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  • 1.
    Abari, Farzad Foroughi
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Optimization of Audio Processing algorithms (Reverb) on ARMv6 family of processors2008Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    Audio processing algorithms are increasingly used in cell phones and today’s customers are placing more demands on cell phones. Feature phones, once the advent of mobile phone technology, nowadays do more than just providing the user with MP3 play back or advanced audio effects. These features have become an integral part of medium as well as low-end phones. On the other hand, there is also an endeavor to include as improved quality as possible into products to compete in market and satisfy users’ needs. Tackling the above requirements has been partly satisfied by the advance in hardware design and manufacturing technology. However, as new hardware emerges into market the need for competence to write efficient software and exploit the new features thoroughly and effectively arises. Even though compilers are also keeping up with the new tide space for hand optimized code still exist. Wrapped in the above goal, an effort was made in this thesis to partly cover the competence requirement at Multimedia Section (part of Ericsson Mobile Platforms) to develope optimized code for new processors. Forging persistently ahead with new products, EMP has always incorporated the latest technology into its products among which ARMv6 family of processors has the main central processing role in a number of upcoming products. To fully exploit latest features provided by ARMv6, it was required to probe its new instruction set among which new media processing instructions are of outmost importance. In order to execute DSP-intensive algorithms (e.g. Audio Processing algorithms) efficiently, the implementation should be done in low-level code applying available instruction set. Meanwhile, ARMv6 comes with a number of new features in comparison with its predecessors. SIMD (Single Instruction Multiple Data) and VFP (Vector Floating Point) are the most prominent media processing improvements in ARMv6. Aligned with thesis goals and guidelines, Reverb algorithm which is among one of the most complicated audio features on a hand-held devices was probed. Consequently, its kernel parts were identified and implementation was done both in fixed-point and floating-point using the available resources on hardware. Besides execution time and amount of code memory for each part were measured and provided in tables and charts for comparison purposes. Conclusions were finally drawn based on developed code’s efficiency over ARM compiler’s as well as existing code already developed and tailored to ARMv5 processors. The main criteria for optimization was the execution time. Moreover, quantization effect due to limited precision fixed-point arithmetic was formulated and its effect on quality was elaborated. The outcomes, clearly indicate that hand optimization of kernel parts are superior to Compiler optimized alternative both from the point of code memory as well as execution time. The results also confirmed the presumption that hand optimized code using new instruction set can improve efficiency by an average 25%-50% depending on the algorithm structure and its interaction with other parts of audio effect. Despite its many draw backs, fixed-point implementation remains yet to be the dominant implementation for majority of DSP algorithms on low-power devices.

  • 2.
    Abbas, Muhammad
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    On the Implementation of Integer and Non-Integer Sampling Rate Conversion2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The main focus in this thesis is on the aspects related to the implementation of integer and non-integer sampling rate conversion (SRC). SRC is used in many communication and signal processing applications where two signals or systems having different sampling rates need to be interconnected. There are two basic approaches to deal with this problem. The first is to convert the signal to analog and then re-sample it at the desired rate. In the second approach, digital signal processing techniques are utilized to compute values of the new samples from the existing ones. The former approach is hardly used since the latter one introduces less noise and distortion. However, the implementation complexity for the second approach varies for different types of conversion factors. In this work, the second approach for SRC is considered and its implementation details are explored. The conversion factor in general can be an integer, a ratio of two integers, or an irrational number. The SRC by an irrational numbers is impractical and is generally stated for the completeness. They are usually approximated by some rational factor.

    The performance of decimators and interpolators is mainly determined by the filters, which are there to suppress aliasing effects or removing unwanted images. There are many approaches for the implementation of decimation and interpolation filters, and cascaded integrator comb (CIC) filters are one of them. CIC filters are most commonly used in the case of integer sampling rate conversions and often preferred due to their simplicity, hardware efficiency, and relatively good anti-aliasing (anti-imaging) characteristics for the first (last) stage of a decimation (interpolation). The multiplierless nature, which generally yields to low power consumption, makes CIC filters well suited for performing conversion at higher rate. Since these filters operate at the maximum sampling frequency, therefore, are critical with respect to power consumption. It is therefore necessary to have an accurate and efficient ways and approaches that could be utilized to estimate the power consumption and the important factors that are contributing to it. Switching activity is one such factor. To have a high-level estimate of dynamic power consumption, switching activity equations in CIC filters are derived, which may then be used to have an estimate of the dynamic power consumption. The modeling of leakage power is also included, which is an important parameter to consider since the input sampling rate may differ several orders of magnitude. These power estimates at higher level can then be used as a feed-back while exploring multiple alternatives.

    Sampling rate conversion is a typical example where it is required to determine the values between existing samples. The computation of a value between existing samples can alternatively be regarded as delaying the underlying signal by a fractional sampling period. The fractional-delay filters are used in this context to provide a fractional-delay adjustable to any desired value and are therefore suitable for both integer and non-integer factors. The structure that is used in the efficient implementation of a fractional-delay filter is know as Farrow structure or its modifications. The main advantage of the Farrow structure lies in the fact that it consists of fixed finite-impulse response (FIR) filters and there is only one adjustable fractional-delay parameter, used to evaluate a polynomial with the filter outputs as coefficients. This characteristic of the Farrow structure makes it a very attractive structure for the implementation. In the considered fixed-point implementation of the Farrow structure, closed-form expressions for suitable word lengths are derived based on scaling and round-off noise. Since multipliers share major portion of the total power consumption, a matrix-vector multiple constant multiplication approach is proposed to improve the multiplierless implementation of FIR sub-filters.

    The implementation of the polynomial part of the Farrow structure is investigated by considering the computational complexity of different polynomial evaluation schemes. By considering the number of operations of different types, critical path, pipelining complexity, and latency after pipelining, high-level comparisons are obtained and used to short list the suitable candidates. Most of these evaluation schemes require the explicit computation of higher order power terms. In the parallel evaluation of powers, redundancy in computations is removed by exploiting any possible sharing at word level and also at bit level. As a part of this, since exponents are additive under multiplication, an ILP formulation for the minimum addition sequence problem is proposed.

  • 3.
    Abbas, Muhammad
    et al.
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Oscar
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Johansson, Håkan
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    On the Fixed-Point Implementation of Fractional-Delay Filters Based on the Farrow Structure2013Inngår i: IEEE Transactions on Circuits and Systems Part 1: Regular Papers, ISSN 1549-8328, E-ISSN 1558-0806, Vol. 60, nr 4, 926-937 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, the fixed-point implementation of adjustable fractional-delay filters using the Farrow structure is considered. Based on the observation that the sub-filters approximate differentiators, closed-form expressions for the L-2-norm scaling values at the outputs of each sub-filter as well as at the inputs of each delay multiplier are derived. The scaling values can then be used to derive suitable word lengths by also considering the round-off noise analysis and optimization. Different approaches are proposed to derive suitable word lengths including one based on integer linear programming, which always gives an optimal allocation. Finally, a new approach for multiplierless implementation of the sub-filters in the Farrow structure is suggested. This is shown to reduce register complexity and, for most word lengths, require less number of adders and subtracters when compared to existing approaches.

  • 4.
    Abbas, Muhammad
    et al.
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Oscar
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Johansson, Håkan
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Scaling of fractional delay filters based on the Farrow structure2009Inngår i: Proceedings of IEEE International Symposium on Circuits and Systems, 2009. ISCAS 2009, Piscataway: IEEE , 2009, 489-492 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this work we consider scaling of fractional delay filters using the Farrow structure. Based on the observation that the subfilters approximate the Taylor expansion of a differentiator, we derive estimates of the L2-norm scaling values at the outputs of each subfilter as well as at the inputs of each delay multiplier. The scaling values can then be used to derive suitable wordlengths in a fixed-point implementation.

  • 5.
    Abbas, Taimoor
    et al.
    Lund Univ, Elect & Informat Technol Dept, S-22100 Lund, Sweden..
    Sjöberg, Katrin
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Kåredal, Johan
    Lund Univ, Elect & Informat Technol Dept, S-22100 Lund, Sweden..
    Tufvesson, Fredrik
    Lund Univ, Elect & Informat Technol Dept, S-22100 Lund, Sweden..
    A Measurement Based Shadow Fading Model for Vehicle-to-Vehicle Network Simulations2015Inngår i: International Journal of Antennas and Propagation, ISSN 1687-5869, E-ISSN 1687-5877, 190607Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The vehicle-to-vehicle (V2V) propagation channel has significant implications on the design and performance of novel communication protocols for vehicular ad hoc networks (VANETs). Extensive research efforts have been made to develop V2V channel models to be implemented in advanced VANET system simulators for performance evaluation. The impact of shadowing caused by other vehicles has, however, largely been neglected in most of the models, as well as in the system simulations. In this paper we present a shadow fading model targeting system simulations based on real measurements performed in urban and highway scenarios. The measurement data is separated into three categories, line-of-sight (LOS), obstructed line-of-sight (OLOS) by vehicles, and non-line-of-sight due to buildings, with the help of video information recorded during the measurements. It is observed that vehicles obstructing the LOS induce an additional average attenuation of about 10 dB in the received signal power. An approach to incorporate the LOS/OLOS model into existing VANET simulators is also provided. Finally, system level VANET simulation results are presented, showing the difference between the LOS/OLOS model and a channel model based on Nakagami-m fading.

  • 6.
    Abbaspour, Sara
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Proposing Combined Approaches to Remove ECG Artifacts from Surface EMG Signals2015Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Electromyography (EMG) is a tool routinely used for a variety of applications in a very large breadth of disciplines. However, this signal is inevitably contaminated by various artifacts originated from different sources. Electrical activity of heart muscles, electrocardiogram (ECG), is one of sources which affects the EMG signals due to the proximity of the collection sites to the heart and makes its analysis non-reliable. Different methods have been proposed to remove ECG artifacts from surface EMG signals; however, in spite of numerous attempts to eliminate or reduce this artifact, the problem of accurate and effective de-noising of EMG still remains a challenge. In this study common methods such as high pass filter (HPF), gating method, spike clipping, hybrid technique, template subtraction, independent component analysis (ICA), wavelet transform, wavelet-ICA, artificial neural network (ANN), and adaptive noise canceller (ANC) and adaptive neuro-fuzzy inference system (ANFIS) are used to remove ECG artifacts from surface EMG signals and their accuracy and effectiveness is investigated. HPF, gating method and spike clipping are fast; however they remove useful information from EMG signals. Hybrid technique and ANC are time consuming. Template subtraction requires predetermined QRS pattern. Using wavelet transform some artifacts remain in the original signal and part of the desired signal is removed. ICA requires multi-channel signals. Wavelet-ICA approach does not require multi-channel signals; however, it is user-dependent. ANN and ANFIS have good performance, but it is possible to improve their results by combining them with other techniques. For some applications of EMG signals such as rehabilitation, motion control and motion prediction, the quality of EMG signals is very important. Furthermore, the artifact removal methods need to be online and automatic. Hence, efficient methods such as ANN-wavelet, adaptive subtraction and automated wavelet-ICA are proposed to effectively eliminate ECG artifacts from surface EMG signals. To compare the results of the investigated methods and the proposed methods in this study, clean EMG signals from biceps and deltoid muscles and ECG artifacts from pectoralis major muscle are recorded from five healthy subjects to create 10 channels of contaminated EMG signals by adding the recorded ECG artifacts to the clean EMG signals. The artifact removal methods are also applied to the 10 channels of real contaminated EMG signals from pectoralis major muscle of the left side. Evaluation criteria such as signal to noise ratio, relative error, correlation coefficient, elapsed time and power spectrum density are used to evaluate the performance of the proposed methods. It is found that the performance of the proposed ANN-wavelet method is superior to the other methods with a signal to noise ratio, relative error and correlation coefficient of 15.53, 0.01 and 0.98 respectively.

  • 7.
    Abbaspour, Sara
    et al.
    Amirkabir University of technology,Tehran, Iran.
    Fallah, Ali
    Amirkabir University of technology,Tehran, Iran.
    Removing ECG Artifact from the Surface EMG Signal Using Adaptive Subtraction Technique2014Inngår i: Biomedical Physics and Engineering, ISSN 2251-7200, Vol. 4, nr 1, 33-38 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: The electrocardiogram artifact is a major contamination in the electromyogram signals when electromyogram signal is recorded from upper trunk muscles and because of that the contaminated electromyogram is not useful. Objective: Removing electrocardiogram contamination from electromyogram signals. Methods: In this paper, the clean electromyogram signal, electrocardiogram artifact and electrocardiogram signal were recorded from leg muscles, the pectoralis major muscle of the left side and V4, respectively. After the pre-processing, contaminated electromyogram signal is simulated with a combination of clean electromyogram and electrocardiogram artifact. Then, contaminated electromyogram is cleaned using adaptive subtraction method. This method contains some steps; (1) QRS detection, (2) formation of electrocardiogram template by averaging the electrocardiogram complexes, (3) using low pass filter to remove undesirable artifacts, (4) subtraction. Results: Performance of our method is evaluated using qualitative criteria, power spectrum density and coherence and quantitative criteria signal to noise ratio, relative error and cross correlation. The result of signal to noise ratio, relative error and cross correlation is equal to 10.493, 0.04 and %97 respectively. Finally, there is a comparison between proposed method and some existing methods. Conclusion: The result indicates that adaptive subtraction method is somewhat effective to remove electrocardiogram artifact from contaminated electromyogram signal and has an acceptable result.

  • 8.
    Abbaspour, Sara
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Lindén, Maria
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Gholamhosseini, Hamid
    Auckland University of Technology, New Zealand.
    ECG Artifact Removal from Surface EMG Signal Using an Automated Method Based on Wavelet-ICA2015Inngår i: Studies in Health Technology and Informatics, Volume 211, 2015, 91-97 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This study aims at proposing an efficient method for automated electrocardiography (ECG) artifact removal from surface electromyography (EMG) signals recorded from upper trunk muscles. Wavelet transform is applied to the simulated data set of corrupted surface EMG signals to create multidimensional signal. Afterward, independent component analysis (ICA) is used to separate ECG artifact components from the original EMG signal. Components that correspond to the ECG artifact are then identified by an automated detection algorithm and are subsequently removed using a conventional high pass filter. Finally, the results of the proposed method are compared with wavelet transform, ICA, adaptive filter and empirical mode decomposition-ICA methods. The automated artifact removal method proposed in this study successfully removes the ECG artifacts from EMG signals with a signal to noise ratio value of 9.38 while keeping the distortion of original EMG to a minimum.

  • 9.
    Abdalmoaty, Mohamed
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    A Simulated Maximum Likelihood Method for Estimation of Stochastic Wiener Systems2016Inngår i: 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, 3060-3065 s., 7798727Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper introduces a simulation-based method for maximum likelihood estimation of stochastic Wienersystems. It is well known that the likelihood function ofthe observed outputs for the general class of stochasticWiener systems is analytically intractable. However, when the distributions of the process disturbance and the measurement noise are available, the likelihood can be approximated byrunning a Monte-Carlo simulation on the model. We suggest the use of Laplace importance sampling techniques for the likelihood approximation. The algorithm is tested on a simple first order linear example which is excited only by the process disturbance. Further, we demonstrate the algorithm on an FIR system with cubic nonlinearity. The performance of the algorithm is compared to the maximum likelihood method and other recent techniques.

  • 10.
    Abdalmoaty, Mohamed
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hjalmarsson, Håkan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    On Re-Weighting, Regularization Selection, and Transient in Nuclear Norm Based Identification2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this contribution, we consider the classical problem of estimating an Output Error model given a set of input-output measurements. First, we develop a regularization method based on the re-weighted nuclear norm heuristic. We show that the re-weighting improves the estimate in terms of better fit. Second, we suggest an implementation method that helps in eliminating the regularization parameters from the problem by introducing a constant based on a validation criterion. Finally, we develop a method for considering the effect of the transient when the initial conditions are unknown. A simple numerical example is used to demonstrate the proposed method in comparison to classical and another recent method based on the nuclear norm heuristic.

  • 11.
    Abd-Elrady, Emad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Harmonic signal modeling based on the Wiener model structure2002Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The estimation of frequencies and corresponding harmonic overtones is a problem of great importance in many situations. Applications can, for example, be found in supervision of electrical power transmission lines, in seismology and in acoustics. Generally, a periodic function with an unknown fundamental frequency in cascade with a parameterized and unknown nonlinear function can be used as a signal model for an arbitrary periodic signal. The main objective of the proposed modeling technique is to estimate the fundamental frequency of the periodic function in addition to the parameters of the nonlinear function.

    The thesis is divided into four parts. In the first part, a general introduction to the harmonic signal modeling problem and different approaches to solve the problem are given. Also, an outline of the thesis and future research topics are introduced.

    In the second part, a previously suggested recursive prediction error method (RPEM) for harmonic signal modeling is studied by numerical examples to explore the ability of the algorithm to converge to the true parameter vector. Also, the algorithm is modified to increase its ability to track the fundamental frequency variations.

    A modified algorithm is introduced in the third part to give the algorithm of the second part a more stable performance. The modifications in the RPEM are obtained by introducing an interval in the nonlinear block with fixed static gain. The modifications that result in the convergence analysis are, however, substantial and allows a complete treatment of the local convergence properties of the algorithm. Moreover, the Cramér–Rao bound (CRB) is derived for the modified algorithm and numerical simulations indicate that the method gives good results especially for moderate signal to noise ratios (SNR).

    In the fourth part, the idea is to give the algorithm of the third part the ability to estimate the driving frequency and the parameters of the nonlinear output function parameterized also in a number of adaptively estimated grid points. Allowing the algorithm to automatically adapt the grid points as well as the parameters of the nonlinear block, reduces the modeling errors and gives the algorithm more freedom to choose the suitable grid points. Numerical simulations indicate that the algorithm converges to the true parameter vector and gives better performance than the fixed grid point technique. Also, the CRB is derived for the adaptive grid point technique.

  • 12.
    Abd-Elrady, Emad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Nonlinear Approaches to Periodic Signal Modeling2005Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Periodic signal modeling plays an important role in different fields. The unifying theme of this thesis is using nonlinear techniques to model periodic signals. The suggested techniques utilize the user pre-knowledge about the signal waveform. This gives these techniques an advantage as compared to others that do not consider such priors.

    The technique of Part I relies on the fact that a sine wave that is passed through a static nonlinear function produces a harmonic spectrum of overtones. Consequently, the estimated signal model can be parameterized as a known periodic function (with unknown frequency) in cascade with an unknown static nonlinearity. The unknown frequency and the parameters of the static nonlinearity are estimated simultaneously using the recursive prediction error method (RPEM). A treatment of the local convergence properties of the RPEM is provided. Also, an adaptive grid point algorithm is introduced to estimate the unknown frequency and the parameters of the static nonlinearity in a number of adaptively estimated grid points. This gives the RPEM more freedom to select the grid points and hence reduces modeling errors.

    Limit cycle oscillations problem are encountered in many applications. Therefore, mathematical modeling of limit cycles becomes an essential topic that helps to better understand and/or to avoid limit cycle oscillations in different fields. In Part II, a second-order nonlinear ODE is used to model the periodic signal as a limit cycle oscillation. The right hand side of the ODE model is parameterized using a polynomial function in the states, and then discretized to allow for the implementation of different identification algorithms. Hence, it is possible to obtain highly accurate models by only estimating a few parameters.

    In Part III, different user aspects for the two nonlinear approaches of the thesis are discussed. Finally, topics for future research are presented.

  • 13.
    Abd-Elrady, Emad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Söderström, Torsten
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Wigren, Torbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Periodic signal analysis using orbits of nonlinear ODEs based on the Markov estimate2004Konferansepaper (Fagfellevurdert)
  • 14.
    Abd-Elrady, Emad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Söderström, Torsten
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Wigren, Torbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Periodic signal modeling based on Liénard's equation2003Rapport (Annet vitenskapelig)
  • 15.
    Abd-Elrady, Emad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Söderström, Torsten
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Wigren, Torbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Periodic signal modeling based on Liénard's equation2004Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 49, nr 10, 1773-1778 s.Artikkel i tidsskrift (Fagfellevurdert)
  • 16.
    Abedan Kondori, Farid
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Bring Your Body into Action: Body Gesture Detection, Tracking, and Analysis for Natural Interaction2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Due to the large influx of computers in our daily lives, human-computer interaction has become crucially important. For a long time, focusing on what users need has been critical for designing interaction methods. However, new perspective tends to extend this attitude to encompass how human desires, interests, and ambitions can be met and supported. This implies that the way we interact with computers should be revisited. Centralizing human values rather than user needs is of the utmost importance for providing new interaction techniques. These values drive our decisions and actions, and are essential to what makes us human. This motivated us to introduce new interaction methods that will support human values, particularly human well-being.

    The aim of this thesis is to design new interaction methods that will empower human to have a healthy, intuitive, and pleasurable interaction with tomorrow’s digital world. In order to achieve this aim, this research is concerned with developing theories and techniques for exploring interaction methods beyond keyboard and mouse, utilizing human body. Therefore, this thesis addresses a very fundamental problem, human motion analysis.

    Technical contributions of this thesis introduce computer vision-based, marker-less systems to estimate and analyze body motion. The main focus of this research work is on head and hand motion analysis due to the fact that they are the most frequently used body parts for interacting with computers. This thesis gives an insight into the technical challenges and provides new perspectives and robust techniques for solving the problem.

  • 17.
    Abedan Kondori, Farid
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Liu, Li
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Li, Haibo
    KTH Royal Institue of Technology, Department of Media Technology and Interaction Design, School of Computer Science and Communication.
    Telelife: An Immersive Media Experience for Rehabilitation2014Konferansepaper (Fagfellevurdert)
  • 18. Abedan Kondori, Farid
    et al.
    Yousefi, Shahrouz
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och interaktionsdesign, MID. Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Smart Baggage in Aviation2011Inngår i: Proceedings - 2011 IEEE International Conferences on Internet of Things and Cyber, Physical and Social Computing, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Nowadays, the Internet has dramatically changed the way people take the normal course of actions. By the recent growth of the Internet, connecting different objects to users through mobile phones and computers is no longer a dream. Aviation industry is one of the areas which have a strong potential to benefit from the Internet of Things. Among many problems related to air travel, delayed and lost luggage are the most common and irritating. Therefore, this paper suggests anew baggage control system, where users can simply track their baggage at the airport to avoid losing them. Attaching a particular pattern on the bag, which can be detected and localized from long distance by an ordinary camera, users are able to track their baggage. The proposed system is much cheaper than previous implementations and does not require sophisticated equipment.

  • 19.
    Abedan Kondori, Farid
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Yousefi, Shahrouz
    KTH Royal Institute of Technology, Department of Media Technology and Interaction Design.
    Kouma, Jean-Paul
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Liu, Li
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Li, Haibo
    KTH Royal Institute of Technology, Department of Media Technology and Interaction Design.
    Direct hand pose estimation for immersive gestural interaction2015Inngår i: Pattern Recognition Letters, ISSN 0167-8655, E-ISSN 1872-7344, Vol. 66, 91-99 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a novel approach for performing intuitive gesture based interaction using depth data acquired by Kinect. The main challenge to enable immersive gestural interaction is dynamic gesture recognition. This problem can be formulated as a combination of two tasks; gesture recognition and gesture pose estimation. Incorporation of fast and robust pose estimation method would lessen the burden to a great extent. In this paper we propose a direct method for real-time hand pose estimation. Based on the range images, a new version of optical flow constraint equation is derived, which can be utilized to directly estimate 3D hand motion without any need of imposing other constraints. Extensive experiments illustrate that the proposed approach performs properly in real-time with high accuracy. As a proof of concept, we demonstrate the system performance in 3D object manipulation On two different setups; desktop computing, and mobile platform. This reveals the system capability to accommodate different interaction procedures. In addition, a user study is conducted to evaluate learnability, user experience and interaction quality in 3D gestural interaction in comparison to 2D touchscreen interaction.

  • 20. Abedan Kondori, Farid
    et al.
    Yousefi, Shahrouz
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och interaktionsdesign, MID.
    Li, Haibo
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och interaktionsdesign, MID.
    Direct Head Pose Estimation Using Kinect-type Sensors2014Inngår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911XArtikkel i tidsskrift (Fagfellevurdert)
  • 21.
    Abedan Kondori, Farid
    et al.
    Umeå universitet.
    Yousefi, Shahrouz
    KTH Royal Institute of Technology.
    Li, Haibo
    KTH Royal Institute of Technology.
    Direct three-dimensional head pose estimation from Kinect-type sensors2014Inngår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 50, nr 4, 268-270 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A direct method for recovering three-dimensional (3D) head motion parameters from a sequence of range images acquired by Kinect sensors is presented. Based on the range images, a new version of the optical flow constraint equation is derived, which can be used to directly estimate 3D motion parameters without any need of imposing other constraints. Since all calculations with the new constraint equation are based on the range images, Z(xyt), the existing techniques and experiences developed and accumulated on the topic of motion from optical flow can be directly applied simply by treating the range images as normal intensity images I(xyt). In this reported work, it is demonstrated how to employ the new optical flow constraint equation to recover the 3D motion of a moving head from the sequences of range images, and furthermore, how to use an old trick to handle the case when the optical flow is large. It is shown, in the end, that the performance of the proposed approach is comparable with that of some of the state-of-the-art approaches that use range data to recover 3D motion parameters.

  • 22.
    Abedan Kondori, Farid
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Yousefi, Shahrouz
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Li, Haibo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Direct three-dimensional head pose estimation from Kinect-type sensors2014Inngår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 50, nr 4, 268-270 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A direct method for recovering three-dimensional (3D) head motion parameters from a sequence of range images acquired by Kinect sensors is presented. Based on the range images, a new version of the optical flow constraint equation is derived, which can be used to directly estimate 3D motion parameters without any need of imposing other constraints. Since all calculations with the new constraint equation are based on the range images, Z(xyt), the existing techniques and experiences developed and accumulated on the topic of motion from optical flow can be directly applied simply by treating the range images as normal intensity images I(xyt). In this reported work, it is demonstrated how to employ the new optical flow constraint equation to recover the 3D motion of a moving head from the sequences of range images, and furthermore, how to use an old trick to handle the case when the optical flow is large. It is shown, in the end, that the performance of the proposed approach is comparable with that of some of the state-of-the-art approaches that use range data to recover 3D motion parameters.

  • 23.
    Abedan Kondori, Farid
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Yousefi, Shahrouz
    KTH Royal Institute of Technology, Department of Media Technology and Interaction Design.
    Liu, Li
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Li, Haibo
    KTH Royal Institute of Technology, Department of Media Technology and Interaction Design.
    Head operated electric wheelchair2014Inngår i: IEEE Southwest Symposium on Image Analysis and Interpretation (SSIAI 2014), IEEE , 2014, 53-56 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Currently, the most common way to control an electric wheelchair is to use joystick. However, there are some individuals unable to operate joystick-driven electric wheelchairs due to sever physical disabilities, like quadriplegia patients. This paper proposes a novel head pose estimation method to assist such patients. Head motion parameters are employed to control and drive an electric wheelchair. We introduce a direct method for estimating user head motion, based on a sequence of range images captured by Kinect. In this work, we derive new version of the optical flow constraint equation for range images. We show how the new equation can be used to estimate head motion directly. Experimental results reveal that the proposed system works with high accuracy in real-time. We also show simulation results for navigating the electric wheelchair by recovering user head motion.

  • 24. Abedan Kondori, Farid
    et al.
    Yousefi, Shahrouz
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och interaktionsdesign, MID.
    Liu, Li
    Li, Haibo
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och interaktionsdesign, MID. Nanjing University of Posts and Telecommunications, Nanjing, China .
    Head Operated Electric Wheelchair2014Inngår i: Proceedings of the IEEE Southwest Symposium on Image Analysis and Interpretation, 2014, 53-56 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Currently, the most common way to control an electric wheelchair is to use joystick. However, there are some individuals unable to operate joystick-driven electric wheelchairs due to sever physical disabilities, like quadriplegia patients. This paper proposes a novel head pose estimation method to assist such patients. Head motion parameters are employed to control and drive an electric wheelchair. We introduce a direct method for estimating user head motion, based on a sequence of range images captured by Kinect. In this work, we derive new version of the optical flow constraint equation for range images. We show how the new equation can be used to estimate head motion directly. Experimental results reveal that the proposed system works with high accuracy in real-time. We also show simulation results for navigating the electric wheelchair by recovering user head motion.

  • 25.
    Abelsson, Sara
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Propagation Measurements at 3.5 GHz for WiMAX2007Independent thesis Advanced level (degree of Master (One Year))Oppgave
    Abstract [en]

    Propagation measurements at the frequency 3.5 GHz for the WiMAX technology have been conducted. The purpose of these measurements is that a coverage analysis should be accomplished. The mathematical software package MATLAB has been used to analyze the collected data from the measurement campaign. Path loss models have also been used and a comparison between these models and the collected data has been performed. An analysis prediction tool from an application called WRAP has also been used in the comparison with the collected data. In this thesis, diff

  • 26.
    Abou Raas, Mhd Jihad
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap.
    Wall Compensation Algorithms for M-sequence UWB Radar2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A technique for wall compensation in the ultra-wideband (UWB) through-wall imaging radar is presented. The UWB system can be utilize in high precision measurements, but due to phase distortion and amplitude attenuation caused by the wall the precision is limited, the target is displaced, and the image is defocused. 

    In order to mitigate the wall effects, two methods are applied in this project. First, the unknown wall transfer function is estimated using real data measurements to design the inverse filter. Secondly, FIR Wiener filter is designed to improve the received m-sequence. After all, each method is tested using three parameters, the signal to noise ratio (SNR), the signal to clutter ratio (SCR), and the relative position error (RPE). 

    The inverse filter can eliminate the wall effects very well; it could correct not only the position of the target but also the image defocus. The new method can give improve the image quality and that can extend the use of UWB radar in many applications. 

  • 27.
    Abrahamsson, Richard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Estimation Problems in Array Signal Processing, System Identification, and Radar Imagery2006Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis is concerned with parameter estimation, signal processing, and applications.

    In the first part, imaging using radar is considered. More specifically, two methods are presented for estimation and removal of ground-surface reflections in ground penetrating radar which otherwise hinder reliable detection of shallowly buried landmines. Further, a study of two autofocus methods for synthetic aperture radar is presented. In particular, we study their behavior in scenarios where the phase errors leading to cross-range defocusing are of a spatially variant kind.

    In the subsequent part, array signal processing and optimal beamforming is regarded. In particular, the phenomenon of signal cancellation in adaptive beamformers due to array perturbations, signal correlated interferences and limited data for covariance matrix estimation is considered. For the general signal cancellation problem, a class of improved adaptive beamformers is suggested based on ridge-regression. Another set of methods is suggested to mitigate signal cancellation due to correlated signal and interferences based on a novel way of finding a characterization of the interference subspace from observed array data. Further, a new minimum variance beamformer is presented for high resolution non-parametric spatial spectrum estimation in cases where the impinging signals are correlated. Lastly, a multitude of enhanced covariance matrix estimators from the statistical literature are studied as an alternative to other robust adaptive beamforming methods. The methods are also applied to space-time adaptive processing where limited data for covariance matrix estimation is a common problem.

    In the third and final part the estimation of the parameters of a general bilinear problem is considered. The bilinear model is motivated by the application of identifying submarines from their electromagnetic signature and by the identification of a Hamerstein-Wiener model of a non-linear dynamic system. An efficient approximate maximum-likelihood method with closed form solution is suggested for estimating the bilinear model parameters.

  • 28. Abtahi, F
    et al.
    Seoane, F
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Lindecrantz, K
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Electrical bioimpedance spectroscopy in time-variant systems: Is undersampling always a problem?2014Inngår i: Journal of Electrical Bioimpedance, ISSN 1891-5469, E-ISSN 1891-5469, Vol. 5, nr 1, 28-33 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During the last decades, Electrical Bioimpedance Spectroscopy (EBIS) has been applied mainly by using the frequency-sweep technique, across a range of many different applications. Traditionally, the tissue under study is considered to be time-invariant and dynamic changes of tissue activity are ignored by treating the changes as a noise source. A new trend in EBIS is simultaneous electrical stimulation with several frequencies, through the application of a multi-sine, rectangular or other waveform. This method can provide measurements fast enough to sample dynamic changes of different tissues, such as cardiac muscle. This high sampling rate comes at a price of reduction in SNR and the increase in complexity of devices. Although the frequency-sweep technique is often inadequate for monitoring the dynamic changes in a variant system, it can be used successfully in applications focused on the time-invariant or slowly-variant part of a system. However, in order to successfully use frequency-sweep EBIS for monitoring time-variant systems, it is paramount to consider the effects of aliasing and especially the folding of higher frequencies, on the desired frequency e.g. DC level. This paper discusses sub-Nyquist sampling of thoracic EBIS measurements and its application in the case of monitoring pulmonary oedema. It is concluded that by considering aliasing, and with proper implementation of smoothing filters, as well as by using random sampling, frequency-sweep EBIS can be used for assessing time-invariant or slowly-variant properties of time-variant biological systems, even in the presence of aliasing. In general, undersampling is not always a problem, but does always require proper consideration.

  • 29.
    Abtahi, Farhad
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Aspects of Electrical Bioimpedance Spectrum Estimation2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Electrical bioimpedance spectroscopy (EBIS) has been used to assess the status or composition of various types of tissue, and examples of EBIS include body composition analysis (BCA) and tissue characterisation for skin cancer detection. EBIS is a non-invasive method that has the potential to provide a large amount of information for diagnosis or monitoring purposes, such as the monitoring of pulmonary oedema, i.e., fluid accumulation in the lungs. However, in many cases, systems based on EBIS have not become generally accepted in clinical practice. Possible reasons behind the low acceptance of EBIS could involve inaccurate models; artefacts, such as those from movements; measurement errors; and estimation errors. Previous thoracic EBIS measurements aimed at pulmonary oedema have shown some uncertainties in their results, making it difficult to produce trustworthy monitoring methods. The current research hypothesis was that these uncertainties mostly originate from estimation errors. In particular, time-varying behaviours of the thorax, e.g., respiratory and cardiac activity, can cause estimation errors, which make it tricky to detect the slowly varying behaviour of this system, i.e., pulmonary oedema.

    The aim of this thesis is to investigate potential sources of estimation error in transthoracic impedance spectroscopy (TIS) for pulmonary oedema detection and to propose methods to prevent or compensate for these errors.   This work is mainly focused on two aspects of impedance spectrum estimation: first, the problems associated with the delay between estimations of spectrum samples in the frequency-sweep technique and second, the influence of undersampling (a result of impedance estimation times) when estimating an EBIS spectrum. The delay between frequency sweeps can produce huge errors when analysing EBIS spectra, but its effect decreases with averaging or low-pass filtering, which is a common and simple method for monitoring the time-invariant behaviour of a system. The results show the importance of the undersampling effect as the main estimation error that can cause uncertainty in TIS measurements.  The best time for dealing with this error is during the design process, when the system can be designed to avoid this error or with the possibility to compensate for the error during analysis. A case study of monitoring pulmonary oedema is used to assess the effect of these two estimation errors. However, the results can be generalised to any case for identifying the slowly varying behaviour of physiological systems that also display higher frequency variations.  Finally, some suggestions for designing an EBIS measurement system and analysis methods to avoid or compensate for these estimation errors are discussed.

  • 30.
    Abu-Hamam, Anas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Li, Haibo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Georgakis, Apostolos
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Understanding Web Users Behaviour From A Web Video Camera2003Rapport (Annet vitenskapelig)
    Abstract [en]

    To develop a Real-Time system, which can capture and track the web user’s head motion. Based on the head motion information, the system should be able to identify whether the user is interested in the current homepage or not. A future system property would be to find out in which area of the homepage the user’s interest is moving.

  • 31. Abu-Shaban, Z.
    et al.
    Bhavani Shankar Mysore, R.
    Mehrpouyan, H.
    Ottersten, Björn
    SnT - Univ. of Luxembourg, Luxembourg, Luxembourg.
    Enhanced List-based Group-wise overloaded receiver with application to satellite reception2014Inngår i: 2014 IEEE International Conference on Communications (ICC), IEEE conference proceedings, 2014, 5616-5621 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The market trends towards the use of smaller dish antennas for TV satellite receivers, as well as the growing density of broadcasting satellites in orbit require the application of robust adjacent satellite interference (ASI) cancellation algorithms at the receivers. The wider beamwidth of a small size dish and the growing number of satellites in orbit impose an overloaded scenario, i.e., a scenario where the number of transmitting satellites exceeds the number of receiving antennas. For such a scenario, we present a two stage receiver to enhance signal detection from the satellite of interest, i.e., the satellite that the dish is pointing to, while reducing interference from neighboring satellites. Towards this objective, we propose an enhanced List-based Group-wise Search Detection (LGSD) receiver architecture that takes into account the spatially correlated additive noise and uses the signal-to-interference-plus-noise ratio (SINR) maximization criterion to improve detection performance. Simulations show that the proposed receiver structure enhances the performance of satellite systems in the presence of ASI when compared to existing methods.

  • 32. Abu-Shaban, Z.
    et al.
    Mehrpouyan, H.
    Grotz, J.
    Ottersten, Björn
    SnT - University of Luxembourg, Luxembourg .
    Overloaded satellite receiver using SIC with hybrid beamforming and ML detection2013Inngår i: 2013 IEEE 14th Workshop on Signal Processing Advances in Wireless Communications (SPAWC), New York: IEEE , 2013, 450-454 s.Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, a new receiver structure that is intended to detect the signals from multiple adjacent satellites in the presence of other interfering satellites is proposed. We tackle the worst case interference conditions, i.e., it is assumed that uncoded signals that fully overlap in frequency arrive at a multiple-element small-size parabolic antenna in a spatially correlated noise environment. The proposed successive interference cancellation (SIC) receiver, denoted by SIC Hy/ML, employs hybrid beamforming and disjoint maximum likelihood (ML) detection. Depending on the individual signals spatial position, the proposed SIC Hy/ML scheme takes advantage of two types of beamformers: a maximum ratio combining (MRC) beamformer and a compromised array response (CAR) beamformer. The performance of the proposed receiver is compared to an SIC receiver that uses only MRC beamforming scheme with ML detection for all signals, a joint ML detector, and a minimum mean square error detector. It is found that SIC Hy/ML outperforms the other schemes by a large margin.

  • 33.
    Abuzohri, Ahmed
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Effektförstärkare med strömkontroll2012Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Energin är ett begrepp som används dagligen i vårt samhälle. Energin kan inte skapas men däremot kan den omvandlas till olika former, förbrukas och lagras i vissa fall. Men att omvandla energi från en form till en annan form för att sedan lagra den är en av dagens stora utmaningar inom tekniken då vi måste följa de regler som naturen dikterar. Forskning på detta område har pågått i flera decennier för att kunna ta fram lämpliga och effektiva sätt att lagra energi på. Svänghjul-system är ett sådant sätt där man kan lagra energi under begränsad tid.

    I mitt examensarbete har jag utnyttjat kunskapen som jag har lärt mig från elektronik kurserna för att konstruera en effektförstärkare med strömkontroll som användes för att driva ett svänghjul-system. Förstärkaren har byggts med elektronikkomponenter och styrs från datorn med m.h.a. styrprogrammet LabVIEW som kommunicerar med hårdvaran och kontrollerar svänghjulets rörelse.

  • 34.
    Adam, Wettring
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Adaptive Filtering and Nonlinear Models for Post-processing of Weather Forecasts2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Kalman filters have been used by SMHI to improve the quality of their forecasts. Until now they have used a linear underlying model to do this. In this thesis it is investigated whether the performance can be improved by the use of nonlinear models such as polynomials and neural networks. The results suggest that an improvement is hard to achieve by this approach and that it is likely not worth the effort to implement a nonlinear model.

  • 35.
    Adapa, Nagaswaroopa
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Bollu, Sravya
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Performance analysis of different adapative algorithms based on acoustic echo cancellation2013Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    In modern telecommunication systems like hands-free and teleconferencing systems, the problem arise during conversation is the creation of an acoustic echo. This problem degrades the quality of the information signal. All speech processing equipments like noise cancelling headphones and hearing aids should be able to filter different kinds of interfering signals and produce a clear sound to the listener. Currently, echo cancellation is a most interesting and challenging task in any communication system. Echo is the delayed and degraded version of original signal which travels back to its source after several reflections. Eliminating this effect without affecting the original quality of the speech is a challenge of research in present days. Echo cancellation in voice communication is a process of removing the echo to improve the clarity and quality of the voice signals. In our thesis we mainly focused on the acoustic echo cancellation in a closed room using adaptive filters. The Acoustic echo cancellation with adaptive filtering technique will more accurately enhance the speech quality in hands free communication systems. The main aim of using adaptive algorithms for echo cancellation is to achieve higher ERLE at higher rate of convergence with low complexity. The adaptive algorithms NLMS, APA and RLS are implemented using MATLAB. These algorithms are tested with the simulation of echo occurring environment by using constant room dimensions , microphone and source positions. The performance of the NLMS, APA and RLS are evaluated in terms ERLE and misalignment. The results show that RLS algorithm achieve good performance with more computational complexity comparing with the NLMS and APA algorithms. The NLMS algorithm has very low computational complexity comparing to RLS and APA algorithms. The results are taken for both input signal as speech signal and noise separately and plotted in the results section.

  • 36.
    ADHIKARLA, VAMSI KIRAN
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    3D VIDEO FORMAT CONVERSION2011Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    The main aim of this thesis work is to find/implement various methods that convert Conventional Stereoscopic 3D Video (CSV) to Multiview video (MVV). The work investigates different methods that can produce multiple views given a stereoscopic pair from a frame of a particular video sequence and continues with the process of selecting the best among investigated methods that has optimum quality and speed. In contrast to the existing algorithms, this work disregards the physical depth but instead focus on pixel value correspondence. The intermediate view generation in this work is not considered as a geometrical problem, but a morphing problem. Different morphing algorithms (mesh, field and thin plate spline morphing techniques) are considered for conversion. Performance of each morphing algorithm is in turn compared using different correspondence matching techniqes. The investigated methods aim to produce arbitrary number of novel synthesized camera views from a sparse view set. Mesh morphing algorithm is found to be a better candidate in terms of signal to noise ratio, but requires accurate correspondences at edges of an object in a particular scene and also needs more execution time to generate more number of views. A new approach to field morphing has been introduced in this thesis work, which performs better in terms of execution time and also found to produce intermediate views with reasonable signal to noise ratio. This approach is observed to bring good trade off between speed and accuracy. This conversion has an advantage it can be used as a decompression mechanism that can produce multiple views required for an Autostereoscopic 3D display from a stereoscopic left and right pair. This approach also brings the benefit of backward compatibility as present standards for CSV may be used to provide multiview 3D video to high fidelity Autostereoscopic 3D displays of the future. This work has applications in free view point television, video conferencing systems etc.,

  • 37. Adolfsson, Stefan
    On Automatic Detection of Burn-through Using a Parametric Model1995Rapport (Annet vitenskapelig)
  • 38. Adolfsson, Stefan
    Quality Monitoring in Pulsed GMA Welding Using Modern Signal Processing Methods1995Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 39. Adolfsson, Stefan
    Quility Monitoring in Robotised Short Circuiting GMA Welding1997Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper addresses the problem of automatic monitoring the weld quality produced by robotised short arc welding. A simple statistical change detection algorithm for the weld quality, recursive Sequential Probability Ratio Test (SPRT), is used. The algorithm may equivalently be viewed as a cumulative sum (CUSUM) - type test. The test statistics is based upon the variance of the amplitude of the weld voltage. The performance of the algorithm is evaluated using experimental data. The results obtained from the algorithm indicate that it is possible to detect changes in the weld quality automatically and on-line.

  • 40. Adolfsson, Stefan
    et al.
    Bahrami, Ali
    Bolmsjö, Gunnar
    Claesson, Ingvar
    Automatic quality monitoring in robotised GMA welding using a repeated sequential probability ratio test method1997Inngår i: International Journal for the Joining of Materials, ISSN 0905-6866, Vol. 9, nr 1, 2-8 s.Artikkel i tidsskrift (Fagfellevurdert)
  • 41. Adolfsson, Stefan
    et al.
    Bahrami, Ali
    Claesson, Ingvar
    A Sequential Probability Ratio Test Method for Quality Monitoring in Robotised GMA Welding1997Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper deals with the problem of automatic monitoring the weld quality when welding with Gas Metal Arc (GMA) in short circuiting mode. Experiments with two different types of T-joints are performed in order to provoke optimal and non-optimal welding conditions. During the experiments, voltage and current are measured from the welding process. A simple statistical change detection algorithm for the weld quality, the repeated Sequential Probability Ratio Test (SPRT), is used. The algorithm can equivalently be viewed as a cumulative sum (CUSUM) - type test. The test statistics is based upon the fluctuations of amplitude in the weld voltage. It is shown that the fluctuations of the weld voltage amplitude decreases when the welding process is not operating under optimal condition. The results obtained from the experiments indicate that it is possible to detect changes in the weld quality automatically and on-line.

  • 42. Adolfsson, Stefan
    et al.
    Bahrami, Ali
    Claesson, Ingvar
    Quality Monitoring in Robotised Welding using Sequential Probability Ratio test1996Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper addresses the problem of automatic monitoring the weld quality produced by robotised short arc welding. A simple statistical change detection algorithm for the weld quality, recursive sequential probability ratio test (SPRT), is used. The algorithm may equivalently be viewed as a cumulative sum (CUSUM) type test. The test statistics is based upon the variance of the amplitude of the weld voltage. It is shown that the variance of the weld voltage amplitude decreases when the welding process is not operating under optimal condition. The performance of the algorithm is evaluated using experimental data. The results obtained from the algorithm indicate that it is possible to detect changes in the weld quality automatically and on-line

  • 43. Adolfsson, Stefan
    et al.
    Bahrami, Ali
    Claesson, Ingvar
    Bolmsjö, Gunnar
    On-line quality monitoring in short: circuit gas metal arc welding1999Inngår i: Welding Journal, ISSN 0043-2296, Vol. 78, nr 2, 59S-73S s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper addresses the problems involved in the automatic monitoring of the weld quality produced by robotized short-arc welding. A simple statistical change detection algorithm for the weld quality, the repeated Sequential Probability Ratio Test (SPRT), was used. The algorithm may similarly be viewed as a cumulative sum (CUSUM) type test, and is well-suited to detecting sudden minor changes in the monitored test statistic. The test statistic is based on the variance of the weld voltage, wherein it will be shown that the variance decreases when the welding process is not operating under optimal conditions. The performance of the algorithm is assessed through the use of experimental data. The results obtained from the algorithm show that it is possible to detect changes in weld quality automatically and on-line.

  • 44. Adolfsson, Stefan
    et al.
    Ericson, Klas
    Grennberg, Anders
    Automatic Detection of Burn-through in GMA Welding Using a Parametric Model1996Inngår i: Mechanical Systems & Signal Processing, ISSN 0888-3270 , Vol. 10, nr 5, 633-651 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper addresses the problem of automatic detection of burn-through in weld joints. Gas metal are (GMA) welding with pulsed current is used, and welding voltage and current are recorded. As short-circuitings are common between the welding electrode and the work piece during burn-through, a short-circuit detector is developed to detect these events. To detect another specific characteristic of burn-through-a broadband long-lasting voltage component-this detector is combined with a square-law detector. This second detector is based on a non-linear modification of an autoregressive model with extra input (ARX-model) of the welding process. The results obtained from this compound detector indicate that it is possible to detect burn-through in the welds automatically. The work also indicates that it is possible to design an on-line monitoring system for robotic GMA welding.

  • 45. Adolfsson, Stefan
    et al.
    Ericson, Klas
    Gustavsson, Jan-Olof
    Ågren, Björn
    Quality Monitoring for Pulsed Arc Welding1994Konferansepaper (Fagfellevurdert)
  • 46. Adolfsson, Stefan
    et al.
    Ericson, Klas
    Ågren, Björn
    On Automatic Detection of Burn-through in GMA Welding: Weld Voltage Analysis1995Rapport (Annet vitenskapelig)
  • 47.
    Adolfsson, Stefan
    et al.
    Luleå tekniska universitet.
    Ericsson, Klas
    Luleå tekniska universitet.
    Grennberg, Anders
    Automatic detection of burn-through in GMA welding using a parametric model1996Inngår i: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 10, nr 5, 633-651 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper addresses the problem of automatic detection of burn-through in weld joints. Gas metal arc (GMA) welding with pulsed current is used, and welding voltage and current are recorded. As short-circuitings are common between the welding electrode and the work piece during burn-through, a short-circuit detector is developed to detect these events. To detect another specific characteristic of burn-through - this detector is combined with a square-law detector. This second detector is based on a non-linear modification of an autoregressive model with extra input (ARX-model) of the welding process. The results obtained from this compound detector indicate that it is possible to detect burn-through in the welds automatically. The work also indicates that it is possible to design an on-line monitoring system for robotic GMA welding.

  • 48.
    af Ekenstam, Love
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Modellering av signalbehandlingen i ett cochleaimplantat och utvärdering av modellen.2014Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Ett program som simulerar signalbehandlingen i ett cochleaimplantat med signalbehandlingsstrategin ACE (Advanced Combined Encoder) har konstruerats. Programmets främsta syfte är att i förväg prova ut inställningar i ett cochleaimplantat och genom detta försöka förutsäga olika användares individuella inställningar.

     

    Programmet har validerats med utsignaler bearbetade av Cochlear Limited i deras egenkonstruerade Matlab-modul för forskning inom cochleaimplantat, NMT (Nucleus Matlab Toolbox). Samma insignal som använts av Cochlear Limited har processats av programmet och utsignalerna från detta jämfördes med utsignalerna från NMT. De bägge utsignalerna, producerade med samma inställningar, stämde bra överens.

     

    Komprimeringsfunktionen i programmet, som är en vital del av signalbehandlingen, visade sig stämma bra överens med NMT:s komprimeringsfunktion, sånär som på en relativ minskning av värdet vid starka insignaler. Programmet ska nu användas på Cochleaimplantat-sektionen vid Uppsala Akademiska sjukhus för att pröva ut individuella inställningar till användare av cochleaimplantat. Förhoppningen är att bättre inställningar ska leda till bättre talförståelse och i förlängningen, bättre upplevelse av musik.

  • 49.
    Afaq, Muhammad
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Faheem, Sahibzada Muhammad
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Performance Analysis of Selected Cooperative Relaying Techniques2010Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    Recently, cooperative communication has gained significant interest due to the fact that it exploits spatial diversity and provides capacity/performance gain over conventional single- input single-output (SISO) systems. A mobile node with single antenna can cooperate with a nearby mobile node having single antenna in multi-user environment to create the effect of virtual multiple antenna system. Hence, reducing the complexity associated with actual multiple antenna systems. Despite the small size and power constraints, a mobile node can still benefit from spatial diversity by employing cooperation, thus saving transmission power and increasing the coverage range of the network. In this thesis, we have selected some of relaying protocols, namely, amplify-and-forward, decode-and-forward, detect-and-forward, and selective detect-and-forward that are studied and implemented for two different relaying geometries, i.e. equidistant and collinear. Results are studied and compared with each other to show the performance of each protocol in terms of average symbol error probabilities. The considered system model has three nodes, i.e. source, relay, destination. Communicating nodes are considered to be half-duplex with single antenna for transmission and reception. The source, when communicating with the destination, broadcasts the information, which is heard by the nearby relay. The relay then uses one of the cooperation protocols. Finally, the relayed signal reaches the destination, where it is detected by maximal ratio combiner (MRC) and combined with the direct transmission for possible diversity gains. The transmission path or the channel is modeled as a frequency non-selective Rayleigh fading in the presence additive white Gaussian noise (AWGN). The effect of path loss has been observed on cooperation for collinear arrangement with exponential decay up to four. Considering equidistant arrangement, decode-and-forward shows good performance at high signal-to-noise ratio (SNR) while amplify-and-forward is very promising for very low SNR. A selective relaying scheme called selective detect-and- forward is also presented which outperforms its fixed counterparts for a wide range of SNR.

  • 50.
    Aftab, Adnan
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Mufti, Muhammad Nabeel
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Spectrum sensing through implementation of USRP22011Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    Scarcity of the wireless spectrum has led to the development of new techniques for better utilization of the wireless spectrum. Demand for high data rates and better voice quality is resulting in the development of new wireless standard making wireless spectrum limited than ever. In this era of wireless communication, service providers and telecom operators are faced with a dilemma where they need a large sum of the wireless spectrum to meet the ever increasing quality of service requirements of consumers. This has led to the development of spectrum sensing techniques to find the unused spectrum in the available frequency band. The results presented in this thesis will help out in developing clear understanding of spectrum sensing techniques. Comparison of different spectrum sensing approaches. The experiments carried out using USRP2 and GNU radio will help the reader to understand the concept of underutilized frequency band and its importance in Cognitive Radios.

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