Ändra sökning
Avgränsa sökresultatet
3456789 251 - 300 av 2284
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 251.
    Cambazoglu, Volkan
    Uppsala universitet, Avdelningen för datorteknik.
    Protocol, mobility and adversary models for the verification of security2016Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The increasing heterogeneity of communicating devices, ranging from resource constrained battery driven sensor nodes to multi-core processor computers, challenges protocol design. We examine security and privacy protocols with respect to exterior factors such as users, adversaries, and computing and communication resources; and also interior factors such as the operations, the interactions and the parameters of a protocol.

    Users and adversaries interact with security and privacy protocols, and even affect the outcome of the protocols. We propose user mobility and adversary models to examine how the location privacy of users is affected when they move relative to each other in specific patterns while adversaries with varying strengths try to identify the users based on their historical locations. The location privacy of the users are simulated with the support of the K-Anonymity protection mechanism, the Distortion-based metric, and our models of users' mobility patterns and adversaries' knowledge about users.

    Security and privacy protocols need to operate on various computing and communication resources. Some of these protocols can be adjusted for different situations by changing parameters. A common example is to use longer secret keys in encryption for stronger security. We experiment with the trade-off between the security and the performance of the Fiat–Shamir identification protocol. We pipeline the protocol to increase its utilisation as the communication delay outweighs the computation.

    A mathematical specification based on a formal method leads to a strong proof of security. We use three formal languages with their tool supports in order to model and verify the Secure Hierarchical In-Network Aggregation (SHIA) protocol for Wireless Sensor Networks (WSNs). The three formal languages specialise on cryptographic operations, distributed systems and mobile processes. Finding an appropriate level of abstraction to represent the essential features of the protocol in three formal languages was central.

  • 252.
    Cambazoglu, Volkan
    et al.
    Uppsala universitet, Datorarkitektur och datorkommunikation.
    Gutkovas, Ramunas
    Uppsala universitet, Datalogi.
    Åman Pohjola, Johannes
    Uppsala universitet, Datalogi.
    Victor, Björn
    Uppsala universitet, Datalogi.
    Modelling and analysing a WSN secure aggregation protocol: A comparison of languages and tool support2015Rapport (Övrigt vetenskapligt)
    Abstract [en]

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

  • 253.
    Cao, Le Phuong
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias J.
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Optimal transmit strategy for MIMO channels with joint sum and per-antenna power constraints2017Ingår i: 2017 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), IEEE, 2017, s. 3569-3573Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 254.
    Cao, Wei Qiu
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    A new Content Distribution Network architecture - PlentyCast2004Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Mediadistributionsnätverk har funnits några år. De har fått uppmärksamhet i både akademisk forskning och i industrin och kännetecknas av följande frågor: placering av innehållskopior, lokalisering av innehåll och routing, svärm intelligens, överlagrade nätverks självorganisering för denna typ av fördelade system. I denna rapport studeras en ny nätverksarkitektur för innehållsfördelning - PlentyCast. Denna studie fokuserar på tillgångslatens, nätverksskalbarhet, hög innehållstillgång, låg bandbreddskonsumtion, och förbättrad infrastrukturprestanda för Innehållsfördelningsnätverk.

  • 255.
    Cao, Yuan
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Zhao, Yongli
    Beijing Univ Posts & Telecommun, State Key Lab Informat Photon & Opt Commun, Beijing 100876, Peoples R China..
    Lin, Rui
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Yu, Xiaosong
    Beijing Univ Posts & Telecommun, State Key Lab Informat Photon & Opt Commun, Beijing 100876, Peoples R China..
    Zhang, Jie
    Beijing Univ Posts & Telecommun, State Key Lab Informat Photon & Opt Commun, Beijing 100876, Peoples R China..
    Chen, Jiajia
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Multi-tenant secret-key assignment over quantum key distribution networks2019Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 27, nr 3, s. 2544-2561Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Quantum key distribution (QKD) networks are promising to progress towards widespread practical deployment over existing fiber infrastructures in the near future. Given the high cost and difficulty of deploying QKD networks, multi-tenancy becomes promising to improve cost efficiency for future QKD networks. In a multi-tenant QKD network, multiple QKD tenants can sham the same QKD network infrastructure to obtain secret keys for securing their data transfer. Since the secret-key resources are finite and precious in QKD networks, how to achieve efficient multi-tenant secret-key assignment (MTKA) to satisfy the secret-key demands of multiple QKD tenants over QKD networks becomes a significant problem. In this regard, this study addresses the MTKA problem over QKD networks. A new multi-tenant QKD network architecture is proposed based on software defined networking (SDN) and quantum key pool (QKP) techniques. A secret-key rate sharing scheme is presented and a heuristic algorithm is designed to implement efficient MTKA over QKD networks. A new performance metric, namely matching degree (MD) that reflects the balance between QKD network secret-key resources and QKD tenant requests, is defined and evaluated. Simulation studies indicate that high QKD tenant requests accommodation and efficient secret-key resource usage can be achieved via maximizing the value of MD. 

  • 256.
    Carlsson, Daniel
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Dynamics AX in the Cloud: Possibilities and Shortcomings2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Användningen av molnet är snabbt expanderande och är något som är relevant för alla inblandade inom teknologin. Meningen med det här projektet är att undersöka fördelarna och de möjliga problem som kan uppstå genom användning av Microsoft Dynamics AX I molnet, specifikt Microsoft Azure, istället för lokala datacenter. Det här projektet har utförts hos Scania IT med hjälp av deras nuvarande implementation av Dynamics AX.

    Arbetet innehåller en omfattande litteraturstudie angående både ERP system och andra system från varierande områden med fokus på molnet. Det beslutades tidigt att fokusera på den nya versionen av Dynamics AX, som för tillfället bara är tillgänglig I molnet, och jämföra denna implementationen med de två versionen som huvudsakligen används idag, AX 2009 och AX 2012. Fördelarna med både AX och Azure som Microsoft produkter är tydliga med välintegrerade hjälpmedel hela vägen från klienterna till servrarna med ett särskilt fokus på säkerhetskopiering och lastbalansering. Det visas hur utvecklare behöver ändra sitt arbetssätt i avseende på integrationer med andra system, särskilt för AX 2009 då ramverken har ändrats. Tillägget av Data Entities betyder att utvecklare kan spara mycket tid på att bara behöva ha koll på en referens till platsen för ett objekt istället för att behöva veta exakt i vilken tabell i databasen objektet befinner sig.

    Analysen fokuserar på skillnaderna inom fyra olika områden, prestanda & tillgänglighet, skalbarhet, kostnadsbesparingar samt säkerhet & integritet. Kunskapen för analysen kommer framförallt ifrån litteraturstudien samt den kunskap som har intagits från implementationen samt medarbetarna vid Scania idag. Resultatet visar att det finns tydliga fördelar när det kommer till prestanda, kostnadsbesparingar och framför allt, tillgänglighet. Dock är det även tydligt att lagar i många länder ännu inte har hunnit ikapp det faktum att molnet är en av de bättre möjligheterna att spara data i idag. Detta betyder i sin tur betyder att det bästa nästa steget för majoriteten av ERP användarna idag är ett hybrid- eller privatmoln inom landsgränserna.

  • 257.
    Carlsson, Stefan
    et al.
    KTH, Tidigare Institutioner, Teleinformatik.
    Halén, Erik
    KTH, Tidigare Institutioner, Teleinformatik.
    Mobile Internet: Content Adaptation for Limited Devices2000Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

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

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

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

  • 258.
    Carrara, Elisabetta
    KTH, Tidigare Institutioner, Teleinformatik.
    Wireless Adaptation of a Security Management Protocol Suite1999Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

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

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

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

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

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

  • 259.
    Cavdar, Cicek
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Gera, Damini
    Airbus, Ottobrunn, Germany..
    Ghosh, Ayan
    BT, Bristol, Avon, England..
    Hofmann, Sandra
    Airbus, Ottobrunn, Germany..
    Nordlow, Anders
    Ericsson, Stockholm, Sweden..
    Schupke, Dominic
    Airbus, Ottobrunn, Germany..
    Demonstration of an Integrated 5G Network in an Aircraft Cabin Environment2018Ingår i: 2018 IEEE/AIAA 37TH DIGITAL AVIONICS SYSTEMS CONFERENCE (DASC), IEEE , 2018, s. 334-343Konferensbidrag (Refereegranskat)
    Abstract [en]

    The wireless communications finds many applications inside an aircraft cabin, in terms of Passenger and Crew Communications as well as Machine Type Communications (MTC). The aircraft cabin is a challenging environment and the different wireless technologies must be adequately tested and adapted to achieve maximum performance. In this regard, an aircraft environment has been analyzed in this paper for an in-cabin wireless system implementation and the measurement results have been further evaluated. This is an integrated system for the technologies of LTE, LAA and NB-IoT for the potential use-cases of Passenger Connectivity, On-Board Sensing, Cargo Tracking and Passenger Announcement. Results have then been summarized within the scope of this paper.

  • 260.
    Cavdar, Cicek
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Ruiz, M.
    Monti, Paolo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Velasco, L.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Design of green optical networks with signal quality guarantee2012Ingår i: IEEE International Conference on Communications, IEEE , 2012, s. 3025-3030Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 261. Cen, M.
    et al.
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Mégret, P.
    Moeyaert, V.
    Wuilpart, M.
    Fast and simple fault monitoring for long-reach passive optical networks2014Ingår i: 2014 European Conference on Optical Communication, (ECOC), IEEE , 2014, s. 6964070-Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 262.
    Chabouni (nee Talbi), Sami
    KTH, Tidigare Institutioner, Teleinformatik. KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Investigation and Prototyping of a web based manager in a GSM SIM Application Platform1998Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

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

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

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

  • 263.
    Champati, Jaya Prakash
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Al-Zubaidy, Hussein
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Gross, James
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    On the Distribution of AoI for the GI/GI/1/1 and GI/GI/1/2*Systems: Exact Expressions and Bounds2019Ingår i: IEEE CONFERENCE ON COMPUTER COMMUNICATIONS (IEEE INFOCOM 2019), IEEE , 2019, s. 37-45Konferensbidrag (Refereegranskat)
    Abstract [en]

    Since Age of Information (AoI) has been proposed as a metric that quantifies the freshness of information updates in a communication system, there has been a constant effort in understanding and optimizing different statistics of the AoI process for classical queueing systems. In addition to classical queuing systems, more recently, systems with no queue or a unit capacity queue storing the latest packet have been gaining importance as storing and transmitting older packets do not reduce AoI at the receiver. Following this line of research, we study the distribution of AoI for the GI/GI/1/1 and GI/GI/1/2* systems, under non-preemptive scheduling. For any single-source-single-server queueing system, we derive, using sample path analysis, a fundamental result that characterizes the AoI violation probability, and use it to obtain closed-form expressions for D/GI/1/1, M/GI/1/1 as well as systems that use zero-wait policy. Further, when exact results are not tractable, we present a simple methodology for obtaining upper bounds for the violation probability for both GI/GI/1/1 and GI/GI/1/2* systems. An interesting feature of the proposed upper bounds is that, if the departure rate is given, they overestimate the violation probability by at most a value that decreases with the arrival rate. Thus, given the departure rate and for a fixed average service, the bounds are tighter at higher utilization.

  • 264.
    Chang, Peiliang
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Area Spectral and Energy Efficiency Analysis of Cellular Networks with Cell DTX2015Ingår i: IEEE Globecom 2015 , San Diego, December 6th-10th, 2015, IEEE conference proceedings, 2015, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 265.
    Chang, Peiliang
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Energy and Spectral Efficiency of Cellular Networks with Discontinuous Transmission2017Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, nr 5, s. 2991-3002Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 266. Chaporkar, P.
    et al.
    Proutière, Alexandre
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Optimal distributed scheduling in wireless networks under SINR interference model2013Ingår i: 2013 51st Annual Allerton Conference on Communication, Control, and Computing, Allerton 2013, IEEE conference proceedings, 2013, s. 1372-1379Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 267.
    Charalambous, Themistoklis
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Kalyviannaki, Evangelia
    City University London.
    Hadjicostis, Christoforos N.
    Electrical and Computer Engineering Department, University of Cyprus.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Distributed Offline Load Balancing in MapReduce Networks2013Ingår i: 2013 IEEE 52ND ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC), IEEE conference proceedings, 2013, s. 835-840Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 268.
    Charalambous, Themistoklis
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Krikidis, I.
    Medium access control via contention-based distributed power control2012Ingår i: 2012 8th International Wireless Communications And Mobile Computing Conference (IWCMC), IEEE , 2012, s. 555-560Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 269.
    Chareonvisal, Tanakorn
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    ImplementingDistributed Storage System by Network Coding in Presence of Link Failure2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

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

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

  • 270.
    Charvandeh, Jenny
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Location aware web access2009Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Tillgång till information varsomhelst och vilken tid som helst är en viktig utkom av modern rörliga kommunikations systems.

    Alltmera har användarens terminal kännedom om användarens plats. Informationen om platsen kan vara lite eller omfattande. Tillgång till information om platsen gör det möjligt att skapa platsmedvetna tjänster.

    I den här master thesis presenterar och utvärderar jag ett system för plats medvetna web användning. Användaren klickar på en punkt på en karta (för att inrätta en virtuell lokalisering genom att använda tidigare installerat applikationer), sedan deras HTTP GET request för en URL utvidgas med information om användarens position eller deras virtuella (verkliga) lokalisering. En platsmedveten web query har skapats så att information om plats som latitude och longitude läggs till denna web query. Sedan en web server använder denna information för att generera dynamiska web sidor.

  • 271.
    Chatterjee, Saikat
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Hari, K. V. S.
    Händel, Peter
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Projection-based atom selection in orthogonal matching pursuit for compressive sensing2012Ingår i: 2012 National Conference on Communications, NCC 2012, IEEE , 2012, s. 6176797-Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 272.
    Chatzaras, Anargyros
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Savvidis, Georgios
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Seamless speaker recognition2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I ett teknologiskt avancerat samhälle så hanterar den genomsnittliga personen dussintals konton för e-post, sociala nätverk, internetbanker, och andra elektroniska tjänster. Allt eftersom antalet konton ökar, blir behovet av automatisk identifiering av användaren mer väsentlig. Biometri har länge använts för att identifiera personer och är den vanligaste (om inte den enda) metoden för att utföra denna uppgift.

    Smartphones har under de senaste åren blivit allt mer vanligt förekommande, de ger användaren tillgång till de flesta av sina konton och, i viss mån, även personifiering av enheterna baserat på deras profiler på sociala nätverk. Dessa enheter har inbyggda mikrofoner och används ofta av en enskild användare eller en liten grupp av användare, till exempel ett par eller en familj. Denna avhandling använder mikrofonen i en smartphone för att spela in användarens tal och identifiera honom/henne. Befintliga lösningar för talarigenkänning ber vanligtvis användaren om att ge långa röstprover för att kunna ge korrekta resultat.  Detta resulterar i en dålig användarupplevelse och avskräcker användare som inte har tålamod att gå igenom en sådan process. Huvudtanken bakom den strategi för talarigenkänningen som presenteras i denna avhandling är att ge en sömlös användarupplevelse där inspelningen av användarens röst sker i bakgrunden.

    En Android-applikation har utvecklats som, utan att märkas, samlar in röstprover och utför talarigenkänning på dessa utan att kräva omfattande interaktion av användaren. Två varianter av verktyget har utvecklats och dessa beskrivs ingående i denna avhandling. Öpen source-ramverket Recognito används för att utföra talarigenkänningen. Analysen av Recognito visade att det inte klarar av att uppnå tillräckligt hög noggrannhet, speciellt när röstproverna innehåller bakgrundsbrus. Dessutom visade jämförelsen mellan de två arkitekturerna att de inte skiljer sig nämnvärt i fråga om prestanda.

  • 273.
    Chatzidrossos, Ilias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Maximizing streaming quality in heterogeneous overlays through incentives2009Ingår i: Proceedings of the 2009 ACM Conference on Emerging Networking Experiments and Technologies, CoNEXT'09 - Co-located Student Workshop, CoNext Student Workshop '09, 2009, s. 35-36Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 274. Chatzigiannakis, I.
    et al.
    Strikos, Andreas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    A decentralized intrusion detection system for increasing security of wireless sensor networks2007Ingår i: ETFA 2007: 12th IEEE International Conference on Emerging Technologies and Factory Automation, IEEE , 2007, s. 1408-1411Konferensbidrag (Refereegranskat)
    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.

  • 275.
    Chazalet, Boris
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Opportunistic Content Delivery utilizing Optimized Context Dissemination via the Service Interface in Ambient Networks2007Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    En av Ambient Network viktigast egenskap är användning av kontext information. Kontext i ett Ambient Network omfattar alla sorts information som beskriver nuvarande situation av alla entiten som är kopplad med nätverket (T.ex. lokalisering, tillgängliga konnectivitet och anordningarna osv.). Sådana kontext information kan används av olika applikationer, tjänster eller nätverks resurser, möjligör de kan automatiskt ändrar deras beteende utan användares ingripande. Därför, kontext i Ambient Network ger användaren en bättre upplevelse genom automatiskt konfiguration, uppgörelse och tjänst framförande och transport.

    Detta exjobb presenterar ett optimerad version av kontext utbyt protocolen. Denna protocol är en del av kontext-medveten arkitekture för Ambient Network. Design och arkitekture av den Distributed Context EXchange Protocol (DCXP) använder en P2P överdrag på UDP. Denna design och arkitekture har reviderats för real tids kontext utspridning, samtidigt avsätta flaskhals. En undersökning av denna reviderad design inklusiv mätningar i verkliga scenario, undersökning visar att DXCP erbjuder en praktiskt infall på kontext igenkänning och utspridning, tillåter snabb kontext utbyt och spontan anvädning av nya kontext källor när de blir (inte) tillgängliga i dynamiskt omställning av nätverks konnektivitet, underlätta användning av Ambient Network teknologi. Slutligen, detta exjobb presenterar och demostrerar en ny användning och fördelar med optimerad kontext utspridning som Ambient Networks tjänst gränssnitt (ASI) för läglig kontext leverans. Det är uppnått genom att tillägga en utökning av ASI API, som möjligör en kontext leverans proxy som interagerar med DXCP, och möjligör kontext leverans över Ambient Network.

  • 276.
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Efficient resiliency mechanisms for next generation passive optical networks2013Ingår i: ICICS 2013 - Conference Guide of the 9th International Conference on Information, Communications and Signal Processing, IEEE Computer Society, 2013, s. 6782903-Konferensbidrag (Refereegranskat)
    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.

  • 277.
    Chen, Jiajia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Mahloo, Mozhgan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Reducing the Impact of Failures in Next Generation Optical Access Networks2012Ingår i: 2012 Asia Communications And Photonics Conference (ACP), 2012, s. AS1D.2-Konferensbidrag (Refereegranskat)
    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.

  • 278.
    Chen, Jiajia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Urban, Patryk J.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Fast fault monitoring technique for reliable WDM PON: Achieving significant operational saving2013Ingår i: 2013 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference, OFC/NFOEC 2013, IEEE , 2013, s. 6532499-Konferensbidrag (Refereegranskat)
    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.

  • 279.
    Chen, Lisan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Schiller Shi, Tingting
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Targeted News in an Intranet2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Microsoft har i SharePoint 2013 förbättrat användarnas personliga sidor (My Site) genom att sammankoppla dem i ett socialt nätverk. I förbättringen har ett personligt nyhetsflöde som visar händelser som användaren följer tillagts. Denna rapport avser att undersöka möjligheten att utöka det personliga nyhetsflödet med att lägga till en oberoende komponent i My Site. Komponenten ska tillåta användarna att prenumerera på företagsnyheter genom att välja bland olika nyhetskategorier.

    En prototyp av komponenten implementerades och resultatet uppfyllde de flesta kraven som ställdes i början av arbetet. Komponenten har lagts till i användarens My Site som en webb del och hämtar automatiskt de senaste företagsnyheterna som matchar användarens prenumeration. Den utvecklade prototypen kan förbättras både i funktion och design, men har uppfyllt behovet för denna rapport som avser att undersöka möjligheten att utöka det personliga nyhetsflödet i My Site med en sådan komponent.

    Eftersom projektmedlemmarna saknade förkunskaper i SharePoint och .NET utveckling innebar projektet nya utmaningar. Studenterna lärde sig att arbeta i SharePoint miljö samt i Microsoft Visual Studio för .NET utveckling.

  • 280.
    Chen, Qiao
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    Valerio, G.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    Dispersion analysis of polar glide symmetry with coaxial rings2018Ingår i: IET Conference Publications, Institution of Engineering and Technology , 2018, nr CP741Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article, the dispersion properties of a coaxial transmission line with polar glide-symmetric rings are analyzed. This symmetry is obtained by introducing periodic polar rings on either the inner or outer conductor of a coaxial guide. By modifying the relative radii of both rings, we demonstrate that a zero bandgap with non-zero group velocity at the Brillouin zone boundary can be achieved. Such quasi-linear dispersion is analyzed by applying both a circuit-based method and full-wave simulations. A good agreement is achieved between the methods.

  • 281.
    Chen, Ta-wei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Optimization of Transport Security for Securing Peer-to-Peer Communication in Heterogeneous Networks2005Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Denna uppsats behandlar säkerheten för morgondagens "peer-to-peer" (P2P) realtidskommunikation i heterogena nät. På grund av den adderade fördröjning som orsakas av inbandssignalering och dålig kompabilitet hos många transportprotokoll, så kan man fastställa att existerande säkerhetsprotokoll, såsom "(Datagram) Transport Layer Security" (TLS och DTLS), inte är lämpade för denna typ av kommunikation och att ett nytt säkerhetsprotokoll bör tas fram. "Transport Encapsulation Security Payload" (TESP) är ett sådant protokoll. TESP har inte bara fördelar såsom låg uppstartsfördröjning, utan har också stöd för många transportprotokoll, t.ex. "Transport Control Protocol" (TCP), "User Datagram Protocol" (UDP), "Stream Control Transmission Protocol" (SCTP) och "Datagram Congestion Control Protocol" (DCCP). Även en säkerhetsanalys av TESP har gjorts, där inga säkerhetsproblem har kunnat påvisas.

  • 282.
    Chen, Xu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Performance Analysis of Wireless Multiplayer Games on Terraplay Systems2005Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Denna avhandling är sponsrad av Terraplay System AB. Terraplay System är en trådlös multiplayer-spelservice i Sverige. Syftet med detta projekt var att ge ett lättillgängligt och gratis testverktyg för fördröjning kallat Terraplay Test Toolkit (TTK) till spelutvecklare som använder Terraplays plattform. Eftersom trådlösa multispel är känsliga för fördröjning, är det nödvändigt för spelutvecklare att innan de börjar göra en uppskattning av denna. TTK är baserat på Java Mobile Edition-teknologi (J2me), och kan utföra ett fördröjningstest i realtid, kallat Round Trip Time (RTT). Detta projekt undersökte tillämpningen av den mobila utvecklingen. Mobil utveckling är ett helt nytt fält och blir mer och mer populärt. Designprocessen och källkoden kan användas som referenser för mobila utvecklare. Baserat på Terraplay Test Toolkit gjordes en serie experiment för att testa TTK:s förmåga. Dessa experiment fokuserade på fördröjda effekter av trådlösa multiplayerspel under olika situationer så som olika paketstorlek, olika leveranshastigheter, höghastighetsrörelser och så vidare. Även fast TTK inte är ett professionellt testverktyg, och inte kan användas för exakta fördröjningsanalyser, återger det ändå fördröjningens variationer under olika villkor. Dessa experiment visade att trådlösa multiplayerspel anpassade till Terraplay, med genomsnittlig paketstorlek (300 bite) INTE är en faktor med avseende på fördröjningen till Terraplay System; paketets hastighet kan påverka paketets fördröjning. I en miljö med hög rörelsehastighet, ökar inte påtagligt spelets fördröjning. Användandet av HTTP kan orsaka en tre gånger så lång fördröjning, jämfört med att bara använda TCP. Slutsatserna är baserade på experimentresultaten. Dessa slutsatser kan hjälpa utvecklare av trådlösa multiplayerspel[.]

  • 283.
    Chen, Zhaofei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Yavuz, Emre A.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Demo of a collaborative music sharing system2012Ingår i: MobiOpp'12 - Proceedings of the 3rd ACM International Workshop on Mobile Opportunistic Networks, New york: ACM , 2012, s. 77-78Konferensbidrag (Refereegranskat)
    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.

  • 284.
    Chen, Zhaofei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Yavuz, Emre Altug
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    What a juke! A collaborative music sharing system2012Ingår i: 2012 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks, WoWMoM 2012 - Digital Proceedings, IEEE , 2012, s. 6263751-Konferensbidrag (Refereegranskat)
    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.

  • 285.
    Cheng, Yuxin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Optical Interconnects for Next Generation Data Centers: Architecture Design and Resource Allocation2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The current data center architectures based on blade servers and elec- tronic packet switches face several problems, e.g., limited resource utilization, high power consumption and cost, when handling the rapidly growing of data traffic. Optical networks offering ultra-high capacity and requiring low energy consumption are considered as a good option to address these problems. This thesis presents new data center architectures based on optical interconnects and transmissions, and evaluates performance by extensive simulations.

    The first main contribution of the thesis is to introduce a passive optical top-of-rack interconnect (POTORI) architecture. The data plane of POTORI mainly consists of passive components to interconnect the servers within the rack. Using the passive components makes it possible to significantly reduce power consumption while achieving high reliability in a cost-efficient way. In addition, the POTORI’s control plane is based on a centralized controller, which is responsible for coordinating the communications among the servers in the rack. A cycle-based medium access control (MAC) protocol and a dy- namic bandwidth allocation (DBA) algorithm are designed for the POTORI to efficiently manage the exchange of control messages and the data transmis- sion 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.

    The second main contribution of the thesis is to investigate rack-scale disaggregated data center (DDC) architecture for improving resource utiliza- tion. In contrast to the traditional DC with blade servers that integrate various types of resources (e.g., central processing unit (CPU), memory) in a chassis, the rack-scale DDC contains fully decoupled resources held on differ- ent blades, referred to as resource blades. The resource blades are required to be interconnected within the rack by an ultra-high bandwidth optical in- terconnect through the optical interfaces (OIs). A resource allocation (RA) algorithm is proposed to efficiently schedule the resources in the DDC for virtual machine requests. Results show that with sufficient bandwidth on the OIs, the rack-scale DDC with the proposed RA algorithm can achieve 20% higher resource utilization and make 30% more revenue comparing to the traditional DC.

  • 286.
    Cheng, Yuxin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Passive Optical Top-of-Rack Interconnect for Data Center Networks2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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. 

  • 287.
    Cheng, Yuxin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Fiorani, Matteo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Reliable and Cost Efficient Passive Optical Interconnects for Data Centers2015Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, nr 11, s. 1913-1916Artikel i tidskrift (Refereegranskat)
    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.

  • 288.
    Cheng, Zhuo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Hybrid Power Control in Time Division Scheduling Wideband Code Division Multiplex Access2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Med den höga datahastighet som Enhanced Uplink (EUL) medger kan en konventionell algoritm för effektkontroll baserad på signal to interference ratio (SIR) leda till effekthöjning beroende på självinterferens eller felaktigt SIR mål. Time division (TD) schedulering vid Wideband Code Division Multiple Access (WCDMA) anses vara en nyckelfunktion för att uppnå höga datahastigheter. I övergången mellan aktiv och inaktiv transmissionstidsintervall vid time division multiplexing (TDM) har effektoscillering/effektpeak observerats. Detta gör det nödvändigt att se över algoritmerna för effektkontroll vid olika scenarion av TD schedulering.

    Målet med effektkontrollen i denna studie är att minimera rise over thermal noise (RoT) för en given datahastighet givet begränsningen att kvaliteten på physical layer control channel är tillräcklig (beaktande att dedicated physical control channel (DPCCH) SIR inte understiger 3dB med en sannolikhet på som mest 5%). Ett annat mål är att minimera den lokala effektoscillationen (effektpeakar) som kan inträffa till exempel vid övergång mellan aktiv och inaktiv transmissionstidsintervall.

    De undersökta hybrida metoderna för effektkontroll är: (1) icke-parametrisk Generalized rake receiver SIR (GSIR) Inner Loop Power Control (ILPC) vid aktiv transmissionstidsintervall + Received Signal Code Power (RSCP) ILPC vid inaktiv transmissionstidsintervall och (2) RSCP ILPC under aktiv transmissionstidsintervall + GSIR ILPC under inaktiv transmissiontidsintervall. Båda metoderna jämförs med ren GSIR och ren RSCP ILPC.

    Länk nivå simulering med flera användare anslutna till en enda cell visar att:

    • Problemet med effektpeakar observeras tydligt vid GSIR + GSIR transmit power control (TPC) men generellt sett presterar den bra i alla studerade TD scenarion. GSIR presterar bättre än andra TPC metoder beträffande RoT, speciellt i TU kanal modellen. Detta beror på att metoden är bra på att motverka momentant förändrad fading och med god precision estimerar SIR. Bland alla presenterade TPC metoder är GSIR + GSIR TPC den bästa på att behålla en god kvalitet på DPCCH kanalen. Ingen effekthöjning har observerats vid GSIR + GSIR TPC.
    • RSCP + RSCP eliminerar problemet med effektpeakar och presterar bättre än andra TPC metoder presenterade under 3GPPs Pedestrial A (pedA) 3km/h kanal beträffande RoT. Dock är metoden generellt sett sämre på att behålla kontrollkanalens kvalitet än GSIR + GSIR TPC.
    • GSIR + GSIR ILPC eliminerar problemet med effektpeakar och presterar bättre än GSIR power control i ett scenario med 2 och 4 TDM high data rate (HDR) UE och 2 TDM HDR UE tillsammans med 4 Code Division Multiplex (CDM) LDR UE i pedA 3km/h kanalen beträffande RoT. Dock kan inte kvaliteten på kontrollkanalen behållas i detta fall heller under inaktiv transmissionstidsintervall.
    • Det är inte rekommenderat att använda RSCP + GSIR TPC eftersom den presterar sämst av alla TPC metoder beträffande RoT i de allra flesta fall. Till dess fördel är att den är den näst bästa på att behålla kvaliteten på kontrollkanalen. Effektpeakar har observerats när RSCP + GSIR TPC använts.

    För att behålla kontrollkanalens kvalitet används alltid en minimum SIR nivå ovanpå alla föreslagna TPC metoder. När det finns flera anslutna TDM HDR UEs i cellen indikerar resultaten att det är en utmaning att behålla kvalitetskraven på kontrollkanalen. På grund av detta kan det bli nödvändigt att begränsa antalet anslutna terminaler i en cell i ett TD scenario.

  • 289.
    Chengegowda, Venkatesh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Analysis of Queues for Interactive Voice and Video Response Systems: Two Party Video Calls2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Videosamtal på mobila enheter är popularisera med tillkomsten av 3G. Den förbättrade nätkapacitet så tillgänglig möjliggör överföring av videodata över Internet. Det har prognos av flera VOIP serviceorganisationer att de nuvarande IVR-system kommer att utvecklas till röst och video Response (IVVR) System. Dock har denna utveckling många tekniska utmaningar på vägen. Arkitekturer för att genomföra kösystem för videodata och standarder för bland konvertering av videodata mellan format som stöds för uppringande är två av dessa utmaningar. Denna avhandling är en analys av köer och media kodkonvertering för IVVRs.

    En stor insats i detta arbete innebär att bygga en prototyp IVVR kösystem. Systemet är konstruerat med hjälp av en öppen källkod-server som heter Asterisk och MySQL-databas. Asterisk är en SIP-baserad Public Exchange Server (PBX) och även en utvecklingsmiljö för VOIP-baserade IVRs. Funktionella scenarier för SIP session etablering och motsvarande sessionen inställningar för den föreslagna kö modell mäts. Resultaten indikerar att prototypen tjänar som en tillräcklig modell för en kö, även om en betydande fördröjning införs för sessionsupprättandebegäran. Arbetet omfattar även analys av integrering DiaStar™ är en SIP-baserad media kodkonvertering motor till denna kö. Emellertid är detta system inte helt att fungera med DiaStar för media translation. The studie avslutas med ett omnämnande av de områden för framtida arbete med detta system och det allmänna tillståndet i IVVR kö-system i branschen.

  • 290.
    Chia, Yeow-Khiang
    et al.
    Institute for Infocomm Research, Singapore.
    Kittichokechai, Kittipong
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    On secure source coding with side information at the encoder2013Ingår i: 2013 IEEE International Symposium on Information Theory Proceedings (ISIT), IEEE, 2013, s. 2204-2208Konferensbidrag (Refereegranskat)
    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.

  • 291. Chiaraviglio, L.
    et al.
    Lorincz, J.
    Monti, Paolo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Towards sustainable and reliable networks with LIFETEL2015Ingår i: Proceedings - IEEE INFOCOM, IEEE conference proceedings, 2015, s. 39-40Konferensbidrag (Refereegranskat)
    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.

  • 292.
    Chiaraviglio, Luca
    et al.
    Univ Roma Tor Vergata, EE Dept, Rome, Italy.;Consorzio Nazl Interuniv Telecomunicaz, Pisa, Italy..
    Amorosi, Lavinia
    Consorzio Nazl Interuniv Telecomunicaz, Pisa, Italy..
    Blefari-Melazzi, Nicola
    Univ Roma Tor Vergata, EE Dept, Rome, Italy.;Consorzio Nazl Interuniv Telecomunicaz, Pisa, Italy..
    Dell'Olmo, Paolo
    Univ Rome Sapienza, DSS Dept, Rome, Italy..
    Natalino, Carlos
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Optimal Design of 5G Networks in Rural Zones with UAVs, Optical Rings, Solar Panels and Batteries2018Ingår i: 2018 20TH ANNIVERSARY INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON) / [ed] Jaworski, M Marciniak, M, Institute of Electrical and Electronics Engineers (IEEE), 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    We focus on the problem of designing a 5G network architecture to provide coverage in rural areas. The proposed architecture is composed of 5G Base Stations carried by Unmanned Aerial Vehicles (UAVs), and supported by ground sites interconnected through optical fiber links. We also consider the dimensioning of each site in terms of the number of Solar Panels (SPs) and batteries. We then formulate the problem of cost minimization of the aforementioned architecture, by considering: i) the cost for installing the sites, ii) the costs for installing the SPs and the batteries in each site, iii) the costs for installing the optical fiber links between the installed sites, and iv) the scheduling of the UAVs to serve the rural areas. Our results, obtained over a representative scenario, reveal that the proposed solution is effective in limiting the total costs, while being able to ensure the coverage over the rural areas.

  • 293.
    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?2013Ingår i: 2013 21st IEEE International Conference on Network Protocols (ICNP), IEEE Computer Society, 2013, artikel-id 6733584Konferensbidrag (Refereegranskat)
    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.

  • 294.
    Chiesa, Marco
    et al.
    Roma Tre University, Italy.
    Cittadini, L.
    Di Battista, G.
    Vissicchio, S.
    Local transit policies and the complexity of BGP Stability Testing2011Ingår i: INFOCOM, 2011 Proceedings IEEE, Institute of Electrical and Electronics Engineers (IEEE), 2011, s. 2957-2965, artikel-id 5935136Konferensbidrag (Refereegranskat)
    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.

  • 295.
    Chiesa, Marco
    et al.
    Université catholique du Louvain, Belgium.
    Demmler, D.
    Canini, M.
    Schapira, M.
    Schneider, T.
    Towards securing internet eXchange points against curious onlooKers2016Ingår i: ANRW 2016 - Proceedings of the ACM, IRTF and ISOC Applied Networking Research Workshop, Association for Computing Machinery (ACM), 2016, s. 32-34Konferensbidrag (Refereegranskat)
    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.

  • 296.
    Chiesa, Marco
    et al.
    Roma Tre University, Italy.
    Di Battista, G.
    Erlebach, T.
    Patrignani, M.
    Computational complexity of traffic hijacking under BGP and S-BGP2012Ingår i: Automata, Languages, and Programming: 39th International Colloquium, ICALP 2012, Warwick, UK, July 9-13, 2012, Proceedings, Part II, Springer, 2012, Vol. 7392, nr PART 2, s. 476-487Konferensbidrag (Refereegranskat)
    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.

  • 297.
    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-BGP2015Ingår i: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 600, s. 143-154Artikel i tidskrift (Refereegranskat)
    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.

  • 298.
    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 Points2017Ingår i: Proceedings of the IM 2017 - 2017 IFIP/IEEE International Symposium on Integrated Network and Service Management, Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 435-441, artikel-id 7987309Konferensbidrag (Refereegranskat)
    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.

  • 299.
    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 capabilities2016Ingår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 54, nr 10, s. 102-108, artikel-id 7588277Artikel i tidskrift (Refereegranskat)
    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.

  • 300.
    Chiesa, Marco
    et al.
    Roma Tre University, Italy.
    Kindler, G.
    Schapira, M.
    Traffic engineering with Equal-Cost-Multipath: An algorithmic perspective2014Ingår i: INFOCOM, 2014 Proceedings IEEE, Institute of Electrical and Electronics Engineers (IEEE), 2014, s. 1590-1598, artikel-id 6848095Konferensbidrag (Refereegranskat)
    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.

3456789 251 - 300 av 2284
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf