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  • 101.
    Gertsovich, Irina
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Bartuněk, Josef Ström
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Håkansson, Lars
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Nilsson, Mikael
    A novel methodology for the interoperability evaluation of an iris segmentation algorithm2013Conference paper (Refereed)
    Abstract [en]

    The performance of an iris recognition system depends greatly on how well the iris segmentation part of the system performs its task. The performance of an iris segmentation algorithm can be evaluated using different criteria and methods. Some of the methods evaluate the performance of the segmentation algorithm based on the performance of the whole iris recognition system. Other methods evaluate the performance of an iris segmentation subsystem independent of the performance of the system's other subsystems. To our knowledge there do not exist a generally accepted method or criteria for the evaluation of the standalone iris segmentation subsystem. This paper proposes a novel methodology to compare the performance of different iris segmentation algorithms, applied to different image datasets in a consistent way. The methodology employs the F1 score and an empirical cumulative distribution function. The implementation of the F1 score estimation, adapted to the iris segmentation task is described. Finally the application of the proposed methodology is demonstrated and discussed.

  • 102.
    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.

  • 103. Griffiths, Wayne
    et al.
    Zepernick, Hans-Jürgen
    Caldera, Manora
    APP Decoding of Non-Binary Block Codes on Gilbert-Elliott Channels Using Generalized Weight Polynomials2008Conference paper (Refereed)
    Abstract [en]

    In this paper, we present an a-posteriori probability (APP) decoding algorithm for non-binary block codes on non-binary Gilbert-Elliott channels (GECs) using generalized weight polynomials. The proposed approach is based on a single-sweep APP decoding technique that utilizes matrix multiplications. By fixing the crossover probability in the `bad' state of the non-binary GEC such that for a given transmitted symbol, all symbols are equally likely to be received, an APP decoding decision can efficiently be reached by evaluating trivariate polynomials. In this case, the non-binary GEC is described by three variables that are referred to as the average fade to connection time ratio, the burst factor, and the channel reliability factor. The application of the generalized weight polynomial approach is demonstrated with respect to numerical performance results obtained for simple non-binary block codes from computer simulations.

  • 104.
    Grunditz, David
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Implementation av CUSUM/SPRT-algoritm för kvalitetsövervakning i realtid av robotsvetsning2005Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    In the early 1990s, Volvo Car Corporation in Olofström started a project focusing on monitoring systems for robotized Gas Metal Arc (GMA) welding. This resulted in a research project where Stefan Adolfsson, Department of Production and Materials Engineering, Lund University/ Blekinge Tekniska Högskola, presented in 1998 the doctoral thesis, Automatic Quality Monitoring in GMA Welding using Signal Processing Methods. This doctoral thesis presented a Sequential Probability Ratio Test, SPRT, concept for quality monitoring automatic robotized GMA welding. To create a cost efficient monitoring system the Industriellt Utvecklingscentrum i Olofström AB presented the idea of using a traditional PC computer as a system platform. A traditional PC computer offers high performance to relatively low cost. The main task of this thesis is to implement the SPRT concept for monitoring automatic robotized GMA welding in the LabVIEW environment on a PC and evaluate the real time capacity. A second task in the thesis is to make a survey of similar monitoring systems for robotized GMA welding. The final implementation monitors both mean and variance of the weld voltage and the weld current. In total four different SPRT concepts have been implemented. They are modifications of the SPRT concept that is presented in the doctoral thesis. Two of the SPRT concepts were developed during this exam thesis work and are intended to reduce the risk of false alarms caused by natural systematic variations. Since four different SPRT concepts have been implemented and every single concept monitor both mean and variance of the weld voltage and the weld current, it means that there are in total 16 SPRT algorithms working in parallel. The evaluation of the implementation shows that an ordinary PC is sufficient for real time monitoring and that only two of the four SPRT concepts are suitable. The result of the market research of comparable monitoring systems indicates that there exist a small number of comparable welding monitoring systems.

  • 105. Gustafsson, Harald
    Speech enhancement for mobile communications2002Doctoral thesis, comprehensive summary (Other academic)
  • 106. Gustafsson, Harald
    et al.
    Lindgren, Ulf
    Claesson, Ingvar
    Low-complexity feature-mapped speech bandwidth extension2006In: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, p. 577-588Article in journal (Refereed)
    Abstract [en]

    Today's telecommunications systems use a limited audio signal bandwidth. A typical bandwidth is 0.3-3.4 kHz, but recently it has been suggested that mobile phone networks will facilitate an audio signal bandwidth of 50 Hz-7 kHz. This is suggested since an increased bandwidth will increase the sound quality of the speech signals. Since only few telephones initially will have this facility, a method extending the conventional narrow frequency-band speech signal into a wide-band speech signal utilizing the receiving telephone only is suggested. This will give the impression of a wide-band speech signal. The proposed speech bandwidth extension method is based on models of speech acoustics and fundamentals of human hearing. The extension maps each speech feature separately. Care has been taken to deal with implementation aspects, such as noisy speech signals, speech signal delays, computational complexity, and processing memory usage.

  • 107.
    Gustafsson, Ida
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    OCT inom ögonsjukvård: noggrannhet hos mätfunktion2008Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    This report is about Optical Coherence Tomography (OCT), a new technology with an increasing popularity at eye clinics. The OCT equipment is used for diagnostic purposes and can detect eye diseases in the area of the yellow spot and the optic nerve. In May 2007 the eye clinic at Blekingesjukhuset invested in a Topcon 3D OCT-1000. This OCT instrument has a measurement function named Caliper, which measures the retinal thickness. This study investigates what Caliper is, how it works, and its reliability. A 3D OCT examination was performed on ten test persons. For each person eight OCT images were captured. One of the images was captured with correct adjustments of the parameters and was used as a reference image. The seven remaining images were captured when the operator deliberately adjusted the parameters incorrect or the patient was focusing away from the fixation point. For all OCT images Caliper measurements were made between the bottom of fovea and the retinal pigment epithelium. All image measurements from a certain test person were compared to that person’s reference image. Additional measurements were made to investigate if manual measurements of retinal thickness give the same results as automatic measurements executed by the OCT equipment. The measurements showed that neither the operator’s incorrect adjustments nor the patient’s incorrect fixation did affect the Caliper measurements in ways worth mentioning. The measurement deviation of a few micrometres can be a result from human measurement errors. During this study an increased difficulty was observed when trying to measure skew images or less sharp images. The results of this study also show that manual and automatic measurements of mean retinal thickness give the same value. This study can not answer the question about how Caliper accomplishes its retinal thickness measurements since the measurement algorithm is a corporate secret. Caliper measures the distance between two different spots and is probably calculating the number of pixels. Finally, the measurements in this study show that Caliper is reliable.

  • 108. Gustavsson, Ingvar
    How to open a local electronics laboratory for remote access2008Conference paper (Other academic)
    Abstract [en]

    A local electronics laboratory can be opened for remote access using the VISIR Open Lab Platform. This is a way to open the laboratory for students on campus and off cam-pus 24/7 without any risk for themselves or the experimental equipment. The VISIR Open Lab Platform is a server/client application enabling learners to perform physical electrical experiments described in lab instruction manuals over the internet using a web browser. Virtual front panels and a virtual breadboard displayed on the client PCs are used to control the physical equipment connected to the server. The server is a time shared online workbench giving the learners the impression that they are working in a real laboratory. Such a workbench supplements a local laboratory equipped with work-benches comprising oscilloscope, function generator, DMM, triple power supply, and a solderless breadboard. Apart from Blekinge Institute of Technology in Sweden, where the platform has been created two universities, University of Deusto in Spain and FH Campus Wien in Aus-tria, have already implemented copies of the workbench and use them in their regular education. Other universities are ready to start. Thus, the workbench is being used at universities but it is perfect for schools and for vocational education as well. It is easy for teachers to introduce their own existing lab assignments. A modem connection and a web browser with Flash player are sufficient for the learner. The software required to set up such a workbench was published approximately a year ago under a GNU GPL licence. Apart from a standard PC the hardware required to join the VISIR Group and implement a workbench is a PXI chassis with instruments from National Instruments and a switching matrix. The components to be used by the learners are to be provided by the teachers and installed in the matrix. Universities, schools and other teaching organizations are invited to participate and open their local laboratories for remote access in order to be able to produce engineers with a solid and documented lab experience but without significantly increased cost per student. This tutorial is divided into four parts. They are about: • a general overview of the platform and its performance from the perspectives of the student and the teacher • lab course administration • how to provide components for remote users and how to avoid damage of ex-perimental equipment • A hands-on session, where the participants are invited to perform experiments using their laptops. Only WLAN and Flash Player are required. The presentations, notes pages and material for the hands-on session will be available at http://openlabs.bth.se/electronics/tutorial. Please download it and bring it to the tutorial.

  • 109. Gustavsson, Ingvar
    INNOVATIONS 2004: World Innovations in Engineering Education and Research2004In: 2004-07-21 / [ed] Aung, Win, Arlington: iNEER , 2004, p. 163-172Chapter in book (Other academic)
    Abstract [en]

    Laboratory (lab) work is recognized as an efficient method for students to assimilate knowledge and develop skills for solving real world problems. A traditional undergraduate electronics laboratory at Blekinge Institute of Technology (BTH), Sweden, provides eight identical lab stations. Each station is equipped with a breadboard, some desktop instruments and a power supply. The Internet provides new opportunities for remote experimentation. Laboratory exercises in electrical engineering courses such as circuit theory and basic electronics can be performed remotely using real equipment. Experiments on electrical circuits have been conducted over the Internet using experimental hardware located in a small closed room at BTH. This tiny laboratory provides one lab station equipped with computer-based instruments and a remotely controlled switch matrix to replace the traditional breadboard. The matrix makes it possible to make all the necessary connections to form a circuit and to connect test probes. The aim is to emulate a traditional laboratory. This paper describes the remote laboratory implemented and compares it with a traditional one at BTH.

  • 110. Gustavsson, Ingvar
    et al.
    Nilsson, Kristian
    , Johan Zackrisson
    A tutorial on the VISIR Open Laboratory Platform and an invitation to join the VISIR Community2009Conference paper (Other academic)
    Abstract [en]

    A local instructional laboratory for electrical experiments can be opened for remote ac-cess using the VISIR Open Laboratory Platform. A VISIR Open Laboratory is a server/client application enabling students to perform physical electrical experiments within limits set by the teacher over the internet using a web browser 24/7. Virtual front panels and a virtual breadboard displayed on the client PCs are used to control the physical equipment connected to the server. The server is an online workbench giving the students the impression that they are working in a real laboratory. Such a workbench supplements a local laboratory equipped with workbenches comprising oscilloscope, function generator, multi-meter, triple power supply, and a solderless breadboard. Apart from Blekinge Institute of Technology in Sweden, where the platform has been created two universities, University of Deusto in Spain and FH Campus Wien in Aus-tria, have already implemented replicas of the online workbench at BTH and use them in their regular education. Other universities are ready to start. It is easy for teachers to introduce their own existing laboratory exercises. A modem connection and a web browser with Flash player are sufficient for the student. The software required to set up such a workbench has been published under a GNU GPL licence. Apart from a standard PC the hardware required to join the VISIR Com-munity and implement an online workbench is a PXI chassis containing instruments and a switching matrix for circuit wiring. The components to be used by the students are to be provided by the teachers and are installed in the matrix. Universities, schools and other teaching organizations are invited to participate and open their local laboratories for remote access in order to be able to produce engineers with a solid and documented laboratory experience but without significantly increased cost per student. This tutorial is divided into four parts: • a general overview of the platform and its performance from the perspectives of the student and the teacher and a presentation of how University of Deusto in Spain uses their VISIR workbench • a mouse-cursor-on session, where the participants are invited to perform ex-periments using their laptops. Only WLAN and Flash Player are required. • course administration • how to provide components for remote users and how to avoid damage of ex-perimental equipment

  • 111. Gustavsson, Ingvar
    et al.
    Nilsson, Kristian
    Lagö, Thomas L
    The VISIR Open Lab Platform2009Conference paper (Other academic)
    Abstract [en]

    The VISIR Open Lab Platform is a client/server application enabling learners to perform physical electrical experiments over the Internet using a web browser. Virtual front panels and a virtual breadboard displayed on the client PCs are used to control the physical equipment giving the learners the impression that they are working in a real laboratory.

  • 112. Gustavsson, Ingvar
    et al.
    Norlin, Börje
    A Flexible Circuit Analysis Course2004Conference paper (Refereed)
    Abstract [en]

    Blekinge Institute of Technology (BTH) and Mid Sweden University offer a flexible circuit analysis course for Initial Professional Development and Continuing Engineering Education. The course material is used on campus. A combination of synchronous and asynchronous distance learning activities is used. Asynchronous video presentations, on-line classes and on-line laboratory sessions are provided. This paper presents the course, its aims and components and discusses relevant implementation details.

  • 113. Gustavsson, Ingvar
    et al.
    Olsson, Thomas
    Åkesson, Henrik
    Håkansson, Lars
    A Remote Electronics Laboratory for Physical Experiments using Virtual Breadboards2005Conference paper (Refereed)
    Abstract [en]

    In traditional university laboratories students conduct experiments under the supervision of an instructor. A remotely-operated laboratory for undergraduate education in electrical engineering which emulates a traditional laboratory has been set up by Blekinge Institute of Technology (hereafter referred to as BTH), Ronneby, Sweden. The laboratory is a client/server application and the Internet is used as the communication infrastructure. Most remote laboratories elsewhere are used for fixed experiments but in the BTH laboratory students around the world can assemble circuits simultaneously from electronic components in much the same way as they do in a traditional laboratory. The teacher or a member of the laboratory staff mounts the components to be used in the lab sessions in a circuit assembly robot in the experiment server in Ronneby. Students use the mouse to connect some of the corresponding virtual components on a virtual breadboard displayed on the client PC. Students thus control the robot by means of the wiring on the virtual breadboard. Virtual instrument front panels are used to control and read the instruments by means of remote control. To avoid potentially serious student mistakes e.g. overloading a component the teacher can preset limits to the source voltages which are accessible to students. The teacher can also restrict student circuits by, for example, dictating minimum impedance in loops created with aid of the components provided. The number of nodes provided on the virtual breadboard is adequate for experiments in undergraduate education. The laboratory is always open and can be used by registered students and guest users alike. The time-sharing scheme used allows simultaneous access for up to 8 client PCs. A 56 kbit/s modem and MS Internet Explorer are all that are required. The client software can be downloaded from the laboratory web site at http://distanslabserver.its.bth.se/. This paper discusses the remotely operated laboratory at BTH; it focuses on the virtual breadboard.

  • 114. Gustavsson, Ingvar
    et al.
    Pettersson, Mats
    Håkansson, Lars
    Lagö, Thomas L
    Claesson, Ingvar
    Gör ingenjörsutbildningen attraktiv genom att öka det experimentella inslaget2008Conference paper (Other academic)
    Abstract [sv]

    Många idéer till hur man skall få fler ungdomar att välja ingenjörsyrket har diskuterats och provats men tyvärr utan större framgång. En ny ingrediens kan vara att öka det experimentella inslaget, något som ändå måste göras av andra skäl, varav ett är hållbar utveckling. Det är känt att genom experiment kan man lära känna naturens principer. Ingenjörer är de yrkesutövare som konstruerar många av de nyttigheter som bär upp vår civilisation. Vi använder teorier/modeller som verktyg, men dessa räcker inte alltid, utan man måste få experimentera och bygga prototyper samt verifiera. Den allmänna meningen bland lärare och andra initierade bedömare har hittills varit att laborationer är nödvändiga men lite sägs om vad de förväntas ge. Få lärosäten producerar ingenjörer med dokumenterad erfarenhet av laborativt arbete. Lärandemål för laborationer har saknats men de senaste åren har sådana börjat definieras. Under senare decennier har undervisningsanslagen heller inte räknats upp i takt med studenttillströmningen. Eftersom laborativ undervisning är kostsam per student har lärosätena valt att reducera antalet laborationer, men Internets intåg ger nya möjligheter att öppna laboratorier för fjärrstyrning och låta studenter experimentera själva, utan risk att skada sig själva eller utrustningen. Studenter får således nya möjligheter att organisera sina studier i enlighet med vad Bolognaprocessen kräver och lärosäten kan utnyttja laboratorierna mera effektivt. Vi kan öka det experimentella inslaget i undervisningen. Internationellt samarbete både avseende läromedel och experimentell utrustning ser ut att ge möjlighet att sänka de löpande kostnaderna till den grad att det experimentella inslaget kan ökas väsentligt inom befintliga anslagsramar, även om den initiala kostnaden för den forskning som först krävs då inte är inräknad. Avdelningen för signalbehandling, ASB, vid BTH har öppnat övningslaboratorier för ellära och mekaniska vibrationsexperiment för fjärrstyrning. Båda används i reguljär undervisning sedan några år. Ett unikt användargränssnitt gör det möjligt att från valfriplats styra och manövrera experimentutrustning på samma sätt som i laboratorielokalerna. Studenterna får möjlighet att i förväg bekanta sig med instrumenten och utföra föreskrivna experiment enskilt eller tillsammans med andra. Dessa öppna laboratorier ger möjlighet att inkludera praktiska uppgifter i skriftliga tentamina, förutsatt att examination kan ske i datorsal, varvid erfarenhet av laborativt arbete enkelt kan examineras för varje enskild student. ASB har startat ett projekt VISIR (Virtual Systems in Reality) som handlar om att sprida BTH:s öppna laboratoriekoncept och formulera standarder inom området. Tillhörande programvara har publicerats som öppen källkod. BTH bjuder in andra lärosäten att delta i projektet och i dess vidareutveckling mot internationella standarder. Två internationella universitet har redan öppnat kopior av elläralaboratoriet och deltar aktivt i vidareutvecklingen. ASB har nyligen blivit inbjuden av ett universitet i Australien att delta ett projekt med titeln ”Enriching Student Learning Experience through International Collaboration in Remote Laboratories”. Detta beviljade projekt är ett resultat av nya pedagogiska möjligheter, som diskuteras i detta bidrag. ASB söker samarbete med pedagoger och andra forskare intresserade av experimentella inslag i ingenjörsutbildningen. Lärandemål för laborativt arbete, öppna laboratorier och internationellt samarbete kan bli ingredienser i en moderniserad och attraktiv ingenjörsutbildning.

  • 115. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Bartunek, Josef Ström
    Nilsson, Kristian
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    Telemanipulator for Remote Wiring of Electrical Circuits2008Conference paper (Refereed)
    Abstract [en]

    Nowadays, students want extended access to learning resources and increased freedom to organize their learning activities. Remote access to laboratories enables students to perform physical experiments on their own 24/7. It is easy to control most electronic instruments remotely but some kind of telemanipulator is often required. The Signal Processing Department (ASB) at Blekinge Institute of Technology (BTH) has created an online lab workbench for electrical experiments, mimicking and supplementing workbenches in local laboratories. Students being at home can, for example, use the online workbench in order to prepare themselves for supervised lab sessions and/or participate in such sessions taking place in a local laboratory. A virtual breadboard is used to control a telemanipulator (switching matrix) performing the circuit wiring. Together with virtual front panels depicting the front panels of the desktop instruments, it gives distant students the impression that they are working in a real laboratory. This paper describes the virtual breadboard and switching matrix combination, which can be used in many switching applications.

  • 116. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Bartunek, Josef Ström
    Åkesson, Henrik
    Håkansson, Lars
    Lagö, Thomas L
    An Instructional Electronics Laboratory Opened for Remote Operation and Control2006Conference paper (Refereed)
    Abstract [en]

    Blekinge Institute of Technology in Sweden has opened a local instructional laboratory for undergraduate education in electrical and electronic engineering for remote operation and control 24/7 as a complement and a supplement to traditional laboratories. It is equipped with a unique virtual interface enabling students to recognize on their own computer screen the desktop instruments and the breadboard most of them have already used in the local laboratory. The open laboratory is used in regular courses in circuit analysis for distant learning students dispersed all over Sweden and for campus students as well. The research is focused on what is perceived to be the greatest challenge, to give students laboratory experience that is as genuine as possible despite the lack of direct contact with the actual lab hardware. The goal is to produce an open international standard in cooperation with universities and other organizations around the world.

  • 117. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Håkansson, Lars
    Distributed Laboratories Based on Open Source Technologies2007In: 2007-07-23 / [ed] Garcia-Zubia, L. Gomes and J., Bilbao: University of Deusto , 2007, p. 247-267Chapter in book (Refereed)
    Abstract [en]

    This chapter discusses the general principles of remote laboratories. It focuses on the experimental and hardware aspects of the innovation. Access methods, protocols, and new web technologies such as Web 2.0 have been covered elsewhere. A remote laboratory project was started in 1999 at Blekinge Institute of Technology (hereafter referred to as BTH) in Sweden to ascertain if it is feasible to design a remote electronics laboratory which could function as a supplement to local instructional laboratories and provide students with free access to experimental equipment. Today, there are two laboratories online, one for electronics and one for signal processing. These are used as examples in the ensuing discussion. The BTH Open Laboratory concept evolved over a number of years. Its object is to add a remote operation option to traditional instructional laboratories thereby making the latter more accessible. This option is equipped with a unique interface enabling students to recognize on their own computer screen the instruments and other equipment which most of them have used in the local laboratory. The research is focused on what is considered to be the greatest challenge in engineering education today, i.e. to give students a laboratory experience that is as genuine as possible without direct contact with the actual lab hardware while at the same time allowing teachers to use standard equipment and readily available learning material. The winners are not only students and teachers, but also universities, which will be able to share distributed laboratories. Finally, the chapter presents some ideas about standards for primarily distributed electronics laboratories based on IVI (Interchangeable Virtual Instruments).

  • 118. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    The VISIR project – an Open Source Software Initiative for Distributed Online Laboratories2007Conference paper (Refereed)
    Abstract [en]

    Blekinge Institute of Technology (BTH) in Sweden has started a project known as VISIR (Virtual Instrument Systems in Reality) together with National Instruments in USA and Axiom EduTech in Sweden to disseminate an online laboratory concept created at BTH using open source technologies in collaboration with other universities and organizations. The concept is about adding a remote operation option to traditional instructional laboratories to make them more accessible, irrespective of whether the students are on campus or mainly off campus. The BTH option is equipped with a unique interface enabling students to recognize on their own computer screen the instruments and other equipment most of them have previously used in the local laboratory. The first remote control option implemented is for an electronics laboratory and the second one is for a signal processing laboratory with emphasis on mechanical vibration experiments. The electronics lab option features remote circuit wiring using a virtual breadboard and a relay switching matrix combination. The goal is an international standard, enabling teams worldwide to expand and develop jointly this powerful approach into distributed online laboratories by using standardized software such as IVI (Interchangeable Virtual Instruments) and equipment platforms such as PXI (PCI eXtensions for Instrumentation) and LXI (LAN eXtensions for Instrumentation).

  • 119. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Nilsson, Kristian
    Garcia-Zubia, Javier
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    A Flexible Instructional Electronics Laboratory with Local and Remote Lab Workbenches in a Grid2008Conference paper (Refereed)
    Abstract [en]

    The Signal Processing Department (ASB) at Blekinge Institute of Technology (BTH) has created two online lab workbenches, one for electrical experiments and one for mechanical vibration experiments, mimicking and supplementing workbenches in traditional labo-ratories. Since some years, the workbenches are used concurrently with on-site ones in regular supervised lab sessions. The students are also free to use them on their own around the clock e.g. for preparation. The electronic workbench can be used simultane-ously by many students. The aim of a project known as VISIR (Virtual Systems in Reality) founded by ASB at the end of 2006, is disseminating the online lab workbenches using open source technologies. The goal is to create a template for a grid laboratory where the nodes are workbenches for electrical ex-periments, located at different universities. This paper focuses on standards, pedagogical aspects, and measurement procedure requirements.

  • 120. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Nilsson, Kristian
    Garcia-Zubia, Javier
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    A Flexible Instructional Electronics Laboratory with Local and Remote Lab Workbenches in a Grid2008In: International Journal of Online Engineering, ISSN 1868-1646, E-ISSN 1861-2121, Vol. 4, no 2, p. 12-16Article in journal (Refereed)
    Abstract [en]

    The Signal Processing Department (ASB) at Blekinge Institute of Technology (BTH) has created two online lab workbenches; one for electrical experiments and one for mechanical vibration experiments, mimicking and supplementing workbenches in traditional laboratories. For several years now, the workbenches have been used concurrently with on-site ones in regular, supervised lab sessions. The students are encouraged to use them on a 24/7 basis for example, in preparation for supervised sessions. The electronic workbench can be used simultaneously by many students. The aim of a project known as VISIR (Virtual Systems in Reality) founded by ASB at the end of 2006, is to disseminate the online lab workbenches using open source technologies. The goal is to create a template for a grid laboratory where the nodes are workbenches for electrical experiments, located at different universities. This paper focuses on standards, pedagogical aspects, and measurement procedure requirements.

  • 121. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Olsson, Thomas
    Traditional Lab Sessions in a Remote Laboratory for Circuit Analysis2004Conference paper (Refereed)
    Abstract [en]

    Traditional lab sessions are performed in many local university laboratories. Emulating a local laboratory, a remote laboratory for courses in circuit analysis and electronics has been set up at Blekinge Institute of Technology in Ronneby, Sweden. Students in different places around the globe can participate in lab sessions in which up to eight client PCs can be connected simultaneously to an experiment server via the Internet; students can also perform experiments individually and around the clock whenever the server is not fully occupied. Universities or other teaching organizations which make use of the laboratory for teaching purposes can use learning material in the language of their choice. The laboratory is always open and can be used by guest users outside regular lab sessions. The address of the web site is: http://distanslabserver.its.bth.se/.

  • 122. Gustavsson, Ingvar
    et al.
    Zackrisson, Johan
    Åkesson, Henrik
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    Remote Operation and Control of Traditional Laboratory Equipment2006In: International Journal of Online Engineering, ISSN 1868-1646, E-ISSN 1861-2121, Vol. 2, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Physical experiments are indispensable for developing skills to deal with physical processes and instrumentation. The Internet provides new possibilities for universities and other teaching organizations to share laboratories and increase the number of lab sessions without incurring any increase in cost. Blekinge Institute of Technology in Sweden has opened a traditional electronics laboratory for remote operation and control 24/7; it is the first of its kind. The laboratory is equipped with a unique virtual interface enabling students to recognize on their own computer screen the desktop instruments and the breadboard they have already used in the local laboratory. The research is focused on what is perceived to be the greatest challenge, i.e. to give the student laboratory experience that is as genuine as possible despite the lack of direct contact with the actual lab hardware at the same time as it allows the teacher to use existing equipment and teaching material. The goal is to produce an open international standard.

  • 123. Gustavsson, Ingvar
    et al.
    Åkesson, Henrik
    A Remote Laboratory providing Teacher-defined Sessions2004Conference paper (Other academic)
    Abstract [en]

    An experiment server emulating a traditional university laboratory for courses in Circuit Analysis and Electronics has been set up at Blekinge Institute of Technology (BTH) in Ronneby, Sweden. Students in different places around the globe can participate in lab sessions allowing up to eight client PCs to be connected to the server via the Internet simultaneously or they can perform experiments alone without supervision around the clock when the laboratory is not fully occupied. Regular sessions are supervised by one instructor using MS Netmeeting or other means of communication. The laboratory pro-vides common instruments and the user interface is in English but universities or other learning organizations engaging the laboratory for their courses can use lab instruction manuals and other learning material in a language of their choice. In a traditional labora-tory the students use a breadboard and components handed over by the instructor to form the circuits assigned and connect the test probes. In the remote laboratory a virtual breadboard and photographs of the components provided in each session are displayed on the client PC screen at startup. The students use the mouse to locate each virtual component on the breadboard and do the wiring to assemble the circuits. The teacher or someone in the laboratory staff mounts the corresponding real components in sockets in a switching matrix in Ronneby controlled by the virtual breadboard routine before the session. The instruments provided are computer-based and have virtual front panels. The time sharing scheme used to allow simultaneous access to one server imposes re-strictions on the time period allowed for each experiment but in courses in electronics the time constants involved can without any inconvenience be selected within a proper range. The number of nodes on the virtual breadboard is also limited due to the hard-ware complexity of the switching matrix but is adequate for experiments in undergradu-ate education. Apart from the fact that each student or student team is working in a vir-tual environment without face to face contact with the instructor or other students in the laboratory the only difference compared to a traditional lab session is that it is not pos-sible for a student to manipulate the components and the wires with their fingers. The laboratory is always open and can be used by everybody outside regular lab sessions. Only a 56 kbit/s modem and MS Internet Explorer are required. The client software can be downloaded from the laboratory web site. The address of the homepage of the ex-periment server is: http://distanslabserver.its.bth.se/. In this paper laboratory sessions in the remote laboratory will be compared with sessions in a traditional laboratory.

  • 124. Haan, Jan Mark de
    Convergence and Complexity Analysis of Delayless Subband Adaptive Filters2004Report (Other academic)
    Abstract [en]

    Subband adaptive filters have been proposed to circumvent the drawbacks of slow convergence and high computational complexity associated with time domain adaptive filters. Subband processing introduces transmission delays and signal degradations due to aliasing effects. In order to overcome the transmission delays, delayless adaptive filtering has been introduced where the coefficient adaptation is performed in the subband domain while signal filtering is performed in fullband. In this paper convergence behavior and computational complexity of two different types of delayless adaptive filters are considered. Both open loop and closed loop configurations are studied. The theoretical results are compared with simulations of algorithms in a system identification scenario.

  • 125. Haan, Jan Mark de
    et al.
    Nordholm, Sven
    Claesson, Ingvar
    Design of Nonuniform Filter Banks with Frequency Domain Criteria2004Report (Other academic)
    Abstract [en]

    This paper presents methods for the design of nonuniform filter banks. The filter bank structure is obtained from an uniformly modulated filter bank by using an allpass transform which has a lossless frequency function and a nonlinear phase function. The proposed design methods include linear and quadratic frequency domain criteria and linear constraints. Considered applications are subband adaptive filtering and subband coding. Analysis filter banks and synthesis filter banks are designed in two subsequent stages, and design objectives include minimization of subband aliasing as well as reconstruction output residual aliasing components on an individual basis. This way to formulate design objectives is appropriate for filter banks used in subband adaptive filtering. Other design objectives are to optimize the overall filter bank response for low amplitude and phase distortion. Designs with phase compensation for linear phase overall response are included. Examples are included of filter banks with increasing bandwidth.

  • 126.
    HAIDER, KAMRAN
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Peak to Average Ratio Reduction in Wireless OFDM Communication Systems2006Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Future mobile communications systems reaching for ever increasing data rates require higher bandwidths than those typical used in today’s cellular systems. By going to higher bandwidth the (for low bandwidth) flat fading radio channel becomes frequency selective and time dispersive. Due to its inherent robustness against time dispersion Orthogonal Frequency Division Multiplex (OFDM) is an attractive candidate for such future mobile communication systems. OFDM partitions the available bandwidth into many subchannels with much lower bandwidth. Such a narrowband subchannel experiences now due to its low bandwidth an almost flat fading leading in addition to above mentioned robustness also to simple implementations. However, one potential drawback with OFDM modulation is the high Peak to Average Ratio (PAR) of the transmitted signal: The signal transmitted by the OFDM system is the superposition of all signals transmitted in the narrowband subchannels. The transmit signal has then due to the central limit theorem a Gaussian distribution leading to high peak values compared to the average power. A system design not taking this into account will have a high clip rate: Each signal sample that is beyond the saturation limit of the power amplifier suffers either clipping to this limit value or other non-linear distortion, both creating additional bit errors in the receiver. One possibility to avoid clipping is to design the system for very high signal peaks. However, this approach leads to very high power consumption (since the power amplifier must have high supply rails) and also complex power amplifiers. The preferred solution is therefore to apply digital signal processing that reduces such high peak values in the transmitted signal thus avoiding clipping. These methods are commonly referred to as PAR reduction. PAR reduction methods can be categorized into transparent methods – here the receiver is not aware of the reduction scheme applied by the transmitter – and non-transparent methods where the receiver needs to know the PAR algorithm applied by the transmitter. This master thesis would focus on transparent PAR reduction algorithms. The performance of PAR reduction method will be analysed both with and without the PSD constrained. The effect of error power on data tones due to clipping will be investigated in this report.

  • 127. Haider, Kamran
    et al.
    Mohammed, Abbas
    Baldmair, Robert
    Performance Evaluation of the Active Set Algorithm for Peak to Average Ratio Reduction in Wireless OFDM Communication Systems2006Conference paper (Refereed)
    Abstract [en]

    For high speed data transmission over multipath fading channels Orthogonal Frequency Division Multiplexing (OFDM) can be a spectrally efficient multicarrier modulation technique. All OFDM systems suffer from large peak-to-average-power ratio (PAR), which can lead to power inefficiency and nonlinear distortion at the RF portion of the transmitter. Tone reservation method uses reserved tones to generate a peak-canceling signal to lower the PAR of a transmit OFDM block. This paper investigates the recently proposed active-set tone reservation method, for complex-baseband signals, to reduce the PAR in wireless and broadcast systems. When PAR reduction is applied on an OFDM symbol and its PAR level still exceeds the target PAR after reduction this OFDM symbol suffers clipping. Infrequency domain clipping energy spreads across all tones and acts as error power. Simulations are performed to investigate the error power on data tones after active-set method.

  • 128.
    Haider, Muhammad Abdur Rahman
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Bhatti, Abu Bakar
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Kirmani, Ammar Ahmad
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Radio Resource Management In 3G UMTS Networks2007Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Universal Mobile Telecommunication System (UMTS) is a third generation mobile communication system, designed to support a wide range of applications with different quality of service (QoS) profiles. This 3G system has capability of transporting wideband and high bit rate multimedia services along with traditional cellular telephony services e.g voice, messaging etc. To provide these services with better quality of service and enhance the performance of wireless network, management of radio resources is necessary. To do this, UMTS offer many radio resource management (RRM) strategies. These RRM techniques play important role in providing different services with better quality, keep the end user happy and make the network stable. In our thesis, our main objective is to explore some RRM strategies and understand their practical importance by simulating some RRM algorithms. First we start with UMTS overview and learn some important concept about UMTS architecture. Then we go deep into physical layer of UMTS. After getting strong concept of UMTS radio architecture and procedures, we worked on different RRM techniques and in the end we analyze two power control algorithms to understand and get some practical experience of actual RRM strategies, because power control is the important most and critical part of RRM techniques due to interference limited nature of CDMA systems.

  • 129.
    Hamid, Mohamed
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    DYNAMIC SPECTRUM ACCESS IN COGNITIVE RADIO NETWORKS: ASPECTS OF MAC LAYER SENSING2008Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Over the past two decades wireless communication systems have been showing great revolution and rapid growth. Therefore, the standardization agencies together with wireless researchers and industry have been working on new specifications and standards to face the high demand for wireless communication systems. One of the most critical issues regarding wireless networks regulation agencies and researchers are thinking about is how to manage the available electromagnetic radio spectrum in a way that satisfies the needs of these growing wireless systems both economically and technically especially with the recent crowding in the available spectrum. Hence, building cognitive radio systems support dynamic access to the available spectrum has appeared recently as a novel solution for the wireless system huge expansion. In this thesis 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 the pre-mentioned sensing schemes has been held via two performance metrics, achieved spectrum utilization factor and idle channel search delay. The simulation results show that with proactive sensing adapted periods we achieve the best performance but with an observable over head computational tasks to be done by the network nodes which reflects the extent of complexity we need in our network nodes. On the other hand reactive sensing is the simplest sensing schemes with the worst achieved performance.

  • 130. Hamid, Mohamed
    et al.
    Mohammed, Abbas
    MAC Layer Sensing Schemes in Cognitive Radio Networks2009Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate the MAC layer sensing schemes in cognitive radio. Reactive and proactive sensing are both considered and assessed. The assessment of these sensing has been held via the obtained idle channel search delay in each case. The simulation results conclude that with proactive sensing we achieve lower idle channel search delay as compared with reactive sensing, but on the other hand we waste some of our resources in sensing which is higher than in reactive scheme. Thus, in proactive sensing we have observable computational tasks to be done by the network nodes.

  • 131. Hansson, H
    et al.
    Blomstrand, F
    Khatibi, Siamak
    Olsson, T
    Glutamate induced astroglial swelling1997In: On astrocytes and glutamate neurotransmission: New waves in brain information processing, Neuroscience Intelligence Unit, Springer, R.G. Landes Company , 1997, p. 106-120Chapter in book (Refereed)
  • 132.
    Hodzic, Armin
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Research in SAR reduction by changing composition of phone casing2007Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    This thesis is a research conducted to find out if the specific absorption rate (SAR), imposed on the human head from cellular phones, can be reduced without having an significant impact on the overall performance and reception of the phone. The SAR values are influenced by various different variables like, type and size of the antenna, position of the antenna relative to human head, radiated power from the antenna, distance and angle from human head and finally the material covering the phone. The methodologies that will be used are to investigate three different approaches to SAR reduction. First approach is to investigate if the size and type of the material shielding the human head have significant impact on the SAR radiation, second approach is to investigate if the angle of the phone in relation to human head have significant impact and as the third approach is to investigate if it is possible to change the composition of the material which would ultimately lead to SAR reduction. Electric properties of the material are described by two variables conductivity and permittivity, and in the third part of the thesis I will change these two variables and then investigate how the SAR values change. Result will be presented as a 3D graph and it will directly present how SAR values relate to the material used as a phone casing. The distance and antenna variations will not be investigated. The distance values will be fixed to 2.5 cm from the human head and the antenna length will be quarter of the 900 MHz wave length. The investigations will be performed in a simulation program called FEMLAB and the results will be showed in text and figures.

  • 133. Holland, Ian
    et al.
    Zepernick, Hans-Jürgen
    Caldera, Manora
    Soft Combining for Hybrid ARQ2005In: Electronics Letters, ISSN 0013-5194 , Vol. 41, no 22, p. 1230-1231Article in journal (Refereed)
    Abstract [en]

    A soft combining approach utilising symbol-by-symbol maximum a posteriori probability decoding is proposed for hybrid automatic repeat request schemes. In comparison to an existing soft combining approach, significant reductions in post-decoding bit error rate can be obtained without sacrificing the throughput efficiency. This is achieved with the proposed method by accumulating the signal-to-noise ratio at the channel output on each additional retransmission, for use in calculating extrinsic log-likelihood ratios on subsequent decoding attempts.

  • 134.
    Hossain, Firoz
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Sohab, Abu-Shadat-Mohammad
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Mathematical Modelling of Call Admission Control in WCDMA Network2007Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    WCDMA is an interference limited multiple access technique .It is widely used in the 3rd generation mobile networks like UMTS. When a new call arrives in the system to get admission, it checks whether the call is admitted or not based on some parameters like signal to interference ratio (SIR), transmission power of the Node B and the air interface load .If the call is accepted this will increase some interference to the ongoing calls. This new interference would degrade the ongoing calls and this will also add some extra load which may also lead to the exceeding capacity. So that the system has to decide this admission policy in a systematic way that all the users should maintain their communication with guaranteed quality of service. This decision making algorithm belongs to the radio resource management functionalities of the Radio Network Controller (RNC) in a WCDMA based UMTS network. This thesis paper focuses on the mathematical representation of the call admission control in an interference based environment. There is also a comparative study with different methods.

  • 135. Hult, Tommy
    Novel Applications of Space-Time Processing for Wireless Systems2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Space-time processing techniques have emerged as one of the most promising areas of research and development in wireless communications. Space-time processing signifies the signal processing performed on a system consisting of several antenna elements, whose signals are processed adaptively in order to exploit both the spatial (space) and temporal (time) dimensions of the radio channel. Space-time processing techniques can be applied at the transmitter, the receiver or both. The use of space-time signal processing can significantly improve average signal power, mitigating fading, and reduce inter-symbol interference and co-channel interference. This can significantly improve capacity, coverage and quality of wireless systems. In this thesis we expand the scope of space-time processing by proposing novel applications in wireless communications. These include the reduction of possibly harmful electromagnetic radiation from mobile phones, enhancing link quality for Bluetooth links in indoor office environments, and increasing the spectral efficiency of satellite communication systems. Several studies have been conducted on the effects of radiation from hand held mobile phones. The amount of radiation emitted from most mobile phones is minute, but given the close proximity of the phone to the head it might be possible for the radiation to cause harm. In Part I, we suggest the use of adaptive signal processing algorithms combined with a MIMO (multiple-input multiple output) antenna system to decrease the electromagnetic radiation inside a certain volume in space (e.g. the the human head). In addition, we investigate the impact of MIMO antenna parameters, carrier frequency and power constraint on the performance of the system. Over the last decade there has been an explosive growth in the use of wireless mobile communications. Today we find users with mobile phones, wireless PDA's, MP3 players, and wireless headphones to connect to these devices. In Part II, we investigate the wave propagation effects of a short-range wireless device, such as the Bluethooth technology. Specifically, we assess the fading phenomenon for Bluetooth link in indoor office environment by simulation of different propagation scenarios, and use measurement results to confirm our findings. In addition, we investigate the improvement in performance resulting from receiver diversity gain of a system employing multiple receive antennas with various combining techniques. The need for high-speed, high-quality bandwidth efficient mobile communications is constantly increasing. In Part III, we address the potential gain of using MIMO antenna system in combination with OFDM (orthogonal frequency division multiplexing) in order to increase the bandwidth efficiency in satellite communication systems. In particular, we consider the increase in channel capacity that is possible by exploiting satellite and polarization diversity. In addition we investigate the effect of using different compact MIMO polarization antenna configurations and power control on the information theoretic capacity of the total transmission channel of the satellite system.

  • 136. Hult, Tommy
    Space-Time Processing Applications for Wireless Communications2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wireless mobile communication networks are rapidly growing at an incredible rate around the world and a number of improved and emerging technologies are seen to be critical to the improved economics and performance of these networks. The technical revolution and continuing growth of mobile radio communication systems has been made possible by extraordinary advances in the related fields of digital computing, high-speed circuit technology, the Internet and, of course, digital signal processing. Improved third generation (3G) and future generation wireless communication systems must support a substantially wider and enhanced range of services with respect to those supported by second generation and basic 3G systems. The never-ending quest for such personal and multimedia services, however, demands technologies operating at higher data rates and broader bandwidths. This combined with the unpredictability and randomness of the mobile propagation channel has created many new technically challenging problems for which innovative, adaptive and advanced signal processing techniques may offer new and better solutions. Space-time processing techniques have emerged as one of the most promising areas of research and development in wireless communications for the efficient utilization of the physical mobile radio propagation channel. Space-time processing signifies the signal processing performed on a system consisting of several antenna elements, whose signals are processed adaptively in order to exploit both the spatial (space) and temporal (time) dimensions of the radio channel. This can significantly improve the capacity, coverage, quality and energy efficiency of wireless systems. This thesis expands the scope of space-time processing by proposing novel applications in wireless communication systems. These include the reduction of possibly harmful electromagnetic radiation from mobile phones, enhancing the quality of Bluetooth links in indoor office environments, increasing the spectral efficiency of satellite and the novel high altitude platforms (HAPs) communication systems, enhancing the coverage and capacity of integrated multiple-HAP 3G systems, and improving the energy efficiency of cooperative wireless sensor networks. The performance of these systems is assessed by theoretical analysis, by computer simulations under a range of propagation environments including realistic channel models, advanced commercial electromagnetic modeling software, and a proposed novel multi-channel simulator suitable for various space-time applications.

  • 137. Hult, Tommy
    WCDMA Uplink Interference Assessment from Multiple High Altitude Platform Configurations2008In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. vol. 2008, no Special Issue on Advanced Communication Techniques and Applications for High-Altitude PlatformsArticle in journal (Refereed)
    Abstract [en]

    We investigate the possibility of multiple high altitude platform (HAP) coverage of a common cell area using a wideband code division multiple access (WCDMA) system. In particular, we study the uplink system performance of the system. The results show that depending on the traffic demand and the type of service used, there is a possibility of deploying 3-6 HAPs covering the same cell area. The results also show the effect of cell radius on performance and the position of the multiple HAP base stations which give the worst performance.

  • 138. Hult, Tommy
    et al.
    Falletti, Emanuela
    Mohammed, Abbas
    Sellone, Fabrizio
    Multi-antenna Channel Model for Space-Polarization Systems2007Conference paper (Refereed)
  • 139. Hult, Tommy
    et al.
    Falletti, Emanuela
    Mohammed, Abbas
    Sellone, Fabrizio
    The Impact of Depolarizing Effects on a Multiple HAP System Employing Polarization Diversity2007Conference paper (Refereed)
  • 140. Hult, Tommy
    et al.
    Grace, David
    Mohammed, Abbas
    WCDMA Capacity and Coverage Enhancement from Multiple High Altitude Platform Configuration2007Conference paper (Refereed)
  • 141. Hult, Tommy
    et al.
    Mohammed, Abbas
    A Combined Satellite Diversity and Compact MIMO Antenna Configurations for High Data Rate Communications2007Conference paper (Refereed)
  • 142. Hult, Tommy
    et al.
    Mohammed, Abbas
    Active Signal Processing Algorithms for Controlling Electromagnetic Fields: a Tutorial2008Conference paper (Refereed)
  • 143. Hult, Tommy
    et al.
    Mohammed, Abbas
    Active Suppression of Electromagnetic Fields2004Conference paper (Refereed)
  • 144. Hult, Tommy
    et al.
    Mohammed, Abbas
    Assessment of a HAP Diversity System Employing Compact MIMO-Tetrahedron Antenna2007Conference paper (Other academic)
  • 145. Hult, Tommy
    et al.
    Mohammed, Abbas
    Assessment of Multipath Propagation for a 2.4 GHz Short-Range Wireless Communication System2007Conference paper (Refereed)
    Abstract [en]

    In this paper we assess the multipath propagation effects of a short-range wireless device operating at 2.4 GHz in an indoor office environment. The investigations are carried out using FEM simulations and measurement trials for NLOS and LOS propagation scenarios. The FEM simulations will also be used for assessing the influence on propagation when doors are opened or closed. Finally, we investigate a single-input multiple-output (SIMO) antenna receive diversity system utilizing different combining techniques to improve the performance over a fading radio channel in a NLOS propagation environment. Simulation results show that a substantial diversity gain would be achieved by using this system. © 2007 IEEE

  • 146. Hult, Tommy
    et al.
    Mohammed, Abbas
    CAPACITY OF A SATELLITE DIVERSITY SYSTEM EMPLOYING MULTIPLE POLARIZATIONS2006Conference paper (Refereed)
    Abstract [en]

    In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with satellite diversity techniques in order to increase the data rates in satellite communication systems. Simulation results show that by exploiting the additional multiple polarization channels and satellite diversity we can achieve considerable capacity gain compared to the single satellite case.

  • 147. Hult, Tommy
    et al.
    Mohammed, Abbas
    CAPACITY OF MULTIPLE HAP SYSTEM EMPLOYING MULTIPLE POLARIZATIONS2006Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate the potential increase in capacity of HAP (High Altitude Platforms) communication systems using compact MIMO antenna array configurations in conjunction with HAP diversity techniques. In addition, we evaluate the system performance for different separation angles between HAPs. Simulation results show that the HAP diversity system provides superior performance compared to the single HAP case.

  • 148. Hult, Tommy
    et al.
    Mohammed, Abbas
    COMBINED POLARIZATION AND SATELLITE DIVERSITY FOR HIGH DATA RATE COMMUNICATIONS2006Conference paper (Refereed)
    Abstract [en]

    This paper addresses the potential gain of using multiple-input multiple-output (MIMO) principle in order to increase the bandwidth efficiency in satellite communication systems. In particular, we consider the increase in channel capacity that is possible by exploiting satellite and polarization diversity. In addition, we investigate the effect of using different compact MIMO polarization antenna configurations and power control on the information theoretic capacity of the total transmission channel of the satellite system.

  • 149. Hult, Tommy
    et al.
    Mohammed, Abbas
    Compact MIMO Antennas and HAP Diversity for Enhanced Data Rate Communications2007Conference paper (Refereed)
    Abstract [en]

    In this paper we address the potential gain of using various compact MIMO antenna array configurations in conjunction with HAP (High Altitude Platforms) diversity techniques in order to enhance 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. Simulations also show the existence of an optimum separation angle between HAPs that maximizes capacity. © 2007 IEEE.

  • 150. Hult, Tommy
    et al.
    Mohammed, Abbas
    Cooperative Beamforming for Wireless Sensor Networks2007Conference paper (Refereed)
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