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

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

  • 252.
    Chazalet, Boris
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Opportunistic Content Delivery utilizing Optimized Context Dissemination via the Service Interface in Ambient Networks2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One of the novel and important features of Ambient Networks is the use of context information. Context in Ambient Networks concerns any information that describes the current situation of entities connected to the network (e.g. location, available connectivity and devices, etc.). Such context information can be used by applications, services, or network resources enabling them to automatically adapt their behavior without requiring user intervention. Thus, context in Ambient Networks provides a better user experience due to the auto-configuration, as well as auto-arrangement of service delivery and transport.

    This thesis presents an optimized version and implementation of the Distributed Context eXchange Protocol. This protocol is part of the context-aware architecture for Ambient Networks. The design and architecture of the Distributed Context eXchange Protocol (DCXP), utilizes a P2P overlay on top of UDP. This design and architecture have been revised to enable real-time context dissemination, while simultaneously removing bottlenecks. An analysis of this revised design including measurements in real-world scenarios, shows that DXCP offers a practical approach to context-sensing and dissemination, allowing rapid context changes and spontaneous use of new context sources as these become (un)available in dynamic rearrangements of network connectivity, facilitating the use of Ambient Network technologies. Finally, the thesis presents and demonstrates a novel use and the advantages of Optimized Context Dissemination as the Ambient Networks Service Interface (ASI) for Opportunistic Content Delivery. This is achieved by adding an (subset) API to the ASI which enables a Content Delivery Proxy to interface with DCXP and leverage context information to enable opportunistic content delivery across Ambient Networks.

  • 253.
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Efficient resiliency mechanisms for next generation passive optical networks2013In: ICICS 2013 - Conference Guide of the 9th International Conference on Information, Communications and Signal Processing, IEEE Computer Society, 2013, p. 6782903-Conference paper (Refereed)
    Abstract [en]

    Future broadband access networks are expected to cover large service areas while fulfilling high bandwidth request on a per-user basis. The rapidly increasing traffic demand is also driven by the growing popularity of mobile data services, which is placing high-capacity requirement on the backhaul. Due to advances in wavelength division multiplexing (WDM) technology, WDM based architectures have been considered as promising candidates for next generation optical access, such as WDM passive optical network (PON), and hybrid WDM/time division multiplexing (TDM) PON. Meanwhile, resilience technique will play a more prominent role in emerging access networks due to their significantly increased capacity and coverage compared to the current deployments. Therefore, efficient resiliency mechanisms are highly required to enable uninterrupted network operation where a certain level of reliability performance can be guaranteed. In this work, we first evaluate reliability performance of each segment of next generation optical access networks and then identify the most important part for protection. A particular attention is paid to the reduction of failure impact.

  • 254.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Mahloo, Mozhgan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Reducing the Impact of Failures in Next Generation Optical Access Networks2012In: 2012 Asia Communications And Photonics Conference (ACP), 2012, p. AS1D.2-Conference paper (Refereed)
    Abstract [en]

    Reliability performance of next generation optical access (NGOA) networks offering high bandwidth and large service coverage is evaluated. A particular attention is paid to the reduction of the impact of failures in NGOA.

  • 255.
    Chen, Jiajia
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Urban, Patryk J.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Fast fault monitoring technique for reliable WDM PON: Achieving significant operational saving2013In: 2013 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference, OFC/NFOEC 2013, IEEE , 2013, p. 6532499-Conference paper (Refereed)
    Abstract [en]

    We propose a fast fault supervision technique compatible with an efficient resilience scheme for WDM PON. Several drop fibres can be monitored simultaneously so that a significant reduction of operational cost can be achieved.

  • 256.
    Chen, Lisan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Schiller Shi, Tingting
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Targeted News in an Intranet2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In SharePoint 2013, Microsoft added a social networking function in the personal sites (My Site) of a user. In this version, a personal news feed has been added which shows events regarding subjects the user follows, such as document changes, user updates, tagged posts, and site activities. The purpose of the thesis is to investigate whether or not it is possible to extend the news feed function by adding an independent component as part of My Site, to allow users to follow corporate news by choosing their categories of interests.

    A prototype of the component was implemented and it met most of the objectives stated in the thesis. It is added to the default page of the user’s My Site as a web part and it is able to retrieve and display news that matches the user’s subscription. Although the web part still needs improvements in both functionality and design, it still confirms that it is possible to extend the current My Site news feed with such a component.

    Since the students working on this thesis had no prior knowledge of SharePoint or .NET development, the project brought new challenges, as the students needed to learn how to work in a SharePoint environment and to learn to use Microsoft Visual Studio for .NET development.

  • 257.
    Chen, Ta-wei
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Optimization of Transport Security for Securing Peer-to-Peer Communication in Heterogeneous Networks2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis concerns the security of tomorrow’s peer-to-peer real-time communication in heterogeneous networks. Because of the additional delay caused by inband handshake and the poor compatibilities of some transport protocols, it was determined that existing security protocols such as transport layer security (TLS) and datagram transport layer security (DTLS) are not suitable in such a user scenario and a new security protocol should be designed. This new security protocol is called transport encapsulation security payload (TESP). TESP not only has the advantage of low initialization delay, but also fully supports transport protocols including TCP, UDP, stream control transmission protocol (SCTP), and datagram congestion control protocol (DCCP). Also a security analysis of TESP was carried out and no security flaws were found.

  • 258.
    Chen, Xu
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Performance Analysis of Wireless Multiplayer Games on Terraplay Systems2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis project was sponsored by Terraplay System AB. Terraplay System is a wireless online multiplayer game service provider in Europe. The purpose of this project was to provide a convenient and free latency test tool named Terraplay Test Toolkit (TTK) for game developers who utilize the Terraplay platform. Since wireless multiplayer games are latency sensitive, it’s necessary for game developers to estimate the real-time game latency before their development. TTK is based on Java Mobile Edition (J2me) technology, it can performs a real-time Round Trip Time (RTT) latency test. This project explored the application of the mobile development. Mobile development is a brand new field and becoming more and more popular. The design process and source code can be used as reference for mobile developers. Based on the Terraplay Test Toolkit, a series of experiments were conducted to test the ability of TTK. These experiments focused on end-to-end latency effects of wireless multiplayer games under different situations such as different packet size, different sending rates, high speed movement, and so on. Although TTK is not a professional test tool, it still reflects the latency variance under different conditions correctly. From these experiments, it was found that for the Terraplay enabled wireless multiplayer games, large average packet size (300 bytes) is NOT a factor with regard to the latency on the Terraplay System; the packet rate can affect the game latency. In a high speed-moving environment, game latency doesn’t obvious increase. Using HTTP can cause three times higher latency than simply using TCP. These conclusions are based on experimental results. These conclusions should guide wireless multiplayer game developers and game players.

  • 259.
    Chen, Zhaofei
    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.
    Demo of a collaborative music sharing system2012In: MobiOpp'12 - Proceedings of the 3rd ACM International Workshop on Mobile Opportunistic Networks, New york: ACM , 2012, p. 77-78Conference paper (Refereed)
    Abstract [en]

    We demonstrate a wireless real-time music-sharing application that lets users play music directly from their mobiles through a jukebox. We have designed and implemented the application by using a previously developed content-centric opportunistic networking middleware. The jukebox plays the music file that is first in its playlist by streaming it in real-time from the publishing user device. All users can observe the collaboratively formed playlist on their mobiles in real-time. The application shows the usefulness of our middleware and demonstrates a new form of situated applications. The application handles churn and garbage collection after departed users.

  • 260.
    Chen, Zhaofei
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Yavuz, Emre Altug
    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.
    What a juke! A collaborative music sharing system2012In: 2012 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks, WoWMoM 2012 - Digital Proceedings, IEEE , 2012, p. 6263751-Conference paper (Refereed)
    Abstract [en]

    The fast spreading of smart mobile devices has changed the way people create and share multimedia contents. A recently proposed idea is to distribute contents opportunistically when devices are within each other's communication range. In this work we have seized this idea and designed and implemented a real-time music-sharing application that allows people to share a sound system for collective listening. The system utilizes a content-centric opportunistic networking middleware. The application provides an interface for users to play audio files stored in their own mobile devices through a shared jukebox that is within direct communication range. The jukebox plays the audio file that is first in queue in its playlist by streaming it from the publishing user device. All devices synchronize with the jukebox so that the users can observe the contents of the playlist on their displays in real-time. This paper presents the idea and motivation for such a system as well as its design and evaluation.

  • 261.
    Cheng, Yuxin
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Passive Optical Top-of-Rack Interconnect for Data Center Networks2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Optical networks offering ultra-high capacity and low energy consumption per bit are considered as a good option to handle the rapidly growing traffic volume inside data center (DCs). However, most of the optical interconnect architectures proposed for DCs so far are mainly focused on the aggregation/core tiers of the data center networks (DCNs), while relying on the conventional top-of-rack (ToR) electronic packet switches (EPS) in the access tier. A large number of ToR switches in the current DCNs brings serious scalability limitations due to high cost and power consumption. Thus, it is important to investigate and evaluate new optical interconnects tailored for the access tier of the DCNs.

    We propose and evaluate a passive optical ToR interconnect (POTORI) architecture for the access tier. The data plane of the POTORI consists mainly of passive components to interconnect the servers within the rack as well as the interfaces toward the aggregation/core tiers. Using the passive components makes it possible to significantly reduce power consumption while achieving high reliability in a cost-efficient way.

    Meanwhile, our proposed POTORI’s control plane is based on a centralized rack controller, which is responsible for coordinating the communications among the servers in the rack. It can be reconfigured by software-defined networking (SDN) operation. A cycle-based medium access control (MAC) protocol and a dynamic bandwidth allocation (DBA) algorithm are designed for the POTORI to efficiently manage the exchange of control messages and the data transmission inside the rack.

    Simulation results show that under realistic DC traffic scenarios, the POTORI with the proposed DBA algorithm is able to achieve an average packet delay below 10 μs with the use of fast tunable optical transceivers. Moreover, we further quantify the impact of different network configuration parameters on the average packet delay. 

  • 262.
    Cheng, Yuxin
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Fiorani, Matteo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Reliable and Cost Efficient Passive Optical Interconnects for Data Centers2015In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, no 11, p. 1913-1916Article in journal (Refereed)
    Abstract [en]

    To address the sustainability, scalability, and reliability problems that data centers are currently facing, we propose three passive optical interconnect (POI) architectures on top of the rack. The evaluation results show that all three architectures offer high reliability performance (connection availability for intra-rack interconnections higher than 99.999%) in a cost-efficient way.

  • 263.
    Cheng, Zhuo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Hybrid Power Control in Time Division Scheduling Wideband Code Division Multiplex Access2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With high date rates using Enhanced Uplink (EUL), a conventional signal to interference ratio (SIR) based power control algorithm may lead to a power rush due to self interference or incompatible SIR target [2]. Time division (TD) scheduling in Wideband Code Division Multiplex Access (WCDMA) is considered to be a key feature in achieving high user data rates. Unfortunately, power oscillation/peak is observed in time division multiplexing (TDM) at the transition between active and inactive transmission time intervals [1]. Therefore there is a need to revisit power control algorithms for different time division scheduling scenarios.

    The objective of power control in the context of this study is to minimize the required rise over thermal noise (RoT) for a given data rate, subject to the constraint that the physical layer control channel quality is sufficient (assuming that the dedicated physical control channel (DPCCH) SIR should not go below 3dB with a probability of at most 5%). Another goal is to minimize the local oscillation in power (power peaks) that may occur, for example due to transitions between active and inactive transmission time intervals.

    The considered hybrid power control schemes are: (1) non-parametric Generalized rake receiver SIR (GSIR) Inner Loop Power Control (ILPC) during active transmission time intervals + Received Signal Code Power (RSCP) ILPC during inactive transmission time intervals and (2) RSCP ILPC during active transmission time intervals + GSIR ILPC during inactive transmission time intervals. Both schemes are compared with pure GSIR and pure RSCP ILPC.

    Link level simulations with multiple users connected to a single cell show that:

    • The power peak problem is obviously observed in GSIR + GSIR transmit power control (TPC), but in general it performs well in all time division scenarios studied. GSIR outperforms other TPC methods in terms of RoT, especially in the TU channel model. This is because it is good in combating instantaneously changed fading and accurately estimates SIR. Among all TPC methods presented, GSIR + GSIR TPC is best in maintaining the quality of the DPCCH channel. No power rush is observed when using GSIR + GSIR TPC.
    • RSCP + RSCP eliminates the power peak problem and outperforms other TPC methods presented under the 3GPP Pedestrial A (pedA) 3km/h channel in terms of RoT. However, in general it is worse in maintaining the control channel’s quality than GSIR + GSIR TPC.
    • GSIR + RSCP ILPC eliminates the power peak problem and out-performs GSIR power control in the scenario of 2 and 4 TDM high data rate (HDR) UE and 2 TDM HDR UE coexistence with 4 Code DivisionMultiplex (CDM) LDR UE, in the pedA 3km/h channel, in terms of RoT. However, the control channel quality is not maintained as well during inactive transmission time intervals.
    • It is not recommended to use RSCP + GSIR TPC since it performs worst among these TPC methods for most of the cases in terms of RoT, even though it is the second best in maintaining the control channel quality. The power peak is visible when using RSCP + GSIR TPC.

    To maintain the control channel’s quality, a minimum SIR condition is always used on top of all proposed TPC methods. However, when there are several connected TDM HDR UEs in the cell, results indicates that it is challenging to meet the quality requirement on the control channels. So it may become necessary to limit the number of connected terminals in a cell in a time division scenario.

  • 264.
    Chengegowda, Venkatesh
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Analysis of Queues for Interactive Voice and Video Response Systems: Two Party Video Calls2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Video conversation on mobile devices is popularizing with the advent of 3G. The enhanced network capacity thus available enables transmission of video data over the internet. It has been forecasted by several VOIP service organizations that the present IVR systems will evolve into Voice and Video Response (IVVR) Systems. However, this evolution has many technical challenges on the way. Architectures to implement queuing systems for video data and standards for inter conversion of video data between the formats supported by calling parties are two of these challenges. This thesis is an analysis of queues and media transcoding for IVVRs.

    A major effort in this work involves constructing a prototype IVVR queuing system. The system is constructed by using an open source server named Asterisk and MySql database. Asterisk is a SIP based Public Exchange Server (PBX) and also a development environment for VOIP based IVRs. Functional scenarios for SIP session establishment and the corresponding session setup times for this queueing model are measured. The results indicate that the prototype serves as a sufficient model for a queue, although a significant delay is introduced for session establishment.  The work also includes analysis of integrating DiaStar™, is a SIP based media transcoding engine to this queue. However, this system is not complete to function with DiaStar for media translation. The study concludes with a mention of the areas for future work on this particular system and the general state of IVVR queuing systems in the industry.

  • 265.
    Chia, Yeow-Khiang
    et al.
    Institute for Infocomm Research, Singapore.
    Kittichokechai, Kittipong
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On secure source coding with side information at the encoder2013In: 2013 IEEE International Symposium on Information Theory Proceedings (ISIT), IEEE, 2013, p. 2204-2208Conference paper (Refereed)
    Abstract [en]

    We consider a secure source coding problem with side informations at the decoder and the eavesdropper. The encoder has a source that it wishes to describe with limited distortion through a rate-limited link to a legitimate decoder. The message sent is also observed by the eavesdropper. The encoder aims to minimize both the distortion incurred by the legitimate decoder; and the information leakage rate at the eavesdropper. When the encoder has access to the side information (S.I.) at the decoder, we characterize the rate-distortion-information leakage rate (R.D.I.) region under a Markov chain assumption and when S.I. at the encoder does not improve the rate-distortion region as compared to the case when S.I. is absent. We then extend our setting to consider the case where the encoder and decoder obtain coded S.I. through a rate-limited helper, and characterize the R.D.I. region for several special cases under logarithmic loss distortion (log-loss). Finally, we consider the case of list or entropy constraints at the decoder and show that the R.D.I. region coincides with R.D.I. region under log-loss.

  • 266. Chiaraviglio, L.
    et al.
    Lorincz, J.
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Towards sustainable and reliable networks with LIFETEL2015In: Proceedings - IEEE INFOCOM, IEEE conference proceedings, 2015, p. 39-40Conference paper (Refereed)
    Abstract [en]

    We present the LIFETEL project, whose aim is trying to increase the device lifetime in telecommunication networks by exploiting energy-efficient techniques. In particular, we show that the lifetime of a device might increase when it is put in sleep mode. However, the device lifetime might decrease when power state variations (from sleep mode to full power) occur very frequently. Thus, there is a trade-off between the duration of sleep mode and its frequency. Moreover, we report a lifetime analysis for cellular and backbone devices, showing that the electricity saving may be exceeded by the costs due to the fact that devices fail more frequently compared to the situation in which they are always powered on. Thus, we claim that energy-aware network algorithms should be redesigned in order not to impact and to increase (when possible) the lifetime of network devices.

  • 267.
    Chiesa, Marco
    et al.
    Roma Tre University, Italy.
    Cittadini, L.
    Di Battista, G.
    Vanbever, L.
    Vissicchio, S.
    Using routers to build logic circuits: How powerful is BGP?2013In: 2013 21st IEEE International Conference on Network Protocols (ICNP), IEEE Computer Society, 2013, article id 6733584Conference paper (Refereed)
    Abstract [en]

    Because of its practical relevance, the Border Gateway Protocol (BGP) has been the target of a huge research effort since more than a decade. In particular, many contributions aimed at characterizing the computational complexity of BGP-related problems. In this paper, we answer computational complexity questions by unveiling a fundamental mapping between BGP configurations and logic circuits. Namely, we describe simple networks containing routers with elementary BGP configurations that simulate logic gates, clocks, and flip-flops, and we show how to interconnect them to simulate arbitrary logic circuits. We then investigate the implications of such a mapping on the feasibility of solving BGP fundamental problems, and prove that, under realistic assumptions, BGP has the same computing power as a Turing Machine. We also investigate the impact of restrictions on the expressiveness of BGP policies and route propagation (e.g., route propagation rules in iBGP and Local Transit Policies in eBGP) and the impact of different message timing models. Finally, we show that the mapping is not limited to BGP and can be applied to generic routing protocols that use several metrics.

  • 268.
    Chiesa, Marco
    et al.
    Roma Tre University, Italy.
    Cittadini, L.
    Di Battista, G.
    Vissicchio, S.
    Local transit policies and the complexity of BGP Stability Testing2011In: INFOCOM, 2011 Proceedings IEEE, Institute of Electrical and Electronics Engineers (IEEE), 2011, p. 2957-2965, article id 5935136Conference paper (Refereed)
    Abstract [en]

    BGP, the core protocol of the Internet backbone, is renowned to be prone to oscillations. Despite prior work shed some light on BGP stability, many problems remain open. For example, determining how hard it is to check that a BGP network is safe, i.e., it is guaranteed to converge, has been an elusive research goal up to now. In this paper, we address several problems related to BGP stability, stating the computational complexity of testing if a given configuration is safe, is robust, or is safe under filtering. Further, we determine the computational complexity of checking popular sufficient conditions for stability. We adopt a model that captures Local Transit policies, i.e., policies that are functions only of the ingress and the egress points. The focus on Local Transit policies is motivated by the fact that they represent a configuration paradigm commonly used by network operators. We also address the same BGP stability problems in the widely adopted SPP model. Unfortunately, we find that the most interesting problems are computationally hard even if policies are restricted to be as expressive as Local Transit policies. Our findings suggest that the computational intractability of BGP stability be an intrinsic property of policy-based path vector routing protocols that allow policies to be specified in complete autonomy.

  • 269.
    Chiesa, Marco
    et al.
    Université catholique du Louvain, Belgium.
    Demmler, D.
    Canini, M.
    Schapira, M.
    Schneider, T.
    Towards securing internet eXchange points against curious onlooKers2016In: ANRW 2016 - Proceedings of the ACM, IRTF and ISOC Applied Networking Research Workshop, Association for Computing Machinery (ACM), 2016, p. 32-34Conference paper (Refereed)
    Abstract [en]

    The growing relevance of Internet eXchange Points (IXPs), where an increasing number of networks exchange routing information, poses fundamental questions regarding the privacy guarantees of confidential business information. To facilitate the exchange of routes among their members, IXPs provide Route Server (RS) services to dispatch the routes according to each member's export policies. Nowadays, to make use of RSes, these policies must be disclosed to the IXP. This state of affairs raises privacy concerns among network administrators and even deters some networks from subscribing to RS services. We design SIXPACK (which stands for "Securing Internet eXchange Points Against Curious onlooKers"), a RS service that leverages Secure Multi-Party Computation (SMPC) techniques to keep export policies confidential, while maintaining the same functionalities as today's RSes. We assess the effectiveness and scalability of our system by evaluating our prototype implementation and using traces of data from one of the largest IXPs in the world.

  • 270.
    Chiesa, Marco
    et al.
    Roma Tre University, Italy.
    Di Battista, G.
    Erlebach, T.
    Patrignani, M.
    Computational complexity of traffic hijacking under BGP and S-BGP2012In: Automata, Languages, and Programming: 39th International Colloquium, ICALP 2012, Warwick, UK, July 9-13, 2012, Proceedings, Part II, Springer, 2012, Vol. 7392, no PART 2, p. 476-487Conference paper (Refereed)
    Abstract [en]

    Harmful Internet hijacking incidents put in evidence how fragile the Border Gateway Protocol (BGP) is, which is used to exchange routing information between Autonomous Systems (ASes). As proved by recent research contributions, even S-BGP, the secure variant of BGP that is being deployed, is not fully able to blunt traffic attraction attacks. Given a traffic flow between two ASes, we study how difficult it is for a malicious AS to devise a strategy for hijacking or intercepting that flow. We show that this problem marks a sharp difference between BGP and S-BGP. Namely, while it is solvable, under reasonable assumptions, in polynomial time for the type of attacks that are usually performed in BGP, it is NP-hard for S-BGP. Our study has several by-products. E. g., we solve a problem left open in the literature, stating when performing a hijacking in S-BGP is equivalent to performing an interception.

  • 271.
    Chiesa, Marco
    et al.
    Université catholique du Louvain, Belgium.
    Di Battista, G.
    Erlebach, T.
    Patrignani, M.
    Computational complexity of traffic hijacking under BGP and S-BGP2015In: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 600, p. 143-154Article in journal (Refereed)
    Abstract [en]

    Harmful Internet hijacking incidents put in evidence how fragile interdomain routing is. In particular, the Border Gateway Protocol (BGP), which is used to exchange routing information between Internet entities, called Autonomous Systems (ASes), proved to be prone to attacks launched by a single malicious AS. Recent research contributions pointed out that even S-BGP, the secure variant of BGP that is being deployed, is not fully able to blunt traffic attraction attacks. Given a traffic flow between two ASes, we study how difficult it is for a malicious AS to devise a strategy for hijacking or intercepting that flow. The goal of the attack is to attract a traffic flow towards the malicious AS. While in the hijacking attack connectivity between the endpoints of a flow can be disrupted, in the interception attack connectivity must be maintained. We show that this problem marks a sharp difference between BGP and S-BGP. Namely, while it is solvable, under reasonable assumptions, in polynomial time for the type of attacks that are usually performed in BGP, it is NP-hard for S-BGP. Our study has several by-products. E.g., we solve a problem left open in the literature, stating when performing a hijacking in S-BGP is equivalent to performing an interception.

  • 272.
    Chiesa, Marco
    et al.
    Université catholique du Louvain, Belgium.
    DI Lallo, R.
    Lospoto, G.
    Mostafaei, H.
    Rimondini, M.
    DI Battista, G.
    PrIXP: Preserving the privacy of routing policies at Internet eXchange Points2017In: Proceedings of the IM 2017 - 2017 IFIP/IEEE International Symposium on Integrated Network and Service Management, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 435-441, article id 7987309Conference paper (Refereed)
    Abstract [en]

    Internet eXchange Points (IXPs) serve as landmarks where many network service providers meet to obtain reciprocal connectivity. Some of them, especially the largest, offer route servers as a convenient technology to simplify the setup of a high number of bi-lateral peerings. Due to their potential to support a quick and easy interconnection among the networks of multiple providers, IXPs are becoming increasingly popular and widespread, and route servers are exploited increasingly often. However, in an ever-growing level of market competition, service providers are pushed to develop concerns about many aspects that are strategic for their business, ranging from commercial agreements with other members of an IXP to the policies that are adopted in exchanging routing information with them. Although these aspects are notoriously sensitive for network service providers, current IXP architectures offer no guarantees to enforce the privacy of such business-critical information. We re-design a traditional route server and propose an approach to enforce the privacy of peering relationships and routing policies that it manages. Our proposed architecture ensures that nobody, not even a third party, can access such information unless it is the legitimate owner (i.e., the IXP member that set up the policy), yet allowing the route server to apply the requested policies and each IXP member to verify that such policies have been correctly deployed. We implemented the route server and tested our solutions in a simulated environment, tracking and analyzing the number of exchanged control plane messages.

  • 273.
    Chiesa, Marco
    et al.
    Université catholique du Louvain, Belgium.
    Dietzel, C.
    Antichi, G.
    Bruyére, M.
    Castro, I.
    Gusat, M.
    King, T.
    Moore, A. W.
    Nguyen, T. D.
    Owezarski, P.
    Uhlig, S.
    Canini, M.
    Inter-domain networking innovation on steroids: Empowering IXPs with SDN capabilities2016In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 54, no 10, p. 102-108, article id 7588277Article in journal (Refereed)
    Abstract [en]

    While innovation in inter-domain routing has remained stagnant for over a decade, Internet exchange points (IXPs) are consolidating their role as economically advantageous interconnection points for reducing path latencies and exchanging ever increasing amounts of traffic. As such, IXPs appear as a natural place to foster network innovation and assess the benefits of SDN, a recent technological trend that has already boosted innovation within data center networks. In this article, we give a comprehensive overview of use cases for SDN at IXPs, which leverage the superior vantage point of an IXP to introduce advanced features like load balancing and DDoS mitigation. We discuss the benefits of SDN solutions by analyzing real-world data from one of the largest IXPs. We also leverage insights into IXP operations to shape benefits not only for members but also for operators.

  • 274.
    Chiesa, Marco
    et al.
    Roma Tre University, Italy.
    Kindler, G.
    Schapira, M.
    Traffic engineering with Equal-Cost-Multipath: An algorithmic perspective2014In: INFOCOM, 2014 Proceedings IEEE, Institute of Electrical and Electronics Engineers (IEEE), 2014, p. 1590-1598, article id 6848095Conference paper (Refereed)
    Abstract [en]

    To efficiently exploit network resources operators do traffic engineering (TE), i.e., adapt the routing of traffic to the prevailing demands. TE in large IP networks typically relies on configuring static link weights and splitting traffic between the resulting shortest-paths via the Equal-Cost-MultiPath (ECMP) mechanism. Yet, despite its vast popularity, crucial operational aspects of TE via ECMP are still little-understood from an algorithmic viewpoint. We embark upon a systematic algorithmic study of TE with ECMP. We consider the standard model of TE with ECMP and prove that, in general, even approximating the optimal link-weight configuration for ECMP within any constant ratio is an intractable feat, settling a long-standing open question. We establish, in contrast, that ECMP can provably achieve optimal traffic flow for the important category of Clos datacenter networks. We last consider a well-documented shortcoming of ECMP: suboptimal routing of large ("elephant") flows. We present algorithms for scheduling "elephant" flows on top of ECMP (as in, e.g., Hedera [1]) with provable approximation guarantees. Our results complement and shed new light on past experimental and empirical studies of the performance of TE with ECMP.

  • 275.
    Chiesa, Marco
    et al.
    Université catholique du Louvain, Belgium.
    Kindler, G.
    Schapira, M.
    Traffic engineering with equal-cost-multipath: An algorithmic perspective2017In: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 25, no 2, p. 779-792, article id 7588075Article in journal (Refereed)
    Abstract [en]

    To efficiently exploit the network resources operators, do traffic engineering (TE), i.e., adapt the routing of traffic to the prevailing demands. TE in large IP networks typically relies on configuring static link weights and splitting traffic between the resulting shortest paths via the Equal-Cost-MultiPath (ECMP) mechanism. Yet, despite its vast popularity, crucial operational aspects of TE via ECMP are still little-understood from an algorithmic viewpoint. We embark upon a systematic algorithmic study of TE with ECMP. We consider the standard model of TE with ECMP and prove that, in general, even approximating the optimal link-weight configuration for ECMP within any constant ratio is an intractable feat, settling a long-standing open question. We establish, in contrast, that ECMP can provably achieve optimal traffic flow for the important category of Clos datacenter networks. We last consider a well-documented shortcoming of ECMP: suboptimal routing of large ("elephant") flows. We present algorithms for scheduling "elephant" flows on top of ECMP (as in, e.g., Hedera) with provable approximation guarantees. Our results complement and shed new light on past experimental and empirical studies of the performance of TE with ECMP.

  • 276.
    Chiesa, Marco
    et al.
    Roma Tre University.
    Lospoto, G.
    Rimondini, M.
    Di Battista, G.
    Intra-domain pathlet routing2013In: 2013 22nd International Conference on Computer Communications and Networks (ICCCN), IEEE Communications Society, 2013, article id 6614145Conference paper (Refereed)
    Abstract [en]

    Internal routing inside an ISP network is the foundation for lots of services that generate revenue from the ISP's customers. A fine-grained control of paths taken by network traffic once it enters the ISP's network is therefore a crucial means to achieve a top-quality offer and, equally important, to enforce SLAs. Many widespread network technologies and approaches (most notably, MPLS) offer limited (e.g., with RSVP-TE), tricky (e.g., with OSPF metrics), or no control on internal routing paths. On the other hand, recent advances in the research community are a good starting point to address this shortcoming, but miss elements that would enable their applicability in an ISP's network. We extend pathlet routing by introducing a new control plane for internal routing that pursues the following qualities: it is designed to operate in the internal network of an ISP; it enables fine-grained management of network paths with suitable configuration primitives; it is scalable because routing changes are only propagated to the network portion that is affected by the changes; it supports independent configuration of specific network portions without the need to know the configuration of the whole network; it is robust thanks to the adoption of multipath routing; it supports the enforcement of QoS levels; it is independent of the specific data plane used in the ISP's network; it can be incrementally deployed and it can nicely coexist with other control planes. Besides formally introducing the dissemination mechanisms and algorithms of our control plane, we propose an experimental validation in the simulation framework OMNeT++ that we use to assess the effectiveness and scalability of our approach.

  • 277.
    Chiesa, Marco
    et al.
    Roma Tre University, Italy.
    Lospoto, G.
    Rimondini, M.
    Di Battista, G.
    Intra-domain routing with pathlets2014In: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 46, p. 76-86Article in journal (Refereed)
    Abstract [en]

    Internal routing inside the network of an Internet Service Provider (ISP) affects the performance of lots of services that the ISP offers to its customers and is therefore critical to adhere to Service Level Agreements (SLAs), achieve a top-quality offer, and earn revenue. Existing technologies (most notably, MPLS) offer limited (e.g., with RSVP-TE), tricky (e.g., with OSPF metrics), or no control on internal routing paths. Recent research results address these shortcomings, but miss a few elements that would enable their application in an ISP's network. We introduce a new control plane, based on pathlet routing (Godfrey et al., 2009) [2], designed to operate in the network of an ISP and offering several nice features: it enables steering of network paths at different levels of granularity; it is scalable and robust; it supports independent configuration of specific network regions and differentiation of Quality of Service (QoS) levels; it can nicely coexist with other control planes and is independent of the data plane used in the ISP's network. Besides formally introducing the messages and algorithms of our control plane, we propose an experimental scalability assessment and comparison with OSPF, conducted in the simulation framework OMNeT++.

  • 278.
    Chiesa, Marco
    et al.
    Université catholique du Louvain, Belgium.
    Nikolaevskiy, I.
    Mitrovic, S.
    Gurtov, A.
    Madry, A.
    Schapira, M.
    Shenker, S.
    On the Resiliency of Static Forwarding Tables2017In: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 25, no 2, p. 1133-1146, article id 7728092Article in journal (Refereed)
    Abstract [en]

    Fast reroute and other forms of immediate failover have long been used to recover from certain classes of failures without invoking the network control plane. While the set of such techniques is growing, the level of resiliency to failures that this approach can provide is not adequately understood. In this paper, we embarked upon a systematic algorithmic study of the resiliency of forwarding tables in a variety of models (i.e., deterministic/probabilistic routing, with packet-headerrewriting, with packet-duplication). Our results show that the resiliency of a routing scheme depends on the "connectivity" k of a network, i.e., the minimum number of link deletions that partition a network. We complement our theoretical result with extensive simulations. We show that resiliency to four simultaneous link failures, with limited path stretch, can be achieved without any packet modification/duplication or randomization. Furthermore, our routing schemes provide resiliency against k - 1 failures, with limited path stretch, by storing log(k) bits in the packet header, with limited packet duplication, or with randomized forwarding technique.

  • 279.
    Chiesa, Marco
    et al.
    Université catholique du Louvain, Belgium.
    Nikolaevskiy, I.
    Mitrović, S.
    Panda, A.
    Gurtov, A.
    Maidry, A.
    Schapira, M.
    Shenker, S.
    The quest for resilient (static) forwarding tables2016In: INFOCOM 2016 - The 35th Annual IEEE International Conference on Computer Communications, IEEE, Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7524552Conference paper (Refereed)
    Abstract [en]

    Fast Reroute (FRR) and other forms of immediate failover have long been used to recover from certain classes of failures without invoking the network control plane. While the set of such techniques is growing, the level of resiliency to failures that this approach can provide is not adequately understood. We embark upon a systematic algorithmic study of the resiliency of immediate failover in a variety of models (with/without packet marking/duplication, etc.). We leverage our findings to devise new schemes for immediate failover and show, both theoretically and experimentally, that these outperform existing approaches.

  • 280.
    Chiesa, Marco
    et al.
    Université catholique du Louvain, Belgium.
    Rétvári, G.
    Schapira, M.
    Lying your way to better traffic engineering2016In: CoNEXT 2016 - Proceedings of the 12th International Conference on Emerging Networking EXperiments and Technologies, Association for Computing Machinery (ACM), 2016, p. 391-398Conference paper (Refereed)
    Abstract [en]

    To optimize the flow of traffic in IP networks, operators do traffic engineering (TE), i.e., tune routing-protocol parameters in response to traffic demands. TE in IP networks typically involves configuring static link weights and splitting traffic between the resulting shortest-paths via the Equal- Cost-MultiPath (ECMP) mechanism. Unfortunately, ECMP is a notoriously cumbersome and indirect means for optimizing traffic flow, often leading to poor network performance. Also, obtaining accurate knowledge of traffic demands as the input to TE is elusive, and traffic conditions can be highly variable, further complicating TE.We leverage recently proposed schemes for increasing ECMP's expressiveness via carefully disseminated bogus information ("lies") to design COYOTE, a readily deployable TE scheme for robust and efficient network utilization. COYOTE leverages new algorithmic ideas to configure (static) traffic splitting ratios that are optimized with respect to all (even adversarially chosen) traffic scenarios within the operator's "uncertainty bounds". Our experimental analyses show that COYOTE significantly outperforms today's prevalent TE schemes in a manner that is robust to traffic uncertainty and variation. We discuss experiments with a prototype implementation of COYOTE.

  • 281.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Jiang, Yuming
    NTNU (Norwegian University of Science and Technology).
    Fundamentals of the Backoff Process in 802.11: Dichotomy of the Aggregation2015In: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 61, no 4, p. 1687-1701Article in journal (Refereed)
    Abstract [en]

    This paper discovers fundamental principles of the backoff process that governs the performance of IEEE 802.11. A simplistic principle founded upon regular variation theory is that the backoff time has a truncated Pareto-type tail distribution with an exponent of $ { (log gamma !)/log m}$ ( $boldsymbol {m}$ is the multiplicative factor and $ {gamma }$ is the collision probability). This reveals that the per-node backoff process is heavy-tailed in the strict sense for $ { gamma > 1/m^{2}}$ , and paves the way for the following unifying result. The state-of-the-art theory on the superposition of the heavy-tailed processes is applied to establish a dichotomy exhibited by the aggregate backoff process, putting emphasis on the importance of time-scales on which we view the backoff processes. While the aggregation on normal time-scales leads to a Poisson process, it is approximated by a new limiting process possessing long-range dependence (LRD) on coarse time-scales. This dichotomy turns out to be instrumental in formulating short-term fairness, extending existing formulas to arbitrary population, and to elucidate the absence of LRD in practical situations. A refined wavelet analysis is conducted to strengthen this argument.

  • 282.
    Cho, Jeong-woo
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Le Boudec, Jean-Yves
    EPFL (École Polytechnique Fédérale de Lausanne).
    Jiang, Yuming
    NTNU (Norwegian University of Science and Technology).
    On the Asymptotic Validity of the Decoupling Assumption for Analyzing 802.11 MAC Protocol2012In: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 58, no 11, p. 6879-6893Article in journal (Refereed)
    Abstract [en]

    Performance evaluation of the 802.11 MAC protocol is classically based on the decoupling assumption, which hypothesizes that the backoff processes at different nodes are independent. This decoupling assumption results from mean field convergence and is generally true in transient regime in the asymptotic sense (when the number of wireless nodes tends to infinity), but, contrary to widespread belief, may not necessarily hold in stationary regime. The issue is often related with the existence and uniqueness of a solution to a fixed point equation; however, it was also recently shown that this condition is not sufficient; in contrast, a sufficient condition is a global stability property of the associated ordinary differential equation. In this paper, we give a simple condition that establishes the asymptotic validity of the decoupling assumption for the homogeneous case (all nodes have the same parameters). We also discuss the heterogeneous and the differentiated service cases and formulate a new ordinary differential equation. We show that the uniqueness of a solution to the associated fixed point equation is not sufficient; we exhibit one case where the fixed point equation has a unique solution but the decoupling assumption is not valid in the asymptotic sense in stationary regime.

  • 283.
    Cho, Ming-King
    KTH, Superseded Departments, Teleinformatics.
    Paving the Information Superhighway at SNRA: A Proposal for Multimedia Traffic Information Systems1995Independent thesis Advanced level (degree of Master (Two Years)), 12 credits / 18 HE creditsStudent thesis
  • 284.
    Cholaraju Narasaraju, Vignesh
    KTH, School of Information and Communication Technology (ICT).
    Impact of Extended DRX Cycles on Battery Lifetimes and UE Reachability2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Several UE energy consumption optimization techniques have been proposed for Machine Type Communication (MTC) devices. Extended Discontinuous Reception (eDRX) in idle mode is one such technique wherein an UE in idle mode wakes up only during its Paging Occasion (PO) to monitor paging messages from eNodeB (eNB). The PO is located within a Paging frame (PF). The PF is a function of System Frame Number (SFN) cycle of eNB. The paging messages may be sent asynchronously from multiple eNBs to a UE. Due to asynchronous operation of eNBs, SFN takes on different values at a given point in time and therefore a paging message is transmitted at different points in time from different eNBs. Due to this SFN misalignment between eNBs, an idle mode UE might receive and respond to the same paging message from different eNBs and/or miss a PO and thus the paging message. Due to this spread in time of SFN and PO, the actual handling of paging message by the UE becomes inefficient leading to increased UE energy consumption and decreased reachability. These issues, resulting from paging handling, will get amplified further if DRX period is extended longer (eDRX).

    In this study, we investigate the impact of eDRX cycles and mobility related parameters such as UE speed, cell size and size of SFN misalignment between eNBs on UE energy consumption, use of network resources and UE reachability. Receiving and responding to the same paging message results in increased energy consumption for UE and increased signaling between UE and the network. Missing a PO results in delayed paging reception and hence decreases UE reachability. As the DRX cycle lengths are increased from existing maximum of 2.56 seconds to 10.24 seconds and beyond, we see a reduction in UE energy consumption by more than 90%, but the network signaling and the delay to reach the UE increases linearly as a function of the DRX cycle length. We observe that the number of duplicate paging message receptions/missed POs is minuscule for DRX cycle lengths below 10.24 sec. At DRX cycle length of 10.24 seconds, UEs travelling across 500 m cell radius at speeds of 3, 50, 100 km/h the percentage of duplicate paging receptions are 0.07, 0.11, and 0.15 respectively. This duplicate paging message reception increases the UE energy consumption by 2.31, 6.15 and 12 percent of the total energy units respectively. Similarly, UE misses nearly 0.34, 0.39, and 0.405 percent of the total POs respectively. Depending on the number of consecutive PO misses, the UE reachability decreases. But by reducing the size of SFN misalignment between eNBs, we see that it’s possible to increase the reachability for UEs in eDRX. Further we have proposed solutions based on our analytical study to avoid duplicate paging message reception by UE, increase UE reachability and also reduce UE energy consumption using a windowing technique. We conclude that when a UE is configured with eDRX cycles, the tradeoff between battery lifetimes and UE reachability is based on mobility characteristics and service requirements.

  • 285.
    Choudrey, Sajaval
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Hiltunen, Kim
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Moln för Försvarsmakten2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    An organization with such a big responsibility as the Swedish armed forces constantly needs to find new ways to develop and increase their effectiveness when it comes to management, administration and organization. An information system with cloud computing as a basis would mean a modernization of the Swedish armed force’s administration and could potentially live up to the security standards within the organization. The primary goal of the thesis is to present and analyze cloud solutions that the Swedish armed forces eventually could integrate in to their activities. The first part of the thesis gives an introduction to the cloud technology with the security aspects of a cloud as a large part of the focus. This is followed by information about the Swedish armed forces and their current IT-systems, as well as information on the requirements they have for the implementation of new IT-systems within the organization. Two different cloud services from VMware and Cloudstack have been examined in order to see whether these could be used for a future implementation. The focus of the analysis lies heavily on the security issues and questions, that arise, for each solution, as the security aspect is something that is very important for the Swedish armed forces.

    The thesis also touches on the economical benefits and economical difficulties associated with cloud service implementation. The purpose of this is to see whether an eventual implementation is beneficial or not.

  • 286.
    Christensson, Anja
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Gerson, Nadine
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Wallin, Edit
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    A Mapping of Scandinavian Smart Grid Development in the Distribution System from an ICT perspective2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 287.
    Christiansson, Fredrik
    KTH, Superseded Departments, Teleinformatics.
    A distributed, mobile positioning systemfor wireless, handheld devices2000Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis investigates the possibilities of implementing a location awareness mechanism for the so-called lesswire localNavigator. The author claims that it is possible to implement such a mechanism within the given prerequisites and constraints, even though with today’s technology it may not be economically feasible.

    Due to the lesswire’s constraints: high accuracy (67%), high-resolution (12 m2) and no hardware modification allowed to the mobile device, the suggested scheme uses Time Difference Of Arrival technology (TDOA). The main advantage of TDOA, as stated in this thesis, is the fact that it is almost totally independent of the preferred wireless technology of the mobile device. TDOA technology therefore, can be applied to a wide range of wireless networks (primarily TDMA, CDMA, FDMA – based). A disadvantage of this scheme is the fact that the network infrastructure needs to be extremely well synchronized - which in turn implies higher costs.

    Depending on how the synchronization problem is solved, the proposed system may well be economically feasible in the near future.

  • 288.
    Chupisanyarote, Sanpetch
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kouyoumdjieva, Sylvia
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Helgason, Ólafur
    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.
    Caching in opportunistic networks with churn2012In: 2012 9th Annual Conference on Wireless On-Demand Network Systems and Services, WONS 2012, IEEE Communications Society, 2012, p. 39-42Conference paper (Refereed)
    Abstract [en]

    In this paper we examine opportunistic content distribution. We design and evaluate a caching strategy where a node will fetch and share contents on behalf of other nodes, although the contents are not of its own interest. We propose three caching options for improving the use of network resources: relay request on demand, hop-limit, and greedy relay request. The proposed strategies are implemented in the OMNeT++ simulator and evaluated on mobility traces from Legion Studio that have churn. We also compare our strategies with a strategy from the literature. The results are analyzed and they show that the use of opportunistic caching for a community of nodes may enhance the performance marginally while overhead increases significantly.

  • 289.
    Cobo Jiménez, Enrique
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Nakarmi, P. K.
    Näslund, M.
    Norrman, K.
    Subscription identifier privacy in 5G systems2017In: 2017 International Conference on Selected Topics in Mobile and Wireless Networking, MoWNeT 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 8045947Conference paper (Refereed)
    Abstract [en]

    Privacy is a main concern for mobile network users, and there are many proposed enhancements for the protection of the long-Term subscription identifier. Some enhancements require asymmetric key operations, which increase both processing requirements and protocol message sizes. To the best of our knowledge, there has been no practical implementation feasibility study of these enhancements using commodity mobile devices. Neither is it clear whether the enhancements are sufficient. This paper highlights privacy weaknesses, when the long-Term subscription identifier is used in Paging procedures, and proposes new ways to resolve these. Further, the paper evaluates an Android implementation of one of the enhancements, which includes the asymmetric scheme Elliptic Curve Integrated Encryption Scheme (ECIES). We conclude that it is feasible to implement asymmetric encryption methods for the long-Term subscription identifier and that the highlighted privacy weaknesses can be efficiently countered. This removes another set of obstacles for realizing the protection in mobile network standards.

  • 290.
    Collin, Guillaume
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Chazalet, Boris
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Exploiting cooperative behaviors for VoIP communication nodes in a wireless local area network2007Report (Other academic)
    Abstract [en]

    The purpose of this project was to implement a new design for VoIP communication in a wireless local area. One of the main goals was to experiment with a new approach that exploits cooperative behaviors. By cooperative we mean that the nodes try to cooperate so as to achieve higher cell capacity.

    VoIP communications has such specific data flows that it is interesting to build protocols that exploit these characteristics, for example for speech these characteristics are: regularity and timeconstrained delivery. Furthermore the wireless local area network brings another dimension in terms of all of the nodes sharing a wireless cell, as the nodes will share a common bandwidthlimited media. In the current standard for wireless local area networks the computers in the cell have to contend to get access to the shared media which can lead to delays, even if the bandwidth needed is much lower than the bandwidth available. If we focus on the needs of VoIP, one way to improve this is for all nodes to cooperate by organizing themselves to efficiently share the media. If they can agree with each other on what time each node will transmit, then they don't need to contend anymore. Thus the VoIP packets can reach their destination on time and while minimizing the use of resources in this cell.

    In this project we have designed and test a proof of concept of this cooperation in order to prove that it can work and to show what effects and performance it implies. This work can also be seen more generally as contextawareness research where the contextawareness is used to provide input to the cooperative behavior.

  • 291. Colman-Meixner, C.
    et al.
    Figueiredo, G. B.
    Fiorani, Matteo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Tornatore, M.
    Mukherjee, B.
    Resilient cloud network mapping with virtualized BBU placement for cloud-RAN2017In: 2016 IEEE International Conference on Advanced Networks and Telecommunications Systems, ANTS 2016, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7947790Conference paper (Refereed)
    Abstract [en]

    Cloud Radio Access Network (C-RAN) will improve mobile radio coordination and resource efficiency by allowing baseband processing unit (BBU) functions to be virtualized and centralized, i.e., deployed in a BBU hotel. We consider a BBU hoteling scheme based on the concept of access cloud network (ACN). An ACN consists of virtualized BBUs (vBBUs) placed in metro cloud data centers (metro DCs). A vBBU is connected to a set of remote radio heads (RRHs). ACN resiliency against network and processing failures is critical for C-RAN deployments. Hence, in this study, we propose three protection approaches: 1+1 ACN protection, 1+1 ACN and vBBU protection, and partial ACN protection. Simulation results show that both 1+1 ACN and 1+1 ACN and vBBU protection requires large capacity for backup to provide 100% survivability for singlelink and single-DC failures. As a result, we suggest a partial ACN protection approach which provides degraded services with only 8% additional network resources.

  • 292.
    Corcoran, Diarmuid
    et al.
    KTH. Ericsson AB.
    Andimeh, Loghman
    Ericsson AB.
    Ermedahl, Andreas
    Ericsson AB.
    Kreuger, Per
    RISE SICS AB.
    Schulte, Christian
    KTH, Superseded Departments (pre-2005), Microelectronics and Information Technology, IMIT.
    Data Driven Selection of DRX for Energy Efficient 5G RAN2017In: 2017 13TH INTERNATIONAL CONFERENCE ON NETWORK AND SERVICE MANAGEMENT (CNSM), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    The number of connected mobile devices is increasing rapidly with more than 10 billion expected by 2022. Their total aggregate energy consumption poses a significant concern to society. The current 3gpp (3rd Generation Partnership Project) LTE/LTE-Advanced standard incorporates an energy saving technique called discontinuous reception (DRX). It is expected that 5G will use an evolved variant of this scheme. In general, the single selection of DRX parameters per device is non trivial. This paper describes how to improve energy efficiency of mobile devices by selecting DRX based on the traffic profile per device. Our particular approach uses a two phase data-driven strategy which tunes the selection of DRX parameters based on a smart fast energy model. The first phase involves the off-line selection of viable DRX combinations for a particular traffic mix. The second phase involves an on-line selection of DRX from this viable list. The method attempts to guarantee that latency is not worse than a chosen threshold. Alternatively, longer battery life for a device can be traded against increased latency. We built a lab prototype of the system to verify that the technique works and scales on a real LTE system. We also designed a sophisticated traffic generator based on actual user data traces. Complementary method verification has been made by exhaustive off-line simulations on recorded LTE network data. Our approach shows significant device energy savings, which has the aggregated potential over billions of devices to make a real contribution to green, energy efficient networks.

  • 293.
    Cordella, Marco
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    User-to-Network Interface in Optical Network2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This masters thesis work was carried out at the Optical Network Research Laboratory Ericsson Telecom AB in Kungens Kurva (Sweden). Its primary objective is to study the O-UNI (Optical User-to-Network Interface), a service control interface between client devices (e.g., IP routers and ATM switches) and the transport network, and the different signaling protocols running over it.

    This thesis was conducted for the Institute for Microelectronics and Information Technology (IMIT) at the Royal Institute of Technology (KTH) in Stockholm (Sweden) and for the Department of Telecommunications at Politecnico di Torino in Turin (Italy).

    Recently, the Internet Engineering Task Force (IETF), the Optical Internetworking Forum (OIF) and the International Telecommunication Union (ITU) have all started working on standards for routing and signaling protocols for the Optical Transport Network (OTN). While these efforts aim to create a set of protocols to act as the interface to an optical core, the emerging architectures are different enough to present difficult choices for vendors and service providers. The goal of this thesis work was to analyze the state of the art of the OIF based UNI (User-to-Network Interface) in order to gain competence in the area and study this UNI model by implementing some of the abstract messages defined in the UNI 1.0. In particular, the UNI signaling protocols, adapted from the GMPLS RSVP-TE (Generalized Multi-Protocol Label Switching) (Resource Reservation Protocol - Traffic Engineering) and LMP (Link Management Protocol) specifications were implemented.

  • 294.
    Costa, J.
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Zander, Jens
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Context-Aware Framework for Energy Efficient Machine-to-Machine CommunicationsIn: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896Article in journal (Refereed)
    Abstract [en]

    Cellular network based Machine-to-Machine(M2M) communications have been growing rapidly in recentyears, being used in a wide range of services such as security,metering, health, remote control, tracking and so on. A criticalissue that needs to be considered in M2M communications isthe energy efficiency, typically the machines are powered bybatteries of low capacity and it is important to optimize the waythe power is consumed. In search of better M2M systems, wepropose a context-aware framework for M2M communicationsso the machine type communication (MTC) devices dynamicallyadapt their settings depending on a series of characteristicssuch as data reporting mode and quality of service (QoS)features so higher energy efficient is achieved, extending theoperating lifetime of the M2M network. Simulations results willbe provided for four commonly used M2M applications: homesecurity, telehealth, climate and smart metering, showing thatconsiderable energy savings and operating lifetime extension onthe network can be achieved. Thus, contexts play an importantrole on the energy efficiency of a M2M system.

  • 295.
    Coyet, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Mobil Positionering med Kartstöd2003Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis was conducted on behalf of SL Infrateknik AB. The goal of the master thesis was to examine the possibilities for SL to create a mobile positioning service with map support for their travellers. The result would give SL a basis for making decisions relating to the development of such a service.

    The studies have focused on different techniques of positioning and the existing operators in the Swedish market that provide positioning. To acquire understanding of services with map support, the construction and usage of geographic information systems have been examined. These studies have also involved the use of geographic information systems for map presentation on mobile units.

    Since SL’s traffic covers the whole county of Stockholm, it was important to study how SL can reach as many travellers as possible with the new service. However, the accuracy of mobile positioning varies significantly depending on the geographic location. Measurements showed that the accuracy outside Stockholm’s city centre is poor. With 3G, the accuracy is expected to be a bit better. The current conditions are therefore not suitable for creating a positioning service with acceptable accuracy for the whole county of Stockholm.

    The conclusion is that SL should not invest in a mobile positioning service at present. This conclusion is mainly based on such factors as accuracy, choice of operator and communication performance.

  • 296.
    Crespo Ramírez, Daniel
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Smartphone traffic patterns2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The growing popularity of new generation mobile terminals, known as „smartphones‟,has increased the variety and number of such devices. These devices make use of the resources offered by Universal Mobile Telecommunication Services (UMTS) networks toaccess on-line services such as web browsing, e-mail, audio and video streaming, etc. UMTS networks have to deal with an increasing amount of data traffic generated by smartphones. Because of the fact that the smartphone is battery powered and is trying to satisfy the needs ofboth applications and human users there is a need to be smarter about how to manage both network and terminal resources.

    This thesis explores the possibility of making a better use of the network and terminal resources by exploiting correlations in the events of the smartphone-generated traffic. We propose a mechanism, through which the network can predict if a terminal is going to produce data transmission or reception in a near future, based on past events in its traffic. According to this prediction, the network will be able to decide if it keeps or releases the resources allocated to the terminal. We analyze the benefits from the network and the terminal point ofview. We also describe a method to estimate an upper bound of the time until the next transmission or reception of data in a near future.

    We show that it is possible a reduction of the time that each terminal wastes in its maximum power consumption state, but this reduction implies a penalty in the transmission/reception throughput of the terminal. The reduction is not uniform for all terminals: terminals whose traffic presents a predictable behavior gain the most. Estimates of upper bounds of time until the next transmission or reception are more accurate if they are made taking as input information about interarrival times of previous packets.

  • 297.
    Cui, Yaping
    et al.
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China.;Chongqing Univ Posts & Telecommun, Sch Commun & Informat Engn, Chongqing 400065, Peoples R China..
    Fang, Xuming
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China..
    Fang, Yuguang
    Univ Florida, Dept Elect & Comp Engn, Gainesville, FL 32611 USA..
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Optimal Nonuniform Steady mmWave Beamforming for High-Speed Railway2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 5, p. 4350-4358Article in journal (Refereed)
    Abstract [en]

    Using higher frequency bands (e.g., millimeter waves) to provide higher data rate is an effective way to eliminate performance bottleneck for future wireless networks, particularly for cellular networks based high-speed railway (HSR) wireless communication systems. However, higher frequency bands suffer from significant path loss and narrow-beam coverage, which pose serious challenges in cellular networks, especially under the HSR scenario. Meanwhile, as one of the key performance indexes of ultrareliable and low-latency communications in 5G systems, network reliability should be guaranteed to provide steady reliable data transmission along the railway, especially when safety-critical railway signaling information is delivered. In this paper, we propose a novel beamforming scheme, namely, optimal nonuniform steady mmWave beamforming, to guarantee the network reliability under an interleaved redundant coverage architecture for future HSR wireless systems. Moreover, we develop a bisection-based beam boundary determination (BBBD) method to determine the service area of each predefined RF beam. Finally, we demonstrate that the proposed optimal nonuniform steady mmWave beamforming can provide steady reliable data transmissions along the railway, and the network reliability requirements can be guaranteed when the proposed BBBD method is used. We expect that our optimal nonuniform steady mmWave beamforming provides a promising solution for future HSR wireless systems.

  • 298. D, ASTELY
    et al.
    Larsson, Peter
    Ericsson Research, Isafjordsgatan 14E, 164 93 Kista, Sweden.
    Method for determining transmit weights2003Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    NOVELTY - The transmission weights associated to pilot sequences (p1-p_N) containing symbols with predetermined time, frequency resource and complex transmission weights (W11-W_N_M) are adapted for optimizing the multicast transmission of pilot signal. The multiple information stream are transmitted using adapted transmission weights. USE - For beam-forming data transmission in multi-carrier multi-user communication system such as orthogonal frequency division multiplexing (OFDM) system. ADVANTAGE - Improves downlink channel quality by using feedback information from mobile terminals in response to the received pilot signals, thereby increasing transmission efficiency. DESCRIPTION OF DRAWING(S) - The figure shows a schematic diagram of the communication system. communication system (10) access point (11) pilot sequences (p1-p_N) mobile terminals (MS1-MS4) complex transmission weights (W11-W_N_M)

  • 299.
    da Silva, Carlos Natalino
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Yayimli, Aysegul
    Istanbul University of Technology.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Assessing the effects of physical layer attacks on content accessibility and latency in optical CDNs2017In: 19th International Conference on Transparent Optical Networks (ICTON), Girona, Spain: IEEE conference proceedings, 2017, article id 8024993Conference paper (Refereed)
    Abstract [en]

    Content Delivery Networks (CDNs) are a major enabler of large-scale content distribution for Internet applications. Many of these applications require high bandwidth and low latency for a satisfactory user experience, e.g., cloud gaming, augmented reality, tactile Internet and vehicular communications. Replication is one of the most prominent solutions to meet the requirements of latency-sensitive applications. However, infrastructure disruptions can greatly degrade the performance of such applications, or even cease their proper execution. The extent of degradation can be exacerbated by malicious attackers that target the critical elements of the CDN physical infrastructure to disconnect or severely degrade services.

  • 300.
    da Silva, Carlos Natalino
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Yayimli, Aysegul
    Istanbul University of Technology.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Content Accessibility in Optical Cloud Networks Under Targeted Link Cuts2017In: 2017 21st International Conference on Optical Network Design and Modeling, ONDM 2017 - Conference Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7958546Conference paper (Refereed)
    Abstract [en]

    One of the key enablers of the digital society is a highly reliable information infrastructure that can ensure resiliency to a wide range of failures and attacks. In cloud networks, replicas of various content are located at geographically distributed data centers, thus inherently enhancing cloud network reliability through diversification and redundancy of user accessibility to the content. However, cloud networks rely on optical network infrastructure which can be a target of deliberate link cuts that may cause service disruption on a massive scale. This paper investigates the dependency between the extent of damage caused by link cuts and a particular replica placement solution, as a fundamental prerequisite of resilient cloud network design that lacks systematic theoretical quantification and understanding. To quantify the vulnerability of optical cloud networks based on anycast communication to targeted link cuts, we propose a new metric called Average Content Accessibility (ACA). Using this metric, we analyze the impact of the number and the placement of content replicas on cloud network resiliency and identify the best and the worst case scenarios for networks of different sizes and connectivity. We evaluate the efficiency of simultaneous and sequential targeted link cuts, the latter reassessing link criticality between subsequent cuts to maximize disruption. Comparison with Average Two-Terminal Reliability (A2TR), an existing robustness measure for unicast networks, shows great discrepancy in the vulnerability results, indicating the need for new measures tailored to anycast-based networks.

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