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  • 51. Abeywickrama, S.
    et al.
    Wong, E.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Energy-efficient survivability for core networks using dual-homing2015In: Asia Communications and Photonics Conference, ACPC 2015, 2015Conference paper (Refereed)
    Abstract [en]

    This paper studies the energy efficiency of exploiting dual-homing in access network to provide core network survivability. Simulation results show reduced number of utilized wavelengths, suggesting significant energy saving opportunities in the core network. © 2015 OSA.

  • 52. Abeywickrama, Sandu
    et al.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wong, Elaine
    Protecting core networks with dual-homing: A study on enhanced network availability, resource efficiency, and energy-savings2016In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 381, p. 327-335Article in journal (Refereed)
    Abstract [en]

    Core network survivability affects the reliability performance of telecommunication networks and remains one of the most important network design considerations. This paper critically examines the benefits arising from utilizing dual-homing in the optical access networks to provide resource-efficient protection against link and node failures in the optical core segment. Four novel, heuristic-based RWA algorithms that provide dedicated path protection in networks with dual-homing are proposed and studied. These algorithms protect against different failure scenarios (i.e. single link or node failures) and are implemented with different optimization objectives (i.e., minimization of wavelength usage and path length). Results obtained through simulations and comparison with baseline architectures indicate that exploiting dual-homed architecture in the access segment can bring significant improvements in terms of core network resource usage, connection availability, and power consumption.

  • 53.
    Abid, Muhammad Zeeshan
    KTH, School of Information and Communication Technology (ICT). Technische Universität Braunschweig.
    A Multi-leader Approach to Byzantine Fault Tolerance: Achieving Higher Throughput Using Concurrent Consensus2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Byzantine Fault Tolerant protocols are complicated and hard to implement.Today’s software industry is reluctant to adopt these protocols because of thehigh overhead of message exchange in the agreement phase and the high resourceconsumption necessary to tolerate faults (as 3 f + 1 replicas are required totolerate f faults). Moreover, total ordering of messages is needed by mostclassical protocols to provide strong consistency in both agreement and executionphases. Research has improved throughput of the execution phase by introducingconcurrency using modern multicore infrastructures in recent years. However,improvements to the agreement phase remains an open area.

    Byzantine Fault Tolerant systems use State Machine Replication to tolerate awide range of faults. The approach uses leader based consensus algorithms for thedeterministic execution of service on all replicas to make sure all correct replicasreach same state. For this purpose, several algorithms have been proposed toprovide total ordering of messages through an elected leader. Usually, a singleleader is considered to be a bottleneck as it cannot provide the desired throughputfor real-time software services. In order to achieve a higher throughput there is aneed for a solution which can execute multiple consensus rounds concurrently.

    We present a solution that enables multiple consensus rounds in parallel bychoosing multiple leaders. By enabling concurrent consensus, our approach canexecute several requests in parallel. In our approach we incorporate applicationspecific knowledge to split the total order of events into multiple partial orderswhich are causally consistent in order to ensure safety. Furthermore, a dependencycheck is required for every client request before it is assigned to a particular leaderfor agreement. This methodology relies on optimistic prediction of dependenciesto provide higher throughput. We also propose a solution to correct the course ofexecution without rollbacking if dependencies were wrongly predicted.

    Our evaluation shows that in normal cases this approach can achieve upto 100% higher throughput than conventional approaches for large numbers ofclients. We also show that this approach has the potential to perform better incomplex scenarios

  • 54.
    Abolafya, Natan
    KTH, School of Information and Communication Technology (ICT).
    Secure Documents Sharing System for Cloud Environments2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the current trend of cloud services available in every market area in IT business, it is somewhat surprising that security services are not migrated to the cloud widely. Security as a Service (SECaaS) model is hardly popular at the moment even though the infrastructure of the cloud, or web, can support most of the functionalities of conventional distributed security services.

    Another uncommon phenomenon in the cloud is sharing secure files with multi-tenant support. This kind of service would be best available integrated with a SECaaS platform that may offer more similar application services. This thesis proposes, studies, designs, develops and evaluates a Secure Documents Sharing System for Cloud Environment with the possibility of integrating to a SECaaS platform.

  • 55.
    Abtahi, Farzad
    KTH, School of Information and Communication Technology (ICT).
    Optimal Design of Cost- and Energy-Efficient ScalablePassive Optical Backbone Networks2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Advances in optical coherent transmissions and electrical compensation technologies have stimulated the exploration of novel optical network architectures. Filterless optical backbone networks (F-OBNs) eliminate or minimize the usage of active photonic reconfigurable components, which is also referred to as passive OBN. By introducing passive splitters and combiners to interconnect the fiber links, this type of networks have been proposed as a cost- and energy-efficient alternative to active optical switching networks.

    However, F-OBN suffers from a constraint on wavelength reuse due to its broadcast nature. Consequently, this architecture always requires more resources, i.e. higher number of wavelengths, than the active optical switching networks. To address this issue, another passive approach for optical core network, i.e., semi-filterless OBN (SF-OBN) has been introduced. By utilizing passive colored components, e.g., Fiber Bragg Grating (FBG), red/blue filters, etc., at some selected nodes, the SF-OBN is able to improve the wavelength usage while keeping the similar level on cost and energy consumption as FOBN. In this thesis project, an optimization model for wavelength assignment and filter placement in SF-OBN has been developed. F-OBN can be considered as a special case without any filter in SF-OBN. Using integer linear programming (ILP) formulation, the model aims to minimize the total number of wavelengths required in the network given the number of filters.

    Furthermore, wavelength usage, cost and energy consumption in active optical switching, F-OBN and SF-OBN have been compared in order to evaluate the performance of the each network architecture.

  • 56.
    Abtahi, Farzad
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Khanmohamadi, Sahar
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Mantelet, G.
    Archambault, E.
    Tremblay, C.
    Bélanger, M. P.
    Optimal Design of Cost- and Energy-Efficient Scalable Passive Optical Backbone Networks2012In: 2012 Asia Communications And Photonics Conference (ACP), 2012, p. AS3D.4-Conference paper (Refereed)
    Abstract [en]

    We propose an optimization model minimizing number of wavelengths in passive optical backbone networks and obtaining the same resource usage as in networks based on active switching while reducing both cost and power consumption.

  • 57. Achanta, S.
    et al.
    Feuerbacher, M.
    Grishin, Alexander
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Ye, X.
    Celis, J. -P
    On the mechanical and tribological behavior of Al3Mg2 complex metallic alloys as bulk material and as coating2010In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 18, no 11, p. 2096-2104Article in journal (Refereed)
    Abstract [en]

    New materials with tunable physical, mechanical, chemical, and thermal properties are attractive for many applications and stand as prospective substitutes for the existing engineering materials. In that respect, complex metallic alloys (CMA) have recently demonstrated promising traits where a myriad of physical, mechanical, chemical properties can be obtained by altering the structure. CMA's have a large crystal size with thousands of atoms per unit cell. In this work, some mechanical properties and tribological behavior of Al3Mg2 based CMA are discussed. The surface characterization, deformation mode, mechanical and tribological properties of bulk and thin film Al3Mg2 materials are investigated, and compared with existing engineering materials. The results revealed a contrasting tribological behavior of Al3Mg2 when used as either bulk material or as coating. Al3Mg2 coatings act as a low friction solid lubricant under certain conditions, with a coefficient of friction comparable to that of diamond-like carbon coatings. It is suggested that the quasi-crystalline nature of Al3Mg2-coatings renders the surface stiff and that the characteristics of the wear debris generated are responsible for the low friction behavior.

  • 58. Achtziger, N
    et al.
    Grillenberger, J
    Witthuhn, W
    Linnarsson, M K
    KTH, School of Information and Communication Technology (ICT).
    Janson, M S
    Svensson, B G
    Hydrogen passivation of silicon carbide by low-energy ion implantation1998In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 73, p. 945-947Article in journal (Refereed)
    Abstract [en]

    implantation of deuterium is performed to investigate the mobility and passivating effect of hydrogen in epitaxial alpha-SiC (polytypes 4H and 6H). To avoid excessive damage and the resulting trapping of hydrogen, the implantation is performed with low energy (600 eV H-2(2)+). The H-2 depth profile is analyzed by secondary ion mass spectrometry. Electrical properties are measured by capacitance-voltage profiling and admittance spectroscopy. In p-type SIG, hydrogen diffuses on a mu m scale even at room temperature and effectively passivates accepters. In n-type SiC, the incorporation of H is suppressed and no passivation is detected. (C) 1998 American Institute of Physics.

  • 59. Achtziger, N
    et al.
    Hulsen, C
    Janson, M
    Linnarsson, M K
    KTH, School of Information and Communication Technology (ICT).
    Svensson, B G
    Witthuhn, W
    Formation of passivated layers in p-type SiC by low energy ion implantation of hydrogen2000In: SILICON CARBIDE AND RELATED MATERIALS - 1999 PTS, 1 & 2, 2000, Vol. 338-3, p. 933-936Conference paper (Refereed)
    Abstract [en]

    The mobility of hydrogen and its passivating effect on accepters in p-type SiC is investigated. Hydrogen (isotope H-1 or H-2 alternatively) is implanted at temperatures between 300 K and 680 K with low energy (300 eV per atom) in order to minimize implantation damage. The depth profiles of 2H and of passivated accepters correspond closely. Up to 500 K, a fully passivated layer with a well defined thickness is formed. Its depth ton the order of 1 micrometer) is investigated as a function of doping level and hydrogen fluence. At higher temperatures, the incorporation drastically increases, but the electrical passivation is partial only. Qualitative explanations are given.

  • 60. Achtziger, N
    et al.
    Hulsen, C
    Witthuhn, W
    Linnarsson, M K
    KTH, School of Information and Communication Technology (ICT).
    Janson, M
    Svensson, B G
    Mobility passivating effect and thermal stability of hydrogen in silicon carbide1998In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 210, p. 395-399Article in journal (Refereed)
    Abstract [en]

    The diffusion and passivating effect of hydrogen (isotope H-2) in epitaxial p-type SiC is studied by secondary ion mass spectrometry and capacitance-voltage profiling on Schottky diodes. The incorporation of hydrogen is achieved by low-energy ion implantation. The influence of implantation energy, temperature and subsequent annealing is presented. Annealing experiments with an electric field applied reveal a reactivation of passivated accepters and a H+ ion drift at a surprisingly low temperature of 530 K.

  • 61.
    Adam, Constantin
    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.
    A Middleware Design for Large-scale Clusters offering Multiple Services2006In: IEEE Transactions on Network and Service Management, ISSN 1932-4537, E-ISSN 1932-4537, Vol. 3, no 1, p. 1-12Article in journal (Refereed)
    Abstract [en]

    We present a decentralized design that dynamically allocates resources to multiple services inside a global server cluster. The design supports QoS objectives (maximum response time and maximum loss rate) for each service. A system administrator can modify policies that assign relative importance to services and, in this way, control the resource allocation process. Distinctive features of our design are the use of an epidemic protocol to disseminate state and control information, as well as the decentralized evaluation of utility functions to control resource partitioning among services. Simulation results show that the system operates both effectively and efficiently; it meets the QoS objectives and dynamically adapts to load changes and to failures. In case of overload, the service quality degrades gracefully, controlled by the cluster policies.

  • 62.
    Adam, Constantin
    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.
    Adaptable Server Clusters with QoS Objectives2005In: Integrated Network Management IX - MANAGING NEW NETWORKED WORLDS / [ed] Clemm A, Festor O, Pras A, New York: IEEE , 2005, p. 149-163Conference paper (Refereed)
    Abstract [en]

    We present a decentralized design for a server cluster that supports a single service with response time guarantees. Three distributed mechanisms represent the key elements of our design. Topology construction maintains a dynamic overlay of cluster nodes. Request routing directs service requests towards available servers. Membership control allocates/releases servers to/from the cluster, in response to changes in the external load. We advocate a decentralized approach, because it is scalable, fault-tolerant, and has a lower configuration complexity than a centralized solution. We demonstrate through simulations that our system operates efficiently by comparing it to an ideal centralized system. In addition, we show that our system rapidly adapts to changing load. We found that the interaction of the various mechanisms in the system leads to desirable global properties. More precisely, for a fixed connectivity c (i.e., the number of neighbors of a node in the overlay), the average experienced delay in the cluster is independent of the external load. In addition, increasing c increases the average delay but decreases the system size for a given load. Consequently, the cluster administrator can use c as a management parameter that permits control of the tradeoff between a small system size and a small experienced delay for the service.

  • 63.
    Adam, Constantin
    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.
    Externally Controllable, Self-Oganizing Server Clusters2005In: Designing a Scalable, Self-organizing Middleware for Server Clusters (NGNM05): in the scope of Networking 2005, 2005, p. 1-12Chapter in book (Other academic)
  • 64.
    Adamopoulos, Othon
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Björkman, Eva
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Zhang, Yu
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Functional Materials, FNM (Closed 20120101).
    Bog, Tassilo
    Mussmann, Lothar
    Lox, Egbert
    A nanophase oxygen storage material: Alumina-coated metal-based ceria2009In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 29, no 4, p. 677-689Article in journal (Refereed)
    Abstract [en]

    Nanoparticles of Ce1-xMxO2-delta (M = Ca or Zr) coated with Al2O3 with average crystallite size of 10 nm have been synthesised via solution chemistry approach under controlled chemical and hydrodynamic conditions. Their synthesis has been accomplished in three major steps: (1) simultaneous co-precipitation of cations, (2) sequential precipitation of Al(OH)(3) over the former particles and (3) calcination of the precipitated precursors to the corresponding oxides. Several compositions have been synthesised and their physicochemical properties are compared with commercial state-of-the-art material. The Al2O3-coating hinders the particles growth at high temperatures, resulting in materials with a large specific surface area and a restrain in the decrease of their oxygen storage capacity.

  • 65.
    Adigozalov, Niyaz
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    The Intelligent Use of Multiple Interfaces: Using multiplexing to reduce the overhead for small packets2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Long-Term Evolution (LTE) is the latest development in wide area cellular mobile network technology. In contrast with the earlier generations of circuit-switched mobile networks, LTE is all-IP packet-switched network. Both voice and data are sent inside IP packets. Voice over IP (VoIP) is used to provide voice service to LTE users. The speech frames are encapsulated into real-time protocol (RTP) packets and sent over the network. The underlying UDP and IP layers prepend their headers to this small RTP packet resulting in a relatively high overhead. The small size of the RTP packets containing voice/audio leads to an overhead problem as the protocol overhead is in addition to the large LTE frame overhead, thus wasting network resources. This master’s thesis project proposes to multiplex RTP and data packets at the user’s device as a solution to reduce the overhead. Moreover, the capability of modern user devices to switch between several interfaces (such as LTE and WLAN), is taken into account and the multiplexing of multiple traffic flows or a single traffic flow are studied in the case of a vertical handover. Performance and cost metrics are used to evaluate different potential demultiplexing points, and then the best possible demultiplexing point is identified. The results of this evaluation show that several demultiplexing points can be used based on the operator’s needs. The increased packet payload size increases the energy efficiency of LTE and may avoid the need of the UE to switch to WLAN to save power. In addition, to ensure high quality of service for VoIP traffic, the simultaneous use of multiple interfaces is efficient if the multiplexer is enabled. The multiplexing solution proposed by this thesis is also fully compatible with any virtual private network encapsulation protocol.

  • 66.
    Adikari, Jithra
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Efficient non-repudiation for techno-information environment2006In: 2006 International Conference on Industrial and Information Systems, Vols 1 and 2, NEW YORK: IEEE , 2006, p. 454-458Conference paper (Refereed)
    Abstract [en]

    Non-repudiation means that a person is unable to deny a certain action that he has done under any circumstances. There are several mechanisms, standards and protocols to achieve non-repudiation in techno-information enviromnent. However efficiency in non-repudiation in legal framework was not considerably addressed within the context of those mechanisms. Lack of efficient non-repudiation in the legal framework for techno-information environment makes legal issues when evidence is generated maintained. It can be derived that traditional non-repudiation mechanism delivers efficient non-repudiation. Efficient non-repudiation in techno-information environment is achieved by mapping traditional non-repudiation. Evaluation methodology for efficiency of non-repudiation mechanisms has been improved during this work. Further most significant finding of this research is the Efficient Non-Repudiation Protocol.

  • 67.
    Adnan, Muhammad
    KTH, School of Information and Communication Technology (ICT).
    QoS Analysis for Signaling in VoIP Client and Server Communication for Multicore2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Due to the cost-effective solutions provided by Voice over Internet Protocol (VoIP) technology to enterprises and individuals, the growth has been significantly high in this area during the past and current decade. The growing demand has resulted in the escalating number of users who need secure, reliable and efficient communication systems. The deployment of multicore hardware has been solving the computational complexity problems. A multicore hardware/software model for VoIP is the key research area of modern telecommunications. One of the challenges is to design and implement a Quality of Service (QoS) benchmark module for multicore VoIP client and server environment. To achieve this we need a benchmarking module to quantitatively analyze QoS parameters namely delay and packet loss, and to further analyze these parameters with security overhead. In this project we have designed and implemented a prototype for a customized network traffic generator called SQgen, keeping in consideration the parallel nature of hardware and software in VoIP communication.

    The research focus area is to test the performance of signaling protocol for call set up process. Session Initiation Protocol (SIP) is widely deployed protocol for call establishment, maintenance and termination in VoIP, and we measure the performance of an open source implementation of SIP. Using SQgen, a series of stress tests are performed in different network scenarios to analyze the performance, and investigate the reasons for delays in different parts of the call setup process.

  • 68.
    Adnan, Muhammad Wasif
    KTH, School of Information and Communication Technology (ICT).
    Implementation of an FPGA based Emulator for High Speed Power Electronic Systems2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During development of control systems for power electronic systems, it is desirable to test the controller in real-time, by interfacing it with an emulator device. In this context, this work comprises the development of an emulator that can model accurately the dynamics of high speed power electronic systems and provides interfaces that are compatible with the real hardware. The realtime state calculations, based on discrete models, were performed on custom logic, implemented on an FPGA. The realized system allows to emulate Linear Parameter Varying (LPV) systems, achieving sampling rates up to 12MHz using a low cost Xilinx FPGA. As a result, power electronic systems with very high switching frequencies can be modeled. In addition, the FPGA incorporates a soft-core processor that allows a designer to easily re-configure the system model through software. The emulator system has been validated for a multiphase DC-DC converter, by comparing its results with the real hardware setup.

  • 69.
    Adolfsson, Fredrik
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Johansson, Tobias
    KTH, School of Information and Communication Technology (ICT).
    Grafisk visualisering av små fiberoptiska nätverk2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    To graphically visualize small fiber optic networks, in a simple and clear way, can be problematic. The information presented in a graph must not be superfluous nor lacking. The purpose of this report is to present what should be considered when creating graphical visualizations, which refers to layout structure, color and shape. The work was conducted through a literature study, collecting information regarding different types of visualizations. With the help of the information solutions about the graph structure and component appearance were discussed and through this a prototype was built. Based on the creation of the prototype an implementation in JavaScript was performed. The result of the appearance, that the implementation generates, results in the recommended layout for visualization of small fiber optic network.

    The report is divided into the parts: a literature study, the development of the prototype, deciding the JavaScript library to use and finally the implementation of the prototype. The result is a graph based on orthogonal and hierarchy layout where symmetry was pursued. The components are distinguished, among other things, by unique shapes and colors.

    One of the conclusions that is drawn is that the developed visualization is a suitable alternative to visualize a small fiber optic network. To say that it is the obvious alternative is not possible without any kind of study based on interaction between users and the visualization.

  • 70.
    af Sandeberg, Joakim
    KTH, School of Information and Communication Technology (ICT).
    Graphical system visualization and flow display: A visual representation of an authentication, authorization, and accounting backend2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Displaying the architecture of a software system is not a simple task. Showing all of the available information will unnecessarily complicate the view, while showing too little might render the view unhelpful. Furthermore, showing the dynamics of the operation of such a system is even more challenging.

    This thesis project describes the development of a graphical tool that can both display the configuration of an advanced authentication, authorization, and accounting (AAA) system and the messages passed between nodes in the system.  The solution described uses force-based graph layouts coupled with adaptive filters as well as vector-based rendering to deliver a view of the status of the system. Force-based layout spreads out the nodes in an adaptive fashion. The adaptive filters starts by showing what is most often the most relevant information, but can be configured by the user. Finally, the vector based rendering offers unlimited zoom into the individual nodes in the graph in order to display additional detailed information.

    Unified Modeling Language (UML) sequence charts are used to display the message flow inside the system (both between nodes and inside individual nodes).

    To validate the results of this thesis project each iteration of the design was evaluated through meetings with the staff at Aptilo Networks. These meetings provided feedback on the direction the project was taking as well as provided input (such as ideas for features to implement).

    The result of this thesis project shows a way to display the status of an AAA system with multiple properties displayed at the same time. It combines this with a view of the flow of messages and application of policies in the network via a dynamically generated UML sequence diagram. As a result human operators are able to see both the system’s architecture and the dynamics of its operation using the same user interface. This integrated view should enable more effective management of the AAA system and facilitate responding to problems and attacks.

  • 71.
    af Sandeberg, Jonas
    KTH, School of Information and Communication Technology (ICT).
    Speeding Up Value at Risk Calculations Using Accelerators2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Calculating Value at Risk (VaR) can be a time consuming task. Therefore it is of interest to find a way to parallelize this calculation to increase performance. Based on a system built in Java, which hardware is best suited for these calculations?

    This thesis aims to find which kind of processing unit that gives optimal performance when calculating scenario based VaR. First the differences of the CPU, GPU and coprocessor is examined in a theoretical study. Then multiple versions of a parallel VaR algorithm are implemented for a CPU, a GPU and a coprocessor trying to make use of the findings from the theoretical study.

    The performance and ease of programming for each version is evaluated and analyzed. By running performance tests it is found that the CPU was the winner when coming to performance while running the chosen VaR algorithm and problem sizes.

  • 72.
    Afrasiabi, Roodabeh
    KTH, School of Information and Communication Technology (ICT).
    Hysteresis and Time-delay in the pH Response of Al2O3 and SiO2-gated Silicon Nanoribbon FET SensorsManuscript (preprint) (Other academic)
    Abstract [en]

    The conventional ion-sensitive field-effect transistor (ISFET) with SiO2 as the insulator of choice has been used as an electrochemical sensor to measure ion concentrations in solutions for many decades. With the ongoing progress in use of silicon nanoribbon (SiNR) FET sensors for fast reliable sensing and the recent demand for pH-sensing technologies in biological applications, it is important to identify the true pH response of the device. However, it has become much more difficult to achieve reliable results across a broad range of pH using SiO2-gated SiNR FET sensors and limitations such as long term drift and hysteresis (also referred to as memory effects) during pH measurements need to be addressed. In this work, we have investigated the electrochemical pH response behavior of silicon oxide-gated SiNR FET sensors and compared it with similar devices (same NR size) but with Al2O3 as the gate oxide. Our studies show that devices passivated with SiO2 show a large hysteresis in the pH response both in acidic and in basic direction, whereas Al2O3 surfaces show slight hysteresis and only in the acidic pH range. Furthermore, in case of SiO2, the total response-time after a pH change appears to be a combination of a fast transient and a slow drift which is related both to the type of oxide and the concentration of the background electrolyte. Consequently, to minimize errors in pH measurements caused by hysteresis and delayed response, we advise performing the measurements at low ionic concentrations and preferably to replace SiO2 by Al2O3 as the gate oxide. In biological applications, we also recommend the integration of an on-chip reference nanoribbon FET for real-time monitoring of problems such as long-term drift and slow response.

  • 73.
    Afrasiabi, Roodabeh
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Silicon Nanoribbon FET Sensors: Fabrication, Surface Modification and Microfluidic Integration2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Over the past decade, the field of medical diagnostics has seen an incredible amount of research towards the integration of one-dimensional nanostructures such as carbon nanotubes, metallic and semiconducting nanowires and nanoribbons for a variety of bio-applications. Among the mentioned one-dimensional structures, silicon nanoribbon (SiNR) field-effect transistors (FET) as electro-chemical nanosensors hold particular promise for label-free, real-time and sensitive detection of biomolecules using affinity-based detection. In SiNR FET sensors, electrical transport is primarily along the nanoribbon axis in a thin sheet (< 30 nm) serving as the channel. High sensitivity is achieved because of the large surface-to-volume ratio which allows analytes to bind anywhere along the NR affecting the entire conductivity by their surface charge. Unfortunately, sensitivity without selectivity is still an ongoing issue and this thesis aims at addressing the detection challenges and further proposing effective developments, such as parallel and multiple detection through using individually functionalized SiNRs.We present here a comprehensive study on design, fabrication, operation and device performance parameters for the next generation of SiNR FET sensors towards multiplexed, label-free detection of biomolecules using an on-chip microfluidic layer which is based on a highly cross-linked epoxy. We first study the sensitivity of different NR dimensions followed by analysis of the drift and hysteresis effects. We have also addressed two types of gate oxides (namely SiO2 and Al2O3) which are commonly used in standard CMOS fabrication of ISFETs (Ion sensitive FET). Not only have we studied and compared the hysteresis and response-time effects in the mentioned two types of oxides but we have also suggested a new integrated on-chip reference nanoribbon/microfluidics combination to monitor the long-term drift in the SiNR FET nanosensors. Our results show that compared to Al2O3, silicon-oxide gated SiNR FET sensors show high hysteresis and slow-response which limit their performance only to background electrolytes with low ionic strength. Al2O3 on the other hand proves more promising as the gate-oxide of choice for use in nanosensors. We have also illustrated that the new integrated sensor NR/Reference NR can be utilized for real-time monitoring of the above studied sources of error during pH-sensing. Furthermore, we have introduced a new surface silanization (using 3-aminopropyltriethoxysilane) method utilizing microwave-assisted heating which compared to conventional heating, yields an amino-terminated monolayer with high surface coverage on the oxide surface of the nanoribbons. A highly uniform and dense monolayer not only reduces the pH sensitivity of the bare-silicon oxide surface in a physiological media but also allows for more receptors to be immobilized on the surface. Protocols for surface functionalization and biomolecule immobilization were evaluated using model systems. Selective spotting of receptor molecules can be used to achieve localized functionalization of individual SiNRs, opening up opportunities for multiplexed detection of analytes.Additionally, we present here a novel approach by integrating droplet-based microfluidics with the SiNR FET sensors. Using the new system we are able to successfully detect trains of droplets with various pH values. The integrated system enables a wide range of label-free biochemical and macromolecule sensing applications based on detection of biological events such as enzyme-substrate interactions within the droplets.

  • 74.
    Afrasiabi, Roodabeh
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Jokilaakso, Nima
    KTH, School of Biotechnology (BIO).
    Localized Functionalization and Integration with Microfluidics for Multiplexed Biomolecule Detection using Silicon Nanoribbon-FET SensorsManuscript (preprint) (Other academic)
    Abstract [en]

    Biological processes causing different medical conditions are seldom characterized by the simple presence or absence of a single biomarker molecule and it can be expected that biosensors with options for multiplexed detection of a panel of analytes will be required for the development of bed-side diagnostic/prognostic tools for personalized healthcare. One sensor technology with potential to be used for label-free detection of biomolecules is based on Silicon Nanoribbon Field-Effect Transistors (SiNR FET). In this study, the possibilities for multiplexed detection of biomolecules have been explored by the integration of a SiNR FET device with a microfluidic system, in combination with localized immobilization of receptor molecules using a microdispensing instrument. SiNR FET devices were fabricated using CMOS technology and integrated with a microfluidic delivery system composed of channels defined in an SU-8 layer, covered with a PDMS lid. Switching between buffer solutions of different pH was used to demonstrate that the microfluidic system could be used for controlled sample delivery. The shift in conductance of the sensing wire upon change of pH showed that the SiNR FET devices were functional. Protocols for surface functionalization and biomolecule immobilization were evaluated using model systems based on synthetic complementary DNA oligonucleotides and the protein A-derived Z domain and its interaction with immunoglobulin G. The study demonstrates that localized immobilization of biomolecules on silicon nanoribbons can be achieved, opening up for multiplexed detection of analytes and improved possibilities for referencing.

  • 75.
    Afrasiabi, Roodabeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Jokilaakso, Nima
    KTH, School of Biotechnology (BIO), Protein Technology.
    Schmidt, Torsten
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Björk, P.
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Effect of microwave-assisted silanization on sensing properties of silicon nanoribbon FETs2015In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 209, p. 586-595Article in journal (Refereed)
    Abstract [en]

    An important concern with using silicon nanoribbon field-effect transistors (SiNR FET) for ion-sensing is the pH-response of the gate oxide surface. Depending on the application of the FET sensor, this response has to be chemically manipulated. Thus in silicon oxide-gated pH-sensors with integrated sensor and reference FETS, a surface with high pH-sensitivity, compared to the bare gate oxide, is required in the sensor FETs (SEFET), whereas in the reference FETs (REFET) the surface has to be relatively pH-insensitive. In order to control the sensitivity and chemistry of the oxide surface of the nanoribbons, a silanization reagent with a functional group is often self-assembled on the SiNR surface. Choice of a silanization reaction that results in a self-assembled layer on a silicon oxide surface has been studied extensively over the past decades. However, the effect of various self-assembled layers such as monolayers or mixed layers on the electrical response of SiNR FETs in aqueous solution needs to be exploited further, especially for future integrated SEFET/REFET systems. In this work, we have performed a comprehensive study on 3-aminopropyltriethoxysilane (APTES) silanization of silicon oxide surfaces using microwave (MW) heating as a new biocompatible route to conventional methods. A set of complementary surface characterization techniques (ellipsometry, AFM and ATR-FTIR) was used to analyze the properties of the APTES layer deposited on the silicon surface. We have found that a uniform monolayer can be achieved within 10 min by heating the silanization solution to 75 degrees C using MW heating. Furthermore, electrical measurements suggest that little change in device performance is observed after exposure to MW irradiation. Real-time pH measurements indicate that a uniform APTES monolayer not only reduces the pH sensitivity of SiNR FET by passivating the surface silanol groups, but also makes the device less sensitive to cation concentration in the background electrolyte. Our silanization route proves promising for future chemical surface modification of on-chip REFETs.

  • 76.
    Afrasiabi, Roodabeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Jokilaakso, Nima
    KTH, School of Biotechnology (BIO), Protein Technology.
    Schmidt, Torsten
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Microwave-assisted silanization of SiNW-FET: characterization and effect on sensing propertiesManuscript (preprint) (Other academic)
  • 77.
    Afrasiabi, Roodabeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Sugunan, Abhilash
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Shahid, Robina
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Microwave mediated synthesis of semiconductor quantum dots2012In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 9, no 7, p. 1551-1556Article in journal (Refereed)
    Abstract [en]

    Colloidal quantum dots (QD) have tuneable optoelectronic properties and can be easily handled by simple solution processing techniques, making them very attractive for a wide range of applications. Over the past decade synthesis of morphology controlled high quality (crystalline, monodisperse) colloidal QDs by thermal decomposition of organometallic precursors has matured and is well studied. Recently, synthesis of colloidal QDs by microwave irradiation as heating source is being studied due to the inherently different mechanisms of heat transfer, when compared to solvent convection based heating. Under microwave irradiation, polar precursor molecules directly absorb the microwave energy and heat up more efficiently. Here we report synthesis of colloidal II-VI semiconductor QDs (CdS, CdSe, CdTe) by microwave irradiation and compare it with conventional synthesis based on convection heating. Our findings show that QD synthesis by microwave heating is more efficient and the chalcogenide precursor strongly absorbs the microwave radiation shortening the reaction time and giving a high reaction yield.

  • 78.
    Afrasiabi, Roodabeh
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Söderberg, Lovisa
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Jönsson, Håkan
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Nano Biotechnology.
    Björk, Per
    Andersson-Svahn, Helene
    KTH, School of Biotechnology (BIO), Nano Biotechnology (closed 20130101).
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Integration of a Droplet-Based Microfluidic System and Silicon Nanoribbon FET Sensor2016In: Micromachines, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 7, no 134Article in journal (Refereed)
    Abstract [en]

    We present a novel microfluidic system that integrates droplet microfluidics with a silicon nanoribbon field-effect transistor (SiNR FET), and utilize this integrated system to sense differences in pH. The device allows for selective droplet transfer to a continuous water phase, actuated by dielectrophoresis, and subsequent detection of the pH level in the retrieved droplets by SiNR FETs on an electrical sensor chip. The integrated microfluidic system demonstrates a label-free detection method for droplet microfluidics, presenting an alternative to optical fluorescence detection. In this work, we were able to differentiate between droplet trains of one pH-unit difference. The pH-based detection method in our integrated system has the potential to be utilized in the detection of biochemical reactions that induce a pH-shift in the droplets.

  • 79.
    Afrasiabi, Roodabeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Söderberg, Lovisa M.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Joensson, Haakan N.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Björk, Per
    Svahn Andersson, Helene
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Integration of a Droplet-Based Microfluidic System and Silicon Nanoribbon FET Sensor2016In: Micromachines, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 7, no 8Article in journal (Refereed)
    Abstract [en]

    We present a novel microfluidic system that integrates droplet microfluidics with a silicon nanoribbon field-effect transistor (SiNR FET), and utilize this integrated system to sense differences in pH. The device allows for selective droplet transfer to a continuous water phase, actuated by dielectrophoresis, and subsequent detection of the pH level in the retrieved droplets by SiNR FETs on an electrical sensor chip. The integrated microfluidic system demonstrates a label-free detection method for droplet microfluidics, presenting an alternative to optical fluorescence detection. In this work, we were able to differentiate between droplet trains of one pH-unit difference. The pH-based detection method in our integrated system has the potential to be utilized in the detection of biochemical reactions that induce a pH-shift in the droplets.

  • 80.
    Afzal, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Wang, Baoyuan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Xia, Chen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Zhang, Wei
    He, Yunjuan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Jayasuriya, Jeevan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Zhu, Binzhu
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fabrication of novel electrolyte-layer free fuel cell with semi-ionic conductor (Ba0.5Sr0.5Co0.8Fe0.2O3-delta- Sm0.2Ce0.8O1.9) and Schottky barrier2016In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 328, p. 136-142Article in journal (Refereed)
    Abstract [en]

    Perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) is synthesized via a chemical co-precipitation technique for a low temperature solid oxide fuel cell (LTSOFC) (300-600 degrees C) and electrolyte-layer free fuel cell (EFFC) in a comprehensive study. The EFFC with a homogeneous mixture of samarium doped ceria (SDC): BSCF (60%:40% by weight) which is rather similar to the cathode (SDC: BSCF in 50%:50% by weight) used for a three layer SOFC demonstrates peak power densities up to 655 mW/cm(2), while a three layer (anode/ electrolyte/cathode) SOFC has reached only 425 mW/cm(2) at 550 degrees C. Chemical phase, crystal structure and morphology of the as-prepared sample are characterized by X-ray diffraction and field emission scanning electron microscopy coupled with energy dispersive spectroscopy. The electrochemical performances of 3-layer SOFC and EFFC are studied by electrochemical impedance spectroscopy (EIS). As-prepared BSCF has exhibited a maximum conductivity above 300 S/cm at 550 degrees C. High performance of the EFFC device corresponds to a balanced combination between ionic and electronic (holes) conduction characteristic. The Schottky barrier prevents the EFFC from the electronic short circuiting problem which also enhances power output. The results provide a new way to produce highly effective cathode materials for LTSOFC and semiconductor designs for EFFC functions using a semiconducting-ionic material.

  • 81.
    Afzal, Usman
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Islam, Md. Mustakimul
    KTH, School of Information and Communication Technology (ICT).
    Meven: An Enterprise Trust Recommender System2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Growing an online community takes time and effort. Relationships in an online community must be initiated based on trust followed by privacy, and then carefully cultivated. People are using web based social networks more than recent past, but they always want to protect their private data from unknown access; meanwhile also eager to know more people whom they are interested. Among all other system, trust based recommenders have been one of the most used and demanding system which takes the advantage of social trust to generate more accurate predictions. In this work we have proposed for Meven (An Enterprise trust-based profile recommendation with privacy), which uses Social Network Content (User Profiles and trends) with Trust and privacy control policy. The idea of system is to provide Social Networks with the ability to quickly find related information about the users having similar behaviors as the current user. The users will also be able to set the privacy metrics on their profiles so they will not get recommendation of those they feel less important and this is achieved by Privacy metrics. To generate accurate predictions, we defined trust between two users as a strong bond which is computed using different metrics based on user’s activities with respect to different content such as blogging, writing articles, commenting, and liking along with profile information such as organization, region, interests or skills. We have also introduced privacy metric in such a way so that users have full freedom to hide themselves from the recommendation system or they can also have the opportunity to customize their profiles to be visible to certain level of trustworthy users. We have exposed our application as a web service(api) so that any social network web portal can access the recommendations and publish them as a widget in social network.

  • 82.
    Agevik, Niklas
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Shared UMTS Networks - A Techno-Economic Study on Mobile Network Operators’ Possibilities to Deliver Unique Products and Services2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Historically, there has been a one-to-one mapping between a mobile network and the reseller of the network’s services. Recent developments challenge this model. Virtual operators have emerged in GSM networks and during the rollout of UMTS networks, many operators built shared UMTS networks. This study analyses the impact of shared networks on the mobile network operators’ abilities to deliver unique products and services to their customers. Four sharing models that are in use today are analysed and presented in detail. These are site sharing, geographical split networks, shared RAN and spectrum sharing.

    The research in this study has been done in two steps. In the first step, possible differentiation opportunities are identified through literature studies and interviews with key persons at network operators, equipment manufacturers, business analysts and the Swedish national post and telecom agency. In the second step, this study compares the implementation of these opportunities in the four forms of shared networks with their implementations in a wholly owned network. The opportunities are grouped in three categories: products, quality of service differentiation and multiaccess networks.

    By setting quality of service attributes on bearers, such as latency and the attention/retention policy, quality of service differentiation is a possibility in common shared networks and geographical split networks. Although unlicensed access technologies, such as WLAN standards, can provide coverage differentiation in one sense, this study shows that this is not economical compared to UMTS pico-cells.

    The study finds that implementing features in the underlying network requires extensive cooperation between operators in all sharing models except for site sharing. Certain services require quality of service parameters that are mutually exclusive without over-provisioning in terms of network resources. Such parameters include for example latency and capacity. Even though the 3GPP UMTS standard allow for a separation of the service creation layer and the underlying network, this study argues that many services will still be dependent upon network features, thus mitigating the advantage of developing services in the unshared domain.

  • 83.
    Aggerstam, Thomas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Gallium nitride templates and its related materials for electronic and photonic devices2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

     

  • 84.
    Aggerstam, Thomas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Andersson, T.G.
    Holmström, Petter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Jänes, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Liu, X. Y.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    GaN/AlN multiple quantum well structures grown by MBE on GaN templates for 1.55 mu m intersubband absorption2007In: Quantum Sensing and Nanophotonic Devices IV / [ed] Razeghi, M; Brown, GJ, 2007, Vol. 6479, p. 64791E-1-64791E-12Conference paper (Refereed)
    Abstract [en]

    We have used MBE to grow MQW structures on MOVPE GaN/sapphire templates. The MQW devices are intended for high speed intersubband electroabsorption modulator devices operating at 1.55-mu m. The GaN/AlN multiple quantum well material was systematically studied regarding the surface morphology, structural characterization and optical property by atomic force microscopy, X-ray diffraction and Fourier transform infrared spectroscopy, respectively. The intersubband resonance energy was also calculated considering many-body effects in n-type doped structures. The multiple quantum well structure showed superior performance in terms of linewidth when grown on GaN templates as compared on sapphire. GaN quantum well and AlN barriers with a thickness of 3.3 and 4.2 nm respectively resulted in FWHM of the intersubband absorption peak as low as 93 meV at an absorption energy of 700 meV. This is promising for intersubband modulator applications.

  • 85.
    Aggerstam, Thomas
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    Sjödin, Mikael
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    Lorenzini, P.
    CNRS-CHREA.
    Look, D.C.
    Semiconductor Research Center, Wright State University.
    Investigation of the interface properties of MOVPE grown AlGaN/GaN high electron mobility transistor (HEMT) structures on sapphire2006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 2, p. 705-707Article in journal (Refereed)
    Abstract [en]

    We have developed a virtual GaN substrate on sapphire based on a two-step growth method. By optimizing the growth scheme for the virtual substrate we have improved crystal quality and reduced interface roughness. Our Al0.22Ga0.78N/GaN HEMT structure grown on the optimized semi-insulating GaN virtual substrate, exhibits Hall mobilities as high as 1720 and 7350 cm(2)/Vs and sheet carrier concentrations of 8.4 x 1012 and 10.0 x 1012 cm(-2) at 300 K and 20 K, respectively The presence of good AlGaN/GaN interface quality and surface morphology is also substantiated by X-Ray reflectivity and Atomic Force Microscopy measurements. A simplified transport model is used to fit the experimental Hall mobility.

  • 86. Aggerstam, Thomas
    et al.
    Lovqvist, Anita
    Stevens, Renaud
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Jonsson, Stefan
    Marcks von Würtemberg, Richard
    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.
    Dubois, Mardjan
    Ghisoni, Marco
    Selectively oxidized vertical-cavity surface-emitting lasers for high-speed data communication2001In: Proc. SPIE 4286, SPIE's Optoelectronics 2001, Photonics West, San Jose, US, Bellingham, WA, ETATS-UNIS: Society of Photo-Optical Instrumentation Engineers , 2001, Vol. 4286, p. 96-Conference paper (Refereed)
    Abstract [en]

    MITEL Semiconductor is developing the next generation low cost, high performance transceivers for data communication. The increasing quantity of data being transferred over the Internet demands very high capacity interconnects. A low cost, high-performance alternative is the use of parallel fiber interconnects where the light is, for example, coupled into a 12-channel fiber-ribbon. Parallel interconnects require good uniformity in order to reduce escalating costs and complexity. In this paper we report on the static and the modulation properties of 850nm multimode oxide VCSELs for use in such Gb/s transceiver system. Static power-current-voltage characteristics with good uniformity were obtained for different structures, with threshold currents down to sub-mA. A maximum small signal 3-dB bandwidth of 10 GHz and a modulation current efficiency up to 8.4 GHz/&#8730;[mA] were measured. Single channel results are presented for VCSELs operated at data rates from 2.5-10Gb/s.

  • 87.
    Aggerstam, Thomas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Pinos, Andrea
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
    Linnarsson, Margareta
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Electron and hole capture cross-sections of Fe acceptors in GaN:Fe epitaxially grown on sapphire2007In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 36, no 12, p. 1621-1624Article in journal (Refereed)
    Abstract [en]

    Carrier trapping of Fe (3+)/Fe2+ deep acceptors in epitaxially grown GaN:Fe on sapphire was studied by time-resolved photoluminescence. For the investigated Fe doping levels on the order of 10(18) cm(-3), the luminescence decay times are strongly dependent on the Fe concentration, indicating that Fe centers act as predominant nonradiative recombination channels. Linear dependence of the decay time on the iron concentration allows estimation of the electron capture cross-section for the Fe3+ ions, which is equal to 1.9 x 10(-15) cm(2). The upper bound for the cross-section of the hole capture of Fe2+ was evaluated as 10 x 10(-15) cm

  • 88.
    Aggerstam, Thomas
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    Sjödin, Mikael
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Centres, Electrum Laboratory, ELAB.
    AlGaN/GaN high-electron-mobility transistors on sapphire with Fe-doped GaN buffer layer by MOVPE2006In: Physica Status Solidi C - Current Topics in Solid State Physics: Vol 3, No 6 / [ed] Hildebrandt S; Stutzmann M, 2006, Vol. 3, p. 2373-2376Conference paper (Refereed)
    Abstract [en]

    A simple AlGaN/GaN HEMT structure without any interlayer on Fe-doped GaN (GaN:Fe) grown by LP-MOVPE in one single run on sapphire is demonstrated. The surface segregation of Fe in GaN occurring during growth is identified. Hall measurements yield 2DEG (two dimensional electron gas) mobilities of 1700 and 10700 cm2/Vs and sheet carrier concentrations of 5.1×10 12 and 5.7×1012 cm-2 at 300 K and 20 K, respectively. Good pinch-off current-voltage (ID-VD) characteristics is observed from AlGaN/GaN HEMTs. A maximum drain current density of 0.6 A/mm and a peak extrinsic transconductance of 200 mS/mm have been observed. The HEMT structure yields very good device isolation as indicated by an isolation current of ≀1 nA at 20 V.

  • 89.
    Agnarsson, Björn
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Surface studies on α–sapphire for potential use in GaN epitaxial growth2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This Licentiate thesis summarizes the work carried out by the author the years 2004 to 2008 at the University of Iceland and the Royal Institute of Technology (KTH) in Sweden. The aim of the project was to investigate the structure of sapphire (alpha-Al2O3) surfaces, both for pure scientific reasons and also for potential use as substrate for GaN-growth by molecular beam epitaxy.

    More generally the thesis describes some surface science methods used for investigating the substrates; the general physical back ground, the experi- mental implementation and what information they can give. The described techniques are used for surface analysis on sapphire substrates which have been treated variously in order to optimize them for use as templates for epi- taxial growth of GaN or related III-V compounds.

    The thesis is based on three published papers.

    The first paper focuses on the formation a thin AlN layer on sapphire, which may act as a buffer layer for potential epitaxial growth of GaN or any related III-V materials. Two types of sapphire substrates (reconstructed and non- reconstructed) were exposed to ammonia resulting in the formation of AlN on the surface. The efficiency of the AlN formation (nitridation efficiency) for the two surfaces was then compared as a function of substrate temperature through photoelectron spectroscopy and low electron energy diffraction. The reconstructed surface showed a much higher nitridation efficiency than the non-reconstructed surface.

    In the second paper, the affect of different annealing processes on the sapphire morphology, and thus its capability to act as a template for GaN growth, was studied. Atomic force microscopy, X-ray diffraction analysis together with ellipsometry measurements showed that annealing in H2 ambient and subse- quent annealing at 1300 °C in O2 for 11 hours resulted in high quality and atomically flat sapphire surface suitable for III-V epitaxial growth.

    The third paper describes the effect of argon sputtering on cleaning GaN surfaces and the possibility of using indium as surfactant for establishing a clean and stoichiometric GaN surface, after such sputtering. Soft sputtering, followed by deposition of 2 ML of indium and subsequent annealing at around 500 °C resulted in a well ordered and clean GaN surface while hard sputtering introduced defects and incorporated both metallic gallium and indium in the surface.

  • 90.
    Agnarsson, Björn
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Olafsson, S.
    Gislason, H. P.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Influence of initial surface reconstruction on nitridation of Al2O3 (0001) using low pressure ammonia2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 1, p. 013519-Article in journal (Refereed)
    Abstract [en]

    The purpose of this study is to investigate the effect of initial surface reconstruction on the nitridation process of Al2O3 (0001). This was done by exposing differently reconstructed sapphire substrates at different temperatures to low pressure ammonia (NH3). Structural and chemical analysis were carried out using low-electron energy diffraction and x-ray photoelectron spectroscopy. The experiments revealed that using low pressure ammonia (P-NH3 < 1 X 10(-5) Torr), no nitridation takes place on (1x1) unreconstructed surfaces. However, when the unreconstructed surface starts to change to a (root 31 x root 31) R +/- 9 degrees reconstructed surface, with increasing substrate temperature, the nitridation becomes successful. When using the initially reconstructed surface, the nitridation is successful even from the lowest temperature used. These results suggest that the initial surface reconstruction has a major effect on the nitridation process. This kinetic behavior has not been reported before, with most nitridation studies mainly focusing on the effect of surface temperature on the resulting surface morphology, rather than the actual kinetics of the process itself.

  • 91.
    Agnarsson, Björn
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Qi, B.
    Götelid, Mats
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Olafsson, S.
    Gislason, H. P.
    The effect of hard nitridation on Al(2)O(3) using a radio frequency operated plasma cell2011In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 22, p. 7796-7802Article in journal (Refereed)
    Abstract [en]

    We report on an atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) investigation of hard nitridation of sapphire (alpha.-Al(2)O(3)) substrate, using an Epi UNI-Bulb RF plasma cell at substrate temperatures ranging from 250 to 600 degrees C. Our results show that an AlN(1-x)O(x) layer forms on sapphire after extended nitridation at all temperatures, following a Stranski-Krastanov growth mode, with less islands forming at higher temperatures. We also observe a layer-dependent charging shift in XPS, separating smooth AlN(1-x)O(x) layers from rough AlN(1-x)O(x) islands due to their different electronic coupling to the substrate. Although the island growth is suppressed at higher temperatures, the surface roughness increases at higher temperatures as seen by AFM. We also observe sputtering effects with protrusions and pits.

  • 92.
    Agnarsson, Björn
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Qi, B.
    Szamota-Leandersson, Karolina
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Olafsson, S.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Investigation on the role of indium in the removal of metallic gallium from soft and hard sputtered GaN (0001) surfaces2009In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 517, no 21, p. 6023-6026Article in journal (Refereed)
    Abstract [en]

    Cleaning of GaN by argon sputtering and subsequent annealing introduces metallic gallium on the GaN surface. Once formed, this metallic gallium can be difficult to remove. it has a strong influence on the Fermi level position in the band gap and poses a problem for subsequent epitaxial growth on the surface. We present a method of removing metallic gallium from moderately damaged GaN surfaces by deposition of indium, and formation of an In-Ga alloy that can be desorbed by annealing at similar to 550 degrees C. After the In-Ga alloy has desorbed, photoemission spectra show that the Ga3d bulk component becomes narrower indicating a smoother and more homogeneous surface. This is also reflected in a sharper low energy electron diffraction pattern. On heavily damaged GaN surfaces, caused by hard sputtering, larger amount of metallic gallium forms after annealing at 600 degrees C. This gallium readily alloys with deposited indium, but the alloy does not desorb until a temperature of 840 degrees C is reached and even then, traces of both indium and metallic gallium could be found on the surface.

  • 93.
    Agnihotri, Mohit
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Chirikov, R.
    Militano, F.
    Cavdar, C.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Topology Formation in mesh networks considering Role Suitability2016In: 2016 IEEE Wireless Communications and Networking Conference Workshops, WCNCW 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 421-427Conference paper (Refereed)
    Abstract [en]

    The paper studies various mesh topology formation techniques that can be used to aid the development of large-scale capillary networks. The work focuses on how mesh networks can be established using Bluetooth Low Energy exploiting the heterogeneous characteristics of the devices in the network. A novel algorithm called Topology Formation considering Role Suitability (TFRS) is proposed aiming to maximize the network lifetime. The algorithm employs a newly introduced metric called role suitability metric (RSM) to assign the best role among master, relay and slave to a participating device. The RSM metric is computed from device characteristics including, but not limited to, energy, mobility and computational capability. We use system-level simulation to evaluate the performance of the proposed algorithm against a reference under a homogeneous deployment scenario consisting of heterogeneous devices. Results show that the network lifetime can be improved significantly when the topology is formed considering the device characteristics for both master role selection and relay selection. TFRS can achieve 20% to 40% higher network lifetime depending on the deployment characteristics over the reference algorithm.

  • 94.
    Agnihotri, Mohit
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Chirikov, R.
    Militano, F.
    Cavdar, Cicek
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Topology formation in mesh networks considering role suitability2016In: IEEE Wireless Communications and Networking Conference, WCNC, IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    The paper studies various mesh topology formation techniques that can be used to aid the development of large-scale capillary networks. The work focuses on how mesh networks can be established using Bluetooth Low Energy exploiting the heterogeneous characteristics of the devices in the network. A novel algorithm called Topology Formation considering Role Suitability (TFRS) is proposed aiming to maximize the network lifetime. The algorithm employs a newly introduced metric called role suitability metric (RSM) to assign the best role among master, relay and slave to a participating device. The RSM metric is computed from device characteristics including, but not limited to, energy, mobility and computational capability. We use systemlevel simulation to evaluate the performance of the proposed algorithm against a reference under a homogeneous deployment scenario consisting of heterogeneous devices. Results show that the network lifetime can be improved significantly when the topology is formed considering the device characteristics for both master role selection and relay selection. TFRS can achieve 20% to 40% higher network lifetime depending on the deployment characteristics over the reference algorithm.

  • 95.
    Agnihotri, Mohit Kumar
    KTH, School of Information and Communication Technology (ICT).
    Energy efficient topology formation for Bluetooth mesh networks using heterogeneous devices2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Internet of things (IoT) is the latest trend in our living spaces allowing machine to machine (M2M) communications at the extensive scale. To enable massive M2M communication and portable devices to run on limited power supplies for the extended duration of time, low-cost energy efficient wireless technologies are needed. Among the many competing technologies including Wi-Fi, Bluetooth has shown the potential to be one of the strong candidates to act as the connectivity solution for the IoT especially after the introduction of Bluetooth Low Energy (BLE). Nowadays BLE is one of the biggest players in the market of short-range wireless technologies. By 2020, nearly 30 billion BLE devices in the form of mobile phones, tablets, sports utilities, sensors, security systems and health monitors are expected to be shipped. This proliferation of low-cost devices may for the first time actualize the vision of IoT.

    This thesis studies various mesh topology formation techniques that can be used to aid the development of large-scale networks in capillary networks focusing on BLE. In particular, the thesis focuses on how mesh networks can be established over BLE communications especially exploiting the heterogeneous characteristics of the devices. A novel algorithm is proposed called Topology Formation considering Role Suitability (TFRS) to maximize the network lifetime. The algorithm uses a newly introduced metric called role suitability metric (RSM) to assign the best role among master, relay and slave to a device. The RSM metric bases its decision on various device characteristics including, but not limited to, energy, mobility, and computational capability. We use the system-level simulation to evaluate the performance of the proposed algorithm against a reference under homogeneous deployment scenario consisting of heterogeneous devices.

    Results show that the network lifetime can be improved significantly when the topology is formed considering the device characteristics for both master role selection and relay selection. TFRS can achieve moderate improvements ranging from 20% to 40% varying on the deployment characteristics over the reference case.

  • 96.
    Aguilar, Antonio
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    A Patient Identification System using RFID and IEEE 802.11b Wireless Networks2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The recent increased focus on patient safety in hospitals has yielded a flood of new technologies and tools seeking to improve the quality of patient care at the point of care. Hospitals are complex institutions by nature, and are constantly challenged to improve the quality of healthcare delivered to patients while trying to reduce the rate of medical errors and improve patient safety. Here a simple mistake such as patient misidentification, specimen misidentification, wrong medication, or wrong blood transfusion can cause the loss of a patient’s life. Misidentification of patients is a common problem that many hospitals face on the daily basis. Patient misidentification is one of the leading causes of medical errors and medical malpractice in hospitals and it has been recognised as a serious risk to patient safety.

    Recent studies have shown that an increasing number of medical errors are primarily caused by adverse drug events which are caused directly or indirectly by incorrect patient identification. In recognition of the increasing threat to patient safety, it is important for hospitals to prevent these medical errors from happening by adopting a suitable patient identification system that can improve upon current safety procedures.

    The focus of this master’s thesis is the design, implementation, and evaluation of a handheld-based patient identification system that uses radio frequency identification (RFID) and IEEE 802.11b wireless local area networks to identify patients. In this solution, each patient is given a RFID wristband which contains demographic information (patient ID number, ward number, hospital code, etc.) of the patient. A handheld device equipped with IEEE 802.11b wireless local area network connectivity and a RFID reader is then used by the medical staff to read the patient’s wristband, identify the patient, and access the relevant records of this patient.

    This work was carried out at the Department of Medical Physics and Bioengineering at the University College Hospital Galway (UCHG), Ireland and the National University of Ireland, Galway.

  • 97.
    Aguilar, Antonio
    et al.
    Digital Enterprise Research Institute, National University of Ireland, Galway, Ireland.
    van der Putten, Wil
    Department of Medical Physics, University College Hospital Galway, Galway, Ireland .
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Positive Patient Identification using RFID and Wireless  Networks2006In: Proceedings of the HISI 11th Annual Conference and Scientific Symposium, Dublin, Ireland, Dublin, Ireland, 2006Conference paper (Refereed)
    Abstract [en]

    The increased focus on patient safety in hospitals has yielded a flood of new technologies and tools seeking to improve the quality of patient care at the point-of-care. Hospitals are complex institutions by nature, and are constantly challenged to improve the quality of healthcare delivered to patients while trying to reduce the rate of medical errors and improve patient safety. Here a simple mistake such as patient misidentification, specimen misidentification, wrong medication, or wrong blood transfusion can cause the loss of a patient's life. The focus of this paper is the implementation and evaluation of a handheld-based patient identification system that uses radio frequency identification (RFID) and 802.11b wireless networks to identify patients. In this approach, each patient is given a RFID wristband which contains demographic information (patient ID number, patient summary, hospital code) of the patient. A handheld device equipped with 802.11b wireless connectivity and a RFID reader is then used by the medical staff to read the patient's wristband and identify the patient. This work was carried out at the Department of Medical Physics and Bioengineering at the University College Hospital Galway, Ireland and in co-operation with the National University of Ireland, Galway.

  • 98.
    Aguirre Quiroz, Gerardo Daniel
    KTH, School of Information and Communication Technology (ICT).
    Evaluation of the potential benefits of using Licensed Shared Access in the Americas2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Internet has become an ubiquitous service and human need. Mobile networks have been struggling with the "Mobile Data Tsunami", an increase in mobile broadband consumption due to faster networks, powerful devices and more traffic-demandingapplications, as well as a higher penetration volume. According to Cisco mobile data traffic is expected to grow to 15.9 exabytes per month by 2018, that is almost eleven times the mobile data traffic of 2013.

    Spectrum is a key factor for network deployments, since it determines the capacity of the network. Nonetheless, spectrum is a limited natural resource, i.e. a finite, non-exhaustible common resource. In order to fulfill the high performance targets of future mobile broadband (MBB) systems, a more efficient use and more effective management of spectrum resources have to be developed.

    Licensed Shared Access is a new complementary spectrum access scheme that allows for the sharing of partially used licensed spectrum from an incumbent (e.g. a government organization), by a limited number of “LSA licensees” (e.g. Mobile Network Operators). The LSA agreement follows pre-defined dynamic or static sharing conditions, that determine where, when and how to use the incumbent’s spectrum.

    The implementation of Licensed Shared Access needs the support of a very good regulatory framework and follow the harmonized spectrum pathway. Spectral harmonization, or the uniform allocation of frequency bands across entire region lowers the technology costs, making it easier for any country to consider its implementation. Once adpoted throughout the regions, economies of scale are achieved.

    Some first steps towards a new framework based on LSA have been given in Europe and North America, however to consider LSA as a real option, a complete analysis considering more markets is needed. It is crucial to consider how other regions around the world can be affected by this new approach in order to see if LSA is a viable option or not.

    The approach taken in this research covers the interrelations between technical, market and regulatory conditions in the Americas in order to present the possible value of LSA. The first part of the study deals with the analysis of the technical aspects of LSA. The following parts deal with under what conditions the evaluation is made. First, the study deals with the market conditions found in the Americas as a whole, to then deal with a more specific study of the market and regulatory conditions of selected countries in the region.

    The research showed how there are several ways LSA can bring positive value to established and emerging actors in the Americas, specially in high traffic areas, and/or indoor environments. However, and despite the advantages of LSA, the timing is not there yet. The region still has plenty of spectrum to be allocated as exclusive spectrum, which is preferred by operators. The low mobile broadband penetration in most of the region is also a factor for the low value of LSA in the time of this study.

  • 99.
    Agüero, Ramón
    et al.
    University of Cantabria, Spain.
    Berg, Miguel
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Choque, Johnny
    University of Cantabria, Spain.
    Hultell, Johan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Jennen, Ralf
    RWTH Aachen University, Germany.
    Markendahl, Jan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Muñoz, Luis
    University of Cantabria, Spain.
    Prytz, Mikael
    Ericsson Research.
    Strandberg, Ove
    Nokia, Finland.
    RRM Challenges for Non-Conventional and Low-Cost Networks in Ambient Networks2005Conference paper (Refereed)
    Abstract [en]

    This paper presents an overview of the Radio Resource Management (RRM) functionalities needed for Non-Conventional and Low-Cost Networks. These types of networks are characterized by increased cooperation between different types of networks and providers and they are believed to play a fundamental role for future wireless network networking. The paper describes three specific concepts, which latter is used to identify new RRM challenges. In addition, it identifies the relation between the RRM challenges and the Ambient Networks architecture and functionalities, in particular the multiradio resource management functionality.

  • 100.
    Ahlberg, Jesper
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Andrén, Andreas
    KTH, School of Information and Communication Technology (ICT).
    Usability Optimization and Testing Of Social Music Service2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Music playback in venues is very often controlled by the small group of people administrating the business or locale, and not by the audience of listeners themselves. The people listening rarely have any ability to affect the choice of music within the public place or business they are currently situated in.

    This master thesis is built around a developed social music service, that lets the listeners control the playback of music together. The project is called: Blicko, and it enables its users to collaboratively build up a playlist of music, and then vote on the order of the upcoming tracks to be played. It can be thought of as a tool which has similar functions to a jukebox. The service enables the visitors or attendees at any type of public place or venue (i.e. cafes, bars, lobby, restaurants etc.) to be a part of deciding and controlling which music is being played. The thesis is dedicated to examine the best way of refining the service, in terms of optimizing the User Experience (UX), by application of different practices and methods within the field of Human-Computer Interaction (HCI). This also involves managing the complications that rises when developing a multi-platform service for a wide range of devices.

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