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  • 51. Engelke, Ulrich
    et al.
    Pepion, Romuald
    Callet, Patrick Le
    Zepernick, Hans-Jürgen
    Linking Distortion Perception and Visual Saliency in H.264/AVC Coded Video Containing Packet Loss2010Conference paper (Refereed)
    Abstract [en]

    In this paper, distortions caused by packet loss during video transmission are evaluated with respect to their perceived annoyance. In this respect, the impact of visual saliency on the level of annoyance is of particular interest, as regions and objects in a video frame are typically not of equal importance to the viewer. For this purpose, gaze patterns from a task free eye tracking experiment were utilised to identify salient regions in a number of videos. Packet loss was then introduced into the bit stream such as that the corresponding distortions appear either in a salient region or in a non-salient region. A subjective experiment was then conducted in which human observers rated the annoyance of the distortions in the videos. The outcomes show a strong tendency that distortions in a salient region are indeed perceived as much more annoying as compared to distortions in the non-salient region. The saliency of the distorted image content was further found to have a larger impact on the perceived annoyance as compared to the distortion duration. The findings of this work are considered to be of great use to improve prediction performance of video quality metrics in the context of transmission errors.

  • 52. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    A Framework for Optimal Region of Interest-based Quality Assessment in Wireless Imaging2010In: Journal of Electronic Imaging (JEI), ISSN 1017-9909, E-ISSN 1560-229X, Vol. 19, no 1Article in journal (Refereed)
    Abstract [en]

    Images usually exhibit regions that particularly attract the viewer's attention. These regions are typically referred to as regions-of-interest (ROI) and the underlying phenomenon in the human visual system is known as visual attention (VA). In the context of image quality one may expect that distortions occuring in the ROI are perceived as being more annoying, as compared to distortions in the background. However, VA is only seldom taken into account in existing image quality metrics. In this paper, we thus provide a VA framework to extend existing image quality metrics with a simple VA model. The performance of the framework is evaluated on three contemporary image quality metrics. We further consider the context of wireless imaging where a broad range of artifacts can be observed. To facilitate the VA based metric design, we conducted subjective experiments to both obtain a ground truth for the subjective quality of a set of test images and to identify ROI in the corresponding reference images. A methodology is further discussed to optimize the VA metrics with respect to quality prediction accuracy and generalization ability. It is shown that the quality prediction performance of the three considered metrics can be significantly improved by deploying the proposed framework.

  • 53. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    Framework for Optimal Region of Interest-based Quality Assessment in Wireless Imaging2010In: Journal of Electronic Imaging (JEI), ISSN 1017-9909, E-ISSN 1560-229X, Vol. 19, no 1Article in journal (Refereed)
    Abstract [en]

    Images usually exhibit regions that particularly attract the viewer's attention. These regions are typically referred to as regions-of-interest (ROI) and the underlying phenomenon in the human visual system is known as visual attention (VA). In the context of image quality one may expect that distortions occuring in the ROI are perceived as being more annoying, as compared to distortions in the background. However, VA is only seldom taken into account in existing image quality metrics. In this paper, we thus provide a VA framework to extend existing image quality metrics with a simple VA model. The performance of the framework is evaluated on three contemporary image quality metrics. We further consider the context of wireless imaging where a broad range of artifacts can be observed. To facilitate the VA based metric design, we conducted subjective experiments to both obtain a ground truth for the subjective quality of a set of test images and to identify ROI in the corresponding reference images. A methodology is further discussed to optimize the VA metrics with respect to quality prediction accuracy and generalization ability. It is shown that the quality prediction performance of the three considered metrics can be significantly improved by deploying the proposed framework.

  • 54.
    Engelke, Ulrich
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Psychophysical Assessment of Perceived Interest in Natural Images: The ROI-D Database2011Conference paper (Refereed)
    Abstract [en]

    We introduce a novel region-of-interest (ROI) database for natural image content, the ROI-D database. The database consists of ROI maps created from manual selections obtained in a psychophysical experiment with 20 participants. The presented stimuli were 42 photographic images taken from 3 publicly available image quality databases. In addition to the ROI selections, dominance ratings were recorded that provide further insight into the interest of the selected ROI in relation to the background. In this paper, the experiment is described, the resulting ROI database is analysed, and possible applications of the database are discussed. The ROI-D database is made freely available to the image processing research community.

  • 55. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    Kusuma, Tubagus Maulana
    Subjective Quality Assessment for Wireless Image Communication: The Wireless Imaging Quality Database2010Conference paper (Refereed)
    Abstract [en]

    Mean opinion scores (MOS) obtained in image quality experiments are a key component in the transition from subjective to objective measures of perceived quality. In this respect, MOS are widely used to validate objective quality prediction models. To facilitate comparison between models from different laboratories it is desirable to have publicly available image quality databases. Several databases were made available in recent years. In this paper, we introduce the Wireless Imaging Quality (WIQ) database which, unlike any of the previous databases, takes into account the complex nature of a wireless communications link. The database is thus considered as a valuable complement to the existing databases. The distortion model, the test images, and two quality experiments that we conducted are explained in this paper. A number of contemporary objective quality metrics are tested for their quality prediction performance on the database. The WIQ database including test images and MOS is made freely available to the research community.

  • 56. Engelke, Ulrich
    et al.
    Zepernick, Hans-Jürgen
    Maeder, Anthony
    Visual Fixation Patterns in Subjective Quality Assessment: The Relative Impact of Image Content and Structural Distortions2010Conference paper (Refereed)
    Abstract [en]

    The viewing behaviour of human observers during image quality assessment is analysed. In this respect, the relative impact of image content and structural distortions is of particular interest. Two subjective experiments were conducted as a basis for analysis; a region-of-interest (ROI) experiment and an eye tracking experiment under quality assessment task. A correlation analysis and a receiver operating characteristics analysis reveal, that quality assessment takes place mainly within the ROI, indicating a higher impact of the content as compared to the distortions. This seems to be only contradicted by very strong and localised distortions outside the ROI.

  • 57.
    Faisal, Mohammed
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Uddin, Jia
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Shil, Shimul
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Performance of VoIP networks using MPLS traffic engineering2012In: Advanced Materials Research, Trans Tech Publications , 2012, Vol. 457-458, p. 927-930Conference paper (Refereed)
    Abstract [en]

    The implementation of Voice over Internet Protocol (VoIP) technology is on the increase because of its ability to enhance operating efficiency and reduce infrastructure cost. Voice and data packets traverse over IP networks with fixed maximum capacity. But susceptibility to traffic congestion which results in delay and packet losses is still a major challenge of VoIP technology. Multiprotocol Label Switching Protocol (MPLS) with Traffic Engineering (TE) is an approved standard technology that has the capabilities to minimize network congestion and improve network performance by reducing delay and packet loss to yield a higher throughput. In this paper, we investigate how MPLS Traffic Engineering can be implemented to reduce traffic congestion on VoIP networks.

  • 58. Fidalgo, André
    et al.
    Alves, Gustavo
    Marques, Maria A.
    Viegas, Maria C.
    Costa-Lobo, Maria C.
    Hernández, Unai
    García-Zubia, Javier
    Gustavsson, Ingvar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Using remote labs to serve different teacher's needs: A case study with VISIR and RemotElectLab2012Conference paper (Refereed)
    Abstract [en]

    Remote Laboratories are an emergent technological and pedagogical tool at all education levels, and their widespread use is an important part of their own improvement and evolution. This paper describes several issues encountered on laboratorial classes, on higher education courses, when using remote laboratories based on PXI systems, either using the VISIR system or an alternate in-house solution. Three main issues are presented and explained, all reported by teachers that gave support to students use of remote laboratories. The first issue deals with the need to allow students to select the actual place where an ammeter is to be inserted on electric circuits, even incorrectly, therefore emulating real world difficulties. The second one deals with problems with timing when several measurements are required at short intervals, as in the discharge cycle of a capacitor. And the last issue deals with the use of a multimeter in DC mode when reading AC values, a use that collides with the lab settings. All scenarios are presented and discussed including the solution found for each case. The conclusion derived from the described work is that the remote laboratories area is an expanding field, where practical use leads to improvement and evolution of the available solutions, requiring a strict cooperation and information sharing between all actors, i.e. developers, teachers and students.

  • 59.
    Garcia-Zubia, Javier
    et al.
    Univ Deusto, ESP.
    Cuadros, Jordi
    Univ Ramon Llull, ESP.
    Romero, Susana
    Univ Deusto, ESP.
    Hernandez-Jayo, Unai
    Univ Deusto, ESP.
    Orduna, Pablo
    Univ Deusto, ESP.
    Guenaga, Mariluz
    Univ Deusto, ESP.
    Gonzalez-Sabate, Lucinio
    Univ Ramon Llull, ESP.
    Gustavsson, Ingvar
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing. Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering. Blekinge Institute of Technology, Department of Signal Processing.
    Empirical Analysis of the Use of the VISIR Remote Lab in Teaching Analog Electronics2017In: IEEE Transactions on Education, ISSN 0018-9359, E-ISSN 1557-9638, Vol. 60, no 2, p. 149-156Article in journal (Refereed)
    Abstract [en]

    Remote laboratories give students the opportunity of experimenting in STEM by using the Internet to control and measure an experimental setting. Remote laboratories are increasingly used in the classroom to complement, or substitute for, hands-on laboratories, so it is important to know its learning value. While many authors approach this question through qualitative analyses, this paper reports a replicated quantitative study that evaluates the teaching performance of one of these resources, the virtual instrument systems in reality (VISIR) remote laboratory. VISIR, described here, is the most popular remote laboratory for basic analog electronics. This paper hypothesizes that use of a remote laboratory has a positive effect on students' learning process. This report analyzes the effect of the use of VISIR in five different groups of students from two different academic years (2013-2014 and 2014-2015), with three teachers and at two educational levels. The empirical experience focuses on Ohm's Law. The results obtained are reported using a pretest and post-test design. The tests were carefully designed and analyzed, and their reliability and validity were assessed. The analysis of knowledge test question results shows that the post-test scores are higher that the pretest. The difference is significant according to Wilcoxon test (p < 0.001), and produces a Cohen effect size of 1.0. The VISIR remote laboratory's positive effect on students' learning processes indicates that remote laboratories can produce a positive effect in students' learning if an appropriate activity is used.

  • 60.
    Gothberg, Mattias
    et al.
    Atlas Copco, SWE.
    Enblom, Samuel
    Atlas Copco, SWE.
    Rantakokko, Renny
    Atlas Copco, SWE.
    Håkansson, Lars
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing. Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering. Blekinge Institute of Technology, Department of Signal Processing. Blekinge Institute of Technology, School of Engineering, Department of Signal Processing. Blekinge Inst Technol, Dept Appl Signal Proc, Karlskrona, Sweden..
    EFFICIENT MULTI CHANNEL VIBRATION MEASUREMENT-SYSTEMATIC APPROACH2016In: PROCEEDINGS OF THE 23RD INTERNATIONAL CONGRESS ON SOUND AND VIBRATION: FROM ANCIENT TO MODERN ACOUSTICS / [ed] Vogiatzis, K Kouroussis, G Crocker, M Pawelczyk, M, INT INST ACOUSTICS & VIBRATION , 2016Conference paper (Refereed)
    Abstract [en]

    In Atlas Copco a wide range of machines is produced from surface drill rigs, exploration drill rigs, underground drill rigs both for mining and construction to underground loader and haulers for mines. Recently new rock excavation methods have developed in cooperation with large mining companies. The machines are produced in low volume and often customized although having a modular approach. Time for validation is limited due to machines available for test are planned for customer delivery. It is on regular basis needed to validate and investigate vibrational behavior of installations as power packs and drivelines to get loads for simulation, identify resonances, operational deflection shapes, and vibration and stress levels for life length estimations under operational conditions. The time for a 40-180 Channel measurement is now down the range of 13 days. To reduce the time it takes to perform measurement a systematic approach has been taken that includes mainly three areas. First the Bookkeeping of all information and data needed for the analysis and reporting is input before or during the measurement. Systematic Approach of how to setup sensors, handle cable and equipment, planning and measurement. This includes practical examples of how to. Finally it is very important to take steps to assure Quality early in the measurement and also avoiding disturbances in the sensor path. There will be practical examples of important disturbances to look out for and quality check to perform. It should also be noted that the measurements is regular measured in mines or start up halls under rpm sweeps or/and operating conditions of the machines.

  • 61. Gustavsson, Ingvar
    On Remote Electronics Experiments2011In: Using Remote Labs in Education / [ed] Zubia, Javier Garcia; Alves, Gustavo R., Bilbao: Duesto University Press , 2011, p. 157-176Chapter in book (Refereed)
    Abstract [en]

    Electrical experiments are common at schools and universities worldwide. Today several remote laboratories for such experiments supplement hands-on ones in science and engineering education. Some of the remote laboratories, where online students can perform physical experiments and get the same results as in a hands-on laboratory, are more or less replicas of hands-on ones [1], [2], [3]. Thus, online students compose circuits using real components and make real measurements on the circuits created. In this chapter, a workbench for remote electrical experiments based on the VISIR Open Lab Platform (Virtual Instrument Systems in Reality) designed at Blekinge Institute of Technology (BTH) is compared with hands-on ones. Since some years, such VISIR workbenches are used in regular university courses and at least one VISIR workbench is being tested in courses at lower levels [4], [5]. Some further development of the online workbench desirable to better adapt it to school level is discussed as well. The chapter may also serve as an introduction to online electrical experiments for teachers.

  • 62. Gustavsson, Ingvar
    et al.
    Claesson, Lena
    Nilsson, Kristian
    Zackrisson, Johan
    Zubia, Javier Garcia
    Jayo, Unai Hernandez
    Håkansson, Lars
    Bartunek, Josef Ström
    Lagö, Thomas L
    Claesson, Ingvar
    The VISIR Open Lab Platform2011In: Internet Accessible Remote Laboratories: Scalable E-Learning Tools for Engineering and Science Disciplines / [ed] Azad, Abul K.M.; Auer, Michael E.; Harward, V. Judson, IGI Global , 2011, p. 294-317Chapter in book (Refereed)
    Abstract [en]

    The VISIR Open Lab Platform designed at the Department of Electrical Engineering (AET), the Blekinge Institute of Technology (BTH), Sweden, is a platform for opening instructional laboratories for remote access 24/7 with preserved context. VISIR is an acronym for Virtual Instrument Systems in Reality. In VISIR laboratories, students perform physical experiments and laboratory work remotely. A unique interface gives them the feeling of “being there.” The platform software is published under a GPL license, and other universities, schools, etc., are invited use it to open their laboratories and to participate in further research and development. Apart from BTH, five universities in Europe have set up VISIR online laboratories for electrical experiments and the Indian Institute of Technology Madras in India will set up one soon. A VISIR community has been established. Common projects are initiated, and the sharing of learning material is being discussed. This chapter is a general introduction to VISIR and its possibilities.

  • 63. Gustavsson, Ingvar
    et al.
    Nilsson, Kristian
    Lagö, Thomas L
    On physical experiments and individual assessment of laboratory work in engineering education2009Conference paper (Refereed)
    Abstract [en]

    It is obvious that our society needs more engineers. It is also true that mankind must live in symbiosis with nature and focus on sustainability and understanding. Thus, engineers must be able to design products and services which are in line with the principles of nature and the only way to become familiar with these principles is to perform many physical experiments. A way to use instructional laboratories more effectively and offer more hours in the laboratories for students without significant increased cost per student is opening them for remote access. Hands-on experiments are indispensable but remote mouse-cursor-on ones can supplement them. The VISIR (Virtual Instrument Systems in Reality) Open Laboratory Platform offers an open standard for online workbenches enabling students not only to perform physical experiments 24/7 but also to practice laboratory work. Learning objectives of laboratory work, free access to laboratory resources, and individual assessment of such work should be important key elements in an education delivering engineers with a solid documented laboratory experience.

  • 64.
    Gustavsson, Ingvar
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Nilsson, Kristian
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Zackrisson, Johan
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Garcia-Zubia, J.
    Hernandez-Jayo, U.
    Nedic, Z
    Göl, Ö.
    MacHotka, J.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Pettersson, Mats
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    On objectives of instructional laboratories, individual assessment, and use of collaborative remote laboratories2009In: IEEE Transactions on Learning Technologies, ISSN 1939-1382, E-ISSN 1939-1382, Vol. 2, no 4, p. 263-274Article in journal (Refereed)
    Abstract [en]

    Three key issues should be addressed to enable universities to deliver engineers who have a solid documented laboratory experience enabling them to design goods and services complying with the requirements of a sustainable society. First, introduce learning objectives of engineering instructional laboratories in courses including laboratory components. Second, implement individual student assessment. Third, introduce free access to online experimental resources as a supplement to the equipment in traditional laboratories. Blekinge Institute of Technology (BTH) in Sweden and the University of South Australia (UniSA) have created online laboratory workbenches for electrical experiments that mimic traditional ones by combining virtual and physical reality. Online workbenches not only supplement traditional ones, but they can also be used for low-cost individual assessment. BTH has started a project disseminating the BTH workbench concept, The Virtual Instrument Systems in Reality (VISIR) Open Laboratory Platform, and invites other universities to set up replicas and participate in further development and standardization. Further, online workbenches offer additional learning possibilities. UniSA has started a project where students located in different countries can perform experiments together as a way to enhance the participants' intercultural competence. This paper discusses online laboratory workbenches and their role in an engineering education appropriate for a sustainable society.

  • 65. Hamid, Mohamed
    et al.
    Mohammed, Abbas
    Yang, Zhe
    On Spectrum Sharing and Dynamic Spectrum Allocation: MAC Layer Spectrum Sensing in Cognitive Radio Networks2010Conference paper (Refereed)
    Abstract [en]

    One of the most critical issues regarding wireless networks regulation agencies is how to manage the available electromagnetic radio spectrum in a way that satisfies the needs of the huge growing in wireless systems both economically and technically, especially with the recent crowding in the available spectrum. Hence, building cognitive radio systems supporting dynamic access to the available spectrum has appeared recently as a novel solution for the wireless system huge expansion. In this paper we investigate the MAC layer sensing schemes in cognitive radio networks, where both reactive and proactive sensing are considered. In proactive sensing the adapted and non-adapted sensing periods schemes are also assessed. The assessment of these sensing schemes has been held via two performance metrics: available spectrum utilization and idle channel search delay. Simulation results show that with proactive sensing adapted periods we achieve the best performance but with an observable overhead computational tasks to be done by the network nodes.

  • 66. Hanif, Muhammad
    et al.
    Niaz, Hamza
    Kahn, Muhammad Afsar
    Investigating the possible role and usefulness of video capture virtual reality in motor impairment rehabilitation2011Conference paper (Refereed)
    Abstract [en]

    Researchers in serious games area and professionals in stroke rehabilitation, working collaboratively in explorative interdisciplinary research studies in order to develop usable and effective applications. In this context, physiotherapists and occupational therapy are important elements of stroke rehabilitation. Applications from such exploratory development reflect motivational and easy to use features, which could be further designed and developed by serious games developers. This research study aims to investigate the role and usefulness of Video Capture Virtual Reality Technology (VCVRT) in motor impairment rehabilitation, to identify and explore the importance of this technology in healthcare, specifically in motor impairment rehabilitation. Likewise, to analyze the acceptance of VCVRT among the physiotherapists in terms of perceived ease of use, perceived usefulness and perceived intension to use. Results imply that video capture virtual reality technology can be use as complement to conventional physiotherapy. This technology is cheap, easy to use and is useful as a home based rehabilitation tool, but together with physiotherapist supervision or coaching. Moreover, VCVRT is motivational for weak patients and useful in motor rehabilitation in terms of quantity, i.e. intensity of exercise can be increased. Physiotherapist centered approach is necessary for game design process; effective game design suggestions and the idea of single gaming framework consists of different games acquiring multiple rehabilitation goals, are achieved from physiotherapists during the research. Technology acceptance value is high among physiotherapists. The research study provides a more detailed understanding of the factors involved in the implication of video capture virtual reality technology in motor impairment rehabilitation.

  • 67. Hoc, Phan
    et al.
    Duong, Quang Trung
    Zepernick, Hans-Jürgen
    Full-Rate Distributed Space-Time Coding for Bi-directional Cooperative Communications2010Conference paper (Refereed)
    Abstract [en]

    In this paper, a protocol for bi-directional cooperative communications applying full-rate distributed space-time codes and physical network coding is proposed. This scheme uses L relays to transmit the codewords in a distributed fashion. It takes 3 time slots for two sources to transmit two corresponding codewords by exploiting physical network coding and self-interference cancelation at each source. We prove that this scheme obtains full diversity. The analytical results show that the diversity order of this scheme will be L+1, where L is the number of relays. In addition, we assess the sum-rate of the bi-directional cooperative communication scheme and reveal that it achieves larger spectral efficiency compared to one-way cooperative communication scheme. We employ Monte Carlo simulations to validate the symbol error rate and the ergodic sum-rate of the scheme.

  • 68. Hult, Tommy
    et al.
    Mohammed, Abbas
    Application of Space-Time Signal Processing and Active Control Algorithms for the Suppression of Electromagnetic Fields2011In: Applied Signal and Image Processing: Multidisciplinary Advancements / [ed] Qahwaji, Rami; Green, Roger; Hines, Evor, Hershey: IGI Global , 2011, p. 45-60Chapter in book (Refereed)
    Abstract [en]

    Several studies have been conducted on the effects of radiation on the human body. This has been especially important in the case of radiation from hand held mobile phones. The amount of radiation emitted from most mobile phones is very small, but given the close proximity of the phone to the head it might be possible for the radiation to cause harm. The suggested approach involves the use of adaptive active control algorithms and a full space-time processing system setup (i.e. multiple antennas at both the transmitter and receiver side or MIMO), with the objective of reducing the possibly harmful electromagnetic radiation emitted by hand held mobile phones. Simulation results show the possibility of using the adaptive control algorithms and MIMO antenna system to attenuate the electromagnetic field power density.

  • 69. Hult, Tommy
    et al.
    Mohammed, Abbas
    MIMO applications for interference mitigation in multiple high altitude platform WCDMA systems2009Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate the possibility of multiple HAP coverage of a common cell area. In particular we study the uplink system performance since it is considered as a worst case scenario. In order to obtain further enhancement (interference mitigation) we also apply space-time diversity techniques, such as Single-Input Multiple-Output (SIMO) receive diversity or Multiple-Input Multiple-Output (MIMO) diversity, to improve the spectrum reuse in the multiple HAP scenario. We will show the level of improvement using SIMO and MIMO algorithms, the practical limits on the number of HAPs and SIMO/MIMO system dimension in response to traffic demands and the type of service used.

  • 70. Hult, Tommy
    et al.
    Mohammed, Abbas
    The Effect of Mutual Coupling on a High Altitude Platform Diversity System Using Compact Antenna Arrays2010In: International Journal of Antennas and Propagation, ISSN 1687-5869, E-ISSN 1687-5877, Vol. 2010Article in journal (Refereed)
    Abstract [en]

    We analyze the destructive effects of mutual coupling and spatial correlation between the separate antenna elements on a combined diversity system consisting of multiple HAPs (High-Altitude Platforms) employing various compact MIMO (Multiple-Input Multiple-Output) antenna array configurations, in order to enhance the mutual information in HAP communication links. In addition, we assess the influence of the separation angle between HAPs on system performance, and determine the optimal separation angles that maximize the total mutual information of the system for various compact MIMO antennas. Simulation results show that although the mutual information is degraded by mutual coupling and spatial correlation, the proposed HAP diversity system still provides better performance compared to a nondiversity system for all tested scenarios.

  • 71. Hult, Tommy
    et al.
    Mohammed, Abbas
    Yang, Zhe
    Grace, David
    Performance of a multiple HAP system employing multiple polarization2010In: Wireless Personal Communications, Springer , 2010, Vol. 52, no 1, p. 105-117Conference paper (Refereed)
    Abstract [en]

    In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with HAP (High Altitude Platforms) diversity techniques in order to increase the data rates in HAP communication systems. We will also investigate the effects of spatial correlation and mutual coupling between the separate antenna elements on system performance. Simulation results show that although the capacity is degraded by correlation and mutual coupling, we still achieve significant capacity gain compared to the single HAP case. In addition, we evaluate the performance of the system for different separation angles between HAPs, and determine the optimal separation angle that maximizes the total capacity of the system. © 2008 Springer Science+Business Media, LLC.

  • 72.
    Hultgren, Anders
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Bui, S.
    Linnér, Jörgen
    Ranstad, Per
    Lenells, Matz
    Fault tolerant high voltage resonant power converter application2013Conference paper (Refereed)
    Abstract [en]

    A high voltage and high power fault tolerant application of a resonant converter is presented. The resonant converter load shows frequent short circuits making the load voltage drop to zero within some us, implying high stress on the main circuit components. A load voltage short circuit fault tolerant system is suggested by including a novel way of augmenting the controller with a load voltage estimator. The estimator can detect load voltage short circuit and will then be a part of a fault tolerant high voltage resonant converter.

  • 73.
    Hultgren, Anders
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Kulesza, Wlodek
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Nilsson, Magnus
    Walther, Björn
    Integration av matematik och teknik på ingenjörsutbildningar2009Conference paper (Refereed)
    Abstract [en]

    An possible integration of mathematics and applications within engineering is presented. The integration method has been used at The university of Kalmar. The method is described and experiences are presented.

  • 74.
    Hultgren, Anders
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Melin, Jan
    Ranstad, Per
    Asymmetric Limit Cycles in an Industrially Applied Controlled Resonant Converter2009Conference paper (Refereed)
    Abstract [en]

    An industrially applied LCC power converter is modelled as a hybrid system. It is found that the hybrid system given a parameter set up and different initial conditions has three different limit cycles, one unstable and two asymmetric stable limit cycles. Effects of the asymmetric limit cycles are considered.

  • 75. Hultgren, Anders
    et al.
    Melin, Jan
    Ranstad, Per
    Limit cycle control of an industrially applied resonant converter modelled as a hybrid system2011Conference paper (Refereed)
    Abstract [en]

    Limit cycle control of an industrially applied high power, high voltage resonant power converter is modelled as a hybrid system. It is found that the hybrid system with three continuous states and one logic state given a parameter set up and different initial conditions has a rich solution set indicating possible problems in the industrial application. The solution set are one central closed trajectory and two asymmetric types of limit cycles.

  • 76. Hultgren, Anders
    et al.
    Melin, Jan
    Ranstad, Per
    Limit Cycles in an Industrially Applied Hybrid System2010Conference paper (Refereed)
    Abstract [en]

    An industrially applied LCC power converter is modelled as a hybrid system. It is found that the hybrid system with three continuous states and one logic state given a parameter set up and different initial conditions has among other solutions one central closed trajectory and two types of limit cycles, on the left and the right side. The other solutions are indicated.

  • 77.
    Iqbal, Mohammad Imran
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Analysis and modeling of optimal error protection for embedded codestreams2012In: Journal of Electronic Imaging (JEI), ISSN 1017-9909, E-ISSN 1560-229X, Vol. 21, no 2Article in journal (Refereed)
    Abstract [en]

    Efficient utilization of bandwidth is key to providing mobile multimedia services such as wireless imaging. As such, efficient allocation of the available parity budget for error protection of the associated codestreams is essential for ensuring quality of service. Computing the optimal parity allocation to the codestream packets may not be possible in real-time due to the huge number of ways the parity can be assigned to the codestream packets. This is particularly true for systems having limited resources, such as mobile handheld devices. As a result, it is important to provide an error-protection scheme that gives good error-protection performance while imposing low computational and memory demands on the system. We therefore analyze how different parameters such as signal-to-noise ratio and source distortion-rate function affect the optimal unequal error protection (UEP) scheme for embedded codestreams. We also propose to approximate the optimal UEP using suitable mathematical models in order to reduce the complexity that otherwise would occur with computing the optimal UEP. We investigate several models for their fitness in approximating the optimal UEP using different performance metrics. The simulation results show that most of these models provide an excellent trade-off between performance and complexity.

  • 78. Iqbal, Muhammad Imran
    Preferential Coding for Mobile Multimedia Services2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Different parts of source encoded multimedia streams such as those associated with standard image or video formats possess different levels of importance with respect to their contribution to the quality of the reconstructed image or video. This unequal importance among data within a codestream gives rise to preferential treatment of the more significant parts of the codestream compared to the less important parts. Similarly, visual information offered by certain regions of an image or video may attract viewer’s attention more than other parts of the viewing area. As a consequence, preferential treatment of important data and information can play a vital role in mobile multimedia services in order to preserve satisfactory quality of service under the harsh conditions of a band-limited, error-prone wireless channel. In this thesis, we therefore, investigate how preferential coding can be used to protect multimedia services more efficiently against transmission errors. For this purpose, an error sensitivity analysis of the specific application is utilized as a basis to design efficient unequal error protection (UEP) schemes. The performance of the proposed preferential coding schemes is evaluated using objective perceptual quality metrics in order to account for the fact that humans are the ultimate judges of service quality. The thesis is divided into four parts. In the first part, region of interest (ROI) identification, coding and advantages of ROI coding for different applications are investigated. In addition, a framework is proposed for using ROI coding in wireless imaging. The second part analyses the error sensitivity of wireless JPEG2000 (JPWL) in terms of perceptual quality metrics. It is also shown that using reduced- reference perceptual quality metrics as error sensitivity descriptor (ESD) in JPWL increases the effectiveness of ESD. Specifically, this type of metrics correlates well with subjective quality assessment and provides an additional estimate for the obtained quality. In the third part, two UEP schemes for JPWL are proposed and compared with equal error protection (EEP). Their performance is evaluated in terms of perceptual quality metrics such as structural similarity index and the visual information fidelity criterion of the reconstructed image and their benefit over EEP is revealed. Finally, in the fourth part, a framework for optimized preferential coding of ROI based images and videos is proposed. Specifically, a dynamic programming algorithm for optimal parity distribution is provided.

  • 79. Iqbal, Muhammad Imran
    et al.
    Zepernick, Hans-Jürgen
    A Framework for Error Protection of Region of Interest Coded Images and Videos2011In: Signal processing. Image communication, ISSN 0923-5965, E-ISSN 1879-2677, Vol. 26, no 4-5, p. 236-249Article in journal (Refereed)
    Abstract [en]

    In this paper, we propose a framework for unequal error protection (UEP) of image and video streaming over a wireless channel. Our framework of allocating the parity symbols associated with error control coding to the image or video codestream takes advantage of the different levels of importance that particular spatial regions of visual multimedia content has to human observers. As such, it provides stronger protection against transmission impairments to those parts of an image or video stream that correspond to the regions of interest (ROIs) while weaker protection is applied to the background (BG). For this purpose, an image or video stream represented by a sequence of packets is split into smaller cells in such a way that certain cells contain the parts of a codestream that represent ROIs and the last cell carries solely BG information. The available parity budget obtained from the given code rate is then distributed among these cells based on their contribution to the overall perceptual quality of a reconstructed image or video. A dynamic programming approach is utilized to facilitate optimal allocation of parity to ROIs and BG for ROI based UEP. The performance of the proposed ROI based UEP scheme in terms of a objective perceptual quality metric is analyzed and compared with both the optimal UEP without ROI processing and equal error protection (EEP) using the structural similarity (SSIM) index. Performance results validate the effectiveness of our framework and the superior performance of the proposed UEP scheme compared to EEP. The performance of the proposed UEP scheme matches well with that of the optimal UEP without ROI processing, especially, for multiple spatial description image and video coding while computational complexity can be kept much lower.

  • 80.
    Iqbal, Muhammad Imran
    et al.
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Error Protection for Wireless Imaging: Providing a Trade-off Between Performance and Complexity2010Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a number of error protection schemes for wireless imaging ranging from simple but less efficient equal error protection to very complex yet optimal error protection. The main objective is to facilitate tradeoffs between performance and complexity in choosing an error protection scheme. Our technique provides the system designer with a number of solutions from which the application can choose those that best suits the available resources such as processing power and data rate. For this purpose, an image codestream is split into smaller cells each having a certain number of packets while the available parity symbols from the deployed error protection are optimally allocated to these cells. Subsequently, the parity symbols allocated to these cells are distributed among the packets that constitute each of these cell. Finally, the error control codes for every packet are determined based on the number of parity symbols allocated to each packet. Larger cells provide less complex but also less efficient error protection while smaller cells result in a better error protection performance but at the cost of increased complexity. Simulation results validate the effectiveness of the considered technique in providing the desired performances-complexity trade-off. To obtain better correlation with human perception, performance is evaluated in terms of objective perceptual quality metrics.

  • 81. Iqbal, Muhammad Imran
    et al.
    Zepernick, Hans-Jürgen
    Quality Assessment of Error Protection Schemes for Wireless JPEG20002010Report (Other academic)
    Abstract [en]

    Wireless imaging services suffer large impairments due to the hostile nature of the wireless channel. Given the limited and expensive channel bandwidth and the high data demanding nature of these services, it becomes a challenging task to provide high quality of service in such error prone channels. Clearly, suitable error protection is necessary in order to maintain sufficient quality of these services under various channel conditions. In this report, therefore, we have investigated different channel error protection schemes for a wide range of channel conditions and coding rates. Two unequal error protection (UEP) schemes have been examined for JPEG2000 images exploiting useful features of the JPEG2000 codestream and using the error protection tool set provided by wireless JPEG2000 (JPWL). Taking the importance of the initial codestream packets on the reconstruction of the image at the receiver into account, the first scheme uses all the additional bandwidth resources in protecting the initial packets of the codestream. The rest of the packets, which are of relatively low importance, are transmitted without any parity symbols assigned to them. In the second UEP scheme, the initial parts of the codestream are strongly protected by assigning them an increased amount of parity symbols. In addition, the tail packets of the codestream are also protected but using a weaker error control code compared to the initial packets. The performance of the proposed UEP schemes has been investigated in terms of the peak signal-to-noise ratio as a typical fidelity metric and three perceptual quality metrics, namely, the Lp-norm, the structural similarity index, and the visual information fidelity criterion. Numerical results of the proposed UEP schemes have been compared with conventional equal error protection (EEP) over additive white Gaussian noise (AWGN) channel as well as Rayleigh fading channel in the presence of AWGN. The results reveal the superior performance of the suggested UEP schemes compared to EEP over a range of channel signal-to-noise ratios and code rates.

  • 82. Iqbal, Muhammad Imran
    et al.
    Zepernick, Hans-Jürgen
    Engelke, Ulrich
    Perceptual-based quality assessment of error protection schemes for wireless JPEG20002009Conference paper (Refereed)
    Abstract [en]

    Designing wireless imaging services with acceptable quality imposes great challenges due to the severe impairments induced by wireless channels, high data rate demands and limited transmission bandwidth. In this paper, we examine different error protection schemes for the JPEG2000 codestream using the error control codes offered by the wireless JPEG2000 (JPWL) standard. In particular, two unequal error protection (UEP) schemes are considered. In the first scheme, only the initial and more important packets of the JPWL codestream are protected while the remaining packets are left without protection. In contrast, the second scheme uses a strong code for the initial packets while a weaker code is used for the tail packets. As quality of visual services may not be captured adequately with traditional link layer metrics, code selection and their performance assessment is based on perceptual quality metrics. Specifically, the LP -norm, structural similarity (SSIM) index and visual information fidelity (VIF) criterion are utilized. Numerical results are provided for a range of system conditions under which UEP outperforms conventional equal error protection in terms of perceptual quality metrics.

  • 83.
    Iqbal, Muhammad Imran
    et al.
    Blekinge Institute of Technology, School of Computing.
    Zepernick, Hans-Jürgen
    Blekinge Institute of Technology, School of Computing.
    Fiedler, Markus
    Blekinge Institute of Technology, School of Computing.
    Shaikh, Junaid
    Blekinge Institute of Technology, School of Computing.
    Spatio-Temporal Quality of Experience Trade-offs for Mobile Imaging Applications2010Conference paper (Refereed)
    Abstract [en]

    In this paper, we focus on mobile images given in JPEG2000 format and evaluate their spatio-temporal Quality of Experience (QoE). In particular, the trade-of between spatial QoE supported by progressive source encoding and temporal QoE related to network delay as well as initial transmission delay is examined.

  • 84. Ishaq, Rizwan
    et al.
    Shahid, Muhammad
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Lövström, Benny
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Zapirain, Begona Garcıa
    Claesson, Ingvar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Modulation frequency domain adaptive gain equalizer using convex optimization2012Conference paper (Refereed)
    Abstract [en]

    Adaptive gain equalizer (AGE) is a commonly used single-channel speech enhancement algorithm. AGE and its variants has been widely used for speech enhancement applications. There are two broad categories of these variants. The first deals with its improvement in time-frequency domain with readjustment of the used parameters and the second one deals with performing the main filtering operation in modulation frequency domain. This paper evaluates the working of AGE in modulation frequency domain with the use of a demodulation technique which solves the demodulation process as a convex optimization problem. The performance of the modified AGE is compared with the traditional AGE and another modulation frequency domain AGE based on demodulation using the spectral center-of-gravity. These used performance measures are Signal to Noise Ratio Improvement(SNRI), Spectral Distortion(SD) and Mean Option Score(MOS).

  • 85. Ishaq, Rizwan
    et al.
    Zapirain, Begona Garcia
    Shahid, Muhammad
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Lövström, Benny
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Subband Modulator Kalman Filtering for Single Channel Speech Enhancement2013Conference paper (Refereed)
    Abstract [en]

    his paper presents a single channel speech enhancement technique based on sub-band modulator Kalman filtering for laryngeal (normal) and alaryngeal (Esophageal speech) speech signals. The noisy speech signal is decomposed into sub-bands and subsequently each sub-band is demodulated into its modulator and carrier components. Kalman filter is applied to modulators of all sub-bands without altering the carriers. Performance of the proposed system has been validated by Mean Opinion Score (MOS) for laryngeal and Harmonic to Noise Ratio (HNR) for alaryngeal speech. An improvement of 20% has been observed in MOS over sub-band Kalman filtering for laryngeal speech, while 3 to 4 dB enhancement in HNR has been observed for alaryngeal speech over the full-band Kalman filtering.

  • 86. Jamil, Momin
    et al.
    Zepernick, Hans-Jürgen
    Pettersson, Mats
    Cross-ambiguity function of weighted pulse trains with Oppermann sequences2009Conference paper (Refereed)
    Abstract [en]

    The design of integrated radar and communication systems may be based on sets of polyphase sequences such as Oppermann sequences. In this paper, we derive an analytical expression for the cross-ambiguity function of weighted pulse trains with Oppermann sequences. Further, the auto-ambiguity function is deduced from this as a special case. Numerical examples are provided to illustrate the relationship between sequence parameters and performance characteristics.

  • 87. Jamil, Momin
    et al.
    Zepernick, Hans-Jürgen
    Pettersson, Mats
    Properties of ambiguity functions for weighted pulse trains with oppermann sequences2009Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider properties of the autoambiguity and cross-ambiguity functions of weighted pulse trains with Oppermann sequences. Several properties are examined and proved which in turn allows for reducing the design space for optimization of a particular design. The insights gained from these properties are consolidated in a formal framework leading to procedures that can be used for a more structured waveform design. Numerical examples are provided to illustrate the relationship between sequence parameters and performance characteristics.

  • 88. Jung, Younchan
    et al.
    Ibanez, Al Ann
    Zepernick, Hans-Jürgen
    Atwood, J. William
    Impact of Adaptive Packet Coding on Speech Quality in Wireless VoIP2010In: Telecommunications Review, ISSN 1226-5586, Vol. 20, no 3, p. 368-378Article in journal (Refereed)
    Abstract [en]

    The specific packet loss recovery coding used in a Voice over IP (VoIP) system can have a significant impact on the quality to the receiver. In this paper, we propose adaptive quality coding, which cannot only improve the perceptual quality for VoIP services over wireless environments but also utilizes only a small amount of additional bandwidth.

  • 89. Kahn, Muhammad Afsar
    et al.
    Israr, Nauman
    Hassan, Sher
    Usability Evaluation of Web Office Applications in Collaborative Writing2010Conference paper (Refereed)
    Abstract [en]

    Usability evaluation of collaborative writing system for education usage is essential to improve its functionality. In this paper, the usability of web office (ThinkFree doe) is tested using mix research approach. Usability evaluation is performed via the think aloud protocol. A questionnaire was designed for quantitative survey. The questionnaire was completed by users who have been using Thinkfree doc for educational collaborative work. Interviews were conducted with the selected participants for results validation. During usability evaluation process, positive and negative effects regarding software's usage were recorded. The results revealed that the overall systems response is very slow. The software needs to improve its processing speed in order to make it more efficient for future use. The system also needs to improve overall functionality (for example collaborative work, synchronization, uploading and track changes) to provide accurate and complete results.

  • 90. Kamal, Hany
    et al.
    Mohammed, Abbas
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Game Theory for Cognitive Radio2013In: Cognitive Radio and Interference Management: Technology and Strategy / [ed] Meng-Lin Ku and Jia-Chin Lin, IGI Global, 2013, p. 115-126Chapter in book (Refereed)
    Abstract [en]

    Demands on high data rate applications are increasing and consequently demands on spectral resources are increasing as well. Although electromagnetic spectrum is recently said to be in a scarcity situation, several studies have shown that this scarcity is mainly due to the legacy command-and-control regulation rather than due to physical scarcity of spectrum. For this reason, researchers have started investigating techniques to better manage the usage of spectrum. Among these techniques there exist the methods allowing the primary/secondary usage of spectrum, or secondary market. Secondary market techniques mainly manage sensing, accessing, and aborting the spectrum usage by the secondary users. Techniques developed for secondary market context are also referred to as algorithms for Cognitive Radio (CR) networks. Regulators worldwide took measures to promote the deployment of primary/secondary context. In this chapter, the authors give an illustrative discussion on CR and on the application of game theory to overcome the spectrum scarcity problem. Game theory is a field of applied mathematics that describes and analyzes scenarios with interactive decisions. In recent years, there has been considerable interest in adopting game theoretic approaches to model many communications and networking problems such as radio resource management and routing. Nowadays, game theory is also used to model interactive situations for CR terminals.

  • 91.
    Khan, Imran
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Gertsovich, Irina
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Claesson, Ingvar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Johansson, Per-Erik
    Wirenstedt, Maria
    Borja, Oscar
    Petersson, Stefan
    MRI SCANNER VIBRATION PATH ANALYSIS2013In: Machinery Noise and Vibration, 2013, article id 725Conference paper (Other academic)
    Abstract [en]

    Magnetic Resonance Imaging (MRI) scanner is one of the most important tools in clinical diagnostics. MRI scanners are associated by strong vibration which results in unpleasant and disturbing acoustic noise. The primary source of this vibration is the Lorentz force produced by fast switching of the currents inside the gradient coils of MRI scanners under a strong static magnetic field. During an MR-imaging scan the switching is controlled in order to spatially code the hydrogen nuclei that will generate the signal, which is reconstructed into anatomical images. Faster switching of the currents allows for shorter scan times and/or higher image resolutions. Consequently, the clinical quality has motivated the drive for shorter switching time and higher currents. This development, however, has also caused an undesired increase of MRI vibrations. The overall vibration phenomenon of an installed fully functional MRI scanner system becomes unique because of the installed location and ambiance. This vibration can potentially degrade the image quality and hence the diagnosis. Apart from the vibration produced, the associated annoying acoustic noise may not only affect the patients under examination and the clinical staff, but may also be transmitted to other parts of the building and causing discomfort for the personnel working there. In order to devise an effective isolation plan or improve an existing one both for vibration and acoustic noise it is important to study the noise and vibration transfer paths. This paper concerns an investigation of vibration transfer paths for vibration excited by an installed functional MRI scanner at a medical facility. The vibration transfer paths have been investigated experimentally. The obtained results are presented and discussed.

  • 92.
    Khan, Imran
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Moazzam, M
    Rabbani, S.M.
    Johansson, Sven
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    PERFORMANCE EVALUATION OF CONTROL ALGORITHMS IMPLEMENTED ON A REMOTELY CONTROLLEDACTIVE NOISE CONTROL LABORATORY2013Conference paper (Other academic)
  • 93.
    Khan, Imran
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Muhammad, Moazzam
    Rabbani, Muhammad Shoaib
    BTH.
    Johansson, Sven
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Performance evaluation of control algorithms implemented on a remotely controlled active noise control laboratory2013In: Active Noise and Vibration Control in Practical System Implementations, 2013, article id 731Conference paper (Other academic)
    Abstract [en]

    The remotely controlled laboratory setup for Active Noise Control (ANC) developed by Blekin-ge Institute of Technology, Sweden provides an efficient learning platform for the students to implement and learn ANC algorithms with real world physical system, hardware and signals. The initial laboratory prototype based on a Digital Signal Processor (DSP) TMS320C6713 from Texas Instruments (TI) was successfully tested with Filtered-x Least Mean Square (F-XLMS) algorithm applied to control noise in a ventilation duct. The resources of the DSP platform used in the remote laboratory setup enable testing and investigating substantially more challenging and computationally demanding algorithms. In this paper, we expand the horizon of the laboratory setup by testing more advanced and complicated single channel feed forward ANC algorithms. Filtered-x versions of algorithms such as the normalized least mean square (N-LMS), leaky least mean square (L-LMS), Filtered-U recursive least mean square (FURLMS) and recursive least square (RLS) algorithm etc. have been implemented utilizing the remote web based client provided in the remote laboratory. A comprehensive performance comparison of the aforementioned algorithms for the remote laboratory setup is presented to demonstrate the viability of the remote laboratory.

  • 94.
    Khan, Imran
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Muthusamy, Dinesh
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Ahmad, Wasim
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Nilsson, Kristian
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Zackrisson, Johan
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Gustavsson, Ingvar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Remotely controlled laboratory setup for Active Noise Control and acoustic experiments2012Conference paper (Refereed)
    Abstract [en]

    This paper presents a remotely controlled educational experiments setup for Active Noise Control (ANC) and acoustic experiments. The experiments setup is based on the Virtual Instruments Systems in Reality (VISIR) open source platform, National Instruments LabVIEW software and a Digital Signal Processor TMS320C6713 from Texas Instruments. The software development and equipment are controlled remotely form a client PC using a standard web browser. The proposed laboratory setup focuses on ANC experiments applied to noise in a ventilation duct. The laboratory setup will enable students to test and investigate properties and behaviour of adaptive algorithms in reality as compared to more confined simulations usually carried out in Matlab etc. The general steps in ANC, such as the feasibility of active control, designing, testing and debugging ANC algorithms, configuration and implementation of an active control system, are all covered. In addition students will be able to study the effect of analog to digital converters (ADC), anti-aliasing filters, digital to analog converters (DAC) and reconstruction filters using digital signal processing in reality, etc. The laboratory setup is suitable for a wide range of courses such as sound related experiments in upper secondary school physics, digital signal processing, adaptive signal processing, and acoustics at university level.

  • 95.
    khan, Imran
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Muthusamy, Dineshkumar
    Ahmad, Waqas
    Gustavsson, Ingvar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Zackrisson, Johan
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Nilsson, Kristian
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Remotely Controlled Laboratory Setup for Active Noise Control and Acoustic Experiments2012Conference paper (Refereed)
    Abstract [en]

    This paper presents a remotely controlled educational experiments setup for Active Noise Control (ANC) and acoustic experiments. The experiments setup is based on the Virtual Instruments Systems in Reality (VISIR) open source platform, National Instruments LabVIEW software and a Digital Signal Processor TMS320C6713 from Texas Instruments. The software development and equipment are controlled remotely form a client PC using a standard web browser. The proposed laboratory setup focuses on ANC experiments applied to noise in a ventilation duct. The laboratory setup will enable students to test and investigate properties and behaviour of adaptive algorithms in reality as compared to more confined simulations usually carried out in Matlab etc. The general steps in ANC, such as the feasibility of active control, designing, testing and debugging ANC algorithms, configuration and implementation of an active control system, are all covered. In addition students will be able to study the effect of analog to digital converters (ADC), anti-aliasing filters, digital to analog converters (DAC) and reconstruction filters using digital signal processing in reality, etc. The laboratory setup is suitable for a wide range of courses such as sound related experiments in upper secondary school physics, digital signal processing, adaptive signal processing, and acoustics at university level.

  • 96.
    khan, Imran
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Muthusamy, Dineshkumar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Ahmad, Waqas
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Gustavsson, Ingvar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Zackrisson, Johan
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Nilsson, Kristian
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Johansson, Sven
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Remotely Controlled Active Noise Control Laboratories2012Conference paper (Refereed)
    Abstract [en]

    Remotely controlled laboratories in educational institutions are gaining popularity at an exponential rate due to the multidimensional benefits they provide. The Virtual Instrument Systems in Reality (VISIR) project by Blekinge Institute of Technology (BTH) Sweden has successfully implemented remotely controlled laboratories, with remotely controlled real instruments and experimental setups. Currently these laboratories provide students the opportunity to conduct experiments in the field of electronics, antenna theory and mechanical vibration measurements. In this paper a prototype system of a remotely controlled laboratory for active noise control (ANC) is introduced. The proposed lab will focus on addressing the problem of a ventilation duct noise. The laboratory is informative and to a great extent introduces a student to the general steps in ANC when it is suggested as a plausible solution for a noise problem. The student can perform an investigation concerning feasibility of active control, design, configuration and implementation of an active control system. The laboratory is based on a modern and relevant DSP platform with the corresponding software development environment controlled remotely. In addition, it may be utilized remotely both for lab assignments in acoustics courses and digital signal processing courses.

  • 97.
    Khan, Imran
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Muthusamy, Dineshkumar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Ahmad, Waqas
    Sällberg, Benny
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Nilsson, Kristian
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Zackrisson, Johan
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Gustavsson, Ingvar
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Håkansson, Lars
    Performing active noise control and acoustic experiments remotely2012In: International Journal of Online Engineering, ISSN 1868-1646, E-ISSN 1861-2121, Vol. 8, no special issue 2, p. 65-74Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel and advanced remotely controlled laboratory for conducting Active Noise Control (ANC), acoustic and Digital Signal Processing (DSP) experiments. The laboratory facility, recently developed by Blekinge Institute of Technology (BTH) Sweden, supports remote learning through internet covering beginners level such as simple experimental measurements to advanced users and even researchers such as algorithm development and their performance evaluation on DSP. The required software development for ANC algorithms and equipment control are carried out anywhere in the world remotely from an internet-connected client PC using a standard web browser. The paper describes in detail how ANC, acoustic and DSP experiments can be performed remotely The necessary steps involved in an ANC experiment such as validity of ANC, forward path estimation and active control applied to a broad band random noise [0-200Hz] in a ventilation duct will be described in detail. The limitations and challenges such as the forward path and nonlinearities pertinent to the remote laboratory setup will be described for the guidance of the user. Based on the acoustic properties of the ventilation duct some of the possible acoustic experiments such as mode shapes analysis and standing waves analysis etc. will also be discussed in the paper.

  • 98. Khan, Muhammad Gufran
    On Modulation and Detection Schemes for Low-Complexity Impulse Radio UWB Communications2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to wealth of advantages offered by short range ultra wideband (UWB) technology, such as capacity improvement, fading reduction and localization, it has gathered a considerable attention. Distinct UWB qualities also pose many system design challenges like difficulties in using digital processing, complex channel estimation and different propagation characteristics. The main objective of the thesis is to develop and evaluate efficient modulation and detection schemes for impulse radio (IR) UWB with a focus on wireless sensor networks characterized by low cost and low power consumption. The content of the thesis comprises of five parts. In Part I, a coherent RAKE and non-coherent energy detector (ED) and transmitted reference (TR) receivers are examined and their bit-error-rate (BER) performance is evaluated using channels measured in an industrial environment. In specific, selective RAKE (SRake) and partial RAKE (PRake) for both maximal ratio combining (MRC) and equal gain combining (EGC) are compared. Based on the analysis and simulation results, it is concluded the SRake with EGC is to be preferred, whereas the best complexity/performance trade-off is provided by the ED based receivers. Part II presents several signaling and detection schemes; the proposed schemes are recursive TR (R-TR), dual-doublet TR (DDTR), doublet-shift TR (DSTR) and binary pulse position modulation (BPPM)/DSTR. Analysis and simulations verify that the proposed schemes may be preferred over the conventional TR in terms of BER, energy efficiency and/or implementation complexity. Part III presents a non-coherent kurtosis detector (KD) and a fourth-order detector (FD), which can discriminate between Gaussian noise and non-Gaussian IR-UWB signals by directly estimating the fourth-order moment of the received signal. Empirical evaluations and simulations using channel measurements conducted in a corridor, an office and a laboratory environment verify that performance of the proposed FD receiver is slightly better than the ED in the low SNR region and its performance improves as the SNR increases. Part IV presents a robust weighted ED (WED) in which the weighting coefficients are estimated adaptively based on the received stochastic data. Simulation results confirm that performance of the proposed weight estimation method is close to that of a data-aided (DA) scheme. Finally, Part V focuses on a multi-user scenario and develops a weighted code-multiplexed TR (WCM-TR) receiver employing the robust adaptive weight estimation scheme. Secondly, a BPPM/CM-TR UWB system is presented to mitigate inter-frame interference (IFI) and multi-user interference (MUI) from other asynchronous users. The BPPM/CM-TR system is 3 dB energy-efficient and improves the BER performance by mitigating MUI/IFI in the high SNR region, while for the low SNR case and single-user scenario, a dual-mode BPPM/CM-TR system is suggested

  • 99. Khan, Muhammad Gufran
    et al.
    Sällberg, Benny
    Nordberg, Jörgen
    Claesson, Ingvar
    Energy efficient binary PPM/code-multiplexed transmitted-reference multi-user UWB system2011Conference paper (Refereed)
    Abstract [en]

    This paper presents a combined binary pulse position modulation (BPPM)/code-multiplexed transmitted-reference (CM-TR) ultra wideband (UWB) system. The low complexity CM-TR UWB is not energy efficient as one half of the energy is used to transmit reference pulses and, even at low-to-medium data rates, it suffers from strong multi-user interference (MUI) and inter-frame interference (IFI). Keeping the information rate constant, the combined BPPM/CM-TR UWB system utilizes 3 dB less energy per bit as compared to the CM-TR system and achieves relatively longer silent periods between the pulses, which not only mitigate the IFI but also decrease the MUI due to less collisions with other asynchronous users. In the high SNR region, where the effect of IFI and MUI severely degrades the bit-error-rate (BER) performance of the multiuser CM-TR system, simulation results verify that the multiuser BPPM/CM-TR outperforms the multiuser CM-TR system.

  • 100. Khan, Muhammad Gufran
    et al.
    Sällberg, Benny
    Nordberg, Jörgen
    Claesson, Ingvar
    Non-coherent detection of impulse radio UWB signals based on fourth order statistics2009Conference paper (Refereed)
    Abstract [en]

    Non-coherent receivers are an attractive solution for impulse radio (IR) ultra wideband (UWB) systems due to their low-complexity implementation and low power consumption. However, low-complexity detection is achieved at the expense of some loss in performance. In this paper, a non-coherent detection scheme based on fourth order statistics, i.e., kurtosis, is proposed for low data rate IR-UWB systems. The performance of a conventional energy detector (ED) and the proposed kurtosis detector (KD) is compared in terms of bit-error-rate (BER). The simulation results validate that the KD receiver outperforms a conventional ED receiver on both additive white Gaussian noise (AWGN) and IEEE 802.15.4a multipath channels.

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