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  • 251.
    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, 6879-6893 p.Article 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.

  • 252.
    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    KTH, Superseded Departments, Teleinformatics.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
  • 253.
    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.

  • 254.
    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.

  • 255.
    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
  • 256.
    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.

  • 257.
    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, 39-42 p.Conference 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.

  • 258.
    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, 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.

  • 259.
    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.

  • 260. 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, 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.

  • 261.
    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.

  • 262.
    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.

  • 263.
    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.

  • 264.
    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.

  • 265. 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)

  • 266.
    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, 2017Conference paper (Other academic)
    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.

  • 267.
    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, 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.

  • 268.
    Dabbous, Fouad
    KTH, Superseded Departments, Teleinformatics.
    The mobitex network in the point of sale application1995Independent thesis Advanced level (degree of Master (Two Years)), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    The Purpose of the work is to provide a solution for interfacing the point-of-sale terminal (POST) with Mobitex radio modem (mobidem) on the mobile side and a solution for interfacing the authorization center host computer with the Mobitex area exchanges (MOX), at the fixed side. The application of POS was coded to use the Mobitex network as a communication link between the POST and the host computer.

    An existing POS application was used during the simulation where the communication procedure had been rewritten to meet the Mobitex network communication specifications. Analyses and ideas related to the suggested communication model and procedure were discussed during the simulation phase.

  • 269.
    Dahlberg, Axel
    et al.
    KTH, School of Technology and Health (STH), Data- och elektroteknik.
    Francén, Jonas
    KTH, School of Technology and Health (STH), Data- och elektroteknik.
    IPv6-adresshantering och prefixdelegering i MPLS VPN-nät2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Full migration to IPv6 brings the need to adjust datacommunication services for the new generationof IP protocols with maintained or expanded functionality. This thesis’ goals is to submitone or more solutions that meets requirements and the technical conditions that enables thecompany DGC:s to expand the service IP-VPN for IPv6. This includes address assignmenttechniques like prefix delegation and automatic address configuration in existing network infrastructure.Solutions are presented in six scenarios that have been investigated considering tests, analysis andexperienced problems. The investigation formed the criteria scalability, configuration complexity,compatibility, support by RFC:s and requirements stated by DGC that adds to the evaluationof the most suitable solution.The evaluation has resulted in a recommended scenario that is implementable according to givengoals.Techniques that may influence the choice of most suitable solution, but that is not yet available,are discussed and presented to point out what may needed to be considered in the future.

  • 270.
    Dahlman, Erik
    et al.
    KTH.
    Mildh, G.
    Parkvall, S.
    Peisa, J.
    Sachs, J.
    Selén, Y.
    5G radio access2014In: Ericsson review (English ed.), ISSN 0014-0171, Vol. 91, no 1, 42-47 p.Article in journal (Other academic)
    Abstract [en]

    Mobile communication has evolved significantly from early voice systems to today's highly sophisticated integrated communication platforms that provide numerous services, and support countless applications used by billions of people around the world.

  • 271.
    Dalarsson, Stefan
    KTH, School of Information and Communication Technology (ICT). Department of Mathematics.
    ANALYTICAL AND NUMERICAL STUDY OF HELICAL ANTENNAS IN RADIO DEVICES USING INTEGRAL EQUATIONS2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 272.
    Damola, Ayodele
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Peer to peer networking in Ethernet broadband access networks2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The use of peer-to-peer (P2P) applications is growing dramatically, particularly for sharing content such as video, audio, and software. The traffic generated by these applications represents a large proportion of Internet traffic. For the broadband access network providers P2P traffic presents several problems.

    This thesis identifies the performance and business issues that P2P traffic has on broadband access networks employing the McCircuit separation technique. A mechanism for managing P2P within the access network is proposed. The P2P diversion algorithm aims to manage P2P traffic within the access network based on layer 2 and layer 3 information without employing intrusive layer 7 traffic detection. To solve the contention problem experienced by best effort traffic in the access network, a solution based on the diversion algorithm and on a QoS based traffic classification scheme is proposed. A business model defining the business roles and pricing schemes is presented based on the features offered by the P2P diversion algorithm introducing new opportunities for gaining revenue from P2P traffic for the network service providers and providing better services to users.

  • 273.
    Dan, Jurca
    et al.
    NTT DOCOMO Eurolabs in Munich, Germany.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES).
    H-GAP: Estimating Histograms of Local Variables with Accuracy Objectives for Distributed Real-Time Monitoring2010In: IEEE Transactions on Network and Service Management, ISSN 1932-4537, E-ISSN 1932-4537, Vol. 7, no 2, 83-95 p.Article in journal (Refereed)
    Abstract [en]

    We present H-GAP, a protocol for continuous monitoring,which provides a management station with the valuedistribution of local variables across the network. The protocolestimates the histogram of local state variables for a givenaccuracy and with minimal overhead. H-GAP is decentralizedand asynchronous to achieve robustness and scalability, and itexecutes on an overlay interconnecting management processesin network devices. On this overlay, the protocol maintains aspanning tree and updates the histogram through incrementalaggregation. The protocol is tunable in the sense that it allowscontrolling, at runtime, the trade-off between protocol overheadand an accuracy objective. This functionality is realized throughdynamic configuration of local filters that control the flow ofupdates towards the management station. The paper includes ananalysis of the problem of histogram aggregation over aggregationtrees, a formulation of the global optimization problem, anda distributed solution containing heuristic, tree-based algorithms.Using SUM as an example, we show how general aggregationfunctions over local variables can be efficiently computed withH-GAP. We evaluate our protocol through simulation using realtraces. The results demonstrate the controllability of H-GAP ina selection of scenarios and its efficiency in large-scale networks.

  • 274.
    Dandugula, Chaitanya
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Networking for Smart Meters2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    "Smart grid" generally refers to a class of technology bringing electricity delivery systems into the 21st century, using computer-based remote control and automation. With the growing energy demand, efficient usage of the available energy resources is increasingly becoming a major issue around the world. Smart grid is a step in that direction. Research in the European Union and the United States are currently underway to modernize the existing and aging transmission grid and to streamline the usage of electricity.

    A typical electricity grid consists of two major entities - the utility company and the distribution control system (DCS). Electricity is generated at the utility company and the DCS is responsible for the distribution of electricity to individual homes/consumers. A smart meter (SM) is an electronic device that measures the electricity consumed at the consumer's premises and provides added information to the utility company. The data concentration unit (DCU) is a device acting as a communication hub collecting and encoding data from multiple smart meters in a neighborhood and forwarding the data to the utility company. The aim of this project is to design a network for securing the communication between the SM and the DCU in a smart metering network environment.

    The meter data communicated from the SM to the DCU is very sensitive and in the hands of an attacker, can reveal significant personal information about an individual. Hence it is of at most importance to protect the meter data transmitted from the SM. On the other hand the control signals transmitted from the DCU to the SM, need protection in order to thwart off unauthorized signals (i.e., an intruder can impersonate the DC and send out control signals to the SMs). Hence the SM and the DCU should be authenticated by each other and authorized and the data and/or control signals exchanged between them should be encrypted.

  • 275. Daneshtalab, M.
    et al.
    Ebrahimi, M.
    Liljeberg, P.
    Plosila, J.
    Tenhunen, Hannu
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. University of Turku, Finland.
    High-performance on-chip network platform for memory-on-processor architectures2011In: 6th International Workshop on Reconfigurable Communication-Centric Systems-on-Chip, ReCoSoC 2011 - Proceedings, 2011, 5981509Conference paper (Refereed)
    Abstract [en]

    Three Dimensional Integrated Circuits (3D ICs) are emerging to improve existing Two Dimensional (2D) designs by providing smaller chip areas, higher performance and lower power consumption. Stacking memory layers on top of a multiprocessor layer (logic layer) is a potential solution to reduce wire delay and increase the bandwidth. To fully employ this capability, an efficient on-chip communication platform is required to be integrated in the logic layer. In this paper, we present an on-chip network platform for the logic layer utilizing an efficient network interface to exploit the potential bandwidth of stacked memory-on-processor architectures. Experimental results demonstrate that the platform equipped with the presented network interface increases the performance considerably.

  • 276.
    Dannerud, Sara
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Sårbarheter i routrar och switchar2008Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    There are a lot of different sources to information about vulnerabilities in routers and switches. The amount of information means that there is no easy way to find out which vendors are affected by vulnerabilities and what types of vulnerabilities that are found in network equipment. Thereby it is also hard to know how to protect your equipment against attacks.

    In this thesis a number of already existing vulnerabilities in router and switches are being analyzed. These vulnerabilities have been chosen by searching the National Vulnerability Database using the words “router” and “switch”. The aim of the analysis is to answer the questions who, what and why when it comes to vulnerabilities in routers and switches. The thesis describes which vendors are exposed to vulnerabilities, what types of vulnerabilities that are most common among routers and switches and why these vulnerabilities have came up. Based on this information, conclusions are drawn regarding what the user should do to avoid vulnerabilities in their equipment. The way the companies deal with vulnerabilities in their products is also described.

  • 277. Dargie, W.
    et al.
    Schill, A.
    Mochaourab, Rami
    Guan, L.
    A Topology Control Protocol for 2D Poisson Distributed Wireless Sensor Networks2009Conference paper (Refereed)
    Abstract [en]

    Topology control in a wireless sensor network is useful for ensuring that the network remains connected in the presence of nodes that exhaust their energy or become altogether dysfunctional (for whatever reasons). It also ensures that all the link that can be established are energy-efficient links and the nodes utilize their energy fairly. In this paper, we propose a fair and energy efficient topology control protocol for a two-dimensional random sensor deployment in which the nodes can estimate the distances to their neighbors and vary their transmission power accordingly. The protocol applies a neighbor eligibility metric in order to ensure a fair distribution of energy in the network. We introduce the notion of weighted relaying regions defined over the plane of a searching node to drop out inefficient links. Unlike most topology control protocols that rely on nearest neighbor approaches, we use a distance measure that is radio characteristic and channel condition dependent. We verify the performance of the protocol through simulation results on network graph properties and energy consumption.

  • 278.
    Darwis, Darwis
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Implementation and Analysis of VoIP CPE Management System using TR-0692008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Customer Premises Equipment (CPE) management is underestimated by the CPE vendors and services providers while it is in fact one of the most important aspects to ensure the high quality of service. Many people still think CPE management is the same as network management. Thus, they use the Simple Network Management Protocol (SNMP) to manage their CPEs. However, SNMP alone was thought not to scale nor to support the provisioning of the types of services which internet services providers must support today.

    This thesis highlights the importance of CPE management, how it is implemented using the TR-069; a CPE management protocol defined by the DSL Forum, and how a management system can be used for VoIP service management, and whether a CPE should implement TR-069 or SNMP as the management system to support. In the addition, the TR-069 will be compared against the SNMP to determine which one is more suitable for CPE management. An interesting conclusion is that while TR-069 does have some advantages over SNMP for managing services rather than simply managing the device, these advantages are not a large as initially believed nor has TR-069 avoided the problem of proprietary management information which SNMP has demonstrated.

  • 279.
    Datta, Anwitaman
    et al.
    NTU Singapore.
    Buchegger, Sonja
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Vu, Le Hung
    EPFL.
    Rzadca, Krzysztof
    Warsaw University.
    Strufe, Thorsten
    TU Darmstadt.
    Decentralized Online Social Networks2010In: Handbook of Social Network Technologies and Applications / [ed] Borko Furht, Springer, 2010, 349-378 p.Chapter in book (Refereed)
    Abstract [en]

    Current Online social networks (OSN) are web services run on logically centralized infrastructure. Large OSN sites use content distribution networks and thus distribute some of the load by caching for performance reasons, nevertheless there is a central repository for user and application data. This centralized nature of OSNs has several drawbacks including scalability, privacy, dependence on a provider, need for being online for every transaction, and a lack of locality. There have thus been several efforts toward decentralizing OSNs while retaining the functionalities offered by centralized OSNs. A decentralized online social network (DOSN) is a distributed system for social networking with no or limited dependency on any dedicated central infrastructure. In this chapter we explore the various motivations of a decentralized approach to online social networking, discuss several concrete proposals and types of DOSN as well as challenges and opportunities associated with decentralization.

  • 280. Daudi, M.
    et al.
    Hauge, Jannicke
    KTH, School of Technology and Health (STH). University of Bremen, Germany.
    Thoben, K. -D
    Effects of decision synchronization on trust in collaborative networks2016In: 17th IFIP WG 5.5 Working Conference on Virtual Enterprises, PRO-VE 2016, Springer-Verlag New York, 2016, 215-227 p.Conference paper (Refereed)
    Abstract [en]

    In collaborative networks, individual and organizational entities encounter many disagreements over many decisions rights. These disagreements procreate conflicting preferences, which in turn, affect trustworthy amongst partners. To that end, it becomes necessary that partners assume a degree of fairness on decision rights by calibrating positions which they initially consider a final. This calibration involves synchronizing partners’ conflicting preferences to a compromise. The objective of this paper, therefore, is to analyze and evaluate the effect of both, compromised and uncompromised preferences on trust. To achieve this, a corresponding behavioral trust model is proposed and evaluated empirically using a logistics collaboration scenario. This evaluation applies a multi-agent systems simulation method. The simulation involves 360 observations with three preferences set as predictor variables. Results show that irrespective of a degree to which conflicting preferences are synchronized, a magnitude of the generated effect on trust, depends as well on other factors like transport cost and extent to which vehicles are loaded. Additionally, if other factors are kept constant, compromised preferences affects trust more positively than uncompromised ones.

  • 281.
    De Andrade, Marilet
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Skubic, Björn
    Ahmed, Jawwad
    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).
    Enhanced IPACT: solving the over-granting problem in long-reach EPON2013In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 54, no 2, 137-146 p.Article in journal (Refereed)
    Abstract [en]

    In this paper we address an issue referred to as "over-granting problem", which is inherent in the existing dynamic bandwidth allocation algorithms for Ethernet-based Passive Optical Networks (EPON), in particular when deployed for multi-threaded scheme in long-reach scenario. In order to solve this problem we design a scheme for the algorithm of Interleaved Polling with Adapted Cycle Time (IPACT) with the limited service discipline. We evaluate the proposed scheme through simulations for single-thread and double-thread cases and demonstrate that, the network performance can be significantly improved by our solution in terms of average delay, jitter, and throughput.

  • 282.
    de Carvalho, Elisabeth
    et al.
    Aalborg University.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Leinkeit, Florian
    University of Bremen.
    Bockelmann, Carsten
    University of Bremen.
    Popovski, Petar
    Aalborg University.
    Relaying and Wireless Network Coding2016In: 5g Mobile and Wireless Communications Technology / [ed] Afif Osseiran, Jose F. Monserrat, Patrick Marsch, Cambridge University Press, 2016, 277-302 p.Chapter in book (Other academic)
    Abstract [en]

    Relaying and network coding are powerful techniques that improve the performance of a cellular network, for example by extending the network coverage, by increasing the system capacity or by enhancing the wireless link reliability. This chapter focuses on relaying and wireless network coding in 5G. After reviewing the history of relaying, the key envisioned scenarios for relaying in 5G are highlighted, namely the provisioning of wireless backhaul in Ultra-Dense Networks (UDNs), for nomadic cells or for data aggregation in the context of massive machine-type communications. While full-duplex technology is slowly gaining maturity, it is expected that due to complexity reasons most relaying scenarios in 5G will be based on half-duplex devices. Therefore, finding solutions to overcome the half-duplex limitation remains critical. The chapter describes the following three key innovations for efficient half-duplex relaying:

    • By applying the principles of wireless network coding to distributed multi-way traffic, in-band relaying becomes a spectrally efficient solution for wireless backhaul in ultra-dense networks of small cells, despite conventional views.

    • Non-orthogonal multiple access techniques, as required by physical-layer network coding, are essential for increased spectral efficiency when simultaneous multi-flows are exchanged through a same relay. Here, Interleave-Division Multiple-Access (IDMA) is put forward for its ability to support flexible rate requirements.

    • Buffer-aided relaying is featured where different ways to exploit buffering are described for improved diversity and increased rates. This technique targets delay tolerant applications having high data rate requirements.

  • 283.
    de Fréin, Ruairí
    et al.
    TSSG, Waterford Institute of Technology, Waterford, Ireland.
    Olariu, Cristian
    University College Dublin.
    Song, Yuqian
    Trinity College Dublin.
    Brennan, Rob
    Trinity College Dublin.
    McDonagh, Patrick
    University College Dublin.
    Hava, Adriana
    University College Dublin.
    Thorpe, Christina
    University College Dublin.
    Murphy, John
    University College Dublin.
    Murphy, Liam
    University College Dublin.
    French, Paul
    IBM .
    Integration of QoS Metrics, Rules and Semantic Uplift for Advanced IPTV Monitoring2014In: Journal of Network and Systems Management, ISSN 1573-7705, Vol. 23, no 3, 1-36 p.Article in journal (Refereed)
    Abstract [en]

    Increasing and variable traffic demands due to triple play services pose significant Internet Protocol Television (IPTV) resource management challenges for service providers. Managing subscriber expectations via consolidated IPTV quality reporting will play a crucial role in guaranteeing return-on-investment for players in the increasingly competitive IPTV delivery ecosystem. We propose a fault diagnosis and problem isolation solution that addresses the IPTV monitoring challenge and recommends problem-specific remedial action. IPTV delivery-specific metrics are collected at various points in the delivery topology, the residential gateway and the Digital Subscriber Line Access Multiplexer through to the video Head-End. They are then pre-processed using new metric rules. A semantic uplift engine takes these raw metric logs; it then transforms them into World Wide Web Consortium’s standard Resource Description Framework for knowledge representation and annotates them with expert knowledge from the IPTV domain. This system is then integrated with a monitoring visualization framework that displays monitoring events, alarms, and recommends solutions. A suite of IPTV fault scenarios is presented and used to evaluate the feasibility of the solution. We demonstrate that professional service providers can provide timely reports on the quality of IPTV service delivery using this system.

  • 284.
    de Fréin, Ruairí
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Pfaff, Joel
    Amadeus SAS, Sophia Antipolis, Nice, France.
    Paré, Thomas
    Amadeus SAS, Sophia Antipolis, Nice, France.
    Enterprise Data Center Globality Measurement2015In: Proceedings - 15th IEEE International Conference on Computer and Information Technology, CIT 2015, 14th IEEE International Conference on Ubiquitous Computing and Communications, IUCC 2015, 13th IEEE International Conference on Dependable, Autonomic and Secure Computing, DASC 2015 and 13th IEEE International Conference on Pervasive Intelligence and Computing, PICom 2015, Institute of Electrical and Electronics Engineers (IEEE), 2015, Liverpool: IEEE Computer Society, 2015, 1861-1869 p.Conference paper (Refereed)
    Abstract [en]

    Measurement of the globality of On-Line Transac- tion Processing (OLTP) workloads in Enterprise Data Centers is considered. Providing OLTP workload isolation (application, services and databases) for performance-sensitive enterprise workloads, so that activity in one workload cannot interfere with another, remains a challenge. We demonstrate that traditional aggregate OLTP Workload globality measurement frameworks can generate mis-leading globality measures. We propose a higher-order globality measurement framework which addresses this problem. We derive two high dimensional structured mea- surement matrices, namely a template and measurand matrix, with special spectral properties, which account for globality mea- surement 1) boundedness; 2) programmability; 3) multiplicity; 4) relativity; 5) spatial correlation and 6) the appropriate sensitivity of the measure to changes in the distribution of the workload. We demonstrate that these properties are exhibited by the new measure by ordering OLTP workloads by their globality measure. We evaluate the measure using a stochastic layered block model for data center topology and OLTP workload generation and demonstrate that it is consistent.

  • 285. De Nardis, L.
    et al.
    Di Benedetto, M. -G
    Tassetto, D.
    Bovelli, S.
    Akhtar, A.
    Holland, O.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Impact of mobility in cooperative spectrum sensing: Theory vs. simulation2012In: Wireless Communication Systems (ISWCS), 2012 International Symposium on, IEEE , 2012, 416-420 p.Conference paper (Refereed)
    Abstract [en]

    This work addresses the problem of cooperative spectrum sensing in cognitive radio networks, focusing on the impact of mobility on performance of cooperative sensing. First, a review of the most recent results on cooperative spectrum sensing is provided, resulting in the identification of measurement correlation and frame error rate in the reporting channel as the main parameters influencing the performance of cooperative sensing schemes. Next, the paper discusses the extension of the analysis to the case of mobile sensors, and determines the set of assumptions made in existing literature when taking into account mobility in sensing. The paper moves then to remove some of such assumptions, by presenting simulation results obtained in presence of realistic models for propagation in the considered area, as well as of a realistic mobility model. A comparison between theoretical derivation and simulation results shows that correlation among measurements taken by different sensors and the selected mobility model may significantly affect the sensing performance.

  • 286.
    Debernardi, Nicolas
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Jäger,, Markus
    Laneri, Jean-Christophe
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Sraj, Malek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Lungaro, Pietro
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Services Provisioning and Terminal Cooperation in User-Deployed Networks2006In: IEEE International Symposium on Personal, Indoor, and Mobile Radio Communications workshops, ISSN 2166-9570, E-ISSN 2166-9589Article in journal (Refereed)
    Abstract [en]

    Exploiting high-speed user-deployed Access Points (APs) in public infrastructures has been proposed as one of the candidate solutions for reducing the cost of future radio access. A disadvantage is that, due to lack of deployment coordination, these types of network are likely to provide only partial coverage. For this reason, the set of services that could be successfully provided in these networks might be rather limited. In this paper we present a novel framework for modeling non-interactive " infotainment" services with different degrees of "time criticality", and utilize it for investigating the user service perception in "spotty" coverage networks. In order to hide the infrastructure sparsity to the end users, the terminals are assumed equipped with software agents that can "opportunistically" pre-fetch information, on behalf of their users. This can be done when in contact with an AP, or, through a peer-to-peer file exchange with other terminal agents that have previously accessed the same information. In this paper, for different service types, the relationship between AP density and service perception is investigated. Furthermore, the impact of peer-to-peer terminal cooperation is evaluated in respect to both infrastructure requirements and content access delay. The results show that already with moderate AP densities, user-deployed networks deliver acceptable service perception, especially for services with low time criticality. Furthermore, whenever a "critical" mass of users shares common interests, the adoption of a peer-to-peer exchange strategy brings the significant gains of infrastructure reduction and/or improved service perception.

  • 287.
    Demirel, Burak
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Paderborn, Germany.
    Gupta, V.
    Quevedo, D. E.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On the Trade-Off between Communication and Control Cost in Event-Triggered Dead-Beat Control2016In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. PP, no 99, 7562376Article in journal (Refereed)
    Abstract [en]

    We consider a stochastic system where the communication between the controller and the actuator is triggered by a thresholdbased rule. The communication is performed across an unreliable link that stochastically erases transmitted packets. To decrease the communication burden, and as a partial protection against dropped packets, the controller sends a sequence of control commands to the actuator in each packet. These commands are stored in a buffer and applied sequentially until the next control packet arrives. In this context, we study dead-beat control laws and compute the expected linear-quadratic loss of the closed-loop system for any given event-threshold. Furthermore, we provide analytical expressions that quantify the trade-off between the communication cost and the control performance of event-triggered control systems. Numerical examples demonstrate the effectiveness of the proposed technique.

  • 288. Deng, Lei
    et al.
    Beltrán, Marta
    Pang, Xiaodan
    RISE ACREO AB.
    Zhang, Xu
    Arlunno, Valeria
    Zhao, Ying
    Caballero, Antonio
    Dogadaev, Anton
    Yu, Xianbin
    Llorente, Roberto
    Liu, Deming
    Tafur Monroy, I
    Fiber Wireless Transmission of 8.3-Gb/s/ch QPSK-OFDM Signals in 75–110-GHz Band2012In: Photonics Technology Letters, IEEE, Vol. 24, no 5, 383-385 p.Article in journal (Refereed)
  • 289. Deng, Lei
    et al.
    Liu, Deming
    Pang, Xiaodan
    RISE ACREO AB.
    Zhang, Xu
    Arlunno, Valeria
    Zhao, Ying
    Caballero, Antonio
    Dogadaev, Anton K
    Yu, Xianbin
    Monroy, Idelfonso Tafur
    Beltran, Marta
    Llorente, Roberto
    42.13 Gbit/S 16qam-OFDM Photonics-Wireless Transmission in 75-110 GHz Band2012In: Progress In Electromagnetics Research, Vol. 126, 449-461 p.Article in journal (Refereed)
  • 290. Deng, Lei
    et al.
    Pang, Xiaodan
    RISE ACREO AB.
    Monroy, Idelfonso Tafur
    Tang, Ming
    Shum, Ping
    Liu, Deming
    Experimental demonstration of nonlinearity and phase noise tolerant 16-QAM OFDM W-band (75–110 GHz) signal over fiber system2014In: Journal of Lightwave Technology, Vol. 32, no 8, 1442-1448 p.Article in journal (Refereed)
  • 291. Deng, Lei
    et al.
    Pang, Xiaodan
    RISE ACREO AB.
    Zhang, Xu
    Yu, Xianbin
    Liu, Deming
    Monroy, Idelfonso Tafur
    Nonlinearity and Phase Noise Tolerant 75-110 GHz Signal over Fiber System Using Phase Modulation Technique2013In: National Fiber Optic Engineers Conference, 2013Conference paper (Refereed)
  • 292. Deng, Lei
    et al.
    Pang, Xiaodan
    RISE ACREO AB.
    Zhao, Ying
    Othman, M Binti
    Jensen, Jesper Bevensee
    Zibar, Darko
    Yu, Xianbin
    Liu, Deming
    Monroy, Idelfonso Tafur
    2x2 MIMO-OFDM Gigabit fiber-wireless access system based on polarization division multiplexed WDM-PON2012In: Optics express, Vol. 20, no 4, 4369-4375 p.Article in journal (Refereed)
  • 293. Deng, Lei
    et al.
    Zhao, Ying
    Pang, Xiaodan
    RISE ACREO AB.
    Tang, Ming
    Shum, Ping
    Liu, Deming
    All-VCSEL Transmitters With Remote Optical Injection for WDM-OFDM-PON2014In: IEEE Photonics Technology Letters, Vol. 26, no 5, 461-464 p.Article in journal (Refereed)
  • 294. Deng, Lei
    et al.
    Zhao, Ying
    Pang, Xiaodan
    RISE ACREO AB.
    Yu, Xianbin
    Jensen, J Bevensee
    Liu, Deming
    Monroy, I Tafur
    Colorless ONU based on all-VCSEL sources with remote optical injection for WDM-PON2011In: Photonics Conference (PHO), 2011 IEEE, 2011, 220-221 p.Conference paper (Refereed)
  • 295. Deng, Lei
    et al.
    Zhao, Ying
    Pang, Xiaodan
    RISE ACREO AB.
    Yu, Xianbin
    Liu, Deming
    Monroy, Idelfonso Tafur
    Intra and inter-PON ONU to ONU virtual private networking using OFDMA in a ring topology2011In: Microwave Photonics, 2011 International Topical Meeting on & Microwave Photonics Conference, 2011 Asia-Pacific, MWP/APMP, 2011, 176-179 p.Conference paper (Refereed)
  • 296.
    Derakhshanno, Homayoun
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Voice over IP over GPRS2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Voice over IP (VoIP) technology has become prevalent today due to its lower cost than traditional telephony and its ability to support new value-added services. Additionally, the increasing availability of wireless internet access has led to research studies examining the combination of wireless network access with voice over IP. With the widespread availability of advanced mobile phones and Pocket PCs, the need for VoIP applications on these mobile platforms is tangible. To enable this, we need to evaluate the current wireless access technologies to see if they can support the necessary traffic and implement software to offer these VoIP services to users.

    In order to easily implement an IP-based service on GSM technology, we should use the GPRS service provided by the GSM operators. In this thesis, we evaluate Voice over IP service over GPRS in terms of feasibility and quality. Following this we ported a locally developed VoIP program to a Pocket PC (with GSM SIM-card support) which runs Microsoft’s Windows Mobile in order to provide suitable software as needed to offer the service from such a portable device.

  • 297. Devlic, Alisa
    Extending CPL with context ontology2006Conference paper (Refereed)
    Abstract [en]

    Communication has always been an essential part of peo-ple's everyday life. Nowadays most of people would liketo be reachable on multiple devices at anytime, anyplace. As a consequence, there has been a need to know and exploit a user's availability for communication (so called presence information), so that he/she can control incoming callsand make the decision to accept this call or not based onthe user's current context. The appearance and acceptanceof Session Initiation Protocol (SIP) as a signalling protocol for next generation networks has opened the door for multiple services, such as Voice over IP (VoIP), chat, games,instant messaging, and other innovative communication services. Built on top of existing data communication networks, this has enabled easy integration of voice and data services. In this paper we present an idea on how to use the context information to enhance the power of existing SIP call control services, to enable users to have greater control over their incoming/outgoing calls. These services are implemented using Call Processing Language (CPL), a language to describe and control Internet Telephony Services. They are extended with context parameters to permit context-based decision making based on context ontology. We want to show how easy is to add new context parameters to the CPL and how complex criteria can be built using our solution.

  • 298.
    Devlic, Alisa
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Mobile Service Laboratory (MS Lab).
    On Optimization of Quality of User Experience and Wireless Network Bandwidth in Video Content Delivery2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mobile video content today generates more than half of the mobile data traffic.The increasing popularity of mobile video on demand services poses great challenges to mobile operators and content providers. Frontmost, how to reduce the mobile video traffic load, while delivering high quality video content to mobile users without perceived quality degradations for the same (or cheaper) price? Battery lifetime represents another key factor of a user’s Quality of Experience(QoE). A lot of device energy is consumed by mobile network signalling and data transmission over new generation mobile communication systems. This thesis focuses on: (1) reducing the size of the video that is delivered to the enduser in the maximum achievable video quality, thus optimizing the wireless network bandwidth and the user-perceived QoE, and (2) reducing the energy consumption of a mobile device that is associated to data transfer over the radio interface, thus increasing the device’s battery lifetime. The main contributions have been given in providing the Over-the-Top video optimization and delivery schemes and recommendations on tuning their parameters in order to minimize the bandwidth and energy consumption of mobile video delivery, while maximizing the predictable user-perceived QoE. By preventing the video to be prefetched on low data rates and tuning the datarate threshold according to statistical properties of available data rates, we show that 20-70% of energy cost can be reduced by opportunistic prefetching, depending on the user’s pattern of available data rates. The data rate values ordered in time that have a large amount of serial correlation and low noise variance, or low average valueand high peak-to-mean ratio, are likely to yield the highest energy gains from content prefetching. Moreover, we show that energy gains are the largest when the threshold data rate is set close to an average data rate, due to the highest availability of data rates around this value, and for longer sleep time between the prefetching periods, which increases the probability of moving away from the areas with low data rates. Next, we focus on QoE-aware mobile video delivery solutions that are more bandwidth efficient without compromising the user-perceived video quality. They deliver a video over a varying data rate channel that is optimized for viewing on a mobile device in the highest perceptual video quality that can be achieved in the given video and network conditions. An optimized video consists of short segments in the minimum resolutions that satisfy the target perceptual video quality and have up to 60% reduced size compared to the video in the corresponding fixed video resolution, without perceptible quality difference. The delivery is performed by on demand download, context-aware prefetching, or in real time using the QoE-aware adaptive video streaming that runs over Dynamic Adaptive video Streaming over HTTP (DASH). By limiting the maximum bitrates of the requested video segments and using the remaining throughput to prefetch optimized video segments in advance of playout, we show that QoE-aware adaptive video streaming maintains a more stable perceptual video quality than DASH despite the fluctuations of the channel bandwidth, while using fewer number of bits, which improves a user-perceived QoE. The results of this thesis can help operators and content providers to reduce their costs and provide more content to their users at the same (or cheaper) price.

  • 299. Devlic, Alisa
    et al.
    Erik, Klintskog
    Context retrieval and distribution in a mobile distributed environment2007Conference paper (Refereed)
    Abstract [en]

    Context-aware services are gaining momentum in mobile computing. To enable rapid development of context-aware services,context information has to be retrieved from the environment, modeled,processed, and distributed to these services. MIDAS is a European research project concerning 3G and beyond, which aims to dene and implement a platform to simplify and speed up the task of developing and deploying mobile applications and services. MIDAS context engine provides mechanisms to retrieve, model, synthesize, and distribute context information in a distributed, mobile environment. This paper presents a way to retrieve and distribute context information using context queries and triggers. A novel approach to perform context synthesis will be presented using operators.

  • 300.
    Devlic, Alisa
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Graf, A.
    Barone, P.
    Evaluation of context distribution methods via Bluetooth and WLAN: Insights gained while examining Battery Power Consumption2008In: MobiQuitous 2008 - 5th International ICST Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services, 2008Conference paper (Refereed)
    Abstract [en]

    In a traditional context-aware system, most context information is local to a device. However, we may need access to context information from outside the device. Increasingly mobile electronic devices are equipped with Bluetooth and/or WLAN network interfaces. Both of these technologies enable ad hoc discovery & networking. In this paper we evaluate the use of these technologies for context distribution within a local area (i.e., limited to a single hop). Using Bluetooth, we begin by discovering devices using Bluetooth's discovery protocol, collect their context information, create an XML file containing this information, and distribute this file to all discovered devices, such that every device now has the same context information. Next we perform the same discovery, collect, and distribute functions, but using WLAN. In each case we have performed the cycle of operations starting with a fully charged battery and continuing until the device was not able to utilize the selected wireless interface any longer. Finally we compare both approaches to context distribution in terms of battery power consumption. We observe that Bluetooth consumes 2-6 times more energy for transmission of a 1MB file to two devices than to discover these two devices. Furthermore, the transfer of this file is two times slower than WLAN, and we must unicast this file to each device. Multicasting via WLAN proved to be less energy consuming than the Bluetooth transmission, if data is to be sent to more than three users. In addition, the energy to discover 2 devices along with their services using Bluetooth consumed 52 times more energy than to receive the same amount of data via a WLAN multicast. Thus, this paper shows that it is more energy efficient to distribute context knowledge to other devices, than having each device learn this information itself. Finally, we give equations for calculating the battery power consumption of transmitting data using any protocol that runs over Bluetooth or over WLAN.

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