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  • 301. Ambat, Sooraj K.
    et al.
    Chatterjee, Saikat
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Hari, K. V. S.
    Fusion of Algorithms for Compressed Sensing2013In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 61, no 14, p. 3699-3704Article in journal (Refereed)
    Abstract [en]

    For compressed sensing (CS), we develop a new scheme inspired by data fusion principles. In the proposed fusion based scheme, several CS reconstruction algorithms participate and they are executed in parallel, independently. The final estimate of the underlying sparse signal is derived by fusing the estimates obtained from the participating algorithms. We theoretically analyze this fusion based scheme and derive sufficient conditions for achieving a better reconstruction performance than any participating algorithm. Through simulations, we show that the proposed scheme has two specific advantages: 1) it provides good performance in a low dimensional measurement regime, and 2) it can deal with different statistical natures of the underlying sparse signals. The experimental results on real ECG signals shows that the proposed scheme demands fewer CS measurements for an approximate sparse signal reconstruction.

  • 302. Ambat, Sooraj K.
    et al.
    Chatterjee, Saikat
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Hari, K. V. S.
    Progressive fusion of reconstruction algorithms for low latency applications in compressed sensing2014In: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 97, p. 146-151Article in journal (Refereed)
    Abstract [en]

    Recently, it has been shown that fusion of the estimates of a set of sparse recovery algorithms result in an estimate better than the best estimate in the set, especially when the number of measurements is very limited. Though these schemes provide better sparse signal recovery performance, the higher computational requirement makes it less attractive for low latency applications. To alleviate this drawback, in this paper, we develop a progressive fusion based scheme for low latency applications in compressed sensing. In progressive fusion, the estimates of the participating algorithms are fused progressively according to the availability of estimates. The availability of estimates depends on computational complexity of the participating algorithms, in turn on their latency requirement. Unlike the other fusion algorithms, the proposed progressive fusion algorithm provides quick interim results and successive refinements during the fusion process, which is highly desirable in low latency applications. We analyse the developed scheme by providing sufficient conditions for improvement of CS reconstruction quality and show the practical efficacy by numerical experiments using synthetic and real-world data.

  • 303.
    Ambat, Sooraj K.
    et al.
    IISc - Indian Institute of Science.
    Chatterjee, Saikat
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hari, K.V.S.
    IISc - Indian Institute of Science.
    Fusion of greedy pursuits for compressed sensing signal reconstruction2012In: 2012 Proceedings Of The 20th European Signal Processing Conference (EUSIPCO), IEEE Computer Society, 2012, p. 1434-1438Conference paper (Refereed)
    Abstract [en]

    Greedy Pursuits are very popular in Compressed Sensing for sparse signal recovery. Though many of the Greedy Pursuits possess elegant theoretical guarantees for performance, it is well known that their performance depends on the statistical distribution of the non-zero elements in the sparse signal. Inpractice, the distribution of the sparse signal may not be knowna priori. It is also observed that performance of Greedy Pursuits degrades as the number of available measurements decreases from a threshold value which is method dependent. To improve the performance in these situations, we introduce a novel fusion framework for Greedy Pursuits and also propose two algorithms for sparse recovery. Through Monte Carlo simulations we show that the proposed schemes improve sparse signal recovery in clean as well as noisy measurement cases.

  • 304.
    Amelin, Kirill
    KTH, School of Electrical Engineering (EES).
    Analysis of ICRH of H and He-3 minorities in D and D-T plasmas in JET2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nuclear fusion is potentially a source of practically endless energy. It is one of the candidates to replace fossil fuels in the future. Fusion is also a source of clean energy, which should make a positive environmental impact. It can decrease the CO2 emission without creating any long-lived radioactive waste. The most promising fusion reaction is between deuterium and tritium that produces a helium atom and a highly energetic neutron. However, tritium is complicated to manufacture and handle, so its supply on Earth is currently limited. For this reason, only a small number of deuterium-tritium plasma experiments have been performed. Therefore, it is important to study the physics of the deuterium-tritium plasma to be able to make predictions for the future experiments. The topic addressed in this project is radio frequency heating, which is one of the main plasma heating methods. This method will also be applied in the future ITER experiment. The goal is to study how ion cyclotron resonance heating of hydrogen and helium-3 minorities performs in deuterium-tritium plasma. An analytical model based on previous research is presented in the report. The results from this analytical model are compared with the results from the numerical simulations performed using SELFO code to evaluate the validity of the analytical model. It is shown that the approximate analytical model provides viable estimations for power partition, fast ion population and their energy content. Collisional power transfer from minority to bulk plasma ions and electrons can be estimated to a certain extent, although a deviation from the numerical simulations are found when heating the helium-3 minority. Nevertheless, helium-3 minority fundamental resonance heating is shown to result in the strongest bulk plasma heating. The conclusion is that the analytical model can be used to recreate several important results of the simulations.

  • 305.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    An Evaluation of Intraday Trading and Demand Response for a Predominantly Hydro-Wind System Under Nordic Market Rules2015In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 30, no 1, p. 3-12Article in journal (Refereed)
    Abstract [en]

    Many countries are planning for a large-scale expansion of wind power. This development will have a significant impact on power system operation and economics. One of the challenges is that the difficulty to forecast wind power generation will increase the need for real-time balancing. This paper presents a study of how the impact of wind power forecast errors can be reduced by changes in the market design. The study is based on the conditions in the Nordic electricity market. A characteristic of this market is that there is a large share of flexible hydro generation; hence, ramp and unit commitment constraints rarely constrain dispatch. The need for regulation during real-time is provided in a voluntary real-time balancing market, where players can be compensated for their redispatch costs. Case studies are presented which show that a shift from day-ahead to intraday trading and increased demand response can improve the performance when the share of wind power is increasing.

  • 306.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Comparison of Capacity Credit Calculation Methods for Conventional Power Plants and Wind Power2009In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 24, no 2, p. 685-691Article in journal (Refereed)
    Abstract [en]

    Several methods for computing capacity credit values of power plants have been presented over the years. This paper uses an empirical approach to investigate and compare different properties of four typical capacity credit definitions. It is shown that the choice of definition indeed can have a significant impact on the results. Concerning three of the analyzed methods, it is found that important factors that influence the capacity credit are the overall generation adequacy and the penetration factor of the power plant; this means that the same generating unit will generally have a higher capacity credit if added to a system with high loss of load probability, and the unit will have a higher capacity credit if its installed capacity is small compared to the total installed capacity of the system. The results of the fourth method only depend on the size and availability of the generating units.

  • 307.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Impact of Trading Arrangements on Imbalance Costs2009Report (Other academic)
    Abstract [en]

    Today there are plans for large wind power investments in Sweden as well asin the neighbouring countries. At the same time, there is a developmenttowards increased price sensitivity of the consumers. These two changes arepartially connected to each other, because larger volumes wind power willresult in increased price variations in the spot market as well as the real-timebalancing market, which makes it desirable with consumers who are moreactive in the electricity market.This report studies different factors of the electricity trading arrangements,which are of importance to the efficiency of an electricity market with largevolumes of wind power and increased consumption flexibility. The study isbased on a new simulation model, which calculates the price for the differentphases of the electricity trading using supply and demand curves based onthe forecasts that are available in each phase. This model has then beenapplied to a number of test systems, which although fictitious, have the samebasic characteristics as the conditions found in the Nordic electricity market.The following factors of the design of the electricity market have beenstudied:• Planning horizon. The planning horizon refers to the delay time fromwhen the players have to submit bids to the spot market until the actualdelivery hour. The consequence of shortening the planning horizon is that theforecast errors will be smaller, especially for wind power forecasts. The resultsfrom the case study show that a shorter planning horizon is beneficial toalmost all players in the electricity market. If such a change of the electricitymarket is profitable does however depend on whether the value of theimproved forecasts is larger than the administrative costs.• Pricing of wind power imbalances. In the present Nordic electricitymarket, a two-price system is used for generation and a one-price system isused for consumption. An alternative would be to consider wind power asnegative load and include wind power imbalances in the consumptionimbalance of the balance responsible players. This would result in decreasedimbalance costs for wind power producers, but the results from the case studyshow that the differences are small compared to treating wind power as othergeneration. The explanation to this is that the imbalance costs in spite of allare only a few per cent of the wind power producer’ income of sellingelectricity.• Increased consumption flexibility. This reports considers theconsequences of introducing a new form contracts, which allows the retailersto initiate load reductions for certain consumers during a limited number ofhours per year. In the case study, this kind of contracts turned out to bebeneficial to all players (including those who were not themselves balanceresponsible for any consumption). The increased consumption flexibility alsoresulted in improved reliability of supply. These advantages must of course becompared to the costs of introducing such contracts and the necessaryinfrastructure

  • 308.
    Amelin, Mikael
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Simulation of Trading Arrangements Impact on Wind Power Imbalance Costs2008In: 2008 10TH INTERNATIONAL CONFERENCE ON PROBABILISTIC METHODS APPLIED TO POWER SYSTEMS, NEW YORK: IEEE , 2008, p. 25-31Conference paper (Refereed)
    Abstract [en]

    Uncertain wind power forecasts is a disadvantage in an electricity market where the majority of the trading is performed several hours before the actual delivery. This paper presents a model which can be used to study how changes in the trading arrangement-in particular changing the delay time between closure of the spot market and the delivery period or changing the imbalance pricing system-would affect different players in the electricity market. The model can be used in Monte Carlo simulation, which is demonstrated for an example system.

  • 309.
    Amelin, Mikael
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Englund, Calle
    Fagerberg, Andreas
    Balansering av vindkraft och vattenkraft i norra Sverige2009Report (Other academic)
  • 310.
    Amelin, Mikael
    et al.
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Hersoug, Ellef
    Options for Rural Electrification in Developing Countries. A Case Study in Kasulu, Tanzania.1997Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 311.
    Amelin, Mikael
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Knazkins, Valerijs
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Estimation of maximum power consumption in the grid area of Fortum, Stockholm2005Conference paper (Refereed)
  • 312.
    Amelin, Mikael
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Taking Credit: The Impact of Wind Power on Supply Adequacy-Experience from the Swedish Market2010In: IEEE POWER ENERGY MAG, ISSN 1540-7977, Vol. 8, no 5, p. 47-52Article in journal (Refereed)
    Abstract [en]

    This article presents some general concepts about capacity credit values, which are illustrated by theoretical examples as well as practical experience from the Swedish electricity market. The capacity credit of a wind generating unit (or a block of generating units) represents the contribution of the unit to the supply adequacy of the system. The capacity credit of a power plant is an abstract quantity based on probability calculations and requires knowledge of the probability distributions for available generation capacity and load. To secure the reliability of supply, the Swedish system operator was given the responsibility to purchase annual contracts for a "power reserve".

  • 313.
    Amin, Shoaib
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Characterization and Linearization of Multi-band Multi-channel RF Power Amplifiers2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The World today is deeply transformed by the advancement in wireless technology. The envision of a smart society where interactions between physical and virtual dimensions of life are intertwined and where human interaction is mediated by machines, e.g., smart phones, demands increasingly more data traffic. This continual increase in data traffic requires re-designing of the wireless technologies for increased system capacity and flexibility. In this thesis, aspects related to behavioral modeling, characterization, and linearization of multi-channel/band power amplifiers (PAs) are discussed.

    When building a model of any system, it is advantageous to take into account the knowledge of the physics of the system and include into the model. This approach could help to improve the model performance. In this context, three novel behavioral models and DPD schemes for nonlinear MIMO transmitters are proposed.

    To model and compensate distortions in GaN based RF PAs in presence of long-term memory effects, novel models for SISO and concurrent dual-band PAs are proposed. These models are based on a fixed pole expansion technique and have infinite impulse response. They show substantial performance improvement. A behavioral model based on the physical knowledge of the concurrent dual-band PA is derived, and its performance is investigated both for behavioral modeling and compensation of nonlinear distortions.

    Two-tone characterization is a fingerprint method for the characterization of memory effects in dynamic nonlinear systems. In this context, two novel techniques are proposed. The first technique is a dual two-tone characterization technique to characterize the memory effects of self- and cross-modulation products in concurrent dual-band transmitter. The second technique is for the characterization and analysis of self- and cross-Volterra kernels of nonlinear 3x3 MIMO systems using three-tone signals.

  • 314.
    Amin, Shoaib Amin
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden.
    Characterization and Linearization of Multi-channel RF Power Amplifiers2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The demands for high data rates and broadband wireless access require the development of wireless systems that can support wide and multi-band signals. To deploy these signals, new radio frequency (RF) front-ends are required which impose new challenges in terms of power consumption efficiency and sources of distortion e.g., nonlinearity. These challenges are more pronounced in power amplifiers (PAs) that degrade the overall performance of the RF transmitter. Since it is difficult to optimize the linearity and efficiency characteristics of a PA simultaneously, a trade-off is needed. At high input power, a PA exhibits high efficiency at the expense of linearity. On the other hand, at low input power, a PA is linear at the expense of the efficiency. To achieve linearity and efficiency at the same time, digital pre-distortion (DPD) is often used to compensate for the PA nonlinearity at high input power. In case of multi-channel PAs, input and output signals of different channels interact with each other due to cross-talk. Therefore, these PAs exhibit different nonlinear behavior than the single-input single-output (SISO) PAs. The DPD techniques developed for SISO PAs do not result in adequate performance when used for multi-channel PAs. Hence, an accurate behavioral modeling is essential for the development of DPD for multi-channel RF PAs. In this thesis, we propose three novel behavioral models and DPD schemes for nonlinear multiple-input multiple-output (MIMO) transmitters in presence of cross-talk. A study of the source of cross-talk in MIMO transmitters have been investigated to derive simple and powerful modeling schemes. These models are extensions of a SISO generalized memory polynomial model. A comparative study with a previously published MIMO model is also presented. The effect of coherent and partially non-coherent signal generationon DPD performance is also highlighted. It is shown experimentally that with partially non-coherent signal generation, the performance of the DPD degrades compared to coherent signal generation. In context of multi-channel RF transmitters, PA behavioral models and DPD schemes suffer from a large number of model parameters with the increase in nonlinear order and memory depth. This growth leads to high complexity model identification and implementation. We have designed a DPD scheme for MIMO PAs using a sparse estimation technique for reducing model complexity. This technique also increases the numerical stability when linear least square estimation model identification is used. A method to characterize the memory effects in a nonlinear concurrent dual-band PAs is also presented. Compared to the SISO PAs, concurrent dual-band PAs are not only affected by intermodulation distortions but also by cross-modulation distortions. The characterization of memory effects inconcurrent dual-band transmitter is performed by injecting a two-tone test signal in each input channel of the transmitter. Asymmetric energy surfaces are introduced for the intermodulation and cross-modulation products, which can be used to identify the power and frequency regions where the memory effects are dominant.

  • 315.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Gävle, Sweden.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rönnow, Daniel
    ATM, University of Gävle.
    Digital Predistortion of Single and Concurrent Dual BandRadio Frequency GaN Amplifiers with Strong NonlinearMemory Effects2017In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 65, no 7, p. 2453-2464Article in journal (Refereed)
    Abstract [en]

    Electrical anomalies due to trapping effects in gallium nitride (GaN) power amplifiers (PAs) give rise to long-term or strong memory effects. We propose novel models based on infinite impulse response fixed pole expansion techniques for the behavioral modeling and digital predistortion of single-input single-output (SISO) and concurrent dual-band GaN PAs. Experimental results show that the proposed models outperform the corresponding finite impulse response (FIR) models by up to 17 dB for the same number of model parameters. For the linearization of a SISO GaN PA, the proposed models give adjacent channel power ratios (ACPRs) that are 7-17 dB lower than the FIR models. For the concurrent dual-band case, the proposed models give ACPRs that are 9-14 dB lower than the FIR models.

  • 316.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Khan, Zain Ahmed
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Isaksson, Magnus
    Högskolan i Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rönnow, Daniel
    Högskolan i Gävle.
    Concurrent Dual-band Power Amplifier Model Modification using Dual Two-Tone Test2016In: European Microwave Week 2016: "Microwaves Everywhere", EuMW 2016 - Conference Proceedings; 46th European Microwave Conference, EuMC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 186-189, article id 7824309Conference paper (Refereed)
    Abstract [en]

    A dual two-tone technique for the characterization of memory effects in concurrent dual-band transmitters is revisited to modify a 2D-DPD model for the linearization of concurrent dual-band transmitters. By taking into account the individual nonlinear memory effects of the self- and cross-kernels, a new2D modified digital pre-distortion (2D-MDPD) model is proposed,which not only supersedes the linearization performance but also reduces the computational complexity compared to the 2DDPDmodel in terms of a number of floating point operations(FLOPs). Experimental results show an improvement of 1.7 dBin normalized mean square error (NMSE) and a 58% reduction in the number of FLOPs.

  • 317.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Ladin, Per N.
    ATM, University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Rönnow, Daniel
    ATM, University of Gävle.
    2D Extended Envelope Memory Polynomial Model forConcurrent Dual-band RF Transmitters2016In: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787Article in journal (Refereed)
    Abstract [en]

    The paper presents a 2D extended envelope memory polynomial (2D-EEMP) model for concurrent dual-band radio frequency (RF) power amplifiers (PAs). The model is derived based on the physical knowledge of a dual-band RF PA. The derived model contains cross-modulation terms not included in previously published models; these terms are found to be of importance for both behavioral modeling and digital pre-distortion (DPD). The performance of the derived model is evaluated both as the behavioral model and DPD, and the performance is compared with state-of-the-art2D-DPD and dual-band generalized memory polynomial (DB-GMP) models. Experimental result shows that the proposed model resulted in normalized mean square error (NMSE) of -51.7/-51.6dB and adjacent channel error power ratio (ACEPR) of -63.1/-63.4 dB, for channel 1/2, whereas the 2D-DPD resulted in the largest model error and DB-GMP resulted in model parameters that are 3 times more than those resulted with the proposed model with the same performance. As pre-distorter, the proposed model resulted in adjacent channel power ratio (ACPR) of -55.8/ -54.6 dB for channel 1/2 and is 7-10 dB lower than those resulted with the 2D-DPD model and2-4 dB lower compared to the DB-GMP model.

  • 318.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Högskolan i Gävle.
    Landin, Per
    Chalmers University of Technology.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rönnow, Daniel
    Högskolan i Gävle.
    Behavioral modeling and linearization of crosstalk and memory effects in RF MIMO transmitters2014In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 62, no 4, p. 810-823Article in journal (Refereed)
    Abstract [en]

    This paper proposes three novel models for behavioral modeling and digital pre-distortion (DPD) of nonlinear 2 x 2 multiple-input multiple-output (MIMO) transmitters in the presence of crosstalk. The proposed models are extensions of the single-input single-output generalized memory polynomial model. Three types of crosstalk effects were studied and characterized as linear, nonlinear, and nonlinear & linear crosstalk. A comparative study was performed with previously published models for the linearization of crosstalk in a nonlinear 2 x 2 MIMO transmitter. The experiments indicate that, depending on the type of crosstalk, the selection of the correct model in the transmitter is necessary for behavioral modeling and sufficient DPD performance. The effects of coherent and partially noncoherent signal generation on the performance of DPD were also studied. For crosstalk levels of 30 dB, the difference in the normalized mean square error and adjacent channel power ratio was found to be 3-4 dB between coherent and partially noncoherent signal generation.

  • 319.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden.
    Landin, Per N.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Rönnow, Daniel
    2D Extended envelope memory polynomial model for concurrent dual-band RF transmitters2017In: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787, Vol. 9, no 8, p. 1619-1627Article in journal (Refereed)
    Abstract [en]

    The paper presents a two-dimensional (2D) extended envelope memory polynomial model for concurrent dual-band radio frequency (RF) power amplifiers (PAs). The model is derived based on the physical knowledge of a dual-band RF PA. The derived model contains cross-modulation terms not included in previously published models; these terms are found to be of importance for both behavioral modeling and digital predistortion (DPD). The performance of the derived model is evaluated both as the behavioral model and DPD, and the performance is compared with state-of-the-art 2D-DPD and dual-band generalized memory polynomial (DB-GMP) models. Experimental result shows that the proposed model resulted in normalized mean square error of -51.7/-51.6 dB and adjacent channel error power ratio of -63.1/-63.4 dB, for channel 1/2, whereas the 2D-DPD resulted in the largest model error and DB-GMP resulted in model parameters that are three times more than those resulted with the proposed model with the same performance. As pre-distorter, the proposed model resulted in adjacent channel power ratio of -55.8/-54.6 dB for channel 1/2 and is 7-10 dB lower than those resulted with the 2D-DPD model and 2-4 dB lower compared with the DB-GMP model.

  • 320. Amin, Shoaib
    et al.
    van Moer, Wendy
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Ronnow, Daniel
    Rebuttal to "On Dual-Band Amplifications Using Dual Two-Tones Clarifications and Discussions"2017In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 66, no 10, p. 2795-2797Article in journal (Refereed)
    Abstract [en]

    This rebuttal is to "On dual-band amplifications using dual two-tone: Clarifications and discussion." In the following, we provide our reply.

  • 321.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden.
    Van Moer, Wendy
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Rönnow, Daniel
    Characterization of a Concurrent dual-band Power Amplifier using a dual-tone excitation signals2014In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662Article in journal (Other academic)
  • 322.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Van Moer, Wendy
    University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Rönnow, Daniel
    University of Gävle.
    Characterization of concurrent dual-band Power Amplifiers using a dual two-tone excitation signal2015In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, no 99Article in journal (Refereed)
    Abstract [en]

    A method to characterize the memory effects in a nonlinear concurrent dual-band transmitter is presented. It is an extension of the conventional two tone test for power amplifiers to concurrent dual band transmitters. The output signal of a concurrent dual-band transmitter is affected not only by intermodulation products but also by cross-modulation products. In one frequency band, the transmitter is excited by a two tone signal which frequency separation is swept. In the second band the transmitter is concurrently excited by an other two tone signal with slightly wider frequency separation. The frequency difference of the two signals is fixed during the frequency sweep. The two tone test is made at different power levels. The upper and lower third-order inter- and cross-modulation products are measured. The asymmetry between the upper and lower third-order inter- and cross-modulation products are measures of the transmitter's memory effects. The measurement results show that the memory effects are more dominant in the third-order intermodulation products than in the cross modulation products. An error analysis and system calibration was performed and measurement results for two different devices are presented.

  • 323.
    Amin, Shoaib
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zenteno, Efrain
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Landin, Per
    Dept. Electronics, Mathematics and Natural Sciences, Faculty of Engineering and Sustainable Development,University of Gävle .
    Rönnow, Daniel
    Dept. Electronics, Mathematics and Natural Sciences, Faculty of Engineering and Sustainable Development,University of Gävle .
    Isaksson, Magnus
    Dept. Electronics, Mathematics and Natural Sciences, Faculty of Engineering and Sustainable Development,University of Gävle .
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Noise Impact on the Identification of DigitalPredistorter Parameters in the Indirect LearningArchitecture2012In: Swedish Communication Technologies Workshop (Swe-CTW), 2012, IEEE conference proceedings, 2012, p. 36-39Conference paper (Refereed)
    Abstract [en]

    The indirect learning architecture (ILA) is the mostused methodology for the identification of Digital Pre-distorter(DPD) functions for nonlinear systems, particularly for highpower amplifiers. The ILA principle works in black box modelingrelying on the inversion of input and output signals of thenonlinear system, such that the inverse is estimated. This paperpresents the impact of disturbances, such as noise in the DPDidentification. Experiments were performed with a state-of-artDoherty power amplifier intended for base station operationin current telecommunication wireless networks. As expected,a degradation in the performance of the DPD (measured innormalized mean square error (NMSE)) is found in our experiments.However, adjacent channel power ratio (ACPR) canbe a misleading figure of merit showing improvement in theperformance for wrongly estimated DPD functions.

  • 324.
    Aminian, Behdad
    KTH, School of Electrical Engineering (EES), Automatic Control.
    GISOO: A Virtual Testbed for Wireless Networked Control Systems2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Networked control over wireless sensor and actuator networks is of growing importance in cyber-physical systems as in industrial process control and building management systems. The correct design of wireless communication solutions and control algorithms is therefore a major requirement in such systems. Simulators and emulators of wireless networked control systems (WNCSs) are tools that help the system designer to develop, optimize and validate solutions prior to the deployment in a real system. Without such tools the development and validation of complex systems would be highly costly, both financially and timely.

    Considering the special characteristic of WNCSs, which is a complex combination of control systems and a wireless network, WNCSs’ simulators must be able to model and emulate/simulate both the control systems and wireless systems together.

    In this thesis project, GISOO, a new simulation platform for WNCSs has been created. GISOO stands for Graphical Integration of Simulink and Cooja and is a hybrid simulation environment which simulates both the physical system to be controlled and the wireless devices and their networking behavior. Simulink, developed by Mathworks, is a tool for modeling, simulation and analysis of dynamic systems and is widely used by the control engineers. The Cooja network simulator, is able to emulate the operation of a real wireless device and its networking behavior. In this way, developers can set up simulations both to debug the developed software and the behavior of the system before running it in the target hardware. This specification makes GISOO a powerful virtual testbed for developing and evaluating novel communication protocols, control techniques and their interactions in large scale complex systems. We validate the correct operation of GISOO in the closed-loop control of a double tank system.

  • 325.
    Aminian, Behdad
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Araújo, José
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    GISOO: A virtual testbed for wireless cyber-physical systems2013In: Industrial Electronics Society, IECON 2013 - 39th Annual Conference of the IEEE, IEEE , 2013, p. 5588-5593Conference paper (Refereed)
    Abstract [en]

    The increasing demand for wireless cyber-physical systems requires correct design, implementation and validation of computation, communication and control methods. Traditional simulation tools, which focus on either computation, communication or control, are insufficient when the three aspects interact. Efforts to extend the traditional tools to cover multiple domains, e.g., from simulating only control aspects to simulating both control and communication, often rely on simplistic models of a small subset of possible communication solutions. We introduce GISOO, a virtual testbed for simulation of wireless cyber-physical systems that integrates two state-of-the art simulators, Simulink and COOJA. GISOO enables users to evaluate actual embedded code for the wireless nodes in realistic cyber-physical experiments, observing the effects of both the control and communication components. In this way, a wide range of communication solutions can be evaluated without developing abstract models of their control-relevant aspects, and changes made to the networking code in simulations is guaranteed to be translated into production code without errors. A double-tank laboratory experimental setup controlled over a multi-hop relay wireless network is used to validate GISOO and demonstrate its features.

  • 326.
    Aminlashgari, Nina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. ABB, Sweden.
    Becerra, Marley
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. ABB, Sweden.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Characterization of degradation fragments released by arc-induced ablation of polymers in air2016In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 49, no 5, article id 055502Article in journal (Refereed)
    Abstract [en]

    Polymers exposed to high intensity arc plasmas release material in a process called arc-induced ablation. In order to investigate the degradation fragments released due to this process, two different polymeric materials, poly(oxymethylene) copolymer (POM-C) and poly(methyl methacrylate) (PMMA), were exposed to a transient, high-power arc plasma in air. A small fraction of the ablated material drifting away from the arcing volume was deposited on a fixed glass substrate during the total duration of a 2 kA ac current semicycle. In addition, another fraction of the released material was deposited on a second moving substrate to obtain a time-resolved streak 'image' of the arc-induced ablation process. For the first time, mass spectra of degradation fragments produced by arc-induced ablation were obtained from the material deposited on the substrates by using laser desorption ionization time-of-flight mass spectrometry (LDI-ToF-MS). It was found that oligomers with mean molecular weight ranging between 400 and 600 Da were released from the surface of the studied polymers. The obtained spectra suggest that the detected degradation fragments of POM could be released by random chain scission of the polymer backbone. In turn, random chain scission and splitting-off the side groups are suggested as the main chemical mechanism leading to the release of PMMA fragments under arc-induced ablation.

  • 327.
    Amoozadeh, Mani
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Certificate Revocation List Distribution in Vehicular Communication Systems2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Message exchange in VANETs should be secured. Researchers have designed many methods to meet this goal. One of the ways agreed upon by most researchers, is through the use of a public-key infrastructure (PKI). An important part of any PKI system is certificate revocation. The revocation is usually done by periodically issuing a Certificate Revocation List (CRL) by the Certification Authority (CA). After the creation of a CRL by CA, the CRL should be distributed in the VC system. The important question is how we can distribute the CRL efficiently and in a timely manner throughout the system in a way that all vehicles receive a genuine copy of it. A couple of researches considered CRL distribution in the past and proposed different methods like RSU-only [1], C2C Epidemic [2], and Most Pieces Broadcast (MPB) [3]. We implement the aforementioned CRL distribution methods and evaluate them using a common framework. With this approach, we can compare these methods accurately and point out the limitations of each. Due to the fact that C2C Epidemic did not provide any packet-level implementation, we propose an implementation for it. We also propose a new method for CRL distribution called ICE (Intelligent CRL Exchange). This method uses V2V and I2V communication to distribute the CRL pieces to vehicles. ICE is an enhanced version of the MPB method and it uses semi-incremental CRL exchange. With this approach, the number of duplicate received pieces decreases in comparison to the MPB method. Moreover, ICE uses a simple approach to decrease the number of unnecessary broadcasts by RSUs. The evaluation is done through simulations. OMNET++ [4] and the MiXiM framework are used for detailed packet-level simulation. The simulation is done for both small and large scale scenarios. For the large scale simulation, we use SUMO [5] to generate mobility traces of vehicle nodes. Different criteria are defined so that we can compare CRL distribution methods. According to the simulation results, vehicles in C2C Epidemic, MPB and ICE receive all the required CRL pieces in less time in comparison to RSU-only, because vehicles use both I2V and V2V communications. MPB shows a better performance than C2C Epidemic, but the number of duplicate received pieces increases substantially. ICE tries to alleviate this by incorporating semi-incremental CRL exchange. Furthermore, the number of broadcasts by RSUs in the ICE method shows reduction.

  • 328. Anatory, Justinian
    et al.
    Theethayi, Nelson
    Thottappillil, Rajeev
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Channel Characterization for Indoor Power-Line Networks2009In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, no 4, p. 1883-1888Article in journal (Refereed)
    Abstract [en]

    Power-line networks are promising mediums by which broadband services can be offered, such as Internet services, voice over Internet protocol, digital entertainment, etc. In this paper, an analysis of delay spread, coherence bandwidth, channel capacity, and averaged delay in the frequency bands up to 100 MHz for typical indoor power-line networks are studied. Earlier studies for indoor power-line networks considered frequencies up to 30 MHz only and earlier works have shown that at these frequency bands, the data rates are generally low and are inefficient for digital entertainment in comparison with wireless local-area networks standards, such as IEEE 802.11n. In this paper, it is shown that at 100 MHz, the average channel capacity for typical indoor power-line networks can be up to 2 Gb/s and it is found that by increasing the number of branches in the link between transmitting and receiving ends, the average channel capacity decreases from 2 Gb/s to 1 Gb/s (when the number of branches was increased by four times for a power spectral density of 60 dBm/Hz). At the same time, the coherence bandwidth decreased from 209.45 kHz to 137.41 kHz, which is much better than the coherence bandwidths corresponding to 30-MHz systems. It is therefore recommended to operate the indoor power-line networks at 100-MHz bandwidths for a wide variety of broadband services.

  • 329. Anatory, Justinian
    et al.
    Theethayi, Nelson
    Thottappillil, Rajeev
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Effects of Multipath on OFDM Systems for Indoor Broadband Power-Line Communication Networks2009In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, no 3, p. 1190-1197Article in journal (Refereed)
    Abstract [en]

    Power-line networks are an excellent infrastructure for broadband data transmission. However, various multipaths within a broadband power-line communication (BPLC) system exist due to stochastic changes in the network load impedances, branches, etc. This further affects network performance. This paper attempts to investigate the performance of indoor channels of a BPLC system that uses orthogonal frequency-division multiplexing (OFDM) techniques. It is observed that when a branch is added in the link between the sending and receiving end of an indoor channel, an average of 4-dB power loss is found. Additionally, when the terminal impedances of the branch change from the line characteristic impedance to impedance of lower values, the power loss (signal-to-noise ratio) is about 0.67 dB/Omega. On the contrary, for every increase in the terminal impedances by 100 Omega, above the line characteristic impedance, the power loss is 0.1. dB/Omega. When the line terminal impedances are close to short or open circuits, OFDM techniques show degraded performance. This situation is also observed when the number of branches increases. In this paper, it is shown that to overcome such performance degradation, the concatenated Reed-Solomon codes/interleaved Viterbi methods can be used. The observations presented in the paper could be useful for an efficient design of a BPLC system that uses OFDM techniques.

  • 330. Anatory, Justinian
    et al.
    Theethayi, Nelson
    Thottappillil, Rajeev
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Performance of Underground Cables That Use OFDM Systems for Broadband Power-Line Communications2009In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, no 4, p. 1889-1897Article in journal (Refereed)
    Abstract [en]

    Power-line networks are proposed for broadband data transmission. The presence of multipaths within the broadband power-line communication (BPLC) system, due to stochastic changes in the network load impedances, branches, etc. pose a real challenge as it affects network performance. This paper attempts to investigate the performance of an orthogonal frequency-division multiplexing (OFDM)-based BPLC system that uses underground cables. It is found that when a branch is added in the link between the sending and receiving end, there is an average of 4-dB power loss. In addition, when the terminal impedances of the branches that are connected to the link between the transmitting and receiving end vary from line characteristic impedance to low-impedance values, the power loss (signal-to-noise ratio) is about 0.35 dB/Omega. On the contrary, for an increase in the terminal impedances by 100 Omega above line characteristic impedance, the power loss is 0.23 dB/Omega. When the branch terminal impedances are close to short or open circuits, OFDM techniques show degraded performance. This situation is also observed when the number of branches increases. It is shown that to overcome degraded network performance, the concatenated Reed-Solomon codes/interleaved Viterbi methods can be used, which could be used for an efficient design of the BPLC system that uses OFDM techniques.

  • 331. Anatory, Justinian
    et al.
    Theethayi, Nelson
    Thottappillil, Rajeev
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Mvungi, Nerey H.
    A Broadband Power-Line Communication System Design Scheme for Typical Tanzanian Low-Voltage Network2009In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, no 3, p. 1218-1224Article in journal (Refereed)
    Abstract [en]

    Information and communications technologies (ICTs) are gaining importance in developing countries. Power-line network is a potential infrastructure for ICT services provision. Power-lines are highly interconnected network with stochastic variation in number of branches. Under such distributed network conditions the design of a broadband power-line communication (BPLC) system is a challenge. In this paper a case study of an actual power-line network, representative of a low-voltage BPLC channel in Dar es Salaam, Tanzania is considered. We shall investigate the performance of such a low-voltage channel that uses orthogonal frequency division multiplexing (OFDM) technique with binary phase shift keying (BPSK) modulation scheme for communication. For sensitivity analysis, three different transmitter locations were chosen and receiver points were varied to identify the possible degraded performance scenarios. Analysis show that in the frequency bands of 100 MHz, the channel delay spread for such networks is about 4 mu s, giving a maximum number of subchannels 4096 with 512 cyclic prefix. To improve the degraded performance scenarios, the concatenated Reed Solomon outer code with punctured convolution inner code was applied to the network. It was found that when the branches were terminated by its corresponding characteristic impedances the performance is improved by 1.0-20 dB compared to a corresponding uncoded system. On the contrary for a coded system when the branches were terminated either in low or higher impedances compared to branch characteristic impedances the improvement was greater than 2-15 dB. This study demonstrates that the specification proposed by IEEE-802.16 Broadband wireless access working groups can be used for performance improvement of distributed low-voltage systems.

  • 332. Andersen, O.
    et al.
    Wisell, David
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gävle, Sweden.
    Keskitalo, N.
    Stenvard, P.
    Cost effective high performance modular instrumentation, signal generation and signal analysis for future mobile communication systems2007In: 2007 IEEE Autotestcon, IEEE , 2007, p. 660-668Conference paper (Refereed)
    Abstract [en]

    A decrease in life cycle cost is a key issue for testing of mobile communication systems. The rapid development and edge technology requires high performance instruments and state of the art measurement technology. It is desired to use virtual/synthetic instruments and put the measurement technology in software independent of hardware, i.e. software driven measurements. Increased flexibility and modularization, both in hardware and software, are requirements to support the cost decrease. The hardware basis is signal generation and signal analysis. In this paper state of the art signal generation and signal analysis capabilities are demonstrated in a modular and flexible architecture. A direct IF synthesis is used to generate 1 WideBand Code-Division Multiple Access (WCDMA) carrier with more than 72 dB Adjacent Carrier Leakage Ratio (ACLR) 2 carrier with more than 68 dBc ACLR over a total bandwidth of 100 MHz. The signal analysis capabilities, ACLR performance, for a WCDMA carrier is better than -70 dBc and for a continuous wave better than -85 dBc over a bandwidth of 42.5 MHz. The critical down converter in the set up doesn't degrade the performance.

  • 333.
    Anderson, James
    et al.
    Oxford University.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Papachristodoulou, Antonis
    Oxford University.
    Dynamical System Decomposition Using Dissipation Inequalities2011In: Proceedings of the 50th IEEE Conference on Decision and Control and European Control Conference,  Orlando, Florida, 2011Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate stability and inter-action measures for interconnected systems that have beenproduced by decomposing a large-scale linear system into aset of lower order subsystems connected in feedback. We beginby analyzing the requirements for asymptotic stability throughgeneralized dissipation inequalities and storage functions. Usingthis insight we then describe various metrics based on a system’senergy dissipation to determine how strongly the subsystemsinteract with each other. From these metrics a decompositionalgorithm is described.

  • 334. Anderson, R. P.
    et al.
    Milutinovic, D.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Self-triggered stabilization of continuous stochastic state-feedback controlled systems2013In: 2013 European Control Conference, ECC 2013, 2013, p. 1151-1155Conference paper (Refereed)
    Abstract [en]

    Event-triggered and self-triggered control, in which the time of update to the controls is based on either current or outdated sampled data, have recently been employed to reduce the computational load or resource consumption for distributed real-time control systems. In this work, we propose a self-triggered scheme for nonlinear controlled stochastic differential equations with additive noise terms. A self-triggering update condition is derived that guarantees stability in the p-th moment of the state distribution. We show that the length of the times between controller updates as computed from the proposed scheme is strictly positive and provide examples.

  • 335. Anderson, R. P.
    et al.
    Milutinović, D.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Self-triggered sampling for second-moment stability of state-feedback controlled SDE systems2015In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 54, p. 8-15Article in journal (Refereed)
    Abstract [en]

    Event-triggered and self-triggered control, whereby the times for controller updates are computed from sampled data, have recently been shown to reduce the computational load or increase task periods for real-time embedded control systems. In this work, we propose a self-triggered scheme for nonlinear controlled stochastic differential equations with additive noise terms. We find that the family of trajectories generated by these processes demands a departure from the standard deterministic approach to event- and self-triggering, and, for that reason, we use the statistics of the sampled-data system to derive a self-triggering update condition that guarantees second-moment stability. We show that the length of the times between controller updates as computed from the proposed scheme is strictly positive and provide related examples.

  • 336.
    Anderson, Taurug
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Iterative Learning Control model for a Resistive Wall Mode Active Controller2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The EXTRAP T2R is a Reversed Field Pinch (RFP) device purposed to conduct magnetic confinement fusion research. Magnetic confinement works on the principle of isolating the hot plasma from the cool walls by locking in the plasma onto the magnetic field lines. Due to the generally unstable nature of plasma, the plasma column will shift off its centered position and encroach upon the cooling walls. To counteract this, a series of magnetic sensor coil are placed around the torus that serve as the input for another set of coils that will generate a magnetic field to force the plasma column back in place. This is a feedback mechanism that uses a Proportional-Integral-Derivative (PID) as the loop gain control mechanisms. While this was effective in stabilizing the system it was discovered that during the start up phase of the experiment there was a repeatable pattern of disturbance. As such it offers the opportunity to make use of a feedforward Iterative Learning Control (ILC) that could provide a much more precise stabilization and occlude the possibility of saturating the feedback coils. In this thesis an ILC system will be built upon the existing PID system, it will be modeled in MATLAB and SIMULINK then run to simulate and gauge its performance.

  • 337.
    Andersson, Dennis
    et al.
    Swedish Defense Research Agency.
    Granåsen, Magdalena
    Swedish Defense Research Agency.
    Sundmark, Thomas
    Swedish Defense Research Agency.
    Holm, Hannes
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Hallberg, Jonas
    Swedish Defense Research Agency.
    Exploratory Sequential Data Analysis of a Cyber Defence Exercise2011In: Proceedings of the International Defense and Homeland Security Simulation Workshop (DHSS) 2011, Caltek s.r.l. , 2011, p. 27-32Conference paper (Refereed)
    Abstract [en]

    Baltic Cyber Shield 2010 (BCS), a multi-national civilmilitary cyber defence exercise (CDX), aimed to improve the capability of performing a CDX and investigate how IT attacks and defence of critical infrastructure can be studied. The exercise resulted in a massive dataset to be analyzed and many lessons learned in planning and executing a large-scale multinational CDX. A reconstruction & exploration (R&E) approach was used to capture incidents such as attacks and defensive counter-measures during the exercise. This paper introduces the usage of R&E combined with exploratory sequential data analysis (ESDA) and discusses benefits and limitations of using these methods for analyzing multi-national cyber defence exercises. Using ESDA we were able to generate statistical data on attacks from BCS, such as number of reported attacks by the attackers and the defenders on different type of services. Initial results from these explorations will be analyzed and discussed.

  • 338.
    Andersson, Dorothea
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Simulation of industrial control system field devices for cyber security2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Industrial Control Systems (ICS) are an integral part of modernsociety, not least when it comes to controlling and protecting criticalinfrastructure such as power grids and water supply. There is a need to testthese systems for vulnerabilities, but it is often difficult if not impossible to doso in operational real time systems since they have been shown to be sensitiveeven to disturbances caused by benign diagnostic tools. This thesis exploreshow ICS field devices can be simulated in order to fool potential antagonists,and how they can be used in virtualized ICS for cyber security research. 8different field devices were simulated using the honeypot daemon Honeyd,and a generally applicable simulation methodology was developed. It was alsoexplored how these simulations can be further developed in order to functionlike real field devices in virtualized environments.

  • 339.
    Andersson, Elin
    KTH, School of Electrical Engineering (EES).
    Multi-hop communication network2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 340.
    Andersson, Eva
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Development of a dynamic model for start-up optimization of coal-red power plants2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The expansion of renewable energies and the deregulations of the energy market are increasing the demand of regulating power. In absence of hydropower, thermal power is often used for this purpose instead. This thesis focuses on the Vattenfall owned power plant Jänschwalde located in Germany. The goal is to optimize the start-up procedure, so that the start-up time is reduced without causing too much thermal stress on the important thickwalled components in the boiler. By reducing the start-up time, the plant can become more protable,  exible and better suited to regulate the electricity market.

    A start-up model was built in Dymola and validated against measurement data and a simulation model of Jänschwalde, which is too complex to use for optimization purposes. The JModelica.org platform was used for the optimization part of the project. It was possible to nd optimal solutions for the start-up process of the Jänschwalde power plant, but the convergence of the optimization algorithm was very dependent on the optimization options used and the scaling of the plant model. Further work includes development of the components used in the start-up model, rening the discretization and scaling for the optimization problem.

  • 341.
    Andersson, Fredrik
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Grafisk utvecklingsplattform för signalbehandling - Design och implementation2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    We have different kinds of signal processing everywhere around us in our everyday life, in our cellphones, when we are listening to music, watching TV etc. This makes signal processing a very interesting and important technical area, where the demand of skilled engineers sets the limit of what is possible.

    Working with signal processing requires in-depth knowledge in areas such as mathematics, physics, electronics, and other related areas. For this, it has traditionally been demanded by a talented developer to also master the advanced programming languages such as C / C + + and Assembler.

    This has begun to change; today there are several companies that offer graphical development environments for signal processing, environments where programming skills are not needed anymore, and the focus can be on signal processing instead.

    The goal with this project is to build a corresponding graphical development environment to reach an understanding of what is required of these systems, and also to grasp what opportunities that are available within graphic programming. Inspiration for the work has partly arise from some of the tools available on the market, and partly from previous theses that have been written about graphic programming.

    The challenge lies in creating a program that can execute signal diagrams in real time from given signal blocks, and be able to handle feedback loops in an efficient way and to do so at the lowest "cost" in terms of clock cycles as possible. This should also be compared against to code, compile and run a complete signal diagram directly.

    To increase the usability it should also be possibility to externally manage in real time the parameters of the signal diagram during execution.

    The interface is a separate program, which is to some extent similar to Matlab Simulink, where a signal diagram is drawn up graphically by connecting wires between different signal blocks. This signal scheme is then executed in an additional program that serves as a runtime environment. In this report, the term "signal engine" is used for this program.

    Signal engine is equivalent to the program that should have been run directly into a standalone DSP (Digital Signal Processor) if a more classic design had been selected, but now runs as a separate process in Windows.

  • 342. Andersson, G.
    et al.
    Esfahani, P. M.
    Vrakopoulou, M.
    Margellos, K.
    Lygeros, J.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Dán, György
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Cyber-security of SCADA systems2012In: 2012 IEEE PES Innovative Smart Grid Technologies, ISGT 2012, IEEE , 2012, p. 6175543-Conference paper (Refereed)
    Abstract [en]

    After a general introduction of the VIKING EU FP7 project two specific cyber-attack mechanisms, which have been analyzed in the VIKING project, will be discussed in more detail. Firstly an attack and its consequences on the Automatic Generation Control (AGC) in a power system are investigated, and secondly the cyber security of State Estimators in SCADA systems is scrutinized.

  • 343.
    Andersson, Hans
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. KTH, Superseded Departments, Alfvén Laboratory.
    Currrent disruptions in a magnetised plasma stream1997Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 344.
    Andersson, Helene
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Twente, Netherlands .
    Van Den Berg, A.
    From LOC to LIC: Using individual cells as experimentation platforms2005In: Nanobiotechnology, ISSN 1551-1286, Vol. 1, no 3, p. 319-321Article in journal (Refereed)
    Abstract [en]

    There are many efforts today trying to mimic the properties of single cells in order to design chips that are as efficient as cells. However, cells are nature's nanotechnology engineering at the scale of atoms and molecules. Therefore, it might be better to vision a microchip that utilizes a single cell as experimentation platform. A novel, so-called Lab-in-a-Cell (LIC) concept is described, where advantage is taken of micro/nanotechnological tools to enable precise control of the biochemical cellular environment and possibility to analyze the composition of single cells.

  • 345.
    Andersson, Jerker
    et al.
    KTH, School of Electrical Engineering (EES).
    Avemo, Jonas
    KTH, School of Electrical Engineering (EES).
    Brytning av månbaserat 3He för användning som fusionsbränsle2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 346.
    Andersson, Joel
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Minimering av förväntad reparationskostnad, I2007Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 347.
    Andersson, Karl-Johan
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Komponentuppdelning av elnätetpå lokalnivå2008Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sweden will, in accordance with the EU-directive 2003/54/EC, move from post-regulating the electricity power grid-tariffs by using a fictitious grid, to a regulation in advance which uses the actual power grid as a starting point. For this purpose a component breakdown of the grid needs to be made to determine the value of the network and by that the tariff price that is reasonable for the network business in question to charge.

    The primary breakdown criteria is the voltage-level and type of region. Voltage-level is crucial for the cost and complexity of a grid-part, because the higher the voltagelevel is, there are more and stricter laws and rules to follow. This work is limited to the distributionpart of the grid, in other words voltage levels from 20 kV and below.

    The type of region is crucial to the type of components you can and want to use. In city environments both overhead-wires and independent substations are undesirable for both practical, safety and aesthetic reasons. Overhead-wires is more common in rural areas, where it´s not economically justifiable to use ground-cable, so the cheaper air-alternative is chosen. An interference in a city environment is also much more costly than one in a urban or rural setting, which is crucial for a component's value. The value of an existing substation in a city environment is much higher than a station of similar nature in the countryside.

    The components that are taken into account are overhead-wires, ground-cables and substations. These come in a variety of aberrations that are used as preconditions for the grouping of components.

    Based on the components actual presence in the network and their electrical properties they are divided into groups, which together with type of region and voltage-level can determine the component's actual value and thus be able to give a value to the power-grid in question.

  • 348.
    Andersson, Marika
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Investigation of dynamic information in reactor noise measurements2004Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this master´s thesis is to investigate if it is possible to extract more dynamic information out of physical signals from nuclear reactor noise measurements than what is possible today. This was achieved by investigating methods to examine and determine the process signal quality, and studying the corresponding transfer function. Accurate measurements of for example the core stability and the control system interference are required for detailed process diagnostics.

    By analysing real reactor signals, (here neutron flux and reactor pressure), it is observed that they are correlated. Becuase the structure of the real system is not perfectly known, two hypothesis have been made regarding the real system. Identification of the transfer function of the two simulated systems have been done using Matlab with process noise added to the system, with measurement noise added to the system, and with feedback added to the system. The identification models ARX (Auto Regression Moving Average), AR (a special case of ARX) and BJ (Box-Jenkin) have been used.

    From the results, it follows difficult to adapt a good transfer function using the ARX model to data. This is because of bad coherence. When identifying the transfer function using a spectrum, an AR model, a good approximation was seen, since the approximation does agree well with the spectral estimate. Here the input is not used.

    When identifying using an uncorrelated noise vector as input, we get a bias in the approximation, since the output can not be fully explained by the input signal.

  • 349.
    Andersson, Mattias
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Coding and Transmission Strategies for Secrecy2014Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In this thesis we consider several problems relating to information theoretic security. The wiretap channel is the simplest information theoretic setting which takes security into account, and in the first chapters of the thesis we design some practical coding schemes for this channel model.

    First we consider the design of two edge type low density parity check (LDPC) codes for the binary erasure wiretap channel (BEC-WT). For the scenario when the main channel is error free and the wiretapper's channel is a binary erasure channel (BEC) we find secrecy capacity achieving code sequences based on standard LDPC code sequences for the BEC. However, this construction does not work when there are also erasures on the main channel. For this case we develop a method based on linear programming to optimize two edge type degree distributions. Using this method we find code ensembles that perform close to the secrecy capacity of the BEC-WT. We generalize a method of Méasson, Montanari, and Urbanke in order to compute the conditional entropy of the message at the wiretapper. We apply this method to relatively simple ensembles and find very good secrecy performance.

    We then show that Arikan's polar codes can be used to achieve the whole capacity-equivocation region of for any degraded symmetric binary input wiretap channel. We also design capacity achieving polar codes for the decode-and-forward scheme for the physically degraded relay channel, and for the bidirectional broadcast channel with common and confidential messages.

    In the subsequent chapter we consider a Gaussian system model. We show that sparse regression codes (SPARCS) as introduced by Joseph and Barron achieve the secrecy capacity of the additive white Gaussian noise (AWGN) wiretap channel, and can be used to implement the decode-and-forward scheme for the Gaussian relay channel. We also consider secret key agreement using correlated Gaussian random variables and a rate-limited public channel. We show that SPARCs attain the capacity region also for this problem.

    Finally we consider secret key agreement over reciprocal fading channels. We first consider a multiple-antenna setup in the high signal-to-noise-ratio (SNR) regime and propose a scheme based on training and randomness sharing. We then consider a single antenna setup in the low SNR regime, where one of the terminals is only allowed to transmit pilot signals. We propose a bursty transmission scheme based on training and opportunistic transmission using a wiretap channel code, and show that this scheme is optimal.

  • 350.
    Andersson, Mattias
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Coding for the Wiretap Channel2011Licentiate thesis, monograph (Other academic)
    Abstract [en]

    We consider code design for Wyner’s wiretap channel. Optimal coding schemes for this channel require an overall code that is capacity achieving for the main channel, partitioned into smaller subcodes, all of which are capacity achieving for the wiretapper’s channel. To accomplish this we introduce two edge type low density parity check (LDPC) ensembles for the wiretap channel. For the scenario when the main channel is error free and the wiretapper’s channel is a binary erasure channel (BEC) we find secrecy capacity achieving code sequences based on standard LDPC code sequences for the BEC. However, this construction does not work when there are also erasures on the main channel. For this case we develop a method based on linear programming to optimize two edge type degree distributions. Using this method we find code ensembles that perform close to the secrecy capacity of the binary erasure wiretap channel (BEC- WT). We generalize a method of M ́easson, Montanari, and Urbanke in order to compute the conditional entropy of the message at the wire- tapper. This conditional entropy is a measure of how much information is leaked to the wiretapper. We apply this method to relatively simple ensembles and find that they show very good secrecy performance.

    Based on the work of Kudekar, Richardson, and Urbanke, which showed that regular spatially coupled codes are capacity achieving for the BEC, we construct a regular two edge type spatially coupled ensem- ble. We show that this ensemble achieves the whole capacity-equivocation region for the BEC-WT.

    We also find a coding scheme using Arıkans polar codes. These codes achieve the whole capacity-equivocation region for any symmetric binary input wiretap channel where the wiretapper’s channel is degraded with respect to the main channel.

     

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