can verify the message validity but cannot discover the identity of the sender from the signed message or link two or more messages from the same signer. However, the identity of the signer can be discovered by an authority using a signed message. For this reason, Group Signature schemes were proposed in the context of vehicular communication systems. In this context, communication and computation overheads are critical. Thus, the focus of this thesis is to implement and compare different group signature schemes in terms of overhead introduced due to processing cost, and analytically evaluate their suitability for vehicular communication scenarios.

     

  • 9.
    Ahmad, Muhammad Bilal
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Macro and Femto Network Aspectsfor Realistic LTE usage scenarios with Interference Management2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 10. Ahmed, J.
    et al.
    Johnsson, A.
    Yanggratoke, Rerngvit
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Networks.
    Ardelius, J.
    Flinta, C.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Predicting SLA conformance for cluster-based services using distributed analytics2016In: Proceedings of the NOMS 2016 - 2016 IEEE/IFIP Network Operations and Management Symposium, IEEE conference proceedings, 2016, 848-852 p.Conference paper (Refereed)
    Abstract [en]

    Service assurance for the telecom cloud is a challenging task and is continuously being addressed by academics and industry. One promising approach is to utilize machine learning to predict service quality in order to take early mitigation actions. In previous work we have shown how to predict service-level metrics, such as frame rate for a video application on the client side, from operational data gathered at the server side. This gives the service provider early indications on whether the platform can support the current load demand. This paper extends previous work by addressing scalability issues for cluster-based services. Operational data being generated in large volumes, from several sources, and at high velocity puts strain on computational and communication resources. We propose and evaluate a distributed machine learning system based on the Winnow algorithm to tackle scalability issues, and then compare the new distributed solution with the previously proposed centralized solution. We show that network overhead and computational execution time is substantially reduced while maintaining high prediction accuracy making it possible to achieve real-time service quality predictions in large systems.

  • 11.
    Alexiou, Nikolaos
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Basagiannis, S.
    Petridou, S.
    Formal security analysis of near field communication using model checking2016In: Computers & security (Print), ISSN 0167-4048, E-ISSN 1872-6208, Vol. 60, 1-14 p.Article in journal (Refereed)
    Abstract [en]

    Near field communication (NFC) is a short-range wireless communication technology envisioned to support a large gamut of smart-device applications, such as payment and ticketing. Although two NFC devices need to be in close proximity to communicate (up to 10 cm), adversaries can use a fast and transparent communication channel to relay data and, thus, force an NFC link between two distant victims. Since relay attacks can bypass the NFC requirement for short-range communication cheaply and easily, it is important to evaluate the security of NFC applications. In this work, we present a general framework that exploits formal analysis and especially model checking as a means of verifying the resiliency of NFC protocol against relay attacks. Toward this goal, we built a continuous-time Markov chain (CTMC) model using the PRISM model checker. Firstly, we took into account NFC protocol parameters and, then, we enhanced our model with networking parameters, which include both mobile environment and security-aware characteristics. Combining NFC specifications with an adversary's characteristics, we produced the relay attack model, which is used for extracting our security analysis results. Through these results, we can explain how a relay attack could be prevented and discuss potential countermeasures.

  • 12.
    Alexiou, Nikolaos
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Basagiannis, S.
    Petridou, S.
    Security analysis of NFC relay attacks using probabilistic model checking2014In: IWCMC 2014 - 10th International Wireless Communications and Mobile Computing Conference, IEEE , 2014, 524-529 p.Conference paper (Refereed)
    Abstract [en]

    Near Field Communication (NFC) is a short-ranged wireless communication technology envisioned to support a large gamut of smart-device applications, such as payment and ticketing applications. Two NFC-enabled devices need to be in close proximity, typically less than 10 cm apart, in order to communicate. However, adversaries can use a secret and fast communication channel to relay data between two distant victim NFC-enabled devices and thus, force NFC link between them. Relay attacks may have tremendous consequences for security as they can bypass the NFC requirement for short range communications and even worse, they are cheap and easy to launch. Therefore, it is important to evaluate security of NFC applications and countermeasures to support the emergence of this new technology. In this work we present a probabilistic model checking approach to verify resiliency of NFC protocol against relay attacks based on protocol, channel and application specific parameters that affect the successfulness of the attack. We perform our formal analysis within the probabilistic model checking environment PRISM to support automated security analysis of NFC applications. Finally, we demonstrate how the attack can be thwarted and we discuss the successfulness of potential countermeasures.

  • 13.
    Alexiou, Nikolaos
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Gisdakis, Stylianos
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Laganà, Marcello
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Papadimitratos, Panagiotis
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Towards a secure and privacy-preserving multi-service vehicular architecture2013In: 2013 IEEE 14th International Symposium on a World of Wireless, Mobile and Multimedia Networks, WoWMoM 2013, IEEE , 2013, 6583472- p.Conference paper (Refereed)
    Abstract [en]

    Intensive efforts in industry, academia and standardization bodies have brought vehicular communications (VC) one step before commercial deployment. In fact, future vehicles will become significant mobile platforms, extending the digital life of individuals with an ecosystem of applications and services. To secure these services and to protect the privacy of individuals, it is necessary to revisit and extend the vehicular Public Key Infrastructure (PKI)-based approach towards a multi-service security architecture. This is exactly what this work does, providing a design and a proof-of-concept implementation. Our approach, inspired by long-standing standards, is instantiated for a specific service, the provision of short-term credentials (pseudonyms). Moreover, we elaborate on its operation across multiple VC system domains, and craft a roadmap for further developments and extensions that leverage Web-based approaches. Our current results already indicate our architecture is efficient and can scale, and thus can meet the needs of the foreseen broad gamut of applications and services, including the transportation and safety ones.

  • 14.
    Alexiou, Nikolaos
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Laganá, Marcello
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Gisdakis, Stylianos
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Khodaei, Mohammad
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Papadimitratos, Panagiotis
    KTH, School of Electrical Engineering (EES), Communication Networks.
    VeSPA: Vehicular security and privacy-preserving architecture2013In: HotWiSec 2013: Proceedings of the 2013 ACM Workshop on Hot Topics on Wireless Network Security and Privacy, 2013, 19-23 p.Conference paper (Refereed)
    Abstract [en]

    Vehicular Communications (VC) are reaching a near deploment phase and will play an important role in improving road safety, driving efficiency and comfort. The industry and the academia have reached a consensus for the need of a Public Key Infrastructure (PKI), in order to achieve security, identity management, vehicle authentication, as well as preserve vehicle privacy. Moreover, a gamut of proprietary and safety applications, such as location-based services and pay-as-you-drive systems, are going to be offered to the vehicles. The emerging applications are posing new challenges for the existing Vehicular Public Key Infrastructure (VPKI) architectures to support Authentication, Authorization and Accountability (AAA), without exposing vehicle privacy. In this work we present an implementation of a VPKI that is compatible with the VC standards. We propose the use of tickets as cryptographic tokens to provide AAA and also preserve vehicle privacy against adversaries and the VPKI. Finally, we present the efficiency results of our implementation to prove its applicability.

  • 15.
    Ali, Raja Hashim
    et al.
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Bark, Mikael
    KTH, School of Information and Communication Technology (ICT).
    Miro, Jorge
    KTH, School of Information and Communication Technology (ICT).
    Muhammad, Sayyed Auwn
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Sjöstrand, Joel
    Stockholm University.
    Zubair, Syed Muhammad
    KTH, School of Electrical Engineering (EES), Communication Networks. University of Balochistan, Pakistan.
    Abbas, Raja Manzar
    Arvestad, Lars
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    VMCMC: a graphical and statistical analysis tool for Markov chain Monte Carlo tracesManuscript (preprint) (Other academic)
    Abstract [en]

    Motivation: MCMC-based methods are important for Bayesian inference of phylogeny and related parameters. Although being computationally expensive, MCMC yields estimates of posterior distributions that are useful for estimating parameter values and are easy to use in subsequent analysis. There are, however, sometimes practical diculties with MCMC, relating to convergence assessment and determining burn-in, especially in large-scale analyses. Currently, multiple software are required to perform, e.g., convergence, mixing and interactive exploration of both continuous and tree parameters.

    Results: We have written a software called VMCMC to simplify post-processing of MCMC traces with, for example, automatic burn-in estimation. VMCMC can also be used both as a GUI-based application, supporting interactive exploration, and as a command-line tool suitable for automated pipelines.

    Availability: VMCMC is available for Java SE 6+ under the New BSD License. Executable jar les, tutorial manual and source code can be downloaded from https://bitbucket.org/rhali/visualmcmc/.

  • 16.
    Ali, Raja Hashim
    et al.
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST). KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Bark, Mikael
    KTH, School of Information and Communication Technology (ICT).
    Miró, Jorge
    KTH, School of Information and Communication Technology (ICT).
    Muhammad, Sayyed Auwn
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST). KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Sjöstrand, J.
    Zubair, Syed M.
    KTH, School of Electrical Engineering (EES), Communication Networks. University of Balochistan, Pakistan.
    Abbas, R. M.
    Arvestad, L.
    VMCMC: A graphical and statistical analysis tool for Markov chain Monte Carlo traces2017In: BMC Bioinformatics, ISSN 1471-2105, E-ISSN 1471-2105, Vol. 18, no 1, 97Article in journal (Refereed)
    Abstract [en]

    Background: MCMC-based methods are important for Bayesian inference of phylogeny and related parameters. Although being computationally expensive, MCMC yields estimates of posterior distributions that are useful for estimating parameter values and are easy to use in subsequent analysis. There are, however, sometimes practical difficulties with MCMC, relating to convergence assessment and determining burn-in, especially in large-scale analyses. Currently, multiple software are required to perform, e.g., convergence, mixing and interactive exploration of both continuous and tree parameters. Results: We have written a software called VMCMC to simplify post-processing of MCMC traces with, for example, automatic burn-in estimation. VMCMC can also be used both as a GUI-based application, supporting interactive exploration, and as a command-line tool suitable for automated pipelines. Conclusions: VMCMC is a free software available under the New BSD License. Executable jar files, tutorial manual and source code can be downloaded from https://bitbucket.org/rhali/visualmcmc/.

  • 17.
    Al-Zubaidy, Hussein
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Liebeherr, Jörg
    Service Characterizations for Multi-Hop Multiaccess Wireless Networks2014In: 2014 IEEE CONFERENCE ON COMPUTER COMMUNICATIONS WORKSHOPS (INFOCOM WKSHPS), 2014, 807-812 p.Conference paper (Refereed)
    Abstract [en]

    The objective of a wireless multiaccess communication system is to distribute limited wireless channel resources efficiently and fairly among its users. Solutions for multiaccess communications have been approached with very different perspectives of the same problem, among them information-theoretic approaches at the physical layer, random access at the media access layer, and packet scheduling at the link or network layer. Different system models with sometimes incongruent assumptions make it difficult to compare or reconcile multiaccess solutions emerging from different areas. In this paper we address these difficulties by presenting system-theoretic characterizations of the available service in multiaccess networks for all three approaches. Using these characterizations we derive performance bounds of multiaccess systems that see bursty traffic. We take advantage of a recently proposed (min, x) network calculus, which enables the analysis of networks with time-variable traffic (in bits per second) in terms of the fading channels parameters, i.e., signal-to-noise ratio (in dB). For each of the multiaccess approaches considered, we are able to compute probabilistic performance bounds for multi-hop wireless channels. The numerical results shed light on fundamental tradeoffs offered by each of these approaches.

  • 18.
    Al-Zubaidy, Hussein Mohammed
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Fodor, Viktoria
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Performance of in-network processing for visual analysis in wireless sensor networks2015In: Proceedings of 2015 14th IFIP Networking Conference, IFIP Networking 2015, IEEE conference proceedings, 2015Conference paper (Refereed)
    Abstract [en]

    Nodes in a sensor network are traditionally used for sensing and data forwarding. However, with the increase of their computational capability, they can be used for in-network data processing, leading to a potential increase of the quality of the networked applications as well as the network lifetime. Visual analysis in sensor networks is a prominent example where the processing power of the network nodes needs to be leveraged to meet the frame rate and the processing delay requirements of common visual analysis applications. The modeling of the end-to-end performance for such networks is, however, challenging, because in-network processing violates the flow conservation law, which is the basis for most queuing analysis. In this work we propose to solve this methodological challenge through appropriately scaling the arrival and the service processes, and we develop probabilistic performance bounds using stochastic network calculus. We use the developed model to determine the main performance bottlenecks of networked visual processing. Our numerical results show that an end-to-end delay of 2-3 frame length is obtained with violation probability in the order of 10-6. Simulation shows that the obtained bounds overestimates the end-to-end delay by no more than 10%.

  • 19.
    Amoozadeh, Mani
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Certificate Revocation List Distribution in Vehicular Communication Systems2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Message exchange in VANETs should be secured. Researchers have designed many methods to meet this goal. One of the ways agreed upon by most researchers, is through the use of a public-key infrastructure (PKI). An important part of any PKI system is certificate revocation. The revocation is usually done by periodically issuing a Certificate Revocation List (CRL) by the Certification Authority (CA). After the creation of a CRL by CA, the CRL should be distributed in the VC system. The important question is how we can distribute the CRL efficiently and in a timely manner throughout the system in a way that all vehicles receive a genuine copy of it. A couple of researches considered CRL distribution in the past and proposed different methods like RSU-only [1], C2C Epidemic [2], and Most Pieces Broadcast (MPB) [3]. We implement the aforementioned CRL distribution methods and evaluate them using a common framework. With this approach, we can compare these methods accurately and point out the limitations of each. Due to the fact that C2C Epidemic did not provide any packet-level implementation, we propose an implementation for it. We also propose a new method for CRL distribution called ICE (Intelligent CRL Exchange). This method uses V2V and I2V communication to distribute the CRL pieces to vehicles. ICE is an enhanced version of the MPB method and it uses semi-incremental CRL exchange. With this approach, the number of duplicate received pieces decreases in comparison to the MPB method. Moreover, ICE uses a simple approach to decrease the number of unnecessary broadcasts by RSUs. The evaluation is done through simulations. OMNET++ [4] and the MiXiM framework are used for detailed packet-level simulation. The simulation is done for both small and large scale scenarios. For the large scale simulation, we use SUMO [5] to generate mobility traces of vehicle nodes. Different criteria are defined so that we can compare CRL distribution methods. According to the simulation results, vehicles in C2C Epidemic, MPB and ICE receive all the required CRL pieces in less time in comparison to RSU-only, because vehicles use both I2V and V2V communications. MPB shows a better performance than C2C Epidemic, but the number of duplicate received pieces increases substantially. ICE tries to alleviate this by incorporating semi-incremental CRL exchange. Furthermore, the number of broadcasts by RSUs in the ICE method shows reduction.

  • 20. Andersson, G.
    et al.
    Esfahani, P. M.
    Vrakopoulou, M.
    Margellos, K.
    Lygeros, J.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Cyber-security of SCADA systems2012In: 2012 IEEE PES Innovative Smart Grid Technologies, ISGT 2012, IEEE , 2012, 6175543- p.Conference paper (Refereed)
    Abstract [en]

    After a general introduction of the VIKING EU FP7 project two specific cyber-attack mechanisms, which have been analyzed in the VIKING project, will be discussed in more detail. Firstly an attack and its consequences on the Automatic Generation Control (AGC) in a power system are investigated, and secondly the cyber security of State Estimators in SCADA systems is scrutinized.

  • 21.
    Anisseh, Sara
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Internet Topology Characterizationon on AS Level2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study investigates the Internet topology characterization on AS level driven from Border Gateway Protocol (BGP) tables which are collected from Réseaux IP Européens (RIPE) datasets during the seven year period, from 2003.07.30 to 2010.07.30.

    The investigation shows that despite of the growth of the Internet with lack of centralized control, some properties of the Internet follow certain rules and some properties remain the same during years. It demonstrates that the Internet, on AS level, exists in the form of clusters of ASs and the connected ASs with higher connectivity become even more connected during time. The spectral analysis of adjacency and normalized Laplacian matrix shows that the eigenvalues of both matrixes follow power-laws with high correlation coefficient with no considerable change in exponent values during years.

  • 22.
    Anna, Ljungström
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Positioning of IP telephones2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report considers the problems with positioning of emergency telephone calls. Emergency calls to the emergency number “112” answered by the emergency service in Sweden cannot always be positioned. That is, it cannot be decided where the call is coming from. The problem with positing of emergency calls is mainly caused by emergency calls coming from Internet Protocol (IP) telephones. Since the use of IP telephones are increasing the number of emergency calls coming from IP telephones will increase. For the emergency service to provide a secure and reliable service to the public it is crucial that all emergency calls can be positioned correctly.

    The report explains how emergency calls are connected towards the emergency service in Sweden, from the different types of telephones that support emergency calls. For the traditional fixed land line all emergency calls can be positioned, when using a mobile telephone 90% of the emergency calls can be positioned. The IP telephones can be divided into two categories, fixed and nomadic. When a fixed IP telephone is used the emergency call can always be positioned correctly, the problem occurs when a nomadic IP telephone is used. Interviews have been held with the four largest IP telephone operators to get their views of the problem and whether they have an opinion on how to solve the problem. Practical tests have been performed to show the problem and when it occurs. To solve the problem with positioning of emergency calls coming from IP telephones an international standard must be set. New features needs to be implemented in the networks so that the calls coming from IP telephones can be positioned and utilize positioning features such as GPS. A lot of work still remains before an international standard can be set.

  • 23.
    Arino Perez, Victor
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Efficient Key Generation and Distributionon Wireless Sensor Networks2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wireless Sensor Networks have become popular during the last years. The introduction ofIPv6 which broadened the address space available, IEEE802.15.4 and adaption layers such as6loWPAN have allowed the intercommunication of small devices. These networks are usefulin many scenarios such as civil monitoring, mining, battle eld operations, as well as consumerproducts. Hence, practical security solutions for the intercommunication must be provided,ensuring privacy, authenticity, integrity and data freshness. In most cases, WSN nodes arenot tamper-proof and have very limited available resources and capabilities which makes PKIcurrently not attractive for this environment. At the same time, key pre-distribution providetoo low security for most applications. Therefore, the communication bootstrapping or thekey generation and distribution problem is an important concern to be addressed with theadditional di culty of the constrained capabilities of WSN nodes. In this thesis, a solution tothis problem is described. It makes use of ECDH and the curve K-163 for key exchange, AESCCM-128 for symmetric encryption to lower the processing overhead and a partial challengesolving chain as well as a TAS to provide strong authentication. Several hash functions havebeen analysed as well as several random number generating approaches. At the same time, inorder to t the key generation and distribution algorithms together with the regular sensoroperation, code optimizations were carried out on the cryptographic library Relic-Toolkit,reducing the memory footprint in 4KB; code reductions on Contiki OS allowed it to run usingonly 18KB of ash; and the peripheral drivers developed for the CC430 reduced as well thecomputation time. The solution allows to generate and distribute the keys in situ and isproved to be resilient to most adversaries while taking into account scalability, portability,energy consumption and making it suitable for consumer applications.

  • 24.
    Aurensanz, Alberto
    KTH, School of Electrical Engineering (EES), Communication Networks.
    A reliable transmission protocol fordistributed extraction of visual featuresusing BRISK and SURF2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Performing visual feature extraction in a network of processing

    nodes is challenging and requires the development of algorithms

    that perform the allocation and delegation of computational tasks,

    of protocols responsible for the correct transmission of data, etc.

    This report starts working from the implementation of a testbed

    for the evaluation of distributed processing of visual features and

    extends its functionality. The testbed is implemented in C++ us-

    ing credit-card sized computers and ZigBee USB units. Communi-

    cation between nodes is carried out through ASN.1 defined types.

    The first part of the thesis work consists of enabling the system

    to work with two different feature extraction schemes. The first

    one is the already implemented SURF algorithm from OpenCV

    and the second one is the original implementation of BRISK. The

    user must be capable of choosing indifferently between them. The

    second part of the work consists of modifying the transmission

    aspects of the system including the necessary classes to provide

    reliability via the design of a retransmission protocol. The reliable

    transmission protocol used is a version of a Stop-and-Wait scheme.

    The system’s performance is evaluated detailing the time needed

    to complete each step of the feature extraction process, presenting

    a comparison between the SURF and BRISK detection and ex-

    traction times, and computing the frame loss rate and achievable

    throughput once the retransmission protocol is implemented.

  • 25. Babaheidarian, P.
    et al.
    Salimi, Somayeh
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Papadimitratos, Panos
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Security in the Gaussian interference channel: Weak and moderately weak interference regimes2016In: 2016 IEEE International Symposium on Information Theory - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2016, 2434-2438 p., 7541736Conference paper (Refereed)
    Abstract [en]

    We consider a secure communication scenario through the two-user Gaussian interference channel: each transmitter (user) has a confidential message to send reliably to its intended receiver while keeping it secret from the other receiver. Prior work investigated the performance of two different approaches for this scenario; i.i.d. Gaussian random codes and real alignment of structured codes. While the latter achieves the optimal sum secure degrees of freedom (s.d.o.f.), its extension to finite SNR regimes is challenging. In this paper, we propose a new achievability scheme for the weak and the moderately weak interference regimes, in which the reliability as well as the confidentiality of the transmitted messages are maintained at any finite SNR value. Our scheme uses lattice structure, structured jamming codewords, and lattice alignment in the encoding and the asymmetric compute-and-forward strategy in the decoding. We show that our lower bound on the sum secure rates scales linearly with log(SNR) and hence, it outperforms i.i.d. Gaussian random codes. Furthermore, we show that our achievable result is asymptotically optimal. Finally, we provide a discussion on an extension of our scheme to K > 2 users.

  • 26. Babaheidarian, Parisa
    et al.
    Salimi, Somayeh
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Papadimitratos, Panos
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Finite-SNR Regime Analysis of The Gaussian Wiretap Multiple-Access Channel2015In: 2015 53rd Annual Allerton Conference on Communication, Control, and Computing, Allerton 2015, 2015, 307-314 p., 7447020Conference paper (Refereed)
    Abstract [en]

    In this work, we consider a K-user Gaussian wiretap multiple-access channel (GW-MAC) in which each transmitter has an independent confidential message for the receiver. There is also an external eavesdropper who intercepts the communications. The goal is to transmit the messages reliably while keeping them confidential from the eavesdropper. To accomplish this goal, two different approaches have been proposed in prior works, namely, i.i.d. Gaussian random coding and real alignment. However, the former approach fails at moderate and high SNR regimes as its achievable result does not grow with SNR. On the other hand, while the latter approach gives a promising result at the infinite SNR regime, its extension to the finite-SNR regime is a challenging task. To fill the gap between the performance of the existing approaches, in this work, we establish a new scheme in which, at the receiver's side, it utilizes an extension of the compute-and-forward decoding strategy and at the transmitters' side it exploits lattice alignment, cooperative jamming, and i.i.d. random codes. For the proposed scheme, we derive a new achievable bound on sum secure rate which scales with log(SNR) and hence it outperforms the i.i.d. Gaussian codes in moderate and high SNR regimes. We evaluate the performance of our scheme, both theoretically and numerically. Furthermore, we show that our sum secure rate achieves the optimal sum secure degrees of freedom in the infinite-SNR regime.

  • 27.
    Bai, Xueyao
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Distributed Visual Processing Based On interest Point Clustering2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this master thesis project, we study the problem in Visual Sensor Networks

    in which only limited bandwidth is provided. The task is to search for ways to

    decrease the transmitting data on the camera side, and distribute the data to dif-

    ferent nodes.

    To do so, we extract the interest points on the camera side by using BRISK in-

    terest point detector, and we distribute the detected interest points into di erent

    number of processing node by implementing proposed clustering methods, namely,

    Number Based Clustering, K-Means Clustering and DBSCAN Clustering.

    Our results show it is useful to extract interest points on the camera side, which

    can reduce almost three quarters of data in the network. A step further, by imple-

    menting the clustering algorithms, we obtained the gain in overhead ratio, interest

    point imbalance and pixel processing load imbalance, respectively. Specically,

    the results show that none of the proposed clustering methods is better than oth-

    ers. Number Based Clustering can balance the processing load between di erent

    processing nodes perfectly, but performs bad in saving the bandwidth resources.

    K-Means Clustering performs middle in the evaluation while DBSCAN is great in

    saving the bandwidth resources but leads to a bad processing balance performance

    among the processing nodes.

  • 28. Baliosian, J.
    et al.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Decentralized configuration of neighboring cells for radio access networks2007In: 2007 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks, WOWMOM, IEEE , 2007, 4351740- p.Conference paper (Refereed)
    Abstract [en]

    In order to execute a handover processes in a Radio Access Network, each cell has a configured list of neighbors to which such handovers are made. Rapid re-configuration of the neigh-borhood list in response to network failures and other events is currently not possible. To address this problem, this paper suggests an autonomic approach for dynamically configuring neighboring cell lists and introduces a decentralized, three-layered framework. As a key element of this framework, a novel probabilistic protocol that detects and continuously tracks the coverage overlaps among cells is presented and evaluated. The protocol, called DOC, maintains a distributed graph of over-lapping cells. Due to using Bloom fillers and aggregation techniques, it exhibits a low traffic and computational overhead. A first series of simulation studies suggests that DOC is scalable with respect to network size and the number of terminals.

  • 29. Baliosian, Javier
    et al.
    Matusikova, Katarina
    Quinn, Karl
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Policy-based self-healing for radio access networks2008In: 2008 IEEE NETWORK OPERATIONS AND MANAGEMENT SYMPOSIUM, IEEE , 2008, 1007-1010 p.Conference paper (Refereed)
    Abstract [en]

    Various centralized, distributed or cooperative management systems have been proposed to address the demands of wireless telecommunication networks. However, considering the size, complexity and heterogeneity that those networks will have in the future, current solutions either do not scale properly, or have no support for automation, or lack of the flexibility and simple control that operators will need for managing future networks in a cost-effective way. To address this problem, we designed Omega, a distributed and policy-based network management system that uses rich knowledge-modeling techniques to develop self-configuration capabilities. Omega also implements a novel conflict-resolution method that uses high-level goals and machine learning techniques to optimize its policy-based decisions. Using simulations, in this paper we show how Omega reduces the impact of a node crash on the overall availability of a radio access network by optimizing the lists of neighboring cells of the nodes in the vicinity.

  • 30.
    Baliosian, Javier
    et al.
    Ericsson Ireland Research Centre, Athlone, Ireland.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Method of Discovering Overlapping Cells2007Patent (Other (popular science, discussion, etc.))
  • 31. Barcelo-Ordinas, Jose M.
    et al.
    Casetti, Claudio
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Sargento, Susana
    Information Mobility: a New Paradigm for Wireless Content Dissemination2009In: EUWIT: 2009 EUROPEAN WIRELESS TECHNOLOGY CONFERENCE, 2009, 100-103 p.Conference paper (Refereed)
    Abstract [en]

    Content distribution networks are nowadays becoming a mature technology. Nevertheless, content delivery research in ad hoc networks has dealt with overlay applications, information querying and data broadcasting techniques. The aim of this paper is to explore and discuss content delivery in wireless ad hoc networks and to state challenges and reference models for this kind of networks. The concept of Information Mobility is introduced to point out that the contents are being stored in mobile nodes and that the contents move and replicate before being accessed. The network considered is a wireless ad hoc network with sparse connectivity and limited infrastructure support.

  • 32. Baroffio, L.
    et al.
    Canclini, A.
    Cesana, M.
    Redondi, A.
    Tagliasacchi, M.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Eriksson, Emil
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Fodor, Viktoria
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Ascenso, J.
    Monteiro, P.
    Demo: Enabling image analysis tasks in visual sensor networks2014In: Proceedings of the 8th ACM/IEEE International Conference on Distributed Smart Cameras, ICDSC 2014, Association for Computing Machinery (ACM), 2014, a46- p.Conference paper (Refereed)
    Abstract [en]

    This demo showcases some of the results obtained by the GreenEyes project, whose main objective is to enable visual analysis on resource-constrained multimedia sensor networks. The demo features a multi-hop visual sensor network operated by BeagleBones Linux computers with IEEE 802.15.4 communication capabilities, and capable of recognizing and tracking objects according to two different visual paradigms. In the traditional compress-then-analyze (CTA) paradigm, JPEG compressed images are transmitted through the network from a camera node to a central controller, where the analysis takes place. In the alternative analyze-then-compress (ATC) paradigm, the camera node extracts and compresses local binary visual features from the acquired images (either locally or in a distributed fashion) and transmits them to the central controller, where they are used to perform object recognition/tracking. We show that, in a bandwidth constrained scenario, the latter paradigm allows to reach better results in terms of application frame rates, still ensuring excellent analysis performance.

  • 33. Baroffio, L.
    et al.
    Cesana, M.
    Redondi, A.
    Tagliasacchi, M.
    Ascenso, J.
    Monteiro, P.
    Eriksson, Emil
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Dan, G.
    Fodor, Viktoria
    KTH, School of Electrical Engineering (EES), Communication Networks.
    GreenEyes: Networked energy-aware visual analysis2015In: 2015 IEEE International Conference on Multimedia and Expo Workshops, ICMEW 2015, IEEE conference proceedings, 2015Conference paper (Refereed)
    Abstract [en]

    The GreenEyes project aims at developing a comprehensive set of new methodologies, practical algorithms and protocols, to empower wireless sensor networks with vision capabilities. The key tenet of this research is that most visual analysis tasks can be carried out based on a succinct representation of the image, which entails both global and local features, while it disregards the underlying pixel-level representation. Specifically, GreenEyes will pursue the following goals: i) energy-constrained extraction of visual features; ii) rate-efficiency modelling and coding of visual feature; iii) networking streams of visual features. This will have a significant impact on several scenarios including, e.g., smart cities and environmental monitoring.

  • 34.
    Barzegar, Hossein
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Multicast scheduling for streaming video in single frequency networks2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With development in wireless mobile communication and evolution to high capacity system like LTE, multimedia streaming over wireless channel becomes an interesting topic both in field of research and application. The bottleneck of this issue is limited available resources in the systems; therefore it is important how the system is allocating its resources to deliver different streams to the subscribers.

    Transmitting data content in a mobile cell can be either uni-cast or multicast transmission. In multicasting type, data content is delivered simultaneously to all users within a group who already subscribed for that special stream. In both transmissions, an algorithm called scheduler decided which multicast group or user should be scheduled and receives the data content. Moreover the scheduler is responsible to dynamically change the transmission rate according to use-end’s channel condition. In this Master’s thesis, we analyze multicast scheduling algorithms for delivering multilayer and single-layer streams to the user-end in LTE-MBSFN network. We use three scheduler algorithms, Max-Sum, Max-Prod, RRB-Max_Sum, to set up the simulation system. We evaluate the performance of algorithms on MBSFN and single cell multicast transmission, as well as the

    impact of using single-layer and multilayer streams. Comparing single cell-multicast transmission and MBSFN scenario, our simulation shows that the quality of received streams is not degraded when the cell traffic load is small on both network structures. On high cell load occasion transmitting the single layer stream in MBSFN, results in low quality of service. The streaming can be offline when the scheduler has access to the data as much as it wants (i.e. saved on the hard disk) or real-time when data contents are stored on size limited buffer. We show that sending a small data bust is not an efficient way of multicasting on MBSFN and wastes the resources. Therefore in this Master thesis, we propose a Multi-group- Max_Sum algorithm that aggregates the small packet together and forms a bigger packet to efficiently use the frequency resources. The system will approach its ideal performance (offline streaming) when using a Multi-group-Max_Sum scheduler. After specific length, the buffer size doesn’t have impact on the scheduler performance.

  • 35. Bauer, K.
    et al.
    Boreli, R.
    Carlsson, N.
    Chen, Z.
    Francillon, A.
    Freudiger, J.
    Friedman, A.
    Gambs, S.
    Haddadi, H.
    Hecker, A.
    Hui, P.
    Kaafar, M. -A
    Köpf, B.
    Mahanti, A.
    Önen, M.
    Papadimitratos, Panagiotis
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Ries, S.
    Salamatian, K.
    Schneider, F.
    Shikfa, A.
    Shue, C.
    Strufe, T.
    Uhlig, S.
    Uzun, E.
    Xie, G.
    Welcome message from the PADE chairs2013In: Welcome message from the PADE chairs  (Editorial), IEEE Computer Society, 2013, lxi-lxii p.Conference paper (Other academic)
  • 36. Boccardi, Federico
    et al.
    Shokri-Ghadikolaei, Hossein
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Fodor, Gabor
    KTH, School of Electrical Engineering (EES), Automatic Control. Ericsson Research, United States.
    Erkip, Elza
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Kountouris, Marios
    Popovski, Petar
    Zorzi, Michele
    Spectrum Pooling in MmWave Networks: Opportunities, Challenges, and Enablers2016In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 54, no 11, 33-39 p.Article in journal (Refereed)
    Abstract [en]

    Motivated by the specific characteristics of mmWave technologies, we discuss the possibility of an authorization regime that allows spectrum sharing between multiple operators, also referred to as spectrum pooling. In particular, considering user rate as the performance measure, we assess the benefit of coordination among networks of different operators, study the impact of beamforming at both base stations and user terminals, and analyze the pooling performance at different frequency carriers. We also discuss the enabling spectrum mechanisms, architectures, and protocols required to make spectrum pooling work in real networks. Our initial results show that, from a technical perspective, spectrum pooling at mmWave has the potential to use the resources more efficiently than traditional exclusive spectrum allocation to a single operator. However, further studies are needed in order to reach a thorough understanding of this matter, and we hope that this article will help stimulate further research in this area.

  • 37.
    Bohli, J. M.
    et al.
    NEC Research.
    Papadimitratos, Panos
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Verardi, D.
    EPFL.
    Westhoff, D.
    Resilient Data Aggregation for Unattended WSNs2011In: 6th International IEEE Workshop on PracticalᅵIssues in Building Sensor Network Applicationsᅵ(IEEE SenseApp 2011), in conjunction with the 36th IEEE LCN, IEEE , 2011, 994-1002 p.Conference paper (Refereed)
    Abstract [en]

    Unattended wireless sensor networks (WSNs) collect and store sensed data in the absence of a base station (sink). WSN data aggregation is a widely accepted approach to improve storage and communication efficiency. But the vulnerability of low-cost WSN nodes to compromise makes the use of secure protocols mandatory. As most secure data aggregation algorithms use the base station as a trust anchor, unattended WSNs need new solutions for secure data aggregation. We address exactly this problem, proposing a new resilient data aggregation scheme that protects data integrity and remains robust to a wide range of attacks, integrating Quality-of-Information (QoI) as a defense mechanism. We argue that a QoI metric accompanying every aggregation result is necessary for the WSN user, to assess the quality of obtained data and detect errors or attacks. Even with a significant fraction of the WSN nodes controlled by the attacker, our scheme identifies and mitigates the effect of the attacks. This is supported by our analysis, with simulations of realistic strong attacks. The practicality of our scheme is supported by our proof of concept implementation.

  • 38.
    Briat, Corentin
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Robust stability analysis in the *-norm and Lyapunov-Razumikhin functions for the stability analysis of time-delay systems2011Conference paper (Other academic)
    Abstract [en]

    Lyapunov-Krasovskii functionals have been shown to have connections with input-output techniques considering delay operators mapping L-2 to L-2. It is shown here that Lyapunov-Razumikhin functions can also be connected to the input-output framework by considering operators on L-infinity and the corresponding Small-Gain Theorem. Several important results from the Lyapunov-Razumikhin Theorem are retrieved and extended.

  • 39.
    Briat, Corentin
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Robust stability analysis of uncertain Linear Positive Systems via Integral Linear Constraints: L-1- and L-infinity-gain characterizations2011Conference paper (Refereed)
    Abstract [en]

    Copositive Lyapunov functions are used along with dissipativity theory for stability analysis of uncertain linear positive systems. At the difference of standard results, linear supply-rates are employed for robustness and performance analysis and lead to L-1- and L-infinity-gain characterizations. This naturally guides to the definition of Integral Linear Constraints (ILCs) for the characterization of input-output nonnegative uncertainties. It turns out that these integral linear constraints can be linked to the Laplace domain, in order to be tuned adequately, by exploiting the L-1-norm and input/output signals properties. This dual viewpoint allows to prove that the static-gain of the uncertainties, only, is critical for stability. This fact provides a new explanation for the surprising stability properties of linear positive time-delay systems. The obtained stability and performance analysis conditions are expressed in terms of (robust) linear programming problems that are transformed into finite dimensional ones using the Handelman's Theorem. Several examples are provided for illustration.

  • 40.
    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, 1484-1491 p.Conference 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.

  • 41.
    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, 3122-3129 p.Conference 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.

  • 42.
    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, 2050-2058 p.Conference 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.

  • 43.
    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.
    Impact of Queueing Delay Estimation Error on Equilibrium and Its Stability2011In: NETWORKING 2011, PT II, 2011, 356-367 p.Conference paper (Refereed)
    Abstract [en]

    Delay-based transmission control protocols need to separate round-trip time (RTT) measurements into their constituting parts: the propagation and the queueing delays. We consider two means for this; the first is to take the propagation delay as the minimum observed RTT value, and the second is to measure the queueing delay at the routers and feed it back to the sources. We choose FAST-TCP as a representative delay-based transmission control protocol for analysis and study the impact of delay knowledge errors on its performance. We have shown that while the first method destroys fairness and the uniqueness of the equilibrium, the stability of the protocol can easily be obtained through tuning the protocol terms appropriately. Even though the second technique is shown to preserve fairness and uniqueness of the equilibrium point, we have presented that unavoidable oscillations can occur around the equilibrium point.

  • 44. Brunner, M
    et al.
    Galis, A
    Cheng, L
    Colas, J A
    Ahlgren, B
    Gunnar, A
    Abrahamsson, H
    Szabo, R
    Csaba, S
    Nielsen, J
    Schuetz, S
    Gonzalez Prieto, Alberto
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Molnar, G
    Towards Ambient Networks Management2005In: MOBILITY AWARE TECHNOLOGIES AND APPLICATIONS, PROCEEDINGS, 2005, Vol. 3744, 215-229 p.Conference paper (Refereed)
    Abstract [en]

    Ambient Networks (AN) are under development and they are based on novel networking concepts and systems that will enable a wide range of user and business communication scenarios beyond today's fixed, 3(rd) generation mobile and IP standards. Central to this project is the concept of Ambient Control Space (ACS) and the Domain Manager control function, which manages the underlying data transfer capabilities and presents a set of interfaces towards the supported services and applications. Network Management Systems of Ambient Networks must work in an environment where heterogeneous networks compose and cooperate, on demand and transparently, without the need for manual (pre or re)-configuration or offline negotiations between network operators. To achieve these goals, ambient network management systems must become dynamic, distributed, self-managing and responsive to the network and its ambience. This paper describes the different management research challenges and four complementary solution approaches (i.e. Pattern-based Management, Peer-to-Peer Management, (Un)PnP Management, Traffic Engineering Management Application Approaches) that enable efficient management of ambient networks, and the relationships between them, and presents the main results achieved so far.

  • 45.
    Brykt, Andreas
    KTH, School of Electrical Engineering (EES), Communication Networks.
    A testbed for distributed detection ofkeypoints and extraction of descriptors forthe Speeded-Up-Robust-Features (SURF)algorithm2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Detecting keypoints and computing descriptors needed in an imagerecognition algorithm are tasks that require substantial processing powerif they are to be executed in a short time span. If a network of sensornodes is used to capture the images to be processed, then the sensor nodescould be used to perform the actual processing. The system would dis-tribute the computing tasks to the available nodes in the network, so thatthe computing load can be divided among the nodes. By this, the com-puting time could possibly still be kept low, despite the large differencein available computing power between a rack-server and a sensor node.This report describes the implementation of a testbed for the evaluationof distributed processing of visual features. The testbed is implementedin C++ using creditcard sized computers and Zigbee USB units. Com-munication between nodes utilizes ASN.1 defined types. The detectionand extraction stage use an implementation of the SURF algorithm fromOpenCV. Results are sent for matching to a server using a TCP-socketin the sink node. The system is evaluated in terms of data transmissionprotocol efficiency, and time spent on transmitting data vs. computation.

  • 46.
    Burden, Tony
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Cohen, Ian
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Dodd, D.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Online tutoring2006In: SEFI 2006 - 34th Annual Conference: Engineering Education and Active Students, Uppsala universitet, 2006Conference paper (Refereed)
    Abstract [en]

    Tutoring has been a central part of the educational system at the long established universities of Cambridge and Oxford in the UK. Previously, at most two students could be tutored in the mathematical sciences, one on each side of the supervisor. Today in the age of computing and Internet, any number of students, in principal, could be supervised at a distance, as each student will be sitting in front of his or her own computer. This paper describes an attempt to carry out tutoring in the subject area of mechanics in small groups and at a distance, i.e. the tutors and the students communicate via an Internet based e-meeting system rather being present in the same physical room. This is used at a KTH (Sweden) mechanics distance course supported with tutoring from AUT (New Zealand) and the reverse tutoring of students at a regular mechanics course at AUT tutored from KTH.

  • 47. Carlsson, N.
    et al.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Mahanti, A.
    Arlitt, M.
    A longitudinal characterization of local and global BitTorrent workload dynamics2012In: 13th International Conference on Passive and Active Measurement (PAM), 2012, Springer Berlin/Heidelberg, 2012, Vol. 7192 LNCS, 252-262 p.Conference paper (Refereed)
    Abstract [en]

    Workload characterization is important for understanding how systems and services are used in practice and to help identify design improvements. To better understand the longitudinal workload dynamics of chunk-based content delivery systems, this paper analyzes the BitTorrent usage as observed from two different vantage points. Using two simultaneously collected 48-week long traces, we analyze the differences in download characteristics and popularity dynamics observed locally at a university campus versus at a global scale. We find that campus users typically download larger files and are early adopters of new content, in the sense that they typically download files well before the time at which the global popularity of the files peak. The noticeable exception is music files, which the campus users are late to download. We also find that there typically is high churn in the set of files that are popular each week, both locally and globally, and that the most popular files peak significantly later than their release date. These findings provide insights that may improve the efficiency of content sharing locally, and thus increase the scalability of the global system.

  • 48.
    Carlsson, Niklas
    et al.
    Linkoping University.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Eager, Derek
    University of Saskatchewan .
    Mahanti, Anirban
    NICTA.
    Tradeoffs in cloud and peer-assisted content delivery systems2012In: 2012 IEEE 12th International Conference on Peer-to-Peer Computing, P2P 2012, IEEE , 2012, 249-260 p.Conference paper (Refereed)
    Abstract [en]

    With the proliferation of cloud services, cloud-based systems can become a cost-effective means of on-demand content delivery. In order to make best use of the available cloud bandwidth and storage resources, content distributors need to have a good understanding of the tradeoffs between various system design choices. In this work we consider a peer-assisted content delivery system that aims to provide guaranteed average download rate to its customers. We show that bandwidth demand peaks for contents with moderate popularity, and identify these contents as candidates for cloud-based service. We then consider dynamic content bundling (inflation) and cross-swarm seeding, which were recently proposed to improve download performance, and evaluate their impact on the optimal choice of cloud service use. We find that much of the benefits from peer seeding can be achieved with careful torrent inflation, and that hybrid policies that combine bundling and peer seeding often reduce the delivery costs by 20% relative to only using seeding. Furthermore, all these peer-assisted policies reduce the number of files that would need to be pushed to the cloud. Finally, we show that careful system design is needed if locality is an important criterion when choosing cloud-based service provisioning.

  • 49. Carra, D.
    et al.
    Strufe, T.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Karnstedt, M.
    Topic 7: Peer-to-peer computing (Introduction)2013In: Lecture Notes in Computer Science, 2013, 353- p.Conference paper (Refereed)
    Abstract [en]

    In Peer-to-peer (P2P) systems computers form an overlay network and share their resources (storage, CPU, bandwidth) to implement a service on top of the Internet. P2P computing has a great potential for creating systems that are selforganizing, efficient, and scalable, but it also faces many challenges: dynamic peer arrivals and departures, which may be correlated (e.g., flash crowd effects, or software failures), high variability of resources, and resource heterogeneity. This topic provides a forum for researchers to present new contributions to P2P systems, technologies, middleware, and applications that address key research issues and challenges.

  • 50. Casetti, C.
    et al.
    Cesana, M.
    Filippini, I.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Marsh, I.
    Context-aware information dissemination in vehicular networks2011In: EURO-NGI Conf. Next Gener. Internet Networks, NGI - Proc., 2011Conference paper (Refereed)
    Abstract [en]

    With the proliferation of mobile devices and vehicular onboard-units mobility is becoming a key factor in determining the performance of networked systems: both the performance of the infrastructure (e.g., the amount of control traffic) and the performance perceived by the end-users (e.g., access latency, throughput) are influenced by mobility. Mobility, as a manifestation of the physical world, transforms content distribution systems into cyber-physical systems. The efficient design and operation of cyber-physical systems, in general, requires an understanding of the characteristics and of the interactions between the components of the system.

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