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  • 201. Dahl, Mattias
    Applied Array-Filter Design: Methods and Applications2000Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 202. Dahl, Mattias
    On-Site Calibrated Microphone Array for Mobile Communication2000Konferensbidrag (Refereegranskat)
  • 203. Dahl, Mattias
    Speech Recognition in Severely Disturbed Environments Combining Ear-Mic and Active Noise Control2002Konferensbidrag (Refereegranskat)
  • 204. Dahl, Mattias
    et al.
    Claesson, Ingvar
    A Neural Network Trained Microphone Array System for Noise Reduction1996Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a neural network based microphone array system, which is capable to continuously perform speech enhancement and adaptation to nonuniform quantization, such as A-law and $mu@-law. Such a quantizer is designed to increase the Signal to Quantization Noise Ratio (SQNR) for small amplitudes in telecommunications systems. The proposed method primarily developed for hands-free mobile telephones, suppresses the ambient car noise with approximately 10 dB. The system is based upon a multi-layered nonlinear back-propagation trained network by using a built-in calibration technique.

  • 205. Dahl, Mattias
    et al.
    Claesson, Ingvar
    Acoustic Echo Cancelling with Michrophone Arrays1995Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report describes a novel method to perform acoustic echo cancelling with microphone arrays. The method employs a digital self-calibrating microphone system. The on-site calibration process is a simple indirect calibration which adapts in each special case to the environment and electronic equipment. The method also continuously takes into account environmental disturbances such as car engine noise and fan noise. The method is primarily aimed at handsfree mobile telephones, by suppressing the handsfree loudspeaker and car noise simultaneously. The report also contains an extensive evaluation in a car.

  • 206. Dahl, Mattias
    et al.
    Claesson, Ingvar
    Acoustic Noise and Echo Canceling with Microphone Array1999Ingår i: IEEE Transactions on Vehicular Technology , ISSN 0018-9545 , Vol. 48, nr 5, s. 1518-1526Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel method of performing acoustic echo canceling using microphone arrays is presented. The method employs a digital self-calibrating microphone system. The calibration process is a simple indirect on-site calibration that adapts to the particulars of the acoustic environment and the electronic equipment in use. Primarily intended for handsfree telephones in automobiles, the method simultaneously suppresses the handsfree loudspeaker and car noise. The system also continuously takes into account disturbances such as fan noise. Examples from an extensive evaluation in a car are also included. Typical performance results demonstrate 20-dB echo cancellation and 10-dB noise reduction simultaneously.

  • 207. Dahl, Mattias
    et al.
    Claesson, Ingvar
    Nordebo, Sven
    Antenna Array Design using Dual Nested Complex Approximation2003Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a new practical approach to complex Chebyshev approximation by semi-infinite linear programming. The approximation problem may be general with arbitrary complex basis functions. By the new front-end technique, the associated semi-infinite linear programming problem is solved exploiting the finiteness of the related Lagrange multipliers by adapting finite--dimensional linear programming to the dual semi--infinite problem, and thereby taking advantage of the numerical stability and efficiency of conventional linear programming software packages. Furthermore, the optimization procedure is simple to describe theoretically and straightforward to implement in computer coding. The new design technique is therefore highly accessible. The new algorithm is formally introduced as the linear Dual Nested Complex Approximation (DNCA) algorithm. The DNCA algorithm is versatile and can be applied to a variety of applications such as narrow-band as well as broad-band beamformers with any geometry, conventional Finite Impulse Response (FIR) filters, analog and digital Laguerre networks, and digital FIR equalizers. The proposed optimization technique is applied to several numerical examples dealing with the design of a narrow-band base-station antenna array for mobile communication. The flexibility and numerical efficiency of the proposed design technique are illustrated with these examples where hundreds of antenna elements are optimized without numerical difficulties.

  • 208. Dahl, Mattias
    et al.
    Claesson, Ingvar
    Nordebo, Sven
    Simultaneous Echo Cancellation and Car Noise Suppression Employing a Microphone Array1997Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a method to simultaneously perform 20 dB acoustic echo cancellation and 15-20 dB speech enhancement using an adaptive microphone array combined with spectral subtraction. Primarily intended for handsfree telephones in automobiles, the microphone array system simultaneously emphasizes the near-end talker and suppresses the handsfree loudspeaker and the broadband car noise. The array system is based on a fast and efficient on-site calibration and can be used in other situations such as conventional speaker phones.

  • 209. Dahl, Mattias
    et al.
    Claesson, Ingvar
    Nordebo, Sven
    Nordholm, Sven
    Chebyshev Optimization of Circular Arrays1999Konferensbidrag (Refereegranskat)
  • 210. Dahl, Mattias
    et al.
    Claesson, Ingvar
    Nordebo, Sven
    Nordholm, Sven
    En adaptiv mikrofon för bullerundertryckning i bil1994Konferensbidrag (Refereegranskat)
  • 211. Dahl, Mattias
    et al.
    Claesson, Ingvar
    Nordholm, Sven
    Grbic, Nedelko
    Adaptive Microphone Array System for Speech Enhancement1997Konferensbidrag (Refereegranskat)
  • 212. Dahl, Mattias
    et al.
    Claesson, Ingvar
    Nordholm, Sven
    Nordebo, Sven
    Acoustic Echo and Noise Cancelling using Microphone Arrays1996Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a new method to simultaneously perform 20 dB acoustic echo cancellation and 10 dB speech enhancement utilizing an adaptive microphone array. The system is based on a fast and efficient on-site calibration. Primarily intended for handsfree telephones in automobiles, the microphone array system simultaneously emphasizes the near-end talker and suppresses the handsfree loudspeaker and car noise. The method can also be used in other situations such as conventional speaker phones.

  • 213. Dahl, Mattias
    et al.
    Claesson, Ingvar
    Nordholm, Sven
    Nordebo, Sven
    Microphone Array and Acoustic Echo Canceller for Use in Hands-free Mobile Telephones1996Konferensbidrag (Refereegranskat)
  • 214. Dahl, Mattias
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    A New General Front-End Technique for Complex Quadratic Programming: Applications to Array Pattern Synthesis2000Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Behandlar antennarrayteknik för mobiltelefoni.

  • 215. Dahl, Mattias
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    Complex Approximation by Semi-Infinite Quadratic Programming2000Konferensbidrag (Refereegranskat)
  • 216. Dahl, Mattias
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    Complex Chebyshev Optimization Using Conventional Linear Programming: A versatile and comprehensive solution2000Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Behandlar antennarray teknik för mobiltelefoni.

  • 217. Dahl, Mattias
    et al.
    Tran, To
    Claesson, Ingvar
    Nordebo, Sven
    Design of antenna array using dual nested complex approximation2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a new practical approach to complex Chebyshev approximation by semi-infinite linear programming. By the new front-end technique, the associated semi-infinite linear programming problem is solved exploiting the finiteness of the related Lagrange multipliers by adapting finite-dimensional linear programming to the dual semi-infinite problem, and thereby taking advantage of the numerical siability and efficiency of conventional linear programming software packages. Furthermore, the optimization procedure is simple to describe theoretically and straightforward to implement in computer coding. The new design technique is therefore. highly accessible. The algorithm is formally introduced as the linear Dual Nested Complex Approximation (DNCA) algorithm. The DNCA algorithm is versatile and can be applied to a variety of applications such as narrow-band as well as broad-band beamformers with any geometry, conventional Finite Impulse Response (FIR) filters, analog and digital Laguerre networks. and digital FIR equalizers. The proposed optimization technique is applied to several numerical examples dealing with the design of a narrow-band base-station antenna array for mobile communication.

  • 218.
    Dalasari, Venkata Gopi Krishna
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Jayanty, Sri Krishna
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Low Light Video Enhancement along with Objective and Subjective Quality Assessment2016Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Enhancing low light videos has been quite a challenge over the years. A video taken in low light always has the issues of low dynamic range and high noise. This master thesis presents contribution within the field of low light video enhancement. Three models are proposed with different tone mapping algorithms for extremely low light low quality video enhancement. For temporal noise removal, a motion compensated kalman structure is presented. Dynamic range of the low light video is stretched using three different methods. In Model 1, dynamic range is increased by adjustment of RGB histograms using gamma correction with a modified version of adaptive clipping thresholds. In Model 2, a shape preserving dynamic range stretch of the RGB histogram is applied using SMQT. In Model 3, contrast enhancement is done using CLAHE. In the final stage, the residual noise is removed using an efficient NLM. The performance of the models are compared on various Objective VQA metrics like NIQE, GCF and SSIM.

    To evaluate the actual performance of the models subjective tests are conducted, due to the large number of applications that target humans as the end user of the video.The performance of the three models are compared for a total of ten real time input videos taken in extremely low light environment. A total of 25 human observers subjectively evaluated the performance of the three models based on the parameters: contrast, visibility, visually pleasing, amount of noise and overall quality. A detailed statistical evaluation of the relative performance of the three models is also provided.

  • 219. Dam, Hai Huyen
    et al.
    Nordberg, Jörgen
    Nordholm, Sven
    Non-Causal Delayless Subband Adaptive Equalizer2002Konferensbidrag (Refereegranskat)
    Abstract [en]

    In wireless communication, multiple versions of the transmitted signals arrive at the receiver with different attenuations and time delays. Thus, an equalizer with long filter is required at the receiver to reverse the multipath effects. In this paper, a new non-causal delayless subband equalizer structure is proposed to reduce the computational complexity of the equalizer and to improve the channel tracking capability. This structure avoids the additional delays usually associated with the subband schemes. A design method is formulated to minimize the aliasing effect of the filter bank in the subbands. The significance of employing a non-causal equalizer is also emphasized. Simulation results show that the performance of the new structure is significantly improved by using the design method. Moreover, the complexity of the new subband equalizer is a fraction of the equivalent fullband at the expense of small degradation in the performance.

  • 220. Dam, Hai Huyen
    et al.
    Nordberg, Jörgen
    Nordholm, Sven
    Zepernick, Hans-Jürgen
    Stacking Methods for Non-Causal Delayless Subband Addaptive Equalizer2002Konferensbidrag (Refereegranskat)
  • 221. Dam, Hai Huyen
    et al.
    Nordebo, Sven
    Svensson, Lars
    Approximation of Classical IIR Filters with Additional Specifications2000Ingår i: IEEE transactions on circuits and systems. 2, Analog and digital signal processing (Print), ISSN 1057-7130, E-ISSN 1558-125X, Vol. 47, nr 12, s. 1536-1540Artikel i tidskrift (Refereegranskat)
  • 222. Dam, Hai Huyen
    et al.
    Nordebo, Sven
    Svensson, Lars
    Design of Digital Filters as the Sum of Two All--Pass Functions Using the Cepstrum Technique2003Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 51, nr 3, s. 726-31Artikel i tidskrift (Refereegranskat)
  • 223. Dam, Hai Huyen
    et al.
    Nordebo, Sven
    Teo, Kok Ley
    Cantoni, Antonio
    Design of Linear Phase FIR FIlters with Recursive Structure and Discrete Coefficients1998Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider a class of FIR filters defined by the first order difference routing digital filter (DRDF) structure and sums of two powers-of-two coefficients. A novel design method is developed for constructing high quality filters with reference to the min-max error criterion. This method is highly efficient in terms of computational time. Simulation studies show a large improvement over existing methods such as quantization. In some cases, the peak ripple magnitude over the stop and pass bands is reduced by up to 13 dB over the quantization method. These results are achieved even for cases involving small number of delays.

  • 224. Dam, Hai Huyen
    et al.
    Nordebo, Sven
    Teo, Kok Ley
    Cantoni, Antonio
    FIR Filter Design over Discrete Coefficients and Least Square Error2000Ingår i: IEE Proceedings - Vision Image and Signal Processing, ISSN 1350-245X, E-ISSN 1359-7108, Vol. 147, nr 5, s. 543-548Artikel i tidskrift (Refereegranskat)
  • 225. Dam, Hai Huyen
    et al.
    Nordebo, Sven
    Teo, Kok Ley
    Cantoni, Antonio
    FIR Filter Design Over Discrete Powers-of-Two Coefficients1998Konferensbidrag (Refereegranskat)
  • 226. Dam, Hai Huyen
    et al.
    Nordebo, Sven
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Teo, Kok Ley
    Cantoni, Antonio
    Frequency Domain Design for Digital Laguerre Networks2000Ingår i: IEEE transactions on circuits and systems. 1, Fundamental theory and applications, ISSN 1057-7122, Vol. 47, nr 4, s. 578-581Artikel i tidskrift (Refereegranskat)
  • 227. Dam, Hai Huyen
    et al.
    Nordholm, Sven
    Cantoni, Antonio
    Haan, Jan Mark de
    Iterative Method for the Design of DFT Filter Bank2004Ingår i: IEEE transactions on circuits and systems. 2, Analog and digital signal processing (Print), ISSN 1057-7130, E-ISSN 1558-125X, Vol. 51, nr 11, s. 581-6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multi-rate adaptive filters have numerous advantages such as low computational load, fast convergence and parallelism in the adaptation. Drawbacks when using multi-rate processing are mainly related to aliasing and reconstruction effects. These effects can be minimized by introducing appropriate problem formulation and employing sophisticated optimization techniques. In this paper, we propose a formulation for the design of filter bank which controls the distortion level for each frequency component directly and minimizes the inband aliasing and the residual aliasing between different subbands. The advantage of this problem formulation is that the distortion level can be weighted for each frequency depending on the particular practical application. A new iterative algorithm is proposed to optimize simultaneously over both the analysis and the synthesis filter banks. This algorithm is shown to have a unique solution for each iteration. For a fixed distortion level, the proposed algorithm yields a significant reduction in both the inband aliasing and the residual aliasing levels compared to existing methods applied to the numerical examples.

  • 228. Dam, Hai Huyen
    et al.
    Teo, Kok Ley
    Liu, Yang
    Nordebo, Sven
    Optimum Pole Position for Digital Laguerre Network with Least Square Error Criterion2000Ingår i: Optimization Methods and Applications, Kluwer academic publisher , 2000, s. 321-330Kapitel i bok, del av antologi (Refereegranskat)
  • 229. Dam, Hai Huyen
    et al.
    Teo, Kok Ley
    Nordebo, Sven
    Cantoni, Antonio
    The Dual Parameterization Approach to Optimal Least Square FIR Filter Design Subject to Maximum Error Constraints2000Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X , Vol. 48, nr 8, s. 2314-2320Artikel i tidskrift (Refereegranskat)
  • 230. Dam, Hai Huyen
    et al.
    Zepernick, Hans-Jürgen
    Nordberg, Jörgen
    Nordholm, Sven
    Application of a Global Optimization Method to the Design of Complex Spreading Sequences2002Konferensbidrag (Refereegranskat)
  • 231. Dam, Hai Huyen
    et al.
    Zepernick, Hans-Jürgen
    Nordberg, Jörgen
    Nordholm, Sven
    Complex Spreading Sequence Design2002Konferensbidrag (Refereegranskat)
    Abstract [en]

    The performance of code division multiple access system depends on the correlation of the employed spreading code. Low cross-correlation values between spreading sequences are desired to suppress multiple access interference. An auto-correlation function with with a distinct peak enables proper synchronization and suppresses intersymbol interference. However, these requirements contradict each other and a trade-off needs to be established. In this paper, a global two dimensional optimization method is proposed to minimize auto-correlation with cross-correlation being allowed to lie within a fixed region. This approach is applied to design a set of complex valued spreading sequences.

  • 232. Dam, Hai Huyen
    et al.
    Zepernick, Hans-Jürgen
    Nordberg, Jörgen
    Nordholm, Sven
    Design of Complex Spreading Sequences2002Konferensbidrag (Refereegranskat)
  • 233.
    Datla, Venkata Rami Reddy
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Implementation and evaluation of spectral subtraction (SS) with minimum statistics and wiener beamformer combination2013Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In mobile communication systems, speech signal can be distorted by acoustic noise such as babble speech noise. Such kind of noises can distort the quality of speech signal to a high extent. All speech processing equipments like the noise cancelling headphones and hearing aids should be able to filter different kinds of interfering signals and present a clear sound to the listener. Eliminating the noise present in the signal without affecting the original speech is a challenge and a topic of research in these days. This paper concentrates on enhancing the quality of speech and reducing the noise on same hand by making use of Wiener Beamformer and Spectral Subtraction based on minimum statistics. Wiener beam former is implemented based on sub-band approach and Direction of Arrival capabilities. Both the methods are cascaded in a unique fashion so maximum speech intelligibility is obtained. All the systems are tested with various positions of noise and speech source with reference to the microphone array. All proposed methods are implemented, evaluated and results are simulated using MATLAB. The performance of the method is analyzed using Signal-to-Noise Ratio improvement (SNRI).

  • 234. Davis, Alan
    et al.
    Low, Siow Yong
    Nordholm, Sven
    Grbic, Nedelko
    A subband space constrained beamformer incorporating voice activity detection2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper introduces a new subband adaptive space constrained beamforming structure for use in hands-free speech enhancement applications. The scheme incorporates a space constrained source model and voice activity information through the integration of a voice activity detector (VAD). The VAD information is used to estimate noise covariance information during non-speech periods and to optimally estimate the source power spectral density (PSD), which is used to provide a spectrally optimized constraint on the source. The proposed structure is evaluated in a real car environment, yielding results which compare well to the optimal Wiener solution where full knowledge of the source is known. ©2005 IEEE.

  • 235.
    Dernaika, Ghina
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Khavtasi, Sophia
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för telekommunikationssystem.
    Multimedia Codec Evaluation and Overview2007Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Movies, songs, conferences, video streams and other multimedia services are spreading in everybody’s life, needs and work. Different types of audio and video codecs of various qualities appear to be used for different purposes. However, each codec can be suitable for a special usage, as for example a codec that can be use for high quality film may not be suitable for streaming it into network. The main purpose of this thesis is to compare the performance of different codecs in one particular scenario and indicate which codec performance is the best. The thesis work includes the investigation of several codec aspects (audio and video) and problems related to choosing a multimedia codec (coder/decoder) suitable for large-scale multimedia distribution over the Internet. More specifically, the work focuses on various features of modern media codecs, compares them and finds the best application for each of them. Furthermore, the thesis provides an overview of available research results related to this work and codec comparison tables for codecs and their features. Additionally, as part of this work, a testbed was developed to measure the performance of codecs when used to stream media over a network. The testbed enabled the collection of various QoS parameters, such as bandwidth usage and burst, size for each codec considered in this thesis.

  • 236.
    Dey, Ajoy Kumar
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Saha, Susmita
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Acoustic Beamforming: Design and Development of Steered Response Power With Phase Transformation (SRP-PHAT).2011Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Acoustic Sound Source localization using signal processing is required in order to estimate the direction from where a particular acoustic source signal is coming and it is also important in order to find a soluation for hands free communication. Video conferencing, hand free communications are different applications requiring acoustic sound source localization. This applications need a robust algorithm which can reliably localize and position the acoustic sound sources. The Steered Response Power Phase Transform (SRP-PHAT) is an important and roubst algorithm to localilze acoustic sound sources. However, the algorithm has a high computational complexity thus making the algorithm unsuitable for real time applications. This thesis focuses on describe the implementation of the SRP-PHAT algorithm as a function of source type, reverberation levels and ambient noise. The main objective of this thesis is to present different approaches of the SRP-PHAT to verify the algorithm in terms of acoustic enviroment, microphone array configuration, acoustic source position and levels of reverberation and noise.

  • 237.
    Dhakal, Prabesh
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Tiwari, Prabhat
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Chan, Pawan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Perceptual Video Quality Assessment Tool2014Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    In our research work, we have designed the tool that can be used to conduct a mass-scale level survey or subjective tests. ACR is the only method used to carry out the subjective video assessment. The test is very useful in the context of a video streaming quality. The survey can be used in various countries and sectors with low internet speeds to determine the kind of video or the compression technique, bit rate, or format that gives the best quality.

  • 238.
    Dhakal, Rajendra
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Mahat, Sagar Raj
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Performance Analysis of DF Relay Systems with Keyhole and Correlation Effects2011Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In recent years, the innovation of multiple-input multiple-output (MIMO) has completely changed the face of wireless communication system. Especially, the concept of MIMO is evolved to fulfill the demand of multimedia services. However, challenges have risen to the system provider for maintaining the quality of service (QoS) and reliability of MIMO system. Additionally, very recently, cooperative communication has been proposed in order to face and deal with the shortcomings of MIMO system. In cooperative communication, the addition of relay between source and destination enhances the QoS and reliability of wireless system. The main purpose of this paper is to derive the closed form analytical expressions of symbol error rate (SER) of M-ary phase shift keying (MPSK) for MIMO decode-and forward (DF) relay system. Besides, SER derivation is based on moment generating function (MGF) of the overall system. In our case, we only deal with a downlink MIMO DF relay system. Here, we consider an $n_t$-antenna at the source $S$, an $n_r$-antenna at the relay $R$ and an $n_d$-antenna at the destination $D$, where the propagated signal from the source passes through keyhole and correlated channel. Further, the same orthogonal space time block codes (OSTBC) is applied to source-destination, source-relay and relay-destination link to exploit the maximal diversity gain. Furthermore, we analyze the effects of MPSK modulation on MIMO DF system under different values of correlation coefficient by combining the different antenna pairs at different nodes. Beside this, we compare keyhole and no keyhole MIMO relay systems with fix value of correlation coefficient and antenna pairs. With the use of cooperative scheme, effects of keyhole on MIMO DF architecture can be minimized to certain level. Eventually, our simulation analysis excellently matches with analytical results, which is sufficient to validate our work.

  • 239.
    Dimkovski, Zlate
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Characterization of a Cylinder Liner Surface by Roughness Parameters Analysis2006Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Cylinder liner surface topology greatly affects oil consumption and wear of engines. Surface optimization would be greatly facilitated by automatic quality control. Surface roughness definitions, parameters, and measurement techniques were reviewed and samples of different Volvo truck engine cylinder liner types were measured. Routines for extracting and computing groove parameters, useful in the automation of quality control in production, were developed, implemented in MATLAB and applied on the samples. The principles of the last two steps procedures needed to fully automate the surface grading by roughness parameters analysis were described.

  • 240.
    Dinakaran, Manoj
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Prasad., Rotu Ramakrishna
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    SINGLE CHANNEL SPEECH DEREVERBERATION FOR ACOUSTIC SIGNALS2013Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Reverberation in speech is one of the primary factors caused by delayed image of speech signal plus the intended speech signals. Reverberation degrades the quality of the speech signal when recorded by a distant microphone and in the hands free telephonic scenarios. This causes a big problem for carrying out communication between people or in automatic voice recognition applications in which the voice is not properly recognized by the voice recognition applications. Here dereverberation is performed considering two mostly used real time scenarios. They are Non blind dereverberation and Blind dereverberation. Dereverberation in a hands free scenario using various adaptive algorithms has been a research topic for several years. This scenario is considered as a Non blind situation. For this non blind situation, here two types of recently proposed adaptive algorithms are used. They are Non Parametric Variable Step Size Normalized Least Mean Square (NP VSS NLMS) and Variable Step Size Normalized Least Mean Square (VSS NLMS) adaptive filters. The scenario in which the knowledge of clear speech signal is unknown is considered to be the blind situation. Here we introduce the Non parametric Variable Step Size NLMS (NP VSS NLMS) based step size adaptive filter in Maximum kurtosis linear prediction (LP) residual of speech to remove the reverberations from the reverberated speech signal. The performances of both blind dereverberation and non blind dereverberation are analyzed using Spectrogram plot, Reverberation Index (RI) and Speech Distortion (SD) parameters.

  • 241. Dinesh, V Sai Krishna
    et al.
    Vishal, K
    Online assessment of practical knowledge in electronics laboratory2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Increasing globalization and opportunities for engineers around the world to work or study anywhere mean challenges for universities wanting the best students as well as for the companies wanting for the most skilled staff. The social and economic conditions of the country where the student has studied have an impact on his level of knowledge though the attained degree is similar in all countries. It is not enough to use scores as a base for decisions. Some tests for software courses, English language etc. exists. Now the challenge is to design and implement a common test to analyze the knowledge of the student/ test taker and certify him in performing laboratory work and operating electronic instruments. A solution to overcome the problem of recruiting companies in this global market as well as the universities to select the meritorious from worldwide would be by implementing a Common Electronics Lab Operation Test. A test with the operation of the equipment in electronics laboratory has importance as test takers are tested in their knowledge with practical equipment using simulated and remote labs which are identical to the operation of real. The testing system is proposed to be developed using latest remotely operated real labs

  • 242.
    Ding, Yuan
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Wu, YiBing
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    TDD Linear Precoding Methods for Next Generation Mobile Communication Systems2011Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    I denna avhandling ger vi våra förutsägelse om nästa mobila kommunikationssystem, som utökar kapaciteten i rumsliga domän med hjälp av ett stort antal antenner och fortfarande håller förenligheten med den tidigare generationens mobila kommunikationssystem. Men för det oförenliga del-precoding-in sådana nya system, presenterar vi två TDD linjär precoding metoder i denna avhandling. Genom simuleringar kan vi se att dessa två precoding metoder är möjlig för det nya systemet och bidra till att öka dess kapacitet prestanda.

  • 243.
    , D.M.BAPPY
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    RAHMAN, MD HAMIDUR
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    A Study in 3D Structure Detection Implementing Forward Camera Motion2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In this thesis we have studied detection of 3D structures having a forward camera movement which has strong influence of translation along the optical axis of the camera. During the forward movement the camera might undergoes rotation and translation .We have used “Plane plus Parallax” algorithm to cancel out this unwanted rotation. The input to the algorithm is a sequence of frames aligned with respect to a certain planar surface. The algorithm gives three types of outputs. (i) Dense correspondence across all frames. (ii) Dense 3D structure relative to the planar surface. (ii) Focus of Expansion (FOE) in all frames with respect to reference frame. Camera calibration is not needed for this algorithm. We have applied this algorithm to real world images and synthetic images. In both cases the 3D structure information could be obtained clearly even for objects far from the reference plane. Our result shows the potential of the method in 3D reconstruction implementing ego-motion of a single camera.

  • 244.
    Dorairaj, Prabhu
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Ramamoorthy, Saranya
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Ramalingam, Ashok Kumar
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Emergency based remote collateral tracking system using google's android mobile platform2012Ingår i: Advances in Intelligent and Soft Computing, New Delhi, 2012, Vol. 167, nr 2, s. 391-403Konferensbidrag (Refereegranskat)
    Abstract [en]

    Introduction of Smart phones redefined the usage of mobile phones in the communication world. Smart phones are equipped with various sophisticated features such as Wi-Fi, GPS navigation, high resolution camera, touch screen with broadband access which helps the mobile phone users to keep in touch with the modern world. Many of these features are primarily integrated with the mobile operating system which is out of reach to public, by which the users can't manipulate those features. Google came up with an innovative operation system termed as ANDROID, which is open system architecture with customizable third party development and debugging environment which helps the user's to manipulate the features and to create their own customizable applications. In this paper, 'Emergency Based Remote Collateral Tracking System' application using Google's Android Mobile Platform is addressed. Emergency is divided into three categories: heart beat based emergency, security threats like personal safety and road accidents. This application is targeted to a person who is driving a vehicle. Heart rate monitoring device is integrated with our application to sense the heart beat of a person driving the vehicle and if there is any abnormalities in the heart beat, then our application performs a dual role. One in which, application uses a GPS to track the location information of the user and send those location information as a message via SMS, email and post it on Facebook wall Simultaneously, an emergency signal is sent to Arduino Microcontroller. Road accidents are quite common, this application is also designed to detect the accident using the sensors in the Android Mobile. Security threat can occur anywhere, our application also answers for personal safety, when the user interacts with the application by pressing the button, then automatically the application generates the geographical information and sends that location information via SMS and email to a pre-stored emergency contact and the same information will be posted on user's Facebook wall. This application is written in JAVA programming language which runs on Eclipse Integrated Development Kit.

  • 245.
    DORNADULA, UDAY CHAITANYA
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    DEVUNURI, PRIYANKA
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Implementation of No-Reference Image Quality Assessment in Contourlet Domain2014Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In image processing, efficiency term refers to the ability in capturing significant information that is sensitive to human visual system with small description. Natural images or scenes that contain intrinsic geometrical structures (contours) are key features of visual information. The existing transform methods like Fourier transformation, wavelets, curvelets, ridgelets etc., have limitations in capturing directional information in an image and their compatibility with compression methods. Hence, to capture the directional information or natural scene statistics of an image and to handle the compatibility over distortion methods, Contourlet Transform (CT) can be a promising approach. The goal of no-reference image quality assessment using contourlet transform (NR IQACT) is to establish a rational computational model to predict the visual quality of an image. In this thesis we implemented an improved Natural Scene Statistics (NSS) model that blindly measures image quality using the concept of Contourlet Transform (CT). In fact, natural scenes contain nonlinear dependencies that can be disturbed by a compression process. This disturbance can be quantified and related to human perception of quality.

  • 246.
    Du, Jiaying
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Utveckling och undersökning av algoritmer för MEMS-gyron2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Examensarbetet har genomförts med utveckling och undersökning av signalbehandlingsalgoritmer för MEMS-gyron. Idag används många MEMS-gyron i olika elektronikprodukter. Företaget Motion Control utvecklar elektronik och inbyggd programvara och de har bland annat tagit fram MultiPos, som är en huvudmus för rörelsehindrade. MultiPos är en MEMS-gyro-baserad datormus. MEMS-gyron används för att känna av huvudrörelser som användaren gör, men det är önskvärt med en bättre signalbehandling, d.v.s. kunna reducera brus, offset och drift. Olika gyron har olika egenskaper och algoritmen måste kunna fungera för ett valfritt MEMS-gyro. Åtta olika algoritmer har undersökts, simulerats med hjälp av MATLAB och implementerats i en dsPIC med hjälp av MPLAB. De algoritmer som testats är högpassfilter, lågpassfilter, LMS, Wavelet, Kalman, WFLC, tröskelvärdesmetod och fördröjningsmetod. Efter jämförelse, sammanställningar och systemtest kan de olika filterfunktionerna användas enskilt eller i kombination med varandra för att förbättra mätsignalen i enlighet med filtrenas olika karaktärer.

  • 247. Duong, Quang Trung
    Exact Closed-Form Expression for Average Symbol Error Rate of MIMO-MRC Systems2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we derive closed-form expressions for exact average symbol error rate (SER) of multiple-input multiple-output (MIMO)-maximum ratio combining (MRC) systems with M-ary modulations. We obtain the tractable compact closed-form expressions for the average SER in terms of the Gauss and Appell hypergeometric functions which are provided as library functions in common mathematical softwares such as MAPLE and MATHEMATICA. The analysis is validated by comparing with Monte-Carlo simulations and we further show that our general SER expressions reduce to the previous known results for binary signals (M=2) as a special case. Applying the series representation of the Gauss and Appell hypergeometric function, we derive a very tight approximation for the average SER

  • 248. Duong, Quang Trung
    On Cooperative Communications and Its Application to Mobile Multimedia2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    With the rapid growth of multimedia services, future generations of wireless communications require higher data rates and a more reliable transmission link while keeping satisfactory quality of service. In this respect, multipleinput multiple-output (MIMO) antenna systems have been considered as an efficient approach to address these demands by offering significant multiplexing and diversity gains over single-antenna systems without increasing requirements on radio resources such as bandwidth and power. Although MIMO systems can unfold their huge benefit in cellular base stations, they may face limitations when it comes to their deployment in mobile handsets. In particular, the typically small-size of mobile handsets makes it impractical to deploy multiple antennas. To overcome this drawback, the concept of cooperative communications has recently been proposed and gained large interest in the research community. The key idea is to form a virtual MIMO antenna array by utilizing a third terminal, a so-called relay node, which assists the direct communication. After receiving the source’s message, the relay processes and forwards it to the destination. With this approach, the benefits of MIMO systems can be attained in a distributed fashion. Furthermore, cooperative communications can efficiently combat the severity of fading and shadowing effects through the assistance of relay terminals. It has been shown that using the relay can extend the coverage of wireless networks. In this thesis, we focus on the performance evaluation of such cooperative communication systems and their application to mobile multimedia. The thesis is divided into five parts. In particular, the first part proposes a hybrid decode-amplify-forward (HDAF) relaying protocol which can significantly improve the performance of cooperative communication systems compared to the two conventional schemes of decode-and-forward (DF) and amplify-and-forward (AF). It is interesting to see that the performance gain of HDAF over DF and AF strictly depends on the relative value of channel conditions between the two hops. The second part extends HDAF to the case of multiple relays. It is important to note that the gains are saturated as the number of relays tends to be a large value. This observation motivates us to use a small number of relays to reduce network overhead as well as system complexity while the obtained gains are still as much as in the large-number case. In the third part, we analyze the performance of DF relaying networks with best relay selection over Nakagami-m fading channels. Besides the diversity gain, we show that the spatial multiplexing gain can be achieved by cooperative communications. We analyze the performance of cooperative multiplexing systems in terms of symbol error rate and ergodic capacity over composite fading channels. Finally, in the fifth part, we exploit the benefit of both diversity and multiplexing gain by proposing an unequal error transmission scheme for mobile multimedia services using cooperative communications.

  • 249. Duong, Quang Trung
    et al.
    Alexandropoulos, George C.
    Tsiftsis, Theodoros A.
    Zepernick, Hans-Jürgen
    Outage probability of MIMO AF relay networks over Nakagami-m fading channels2010Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 46, nr 17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The outage probability (OP) of multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay networks using orthogonal space-time block code is investigated. In particular, a closed-form tight lower bound expression for the OP over independently but not necessarily identically distributed Nakagami-m fading channels is derived. Moreover, an asymptotic approximation for OP which reveals the coding and diversity gains is presented. The analytical expressions are validated by Monte-Carlo simulations.

  • 250. Duong, Quang Trung
    et al.
    Bao, Vo Nguyen Quoc
    Performance Analysis of Selection Decode-and-Forward Relay Networks2008Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 44, nr 20, s. 1206-07Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The performance of decode-and-forward (DF) cooperative networks with relay selection is presented. Specifically, we derive closed-form expressions for symbol error probability (SEP), bit error rate (BER), and achievable spectral efficiency of DF relay selection system in independent but not identically distributed (i.n.i.d.) Rayleigh fading channels taking into account the incapability of decoding the received signals' cyclic redundancy code (CRC) at the relays. We also perform Monte-Carlo simulations to validate the analysis.

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