Change search
Refine search result
1234567 151 - 200 of 741
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 151.
    El-Ansary, Sameh
    et al.
    Swedish Institute of Computer Science (SICS).
    Haridi, Seif
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    An overview of structured P2P overlay networks2006In: Handbook on Theoretical and Algorithmic Aspects of Sensor, Ad Hoc Wireless, and Peer-to-Peer Networks / [ed] Jie Wu, Auerbach Publications , 2006Chapter in book (Other academic)
  • 152.
    El-Ansary, Sameh
    et al.
    Distributed Systems Laboratory, SICS Swedish Institute of Computer Science.
    Krishnamurthy, Supriya
    Distributed Systems Laboratory, SICS Swedish Institute of Computer Science.
    Aurell, Erik
    KTH, School of Engineering Sciences (SCI), Physics.
    Haridi, Seif
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Analytical study of consistency and performance of DHTs under churnManuscript (preprint) (Other academic)
    Abstract [en]

    In this paper, we present a complete analytical study of dynamic membership (aka churn) in structured peer-to-peer networks. We use a master-equation-based approach, which is used traditionally in non-equilibrium statistical mechanics to describe steady-state or transient phenomena. We demonstrate that this methodology is infact also well suited to describing structured overlay networks by an application to the Chord system. For any rate of churn and stabilization rates, and any system size, we accurately account for the functional form of: the distribution of inter-node distances, the probability of network disconnection, the fraction of failed or incorrect successor and finger pointers and show how we can use these quantities to predict both the performance and consistency of lookups under churn. Additionally, we also discuss how churn may actually be of different ’types’ and the implications this will have for structured overlays in general. All theoretical predictions match simulation results to a high extent. The analysis includes details that are applicable to a generic structured overlay deploying a ring as well as Chord-specific details that can act as guidelines for analyzing other systems.

  • 153.
    Emmoth, Birger
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Khartsev, Sergiy
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Pisarev, A.
    Grishin, Alexander
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Litnovsky, A.
    Rubel, Marek J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Wienhold, P.
    Fuel removal from bumper limiter tiles by using a pulsed excimer laser2005In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 337-39, no 1-3, p. 639-643Article in journal (Refereed)
    Abstract [en]

    Samples of a limiter tile from the TEXTOR tokamak were investigated by scanning electron microscopy and nuclear reaction analysis both before and after laser heating. SEM images showed spheres and thin flakes covering the surface which are the areas modified by plasma particles striking under grazing angles. Due to roughness of the surface there are shadowed regions between the 'flakes'. Laser pulses did not lead to expected common ablation of the surface. Features that looked like 'melting' of thin surface layers were rather observed. The initial deuterium content in the surface layer of tiles was of the order of 10(18) D atoms per cm(2). After the laser light impact the content decreased with 60-70%; by reducing the deposited power by a factor four, the deuterium content was decreased by 40-50%. We make the interpretation that we approach a threshold of the laser detritiation method in fusion devices.

  • 154.
    Emmoth, Birger
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Kreter, A.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Jakubowski, M.
    Lehnen, M.
    Litnovsky, A.
    Petersson, P.
    Philipps, V.
    Possnert, G.
    Rubel, Marek J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Schweer, B.
    Sundelin, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Unterberg, B.
    Wienhold, P.
    In-situ measurements of carbon and deuterium deposition using the fast reciprocating probe in TEXTOR2009In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 390-91, p. 179-182Article in journal (Refereed)
    Abstract [en]

    Silicon samples were exposed in the scrape-off layer of the TEXTOR plasma using a fast reciprocating probe, with the aim of studying carbon deposition and deuterium retention during Dynamic Ergodic Divertor (DED) operation. Separate samples were exposed for 300 ms at the flat-top phase of neutral beam heated discharges. The exposure conditions were varied on a shot-to-shot basis by external magnetic perturbations generated by the DED in the m/n = 3/1, DC regime, base configuration. Nuclear Reaction Analysis (NRA) was used to characterise collector sample surfaces after their exposure. Enhanced concentrations of both carbon and deuterium (C 3-10 x 10(16) at./cm(2), D 8-60 x 10(15) at./cm(2)) were found. The D/C ratio was less than unity which indicates that most of the carbon and deuterium were co-deposited. Carbon e-folding lengths of about 2 cm were found on both toroidal sides of the probe independent of DED perturbations.

  • 155.
    Ericsson, Fredrik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Agent based mobile Internet services2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis investigates how to develop mobile SMS services using Personal Internet Agents. A platform for Personal Internet Agents is implemented to serve as a framework in which mobile services can easily be created, executed, and administered. The services are based on extracting information and events from various sources on the Internet, then communicating these to the mobile end user.

    To evaluate the platform several investigations are carried out regarding scalability, integration possibilities, and performance. To illustrate the functionality of the platform a full-blown mobile service is developed that illustrates the gain of the Personal Internet Agents in combination with the mobile Internet. The service, named Spymail, fetches e-mail from Microsoft’s Hotmail and forwards these to the user via SMS.

    Developing services based on agents rises several issues. Since web sites on the Internet sometimes change, go down, etc, agents have to be informed about this to be able to adapt to the situation. Another issue is if it is possible to create a large multi-user agent service or if the bandwidth or computational speed will be a constraint.

  • 156.
    Erikson, Gustaf
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Application of inertial sensing to handheld terminals2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    We consider the potential for using inertial sensing in handheld terminals.As an example, the implementation of an inertial sensing system in twodimensions for the research terminal Tifón at Ericsson Radio is discussed.The implementation includes hardware design, microcode software for aneight-bit micro-controller, and software for communication with the operat-ing system of the terminal.

  • 157.
    Ervenius, Johan
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Tysk, Filip
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Dual-mode Capability in a WLAN-equipped PC for Roaming and Mobility between WLANs and GPRS Networks2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The goal of this masters thesis work has been to develop and evaluate a solution that enables a WLAN-equipped mobile PC to establish and maintain connectivity by means of cellular network services, and more specifically a GPRS network, when roaming and moving outside the coverage area of a WLAN.

    Both network operators and the software industry are looking for inter-technology roaming solutions that can be implemented with minimal changes to existing infrastructures and standards. We have come to the conclusion that the use of Mobile IP is the solution that best meets these conditions as it is implemented on an IP level and treats wireless LAN and GPRS as peer networks, without any modifications to WLAN or GPRS protocols.

    In addition to the architectural solution efficient mobility is also dependent on the choice of handover algorithm, which decides when to connect to the WLAN and when to connect to the GPRS network. Using studies and measurements we have concluded that a good handover algorithm is vital for good TCP performance when performing a handover between WLAN and GPRS.

  • 158. Estephan, Elias
    et al.
    Saab, Marie-belle
    Larroque, Christian
    Martin, Marta
    Olsson, Fredrik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Gergely, Csilla
    Peptides for functionalization of InP semiconductors2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 337, no 2, p. 358-363Article in journal (Refereed)
    Abstract [en]

    The challenge is to achieve high specificity in molecular sensing by proper functionalization of micro/nano-structured semiconductors by peptides that reveal specific recognition for these structures. Here we report on surface modification of the InP semiconductors by adhesion peptides produced by the phage display technique. An M13 bacteriophage library has been used to screen 10(10) different peptides against the InP(0 0 1) and the InP(1 1 1) surfaces to finally isolate specific peptides for each orientation of the InP. MALDI-TOF/TOF mass spectrometry has been employed to study real affinity of the peptide towards the InP surfaces. The peptides serve for controlled placement of biotin onto InP to bind then streptavidin. Our Atomic Force Microscopy study revealed a total surface coverage of molecules when the InP surface was functionalized by its specific biotinylated peptide (YAIKGPSHFRPS). Finally, fluorescence microscopy has been employed to demonstrate the preferential attachment of the peptide onto a micro-patterned InP surface. Use of substrate specific peptides could present an alternative solution for the problems encountered in the actually existing sensing methods and molecular self-assembly due to the unwanted unspecific interactions.

  • 159. Ferrini, R.
    et al.
    Martz, J.
    Zuppiroli, L.
    Wild, B.
    Zabelin, V.
    Dunbar, L. A.
    Houdre, R.
    Mulot, M.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Planar photonic crystals infiltrated with liquid crystals: optical characterization of molecule orientation2006In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 31, no 9, p. 1238-1240Article in journal (Refereed)
    Abstract [en]

    Nematic liquid crystals are infiltrated into InP-based planar photonic crystals. Optical measurements as a function of temperature and polarization are used to study the average director field configuration in the nanometer-size holes: a planar equilibrium state is found.

  • 160.
    Fey, Zsuzsa
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Adapting and Optimising TCP/IP on Satellite Networks2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today communication has become an essential part of our lives. As communication becomes even more global, one has to search for new communication forms, which can satisfy the new needs of the customers. One emerging area is communication via satellites. As the TCP/IP protocol family is the most used protocol family in today's Internet, but was developed primarily for communication on wired links, it has suboptimal behaviour when used with satellite links.

    The purpose of this master's thesis is to examine the shortcomings of using the TCP/IP protocol suite on satellite links, to see what types of problems occur in satellite communication, how these problems affect TCP/IP and to try to find solutions to the problems found.

    The thesis begins with a presentation of the TCP/IP protocols and the issues regarding satellite communications, more precisely the DVB-RCS standard. Then we will take a look at existing improvements for TCP/IP communication over satellite links. The main part of the thesis is to study the behaviour of the different implementations of the TCP/IP protocolson satellite links and to examine possible improvements.

    Finally there are presented the conclusions drawn. The experiments showed that better performance is achieved for initial congestion window sizes of 3 or 4. It was also seen a performance discontinuity at return channel bandwidth of 512 kbps. At low BER TCP Reno performed best, while at high BER no general behaviour was seen. However, at high BER TCP SACK or TCP FACK performed best in most of the studied cases.

  • 161. Flanagan, K. T.
    et al.
    Vingerhoets, P.
    Avgoulea, M.
    Billowes, J.
    Bissell, M. L.
    Blaum, K.
    Cheal, B.
    De Rydt, M.
    Fedosseev, V. N.
    Forest, D. H.
    Geppert, Ch.
    Koester, U.
    Kowalska, M.
    Kraemer, J.
    Kratz, K. L.
    Krieger, A.
    Mane, E.
    Marsh, B. A.
    Materna, T.
    Mathieu, L.
    Molkanov, P. L.
    Neugart, R.
    Neyens, G.
    Noertershaeuser, W.
    Seliverstov, M. D.
    Serot, O.
    Schug, M.
    Sjödin, Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Stone, J. R.
    Stone, N. J.
    Stroke, H. H.
    Tungate, G.
    Yordanov, D. T.
    Volkov, Yu. M.
    Nuclear Spins and Magnetic Moments of Cu-71,Cu-73,Cu-75: Inversion of pi 2p(3/2) and pi 1f(5/2) Levels in Cu-752009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, no 14, p. 142501-Article in journal (Refereed)
    Abstract [en]

    We report the first confirmation of the predicted inversion between the pi 2p(3/2) and pi 1f(5/2) nuclear states in the nu g(9/2) midshell. This was achieved at the ISOLDE facility, by using a combination of in-source laser spectroscopy and collinear laser spectroscopy on the ground states of Cu-71,Cu-73,Cu-75, which measured the nuclear spin and magnetic moments. The obtained values are mu(Cu-71)=+2.2747(8)mu(N), mu(Cu-73)=+1.7426(8)mu(N), and mu(Cu-75)=+1.0062(13)mu(N) corresponding to spins I=3/2 for Cu-71,Cu-73 and I=5/2 for Cu-75. The results are in fair agreement with large-scale shell-model calculations.

  • 162. Fontaine, N. K.
    et al.
    Baek, J. -H
    Ji, C.
    Broeke, R. G.
    Zhou, X.
    Seo, S. -W
    Soares, F. M.
    Shearn, M.
    Scherer, A.
    Olsson, Fredrik E.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Liu, K. Y.
    Tsang, W. T.
    Yoo, S. J. B.
    Monolithically integratable colliding pulse modelocked laser source for O-CDMA photonic chip development2008Conference paper (Refereed)
    Abstract [en]

    We demonstrate modelocking of a colliding-pulse mode-locked laser formed by 3-μm-deep etched-mirrors on an InP platform for integration with passive waveguide components. Timing jitter of 243 fs and pulse width of 10 ps were measured.

  • 163. Fontaine, N. K.
    et al.
    Wei, J.
    Soares, F. M.
    Broeke, R. G.
    Seo, S. -W
    Baek, J. -H
    Cao, J.
    Okamoto, K.
    Yoo, S. J. B.
    Olsson, Fredrik
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Determination of 20 GHz InP AWG phase errors by measurement of AWG pulse train2007In: 2007 IEEE LEOS Annual Meeting Conference Proceedings, IEEE , 2007, p. 725-726Conference paper (Refereed)
    Abstract [en]

    The phase errors of a 20 GHz AWG fabricated on InP are determined by measuring the intensity and phase of the pulse train produced by the transmission of a short pulse through an AWG.

  • 164.
    Forsell, Erik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Internet Telephony: An Internet Service Provider's Perspective2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this Masters Thesis is to propose to SYSteam Nät AB, a local Internet Service Provider (ISP) in Uppsala, Sweden, how to implement IP telephony in their existing ITinfrastructure as a service to their customers. Thus the perspective of the thesis will be that of a local Internet Service Provider. Three general areas are covered in the thesis: Market and Business Model, Technology, and Economics.

    Important issues for SYSteam Nät AB as an established local broadband Internet Service Provider are to both retain present customers and to attract new customers. Some believe that offering value added services such as IP telephony could do this.

    Implementation of IP telephony can be done in different ways to fulfil SYSteam Nät’s requirements. The analysis leads to a proposal of how SYSteam Nät could implement IP telephony. This involves many multi-faceted business, technical, and financial issues; each aspect is examined in this thesis.

  • 165.
    Fredén, Magnus
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Mobile Internet: Testing of Internet services2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In addition to the problems that may occur in the Internet, the people who test mobile internet services confront additional challenges due to the wireless environment. If something goes wrong, it is very problematic for a tester to determine exactly where the error occurred and the reason why it occurred. Is it the software in the telephone that does not work properly, is the GPRS link stable, is the core network of the Internet working as it should, or is there something wrong at the server? The staff at Sony Ericsson has major difficulties determining where the origin of a problem is. They often simply know that something is not working. The major effort is often to detect the source of the actual problem rather than solving it.

    The PlayNow service provided by Sony Ericsson will be used as a reference service in this master’s thesis project. The PlayNow service is currently used for distributing ring signals. It is built on Internet standards, but depends on GSM’s specific features both for distribution and for e-commerce which makes it hard to test using existing web test tools. This Master’s Thesis examines the difficulties in establishing robust IP traffic links between a server and a mobile telephone. It examines the entire communication path between the mobile telephone and the server, and focus on how to detect (potential) errors. Within this project, development of a test tool is included. It supports features necessary for testing the reference service PlayNow.

    This report covers many different technologies within the mobile internet such as GSM, GPRS, and mobile IP. Moreover, the normal infrastructure of the Internet will also be considered; as well as how the different parts interact in an environment consisting of a mobile Internet with GPRS. A major part of the project has been evaluation of the communication link between a mobile device and a server. Additionally, some efforts have focused on developing the new test tool.

  • 166.
    Fu, Jing
    et al.
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sjödin, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Karlsson, Gunnar
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Convergence of intra-domain routing with centralized control2008In: AD HOC AND SENSOR NETWORKS, WIRELESS NETWORKS, NEXT GENERATION INTERNET, PROCEEDINGS, 2008, Vol. 4982, p. 518-529Conference paper (Refereed)
    Abstract [en]

    The decentralized control scheme for routing in current IP networks has been questioned, and a centralized routing scheme has been proposed as an alternative. In this paper, we compare the convergence of centralized control scheme with decentralized link-state routing protocols. We first identify the components of the convergence time. Thereafter, we study how to achieve fast routing convergence in networks with centralized control. In particular, we analyze how to distribute forwarding information efficiently. Finally, we perform simulation studies on the convergence time for both real and synthetic network topologies, and study the impact of control element location, link weights, and number of failures on the convergence time. The results show that the centralized control scheme can provide faster routing convergence than link-state routing protocols.

  • 167.
    Färm, Petra
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Integrated Logic Synthesis Using Simulated Annealing2007Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    A conventional logic synthesis flow is composed of three separate phases: technologyindependent optimization, technology mapping, and technology dependentoptimization. A fundamental problem with such a three-phased approach is thatthe global logic structure is decided during the first phase without any knowledge ofthe actual technology parameters considered during later phases. Although technologydependent optimization algorithms perform some limited logic restructuring,they cannot recover from fundamental mistakes made during the first phase, whichoften results in non-satisfiable solutions.We present a global optimization approach combining technology independentoptimization steps with technology dependent objectives in an annealing-basedframework. We prove that, for the presented move set and selection distribution, detailedbalance is satisfied and thus the annealing process asymptotically convergesto an optimal solution. Furthermore, we show that the presented approach cansmoothly trade-off complex, multiple-dimensional objective functions and achievecompetitive results. The combination of technology independent and technologydependent objectives is handled through dynamic weighting. Dynamic weightingreflects the sensitivity of the local graph structures with respect to the actual technologyparameters such as gate sizes, delays, and power levels. The results showthat, on average, the presented advanced annealing approach can improve the areaand delay of circuits optimized using the Boolean optimization technique providedby SIS with 11.2% and 32.5% respectively.Furthermore, we demonstrate how the developed logic synthesis framework canbe applied to two emerging technologies, chemically assembled nanotechnology andmolecule cascades. New technologies are emerging because a number of physicaland economic factors threaten the continued scaling of CMOS devices. Alternativesto silicon VLSI have been proposed, including techniques based on molecularelectronics, quantum mechanics, and biological processes. We are hoping that ourresearch in how to apply our developed logic synthesis framework to two of theemerging technologies might provide useful information for other designers movingin this direction.

  • 168.
    Färm, Petra
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Dubrova, Elena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Kuehlmann, Andreas
    Logic optimization using rule-based randomized search2005In: ASP-DAC 2005: Proceedings Of The Asia And South Pacific Design Automation Conference, IEEE , 2005, p. 998-1001Conference paper (Refereed)
    Abstract [en]

    In this paper we describe a new logic synthesis approach based on rule-based randomized search using simulated annealing. Our work is motivated by two observations: (1) Traditional logic synthesis applies literal count as the primary quality metric during the technology independent optimization phase. This simplistic metric often leads to poor circuit structures as it cannot foresee the impact of early choices on the final area, delay, power consumption, etc. (2) Although powerful, global Boolean optimization is not robust and corresponding algorithms cannot be used in practice without artificially restricting the application window. Other techniques, such as algebraic methods scale well but provide weaker optimization power To address both problems, we use randomized search that is based on a simple circuit graph representation and a complete set of local transformations that include algebraic and Boolean optimization steps. The objective of the search process can be tuned to complex cost functions, combining area, timing, routability, and power Our experimental results on benchmark functions demonstrate the significant potential of the presented approach.

  • 169.
    Färm, Petra
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Dubrova, Elena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Tenhunen, Hannu
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Logic optimization technique for molecular cascades2005In: Nanotechnology II / [ed] Lugli, P; Kish, LB; Mateos, J, SPIE - International Society for Optical Engineering, 2005, Vol. 5838, p. 95-104Conference paper (Refereed)
    Abstract [en]

    Molecular cascades introduced in(1) provide new ways to exploit the motion of individual molecules in nanometer-scale structures. Computation is performed by purely mechanical means similarly to the toppling of a row of standing domino. A specific feature of molecular cascades is that an inverter cannot be build, because it would require that all molecules in the inverter's output untopple when the input cascade topples. This is not possible because an untoppled state has higher energy than a toppled one. As a solution, we propose to avoid the need for inverters by representing signals by the dual-rail convention. As a basic building block we use a molecular block, which has four inputs x(1),...,x(4) such that x(3) = x(1)', x(4) = x(2)', and two outputs f(1) = x(1) . x(2) and f(2) = x(3) + x(4). If input variables are available in both complemented and non-complemented form, then any Boolean function can be implemented by a composition of such molecular blocks. We present an experimental tool which first uses a rule-based randomized search to optimize a Boolean network and then maps it into a network of interconnected molecular blocks.

  • 170.
    Gaitan, Ivar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Real-time services and multihop networks: Delay analysis of a multihop CDMA fixed relay network2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The next generation of cellular networks is expected to carry high speed IP traffic in a packet switched environment in order to accommodate data traffic for a wide range of services. Much research is thus focused on how to increase the transmission rate in cellular networks. A general consequence of increasing transmission rate in a radio link is a corresponding increase in transmit power, resulting in increased interference and reduced network capacity. The straightforward way to reduce this effect is to shorten the link distance, which in the cellular case means shrinking the cells. This, however, means increased control traffic for handoffs and location registration, as well as increased infrastructure costs.

    An alternative approach, which has received increased attention lately, is the introduction of wireless multihop access networks to relay traffic between the wired infrastructure and the users. Such an access network must clearly accommodate all types of services expected to operate in next generation systems, including real-time services. However, wireless multihop networks have traditionally had problems meeting the delay requirements posed by such services.

    In this thesis, we will study the delay performance through analysis and simulation of such a network, based on the Virtual Cellular Network proposal [1], in which geographically fixed wireless relays are deployed to act as both network nodes and user relays.

  • 171. Galeckas, A.
    et al.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Pirouz, P.
    Recombination-induced stacking faults: Evidence for a general mechanism in hexagonal SiC2006In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 96, no 2Article in journal (Refereed)
    Abstract [en]

    We report on optically induced nucleation and expansion of stacking faults in hexagonal SiC structures. The activation energy for partial dislocation glide under optical excitation is found to reduce to 0.25 +/- 0.05 eV, which is about 2 eV lower than for pure thermal activation. From the measurements of thermal activation and below-gap excitation spectroscopy of dislocation glide, we conclude that the elementary process controlling expansion of stacking faults is kink pair nucleation aided by the phonon-kick mechanism. We propose that solitons on 30 degrees Si(g) partials with a silicon core act as deep 2.4 eV+E-V trap sites, readily providing electron-hole recombination energy to enhance the motion of dislocations. Our results suggest that this is a general mechanism of structural degradation in hexagonal SiC.

  • 172.
    Galeckas, Augustinas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hallen, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schoner, A.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Pirouz, P.
    Investigation of structural stability in 4H-SiC structures with heavy ion implanted interface2006In: Silicon Carbide and Related Materials 2005, Pts 1 and 2, 2006, Vol. 527-529, p. 395-398Conference paper (Refereed)
    Abstract [en]

    We investigate the possibility of controlling formation of stacking faults (SFs) at the interface region by implanting the 4H-SiC substrate with low-energy antimony ions (75 keV Sb+) prior to conventional CVD growth of the homoepitaxial layers. This approach is based on the solidsolution hardening concept, according to which interaction of impurity atoms with dislocations makes the motion of the latter more difficult. Photoluminescence imaging spectroscopy is employed to investigate incorporation of Sb+ implants at the buried interface and also to assess its impact on structural degradation. Spectral results are analyzed considering both the onset of n-type doping and irradiation damage. The latter factor was estimated separately from supplementary measurements of high-energy (2.5 MeV H+) proton-irradiated 4H-SiC epilayers. We compare results of optically stimulated SF formation in virgin and Sb implanted regions and provide a comprehensive picture of the defect evolution, including microscopic details of the imminent nucleation sites.

  • 173.
    Galeckas, Augustinas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Kortegaard Nielsen, Hanne
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Svensson, Bengt G.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Pirouz, P
    Investigation of stacking fault formation in hydrogen bombarded 4H-SiC2005In: SILICON CARBIDE AND RELATED MATERIALS 2004 / [ed] Nipoti, R; Poggi, A; Scorzoni, A, 2005, Vol. 483, p. 327-330Conference paper (Refereed)
    Abstract [en]

    The effects of hydrogen and proton irradiation on stacking fault formation in 4H-SiC are investigated by an optical pump-probe method of imaging spectroscopy. We report optically stimulated nucleation and expansion of stacking faults (SFs) in 0.6 keV H-2(+) implanted n-/n+ and p+/n-/n+ structures. The activation enthalpy for recombination enhanced dislocation glide (REDG) in hydrogenated samples (∼ 0.25 eV) is found to be similar to that in a virgin material. Our results indicate that SFs mainly nucleate at the internal n-/n+ interface, beyond reach of hydrogen, thus justifying minor SF passivation effect. No REDG could be initiated optically in 2.5 MeV proton irradiated samples due to radiation defects providing alternative recombination channels to bypass the REDG mechanism. The radiation damage was verified by DLTS, revealing several new levels below E-C in the range 0.4-0.80 eV, and by PL, showing the onset of D-center related luminescence band and concurrent increase of the nonradiative recombination rate.

  • 174.
    Garcia Lozano, Marianela
    et al.
    FOI, Swedish Defence Research Agency, Department of Systems Modelling.
    Chenine, Moustafa
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Kabilan, Vandana
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A pattern for designing distributed heterogeneous ontologies for facilitating application interoperabilityManuscript (preprint) (Other academic)
  • 175.
    Garcia Lozano, Marianela
    et al.
    FOI, Swedish Defence Research Agency, Department of Systems Modelling.
    Moradi, Farshad
    FOI, Swedish Defence Research Agency.
    Ibarzabal, Eneko
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Tjörnhammar, Edward
    FOI, Swedish Defence Research Agency.
    A semantic approach to simulation component identification and discovery2009In: 21st European Modeling and Simulation Symposium, EMSS 2009, 2009, p. 181-186Conference paper (Refereed)
    Abstract [en]

    Development of simulations is often a costly process that consumes a lot of time and resources. An appealing approach to reduce the costs involved is to reuse and recombine existing predefined models and components through a composition process. This process is a complex task that involves four main steps: identification, discovery, matching and composition. The focus of this work is to show how different ontologies combined with semantic querying enables more accurate identification and discovery of components in the process. We present a methodology for achieving this goal and clarification through a use case. Our preliminary results indicate that our approach is feasible, and semantic techniques contribute to both finer descriptions and search results.

  • 176.
    García Hijes, Raúl
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Corporate Wireless IP Telephony2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    IP telephony is defined as the transport of telephony calls over an IP network. IP telephony exploits the integration of voice and data networks. However, enterprises are still reluctant to deploy IP telephony despite the potential increase in productivity and reduction of costs. The principal concerns are: can IP telephony provide the same level of performance in terms of security, reliability, and scalability as traditional telephony? If so, are its proclaimed benefits such as flexibility and mobility cost-effective?

    The aim of this thesis is to analyze how to deploy IP telephony in large corporations - while providing the necessary security and facilitating mobility. Through the different parts of this thesis, we will analyze the applicable technologies, along with their integration and management. We will focus on the essential requirements for an enterprise of scalability, reliability, flexibility, high-availability, and cost-effectiveness.

    The massive changes brought about due to the deregulation of telecommunications in nearly all countries, the increasingly global nature of business, and the progressively affordable and power technology underlying information and communication technologies have lead to increasing adoption of IP telephony by residential and commercial users. This thesis will examine these technologies in the context of a very large distributed corporation. 

  • 177.
    García Lozano, Marianela
    et al.
    FOI, Swedish Defence Research Agency, Department of Systems Modelling.
    Moradi, Farshad
    FOI, Swedish Defence Research Agency, Department of Systems Modelling.
    Ayani, Rassul
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    SDR: a semantic based Distributed Repository for Simulation Models and Resources2007In: AMS 2007: First Asia International Conference on Modelling & Simulation Asia Modelling Symposium, 2007, p. 171-176Conference paper (Refereed)
    Abstract [en]

    Recent advances in Internet, Peer-to-Peer and Grid technologies have made collaboration and resource sharing across organizational boundaries more feasible. Today, it is essential for many organizations to be able to discover share and manage distributed resources in a transparent, meaningful and secure way. A fundamental problem is locating, matching and composing resources or services of interest. In this paper we describe our initial work designing and developing a semantic based distributed repository for secure sharing of simulation models, components and related resources such as computer resources. We propose an overlay architecture which combines advances in Semantic Web, Peer-to-Peer and Grid techniques. In our project at the Swedish Defence Research Agency (FOI) we had a need for a repository of simulation related resources and having identified our requirements we found that there was no suitable of-the-shelf system available. We describe the design, tools and a prototype implementation of this system - the Semantic based Distributed Repository (SDR) and conclude with our experiences and some raised issues. We argue that although some of the used techniques still are a bit immature and need further improvements a system like the SDR has a lot of potential and can also be used in other domains than modeling and simulation.

  • 178. Gasior, P.
    et al.
    Irrek, F.
    Petersson, P.
    Penkalla, Hj.
    Rubel, Marek J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Schweer, B.
    Sundelin, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Wessel, E.
    Linke, J.
    Philipps, V.
    Emmoth, Birger
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wolowski, J.
    Hirai, T.
    Laser-induced removal of co-deposits from graphitic plasma-facing components: Characterization of irradiated surfaces and dust particles2009In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 390-91, p. 585-588Article in journal (Refereed)
    Abstract [en]

    Laser-induced fuel desorption and ablation of co-deposited layers on limiter plates from the TEXTOR tokamak have been studied. Gas phase composition was monitored in situ, whereas the ex situ studies have been focused on the examination of irradiated surfaces and broad analysis of dust generated by ablation of co-deposits. The size of the dust grains is in the range of few nanometers to hundreds of micrometers. These are fuel-rich dust particles, as determined by nuclear reaction analysis. The presence of deuterium in dust indicates that not all fuel species are transferred to the gas phase during irradiation. This also suggests that photonic removal of fuel and the ablation of co-deposit from plasma-facing components may lead to the redistribution of fuel-containing dust to surrounding areas.

  • 179. Ge, C.
    et al.
    Jia, L.
    Zheying, L.
    Li, Shuo
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Connecting bridge in SoC used for wireless home healthcare system2008In: Int. Symp. Wirel. Pervasive Comput., ISWPC, Proc., 2008, p. 194-197Conference paper (Refereed)
    Abstract [en]

    A connection bridge for connection of two CPU systems in SoC of the HAB (healthcare apparatus on body/bed) in home healthcare wireless network is addressed. Multi CPU system in a SoC could be divided into different part according with data process function. Therefore the each part of the system can work independently without influence each other. With the discussion of the performance of HAB and home networking, the connection bridge is a suitable technology for reducing dies size and power consumption. The connection bridge designed in the paper connects two CPU systems and two digital circuitry components together. To the CPU system, common digital circuitry is a part of the CPU system with the bridge. The architecture and logic function of the connection bridge is analyzed in detail and simulated. The simulation results demonstrate that the connection bridge can not only supply the connection of two CPU and two common components, display module and RAM, but also increase the running speed and system performance.

  • 180. Ghandi, R.
    et al.
    Kolahdouz, M.
    Hållstedt, Julius
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wise, R.
    Wejtmans, Hans
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Effect of strain, substrate surface and growth rate on B-doping in selectively grown SiGe layers2008In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 517, no 1, p. 334-336Article in journal (Refereed)
    Abstract [en]

    In this work, the role of strain and growth rate on boron incorporation in selective epitaxial growth (SEG) of B-doped Si1-xGex (x=0.15-0.25) layers in recessed or unprocessed (elevated) openings for source/drain applications in CMOS has been studied. A focus has been made on the strain distribution and B incorporation in SEG of SiGe layers.

  • 181.
    Ghandi, Reza
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Buono, Benedetto
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Domeij, Martin
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Malm, B. Gunnar
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zetterling, Carl-Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    High-Voltage 4H-SiC PiN Diodes With Etched Junction Termination Extension2009In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 30, no 11, p. 1170-1172Article in journal (Refereed)
    Abstract [en]

    Implantation-free mesa-etched 4H-SiC PiN diodes with a near-ideal breakdown voltage of 4.3 kV (about 80% of the theoretical value) were fabricated, measured, and analyzed by device simulation and optical imaging measurements at breakdown. The key step in achieving a high breakdown voltage is a controlled etching into the epitaxially grown p-doped anode layer to reach an optimum dopant dose of similar to 1.2 x 10(13) cm(-2) in the junction termination extension (JTE). Electroluminescence revealed a localized avalanche breakdown that is in good agreement with device simulation. A comparison of diodes with single-and double-zone etched JTEs shows a higher breakdown voltage and a less sensitivity to varying processing conditions for diodes with a two-zone JTE.

  • 182. Ghiu, Iulia
    et al.
    Björk, Gunnar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    ASYMMETRIC TWO-OUTPUT QUANTUM PROCESSOR IN ANY DIMENSION2008In: Romanian Journal of Physics, ISSN 1221-146X, Vol. 53, no 5-6, p. 725-737Article in journal (Refereed)
    Abstract [en]

    We propose two different implementations of an asymmetric two-output probabilistic quantum processor. One of them is constructed by combining asymmetric telecloning with a quantum gate array. We analyze the efficiency of this processor by evaluating the fidelities between the desired operation and the ones generated by the processor and show that the two output states are the same as the ones produced by the optimal universal asymmetric Pauli cloning machine and have a success probability of 1/2. We show further that we can perform the same one-qubit operation with unity probability at the cost of using nonlocal operations. We finally generalize the two schemes for D-level systems and find that the local ones are successful with a probability of 1/D and the nonlocal generalized scheme is always successful.

  • 183.
    Ghodsi, Ali
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Distributed k-ary System: Algorithms for Distributed Hash Tables2006Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    This dissertation presents algorithms for data structures called distributed hash tables (DHT) or structured overlay networks, which are used to build scalable self-managing distributed systems. The provided algorithms guarantee lookup consistency in the presence of dynamism: they guarantee consistent lookup results in the presence of nodes joining and leaving. Similarly, the algorithms guarantee that routing never fails while nodes join and leave. Previous algorithms for lookup consistency either suffer from starvation, do not work in the presence of failures, or lack proof of correctness.

    Several group communication algorithms for structured overlay networks are presented. We provide an overlay broadcast algorithm, which unlike previous algorithms avoids redundant messages, reaching all nodes in O(log n) time, while using O(n) messages, where n is the number of nodes in the system. The broadcast algorithm is used to build overlay multicast.

    We introduce bulk operation, which enables a node to efficiently make multiple lookups or send a message to all nodes in a specified set of identifiers. The algorithm ensures that all specified nodes are reached in O(log n) time, sending maximum O(log n) messages per node, regardless of the input size of the bulk operation. Moreover, the algorithm avoids sending redundant messages. Previous approaches required multiple lookups, which consume more messages and can render the initiator a bottleneck. Our algorithms are used in DHT-based storage systems, where nodes can do thousands of lookups to fetch large files. We use the bulk operation algorithm to construct a pseudo-reliable broadcast algorithm. Bulk operations can also be used to implement efficient range queries.

    Finally, we describe a novel way to place replicas in a DHT, called symmetric replication, that enables parallel recursive lookups. Parallel lookups are known to reduce latencies. However, costly iterative lookups have previously been used to do parallel lookups. Moreover, joins or leaves only require exchanging O(1) messages, while other schemes require at least log(f) messages for a replication degree of f.

    The algorithms have been implemented in a middleware called the Distributed k-ary System (DKS), which is briefly described.

  • 184.
    Ghodsi, Ali
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Haridi, Seif
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Alima, Luc Onana
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Low-Bandwidth Topology Maintenance for Robustness in Structured Overlay Networks2005In: Proceedings of the Annual Hawaii International Conference on System Sciences, 2005, p. 302-Conference paper (Refereed)
    Abstract [en]

    Structured peer-to-peer systems have emerged as infrastructures for resource sharing in large-scale, distributed, and dynamic environments. One challenge in these systems is to efficiently maintain routing information in the presence of nodes joining, leaving, and failing. Many systems use costly periodic stabilization protocols to ensure that the routing information is up-to-date.In this paper, we present a novel technique called correction-on-change, which identifies and notifies all nodes that have outdated routing information as a result of a node joining, leaving, or failing. Effective failure handling is simplified as the detection of a failure triggers a correction-on-change which updates all the nodes that have a pointer to the failed node. The resulting system has increased robustness as nodes with stale routing information are immediately updated.We proof the correctness of the algorithms and evaluate its performance by means of simulation. Experimental results show that for the same amount of maintenance bandwidth correction-on-change makes the system by far more robust when compared to periodic stabilization. Moreover, compared to adaptive stabilization which adjusts its frequency to the dynamism in the system, correction-on-change gives the same performance but with considerably less maintenance bandwidth. As correction-on-change immediately updates incorrect routing entries the average lookup length is maintained close to the theoretical average in the presence of high dynamism. We show how the technique can be applied to our DKS system as well as the Chord system.

  • 185.
    Ghodsi, Ali
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Huberman, B.
    Wu, F.
    The survival of the unfittest2006Conference paper (Refereed)
    Abstract [en]

    We explore the use of pari-mutuel markets in a peer-to-peer setting to generate a wide diversity of content offerings while responding adaptively to customer demand. Files are served and paid for through a parimutuel market similar to that used for betting in horse races and in lotteries. Our simulations are based on rational agents, which all act according to a set of simple rules. The results show that a favorite-longshot bias occurs, where agents tend to bet on longshots rather than favorites when following simple expected utility maximization. Furthermore, we have confirmed that the long-tail does sustain even when the agents only have a limited view of all files to pick from. If the limited view consists of random subsets of all files, the long tail is enhanced. If the limited view consists of the top most popular items, the long tail slightly decreases. We have also explored the effect of bounded rationality. Our results show that the system is robust in presence of a large fraction of providers that have bounded rationality. If the providers with bounded rationality pick random items, the long tail is enhanced. Conversely, if the providers with bounded rationality only pick their favorite, the long tail slightly decreases.

  • 186.
    Ghorbani, Shaban Reza
    et al.
    Department of Physics, Tarbiat Muallem University of Sabzevar, Iran.
    Andersson, Magnus
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Rapp, Östen
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Disorder Driven Localization in Charge Neutrally Doped 123 Superconductors2006In: Low Temperature Physics / [ed] Takano, Y; Hershfield, SP; Hirschfeld, PJ; Goldman, AM, 2006, Vol. 850, p. 439-440Conference paper (Refereed)
    Abstract [en]

    Charge neutral dopings with equal amounts of CaTh or CaPr on rare earth site in Nd-123 have been investigated by studies of the normal state electrical resistivity, p, the Seebeck coefficient S, and the Hall coefficient R-H. In spite of comparable rates of depression of the superconducting T, significant differences are observed in the doping concentration dependence of p, S, and RH between the two dopings. These results are discussed in terms of disorder induced localization.

  • 187. Ghosh, A. K.
    et al.
    Das, S.
    Roy, R.
    Mukherjee, Amitava
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Sender side intelligence for TCP throughput enhancement in wired-cum-wireless network2007In: 2007 IEEE 18th International Symposium on Personal, Indoor and Mobile Radio Communications: 3-7 September, 2007, Athems, Greece, 2007, p. 4394381-Conference paper (Refereed)
    Abstract [en]

    Performance of the TCP Congestion Control Algorithm has been the focus of research over the last decade. In this paper we propose modifications to TCP Congestion Control to improve its performance in wired-cum-wireless networks The key idea to determine the Optimal Congestion Window for a TCP Sender, in a particular network scenario (that corresponds to the fair share of that connection) and keep this congestion window a constant to a point where the fair share in the network has changed considerably from the instance of the calculation of the size of the last window. At this point, the TCP Congestion Window is recalculated according to the nature of new scenario. The proposed mechanism is particularly effective over wireless links, which have an inherently loss-prone nature, as Modified TCP's congestion window being independent of packet losses (be it corruption losses or it congestion losses), keeps transmitting at the same rate at before.

  • 188. Ghosh, A. K.
    et al.
    Mukherjee, Amitava
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. IBM Global Services India, India.
    Saha, D.
    Some simulation studies to characterize TCP window control behavior in wired/wireless internetworks2005In: 2005 IEEE International Conference on Personal Wireless Communications, IEEE , 2005, p. 545-549Conference paper (Refereed)
    Abstract [en]

    This paper explores the possibility of developing a new variant of TCP, which would be performing equally well under wireless as in wired connections. In order to get this new variant of TCP, this work primarily looks into the behavior of TCP under various loads and error conditions and different window sizes (both variable and fixed), and compares them with TCP Reno. The simulation is carried out in ns simulator.

  • 189. Gilet, Ph.
    et al.
    Pougeoise, E.
    Grenouillet, L.
    Grosse, Ph.
    Olivier, N.
    Poncet, S.
    Chelnokov, A.
    Gerard, J. M.
    Stevens, R.
    Hamelin, R.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Sundgren, Petrus
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    1.3 μm VCSELs: InGaAs/GaAs, GaInNAs/GaAs multiple quantum wells and InAs/GaAs quantum dots- Three candidates as active material2007In: Vertical - Cavity Surface - Emitting Lasers XI, San Jose, CA, 2007, Vol. 6484, p. F4840-F4840Conference paper (Refereed)
    Abstract [en]

    In this article, we report our results on 1.3ÎŒm VCSELs for optical interconnection applications. Room temperature continuous-wave lasing operation is demonstrated for top emitting oxide-confined devices with three different active materials, highly strained InGaAs/GaAs(A) and GalnNAs/GaAs (B) multiple quantum wells (MQW) or InAs/GaAs (C) quantum dots (QD). Conventional epitaxial structures grown respectively by Metal Organic Vapour Phase Epitaxy (MOVPE), Molecular Beam Epitaxy (MBE) and MBE, contain rully doped GaAs/AlGaAs DBRs. All three epilayers are processed in the same way. Current and optical confinement are realized by selective wet oxidation. Circular apertures from 2 ÎŒm to 16 ÎŒm diameters are defined. At room temperature and in continuous wave operation, all three systems exhibit lasing operation at wavelengths above 1 275nm and reached 1 300nm for material (A). Typical threshold currents are in the range [1-10]mA and are strongly dependent firstly on oxide diameter and secondly on temperature. Room temperature cw maximum output power corresponds respectively to 1.77mW, 0.5mW and 0.6mW. By increasing driving current, multimode operation occurs at different level depending on the oxide diameter. In case (A), non conventional modal behaviors will be presented and explained by the presence of specific oxide modes. Thermal behaviors of the different devices have been compared. In case (A) and (C) we obtain a negative T0. We will conclude on the different active materials in terms of performances with respect to 1300nm VCSEL applications.

  • 190.
    Gioacchino Cascella, Roberto
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Reconfigurable Application Networks through Peer Discovery and Handovers2003Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This Master thesis work was carried out at theWireless Center at KTH and it is part of a pilot project. This thesis is conducted for the Institute for Microelectronics and Information Technology (IMIT) at the Royal Institute of Technology (KTH) in Stockholm (Sweden) and for the Department of Telecommunications at Politecnico di Torino in Turin (Italy).

    This thesis addresses an area with significant potential for offering services to mobile users. In such a scenario users should have minimal interaction with applications which, by taking into account available context information, should be able to make decisions, such as setting up delivery paths between peers without requiring a third party for the negotiation.

    In wireless reconfigurable networks, the mobile users are on the move and must deal with dynamic changes of network resources. In such a network, mobile users should be able to contact other peers or resources by using the current route. Thus although manual configuration of the network is a possible solution, it is not easily used because of the dynamic properties of the system which would demand too much user interaction. However, existing discovery protocols fall short of accomodating the complexity of reconfigurable and heterogeneous networks.

    The primary objective of this thesis work was to investigate a new approach at the application level for signaling by taking advantage of SIP’s features. The Session Initiation Protocol (SIP) is used to provide naming and localization of the user, and to provide functionality to invite users to establish sessions and to agree on communication parameters. The Specific Event Notification of the SIP protocol provides a framework for the notification of specific events and I believed that it could be instantiated as solution to the problem for reconfigurable application networks.

    This thesis proposes a method for providing localization information to SIP User Agents in order to establish sessions for service discovery. Furthermore, this method should consider context meta-data to design strategies effective in heterogeneous networks. A viable solution must support (re)location of users at the application layer when they roam between different wireless networks, such as GPRS and WLAN. An analysis of the implications of the proposed model is presented; in this analysis emphasis has been placed on how this model interacts with existing services.

  • 191.
    Glifberg, Fredrik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Optimisation of End-to-End TCP Performance in A UMTS Network2003Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Due to the FEC and ARQ mechanisms in UMTS the wireless part will not introduce loss, but instead introduces latency. This thesis aims to optimize the radio network (RAN) parameters in UMTS affecting TCP and then to optimize the parameters in TCP to perform better in this network.

    The tests have been performed in a live 3G network. A traffic model has been implemented into a client/server allowing us to simulate a UMTS customer in the cell, with which we can test different parameter settings. Radio parameters controlling radio connection supervision, channel switching, and power control’s BLER-target have been examined. Performance has been measured in terms of throughput and cell capacity.

    The results show that we can improve TCP performance by 25% with better static parameter settings. However, the system would be even better with a dynamic approach that would adjust the RAN parameter settings to better match the current load in the cell. In this way the performance/user can be increased significantly and as an example for one user the average throughput given a specific traffic pattern can be increased from 65 kbps up to 300 - 320 kbps.

  • 192.
    Gonzales Prieto, Alberto
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Stadler, Rolf
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Design and Implementation of Performance Policies for SMS Systems2005In: AMBIENT NETWORKS, Berlin: Springer Verlag , 2005, p. 169-180Conference paper (Refereed)
    Abstract [en]

    We present a design for policy-based performance management of SMS Systems. The design takes as input the operator's performance goals, which are expressed as policies that can be adjusted at run-time. In our specific design, an SMS administrator can specify the maximum delay for a message and the maximum percentage of messages that can be postponed during periods of congestion. The system attempts to maximize the overall throughput while adhering to the performance policies. It does so by periodically solving a linear optimization problem that takes as input the policies and traffic statistics and computes a new configuration. We show that the computational cost for solving this problem is low, even for large system configurations. We have evaluated the design through extensive simulations in various scenarios. It has proved effective in achieving the administrator's performance goals and fast in adapting to changing network conditions. A prototype has been developed on a commercial SMS platform, which proves the validity of our design.

  • 193.
    Gonzalez, Delia Rodriguez De Liera
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Ismail, Mohammed
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A programmable baseband chain for a WCDMA/WLAN(802.11b)multi-standard zero-IF receiver2005In: VLSI Circuits and Systems II, Pts 1 and 2 / [ed] Lopez, JF; Fernandez, FV; LopezVillegas, JM; DelaRosa, JM, BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING , 2005, Vol. 5837, p. 396-403Conference paper (Refereed)
    Abstract [en]

    As we move towards convergent 4G Wireless encompassing both 3G cellular (WCDMA) for wide area networks and Wireless LAN for "hot-spots", the development of low power, low cost multi-band multi-standard wireless chipset solutions is a must. To this end this paper presents a programmable architecture for an analog baseband chain intended for use in a zero-IF multi-standard WCDMA/WLAN(802.11b) radio receiver. It also addresses the DC offset cancellation in the baseband chain. This is one of the major impairments in zero-IF receivers whose simplicity makes them suitable for single-chip multi-standard designs but where DC offset can reduce the receiver performance if a proper DC offset cancellation scheme is not devised. System level design of the baseband chain is given leading to design specifications of the different blocks in the chain. Extensive simulations carried out in MATLAB/SimuLink at the system level and in Cadence design tools at the circuit level show the performance of the system. The circuits will be fabricated in a 0.18 mu m CMOS process for a 1.8 V power supply.

  • 194.
    Goobar, E.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Gillner, L.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Broberg, B.
    Tanbun-Ek, T.
    Nilsson, S.
    Measurement of a VPE-transported DFB laser with blue-shifted frequency modulation response from DC to 2 GHz1988In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 24, p. 746-747Article in journal (Refereed)
    Abstract [en]

    The frequency modulation characteristics of a VPE-transported 1.53 mu;m wavelength GaInAsP-InP DFB semiconductor diode laser was measured. Below approximately 0.7 mW optical output power per facet, it exhibited a smooth, blue-shifted, frequency modulation response from DC to 2 GHz. In the modulation frequency range of 10 MHz to 100 MHz it exhibited a | Delta;f/ Delta;I| of 0.5-1.8 GHz/mA, depending on the biasing level

  • 195.
    Goobar, E.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Broadband measurements of frequency noise spectrum in two section DBR laser1991In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 27, p. 289-291Article in journal (Refereed)
    Abstract [en]

    The dependence of the frequency noise on the output power, the tuning current and the current modulation has been measured in a two electrode DBR laser from 30 MHz to 8 GHz. The frequency noise spectrum was fairly flat and decreased with increased output power at a rate faster than 1/P. At certain biasing levels, the noise increased and the relaxation peak was shifted towards lower frequencies when current was injected into the passive waveguide. Furthermore, the frequency noise was not affected by the current modulation.

  • 196.
    Goobar, E.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Broberg, B.
    Nilsson, S.
    Pure frequency modulation or intensity modulation with suppressed frequency chirp using active Bragg reflector integrated laser1989In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 25, p. 304-305Article in journal (Refereed)
    Abstract [en]

    The modulation properties of a laser structure which consists of an active Bragg reflector (300 mu m) integrated with an uncorrugated gain region (600 mu m) have been measured. The laser exhibited a flat FM response and very low spurious intensity modulation when modulating the current in the Bragg reflector. Furthermore, broadband intensity modulation with suppressed frequency chirp could also be achieved. An inhomogeneous linewidth enhancement factor alpha caused by the uneven carrier density distribution between the two sections gives a qualitative explanation to our results.

  • 197.
    Goobar, Edgard
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Rigole, P.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Cross-correlation measurements of intensity noise from the two facets of DFB lasers during linewidth rebroadening1992In: Semiconductor Laser Conference , 1992. Conference Digest. 13th IEEE International, 1992, p. 266-267Conference paper (Refereed)
    Abstract [en]

    Not available

  • 198.
    Goobar, Edgard
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Possibilities of large modulation bandwidth of a directly frequency modulated laser with suppressed intensity modulation1989In: Proceedings of 15th European Conference of Optical Communication, 1989Conference paper (Refereed)
  • 199.
    Gorniak, Richard J.
    et al.
    New York University.
    Kramer, Elissa L.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Schettino, C. J.
    New York University, Department of Radiology.
    Zeleznik, Michael P.
    Saya Systems Inc., Salt Lake City, UT, USA.
    Evaluation of a Semi-Automatic 3D Fusion Technique Applied to Thallium-201 SPECT and MRI Brain/Frame Volume Data Sets2001In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 28, no 8, p. 1190-Article in journal (Refereed)
  • 200.
    Grishin, Alexander
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Mays, Ramos
    Method of interrogating a barcode2004Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    Presented is a system and method for reading a microwave readable barcode formed from a pattern of dielectric material. The dielectric pattern creates a strong microwave contrast with the surrounding media selectively resonating with or scattering an interrogating microwave signal. Dielectric bars can be fabricated by inkjet printing, injection, spraying, drawing or any other technique. Barcode information is encoded using different lengths, angles, or positions of dielectric bars. A microwave readable dielectric barcode system includes a barcode fabricated from a dielectric material, a transmitter with an antenna, and a sensor that senses the effect produced by the dielectric barcode on the microwave signal. The dielectric barcode system can use multiple microwave signals that differ in one or more respects, such as polarization or frequency.

1234567 151 - 200 of 741
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf