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  • 101.
    Khan, Muhammad Gufran
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Sällberg, Benny
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Nordberg, Jörgen
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Tufvesson, Fredrik
    Claesson, Ingvar
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Non-Coherent Fourth-Order Detector for Impulse Radio Ultra Wideband Systems: Empirical Evaluation Using Channel Measurements2013Ingår i: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 68, nr 1, s. 27-46Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low-complex and low-power non-coherent energy detectors (EDs) are interesting for low data rate impulse radio (IR) ultra wideband (UWB) systems, but suffer from a loss in performance compared to coherent receivers. The performance of an ED also strongly depends on the integration interval (window size) of the integrator and the window position. This paper presents a non-coherent fourth-order detector (FD) which can discriminate between Gaussian noise signals and non-Gaussian IR-UWB signals by directly estimating the fourth-order moment of the received signal. The performance of the detectors is evaluated using realistic channels measured in a corridor, an office and a laboratory environment. The results show that bit-error-rate (BER) performance of the proposed FD receiver is slightly better than the ED in low signal-to-noise ratio (SNR) region and its performance improves as the SNR increases. In addition, BER of the FD receiver is less sensitive to overestimation of the integration interval making it relatively robust to variations of the channel delay spread. Finally, a criteria for the selection of integration time of the proposed detector is suggested.

  • 102. Kotte, Jaswini Reddy Swathi
    et al.
    Gannamaneni, Geetha Chowdary
    Talluri, Kalyan Chakravarthy
    Performance analysis of conventional CMA and RLS in single carrier LTE uplink systems2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In wireless communication, channel equalization is one of the most challenging tasks because the broadcast channels are often subjected to multipath fading and several bandwidth limitations. Our project is mainly concerned with the Single Carrier Long Term Evolution (SC-LTE) uplink system model and its performance analysis when Fractionally Spaced Constant Modulus Algorithm (FS-CMA) and Recursive Least Squares Algorithm (RLS) are implemented. FS-CMA (CMA (1, 2) and CMA (2, 2)) and RLS algorithms are used individually to eliminate noise caused by multipath fading and Additive White Gaussian Noise (AWGN) in the stationary channel. The performance of conventional FS-CMA and RLS algorithm are compared using Bit Error Rate (BER) vs. Signal to Noise Ratio (SNR), Convergence, Equalizer output, Peak to Average Power Ratio (PAPR) vs. SNR

  • 103. Kulesza, Wlodek
    Principles of Measurement System Modelling, Identification and Validation: Aspects of In-situ Real Time Self-tests2009Ingår i: Metrologia:dzis i jutro / [ed] Kicinski, W.; Swedrowski, L., Gdansk: Technical University of Gdansk , 2009, s. 21-30Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    The paper focuses on a design of in-situ real time system self-tests of a measurement system. The approach is based on principles of system modelling, pattern identification and validation with several methods presented. These involve several of the aspects of test signals and the design principles are illustrated in two case studies, one in the time domain and the second in the frequency domain. The paper also highlights the significance of rapid prototyping tools. The analysis can be useful as a methodological guide in designing smart sensors with an in-build self-test function.

  • 104. Kulesza, Wlodek
    Wireless Sensor Networks – Measurement, Telecommunication and Energy Approach2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    The wireless sensor networks, which development has begun by military applications, is applied in all human activities; in medicine for patience monitoring, in huge scale environmental monitoring e.g. to reduce the effects of disasters, and even many industrial and everyday applications. Nowadays the area of wireless sensor networks, WSNs is one of the emerging and fast growing fields in the scientific world. This has brought about developing low cost, low-power and multi-function sensor nodes. However, the major fact that sensor nodes run out of energy quickly has been an issue and many energy efficient routing protocols have been proposed to solve this problem and preserve the longevity of the network. This is the reason why routing techniques in wireless sensor network focus mainly on the accomplishment of power conservation. Most of the recent publications have shown many protocols mainly designed to minimize energy consumption in sensor networks. Fast development of wireless sensor networks can also be challenging for a designer, not only due to solution and structure complexities, but first of all due to demanding requirements. Case studies of WSN design are presented in the paper. A hierarchical routing technique which shows energy efficiency has been validated. The technique selects cluster head with highest residual energy in each communication round of transmission but it also takes into account, the shortest distance to the base station from the cluster heads. Simulation results show that hierarchical routing technique with different level of hierarchy prolongs the lifetime of the network compared to other clustering schemes and the residual energy mean value, after some communication rounds of simulation, increases significantly. The presented case study shows the advantages of hierarchical WSN structure. The advantages are validated by comparative studies. The analysis shows that energy efficiency of WSNs can be further improved. For instance the clusters formed dynamically on base of shortest distance to initial cluster head affects the network lifetime of WSN.

  • 105. Kumar, P.V.A.
    et al.
    Balakrishna, L.
    Prakash, Chetana
    Gangashetty, Suraykanath
    Bessel features for estimating number of speakers from multispeaker speech signals2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we explore Bessel features to determine the number of speakers from multispeaker speech signals collected simultaneously from a pair of spatially separated microphones. The arrival of the speech signals from speaker to microphones gives the time delays of given speaker. The time delays can be estimated by performing the cross-correlation to the band limited multispeaker signals collected at the two microphones. Signals are band limited using a finite number of Bessel coefficients. The computer simulation results demonstrate the proposed method is efficient compared to existing methods.

  • 106. Larsson, Martin
    Active Control of Noise in Ventilation Systems: Analysis and Experiments2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In many kinds of buildings, the ventilation system constitute a well known source of broadband noise. Traditionally, duct born noise is attenuated using passive resistive silencers which produce a high level of attenuation over a broad frequency range. However, they tend to become large and bulky if designed for low frequency attenuation. The active noise control (ANC) technique is known for its ability to produce high levels of attenuation in the low frequency range even with a relatively moderate sized ANC system. Accordingly, a combination of active- and passive techniques, i.e. the construction of a hybrid active/passive silencer, provides a duct silencer solution of manageable size which also covers the low frequency range. However, adequate levels of attenuation are not likely to be obtained if the installation of the ANC system is not designed to account for the physical factors that may degrade its performance. This thesis focuses on applying ANC in ventilation systems, with particular emphasis on analyzing the limiting effect of some of these physical factors on the controller, and installation design for the purpose of reducing the influence of them. The degrading factors of particular interest include: flow induced noise in the microphone signals, acoustic feedback between the control loudspeaker and reference microphone, and standing waves and higher order acoustic modes inside the ducts. With respect to installation design, focus is also placed upon industry requirements for the ANC system. This has led to a module based approach, in which the microphones and the loudspeaker are installed in separate modules based on standard duct parts. This thesis is comprised of six parts. The first and third parts analyze the influence of flow-induced noise on the adaptive digital controller theoretically, through simulations and experiments. The second part describes investigations of several microphone installations intended to reduce flow induced noise. Further, results of measurements conducted in an acoustic laboratory according to an ISO-standard are presented. The attenuation produced by the ANC system was approximately 15-25 dB between 50-315 Hz, even for airflow speeds up to 20 m/s. The fourth part focuses on the possibility of using a passive silencer in combination with ANC, to reduce acoustic feedback and standing waves, while the fifth part investigates the possibility of using a passive silencer to reduce standing waves in the duct when the ANC system is not installed near the duct outlet. In ducts of larger dimensions, higher order acoustic modes may be in the frequency range adequate for ANC. The final part presents initial investigations concerning the feasibility of dividing a duct of large dimension into two more narrow ducts to remove higher order acoustic modes in the ANC frequency range, and the feasibility of applying single-channel ANC in each duct.

  • 107. Larsson, Martin
    et al.
    Johansson, Sven
    Claesson, Ingvar
    Håkansson, Lars
    A Module Based Active Noise Control System for Ventilation Systems, Part I: Influence of Measurement Noise on the Performance and Convergence of the Filtered-x LMS Algorithm2009Ingår i: International Journal of Acoustics and Vibration, ISSN 1027-5851, Vol. 14, nr 4, s. 188-195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low noise level is an essential feature when installing ventilation systems today. To achieve attenuation over a broad frequency range, the passive silencers traditionally used to attenuate ventilation noise can be combined with an active noise control (ANC) system. To insure reliable operation and desirable levels of attenuation when applying ANC to duct noise, it is highly important to be able to suppress the contamination of the microphone signals due to the turbulent pressure fluctuations arising as the microphones are exposed to the airflow in the duct. This paper is the first in a series of two, that treats the problem of turbulence induced noise originating from the airflow inside the ducts. Part I is concerned with theoretical and experimental investigations of the influence of the turbulence induced noise on the adaptive algorithm in the ANC system. Part II is concerned with design and investigations of microphone installations for turbulence suppression and results concerning the performance of an ANC system with the different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO-standard. The attenuation achieved with ANC was approximately 15-25 dB between 50-315 Hz even for airflow speeds up to 20 m/s.

  • 108. Larsson, Martin
    et al.
    Johansson, Sven
    Claesson, Ingvar
    Håkansson, Lars
    A Module Based Active Noise Control System for Ventilation Systems, Part II: Performance Evaluation2009Ingår i: International Journal of Acoustics and Vibration, ISSN 1027-5851, Vol. 14, nr 4, s. 196-206Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To utilize the full noise attenuation potential of an active noise control (ANC) system applied to duct noise, it is important to be able to minimize the turbulence induced noise in the microphone signals. This is the second paper in a series of two, that treats the problem of turbulence induced noise originating from the airflow inside the ducts, when applying ANC to ducts. Part I contains theoretical and experimental investigations of the influence of the turbulence induced noise on the filtered-x LMS algorithm used in the ANC system. Part II (the present paper) is concerned with design and investigations of microphone installations which produces a sufficient amount of turbulence suppression while also meeting industry requirements. These requirements are, for example, that the microphone installations should be based on standard ventilation parts, and that they should be easily installed and maintained. Furthermore, results concerning the performance of an ANC system with different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO standard. The attenuation achieved with ANC was approximately 15-25 dB between 50-315 Hz even for airflow speeds up to 20 m/s.

  • 109. Larsson, Martin
    et al.
    Johansson, Sven
    Claesson, Ingvar
    Håkansson, Lars
    Influence of measurement noise on the performance and convergence of the filtered-x LMS algorithm; Theory and simulations2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In active noise control (ANC) applications the sensor signals feeding the controller may be contaminated by signal components not linearly related to the actual noise to be controlled, e.g. measurement noise. An example is the noise in the microphone signals generated by airflow turbulence when applying ANC to ducts. The measurement noise may significantly degrade the performance of an ANC system. This paper is concerned with theoretical investigations of the influence of measurement noise on the performance and convergence of the filtered-x LMS algorithm. Further, computer simulations have been performed to verify the theoretical results. In the theoretical investigations, the convergence of the filtered-x LMS algorithm is derived for different cases with measurement noise affecting the different sensor signals. These cases are compared to the ideal case with no measurement noise present at neither sensor signal. The results from both the theoretical investigations and the simulations show that measurement noise can, depending on the SNR of the sensor signals, degrade the performance of the filtered-x LMS algorithm regarding both the filter coefficients the algorithm converges to in mean, and the convergence rate of the algorithm.

  • 110. Larsson, Martin
    et al.
    Nilsson, Kristian
    Johansson, Sven
    Claesson, Ingvar
    Håkansson, Lars
    An Active Noise Control Approach for Attenuating Noise Above the Plane Wave Region in Ducts2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In a narrow duct, a relatively simple single-channel feedforward ANC system may be used to attenuate noise propagating as plane waves. However, for ducts with larger dimensions the cut-on frequencies for one or several higher-order acoustic modes may be within the frequency range where ANC is applied. In such situations it is generally necessary to use a multiplechannel feedforward ANC system with several secondary sources, error sensors, and perhaps reference sensors. Such a system has a significantly higher complexity than a single-channel ANC system. In this paper another approach is described. Instead of using a multiple-channel feedforward ANC system on a duct of large dimension, the idea is to divide the duct into several more narrow parallel ducts. In this way the complexity of the ANC system may be reduced. In the experiments conducted for this paper, a duct was divided into two more narrow ducts. The noise propagating in each duct was controlled by a feedforward ANC system based on the leaky filtered-x LMS algorithm, where different reference- and error microphone configurations were used. The different configurations were compared to a configuration where the noise in respective narrow duct was controlled using a basic single-channel ANC system per duct. The results preliminary show that high attenuation of low-frequency noise in a duct of large dimension may be achieved using this approach.

  • 111. Lu, Wen
    et al.
    Zhang, Zhen Yuan
    Liu, Ran
    Zhu, Hong Bing
    Design concept of a narrow-wideband antenna for spectrum sensing applications2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Design concept of a novel combined antenna for cognitive radio applications is proposed and numerically verified. The antenna is composed of a wideband circular monopole and a narrowband dipole. The impedance bandwidth of the wideband monopole antenna is from 4.25-10GHz. The narrowband dipole antenna's central frequency is 5.8GHz. The isolation between the two elements is higher than 50dB, which indicates that the two elements independently co-exist within a small printed circuit board (PCB). The design concept proposed in this paper should be useful to the design and realization of compact, planar antennas and antenna modules having spectrum sensing function.

  • 112. Maddala, Sainath
    et al.
    Bartunek, Josef Ström
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Nilsson, Mikael
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Implementation and evaluation of NIST biometric image software for fingerprint recognition2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fingerprints are rich in details which are in the form of discontinuities in ridges known as minutiae and are unique for each person. This paper describes implementation and evaluation of an existing fingerprint recognition system in MATLAB environment. The selected system is developed by National Institute of Standards and Technology (NIST) denoted as Biometric Image Software (NBIS). The NBIS source code is written in ANSI C programming language. To be able to evaluate the algorithm in MATLAB a C language MEX-files has been used. The NBIS support both minutiae extraction and minutiae matching functions that have been employed in the evaluation. The implemented system has been tested on a Fingerprint Verification Competition (FVC) database. The results are presented as Receiver Operating Characteristics (ROC) graphs

  • 113. Maddala, Sainath
    et al.
    Maheswar, Y
    Acoustic echo canceller for teleconferencing systems using Levinson algorithm2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In teleconferencing systems, there are disturbing effects of acoustic echo which hinder the quality of the sound from the loudspeakers. This paper presents an optimization technique to attenuate the acoustic echoes generated due to coupling between the microphone and the loudspeaker. An optimal filter is designed based on a least squares technique. It uses Levinson algorithm to equalize the acoustic channel in an iterative manner by calculating the correlation coefficients needed for updating the iterations, in order to minimize the echo effect. The method calculates the optimal solution directly with less data recorded. The performance was validated and compared with adaptive filtering technique using a real time signal from a conference room

  • 114.
    Maddala, Sainath
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Reddy, Sandeep Kumar
    A simulator for depicting and comparing adaptive algorithms in signal processing2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In real time applications signal characteristic and signal noise cannot be determined and predicted which makes very hard while designing digital filters for noise suppression. To outstrip these problem adaptive filters are preferable in which filter coefficients are designed based on the situation by using adaptive algorithms. In this paper a simulator containing adaptive algorithms(Least Mean Square(LMS), Normalized Least Mean Square(NLMS), Recursive Least Square(RLS) , Signed Least Mean Square(SLMS), Signed Normalized Least Mean Square(SNLMS)) using different applications was developed in MATLAB using Graphical User Interphone(GUI). Performance of all algorithms had been observed and some of the results obtained for different applications had been depicted by using real time noise corrupted voice signal. This proposed simulator helps the end user for depicting and comparing adaptive algorithms for real time applications. Pros and cons of each algorithm are observed manually without any motive of mathematical and paper results.

  • 115.
    Magnus, Berggren
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Nilsson, Kristian
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Håkansson, Lars
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Agnesson, Helen
    Hedsten, Stefan
    Noise measurements in incubators at neonatal intensive care unit2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    The purpose of this study was to investigate the noise properties and levels of common noise sources in a neonatal intensive care unit (NICU) and in particular inside and around an incubator. Many previous studies have been made on noise levels in NICU, frequently focusing on A-weighted sound levels. In this study it was not assumed that infant's hearing follows the same equal loudness curve as adults and hence instead of A-weighting, short time averaged sound spectra in the frequency range 20 Hz to 20 kHz was logged to identify the frequency distribution of specific noise generating events. It was seen that alarms and CPAP air-flow increased the noise level by up to 8 dB outside but was barely noticed inside when considering the un-weighted noise level. However, by analyzing individual frequencies, most events were noticeable inside the incubator. For instance, frequencies above 1 kHz were increased by 10 dB inside and 11 dB outside the incubator when CPAP was turned on. Opening and closing the incubator increased the un-weighted noise level by 8 dB inside and 7 dB outside.

  • 116. Marques, Maria
    et al.
    Viegas, Maria
    Costa-Lobo, Maria
    Fidalgo, André
    Alves, Gustavo
    Rocha, Joao
    Gustavsson, Ingvar
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    How Remote Labs Impact on Courses Outcomes: Various Practices Using VISIR2014Ingår i: IEEE Transactions on Education, ISSN 0018-9359 , Vol. 57, nr 3, s. 151-159Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As technology is increasingly being seen as a facilitator to learning, open remote laboratories are increasingly available and in widespread use around the world. They provide some advantages over traditional hands-on labs or simulations. This paper presents the results of integrating the open remote laboratory VISIR into several courses, in various contexts and using various methodologies. These integrations, all related to higher education engineering, were designed by teachers with different perspectives to achieve a range of learning outcomes. The degree to which these VISIR-related outcomes were accomplished is discussed. The results reflect the levels of student engagement and learning and of teacher involvement. From the analysis, a connection between these two aspects was traced, although only related to the user profiles. VISIR is shown to be always of benefit for more motivated students, but this benefit can be maximized under particular conditions and characteristics.

  • 117.
    Minhas, Tahir
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Shahid, Mohammad
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Rossholm, Andreas
    Lövström, Benny
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Zepernick, Hans-Jürgen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Fiedler, Markus
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Assessment of the Rating Performance of ITU-T Recommended Video Quality Metrics in the Context of Video Freezes2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Video streaming and multimedia applications are getting popular with the growth of networks. In real-time video streaming, video quality can be degraded due to network performance issues. Among other artifacts, freezing and frame dropping are factors that influence user experience. Service providers, operators, and researchers are interested to measure the Quality of Experience objectively. Different algorithms have been proposed and implemented in this regard. Some of them are in the recommendation list of the ITU Telecommunication Standardization Sector (ITU-T). In this paper, we study the effect of the freezing artifact on user experience and compare the mean opinion score (MOS) of these videos with the results of two algorithms, Perceptual Evaluation of Video Quality (PEVQ) and Temporal Quality Metric, both being part of ITU-T Recommendation J.247 Annex B and C, respectively. Another contribution of this paper is the investigation of the impact of different resolutions and frame rates on user experience.

  • 118. Mohammed, Abbas
    et al.
    Hult, Tommy
    OFDM-MIMO Applications for High Altitude Platform Communications2010Ingår i: Orthogonal Frequency Division Multiple Access Fundamentals and Applications / [ed] Jiang, Tao; Song, Lingyang; , Yan Zhang, Auerbach Publications, CRC Press , 2010Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    In this chapter we propose a combined Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output (MIMO), i.e. OFDM-MIMO system, in order to increase the capacity of High Altitude Platform (HAP) communication links. In the proposed system, the OFDM parameters and various compact MIMO antenna array configurations are investigated and their performance, in term of capacity, is analysed. In addition, since these special compact MIMO antenna array configurations depend on the array elements being positioned very closely together, the effect of mutual coupling and spatial correlation will also be analysed and taken into account when performing the simulation for this combined diversity system. Further, we will investigate the influence of the separation angle between the multiple relaying platforms on system performance, and determine the optimal separation angles that maximize the total capacity of the system.

  • 119. Mohammed, Abbas
    et al.
    Last, David
    Application of Novel Signal Processing Algorithms for the Detection and Minimization of Skywave Interfering Signals in Loran Receivers2011Ingår i: Applied Signal and Image Processing: Multidisciplinary Advancements / [ed] Qahwaji, Rami; Green, Roger; Hines, Evor, Hershey: IGI Global , 2011, s. 28-44Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Skywave interference commonly affects Loran receivers’ performance. Traditional skywave rejectionmethods that use fixed, worst-case, sample timing are far from optimal. This chapter reports on novel signal processing techniques for measuring in real-time the delay and strength of the varying skywave components of a Loran signal relative to the groundwave pulse. The merits and limitations of these techniques will be discussed. Their effectiveness will be assessed by theoretical analysis, computer simulations under a range of realistic conditions, and by testing using off-air signals. A prototype Loran system employing the proposed techniques is also presented. This work establishes a basis on which to design a Loran receiver capable of adjusting its sampling point adaptively to the optimal value in a constantly-changing skywave environment. Such receivers promise to improve significantly the accuracy and reliability of positioning under adverse operational conditions.

  • 120. Mohammed, Abbas
    et al.
    Mehmood, Asad
    Overview of Wireless Channel Models for UMTS and LTE2010Ingår i: Evolved Cellular Network Planning and Optimization for UMTS and LTE / [ed] Song, Lingyang; Shen, Jia, Auerbach Publications, CRC Press , 2010, s. 43-86Kapitel i bok, del av antologi (Refereegranskat)
  • 121. Mohammed, Abbas
    et al.
    Mehmood, Assad
    Pavlidou, F.N.
    Mohorcic, M.
    The Role of High-Altitude Platforms (HAPs) in the Global Wireless Connectivity2011Ingår i: Proceedings of the IEEE, ISSN 0018-9219, E-ISSN 1558-2256, Vol. 99, nr 11, s. 1939-1953Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Since 1990s, the investigations of aerospace communication segment have not only been concerned with satellites, but increasingly with lower altitude repeaters flying in the stratosphere. They are the so-called high-altitude platforms (HAPs) with important advantages with respect to satellites in terms of reduced cost of implementation, deployment, and launch. However, HAPs are characterized by a reduced coverage, as compared with satellites. Nevertheless, in recent literature, HAPs are not regarded as competitors of the satellite technology. On the contrary, the emphasis is on the effective and seamless integration among heterogeneous aerospace segments (GEO, LEO, and HAP) and aerospace segments with terrestrial wireless networks in order to globally extend the broadband wireless connectivity. This paper is focused on the role of HAPs in providing global connectivity in future communication systems and services. Potentialities, enabling technologies, and challenges are presented from the perspective of the integrated terrestrial/HAPs/satellite communications infrastructure.

  • 122. Mohammed, Abbas
    et al.
    Yang, Zhe
    Next Generation Broadband Services from High Altitude Platforms2010Ingår i: Fourth-Generation Wireless Networks: Applications and Innovations / [ed] Adibi, Sasan; Mobasher, Amin; Tofighbakhsh, Mostafa, IGI Global , 2010Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    In this chapter the authors investigate the possibility and performance of delivering broadband services from High Altitude Platforms (HAPs). In particular, the performance and coexistence techniques of providing worldwide interoperability for microwave access (WiMAX) from HAPs and terrestrial systems in the shard frequency band are investigated. The WiMAX standard is based on orthogonal frequency-division multiplexing (OFDM) and multiple-input and multiple-output (MIMO) technologies and has been regarded as one of the most promising 4G standards to lead 4G market and deliver broadband services globally. The authors show that it is possible to provide WiMAX services from an individual HAP system. The coexistence capability with the terrestrial WiMAX system is also examined. The simulation results show that it is effective to deliver WiMAX via HAPs and share the spectrum with terrestrial systems.

  • 123. Mohan, P. Ganga
    et al.
    Prakash, Chetana
    Gangashetty, Surayakanath
    Bessel transform for image resizing2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In many circumstances in image processing, image resizing is done, either to magnify or to reduce the size of a digital image. The spatial domain based resizing methods such as bilinear interpolation and bi-cubic interpolation are simple and work better for image size magnification. The main drawback in using them is that they are not suitable for image size reduction. In this paper, we propose a new method for image resizing based on Bessel transform (BT). The performance of image resizing based on BT is compared to that of spatial domain based resizing techniques, the results are viewed in terms of Peak Signal to Noise ratio (PSNR) and Mean Square Error (MSE). Experimental results confirm that the proposed method maintains better image quality when image size is enlarged and also when image size is reduced.

  • 124. Muhammad, Bilal
    et al.
    Mohammed, Abbas
    Performance evaluation of uplink closed loop power control for LTE system2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    Uplink power control is a key radio resource management feature in the 3GPP Long Term Evolution (LTE). In order to adapt to changes in the inter-cell interference situation or to correct power amplifier errors, closed-loop adjustments should be applied. In this paper the performance of closed loop power control combined with fractional path loss compensation factor is studied, and an optimal value for the path loss compensation factor is investigated. The closed loop power control with fractional path loss compensation factor is found to improve the system performance in terms of mean bit rate by 68% and utilizes the battery power more effectively.

  • 125. Muhammad, Bilal
    et al.
    Mohammed, Abbas
    Physical uplink shared channel (PUSCH) closed loop power control for 3G LTE2010Ingår i: Evolved Cellular Network Planning and Optimization for UMTS and LTE / [ed] Song, Lingyang; Shen, Jia, Auerbach Publications, CRC Press , 2010, s. 455-486Kapitel i bok, del av antologi (Refereegranskat)
  • 126. Muhammad, Bilal
    et al.
    Mohammed, Abbas
    Uplink closed loop power control for LTE system2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    The role of uplink power control is to suppress interference. Power control refers to set output power levels of transmitters, base stations in the downlink and User Equipment (UE) in the uplink. In this paper the performance of 3GPP Long Term Evolution (LTE) closed loop power control combined with fractional path loss compensation factor is evaluated by simulating the effects of open loop error, Transmit Power Control (TPC) command delay and power headroom reporting. Simulation results show that the closed loop power control with fractional path loss compensation factor is advantageous compared to closed loop power control with full path loss compensation. The closed loop power control with fractional path loss compensation factor is found to improve the system performance in terms of mean bit rate by 63%.

  • 127. Nafalski, Andrew
    et al.
    Machotka, Jan
    Nedic, Zorica
    Göl, Özdemir
    Scarino, A.
    Crichton, J.
    Gustavsson, Ingvar
    Ferreira, José M.M.
    Lowe, D.
    Murray, S.
    Collaborative Learning in Engineering Remote Laboratories2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper reports on practices in national and international on-line cooperation in engineering remote laboratories (RLs) to support student collaborative activities. A structured aid enables them, in addition to acquiring technical skills and knowledge, to develop intercultural communication skills and the global perspectives sought by their profession. The concept of a Community of Practice (CoP) is a central pedagogical consideration for collaborative learning and is discussed in the paper. After reviewing practices of others, an emphasis will be placed on a team-based laboratory environment of NetLab – a remote laboratory framework created at the University of South Australia (UniSA).

  • 128. Nilsson, Mikael
    et al.
    Gertsovich, Irina
    Bartunek, Josef Ström
    Mouth Open or Closed Decision for Frontal Face Images with Given Eye Locations2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Abstract—Determination of the open/closed state of a mouth is a desired feature considering the face ISO standard. In this paper a simple score is proposed for automatic mouth open/closed decision. Landmarks around the mouth are explored in order to calculate the score. Analysis of mouth location, scale and rotation introduced by nonreflective similarity transformations utilizing prior knowledge regarding the eye locations with the accompanied Jesorsky error is presented. Further, a novel system is proposed in which a search in the four dimensions; position, scale, rotation and shape variation is combined with a discriminative classifier in order to perform alignment of the landmarks. The system is evaluated on the XM2VTS and IMM face databases indicating the feasibility of the proposed system. The evaluation is presented utilizing a cumulative distribution of the mouth open/closed score error.

  • 129. Odeh, S.
    et al.
    Alves, G.R.
    Anabtawi, M.
    Jazi, M.
    Arekat, M.
    Gustavsson, Ingvar
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Experiences with Deploying VISIR at Al-Quds University in Jerusalem2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Engineering and science labs play a central role in illustrating concepts and principles as well as improving technical skills. Through introducing of remote labs, it will be possible to share devices, equipment and instrumentations with lots of universities. Moreover, they relax time and space constraints and are capable to be adapted to pace of each student if there was insufficient time in lab; this contribution reports the experiences at Al-Quds University in Jerusalem in Palestine with deploying VISIR, and represents the results of an evaluation for its appropriateness as a complementary asset to traditional labs. The questionnaire for the interaction between students and VISIR includes survey questions with the goal to measure the evaluation criteria: usefulness and satisfaction, sense of reality/immersion and usability.

  • 130. Oloumi, Daniel
    et al.
    Mohammadirad, Mohammad
    Naraghi, Reza Jokar
    Gain compensation of a printed log periodic dipole array antenna by cutting-away the dielectric between radiating elements2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper introduces a simple technique to compensate the lost gain due to the dielectric loss of the printed log periodic dipole array (PLPDA) antenna. First, a simple Printed LPDA is designed then by removing the dielectric between radiating elements, the PLPDA is changed into Cut PLPDA (CPLPDA). This change causes to compensate antenna gain by 1 dB approximately. Moreover, a simultaneously weight reduction of more than half is likely to happen. Observing the characteristics of both antennas shows that main antenna properties such as radiation pattern, and return loss are maintained during this modification. The proposed structures are simulated by CST Microwave Studio software and are fabricated on both sides of FR4 substrate with =4.5 and 2.4mm thickness. At the end, the simulated results are confirmed by the measured results with excellent agreements.

  • 131. Oloumi, Daniel
    et al.
    Mousavi, Pedram
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Elliott, Duncan
    A Modified TEM Horn Antenna Customized for Oil Well Monitoring Applications2013Ingår i: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X , Vol. 616, nr 12, s. 5902-5909Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A TEM horn antenna with modified radiation pattern customized for oil well monitoring application is presented in this paper. The antenna is designed to operate in an oil saturated medium in the frequency range between 1.4 to 11 GHz. A complete design procedure for the proposed TEM horn antenna with a method to modify the radiation pattern is introduced here. The modification is conducted using non-uniform expansion of the antenna flares. Applying this technique eliminates ripples in the antenna’s main-lobe radiation pattern at higher frequencies, a problem which exists for conventional TEM horn antennas. The design coefficients which control the flare openings are optimized using CST Microwave Studio to achieve smooth main-beam radiation patterns while maintaining return loss more than 10dB. Simulations are performed both in oil and free space. Free space simulations are done to provide a valid reference for antenna radiation pattern measurement as radiation pattern cannot be measured in oil. Simulation results are followed by the measurement results with a very good agreement. The fabricated dimensions of the antenna including balun section are limited to 89.2×49.2×78.2 mm. The designed antenna is utilized as a part of an ultra-wideband radar system for oil well monitoring.

  • 132. Oloumi, Daniel
    et al.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Elliott, Duncon
    Mousavi, Pedram
    A TEM Horn Antenna with Non-uniform Expansion for Oil Well Monitoring2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    A TEM horn antenna with non-uniform expansion to modify the radiation characteristics, operating from 1.4 to 11 GHz in oil medium is introduced. Main lobe radiation pattern ripple at higher frequencies which are the problem of conventional TEM horn antenna is suppressed. The expansions coefficient is tuned using CST Microwave Studio to achieve good return loss (less than 10dB) and radiation pattern. The horn is utilized as a part of an ultra-wideband radar system to monitor oil well with no metal casing.

  • 133.
    Orgunmat, Kaan
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Heatapp - Remote TemperatureController Project: Degree Project in Electrical Engineering2015Självständigt arbete på grundnivå (kandidatexamen), 180 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The project is a part of series of hardware and software challenges merging in one. It is fundamentally an application to monitor the temperature changes and get notications based on those changes. Also through this application an electrical device that is connected to an outlet will be controlled remotely. It is a feature for the users that do not have access to certain type of devices and want to turn on/off them.This project is built by using a digital remote controller and an outlet (REMOTE CONTROLLEDOUTLETS 310000) that a potential heating system is connected to. The remote controller is controlled via Arduino. On Arduino there are two relays (PRMA2A12B) that turns the remote control on and off based on the input signal that is sent. There is also a temperature sensor connected to the Arduino. The readings from the temperature sensor are sent to a web server and stored there in order to track the changes. On the web interface, other than reading and tracking temperature changes, it is possible to turn on/off an outlet with an integrated button.

  • 134. Ostlin, Erik
    et al.
    Zepernick, Hans-Jürgen
    Suzuki, Hajime
    Macrocell Path Loss Prediction Using Artificial Neural Networks2010Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 59, nr 6, s. 2735-2747Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents and evaluates artificial neural network models used for macrocell path loss prediction. Measurement data obtained by utilising the IS-95 pilot signal from a commercial code division multiple access mobile network in rural Australia is used to train and evaluate the models. A simple neuron model and feed-forward networks with different number of hidden layers and neurons are evaluated regarding their training time, prediction accuracy, and generalisation properties. Also, different backpropagation training algorithms, such as gradient descent and LevenbergMarquardt, are evaluated. The artificial neural network inputs are chosen to be distance to base station, parameters easily obtained from terrain path profiles, land usage and vegetation type and density near the receiving antenna. The path loss prediction results obtained by using the artificial neural network models are evaluated against different versions of the semi-terrain based propagation model Recommendation ITU-R P.1546 and the OkumuraHata model. The statistical analysis shows that a non-complex artificial neural network model performs very well compared to traditional propagation models in regards to prediction accuracy, complexity and prediction time. The average ANN prediction results were: 1) maximum error: 22 dB, 2) mean error: 0 dB and 3) standard deviation: 7 dB. A multi-layered feed-forward network trained using the standard backpropagation algorithm was compared with a neuron model trained using the LevenbergMarquardt algorithm. It was found that the training time decreases from 150 , 000 to 10 iterations whilst the prediction accuracy is maintained.

  • 135.
    Pettersson, Mats
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Sjögren, Thomas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Vu, Viet
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    An Evaluation on Moving Target Parameter Estimation using Synthetic Aperture Radar Systems2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    One important application of Synthetic Aperture Radars (SAR) is positioning of targets with high accuracy in both azimuth and range. If the target is moving and a multi-channel SAR system is used also the speed components in azimuth and range can be found with a high accuracy. In this paper we propose a method to estimate the accuracy of such a multichannel SAR system. The method is based on the Cramér-Rao Lower Bound (CRLB). To exemplify the method the variance of parameter estimates by a single channel UHF UWB SAR system is found.

  • 136. Salih, Sami
    et al.
    Al-Refai, Ali
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Suliman, Mamoun
    Mohammed, Abbas
    Implementation of adaptive modulation for broadband wireless access networks using cognitive radio approaches2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Broadband Wireless Access (BWA) has become the best way to meet escalating business demand for rapid Internet connection and integrated 'triple play' services. In addition, not only for topographic but also for technological limitations, alternative wireless solutions have been found. These systems are designed based on Cognitive Radio (CR) approaches, which can adjust its operation according to the environment and technical variations. This tracking feature allows the communication system to deliver the Best Ever, compare to Best Effort, services to the users. In this paper, an implementation of a cognitive engine for adaptive modulation and coding (AMC) is presented. This engine will track the radio channel variations in terms of SNR and be able to select a suitable modulation order among predefined Modulation and Coding Schemes (MCS) to maintain the specified BER by the user requirements.

  • 137. Salih, Sami
    et al.
    Suliman, Mamoun
    Mohammed, Abbas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    A novel spectrum sensing scheduler algorithm for Cognitive Radio Networks2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cognitive Radios' is recognized as a novel approach to improve the utilization of a precious wireless communication natural resource; the radio frequency spectrum. Historically, telecom regulators assigned fixed spectrum bands to the licensee wireless network operators, this spectrum management approach is guarantee interference free environment, except of some configurations faults or illegal usage. However, with the increasing demand for more bandwidth in the finite radio spectrum, the concept of secondary operator's was emerged, but with emphases to not influence licensed operators. Consequently, Cognitive Radio Networks (CRN) architecture enters the market as an intelligent solution to these issues, with concentration on the spectrum sensing procedures to achieve the regulatory constraint. The most successful sensing algorithms is those applying cooperation and scheduling to have better scanning information, however those algorithms are developed base on the primary network activities which is good in terms of reducing the expected interference, but it lay more computational loads on the CRN. In this paper, a novel sensing scheduler algorithm is proposed, the idea is to utilize the CRN by fairly distribute the sensing task among the sensors, then utilizing the radio spectrum shared with the primary networks.

  • 138. Schenkman, Bo
    et al.
    Nilsson, Mats E.
    Grbic, Nedelko
    Human echolocation using click trains and continuous noise2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Blind people may detect objects from the information in reflected sounds, echolocation. Detection as a function of the number of clicks compared to a continuous noise was tested by presenting clicks of 5 ms with rates from 1 to 64 clicks during a 500 ms period and a 500-ms continuous white noise. The sounds were recorded in an ordinary room through an artificial binaural head. The reflecting object was an aluminum disk, diameter 0.5 m, at distances of 1 and 1.5 m. These sounds were later presented to 3 blind and 16 sighted participants in a laboratory using a 2AFC methodology. The task was to detect which of the two sounds that contained a reflecting object. Feedback was provided. The blind participants had a higher detection than the sighted, but there were also differences among the blind. These results are put in relation to physical features such as the autocorrelation function and spectral variations.

  • 139.
    Schüldt, Christian
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Low-Complexity Algorithms for Echo Cancellation in Audio Conferencing Systems2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Ever since the birth of the telephony system, the problem with echoes, arising from impedance mismatch in 2/4-wire hybrids, or acoustic echoes where a loudspeaker signal is picked up by a closely located microphone, has been ever present. The removal of these echoes is crucial in order to achieve an acceptable audio quality for conversation. Today, the perhaps most common way for echo removal is through cancellation, where an adaptive filter is used to produce an estimated replica of the echo which is then subtracted from the echo-infested signal. Echo cancellation in practice requires extensive control of the filter adaptation process in order to obtain as rapid convergence as possible while also achieving robustness towards disturbances. Moreover, despite the rapid advancement in the computational capabilities of modern digital signal processors there is a constant demand for low-complexity solutions that can be implemented using low power and low cost hardware. This thesis presents low-complexity solutions for echo cancellation related to both the actual filter adaptation process itself as well as for controlling the adaptation process in order to obtain a robust system. Extensive simulations and evaluations using real world recorded signals are used to demonstrate the performance of the proposed solutions.

  • 140.
    Schüldt, Christian
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Lindström, Fredric
    Claesson, Ingvar
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    A Delay-Based Double-Talk Detector2012Ingår i: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, Vol. 20, nr 6, s. 1725-1733Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    When an adaptive filter is used for echo cancellation, it is essential to prevent the filter from diverging in situations when the echo signal is contaminated with near-end disturbance, i.e. during double-talk. This paper presents an extension of a previously proposed double-talk detector for improved performance. It is shown that the computational complexity of the proposed detector is lower than that of the well-used normalized cross correlation (NCC) double-talk detector, at the cost of performance. Further, it is shown that there can be a significant performance difference, in terms of detecting double-talk, between having a fixed echo cancellation filter, which is a common strategy in objective evaluation techniques, and an adaptive filter, which is more close to realistic conditions.

  • 141. Schüldt, Christian
    et al.
    Lindström, Fredric
    Claesson, Ingvar
    An Improved Deviation Measure for Two-Path Echo Cancellation2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Parallel adaptive filters have been proposed for echo cancellation to solve the dead-lock problem, occurring when the echo is detected as near-end speech after a severe echo-path change; causing the updating of the adaptive filter to halt. To control the parallel filters and monitor their performance, estimates of the filter deviation (i.e. the squared norm of the filter mismatch vector) are typically used. This paper presents a modification of a filter mismatch estimator. The proposed modification requires slightly more computational resources than the original measure, but provides a significantn improvement in terms of robustness during double-talk. This is shown both analytically and through simulations.

  • 142. Schüldt, Christian
    et al.
    Lindström, Fredric
    Claesson, Ingvar
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Robust low-complexity transfer logic for two-path echo cancellation2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    A well used approach for echo cancellation is the two-path method, where two adaptive filters in parallel are utilized. Typically, one filter is continuously updated, and when this filter is considered better adjusted to the echo-path than the other filter, the coefficients of the better adjusted filter is transferred to the other filter. When this transfer should occur is controlled by the transfer logic. This paper proposes transfer logic that is both more robust and more simple to tune, owing to fewer parameters, than the conventional approach. Extensive simulations show the advantages of the proposed method.

  • 143. Shahid, Muhammad
    et al.
    Ishaq, Rizwan
    Sällberg, Benny
    Grbic, Nedelko
    Lövström, Benny
    Claesson, Ingvar
    Modulation Domain Adaptive Gain Equalizer for Speech Enhancement2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper evaluates speech enhancement by filtering in the modulation frequency domain, as an alternative to filtering in conventional frequency domain. Adaptive Gain Equalizer (AGE) is a commonly used single-channel speech enhancement algorithm. A recently introduced class of signal transformations called modulation transform has successfully made its place alongside classical time/frequency representations. This paper presents an implementation of AGE within modulation system, for the purpose of enhancing the speech signal. The successful implementation of the proposed system has been validated with various performance measurements, i.e., Signal to Noise Ratio Improvement (SNRI), Mean Opinion Score (MOS) and Spectral Distortion (SD). A spectrogram analysis is also presented to further substantiate the performance of this work

  • 144. Shahid, Muhammad
    et al.
    Rossholm, Andreas
    Lövström, Benny
    A High Quality Adjustable Complexity Motion Estimation Algorithm For Video Encoders2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the video encoding process, the motion estimation usually consumes a large part of the encoder computations. This paper presents motion estimation techniques, targeted mainly for MPEG-4 video encoding but also applicable for other video codecs e.g. H.264. A high quality adaptive algorithm with adjustable complexity, based on partially blind prediction for motion estimation, is proposed.The computational complexity of motion estimation is reduced with minor loss in the video quality. In the paper, the quality metrics PSNR, BD PSNR and PEVQ are used, and the possible trade off between complexity and visual quality is studied.

  • 145.
    Shahid, Muhammad
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Rossholm, Andreas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Lövström, Benny
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    A No-Reference Machine Learning Based Video Quality Predictor2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    The growing need of quick and online estimation of video quality necessitates the study of new frontiers in the area of no-reference visual quality assessment. Bitstream-layer model based video quality predictors use certain visual quality relevant features from the encoded video bitstream to estimate the quality. Contemporary techniques vary in the number and nature of features employed and the use of prediction model. This paper proposes a prediction model with a concise set of bitstream based features and a machine learning based quality predictor. Several full reference quality metrics are predicted using the proposed model with reasonably good levels of accuracy, monotonicity and consistency.

  • 146. Shahid, Muhammad
    et al.
    Rossholm, Andreas
    Lövström, Benny
    A Reduced Complexity No-Reference Artificial Neural Network Based Video Quality Predictor2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    There is a growing need for robust methods for reference free perceptual quality measurements due to the increasing use of video in hand-held multimedia devices. These methods are supposed to consider pertinent artifacts introduced by the compression algorithm selected for source coding. This paper proposes a model that uses readily available encoder parameters as input to an artificial neural network to predict objective quality metrics for compressed video without using any reference and without need for decoding. The results verify its robustness for prediction of objective quality metrics in general and for PEVQ and PSNR in particular. The paper also focuses on reducing the complexity of the neural network.

  • 147.
    Shahid, Muhammad
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Singam, Amitesh Kumar
    Rossholm, Andreas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Lövstrom, Benny
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Subjective Quality Assessment of H.264/AVC Encoded Low Resolution Videos2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Advancements in the video processing area have been proliferated by services that require low delay. Such services involve applications being offered at various temporal and spatial resolutions. It necessitates to study the impacts of related video coding conditions upon perceptual quality. But most of studies concerned with quality assessment of videos affected by coding distortions lack in variety of spatio-temporal resolutions. This paper presents a work done on quality assessment of videos encoded by state-of-the-art H.264/AVC standard at different bitrates and frame rates. Overall, 120 test scenarios for video sequences having different spatial and temporal spectral information were studied. The used coded bistreams in this work and the corresponding subjective assessment scores have been made public for the research community to facilitate further studies

  • 148. Sjögren, Thomas
    Development and evaluation of SAR algorithms for image formation and speed estimation in wideband SAR2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Remote sensing and surveillance are the main application areas for radar in general and synthetic aperture (SAR) radar in particular. Since the first radar system built by Hülsmeyer in 1904, radar has developed so that it is now able to create images from a large distance. In addition to this, the invention of synthetic aperture radar has enabled the ability to create images with high resolution. In this thesis, SAR systems capable of very high resolution imaging are considered, and data from such a system, namely CARABAS-II, is used. The higher the resolution of the system, the better the ability to extract information. The work presented in this thesis can be divided into two separate fields. The first and main area is speed estimation and the refocusing of moving targets in SAR imagery. The second area is related to SAR processing. In Part I of this thesis, a theoretical expression for the phase of a moving object in a SAR image is derived. Based on this expression, an estimator of relative speed is proposed. The estimator was tested in simulation and on CARABAS-II data, using a boat as a moving target. The results with regard to the focusing ability were satisfactory. In Part II, a comparison between two high resolution SAR processing algorithms, namely the polar and the subimage version of fast factorized back projection, is made. The comparison takes into account the difference in ability of obtaining very high quality images and gives a phase error analysis. In Part III, the effect of clutter statistics on the estimator is investigated. The sensitivity of the estimator to surrounding stationary targets (coherent clutter) and to thermal noise is examined. The results indicate that a target signal power of approximately 5dB above clutter (peak energy) or noise (average power) gives good results only using one iteration. Part IV is a continuation of Part I and III. In this part, a refocusing approach based on a SAR image is also developed and used. The central part of this refocusing approach is the derivation of a new refocusing equation. The results show that an image with many moving targets that have different normalized relative speeds can be focused.

  • 149.
    Sjögren, Thomas
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Synthetic Aperture Radar Signal and Image Processing for Moving Target Indication and Side Lobe Suppression2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The thesis summarizes a selection of my research within Synthetic Aperture Radar (SAR). Mainly the research is aimed at applying and developing signal processing methods to single channel and multi channel SAR for wideband systems. SAR systems can generate images looking very similar to optical pictures, i.e. photos, and sometimes with much finer resolution compared to optical systems orbiting Earth. SAR has also for instance been used to obtain fine resolution images of the moon, Venus and the satellites of Saturn. Other applications for SAR has is to detect changes in ice sheets and deforestation. In this thesis, SAR systems capable of very high resolution imaging are con- sidered, and data from such systems, namely the VHF system CARABAS-II and the UHF system LORA, is used. High resolution imaging in this thesis refers to high resolution with regard to wavelength, this independent of system operating frequency. Two of the topics in this thesis are related to detection and parameter estimation of moving objects in SAR, the first one using CARABAS-II data and the second with LORA data. On the CARABAS-II data, a speed estimation and refocusing method is introduced and applied to single channel CARABAS-II data. The results show good estimation accuracy as well as good ability to focus the object and suppress forest clutter by ap- plying the refocusing algorithm. The results on LORA data are satisfactory especially with regard to forest clutter suppression. The ability to detect and focus images of ships allow for surveillance of coastal areas and help in rescue of ships lost at sea. Detection and location of cars and trucks allow for traffic monitoring to obtain statistics of how many cars travel the roads and their speed. In the thesis, two more important aspects for SAR processing is presented. One paper presents windowing of UWB SAR images. A strong object such as a power line in a SAR image cause ringing on both sides of the power line. This ringing can cause a small house to be covered by these so called side lobes. Applying a window can make these side lobes in the image much suppressed, however if windowing too much, the power line will smear over the image, covering the small house. The last topic in the thesis concern with theoretical limits for measurement accuracy of parameters for a moving object in a SAR image. These parameters are position, velocity, radar cross section and phase. The theoretical expressions are verified using simulations for a single channel system for estimation accuracy of target speed and relative speed.

  • 150.
    Sjögren, Thomas
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Vu, Viet
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Pettersson, Mats
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Wang, Feng
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Murdin, Daniel
    Gustavsson, Anders
    Ulander, Lars
    Forest Clutter Suppression for Moving Target Detection in UHF Dual Channel SAR2013Konferensbidrag (Refereegranskat)
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