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  • 101.
    Akbarnejad, Shahin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Kennedy, M. W.
    Fritzsch, R.
    Aune, R. E.
    An investigation on permeability of ceramic foam filters (CFF)2015Inngår i: TMS Light Metals, 2015, s. 949-954Konferansepaper (Fagfellevurdert)
    Abstract [en]

    CFFs are used to filter liquid metal in the aluminum industry. CFFs are classified in grades or pores per inch (PPI), ranging from 10-100 PPI. Their properties vary in everything from pore and strut size to window size. CFFs of 80-100 PPI are generally not practical for use by industry, as priming of the filters by gravitational forces requires an excessive metal head. Recently, co-authors have invented a method to prime such filters using electromagnetic Lorentz forces, thus allowing filters to be primed with a low metal head. In the continuation of this research work, an improved experimental setup was developed in the present study to validate previous results and to measure the permeability of different filters, as well as a stack of filters. The study of permeability facilitates estimation of the required pressure drop to prime the filters and the head required to generate a given casting rate.

  • 102.
    Akhlaghpasand, Hossein
    et al.
    Iran Univ Sci and Technol, Iran.
    Razavizadeh, S. Mohammad
    Iran Univ Sci and Technol, Iran.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Do, Tan Tai
    Ericsson AB, Sweden.
    Jamming Detection in Massive MIMO Systems2018Inngår i: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 7, nr 2, s. 242-245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This letter considers the physical layer security of a pilot-based massive multiple-input multiple-output (MaMIMO) system in presence of a multi-antenna jammer. We propose a new jamming detection method that makes use of a generalized likelihood ratio tes

  • 103.
    Akhter, Habiba
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Apodization Method in UWB SAR Imaging2014Inngår i: 2014 1ST INTERNATIONAL CONFERENCE ON ELECTRICAL ENGINEERING AND INFORMATION & COMMUNICATION TECHNOLOGY (ICEEICT 2014), IEEE Computer Society Digital Library, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Synthetic Aperture Radar (SAR) image processing involves a two dimensional (2-D) Fourier Transform (FT) and the spectrum shape introduces high intensity sidelobes. These sidelobes may severely distort the image. Apodization technique can decrease the sidelobes level while preserving the image resolution. However, in Ultra wideband (UWB) SAR imaging, we have to reduce both orthogonal and non-orthogonal sidelobes. In this paper, a new linear window function has been presented based on analysis of different linear and non-linear apodization techniques. This new linear method controls both orthogonal and non-orthogonal sidelobes better than other conventional window functions. This method has been applied and verified with a real SAR image.

  • 104.
    Akhter, Habiba
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Evaluation of weighting functions for Sidelobe control in UWB SAR image processing2013Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    Ultra wideband (UWB) Synthetic Aperture Radar (SAR) holds huge possibilities for both terrestrial and celestial object sensing with excellent details which assists in science and technology. SAR systems associated with large antenna beamwidth, large signal bandwidth and low frequency operating in the VHF/UHF region is becoming gradually more popular because of their rising number of application in the areas of ground-penetrating radar (GPR) and foliage penetration radar (FOPEN). Apodization techniques in UWB SAR imaging have attracted significant interest in recent years for sidelobe suppression in SAR images. This technique is split into two groups: linear apodization and non-linear apodization. Linear apodization technique means to apply amplitude weighting functions in frequency domain prior to the final inverse Fourier transform requisite to appropriately focus on the SAR images. Both linear and non linear techniques can be used to suppress sidelobes level. Frequently used linear weighting functions are Hanning, Hamming and Blackman. Linear techniques can control the sidelobes level but image resolution reduces simultaneously. But non-linear techniques like Spatially Variant Apodization (SVA), Complex Duel Apodization and Dual-Apodization can suppress sidelobes and preserve the spatial resolution concurrently. However for these methods, it can be hard to understand how the output signal relates to input signal and also the phase information of image is lost. In this thesis paper, the main focus is, on apodization techniques to propose a new weighting function for sidelobe apodization and investigate it on real SAR images. In this thesis, we also study Impulse response (IPR) function for UWB SAR image processing. A two dimensional sinc function is used as an impulse response function for narrow band (NB) SAR system. This function can be obtained from a two dimensional Fourier Transform of a SAR image. This rectangular estimation is reasonable for narrow band and narrowbeam SAR. But for large bandwidth and wide integration angles, this approximation for the UWB SAR spectrum is not valid. It can provide erroneous SAR image quality measurements. To obtain precise image quality measurement, SAR image need to be generated for a range of different integration angle as UWB SAR systems are related with large integration angle to maintain azimuth focusing. So, in this work the choices of optimum windows have been investigated at different integration angles in order to see if there are large differences between NB SAR Apodization and UWB SAR Apodization.

  • 105.
    Akif, Ahmed
    Linköpings universitet, Institutionen för systemteknik, Datorteknik.
    FIR Filter Features on FPGA2018Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    Finite-length impulse response (FIR) filters are one of the most commonly used digital signal processing algorithms used nowadays where a FPGA is the device used to implement it. The continued development of the FPGA device through the insertion of dedicated blocks raised the need to study the advantages offered by different FPGA families. The work presented in this thesis study the special features offered by FPGAs for FIR filters and introduce a cost model of resource utilization. The used method consist of several stages including reading, classification of features and generating coefficients. The results show that FPGAs have common features but also specific differences in features as well as resource utilization. It has been shown that there is misconception when dealing with FPGAs when it comes to FIR filter as compared to ASICs.

  • 106.
    Akinwande, Gbenga Segun
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Signaling Over Protocols Gateways in Next-Generation Networks2009Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    In this thesis, I examined various signalling both in wired and mobile networks, with more emphasis on SIGTRAN. The SIGTRAN is the protocol suite applicable in the current new generation and next-generation networks, most especially as it enables service provider to be able to interpolate both wireline and wireless services within the same architecture. This concept is an important component in today’s Triple-play communication, and hence this thesis has provided a broad view on Signalling and Protocol Gateways in Traditional and Next Generations Networks. Signal flow in a typical new generation network was examined by carrying out discrete event simulation of UMTS network using OPNET modeller 14.5. Through both Packet-Switching (PS) and Circuit-Switching (CS) signalling, I was able to examine the QoS on a UMTS. Precisely, I looked at throughput on UMTS network by implementing WFQ and MDRR scheduling schemes.

  • 107. Al Ismaeil, K.
    et al.
    Aouada, D.
    Mirbach, B.
    Ottersten, Björn
    Interdisciplinary Centre for Security, Reliability and Trust, Universtity of Luxembourg, Luxembourg.
    Depth super-resolution by enhanced shift and add2013Inngår i: Computer Analysis of Images and Patterns: 15th International Conference, CAIP 2013, York, UK, August 27-29, 2013, Proceedings, Part II, Springer, 2013, Vol. 8048 LNCS, nr PART 2, s. 100-107Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We use multi-frame super-resolution, specifically, Shift & Add, to increase the resolution of depth data. In order to be able to deploy such a framework in practice, without requiring a very high number of observed low resolution frames, we improve the initial estimation of the high resolution frame. To that end, we propose a new data model that leads to a median estimation from densely upsampled low resolution frames. We show that this new formulation solves the problem of undefined pixels and further allows to improve the performance of pyramidal motion estimation in the context of super-resolution without additional computational cost. As a consequence, it increases the motion diversity within a small number of observed frames, making the enhancement of depth data more practical. Quantitative experiments run on the Middlebury dataset show that our method outperforms state-of-the-art techniques in terms of accuracy and robustness to the number of frames and to the noise level.

  • 108. Al Ismaeil, K.
    et al.
    Aouada, D.
    Mirbach, B.
    Ottersten, Björn
    Advanced Engineering - IEE S.A., Luxembourg .
    Dynamic super resolution of depth sequences with non-rigid motions2013Inngår i: 2013 IEEE International Conference on Image Processing, ICIP 2013 - Proceedings, IEEE Signal Processing Society, 2013, s. 660-664Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We enhance the resolution of depth videos acquired with low resolution time-of-flight cameras. To that end, we propose a new dedicated dynamic super-resolution that is capable to accurately super-resolve a depth sequence containing one or multiple moving objects without strong constraints on their shape or motion, thus clearly outperforming any existing super-resolution techniques that perform poorly on depth data and are either restricted to global motions or not precise because of an implicit estimation of motion. The proposed approach is based on a new data model that leads to a robust registration of all depth frames after a dense upsampling. The textureless nature of depth images allows to robustly handle sequences with multiple moving objects as confirmed by our experiments.

  • 109. Al Ismaeil, K.
    et al.
    Aouada, D.
    Mirbach, B.
    Ottersten, Björn
    SnT - Universtity of Luxembourg, Luxembourg .
    Multi-frame super-resolution by enhanced shift & add2013Inngår i: 2013 8th International Symposium on Image and Signal Processing and Analysis (ISPA), IEEE , 2013, s. 171-176Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A critical step in multi-frame super-resolution is the registration of frames based on their motion. We improve the performance of current state-of-the-art super-resolution techniques by proposing a more robust and accurate registration as early as in the initialization stage of the high resolution estimate. Indeed, we solve the limitations on scale and motion inherent to the classical Shift & Add approach by upsampling the low resolution frames up to the super-resolution factor prior to estimating motion or to median filtering. This is followed by an appropriate selective optimization, leading to an enhanced Shift & Add. Quantitative and qualitative evaluations have been conducted at two levels; the initial estimation and the final optimized superresolution. Results show that the proposed algorithm outperforms existing state-of-art methods.

  • 110. Al Ismaeil, Kassem
    et al.
    Aouada, Djamila
    Mirbach, Bruno
    Ottersten, Björn
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Bilateral Filter Evaluation Based on Exponential Kernels2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The well-known bilateral filter is used to smooth noisy images while keeping their edges. This filter is commonly used with Gaussian kernel functions without real justification. The choice of the kernel functions has a major effect on the filter behavior. We propose to use exponential kernels with L1 distances instead of Gaussian ones. We derive Stein's Unbiased Risk Estimate to find the optimal parameters of the new filter and compare its performance with the conventional one. We show that this new choice of the kernels has a comparable smoothing effect but with sharper edges due to the faster, smoothly decaying kernels.

  • 111.
    Alam, Assad
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Asplund, Fredrik
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Mekatronik.
    Behere, Sagar
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Mekatronik.
    Björk, Mattias
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Mekatronik.
    Garcia Alonso, Liliana
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Mekatronik.
    Khaksari, Farzad
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Khan, Altamash
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Kjellberg, Joakim
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Liang, Kuo-Yun
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Lyberger, Rickard
    Scania CV AB.
    Mårtensson, Jonas
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Nilsson, John-Olof
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Pettersson, Henrik
    Scania CV AB.
    Pettersson, Simon
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Mekatronik.
    Stålklinga, Elin
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Sundman, Dennis
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Zachariah, Dave
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Cooperative driving according to Scoop2011Rapport (Annet vitenskapelig)
    Abstract [en]

    KTH Royal Institute of Technology and Scania are entering the GCDC 2011 under the name Scoop –Stockholm Cooperative Driving. This paper is an introduction to their team and to the technical approach theyare using in their prototype system for GCDC 2011.

  • 112.
    Alam, Md. Jobayer
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Sujan, Shaha Mohammed Goni Abed
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Low Complexity Channel Estimation for OFDM Systems Based on LS and MMSE Estimators’2010Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    In this paper we investigate the block-type pilot channel estimation for orthogonal frequency-division multiplexing (OFDM) systems. The estimation is based on the minimum mean square error (MMSE) estimator and the least square (LS) estimator. We derive the MMSE and LS estimators’ architecture and investigate their performances. We prove that the MMSE estimator performance is better but computational complexity is high, contrary the LS estimator has low complexity but poor performance. For reducing complexity we proposed two different solutions which are the Simplified Least Square (SLS) estimator and the modified MMSE estimator. We evaluate estimator’s performance on basis of mean square error and symbol error rate for 16 QAM systems. We also evaluate estimator’s computational complexity.

  • 113.
    ALAM, MD. SHAMSER
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    On sphere detection for OFDM based MIMO systems2010Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    The mobile wireless communication systems has been growing fast and continuously over the past two decades. Therefore, in order to fulfill the demand for this rapid growth, the standardization bodies along with wireless researchers and mobile operators around the world have been constantly working on new technical specifications.An important problem in modern communication is known as NP complete problem in the Maximum Likelihood (ML) detection of signals transmitting over Multiple Input Multiple Output channel of the OFDM transceiver system. Development of the Sphere Decoder (SD) as a result of the rapid advancement in signal processing techniques provides ML detection for MIMO channels at polynomial time complexity average case. There are weaknesses in the existing SDs. The sphere decoder performance is very sensitive for the most current proposals in order to choose the search radius parameter. At high spectral efficiencies SNR is low or as the problem dimension is high and the complexity coefficient can become very large too. Digital communications of detecting a vector of symbols has importance as, is encountered in several different applications. These symbols are as the finite alphabet and transmitted over a multiple-input multiple-output (MIMO) channel with Gaussian noise. There are no limitation to the detection of symbols spatially multiplexed over a multiple-antenna channel and the multi user detection problem. Efficient algorithms are considered for the detection problems and have recognized well. The algorithm of sphere decoder, orders has optimal performance considering the error probability and this has proved extremely efficient in terms of computational complexity for moderately sized problems in case of signal to noise ratio. At high SNR the algorithm has a polynomial average complexity and it is understood the algorithm has an exponential worst case complexity. The efficiency of the algorithm is ordered the exponential rate derivation of growth. Complexity is positive for the finite SNR and small in the high SNR. To achieve the sphere decoding solution applying Schnorr-Euchner by Maximum likelihood method , Depth-first Stack-based Sequential decoding is used. This thesis focuses on the receiver part of the transceiver system and takes a good look at the near optimal algorithm for sphere detection of a vector of symbols transmitted over MIMO channel. The analysis and algorithms are general in nature.

  • 114.
    Alam, Syed Asad
    et al.
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Oscar
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Design of Finite Word Length Linear-Phase FIR Filters inthe Logarithmic Number System Domain2014Inngår i: VLSI design (Print), ISSN 1065-514X, E-ISSN 1563-5171, Vol. 2014, nr 217495Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Logarithmic number system (LNS) is an attractive alternative to realize finite-length impulse response filters because ofmultiplication in the linear domain being only addition in the logarithmic domain. In the literature, linear coefficients are directlyreplaced by the logarithmic equivalent. In this paper, an approach to directly optimize the finite word length coefficients in theLNS domain is proposed. This branch and bound algorithm is implemented based on LNS integers and several different branchingstrategies are proposed and evaluated. Optimal coefficients in the minimax sense are obtained and compared with the traditionalfinite word length representation in the linear domain as well as using rounding. Results show that the proposed method naturallyprovides smaller approximation error compared to rounding. Furthermore, they provide insights into finite word length propertiesof FIR filters coefficients in the LNS domain and show that LNS FIR filters typically provide a better approximation error comparedto a standard FIR filter.

  • 115.
    Alam, Syed Asad
    et al.
    Linköpings universitet, Institutionen för systemteknik, Datorteknik. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, Oscar
    Linköpings universitet, Institutionen för systemteknik, Datorteknik. Linköpings universitet, Tekniska fakulteten.
    Generalized Division-Free Architecture and Compact Memory Structure for Resampling in Particle Filters2015Inngår i: 2015 European Conference on Circuit Theory and Design (ECCTD), IEEE Press, 2015, s. 416-419Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The most challenging step of implementing particle filtering is the resampling step which replicates particles with large weights and discards those with small weights. In this paper, we propose a generic architecture for resampling which uses double multipliers to avoid normalization divisions and make the architecture  equally efficient for non-powers-of-two number of particles. Furthermore, the complexity of resampling is greatly affected by the size of memories used to store weights. We illustrate that by storing the original weights instead of their cumulative sum and calculating them online reduces the total complexity, in terms of area, ranging from 21% to 45%, while giving up to 50% reduction in memory usage.

  • 116.
    Alam, Syed Asad
    et al.
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Oscar
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Implementation of Narrow-Band Frequency-Response Masking for Efficient Narrow Transition Band FIR Filters on FPGAs2011Inngår i: NORCHIP, 2011, IEEE conference proceedings, 2011, s. 1-4Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The complexity of narrow transition band FIR filters is highand can be reduced by using frequency response masking (FRM) techniques. Thesetechniques use a combination of periodic model filters and masking filters. Inthis paper, we show that time-multiplexed FRM filters achieve lowercomplexity, not only in terms of multipliers, but also logic elements compared to time-multiplexed singlestage filters. The reduced complexity also leads to a lower power consumption. Furthermore, we show that theoptimal period of the model filter is dependent on the time-multiplexing factor.

  • 117.
    Alam, Tahmid
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Irshad, Sharmeen
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    SW features in power systems for telecom equipment2013Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    This thesis report is a research effort with Ericsson’s devices and internal documents. In essence this thesis report contributes with a perspective to understand the power system of Radio Base Station and its features. The overall research aim is to understand the existing power system and its features and to propose new software and hardware features. A lot of investigations have been done with the Functional Specification and Requirement Specification documents for analysis of the present features. The main goal is to identify software features and their benefits to customer. After analysing the present features new features were proposed. For the proposal many steps were taken into consideration including cost and system information. Also some hardware changes have been required. With the new proposed features, the power system will perform better with different environments and also some of the proposals were improvements of the existing features. The proposed features are mostly focused on power saving and cost to benefit the customer.

  • 118.
    Al-Askary, Omar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Coding and Iterative Decoding of Concentrated Multi-level Codes for the Rayleigh Fading Channel2006Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    In this thesis we present the concept of concatenated multilevel codes. These codes are a combination of generalized concatenated codes with multilevel coding. The structure of these codes is simple and relies on the concatenation of two or more codes of shorter length. These codes can be designed to have large diversity which makes them attractive for use in fading channels. We also present an iterative decoding algorithm taylored to fit the properties of the proposed codes. The iterative decoding algorithm we present has a complexity comparable to the complexity of GMD decoding of the same codes. However, The gain obtained by using the iterative decoder as compared to GMD decdoing of these codes is quite high for Rayleigh fading channels at bit error rates of interest. Some bounds on the performance of these codes are given in this thesis. Some of the bounds are information theoretic bounds which can be used regardless of the code under study. Other bounds are on the error probability of concatenated multilevel codes.

    Finally we give examples on the implementation of these codes in adaptive coding of OFDM channels and MIMO channels.

  • 119.
    Alavanja, Bojan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Application of SCADA Data Monitoring Methodology and Reliability Analysis of Wind Farm Operational Data2016Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    Reliability of wind turbine components and maintenance optimisation are among the critical aspects of wind power development closely related to profitability and future development. The main reason for research in these areas is lowering the cost of energy production for wind power, specifically important in offshore environment. Continuous monitoring of specific wind turbine components can be valuable for wind farm operators and, subsequently, wind farm owners.  Also, health assessment of critical components can be useful in estimating the possibilities for life extension of wind turbines. Expensive Condition Monitoring Systems (CMSs) are not always available, particularly in older wind farms, and additionally installing CMSs on wind turbines is not always economically feasible. However, most of modern wind turbines are equipped with the Supervisory Control And Data Acquisition (SCADA) system which is recording 10-minute average values of parameters that depict operation of the turbine. That being said, SCADA data contains a vast amount of information that can be used for analysis of wind turbine components health. Therefore, this project will present an application of previously published methodology for SCADA data condition monitoring on real wind farm data. The goal of this project is to investigate on the possibilities of the SCADA monitoring methodology and what can be the added value of the application for wind farm operators, owners and other stakeholders.

    The methodology for condition monitoring through SCADA data was applied on real data gathered from two wind farms in Germany and one in the Netherlands. During the project the methodology had to be modified in order to ensure the best possible industrial application. Results of the project showed that the SCADA data condition monitoring approach is not capable of predicting failures. However, the technique has been proven successful for detecting the changes of trends in dependencies of working parameters, specifically monitoring parameters related to the turbine generators. Continuously monitoring the dependencies of working parameters can be used as an additional source of information for maintenance scheduling and assessment of components health. The approach presented in this paper can be valuable to asset managers and wind farm owners.

  • 120. Alaves, Dimas
    et al.
    Machado, Renato
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    da Costa, Daniel Benevides
    Legg, Andrei Piccinini
    Uchoa-Filho, Bartolomeu F.
    A dynamic hybrid antenna/relay selection scheme for the multiple-access relay channel2014Inngår i: 2014 11TH INTERNATIONAL SYMPOSIUM ON WIRELESS COMMUNICATIONS SYSTEMS (ISWCS), IEEE , 2014, s. 594-599Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a dynamic hybrid antenna/relay selection scheme for multiple-access relay systems. The proposed scheme aims to boost the system throughput while keeping a good error performance. By using the channel state information, the destination node performs a dynamic selection between the signals provided by the multi-antenna relay, located in the inter-cell region, and the relay nodes geographically distributed over the cells. The multi-antenna relay and the single-antenna relay nodes employ the decode-remodulate-and-forward and amplify-and-forward protocols, respectively. Results reveal that the proposed scheme offers a good tradeoff between spectral efficiency and diversity gain, which is one of the main requirements for the next generation of wireless communications systems.

  • 121.
    Albinsson, John
    et al.
    Lund Univ, Dept Biomed Engn, S-22100 Lund, Sweden..
    Brorsson, Sofia
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, Rydberglaboratoriet för tillämpad naturvetenskap (RLAS).
    Rydén Ahlgren, Åsa
    Lund Univ, Dept Clin Sci, Clin Physiol & Nucl Med Unit, Malmo, Sweden..
    Cinthio, Magnus
    Lund Univ, Dept Biomed Engn, S-22100 Lund, Sweden..
    Improved tracking performance of lagrangian block-matching methodologies using block expansion in the time domain: In silico, phantom and invivo evaluations2014Inngår i: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 40, nr 10, s. 2508-2520Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study was to evaluate tracking performance when an extra reference block is added to a basic block-matching method, where the two reference blocks originate from two consecutive ultrasound frames. The use of an extra reference block was evaluated for two putative benefits: (i) an increase in tracking performance while maintaining the size of the reference blocks, evaluated using in silico and phantom cine loops; (ii) a reduction in the size of the reference blocks while maintaining the tracking performance, evaluated using in vivo cine loops of the common carotid artery where the longitudinal movement of the wall was estimated. The results indicated that tracking accuracy improved (mean - 48%, p<0.005 [in silico]; mean - 43%, p<0.01 [phantom]), and there was a reduction in size of the reference blocks while maintaining tracking performance (mean - 19%, p<0.01 [in vivo]). This novel method will facilitate further exploration of the longitudinal movement of the arterial wall. (C) 2014 World Federation for Ultrasound in Medicine & Biology.

  • 122.
    Aldalaty, Khalid
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Mobile IP handover delay reduction using seamless handover architecture2009Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    Seamless communication is becoming the main aspect for the next generation of the mobile and wireless networks. Roaming among multiple wireless access networks connected together through one IP core makes the mobility support for the internet is very critical and more important research topics nowadays. Mobile IP is one of the most successful solutions for the mobility support in the IP based networks, but it has poor performance in term of handover delay. Many improvements have been done to reduce the handover delay, which result in two new standards: the Hierarchical MIP (HMIP) and the Fast MIP (FMIP), but the delay still does not match the seamless handover requirements. Finally Seamless MIP (S-MIP) has been suggested by many work groups, which combine between an intelligent handover algorithm and a movement tracking scheme. In This thesis, we show the handover delay reduction approaches, specifically the Seamless Mobile IP. The thesis studies the effects of the S-MIP in the handover delay and the network performance as well. A simulation study takes place to compare between the standard MIP and the new suggested S-MIP protocol in term of handover delay, packet loss and bandwidth requirement. The thesis concludes with the analyzing of the simulation results, evaluating the S-MIP performance and finally gives some suggestions for the future work.

  • 123.
    Aldayel, Omar
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. King Saud University, Saudi Arabia.
    Bengtsson, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Alshebeili, Saleh A.
    King Saud University, Saudi Arabia.
    Evaluation of MIMO channel non-stationarity2013Inngår i: 2013 Proceedings of the 21st European Signal Processing Conference (EUSIPCO), IEEE , 2013, s. 6811769-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Several MIMO processing algorithms have been proposed that exploit long-term channel statistics, relaying on the critical assumption that this long-term information is valid long enough. In this paper, we consider the Correlation Matrix Distance (CMD) method previously proposed for the evaluation of MIMO channel non-stationarity. We highlight a couple of problems with the CMD measure and propose two new metrics that are more appropriate for non-stationarity evaluation. The performance of the CMD method and new correlation matrix distance metrics is investigated using measured 4×4 MIMO channels. Both Line-of-Sight (LOS) and Non-LOS (NLOS) environments are considered.

  • 124.
    Alenlöv, Johan
    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.
    Olsson, Jimmy
    Particle-based adaptive-lag online marginal smoothing in general state-space models2019Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 67, nr 21, s. 5571-5582Artikkel i tidsskrift (Fagfellevurdert)
  • 125.
    Aleti, Mahesh
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Syed, Rahamatulla
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Chennupati, Rajendra Prasad
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Fuzzy Based power control system Using ANFIS and MIMO-OFDM Techniques in Cognitive Radio Networks2014Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    Cognitive Radio technology is used for efficient utilization of the spectrum. There are two types of users, one is the Primary user (PU), and the second one is the Secondary user (SU). In those users, PU is having the license to use the spectrum. The SU does not have the license to use the spectrum. Cognitive Radio comprises of Spectrum sensing, Spectrum Management and Spectrum Mobility. In cognitive radio, optimal power control in spectrum sharing is main research issues. In the spectrum, sharing both PU and SU can access the spectrum simultaneously as long as there is no interference to PU’s of Quality of service (QOS). So we have to handle this interference to the PU and we have to improve the performance of the SU. For that power control is the main consternate to improve the performance of SU. In our thesis, we are divided into two parts, the first one is we used ANFIS (Adaptive Neuro Fuzzy Inference System) for optimizing power control in cognitive radio network Users (SU) by optimization of SNR & SINR at Primary User (PU) to maintain QOS of PU and improve the performance of SU and Channel capacity computation for various ISR tolerance levels at PU. In second part, we used implementation of MIMO (Multiple Input Multiple output)-OFDM (Orthogonal Frequency Division Multiplexing) transmission technique in CRN (Cognitive Radio networks) for it is use in emergency conditions where transmission requires reliability and high data rate. Then it is tested BER (Bit error rate) performance on MATLAB. Key words: Cognitive Radio, Power Control, the Fuzzy Interference System (FIS), ANFIS, “MIMO” (“Multiple Input Multiple Output”), “OFDM” (“Orthogonal Frequency Division Multiplexing”), AWGN, BER, SNR, Eb/N0

  • 126.
    Alfredsson, Stefan
    et al.
    Karlstad universitet.
    Brunström, Anna
    Karlstad universitet.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Impact of 4G wireless link configurations on VoIP network performance2008Inngår i: IEEE International Symposium on Wireless Communication Systems 2008, ISWCS2008, Reykjavik, Iceland, 2008Konferansepaper (Fagfellevurdert)
  • 127.
    Algers, Björn
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Stereo Camera Calibration Accuracy in Real-time Car Angles Estimation for Vision Driver Assistance and Autonomous Driving2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The automotive safety company Veoneer are producers of high end driver visual assistance systems, but the knowledge about the absolute accuracy of their dynamic calibration algorithms that estimate the vehicle’s orientation is limited.

    In this thesis, a novel measurement system is proposed to be used in gathering reference data of a vehicle’s orientation as it is in motion, more specifically the pitch and roll angle of the vehicle. Focus has been to estimate how the uncertainty of the measurement system is affected by errors introduced during its construction, and to evaluate its potential in being a viable tool in gathering reference data for algorithm performance evaluation.

    The system consisted of three laser distance sensors mounted on the body of the vehicle, and a range of data acquisition sequences with different perturbations were performed by driving along a stretch of road in Linköping with weights loaded in the vehicle. The reference data were compared to camera system data where the bias of the calculated angles were estimated, along with the dynamic behaviour of the camera system algorithms. The experimental results showed that the accuracy of the system exceeded 0.1 degrees for both pitch and roll, but no conclusions about the bias of the algorithms could be drawn as there were systematic errors present in the measurements.

  • 128.
    Al-Ghazu, Nader
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    A Study of the Next WLAN Standard IEEE 802.11ac Physical Layer2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis studies the Physical Layer (PHY) of the new IEEE 802.11acWireless Local Access Network (WLAN) standard. The 11ac is built basedon the 11n successful standard. The standard is expected to be completedby the end of 2013. And it promises a Very High Throughput (VHT),and robust communication. In order to achieve that, the 11ac uses morebandwidth, it employs higher numbers of Multiple-Input Multiple-Output(MIMO) spatial streams, and higher orders of modulations. The 11ac PHYframe structure is studied in details. The transmitter and receiver blocks areexplained and implemented by MATLAB. Bit Error Rate (BER) and ErrorVector Magnitude (EVM) simulations of the PHY were run. The effectof different Modulation and Coding Scheme (MCS), and bandwidths werestudied. The performance of MIMO and Space-Time Block Coding (STBC)was investigated. The simulation results shows how the 11ac benefits fromthe new employed features. The created MATLAB simulation program canbe used for further tests and research.

  • 129.
    Alhasan, Raghda
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Software defined radio2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Software Defined Radio (SDR) technology is used to receive and transmit radio signals. Radio signals can be received using the SDR_sharp software that can be downloaded to a personal computer and combined with the RTL-SDR dongle hardware that is connected to the computer. This report gives a brief explanation of the SDR receiver, the supported software, and some applications that can be implemented with SDR. Moreover, it is shown how to install the SDR_sharp software and the hardware Zadig. After installation, wideband FM (WFM) reception and adjustment of RF gain and frequency error is illustrated. The reception of some national, regional and community/commercial stations that can be received in Växjö Sweden is presented.

    Keyword: Software defined radio, FM radio.

  • 130. Ali Khan, N.
    et al.
    Ali, S.
    Jansson, Magnus
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Direction of arrival estimation using adaptive directional time-frequency distributions2018Inngår i: Multidimensional systems and signal processing, ISSN 0923-6082, E-ISSN 1573-0824, Vol. 29, nr 2, s. 503-521Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Time-frequency distributions (TFDs) allow direction of arrival (DOA) estimation algorithms to be used in scenarios when the total number of sources are more than the number of sensors. The performance of such time-frequency (t-f) based DOA estimation algorithms depends on the resolution of the underlying TFD as a higher resolution TFD leads to better separation of sources in the t-f domain. This paper presents a novel DOA estimation algorithm that uses the adaptive directional t-f distribution (ADTFD) for the analysis of close signal components. The ADTFD optimizes the direction of kernel at each point in the t-f domain to obtain a clear t-f representation, which is then exploited for DOA estimation. Moreover, the proposed methodology can also be applied for DOA estimation of sparse signals. Experimental results indicate that the proposed DOA algorithm based on the ADTFD outperforms other fixed and adaptive kernel based DOA algorithms.

  • 131.
    Ali, Mohsin
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Nasir, Muhammad Jamal
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Echo Cancellation using PMSAF and Compare the performance with NLMS and improved PNLMS under different Impulse responses2013Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    In the field of signal processing adaptive filtering is a major subject which has vast applications in speech processing e.g. speech coding, speech enhancement, echo cancellation and interference. Echo is the major problem in the communication systems. There are two major types of echoes hybrid and acoustic echoes. In order to remove these echoes the most important method for removing these echoes is through cancellation. Adaptive filters are used to estimate the replication of echoes and then subtracted from the infected signal. . We introduced subband filters to improve the performance of adaptive filter (time domain). Due to small adaptive filters in the subband filter banks, we can improve the reduction of complexity, computational and convergence level as compared with others. The major goal of this thesis is to present the echo cancellation using the multiband subband adaptive filtering and also compare the performance with NLMS and Improved PNLMS using different impulse responses. PMSAF algorithm behaves continuously better convergense rate with excitation signal (colored noise and speech signal) for both impulse responses (sparse and dispersive) as compared with IPNLMS and NLMS algorithms.

  • 132.
    Ali, Sadiq
    et al.
    Electrical Engineering, University of Engineering and Technology of Peshawar, Pakistan.
    Jansson, Magnus
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Seco-Granados, Gonzalo
    Telecommunications and Systems Engineering, Universitat Autònoma de Barcelona, Spain.
    Lopez-Salcedo, Jose A.
    Universitat Autònoma de Barcelona, Spain.
    Kronecker-Based Fusion Rule for Cooperative Spectrum Sensing with Multi-Antenna Receivers2014Inngår i: Electronics, ISSN 2079-9292, Vol. 3, nr 4, s. 675-688Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper considers a novel fusion rule for spectrum sensing scheme for a cognitive radio network with multi-antenna receivers. The proposed scheme exploits the fact that when any primary signal is present, measurements are spatially correlated due to presence of inter-antenna and inter-receiver spatial correlation. In order to exploit this spatial structure, the generalized likelihood ratio test (GLRT) operates with the determinant of the sample covariance matrix. Therefore, it depends on the sample size N and the dimensionality of the received data (i.e., the number of receivers K and antennas L). However, when the dimensionality fK; Lg is on the order, or larger than the sample size N, the GLRT degenerates due to the ill-conditioning of the sample covariance matrix. In order to circumvent this issue, we propose two techniques that exploit the inner spatial structure of the received observations by using single pair and multi-pairs Kronecker products. The performance of the proposed detectors is evaluated by means of numerical simulations, showing important advantages with respect to the traditional (i.e., unstructured) GLRT approach.

  • 133.
    Ali, Sadiq
    et al.
    Universitat Autònoma de Barcelona (UAB),.
    Jansson, Magnus
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Seco-Granados, Gonzalo
    Universitat Autònoma de Barcelona (UAB),.
    López-Salzedo, José A.
    Universitat Autònoma de Barcelona (UAB),.
    Novel collaborative spectrum sensing based on spatial covariance structure2013Inngår i: 2013 Proceedings of the 21st European Signal Processing Conference (EUSIPCO), 2013, s. 6811678-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In collaborative spectrum sensing, spatial correlation in the measurements obtained by sensors can be exploited by adopting Generalized Likelihood Ratio Test (GLRT). In this process the GLRT provides a test statistics that is normally based on the sample covariance matrix of the received signal samples. Unfortunately, problems arise when the dimensions of this matrix become excessively large, as it happens in the so-called large-scale wireless sensor networks. In these circumstances, a huge amount of samples are needed in order to avoid the ill-conditioning of the GLRT, which degenerates when the dimensionality of data is equal to the sample size or larger. To circumvent this problem, we modify the traditional GLRT detector by decomposing the large spatial covariance matrix into small covariance matrices by using properties of the Kronecker Product. The proposed detection scheme is robust in the case of high dimensionality and small sample size. Numerical results are drawn, which show that the proposed detection schemes indeed outperform the traditional approaches when the dimension of data is larger than the sample size.

  • 134.
    Ali, Sajjad
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Ali, Asad
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Performance Analysis of AODV, DSR and OLSR in MANET2010Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    A mobile ad hoc network (MANET) consists of mobile wireless nodes. The communication between these mobile nodes is carried out without any centralized control. MANET is a self organized and self configurable network where the mobile nodes move arbitrarily. The mobile nodes can receive and forward packets as a router. Routing is a critical issue in MANET and hence the focus of this thesis along with the performance analysis of routing protocols. We compared three routing protocols i.e. AODV, DSR and OLSR. Our simulation tool will be OPNET modeler. The performance of these routing protocols is analyzed by three metrics: delay, network load and throughput. All the three routing protocols are explained in a deep way with metrics. The comparison analysis will be carrying out about these protocols and in the last the conclusion will be presented, that which routing protocol is the best one for mobile ad hoc networks.

  • 135.
    Alickovic, Emina
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Subasi, Abdulhamit
    Effat Univ, Saudi Arabia.
    Ensemble SVM Method for Automatic Sleep Stage Classification2018Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 67, nr 6, s. 1258-1265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sleep scoring is used as a diagnostic technique in the diagnosis and treatment of sleep disorders. Automated sleep scoring is crucial, since the large volume of data should be analyzed visually by the sleep specialists which is burdensome, time-consuming tedious, subjective, and error prone. Therefore, automated sleep stage classification is a crucial step in sleep research and sleep disorder diagnosis. In this paper, a robust system, consisting of three modules, is proposed for automated classification of sleep stages from the single-channel electroencephalogram (EEG). In the first module, signals taken from Pz-Oz electrode were denoised using multiscale principal component analysis. In the second module, the most informative features are extracted using discrete wavelet transform (DWT), and then, statistical values of DWT subbands are calculated. In the third module, extracted features were fed into an ensemble classifier, which can be called as rotational support vector machine (RotSVM). The proposed classifier combines advantages of the principal component analysis and SVM to improve classification performances of the traditional SVM. The sensitivity and accuracy values across all subjects were 84.46% and 91.1%, respectively, for the five-stage sleep classification with Cohens kappa coefficient of 0.88. Obtained classification performance results indicate that, it is possible to have an efficient sleep monitoring system with a single-channel EEG, and can be used effectively in medical and home-care applications.

  • 136.
    Alizadeh, Mahmoud
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik. KTH, Teknisk informationsvetenskap.
    Characterisation, Modelling and Digital Pre-Distortion Techniques for RF Transmitters in Wireless Systems2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Wireless systems have become an inevitable part of modern technologies serving humankind. The rapid growth towards large dimensional systems, e.g. 5th generation (5G) technologies, incurs needs for improving the performance of the systems and considering aspects to make them as far as possible environmentally friendly in terms of power efficiency, cost, and so on. One of the key parts of every wireless communication system is the radio frequency (RF) power amplifier (PA), which consumes the largest percentage of the total energy. Hence, accurate models of RF PAs can be used to optimize their design and to compensate for signal distortions. This thesis starts with two methods for frequency-domain characterisation to analyse the dynamic behaviour of PAs in 3rd-order non-linear systems. Firstly, two-tone signals superimposed on large-signals are used to analyse the frequency-domain symmetry properties of inter-modulation (IM) distortions and Volterra kernels in different dynamic regions of RF PAs in a single-input single-output (SISO) system. Secondly, three-tone signals are used to characterise the 3rd-order self- and cross-Volterra kernels of RF PAs in a 3 × 3 multiple-input multiple-output (MIMO) system. The main block structures of the models are determined by analysing the frequency-domain symmetry properties of the Volterra kernels in different three-dimensional (3D) frequency spaces. This approach significantly simplifies the structure of the 3rd-order non-linear MIMO model.

    The following parts of the thesis investigate techniques for behavioural modelling and linearising RF PAs. A piece-wise modelling technique is proposed to characterise the dynamic behaviour and to mitigate the impairments of non-linear RF PAs at different operating points (regions). A set of thresholds decompose the input signal into several sub-signals that drive the RF PAs at different operating points. At each operating point, the PAs are modelled by one sub-model, and hence, the complete model consists of several sub-models. The proposed technique reduces the model errors compared to conventional piece-wise modelling techniques.

    A block structure modelling technique is proposed for RF PAs in a MIMO system based on the results of the three-tone characterisation technique. The main structures of the 3rd- and higher-order systems are formulated based on the frequency dependence of each block. Hence, the model can describe more relevant interconnections between the inputs and outputs than conventional polynomial-type models.

    This thesis studies the behavioural modelling and compensation techniques in both the time and the frequency domains for RF PAs in a 3 × 3MIMO system. The 3D time-domain technique is an extension of conventional 2D generalised memory polynomial (GMP) techniques. To reduce the computational complexity, a frequency-domain technique is proposed that is efficient and feasible for systems with long memory effects. In this technique, the parameters of the model are estimated within narrow sub-bands. Each sub-band requires only a few parameters, and hence the size of the model for each sub-band is reduced.

  • 137.
    Alizadeh, Mahmoud
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. University of Gävle.
    Characterisation, Modelling and Digital Pre-DistortionTechniques for RF Transmitters in Wireless Systems2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Wireless systems have become an inevitable part of modern technologies serving humankind. The rapid growth towards large dimensional systems, e.g. 5th generation (5G) technologies, incurs needs for improving the performance of the systems and considering aspects to make them as far as possible environmentally friendly in terms of power efficiency, cost, and so on. One of the key parts of every wireless communication system is the radio frequency (RF) power amplifier (PA), which consumes the largest percentage of the total energy. Hence, accurate models of RF PAs can be used to optimize their design and to compensate for signal distortions. This thesis starts with two methods for frequency-domain characterisation to analyse the dynamic behaviour of PAs in 3rd-order non-linear systems. Firstly, two-tone signals superimposed on large-signals are used to analyse the frequency-domain symmetry properties of inter-modulation (IM) distortions and Volterra kernels in different dynamic regions of RF PAs in a single-input single-output (SISO) system. Secondly, three-tone signals are used to characterise the 3rd-order self- and cross-Volterra kernels of RF PAs in a 3 × 3 multiple-input multiple-output (MIMO) system. The main block structures of the models are determined by analysing the frequency-domain symmetry properties of the Volterra kernels in different three-dimensional (3D) frequency spaces. This approach significantly simplifies the structure of the 3rd-order non-linear MIMO model.

    The following parts of the thesis investigate techniques for behavioural modelling and linearising RF PAs. A piece-wise modelling technique is proposed to characterise the dynamic behaviour and to mitigate the impairments of non-linear RF PAs at different operating points (regions). A set of thresholds decompose the input signal into several sub-signals that drive the RF PAs at different operating points. At each operating point, the PAs are modelled by one sub-model, and hence, the complete model consists of several sub-models. The proposed technique reduces the model errors compared to conventional piece-wise modelling techniques.

    A block structure modelling technique is proposed for RF PAs in a MIMO system based on the results of the three-tone characterisation technique. The main structures of the 3rd- and higher-order systems are formulated based on the frequency dependence of each block. Hence, the model can describe more relevant interconnections between the inputs and outputs than conventional polynomial-type models.

    This thesis studies the behavioural modelling and compensation techniques in both the time and the frequency domains for RF PAs in a 3 × 3MIMO system. The 3D time-domain technique is an extension of conventional 2D generalised memory polynomial (GMP) techniques. To reduce the computational complexity, a frequency-domain technique is proposed that is efficient and feasible for systems with long memory effects. In this technique, the parameters of the model are estimated within narrow sub-bands. Each sub-band requires only a few parameters, and hence the size of the model for each sub-band is reduced.

  • 138.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. Univ Gavle, Sweden.
    Amin, Shoaib
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling. Univ Gavle, Sweden.
    Ronnow, Daniel
    Measurement and Analysis of Frequency-Domain Volterra Kernels of Nonlinear Dynamic 3 x 3 MIMO Systems2017Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 66, nr 7, s. 1893-1905Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multiple-input multiple-output (MIMO) frequencydomain Volterra kernels of nonlinear order 3 are experimentally determined in bandwidth-limited frequency regions. How the effect of higher nonlinear orders can be reduced and how this affects the estimated errors are discussed. The magnitude and the phase of the kernels are Kramers-Kronig consistent. The self-kernels and cross-kernels have different symmetries, and the kernels are therefore determined and analyzed in different regions in the 3-D frequency space. By analyzing the properties along certain paths in the 3-D frequency space, the block structures for the respective kernels are determined. These block structures contain the significant blocks of the general block structures for the third-order kernels. The device under test is an MIMO transmitter for radio frequency signals.

  • 139.
    Alizadeh, Mahmoud
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Royal Institute of Technology, Stockholm, Sweden.
    Amin, Shoaib
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Royal Institute of Technology, Stockholm, Sweden.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Measurement and analysis of frequency-domain Volterra kernels of nonlinear dynamic 3x3 MIMO systems2017Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 66, nr 7, s. 1893-1905Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multiple-input multiple-output (MIMO) frequency-domain Volterra kernels of nonlinear order 3 are experimentally determined in bandwidth-limited frequency regions. How the effect of higher nonlinear orders can be reduced and how this affects the estimated errors are discussed. The magnitude and phase of the kernels areKramers-Kronig consistent. The self- and cross-kernels have different symmetries and the kernels are therefore determined and analyzed in different regions in the 3D frequency space. By analyzing the properties along certain paths in the 3D frequency space, the block structures for the respective kernels are determined. These block structures contain the significant blocks of the general block structures for third-order kernels. The device under test is a MIMO transmitter for radio frequency signals.

  • 140.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Amin, Shoaib
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Rönnow, Daniel
    ATM, University of Gävle.
    Measurement and analysis of frequency-domainVolterra kernels of nonlinear dynamic 3x3 MIMO systems2016Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multiple-input multiple-output (MIMO) frequency-domain Volterra kernels of nonlinear order 3 are experimentally determined in bandwidth-limited frequency regions. How the effect of higher nonlinear orders can be reduced and how this affects the estimated errors are discussed. The magnitude and phase of the kernels areKramers-Kronig consistent. The self- and cross-kernels have different symmetries and the kernels are therefore determined and analyzed in different regions in the 3D frequency space. By analyzing the properties along certain paths in the 3D frequency space, the block structures for the respective kernels are determined. These block structures contain the significant blocks of the general block structures for third-order kernels. The device under test is a MIMO transmitter for radio frequency signals.

  • 141.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. University of Gävle.
    Händel, Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Rönnow, Daniel
    University of Gävle.
    Basis Function Decomposition Approach in Piece-Wise Modeling for RF Power Amplifiers2018Inngår i: 6th Telecommunications forum TELFOR 2018, Belgrade, Serbia, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, a new approach is proposed to decompose the basis functions in a piece-wise modeling technique for nonlinear radio frequency (RF) power amplifiers. The proposed technique treats the discontinuity problem of the model output at the joint points between different operating points, whereas preserves the linear and nonlinear properties of the original model within each region. Experimental results show that the proposed technique outperforms the conventional piece-wise model in terms of model errors.

  • 142.
    Alizadeh, Mahmoud
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. KTH, Teknisk informationsvetenskap.
    Händel, Peter
    KTH, Teknisk informationsvetenskap.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Basis Function Decomposition Approach in Piece-Wise Modeling for RF Power Amplifiers2018Inngår i: 6th Telecommunications forum TELFOR 2018, Belgrade: Telecommunications society , 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, a new approach is proposed to decompose the basis functions in a piece-wise modeling technique for nonlinear radio frequency (RF) power amplifiers. The proposed technique treats the discontinuity problem of the model output at the joint points between different operating points, whereas preserves the linear and nonlinear properties of the original model within each region. Experimental results show that the proposed technique outperforms the conventional piece-wise model in terms of model errors.

  • 143.
    Alizadeh, Mahmoud
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik. KTH, Teknisk informationsvetenskap.
    Händel, Peter
    KTH, Teknisk informationsvetenskap.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Elektronik.
    Behavioral modeling and digital pre-distortion techniques for RF PAs in a 3 × 3 MIMO system2019Inngår i: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787, Vol. 11, nr 10, s. 989-999Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Modern telecommunications are moving towards (massive) multi-input multi-output systems in 5th generation (5G) technology, increasing the dimensionality of the system dramatically. In this paper, the impairments of radio frequency (RF)power amplifiers (PAs) in a 3x3 MIMO system are compensated in both time and frequency domains. A three-dimensional(3D) time-domain memory polynomial-type model is proposed as an extension of conventional 2D models. Furthermore, a 3D frequency-domain technique is formulated based on the proposed time-domain model to reduce the dimensionality of the model, while preserving the performance in terms of model errors. In the 3D frequency-domain technique, the bandwidth of a system is split into several narrow sub-bands, and the parameters of the system are estimated for each subband. This approach requires less computational complexity, and also the procedure of the parameters estimation for each sub-band can be implemented independently. The device-under-test (DUT) consists of three RF PAs including input and output cross-talk channels. The proposed techniques are evaluated in both behavioural modelling and digital pre-distortion(DPD) perspectives. The results show that the proposed DPD technique can compensate the errors of non-linearity and memory effects by about 23.5 dB and 7 dB in terms of the normalized mean square error and adjacent channel leakage ratio, respectively.

  • 144.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. University of Gävle.
    Händel, Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Rönnow, Daniel
    University of Gävle.
    Behavioural modelling and digital pre-distortion techniques for RF PAs in a 3x3 MIMO system2018Inngår i: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Modern telecommunications are moving towards (massive) multi-input multi-output systems in 5th generation (5G) technology, increasing the dimensionality of the system dramatically. In this paper, the impairments of radio frequency (RF)power amplifiers (PAs) in a 3x3 MIMO system are compensated in both time and frequency domains. A three-dimensional(3D) time-domain memory polynomial-type model is proposed as an extension of conventional 2D models. Furthermore, a 3D frequency-domain technique is formulated based on the proposed time-domain model to reduce the dimensionality of the model, while preserving the performance in terms of model errors. In the 3D frequency-domain technique, the bandwidth of a system is split into several narrow sub-bands, and the parameters of the system are estimated for each subband. This approach requires less computational complexity, and also the procedure of the parameters estimation for each sub-band can be implemented independently. The device-under-test (DUT) consists of three RF PAs including input and output cross-talk channels. The proposed techniques are evaluated in both behavioural modelling and digital pre-distortion(DPD) perspectives. The results show that the proposed DPD technique can compensate the errors of non-linearity and memory effects by about 23.5 dB and 7 dB in terms of the normalized mean square error and adjacent channel leakage ratio, respectively.

  • 145.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. Department of Electronics, Mathematics and Natural Sciences, University of Gävle (HiG), Gävle, Sweden.
    Rönnow, D.
    Händel, Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    Characterization of Volterra Kernels for RF Power Amplifiers Using a Two-Tone Signal and a Large-Signal2018Inngår i: 2018 12th International Conference on Communications, COMM 2018 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 351-356, artikkel-id 8430119Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The 3rd-order Volterra kernels of a radio frequency (RF) power amplifier (PA) are characterized using a large-signal and a two-tone probing-signal. In this technique, the magnitude and phase asymmetries of the kernels of the PA excited by the probing-signal are analyzed in different amplitude regions of the large-signal. The device under test is a class-AB PA operating at 2.14 GHz. The maximum sweeping frequency space of the probing-signal is 20 MHz. The results indicate that the Volterra kernels of the PA show different behaviors (frequency dependency and asymmetry) in different regions.

  • 146.
    Alizadeh, Mahmoud
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. Department of Signal Processing, ACCESS Linnaeus Center, The Royal Institute of Technology (KTH), Stockholm, Sweden.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    A two-tone test for characterizing nonlinear dynamic effects of radio frequency amplifiers in different amplitude regions2016Inngår i: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 89, s. 273-279Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new two-tone test method for radio frequency power amplifiers is presented. The test signal is a two-tone probing-signal superimposed on large-signals of different amplitude. The amplifier is, thus, excited in different amplitude regions. The amplitude and phase of the 3rd order intermodulation (IM) products are measured vs. frequency spacing and probing-signal amplitude in each region. The IM magnitude is a measure of the nonlinearity, while the frequency dependence and asymmetry are measures of the memory effects in the different regions. A Doherty and a class-AB amplifier were tested. For both amplifiers the IM magnitude increased by ∼15 dB from the lowest to the highest amplitude region. For the Doherty amplifier the behavior of the IM products vs. frequency spacing was similar in all regions, indicating similar memory effects. For the class-AB amplifier the IM vs. frequency spacing was significantly different in the different regions, which indicates different memory effects.

  • 147.
    Alizadeh, Mahmoud
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. University of Gävle.
    Rönnow, Daniel
    University of Gävle.
    Händel, Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
    A new Block-Structure Modeling Technique for RF Power Amplifiers in a 2×2 MIMO System2017Inngår i: 2017 13th International Conference on Advanced Technologies, Systems and Services in Telecommunications, TELSIKS 2017 - Proceeding, Nis, Serbia: IEEE, 2017, Vol. 2017, s. 224-227Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A new block-structure behavioral model is proposed for radio frequency power amplifiers in a 2×2 multiple-input multiple-output system including input cross-talk. The proposed model forms kernels of blocks of different nonlinear order that correspond to the significant frequency response of measured frequency domain Volterra kernels. The model can therefore well describe the input-output relationships of the nonlinear dynamic behavior of PAs. The proposed model outperforms conventional models in terms of model errors.

  • 148.
    Alizadeh, Mahmoud
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik. KTH.
    Rönnow, Daniel
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Händel, Peter
    KTH.
    Isaksson, Magnus
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    A new Block-Structure Modeling Technique for RF Power Amplifiers in a 2x2 MIMO System2017Inngår i: 13th International Conference on Advanced Technologies, Systems and Services in Telecommunications (TELSIKS) / [ed] Milovanovic, B. D.; Doncov, N. S.; Stankovic, Z. Z.; Dimitrijevic, T. Z., IEEE , 2017, s. 224-227Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A new block-structure behavioral model is proposed for radio frequency power amplifiers in a 2x2 multiple-input multiple-output system including input cross-talk. The proposed model forms kernels of blocks of different nonlinear order that correspond to the significant frequency response of measured frequency domain Volterra kernels. The model can therefore well describe the input-output relationships of the nonlinear dynamic behavior of PAs. The proposed model outperforms conventional models in terms of model errors.

  • 149.
    allouh, mahmoud
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Gomez, Carlos
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Shockwarner for a Smartphone2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 150.
    AL-MAMUN, ABDULLAH
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    ULLAH, MOHAMMAD RAFIQ
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Cognitive Radio for Short Range Systems based on Ultra-Wideband2011Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    Cognitive Radio (CR) has been proposed as a promising and effective technology to improve radio spectrum utilization. It can change its transmitter parameters depending on the environment in which it operate based on interaction. In CR, a number of different methods of spectrum sensing are used to identify the presence of signal transmission. Among them, the multitaper method (MTM), has been investigated in this thesis paper at the same time with other sensing methods, recently seems to be the best choice for spectrum sensing CR because of its accurate identification and estimation, quick computation, and regularization. This thesis paper is examining how CR can be utilized in short range systems based on Ultra-Wideband (UWB). UWB is a promising technology in wireless communication use for high speed data transmission with low power utilization or long distance localization in both military, radar, sensor, data collection, tracking or commercial application. UWB has the ability to move between very low data rate or very high data rate, short range distance or long range distance applications. Impulse radio UWB (IR-UWB) shows some impressive characteristics in short-range communication systems with varieties of throughput option including high data rates. The strong synergy between the aims of CR and features of IR-UWB has been shown in this thesis. Our key objective is to understand how CR can be applied to UWB systems.

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