Ändra sökning
Avgränsa sökresultatet
45678910 301 - 350 av 2591
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.
  • 301.
    Brännström, Fredrik
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Grant, Alex J.
    University of South Australia.
    Optimal scheduling for multiple serially concatenated codes2003Ingår i: 3rd International Symposium on Turbo Codes & Related Topics, 2003, s. 383-386Konferensbidrag (Refereegranskat)
  • 302.
    Bubenko, Janis, Jr.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Annotations of First Generation Systems Development in Sweden2009Ingår i: / [ed] Impagliazzo J; Jarvi T; Paju P, 2009, Vol. 303, s. 95-105Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work presents episodes of first generation information systems development in Sweden using two particular computers, ALWAC IIIE, during the period 1957-1961, and Univac III during 1963-1964. The ALWAC IIIE at ADB Institute, Gothenburg, was used for technical as well as for administrative applications. Another episode concerns re-engineering of an inventory management application; it used the ALWAC IIIE for the Swedish Defence Material Administration in 1960. The next episode concerns the computer Univac III. A sales contract between Gotaverken AB and Univac included a guarantee by Univac to transfer one of Gotaverken's punched card routines to a magnetic tape oriented routine on Univac III. The development work was carried out on a Univac III at Kantonalbank in Bern, Switzerland. They did the work in night shifts during a period of five months. Only one Univac III was installed in Sweden.

  • 303.
    Bubenko, Janis, Jr.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Information Processing - Administrative Data Processing The First Courses at KTH and SU, 1966-672009Ingår i: / [ed] Impagliazzo J; Jarvi T; Paju P, 2009, Vol. 303, s. 138-148Konferensbidrag (Refereegranskat)
    Abstract [en]

    A three semester, 60-credit course package in the topic of Administrative Data Processing (ADP), offered in 1966 at Stockholm University (SU) and the Royal Institute of Technology (KTH) is described. The package had an information systems engineering orientation. The first semester focused on datalogical topics, while the second semester focused on the infological topics. The third semester aimed to deepen the students' knowledge in different parts of ADP and at writing a bachelor thesis. The concluding section of this paper discusses various aspects of the department's first course effort. The course package led to a concretisation of our discipline and gave our discipline an identity. Our education seemed modern, "just in time", and well adapted to practical needs. The course package formed the first concrete activity of a group of young teachers and researchers. In a forty-year perspective, these people have further developed the department and the topic to an internationally well-reputed body of knowledge and research. The department has produced more than thirty professors and more than one hundred doctoral degrees.

  • 304.
    Bui, Minh N.
    et al.
    Concordia University.
    Jaumard, Brigitte
    Concordia University.
    Cavdar, Cicek
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Mukherjee, Biswanath
    University of California - Davis.
    Design of a survivable VPN topology over a service provider network2013Ingår i: 2013 9th International Conference on the Design of Reliable Communication Networks (DRCN), IEEE conference proceedings, 2013, s. 71-78Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 305.
    Butussi, Matteo
    et al.
    Dipartimento di Ingegneria dell’Informazione University of Padua.
    Bengtsson, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Low Complexity Admission in Downlink Beamforming2006Ingår i: International Conference on Acoustics, Speech and Signal Processing, 2006. ICASSP 2006, 2006, Vol. 4, s. IV261-IV264Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study the downlink of a system with multiple antennas at the base stations and propose two different schemes for admission control and beamforming selection when a new user enters the system. To keep the complexity low, only the power control, not the spatial signatures of beamformers for the already admitted users, are adjusted. Numerical examples illustrate the performance compared to joint optimization of all users

  • 306. Buysse, Jens
    et al.
    Cavdar, Cicek
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    De Leenheer, M.
    Dhoedt, B.
    Develder, Chris
    Improving energy efficiency in optical cloud networks by exploiting anycast routing2011Ingår i: ACP. Asia Communications and Photonics Conference and Exhibition, 2011, IEEE conference proceedings, 2011, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    Exploiting anycast routing significantly reduces optical network and server energy usage. In this work we present a case study showing that intelligently selecting destinations and routes thereto, while switching off unused (network) elements, cuts power consumption by around 20% and saves network resources by 29%.

  • 307. Callegati, F.
    et al.
    Aracil, J.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Andriolli, N.
    Careglio, D.
    Giorgetti, A.
    Fdez-Palacios, J.
    Gauger, C.
    Klinkowski, M.
    de Dios, O. G.
    Hu, E. K. G.
    Matera, F.
    Overby, H.
    Raffaelli, C.
    Rea, L.
    Sengezer, N.
    Tornatore, M.
    Vlachos, K.
    Research on Optical Core Networks in the e-Photon/ONe Network of Excellence2006Ingår i: 25TH IEEE INTERNATIONAL CONFERENCE ON COMPUTER COMMUNICATIONS, VOLS 1-7, PROCEEDINGS IEEE INFOCOM 2006, 2006, s. 2987-2991Konferensbidrag (Refereegranskat)
    Abstract [en]

    This papers reports the advances in optical core networks research coordinated in the framework of the e- photon/ONe and e-photon/ONe+ networks of excellence.

  • 308. Callegati, F.
    et al.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Tornatore, M.
    Cugini, F.
    Research in Optical Transport Networks: The e-Photon/ONe+ Experience2007Ingår i: ICTON 2007: Proceedings of the 9th International Conference on Transparent Optical Networks, Vol 1 / [ed] Marciniak, M, 2007, Vol. 1, s. 3-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper reports the view of the e-Photon/ONe community regarding the research directions in optical transport networks. Results stemming from joint international research activities in the framework of the project are summarized. This summary presents, necessarily, little details, but wants to draw the attention of the reader towards the most advanced research activities ongoing on the broad topics of optical core networks, from wavelength routed network, to optical burst switching and optical packet switching.

  • 309.
    Campostrini, Matteo
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    The Social Shaping of European Digital Radio2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This study examines the social shaping of digital radio in Europe and provides new insights about the main competing technologies and the discourses built around their capabilities.

    The radio frequency spectrum is a limited resource and in order to be used in the most efficient way different organizations have been researching optimizing standards since the mid-1980s. The Eureka-147 project produced the first European digital broadcasting standard DAB whose development have been initially fostered by public service broadcasters and electronics manufacturers, consequently by commercial broadcasters and governmental institutions.

    The design and policy of DAB did not manage to grasp the attention and support of all the actors present in the nascent digital radio industry. A decade after its launch DAB was followed by other digital radio standards, as DAB+ and DRM, in the role of complements/competitors. At the same time the Internet started to be used as infrastructure for delivering radio or sound entertainment content.

    Thirty years after the beginning of the European digital radio experience, the picture is still complex and no technology achieved a complete and harmonized implementation. Across Europe, countries have been involved in the digitalization of radio to different extent: Norway announced FM transmissions shutdown in 2017, UK and Switzerland have developed an almost nationally wide digital network coverage and are about to run their switchover plans, some other countries as Sweden and Italy are still in a transmission-trial and evaluation phase.

    The history of digital radio in Europe offers ground for a Social Shaping of Technology analysis as exposed in “The Social construction of technological systems” (1987) by Wiebe Bijker, Thomas Hughes and Trevor Pinch. The Social Shaping of Technology claims that technologies and their outcomes are always socially negotiated. According to this theoretical framework and in particular to the Social Construction of Technology (SCOT) methodology, it is possible to highlight a number of social groups negotiating the final technology in the development of every artefact. In particular SCOT allows to find points of interpretative flexibility, namely diverging interpretations that different groups have of a same technology or a particular feature of it. These arguments or discourses are built around a technology or its features in order to foster a particular concerns of the corresponding group.

    This master thesis analyses the development of digital radio in Europe according to the framework provided by the Social Shaping of Technology, enriching the number of case studies that have been conducted following this framework. In this way the dissertation “The Social Shaping of European Digital Radio” provides an overview on the social, political and economic forces which negotiated the technology throughout its development and provides a deeper understanding of the overall digital media technology industry. 

  • 310. Capdevila, S.
    et al.
    Masud, Muhammad Mubeen
    KTH, Skolan för elektro- och systemteknik (EES).
    Serrano, R.
    Aguasca, A.
    Blanch, S.
    Romeu, J.
    Ch. Bolomey, J.
    Jofre, L.
    RFID based probes for EM-field measurements2009Ingår i: European Conference on Antennas and Propagation, EuCAP 2009, Proceedings, IEEE , 2009, s. 2787-2790Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper the use of RFID for EM field measurement is studied. A novel RFID antenna with high tuning capabilities is presented and measured, and it is used in combination with several RFID IC to measure the EM field along the H-plane of a horn antenna. A calibration procedure for the non-linear effects in RFID IC is introduced and used to correct the measured fields.

  • 311. Carlsson, N.
    et al.
    Dán, György
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Mahanti, A.
    Arlitt, M.
    A longitudinal characterization of local and global BitTorrent workload dynamics2012Ingår i: 13th International Conference on Passive and Active Measurement (PAM), 2012, Springer Berlin/Heidelberg, 2012, Vol. 7192 LNCS, s. 252-262Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 312.
    Carlsson, Niklas
    et al.
    Linkoping University.
    Dán, György
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Eager, Derek
    University of Saskatchewan .
    Mahanti, Anirban
    NICTA.
    Tradeoffs in cloud and peer-assisted content delivery systems2012Ingår i: 2012 IEEE 12th International Conference on Peer-to-Peer Computing, P2P 2012, IEEE , 2012, s. 249-260Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 313.
    Carrara, Elisabetta
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Security for IP multimedia applications over heterogeneous networks2005Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Personal mobile multimedia services are rapidly become popular. They leverage the combination of mobile and Internet-based communications, the increased capabilities of the third generation of mobile communications (3G), and the flexibility of a common transport and service platform.

    Cost and quality are critical factors for the success of IP multimedia services. 3G is based on hetereogeneous networks, characterized by a mixture of wired and wireless links with very different requirements on the communication itself. Furthermore, the "always best connected" paradigm requires the design of the new applications to accomodate different types of access. It turns out that the cellular link is typically the most constrained, e.g. in terms of limited bandwidth and high delay, especially when IP is used as transport.

    Security is an important aspect of the service. Never before has this awareness been more present, not only among technicians, but also among users. Users want the possibility to protect themselves and their data and private matters, in a way that no one else can interfere and that private communications are guaranteed to remain private. The use of the Internet as a common transport backbone, a notoriously open and adverse environment, and in general the use of the IP technology, which is receiving a bad (media) reputation in terms of the security breaches it opens, calls for an end-to-end security solution for IP multimedia services. There are also scenarios where end-to-end protection of other information is an absolute must, for example public safety communication, catastrophe and emergency communication, corporate, or government communication.

    This research addresses the design of a security solution for IP multimedia, striving in particular for the promotion of end-to-end security on a large scale. This research builds on the concept of a "transport-friendly" security solution: security always comes at a cost, hence it is important to control its impact on services, otherwise security is generally sacrificed.

    This research focused on the protection of the media traffic. It first identified the requirements that arise from IP multimedia applications in hetereogeneous networks, examined existing security solutions, and concluded that they did not fullfil the requirements raised by 3G environments. This has motivated the design of two new security protocols that are transport-friend to meet the identified requirements, so as to have a low impact on services. These two protocols have then been integrated to provide a security solution for IP multimedia in hetereogeneous networks. The research leading to this licentiate has been mostly conducted in the IETF (a standardisation body), and its results were also adopted byothers, e.g. 3GPP services.

  • 314. Casetti, C.
    et al.
    Cesana, M.
    Filippini, I.
    Dán, György
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Marsh, I.
    Context-aware information dissemination in vehicular networks2011Ingår i: EURO-NGI Conf. Next Gener. Internet Networks, NGI - Proc., 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 315. Casini, Enrico
    et al.
    Gallinaro, Gennaro
    Grotz, Joel
    SES ASTRA, Chateau de Betzdorf, L-6815 Betzdorf, Luxembourg.
    Reduced Front-End Reception Requirements for Satellite Broadcast using Interference Processing2008Ingår i: IEEE Transactions on Consumer Electronics, ISSN 0098-3063, Vol. 54, nr 4, s. 1555-1563Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of fixed satellite broadcast reception is considered. The possibility of reducing the requirements on the antenna front-end dimensions is investigated. Interference processing and mitigation techniques are employed to cope with the increased level of adjacent system interference at the satellite broadcast receiver resulting from the less directive antenna. A novel satellite reception front-end antenna based on a multiple input receiver is proposed to adapt the interference processing methods to the broadcast reception scenario. The potential performance of the devised scheme is thoroughly discussed and assessed by extensive software simulations.

  • 316.
    Cavarec, Baptiste
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Bengtsson, Mats
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    CHANNEL DEPENDENT CODEBOOK DESIGN IN SPATIAL MODULATION2018Ingår i: 2018 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING (ICASSP), IEEE, 2018, s. 6413-6417Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present a modulation design based on Spatial Modulation for the uplink in IoT applications. The proposed modulation design uses a Tabu search based deterministic heuristic to adapt the modulation link based on channel information fed back by the receiver. Our approach allows adaptivity to rate and energy constraints. We numerically validate the proposed method on a scenario with full channel state information available at the transceiver, showing clear performance gains compared to simpler heuristics and channel independent codebook designs.

  • 317.
    Cavdar, Cicek
    et al.
    Istanbul Technical University.
    Buzluca, F.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Energy-Efficient Design of Survivable WDM Networks with Shared Backup2010Ingår i: Global Telecommunications Conference (GLOBECOM 2010), 2010 IEEE, 2010, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    In recent years, energy-efficient design of optical WDM networks has become increasingly important as efforts to reduce the operational expenditure (Opex) and the carbon footprint of the internet are prioritized. In this paper we focus on energy- efficient survivable network design where backup resources are shared for efficient capacity consumption. However there is a trade-off between energy-efficiency and survivability. Survivable network design strategies lead to lightly loaded links in order to minimize the risk in case of a failure and to increase the shareability of backup resources. On the contrary, energy-efficient network design strategies tend to increase the load in a set of links as a consequence of concentrating the traffic in order to be able to switch off as much network resources as possible. In this study, we present a novel method to simultaneously minimize Capex and Opex while providing an energy-efficient, shared backup protected network, under the assumption of backup capacity in sleep mode. For the first time we propose an ILP formulation for the energy-efficient shared backup protection problem. By exploiting the sleep mode for the backup resources, we observe that the ILP solution of our mathematical model brings up to 40% gain in energy efficiency in comparison to energy-unaware shared backup protection approach.

  • 318.
    Celebi, Hasan Basri
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Pitarokoilis, Antonios
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Skoglund, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Training-Assisted Channel Estimation for Low-Complexity Squared-Envelope Receivers2018Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC, Institute of Electrical and Electronics Engineers Inc. , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Squared-envelope receivers, also known as energy detectors, are, due to their simplified circuitry, low-cost and low-complexity receivers. Hence they are attractive implementation structures for future Internet-of-Things (IoT) applications. Even though there is considerable work on the wider research area of squared-envelope receivers, a comprehensive comparison and statistical characterization of training-assisted channel estimators for squared-envelope receivers appear to be absent from the literature. A detailed description of practical channel estimation schemes is necessary for the optimal training design of latency-constrained IoT applications. In this paper, various channel estimators are derived, their bias and variance are studied, and their performance is numerically compared against the Cramer-Rao lower bound.

  • 319.
    Cerutti, Isabella
    et al.
    Scuola Superiore Sant'Anna.
    Fumagalli, Andrea
    The University of Texas at Dallas.
    Hui, Rongqing
    The University of Kansas.
    Monti, Paolo
    The University of Texas at Dallas.
    Paradisi, Alberto
    CPqD.
    Tacca, Marco
    The University of Texas at Dallas.
    Plug and Play Networking with Optical Nodes2006Ingår i: ICTON 2006: 8th International Conference on Transparent Optical Networks, Vol 3, Proceedings / [ed] Marciniak, M, 2006, Vol. 3, s. 133-138Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Plug and play optical (PPO) nodes may be used to facilitate the deployment of optical networks. PPO nodes must be able to learn about the signal propagation properties of the surrounding optical fibers and make their wavelength routing decisions based on the collected data. This paper discusses what are the open challenges that must be overcome to provide cost effective and performing ad hoc networking solutions based on PPO nodes.

  • 320.
    Cerutti, Isabella
    et al.
    Scuola Superiore Sant'Anna.
    Fumagalli, Andrea
    The University of Texas at Dallas.
    Hui, Rongqing
    The University of Kansas.
    Monti, Paolo
    The University of Texas at Dallas, United States.
    Paradisi, Alberto
    CPqD.
    Tacca, Marco
    The University of Texas at Dallas, United States.
    Plug and play optical nodes: network functionalities and built-in fiber characterization techniques2007Ingår i: Journal of Optical Networking, ISSN 1536-5379, Vol. 6, nr 6, s. 642-653Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    \textlessp\textgreater\textlessa href$=$"http://www.osa-jon.org/virtual_issue.cfm?vid$=$26"\textgreaterFeature Issue on Photonics in Switching\textless/a\textgreater\textless/p\textgreaterPlug and play optical (PPO) nodes may be used to facilitate the deployment of optical networks. PPO nodes must be able to learn about the signal propagation properties of the surrounding optical fibers and make their wavelength-routing decisions based on the collected data. We discuss what are the open challenges that must be overcome to provide optical networking solutions based on cost-effective PPO nodes. Three possible PPO node hardware architectures with trade-offs in complexity, cost, and functionality are presented along with their built-in fiber characterization techniques.

  • 321.
    Chacinski, Marek
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Berggren, Jesper
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Kjebon, Olle
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Hammar, Mattias
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Sundgren, Petrus
    Marcks von Würtemberg, Rikard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    1.3 um InGaAs VCSELs: Influence of the Large Gain-Cavity Detuning on the Modulation and Static Performance2004Ingår i: Proc. of 30th European Conference on Optical Communication 2004, 2004Konferensbidrag (Refereegranskat)
  • 322.
    Chacinski, Marek
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Isaksson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    D'Oosterlinck, W.
    Morthier, G.
    Widely Tunable Wavelength Conversion 10 Gb/s Using a Modulated Grating Y-branch Laser Integrated with an Optical Amplifier2007Ingår i: OFC/NFOEC 2007 - Optical Fiber Communication and the National Fiber Optic Engineers Conference 2007, 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    A simple integrated tunable wavelength converter is presented. 10 Gb/s XGM conversion of signals at wavelength 1530-1560 nm to 1531-1556 nm and transmission at 2.5 Gb/s over 25 km SSMF of the converted signals were achieved.

  • 323.
    Chacinski, Marek
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Westergren, Urban
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Stoltz, Björn
    Syntune AB, Kista, Sweden .
    Driad, Rachid
    Makon, Robert Elvis
    Hurm, Volker
    Rosenzweig, Josef
    Li, Jie
    Steffan, Andreas Gerhard
    Transceiver modules utilizing travelling-wave electro-absorption modulator2010Ingår i: 2010 Conference on Optical Fiber Communication, Collocated National Fiber Optic Engineers Conference, OFC/NFOEC 2010, 2010, s. 5465732-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Electro-Absorption-Transceiver (EAT) structures used as efficient Travelling-Wave Electro-Absorption-Modulator (TWEAM) as well as Travelling-Wave-Photo-Detector (TWPD) are investigated. Clear eye-openings at 100Gb/s for operation as modulator and/or as detector, as well as 80Gb/s transmission between a pair of EATs, are presented.

  • 324. Chang, C. -C
    et al.
    Arafa, Shadi
    KTH.
    Muftic, S.
    Key establishment protocol for wireless sensor networks2007Ingår i: 2007 IEEE Internatonal Conference on Mobile Adhoc and Sensor Systems, MASS, IEEE , 2007, s. 4428701-Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes the design, prototype implementation and deployment of a key management protocol for sensor networks. In order to exchange protected messages between sensor nodes in a wireless sensor network, secret shared cryptographic keys must be established between the nodes of the network. Several key management schemes have been proposed in the literature, but these schemes are not suitable for real-life deployment. In this paper, we approach the problems of key management protocol differently from other reported results. We first analyzed functionality, feasibility and flexibility of the current key management protocols. Then, we introduce the concept of the Trusted Base Station as the foundation of our new protocol. The results of our implementation and deployment in a real WSN environment show that our theoretical results and claims are supported by the results of practical tests and measurements of operational efficiency.

  • 325.
    Chang, Peiliang
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Cross-Layer Energy-Efficient Mobile Network Design2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    För att säkerställa en hållbar utveckling av framtidens mobilnät är det avgörande att förbättra energieffektiviteten i dem. Denna avhandling ägnas därför åt utformningen av energieffektiva mobilnät. En designmetod över lagren antas, där resurshanteringen i MAC-lagret, nätverkslagret samt servicelagret optimeras för att förbättra energieffektiviteten. Problemet att optimera MAC-lagrets resursallokering i nedlänk i NOMA-system med flera bärare för att maximera systemets energieffektivitet samtidigt som användarnas QoS-krav uppfylls betraktas först. Den optimala effektfördelningen över delbärare och över användare som delar en delbärare föreslås. Genom att utnyttja lösningsstrukturen för den optimala effektallokeringen mellan användare som delar en delbärare, utvecklas en suboptimal lösning för delbärartilldelning, vilket gynnsamt minimerar den behövda effekten för att serva alla användare med erforderlig QoS. Förutom att optimera kanaltilldelningen och effektfördelningen i en enda cell, studeras även länkschemaläggningen i ett flercellsscenario för att hantera mellancellsstörningar. En skalbar och distribuerad lösning för länkschemaläggning föreslås för att orkestrera sändning och DTX-mikrosömn av flera basstationer så att både mellancellsstörningar och energiförbrukning minskas. I nätverkslagret optimeras driften av basstationens sovande för att förbättra mobilnätets energieffektivitet utan att för den delen försämra användarnas QoS. Spektral- och energieffektiviteten i mobilnät där basstationer är aktiverade med DTX studeras först under olika trafikbelastningar. Det visar sig att när nätverksbelastningen ökar, så minskar länkspektraleffektiviteten medan nätverksspektraleffektiviteten ökar. När det gäller nätverksenergieffektiviteten så kommer den antingen att först öka och sedan minska, eller alltid öka i takt med att nätverksbelastningen ökar. Den optimala nätverksbelastningen för att maximera nätverksenergieffektiviteten beror på effektförbrukningen hos basstationer i DTX-viloläge. Baserat på resultaten från ovanstående studie undersöks sedan den kombinerade optimeringen av cell-DTX och djupsömn för att maximera nätverksenergieffektiviteten. En skalningslag för sändningseffekt föreslås som säkerställer att fördelningen av den mottagna effekten förblir oförändrad när fler basstationer kopplas om till djupsömn. Genomsnittliga resursutnyttjandet och överbelastningssannolikheten för basstationer som ej är i djupsömnläge härleds också. Baserat på dessa resultat erhålls ett möjligt intervall på andelen basstationer i djupsömnläge. Slutligen härleds den optimala andelen basstationer i djupsömnläge för att maximera nätverksenergieffektiviteten samtidigt som användarnas QoS-krav uppfylls. Till sist optimeras resurstilldelningen i tjänstelagret för kantnodsberäkning (eng. edge computing), i syfte att förbättra energieffektiviteten i mobilnäten. Vi studerar avvägningen mellan servicefördröjning och energiförbrukning i beräknings- och kommunikationsdelsystemen, och visar att belastningen i delsystemen bör balanseras. Att öka resurserna hos det högt belastade delsystemet kan avsevärt minska resurserna för andra delsystem. En algoritm föreslås för att ta reda på den optimala beräkningshastigheten och optimala antalet aktiva basstationer som minimerar den totala energiförbrukningen samtidigt som kraven på genomsnittlig servicefördröjning säkerställs.

  • 326.
    Chang, Peiliang
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Interference-aware Distributed Control of Cell Discontinuous Transmission2018Ingår i: 2018 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE (WCNC), IEEE , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    As a main enabler for the next generation (5G) cellular networks, network densification faces challenges in intercell interference and energy consumption. Cell discontinuous transmission (DTX) can be employed to reduce both energy consumption of base stations (BSs) and inter-cell interference. In this paper we study the control problem of cell DTX in dense small cell networks (DSCNs). We firstly formulate the network energy efficiency optimization problem. Then a centralized heuristic DTX control algorithm is presented. In order to address the issues of complexity and scalability of the centralized solution, an interference-aware distributed DTX control algorithm is proposed. Discussions on algorithm complexity and implementation are provided. The proposed algorithms are evaluated with numerical simulations. Results show that at high load region, the proposed algorithms can not only enhance network capacity by reducing inter-cell interference by up to 60% but also increase network energy efficiency by switching BSs into micro-sleep mode by 67%.

  • 327.
    Charalambous, Themistoklis
    et al.
    Aalto Univ, Dept Elect Engn & Automat, Espoo, Finland..
    Kim, Su Min
    Korea Polytech Univ, Dept Elect Engn, Shihung, South Korea..
    Nomikos, Nikolaos
    Univ Aegean, Dept Informat & Commun Syst Engn, Samos, Greece..
    Bengtsson, Mats
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Johansson, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Relay-pair selection in buffer-aided successive opportunistic relaying using a multi-antenna source2019Ingår i: Ad hoc networks, ISSN 1570-8705, E-ISSN 1570-8713, Vol. 84, s. 29-41Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study a cooperative network with a buffer-aided multi-antenna source, multiple half-duplex (HD) buffer-aided relays and a single destination. Such a setup could represent a cellular downlink scenario, in which the source can be a more powerful wireless device with a buffer and multiple antennas, while a set of intermediate less powerful devices are used as relays to reach the destination. The main target is to recover the multiplexing loss of the network by having the source and a relay to simultaneously transmit their information to another relay and the destination, respectively. Successive transmissions in such a cooperative network, however, cause inter-relay interference (IRI). First, by assuming global channel state information (CSI), we show that the detrimental effect of IRI can be alleviated by precoding at the source, mitigating or even fully cancelling the interference. A cooperative relaying policy is proposed that employs a joint precoding design and relay-pair selection. Note that both fixed rate and adaptive rate transmissions can be considered. For the case when channel state information is only available at the receiver side (CSIR), we propose a relay selection policy that employs a phase alignment technique to reduce the IRI. The performance of the two proposed relay pair selection policies are evaluated and compared with other state-of-the-art relaying schemes in terms of outage and throughput. The results show that the use of a powerful source can provide considerable performance improvements.

  • 328.
    Charalambous, Themistoklis
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Nomikos, Nikolaos
    Krikidis, Ioannis
    Vouyioukas, Demosthenes
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Modeling Buffer-Aided Relay Selection in Networks With Direct Transmission Capability2015Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 19, nr 4, s. 649-652Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider a wireless relay network that consists of a source, half-duplex decode-and-forward buffer-aided relays and a destination. While the majority of previous works on relay selection assume no direct transmission between source and destination in such a setting, we lift this assumption and propose a link selection policy that exploits both the buffering ability and the opportunity for successful reception of a packet directly from the source. The proposed relay selection scheme incorporates the instantaneous strength of the wireless links and adapts the relay selection decision based on the strongest available link. The evolution of the network as a whole is modeled by means of a Markov chain and thus, the outage probability is associated with the steady state of the Markov chain. It is deduced that even if the link between the source and the destination is in principle a very unreliable link, it is always beneficial for the source to multicast a packet to both the relay with the strongest available link and the destination.

  • 329.
    Chatterjee, Saikat
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Sundman, Dennis
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Hybrid greedy pursuit2011Ingår i: 19th European Signal Processing Conference (EUSIPCO 2011), 2011, s. 343-347Konferensbidrag (Refereegranskat)
    Abstract [en]

    For constructing the support set of a sparse vector in the standardcompressive sensing framework, we develop a hybridgreedy pursuit algorithm that combines the advantages ofserial and parallel atom selection strategies. In an iterativeframework, the hybrid algorithm uses a joint sparsity informationextracted from the independent use of serial and parallelgreedy pursuit algorithms. Through experimental evaluations,the hybrid algorithm is shown to provide a significantimprovement for the support set recovery performance.

  • 330.
    Chatzidrossos, Ilias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Live Streaming Performance of Peer-to-Peer Systems2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In peer-to-peer (P2P) live streaming systems peers organize themselves in an overlay and contributewith their resources to help diffuse live content to all peers in a timely manner. The performanceof such systems is usually characterized by the delay-loss curve, which quantifies theplayback delay required for achieving a certain streaming quality, expressed as the chunk missingratio at the peers. The streaming quality is determined by the overlay construction algorithm, theforwarding algorithm, the loss process in the underlying network, the number of peers in the overlayand their bandwidth distribution, the willingness of the peers to contribute with their resourcesand the viewing behavior of the peers (churn). The overlay construction and forwarding algorithmsare inherent characteristics of a P2P protocol, while the remaining factors are artifacts of thedeployment of the P2P system over a best-effort network such as the Internet, as well as the factthat peers act as independent agents. The current thesis addresses the problem of evaluating andimproving the performance of P2P streaming protocols based on models of the network and of thepeers' behavior. The first part of the thesis is devoted to the performance evaluation of P2P overlay constructionand forwarding algorithms and offers three contributions. First, we study the efficiency of datadistribution in multiple tree-based overlays employing forward error correction. We deriveanalytical expressions for the average packet possession probability as well as its asymptoticbounds and verify our results through simulations. Second, we evaluate the performance of astreaming system in the presence of free-riders. We define two admission control policies and studythe streaming feasibility using an analytical model and via simulations. Third, we present ananalytic framework for the evaluation of forwarding algorithms in mesh-based systems. We validate itvia simulations and use it to evaluate and to compare four push-based forwarding algorithms in termsof their delay-loss curves. The second part of the thesis investigates potential improvements to the operation of P2P streamingsystems and offers three contributions in that area. First, we study the impact of selfish peerbehavior on streaming quality in overlays where a fraction of peers has limited contribution due tophysical constraints. We show that selfish peer behavior results in suboptimal streaming quality andwe propose an incentive mechanism that increases the streaming quality by using the server uploadcapacity to reward high contributing peers. Second, we study the problem of building network aware P2P streaming overlays, taking into accountrecent measurement results that indicate that the AS-level topology of the Internet is flattening.Through extensive simulations on regular and measured topologies we show that it is possible tocreate better than random overlays relying on information about the underlying topology. Finally, westudy the problem of playout adaptation in P2P streaming systems under churn. We propose andevaluate two algorithms that tune the playback delay of the peers in such a way that the streamingquality of the peers is maintained within predetermined limits. We use simulations to show thecorrectness of the proposed algorithms and the benefits from their use.

  • 331.
    Chatzidrossos, Ilias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    P2P Live Video Streaming2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The ever increasing demand for video content directed the focus of researchfrom traditional server-based schemes to peer-to-peer systems for videodelivery. In such systems, video data is delivered to the users by utilizing theresources of the users themselves, leading to a potentially scalable solution.Users connect to each other, forming a p2p overlay network on top of theInternet and exchange the video segments among themselves. The performanceof a p2p system is characterized by its capability to deliver the videocontent to all peers without errors and with the smallest possible delay. Thisconstitutes a challenge since peers dynamically join and leave the overlay andalso contribute different amounts of resources to the system.The contribution of this thesis lies in two areas. The first area is theperformance evaluation of the most prominent p2p streaming architectures.We study the streaming quality in multiple-tree-based systems. We derivemodels to evaluate the stability of a multiple tree overlay in dynamic scenariosand the efficiency of the data distribution over the multiple trees. Then, westudy the data propagation in mesh-based overlays. We develop a generalframework for the evaluation of forwarding algorithms in such overlays anduse this framework to evaluate the performance of four different algorithms.The second area of the thesis is a study of streaming in heterogeneous p2poverlays. The streaming quality depends on the aggregate resources that peerscontribute to the system: low average contribution leads to low streamingquality. Therefore, maintaining high streaming quality requires mechanismsthat either prohibit non-contributing peers or encourage contribution. In thisthesis we investigate both approaches. For the former, we derive a model tocapture the evolution of available capacity in an overlay and propose simpleadmission control mechanisms to avoid capacity drainage. For the latter, inour last work, we propose a novel incentive mechanism that maximizes thestreaming quality in an overlay by encouraging highly contributing peers tooffer more of their resources.

  • 332.
    Chatzidrossos, Ilias
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Dán, György
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Playout Adaptation in Peer-to-Peer Systems Under Churn2012Ingår i: 2012 19th International Packet Video Workshop, PV 2012, IEEE , 2012, s. 119-124Konferensbidrag (Refereegranskat)
    Abstract [en]

    We address the problem of playout adaptation in peer-to-peer streaming systems. We propose two algorithms for playout adaptation: one coordinated and one distributed. The algorithms dynamically adapt the playback delay of the peers so that the playout miss ratio is maintained within a predefined interval. We validate the algorithms and evaluate their performance through simulations under various churn models. We show that playout adaptation is essential in peer-to-peer systems when the system size changes. At the same time, our results show that distributed adaptation performs well only if the peers in the overlay have similar playback delays. Thus, some form of coordination among the peers is necessary for distributed playout adaptation in peer-to-peer streaming systems.

  • 333.
    Chatzidrossos, Ilias
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Dán, György
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Fodor, Viktória
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Delay and playout probability trade-off in mesh-based peer-to-peer streaming with delayed buffer map updates2009Ingår i: Peer-to-Peer Networking and Applications, ISSN 1936-6442, E-ISSN 1936-6450, Vol. 3, nr 3, s. 208-221Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In mesh-based peer-to-peer streaming systemsdata is distributed among the peers according tolocal scheduling decisions. The local decisions affecthow packets get distributed in the mesh, the probabilityof duplicates and consequently, the probabilityof timely data delivery. In this paper we proposean analytic framework that allows the evaluation ofscheduling algorithms. We consider four solutions inwhich scheduling is performed at the forwarding peer,based on the knowledge of the playout buffer contentat the neighbors. We evaluate the effectiveness of thesolutions in terms of the probability that a peer can playout a packet versus the playback delay, the sensitivityof the solutions to the accuracy of the knowledge of theneighbors’ playout buffer contents, and the scalabilityof the solutions with respect to the size of the overlay.We also show how the model can be used to evaluatethe effects of node arrivals and departures on the overlay’sperformance.

  • 334.
    Chatzidrossos, Ilias
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Dán, György
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Fodor, Viktória
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Server Guaranteed Cap: an incentive mechanism for maximizing streaming quality in heterogeneous overlays2010Ingår i: NETWORKING 2010, PROCEEDINGS / [ed] Crovella M; Feeney LM; Rubenstein D; Raghavan SV, 2010, s. 315-326Konferensbidrag (Refereegranskat)
    Abstract [en]

    We address the problem of maximizing the social welfare in a peer-to-peel streaming overlay given a fixed amount of server upload capacity. We show that peers' selfish behavior leads to an equilibrium that is suboptimal in terms of social welfare, because selfish peers are interested in forming clusters and exchanging data among themselves In order to increase the social welfare we propose a novel incentive mechanism: Server Guaranteed Cap (SGC), that uses the server capacity as an incentive for high contributing peers to upload to low contributing ones We prove that SGC is individually rational anti incentive compatible We also show that under very general conditions, there exists exactly one server capacity allocation that maximizes the social welfare under SGC, hence simple gradient based method can be used to find the optimal allocation

  • 335.
    Chatzidrossos, Ilias
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Dán, György
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Legout, Arnaud
    INRIA, FRANCE.
    Small-world Streaming: Network-aware Streaming Overlay Construction Policies for a Flat Internet2011Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Recent measurements indicate that the peering agreements betweenAutonomous Systems (AS) are flattening the AS level topology of theInternet. The transition to a more flat AS topology opens up for newpossibilities for proximity-aware peer-to-peer overlay construction. Inthis paper we consider the problem of the construction of overlays  forlive peer-to-peer streaming  that leverage peering connections tothe maximum extent possible, and investigate how a limited number ofoverlay connections over transit links should be chosen such as tomaximize the streaming performance. We define a set of transit overlaylink establishment policies that leverage topological characteristics ofthe AS graph. We evaluate their performance over regular AS topologiesusing extensive simulations, and show that the performance difference between the policies can be up to an order of magnitude. Thus, it is possible to maximize the system performance by leveraging the characteristics of the AS graph. Based on our results we also argue that the average loss probability is not an adequate measure of the performance of proximity-aware overlays.  We confirm our findings via simulations over a graph of the peering AS topology of over 600 ASs obtained from a large measurement data set.

  • 336.
    Chatzidrossos, Ilias
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    Fodor, Viktória
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    On the effect of free-riders in P2P streaming systems2008Ingår i: 2008 4TH INTERNATIONAL TELECOMMUNICATION NETWORKING WORKSHOP ON QOS IN MULTISERVICE IP NETWORKS, 2008, s. 8-13Konferensbidrag (Refereegranskat)
    Abstract [en]

    Peer-to-peer applications exploit the users willingness to contribute with their upload transmission capacity, achieving this way a scalable system where the available transmission capacity increases with the number of participating users. Since not all the users can offer upload capacity with high bitrate and reliability, it is of interest to see how these non-contributing users can be supported by a peer-to-peer application. In this paper we investigate how free-riders, that is, non-contributing users can be served in a peer-to-peer streaming system. We consider different policies of dealing with free-riders and discuss how performance parameters such as blocking and disconnection of free-riders are influenced by these policies, the overlay structure and system parameters as overlay size and source upload capacity. The results show that while the multiple-tree structure may affect the performance free-riders receive, the utilization of the transmission resources is still comparable to that of an optimized overlay.

  • 337.
    Chatzinotas, Symeon
    et al.
    SnT - securityandtrust.lu, University of Luxembourg.
    Christopoulos, Dimitrios
    SnT - securityandtrust.lu, University of Luxembourg.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Coordinated Multi-Point Decoding with Dual-polarized Antennas2011Ingår i: IWCMC 2011 - 7th International Wireless Communications and Mobile Computing Conference 2011, 2011, s. 157-161Konferensbidrag (Refereegranskat)
    Abstract [en]

    Coordinated multi-point processing has shown greatpotential for cellular networks, while MIMO is the key to nextgeneration wireless communications. However, full exploitationof MIMO technology demands high antenna separation at thetransceivers. This paper investigates the use of dual polarizedantennas as a mean to overcome hardware size limitations.Uplink sum rate capacity of a multicell joint processing (MJP)system employing dual polarized antennas is evaluated throughtheoretical analysis and verified by numerical simulations andtheoretical analysis. The system model incorporates uniformlydistributed users, path loss and Rayleigh fading, extendingWyner’s model. Optimal and MMSE receiver architectures arecompared in terms of capacity and complexity. System capacityis calculated as cell size or cross polar discrimination (XPD)varies. The results support the use of dual-polar decoding for lowXPD, dense cellular systems while per polarization processing isacceptable in high XPD, sparse systems.

  • 338.
    Chatzinotas, Symeon
    et al.
    SnT - securityandtrust.lu, University of Luxembourg.
    Imran, Muhammad Ali
    Centre for Communication Systems Research, University of Surrey, UK.
    Hoshyar, Reza
    Centre for Communication Systems Research, University of Surrey, UK.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Multicell LMMSE Filtering Capacity under Correlated Multiple BS Antennas2010Ingår i: Proceedings IEEE Vehicular Technology Conference, Fall, IEEE , 2010, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    Multicell joint processing has been shown to efficiently suppress inter-cell interference, while providing a high capacity gain due to spatial multiplexing across distributed Base Stations (BSs). However, the complexity of the optimal joint decoder in the multicell uplink channel grows exponentially with the number of users, making it prohibitive to implement in practice. In this direction, this paper investigates the uplink capacity performance of multicell joint linear minimum mean square error (LMMSE) filtering, followed by single-user decoding. The considered cellular multiple-access channel model assumes both Rayleigh and Rician flat fading, path loss, distributed users and correlated multiple antennas at the base station side. The case of Rayleigh fading is tackled using a free probability approach, while the case of Rician fading is addressed through a deterministic equivalent calculated using non-linear programming techniques. In this context, it is shown that LMMSE can provide high spectral efficiencies in practical macrocellular scenarios.

  • 339.
    Chatzinotas, Symeon
    et al.
    SnT - securityandtrust.lu, University of Luxembourg.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Clustered Multicell Joint Decoding under Cochannel Interference2011Ingår i: 2011 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), 2011, s. 5962542-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Multicell joint decoding (MJD) has been widely studied during the last decades as a new communication paradigm which can overcome the interference-limited nature of cellular systems. From a practical point of view, a feasible solution is to exploit clusters of cooperating Base Stations (BSs) with intracluster MJD. However, the clusters would still be affected by intercluster cochannel interference. In this paper, the corresponding channel model is established incorporating four impairments, namely additive white Gaussian noise, flat fading, path loss and cochannel interference. The asymptotic capacity limit of this channel is calculated based on an asymptotic free probability approach which exploits the additive and multiplicative free convolution in the R- and Σ-transform domain respectively, as well as properties of the η and Stieltjes transform. Numerical results are utilized to verify the accuracy of the derived closed-form expressions and evaluate the effect of the cochannel interference.

  • 340.
    Chatzinotas, Symeon
    et al.
    Interdisciplinary Centre for Security, Reliability and Trust, University of Luxembourg, Luxembourg.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Free probability based capacity calculation of multiantenna Gaussian fading channels with cochannel interference2011Ingår i: Physical Communication, ISSN 1874-4907, Vol. 4, nr 3, s. 206-217Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During the last decade, it has been well understood that communication over multiple antennas can increase linearly the multiplexing capacity gain and provide large spectral efficiency improvements. However, the majority of studies in this area were carried out ignoring cochannel interference. Only a small number of investigations have considered cochannel interference, but even therein simple channel models were employed, assuming identically distributed fading coefficients. In this paper, a generic model for a multiantenna channel is presented incorporating four impairments, namely additive white Gaussian noise, flat fading, path loss and cochannel interference. Both point-to-point and multiple-access MIMO channels are considered, including the case of cooperating Base Station clusters. The asymptotic capacity limit of this channel is calculated based on an asymptotic free probability approach which exploits the additive and multiplicative free convolution in the R- and S-transform domains, respectively, as well as properties of the η and Stieltjes transform. Numerical results are utilized to verify the accuracy of the derived closed-form expressions and evaluate the effect of the cochannel interference.

  • 341.
    Chatzinotas, Symeon
    et al.
    SnT - securityandtrust.lu, University of Luxembourg.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Interference Alignment for Clustered Multicell Joint Decoding2011Ingår i: 2011 IEEE Wireless Communications and Networking Conference, WCNC 2011, 2011, s. 1966-1971Konferensbidrag (Refereegranskat)
    Abstract [en]

    Multicell joint processing has been proven to be very efficient in overcoming the interference-limited nature of the cellular paradigm. However, for reasons of practical implementation global multicell joint decoding is not feasible and thus clusters of cooperating Base Stations have to be considered. In this context, intercluster interference has to be mitigated in order to harvest the full potential of multicell joint processing. In this paper, interference alignment is investigated as a means of intercluster interference mitigation and its performance is compared to global multicell joint processing. Both scenarios are modelled and analyzed using the per-cell ergodic sum-rate capacity as a figure of merit. In this process, a number of theorems are derived for analytically expressing the asymptotic eigenvalue distributions of the channel covariance matrices. The analysis is based on principles from Free Probability theory and especially properties in the R and Stieltjes transform domain.

  • 342.
    Chatzinotas, Symeon
    et al.
    SnT - securityandtrust.lu, University of Luxembourg.
    Zheng, Gan
    SnT - securityandtrust.lu, University of Luxembourg.
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Joint Precoding with Flexible Power Constraints in Multibeam Satellite Systems2011Ingår i: Proceedings Global Communications Conference (GLOBECOM), 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In conventional multibeam satellite systems, frequencyand polarization orthogonalization have been traditionallyemployed for mitigating interbeam interference. However, theparadigm of multibeam joint precoding allows for full frequencyreuse while assisting beam-edge users. In this paper, the performanceof linear beamforming is investigated in terms of meetingtraffic demands. More importantly, generic linear constraints areconsidered over the transmit covariance matrix in order to modelthe power pooling effect which can be implemented throughflexible traveling wave tube amplifiers (TWTAS) or multiportamplifiers. The performance of this scheme is compared againstconventional spotbeam systems based on the rate-balancingobjective. In this context, it is shown that significantly higherspectral efficiency can be achieved through beamforming, whileflexible power constraint offers better rate-balancing.

  • 343.
    Chen, Biao
    et al.
    Centre for Optical and Electromagnetic Research, Joint Laboratory of Optical Communications, Zhejiang University, Hangzhou 310027, China.
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Efficient and fine scheduling algorithm for bandwidth allocation in Ethernet passive optical networks2006Ingår i: IEEE Journal of Selected Topics in Quantum Electronics, ISSN 1077-260X, E-ISSN 1558-4542, Vol. 12, nr 4, s. 653-660Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel fine scheduling algorithm is introduced for upstream bandwidth allocation in an Ethernet-based passive optical network. This scheduling algorithm consists of an inter optical network unit (ONU) scheduler at the optical line terminal (OLT) and an intra-ONU scheduler at each ONU. In the inter-ONU scheduling, a novel GATE/REPORT approach is introduced to eliminate the unused remainders without transmission delay and maximize the utilization of bandwidth. Our novel intra-ONU scheduler gives fair bandwidth allocation to the queues of different priorities for each user in a hierarchical and decentralized way. Numerical results have shown that our overall scheduling algorithm can fulfill various requirements of delay and throughput for the transmission of multimedia traffic for each end user..

  • 344. Chen, Biao
    et al.
    Guo, Changjian
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Zhang, Linjian
    Jiang, Qiong
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Add/drop multiplexing and TDM signal transmission in an optical CDMA ring network2007Ingår i: Journal of Optical Networking, ISSN 1536-5379, Vol. 6, nr 8, s. 969-974Artikel i tidskrift (Refereegranskat)
  • 345.
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Design, analysis and simultion for optical access and wide-area networks.2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Due to the tremendous growth of traffic volume caused by both exponential increase of number of Internet users and continual emergence of new bandwidth demanding applications, high capacity networks are required in order to satisfactorily handle the extremely large amount of traffic. Hence, optical fiber communication is the key technology for the network infrastructure. This thesis addresses design, analysis and simulation of access and core networks targeting important research problems, which need to be tackled for the effective realization of next generation optical networks.

    Among different fiber access architectures, passive optical network (PON) is considered as the most promising alternative for the last mile connection due to its relatively low cost and resource efficiency. The inherent bursty nature of the user generated traffic results in dynamically changing bandwidth demand on per subscriber basis. In addition, access networks are required to support differentiated quality of service and accommodate multiple service providers. To address these problems we proposed three novel scheduling algorithms to efficiently realize dynamic bandwidth allocation in PON, along with guaranteeing both the priority and fairness of the differentiated services among multiple users and/or service providers. Meanwhile, because of the increasing significance of reliable access to network services, an efficient fault management mechanism needs to be provided in PON. In addition, access networks are very cost sensitive and the cost of protection should be kept as low as possible. Therefore, we proposed three novel cost-effective protection architectures keeping in mind that reliability requirement in access networks should be satisfied at the minimal cost.

    Regarding the optical core networks, replacing electronic routers with all-optical switching nodes can offer significant advantages in realizing high capacity networks. Because of the technological limitations for realizing all-optical nodes, the focus is put on the ingenious architecture design. Therefore, we contributed on novel switching node architectures for optical circuit and packet switching networks. Furthermore, we addressed different aspects of routing and wavelength assignment (RWA) problem, which is an important and hard task to be solved in wavelength routed networks. First, we proposed an approach based on the information summary protocol to reduce the large amount of control overhead needed for dissemination of the link state information in the case of adaptive routing. In addition, transparency in optical networks may cause vulnerability to physical layer attacks. To target this critical security related issue, we proposed an RWA solution to minimize the possible reachability of a jamming attack.

    Finally, in order to evaluate our ideas we developed two tailor-made simulators based on discrete event driven system for the detailed studies of PON and switched optical networks. Moreover, the proposed tabu search heuristic for our RWA solution was implemented in C++.

  • 346.
    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.

  • 347.
    Chen, Jiajia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Chen, Bao
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    A Novel Joint Scheduling Algorithm for Multiple Services in 10G EPON2008Ingår i: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 7137Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    In this paper, we propose and evaluate a novel joint scheduling algorithm for multiple services which can support differentiated services and bandwidth allocation with global priority of different traffic such as Triple-play: voice, video and Internet services. Simulation results show that for the higher priority traffic better delay and jitter performance can be achieved compared with the lower priority traffic.

  • 348.
    Chen, Jiajia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Chen, Biao
    Centre for Optical Electromagnetic Research, Joint Laboratory of Optical Communications, Zhejiang University, Hangzhou 310027, China.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Self-protection scheme against failures of distributed fiber links in an Ethernet passive optical network2006Ingår i: Journal of Optical Networking, ISSN 1536-5379, Vol. 5, nr 9, s. 662-666Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel self-protection scheme for an Ethernet passive optical network is introduced and studied at both the physical and the media access control layers. The scheme is simple and fast and can provide 1: 1 protection and automatic traffic restoration against the fiber link failure between a remote node ( RN) and any optical network unit (ONU). Simulation results show that fiber failure does not degrade the transmission performance, and the restoration time depends mainly on the switch time of the physical layer. Our protection scheme saves many long fibers, does not influence other normal ONUs, and requires no active device in the RN.

  • 349.
    Chen, Jiajia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Chen, Biao
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101).
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Fotonik (Stängd 20120101).
    Joint Bandwidth Scheduling to Support Differentiated Services and Multiple Service Providers in 1G and 10G EPONs2009Ingår i: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, ISSN 1943-0620, Vol. 1, nr 4, s. 343-351Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dynamic bandwidth allocation (DBA) is one of the key issues for the current (1G) and next-generation (10G) Ethernet-based passive optical network (EPON) systems. We present a novel bandwidth scheduling scheme that integrates specific scheduling implementations in the optical line terminal and optical network units. This scheduling enables multiservice access with scalable quality of service support for the triple-play (video, voice, and data) services and open access. Our simulation results show that the proposed scheduling algorithm performs very well in supporting service differentiation and fair allocation of bandwidth to different service providers. A performance comparison between 1G and 10G systems is also presented. To the best of our knowledge, no detailed study of DBA in a 10G EPON can be found in the literature so far.

  • 350.
    Chen, Jiajia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Gong, Yu
    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).
    High Capacity and Energy Efficient Optical Interconnects at Top of the Rack in Datacentres2014Konferensbidrag (Refereegranskat)
45678910 301 - 350 av 2591
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