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  • 51.
    Barkander, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Utvärdering av grafisk utvecklingsmiljö för programmering av signalprocessor2011Självständigt arbete på grundnivå (yrkesexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This work aims to evaluate the possibility of using a graphical programming language to develop software for a digital signal processor. A fixed-point digital signal processor called Blackfin BF-537 is used for this. Instead of using conventional programming languages, like C or assembler, for software development the possibilities to use a graphical environment to fill the same purpose are examined. The development environment primarily used is NI LabVIEW, but also the use of Mathworks Matlab Simulink is investigated. A variety of programs consisting of various signal processing operations and utilities are developed using these development environments. These include the FIR filter and the limitations of an implementation of such a filter are further investigated. Other operations such as FFT are implemented and an application of this is filtering in the frequency domain. Whether these graphical environments are able to deliver software that can utilize the power of the hardware to the same extent as the non-graphical alternatives is also questioned.

  • 52.
    Barkefors, Annea
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    3D Synthetic Aperture Technique for Ultrasonic Imaging2010Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The group for non-destructive testing at Uppsala University has recently implemented the phase shift migration method, which is a method to focus images acquired unfocused using ultrasound. However, their work has been limited to 2D data, while for many applications the gathered data is 3D. This project has extended the old implementation to 3D data. The new implementation has been done in two different ways, giving one algorithm that works fast but needs much RAM, and one algorithm that takes long time but works on smaller computers, not demanding as much memory. The fast algorithm works faster than the time it takes to acquire the raw data, which makes real-time use realistic. To test the performance of the two algorithms with respect to image improvement, both against each other and against the previous 2D implementation, a number of experiments were carried out, which showed that, apart from processing time, the two new algorithms were equal in performance. The experiments also showed that the obtained resolution in both x- and y-directions matched the theoretical discussion.

  • 53.
    Barkefors, Annea
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Adapting an MSE controller for active noise control to nonstatic noise statisticsManuskript (preprint) (Övrigt vetenskapligt)
  • 54.
    Barkefors, Annea
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Linear Quadratic Gaussian Controllers for Feedforward Active Noise Control: Pushing Performance and Moving Towards Adaptive Control2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Active noise control is a research area focused on using destructive interference of sound fields to attenuate undesired noise. Methods for active noise control are best suited for low frequency noise, as the complexity of the problem grows rapidly with frequency. Coincidentally, passive means of damping have the opposite quality in that they work better for higher frequencies and become bulky and impractical for low frequencies. Applications for active noise control range from fan noise in ducts, noise-cancelling headphones and noise in cars to propeller induced aircraft cabin noise. In this comprehensive summary, the underlying principles of active noise control are presented and the control problem is discussed. Several aspects of the control system are introduced to give an introduction to the research papers that are the basis of this licentiate thesis. The work behind the thesis is focused on a Multiple-Input Multiple-Output (MIMO) Minimal Mean Square Error (MMSE) Linear Quadratic Gaussian (LQG) feedforward controller. This controller is shown to achieve uniform damping in an extended region in space and push the upper frequency that can be controlled. The influence of different design variables has been investigated, and the properties of the control path analyzed with consideration of its ability to suppress noise of prescribed spectral properties over an extended region. In this context, it has been shown how to use the reproducibility of the primary noise path by the control path as an indication of achievable performance for a given control system. Finally, the controller has been adapted to follow changes in the primary noise statistics, an approach that seems promising to considerably raise the performance of the controller.

    Delarbeten
    1. Extending the area silenced by active noise control using multiple loudspeakers
    Öppna denna publikation i ny flik eller fönster >>Extending the area silenced by active noise control using multiple loudspeakers
    2012 (Engelska)Ingår i: Acoustics, Speech and Signal Processing (ICASSP), 2012 IEEE International Conference, 2012, s. 325-328Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Active noise control is of increasing interest in e.g. cars, but the zone of noise damping becomes limited in reverberant environments. We investigate the possibility of extending this spatial zone significantly, by using multiple control loudspeakers. MIMO feedforward controllers designed by linear quadratic control theory are here shown to increase the limiting frequency for uniform damping in a 0.3×0.3 m test area, from 200 Hz to around 600 Hz.

    Nationell ämneskategori
    Signalbehandling
    Forskningsämne
    Elektroteknik med inriktning mot signalbehandling
    Identifikatorer
    urn:nbn:se:uu:diva-181013 (URN)10.1109/ICASSP.2012.6287882 (DOI)000312381400080 ()978-1-4673-0044-5 (ISBN)
    Konferens
    IEEE International Conference on Acoustics, Speech and Signal Processing, 25-30 March, 2012 ICASSP, Kyoto, Japan
    Tillgänglig från: 2012-09-14 Skapad: 2012-09-14 Senast uppdaterad: 2014-05-07Bibliografiskt granskad
    2. MIMO design of active noise controllers for car interiors: Extending the silenced region at higher frequencies
    Öppna denna publikation i ny flik eller fönster >>MIMO design of active noise controllers for car interiors: Extending the silenced region at higher frequencies
    2012 (Engelska)Ingår i: 2012 American Control Conference, Montréal, Canada, 2012, s. 6140-6147Konferensbidrag, Publicerat paper (Refereegranskat)
    Nationell ämneskategori
    Signalbehandling
    Forskningsämne
    Elektroteknik med inriktning mot signalbehandling
    Identifikatorer
    urn:nbn:se:uu:diva-181008 (URN)
    Konferens
    2012 American Control Conference, Montréal, Canada
    Tillgänglig från: 2012-09-14 Skapad: 2012-09-14 Senast uppdaterad: 2014-05-07
    3. An investigation of a theoretical tool for predicting performance of an active noise control system.
    Öppna denna publikation i ny flik eller fönster >>An investigation of a theoretical tool for predicting performance of an active noise control system.
    2012 (Engelska)Ingår i: 19th International Congress on Sound and Vibration, ICSV19, Vilnius, Lithuania, 2012, s. 1-8Konferensbidrag, Publicerat paper (Refereegranskat)
    Nationell ämneskategori
    Signalbehandling
    Forskningsämne
    Elektroteknik med inriktning mot signalbehandling
    Identifikatorer
    urn:nbn:se:uu:diva-181014 (URN)
    Konferens
    ICSV19, Vilnius, Lithuania
    Tillgänglig från: 2012-09-14 Skapad: 2012-09-14 Senast uppdaterad: 2014-05-07
    4. Design and Analysis of Linear Quadratic Gaussian Feedforward Controllers for Active Noise Control
    Öppna denna publikation i ny flik eller fönster >>Design and Analysis of Linear Quadratic Gaussian Feedforward Controllers for Active Noise Control
    2014 (Engelska)Ingår i: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, Vol. 22, nr 12, s. 1777-1791Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    A method for sound field control applied to active noise control is presented and evaluated. The method uses Linear Quadratic Gaussian (LQG) feedforward control to find a Minimal Mean Square Error (MMSE)-optimal linear sound field controller under a causality constraint. It is obtained by solving a polynomial matrix spectral factorization and a linear (Diophantine) polynomial matrix equation. An important component in the design is the control signal penalty term of the criterion. Its use and influence is here discussed and evaluated using measured room impulse responses. The results indicate that the use of a relatively simple, frequency-weighted penalty on individual control signals provides most of the benefits obtainable by the considered more advanced alternative. We also introduce and illustrate several tools for performance analysis. An analytical expression for the attainable performance clearly reveals the performance loss generated by having to use a causal controller instead of the ideal noncausal controller. This loss is largest at low frequencies. Furthermore, we introduce a measure of the reproducibility of the target noise sound field with given control loudspeaker setups and room transfer functions. It describes how well a controller that uses an input subspace of dimension equal to the effective rank of the system is able to reproduce a target sound field. This performance measure can e.g. be used to support the selection of good combinations of placements of control loudspeakers.

    Nationell ämneskategori
    Reglerteknik
    Identifikatorer
    urn:nbn:se:uu:diva-223813 (URN)10.1109/TASLP.2014.2349856 (DOI)000341627500008 ()
    Forskningsfinansiär
    Vetenskapsrådet, 2009-5527
    Tillgänglig från: 2014-04-27 Skapad: 2014-04-27 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
    5. Adapting an MSE controller for active noise control to nonstatic noise statistics
    Öppna denna publikation i ny flik eller fönster >>Adapting an MSE controller for active noise control to nonstatic noise statistics
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Nationell ämneskategori
    Reglerteknik
    Identifikatorer
    urn:nbn:se:uu:diva-223814 (URN)
    Tillgänglig från: 2014-04-27 Skapad: 2014-04-27 Senast uppdaterad: 2014-05-07
  • 55.
    Barkefors, Annea
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Berthilsson, Simon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    An investigation of a theoretical tool for predicting performance of an active noise control system.2012Ingår i: 19th International Congress on Sound and Vibration, ICSV19, Vilnius, Lithuania, 2012, s. 1-8Konferensbidrag (Refereegranskat)
  • 56.
    Barkefors, Annea
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Berthilsson, Simon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Extending the area silenced by active noise control using multiple loudspeakers2012Ingår i: Acoustics, Speech and Signal Processing (ICASSP), 2012 IEEE International Conference, 2012, s. 325-328Konferensbidrag (Refereegranskat)
    Abstract [en]

    Active noise control is of increasing interest in e.g. cars, but the zone of noise damping becomes limited in reverberant environments. We investigate the possibility of extending this spatial zone significantly, by using multiple control loudspeakers. MIMO feedforward controllers designed by linear quadratic control theory are here shown to increase the limiting frequency for uniform damping in a 0.3×0.3 m test area, from 200 Hz to around 600 Hz.

  • 57.
    Barkefors, Annea
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Adapting an MSE controller for active noise control to nonstationary noise statistics2014Konferensbidrag (Refereegranskat)
  • 58.
    Barkefors, Annea
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Brännmark, Lars-Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Design and Analysis of Linear Quadratic Gaussian Feedforward Controllers for Active Noise Control2014Ingår i: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, Vol. 22, nr 12, s. 1777-1791Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method for sound field control applied to active noise control is presented and evaluated. The method uses Linear Quadratic Gaussian (LQG) feedforward control to find a Minimal Mean Square Error (MMSE)-optimal linear sound field controller under a causality constraint. It is obtained by solving a polynomial matrix spectral factorization and a linear (Diophantine) polynomial matrix equation. An important component in the design is the control signal penalty term of the criterion. Its use and influence is here discussed and evaluated using measured room impulse responses. The results indicate that the use of a relatively simple, frequency-weighted penalty on individual control signals provides most of the benefits obtainable by the considered more advanced alternative. We also introduce and illustrate several tools for performance analysis. An analytical expression for the attainable performance clearly reveals the performance loss generated by having to use a causal controller instead of the ideal noncausal controller. This loss is largest at low frequencies. Furthermore, we introduce a measure of the reproducibility of the target noise sound field with given control loudspeaker setups and room transfer functions. It describes how well a controller that uses an input subspace of dimension equal to the effective rank of the system is able to reproduce a target sound field. This performance measure can e.g. be used to support the selection of good combinations of placements of control loudspeakers.

  • 59. Barros, M
    et al.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Feed-forward and feedback control in astrocytes for Ca2+-based molecular communications nanonetworks2018Ingår i: IEEE/ACM Transactions on Computational Biology & Bioinformatics, ISSN 1545-5963, E-ISSN 1557-9964Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Synaptic plasticity depends on the gliotransmitters' concentration in the synaptic channel. And, an abnormal concentration of gliotransmitters is linked to neurodegenerative diseases, including Alzheimer's, Parkinson's, and epilepsy. In this paper, a theoretical investigation of the cause of the abnormal concentration of gliotransmitters and how to achieve its control is presented through a Ca2+-signalling-based molecular communications framework. A feed-forward and feedback control technique is used to manipulate IP3 values to stabilise the concentration of Ca2+ inside the astrocytes. The theoretical analysis of the given model aims i) to stabilize the Ca2+ concentration around a particular desired level in order to prevent abnormal gliotransmitters' concentration (extremely high or low concentration can result in neurodegeneration), ii) to improve the molecular communication performance that utilises Ca2+ signalling, and maintain gliotransmitters' regulation remotely. It shows that the refractory periods from Ca2+ can be maintained to lower the noise propagation resulting in smaller time-slots for bit transmission, which can also improve the delay and gain performances. The proposed approach can potentially lead to novel nanomedicine solutions for the treatment of neurodegenerative diseases, where a combination of nanotechnology and gene therapy approaches can be used to elicit the regulated Ca2+ signalling in astrocytes, ultimately improving neuronal activity.

  • 60.
    Barros, Michael Taynnan
    et al.
    TSSG, Waterford Inst Technol, Waterford, Ireland.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Set point regulation of astrocyte intracellular Ca2+ signalling2017Ingår i: Proceedings / 2017 IEEE 17Th International Conference On Nanotechnology (IEEE-NANO), 2017, s. 315-320Konferensbidrag (Refereegranskat)
    Abstract [en]

    Neurodegenerative diseases are the current centre of attention in medicine due to their increased physiological and psychological burden on the ageing society and in the other hand the lack of efficient treatment to them. In parallel, nanotechnology opens possibilities to study neurodegeneration in the molecular level and uncover cellular properties at the nanoscale that possibly allow disease control using novel system biology methods. The communication between neurons and astrocytes explains how a failure in their communication impact neuronal activity, and how the intracellular Ca2+ signalling of astrocytes can interfere in the synaptic quality. This paper presents a theoretical investigation of a feed forward and feedback control technique to regulate the quantity of IP3 that determines the concentration of Ca2+ emitted from intracellular signalling. The analysis of the control model showed that the quantity of Ca2+ signalling can be stabilised at a desired level. A potential application is to facilitate the Ca2+ concentration around this desired level to maintain cellular homoeostasis for longer periods of time, which can lead to a technology for preventing neurodegenerative diseases. The proposed approach can result in novel solutions for both nanobiology and nanomedicine development, where synthetic biology can be used to program the control functionality into the cells. Other ways of implementing such technology are also explored, including nanoparticles, implantable devices and molecular communications.

  • 61. Bartnitzek, T
    et al.
    Schönlinner, B
    Gautier, W
    Cheng, Shi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Rydberg, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Purtova, T
    Vähä-Veikkilä, T
    Ziaei, A
    Ceramic systems in package for RF and microwave2008Ingår i: IMAPS Advanced Technology Workshop on RF and Microwave Packaging, 2008Konferensbidrag (Refereegranskat)
  • 62.
    Berglund, Joel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Measurements and analysis of UDP transmissions over wireless networks2018Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The growth and expansion of modern society rely heavily upon well-functioning data communication over the internet. This phenomenon is seen at the company Net Insight where the need for transferring a large amount of data in the form of media over the internet in an effective manner is a high priority. At the moment most internet traffic in the modern world is done by the use of the internet protocol TCP (Transmission Control Protocol) instead of the simpler protocol UDP (User Datagram Protocol). Although TCP works in an excellent manner for most kinds of data communication it seems that this might not always be the case, so the use of UDP might be the better option in some occurrences. It is therefore of high interest at Net Insight to see how different types of wireless networks behave under different network circumstances when data is sent in different ways through the use of UDP. Thereby this report focuses on the measurement and analysis of how different wireless networks, specifically 4G, 5.0 GHz and 2.4 GHz WLAN networks, behaves when exposed to varied network environments where data is transmitted by the use of UDP in different ways. To perform a network-analysis data is collected, processed, and then analyzed. This network-analysis resulted in many conclusions regarding network behavior and performance for the different wireless networks.

  • 63.
    Bergsten, Tim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Motor till unikt luftvärmeväxlarsystem2011Självständigt arbete på grundnivå (yrkesexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Gtherm is an innovation company who has an unique air heat exchanger underdevelopment. The purpose of this thesis is to provide data of suitable motors for theheat exchanger and to find suitable motor suppliers.A motor specification was designed. It is an important basis for the search of suitablemotors. A compilation was made of nine motor suppliers and the suitable motorsfrom those. The compilation can be used by GTherm in their choice of suppliers andmotors.The compilation of the demands on the motor and analysis of suppliers indicated thatthere were no standard motors available to GTherms air heat exchanger. Adaptationof motor is required to meet the system requirements.Power Efficiency is the keyword for an air heat exchanger so tests were performedon prototype to calculate this. Suppliers have long delivery time for customizedmotors and because of the lack of time a borrowed standard motor was used for themeasurement. The motor was satisfactory enough to perform the tests but wouldprobably not have been selected for the production of the air heat exchanger. Basedon measured data, electric power (SFP) was calculated for the prototype. The resultsshowed that air heat exchange system was non electrical efficiency because theestimated SFP value was too high. This is probably because the prototype had gaps inthe sealing that produced air leakage.

  • 64.
    Bergström, Kristoffer
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sensor system for automated circuit board testing2019Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis investigates the possibility to automate testing of PCBs with a sensor system.  This PCB testing is today done manually by placing PCBs in a test fixture that determines its condition. This test requires an operator to wait for the test to complete and then place the PCB in the correct section. If this process can be automated time could be saved and the risk of mishandling PCBs could be reduced.

    A sensors system is made that consists of an Arduino with micro switches, hall effect sensors, a scanner and a LiDAR. The sensor system is designed to achieve a set of requirements that is needed for automation. The sensor system is meant to communicate with a robot that moves the PCBs within a test environment. This test environment is also designed in this project. For the system to communicate with a robot a program is made to inform the robot about placement of PCBs within the test environment.

    The final system is able to achieve the requirements set for automation but further investigation is needed to make this into a fully scaled automated system.

  • 65.
    Bergström, Sofia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    The Impact of Antennas on Radiolink Performance in Frequency Hopping Scenarios2018Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This paper investigates how the communication performance of frequency hopping systems are affected by the antenna parameters. The data are generated from Antenna Toolbox in Matlab for the case of two dipole antennas is free space. Non-orthogonal and orthogonal frequency hopping are used and the statistical impact from the antenna on the SINR is investigated. The results can be used to see the wave propagation margin and also see the effects of out-of-bands emissions in frequency hopping systems.

    The numerical generated model is compared to two isotropic antenna models and it shows that the isotropic models are relatively good despite its simplicity in this case. It does however not capture the spread caused by the directivity. Another model is created which mimic the numerical generated statistical distribution. This model uses the theoretical probability of a collision for both orthogonal and non-orthogonal frequency hopping. The model also uses mean values of directivity, s-parameters and the spread of the gain to calculate a statistical antenna model. This model is better than the isotropic for the tested cases and shows that it is possible to generate a statistical model.

  • 66.
    Berthilsson, Simon
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Barkefors, Annea
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Brännmark, Lars-Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Acoustical zone reproduction for car interiors using a MIMO MSE framework.2012Ingår i: AES 48th International Conference, Munich, Germany, 2012Konferensbidrag (Refereegranskat)
  • 67.
    Berthilsson, Simon
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Barkefors, Annea
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    MIMO design of active noise controllers for car interiors: Extending the silenced region at higher frequencies2012Ingår i: 2012 American Control Conference, Montréal, Canada, 2012, s. 6140-6147Konferensbidrag (Refereegranskat)
  • 68.
    Berthilsson, Simon
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Acoustic zones for aircraft seat rows2013Konferensbidrag (Refereegranskat)
  • 69. Besselink, B
    et al.
    Knorn, Steffi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Scalable input-to-state stability for performance analysis of large-scale networks2018Ingår i: IEEE Control Systems Letters, Vol. 2, nr 3, s. 507-512Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This letter investigates networks of interconnected systems and introduces the notion of “scalable input-to-state stability” (sISS). This concept is based on input-to-state stability (ISS) and can be interpreted as an extension of the well-known concept of string stability from simple line graphs to general graphs. It guarantees that the trajectories of all states are bounded at all times independently of the network's size and structure and can hence be regarded as an important performance notion. Further, sufficient conditions are derived to guarantee sISS of homogeneous networks with well-defined interconnection structures. In fact, the conditions depend on local ISS Lyapunov functions but guarantee the global condition of sISS. Hence, a first step is made towards developing suitable extensions of string stability to general networks. Two examples are discussed to illustrate the theoretical result.

  • 70. Biasson, A
    et al.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Zorzi, M
    A decentralized optimization framework for energy harvesting devices2018Ingår i: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 17, nr 11, s. 2483-2496Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Designing decentralized policies for wireless communication networks is a crucial problem, which has only been partially solved in the literature so far. In this paper, we propose a Decentralized Markov Decision Process (Dec-MDP) framework to analyze a wireless sensor network with multiple users which access a common wireless channel. We consider devices with energy harvesting capabilities, that aim at balancing the energy arrivals with the data departures and with the probability of colliding with other nodes. Over time, an access point triggers a SYNC slot, wherein it recomputes the optimal transmission parameters of the whole network, and distributes this information. Every node receives its own policy, which specifies how it should access the channel in the future, and, thereafter, proceeds in a fully decentralized fashion, with no interactions with other entities in the network. We propose a multi-layer Markov model, where an external MDP manages the jumps between SYNC slots, and an internal Dec-MDP computes the optimal policy in the short term. We numerically show that, because of the harvesting, stationary policies are suboptimal in energy harvesting scenarios, and the optimal trade-off lies between an orthogonal and a random access system.

  • 71.
    Biasson, Alessandro
    et al.
    Univ Padua, Dept Informat Engn, Via Gradenigo 6b, I-35131 Padua, Italy..
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Zorzi, Michele
    Univ Padua, Dept Informat Engn, Via Gradenigo 6b, I-35131 Padua, Italy..
    Decentralized Transmission Policies for Energy Harvesting Devices2017Ingår i: 2017 Ieee Wireless Communications And Networking Conference Workshops (WCNCW), IEEE , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    The problem of finding decentralized transmission policies in a wireless communication network with energy harvesting constraints is formulated and solved using the decentralized Markov decision process framework. The proposed policy defines the transmission strategies of all devices so as to correctly balance the collision probabilities with the energy constraints. After an initial coordination phase, in which the network parameters are initialized for all devices, every node proceeds in a fully decentralized fashion. We numerically show that, unlike in the case without energy constraints where a fully orthogonal scheme can be shown to be optimal, in the presence of energy harvesting this is no longer the best choice, and the optimal strategy lies between an orthogonal and a completely symmetric system.

  • 72.
    Biswas, Sinchan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Shirazinia, Amirpasha
    Analyt & AI Grp, S-17062 Stockholm, Sweden.
    Sum Throughput Maximization in a Cognitive Multiple Access Channel With Cooperative Spectrum Sensing and Energy Harvesting2019Ingår i: IEEE TRANSACTIONS ON COGNITIVE COMMUNICATIONS AND NETWORKING, ISSN 2332-7731, Vol. 5, nr 2, s. 382-399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper focuses on the problem of sensing throughput optimization in a fading multiple access cognitive radio (CR) network, where the secondary user (SU) transmitters participate in cooperative spectrum sensing and are capable of harvesting energy and sharing energy with each other. We formulate the optimization problem as a maximization of the expected achievable sum-rate over a finite horizon, subject to an average interference constraint at the primary receiver, peak power constraints, and energy causality constraints at the SU transmitters. The optimization problem is a non-convex, mixed integer non-linear program (MINLP) involving the binary action to sense the spectrum or not, and the continuous variables, such as the transmission power, shared energy, and sensing time. The problem is analyzed under two different assumptions on the available information pattern: 1) non-causal channel state information (CSI), energy state information (ESI), and infinite battery capacity and 2) the more realistic scenario of the causal CSI/ESI and finite battery. In the non-casual case, this problem can be solved by an exhaustive search over the decision variable or an MINLP solver for smaller problem dimensions, and a novel heuristic policy for larger problems, combined with an iterative alternative optimization method for the continuous variables. The causal case with finite battery is optimally solved using a dynamic programming (DP) methodology, whereas a number of sub-optimal algorithms are proposed to reduce the computational complexity of DP. Extensive numerical simulations are carried out to illustrate the performance of the proposed algorithms. One of the main findings indicates that the energy sharing is more beneficial when there is a significant asymmetry between average harvested energy levels/channel gains of different SUs.

  • 73.
    Biswas, Sinchan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Knorn, Steffi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Dey, Subhrakanti
    ITR, University of South Australia, Australia.
    Ahlén, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Quantized non-Bayesian quickest change detection with energy harvesting2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper focuses on the analysis of an optimal sensing and quantization strategy in a multi-sensor network where each individual sensor sends its quantized log-likelihood information to the fusion center (FC) for non-Bayesian quickest change detection. It is assumed that the sensors are equipped with a battery/energy storage device of finite capacity, capable of harvesting energy from the environment. The FC is assumed to have access to either non-causal or causal channel state information (CSI) and energy state information (ESI) from all the sensors while performing the quickest change detection. The primary observations are assumed to be generated from a sequence of random variables whose probability distribution function changes at an unknown time point. The objective of the detection problem is to minimize the average detection delay of the change point with respect to a lower bound on the rate of false alarm. In this framework, the optimal sensing decision and number of quantization bits for information transmission can be determined with the constraint of limited available energy due to finite battery capacity. This optimization is formulated as a stochastic control problem and is solved using dynamic programming algorithms for both non-causal and causal CSI and ESI scenario. A set of non-linear equations is also derived to determine the optimal quantization thresholds for the sensor log-likelihood ratios, by maximizing an appropriate Kullback-Leibler (KL) divergence measure between the distributions before and after the change. A uniform threshold quantization strategy is also proposed as a simple sub-optimal policy. The simulation results indicate that the optimal quantization is preferable when the number of quantization bits is low as its performance is significantly better compared to its uniform counterpart in terms of average detection delay. For the case of a large number of quantization bits, the performance benefits of using the optimal quantization as compared to its uniform counterpart diminish, as expected.

  • 74.
    Biswas, Sinchan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Shirazinia, Amirpasha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sensing Throughput Optimization in Cognitive Fading Multiple Access Channels With Energy Harvesting Secondary Transmitters2016Ingår i: 2016 24Th European Signal Processing Conference (EUSIPCO), 2016, s. 577-581Konferensbidrag (Refereegranskat)
    Abstract [en]

    The paper investigates the problem of maximizing the expected achievable sum rate in a fading multiple access cognitive radio network when secondary user (SU) transmitters have energy harvesting capability, and perform cooperative spectrum sensing. We formulate the problem as maximization of throughput of the cognitive multiple access network over a finite time horizon subject to a time averaged interference constraint at the primary user (PU) and almost sure energy causality constraints at the SUs. The problem is a mixed integer non-linear program with respect to two decision variables, namely, spectrum access decision and spectrum sensing decision, and the continuous variables sensing time and transmission power. In general, this problem is known to be NP hard. For optimization over these two decision variables, we use an exhaustive search policy when the length of the time horizon is small, and a heuristic policy for longer horizons. For given values of the decision variables, the problem simplifies into a joint optimization on SU transmission power and sensing time, which is non-convex in nature. We present an analytic solution for the resulting optimization problem using an alternating convex optimization problem for non-causal channel state information and harvested energy information patterns at the SU base station (SBS) or fusion center (FC) and infinite battery capacity at the SU transmitters. We formulate the problem with causal information and finite battery capacity as a stochastic control problem and solve it using the technique of dynamic programming. Numerical results are presented to illustrate the performance of the various algorithms.

  • 75.
    Biswas, Sinchan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Shirazinia, Amirpasha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sensing throughput optimization in fading cognitive multiple access channels with energy harvesting secondary transmitters.: Extended version of conference paper2016Rapport (Övrigt vetenskapligt)
  • 76.
    Björkman, Tony
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Redesign of environmental stress screening software2014Självständigt arbete på grundnivå (yrkesexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this thesis a industrial test process used during the manufacturing of pressure sensors has beenexamined. The examination is aimed to find areas of improvements related to the software that isused in the process. This test process separates faulty components, in this case circuit boards, beforethey are assembled into a finished product. The separation is made by letting a software applicationmonitor how the functionality of the circuit boards is affected during stress by high temperature andvibration. How the process is performed from a operator viewpoint was examined in the productionplant and suggestions from the operators collected. A preliminary design specification ,that wassupplied at the beginning of the thesis, was completed with the information that was gathered. Thekey improvements to the software were that the evaluation of test results should be automatic andthe software solution should be more scalable in terms of the amount of circuit boards that it canmonitor. The completed specification has been implemented in LabVIEW as a prototype applicationthat contains the key improvements of increased scalability and automatic evaluation of results.

  • 77.
    Björnemo, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Ahlén, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Johansson, Mathias
    Dirac Research AB, Uppsala.
    On the energy-efficiency of cooperative MIMO in nakagami-fading wireless sensor networks2007Konferensbidrag (Refereegranskat)
  • 78.
    Björsell, Joachim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Long Range Channel Predictions for Broadband Systems: Predictor antenna experiments and interpolation of Kalman predictions2016Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The field of wireless communication is under massive development and the demands on the cellular system, especially, are constantly increasing as the utilizing devices are increasing in number and diversity. A key component of wireless communication is the knowledge of the channel, i.e, how the signal is affected when sent over the wireless medium. Channel prediction is one concept which can improve current techniques or enable new ones in order to increase the performance of the cellular system. Firstly, this report will investigate the concept of a predictor antenna on new, extensive measurements which represent many different environments and scenarios. A predictor antenna is a separate antenna that is placed in front of the main antenna on the roof of a vehicle. The predictor antenna could enable good channel prediction for high velocity vehicles. The measurements show to be too noisy to be used directly in the predictor antenna concept but show potential if the measurements can be noise-filtered without distorting the signal. The use of low-pass filter and Kalman filter to do this, did not give the desired results but the technique to do this should be further investigated.

    Secondly, a interpolation technique will be presented which utilizes predictions with different prediction horizon by estimating intermediate channel components using interpolation. This could save channel feedback resources as well as give a better robustness to bad channel predictions by letting fresh, local, channel predictions be used as quality reference of the interpolated channel estimates. For a linear interpolation between 8-step and 18-step Kalman predictions with Normalized Mean Square Error (NMSE) of -15.02 dB and -10.88 dB, the interpolated estimates had an average NMSE of -13.14 dB, while lowering the required feedback data by about 80 %. The use of a warning algorithm reduced the NMSE by a further 0.2 dB. It mainly eliminated the largest prediction error which otherwise could lead to retransmission, which is not desired. 

  • 79.
    Björsell, Joachim
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Grieger, M
    Using predictor antennas for the prediction of small-scale fading provides an order-of-magnitude improvement of prediction horizons2017Rapport (Övrigt vetenskapligt)
  • 80.
    Björsell, Joachim
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Grieger, Michael
    AIRRAYS Wireless Solut Dresden, Dresden, Germany.
    Predictor antennas in action2017Ingår i: 2017 IEEE 28th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), IEEE, 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Connected vehicles in large numbers will be expensive in terms of power and bandwidth unless advanced transmit schemes are employed. These would rely on channel state information at transmitter (CSIT), which rapidly becomes outdated for fading vehicular channels. We here evaluate the predictor antenna concept, that solves this problem by using antennas on the outside of vehicles, with one extra antenna in front of the others. Its estimated channel is a scaled prediction for the channels encountered by rearward antennas when they reach that position. We evaluate this concept on a large set of channel sounding measurements from an urban environment. Recent investigations of the correlations of these measurements indicate that the average normalized mean squared errors (NMSEs) of the complex valued channel predictions should be around -10 dB for prediction horizons in space of up to 3 wavelengths. This represents an extension of the attainable prediction horizon by an order of magnitude, as compared to Kalman or Wiener extrapolation of past channel measurements. It represents an accuracy that would enable e.g. accurate massive multiple input multiple output (MIMO) downlink beamforming to vehicles. We here perform predictions on a subset of the measurements with good channel-to-estimation error power ratio (SNR). The approximate true channels are here available and we evaluate the performance on a validation data set. The results confirm that the distribution of the NMSE, over all investigated propagation environments, is close to that obtained by correlation-based models and outperforms the use of outdated channel measurements.

  • 81.
    Björsell, Joachim
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Grieger, Michael
    AIRRAYS Wireless Solut Dresden, Dresden, Germany.
    Using predictor antennas for the prediction of small-scale fading provides an order-of-magnitude improvement of prediction horizons2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Our aim is to investigate long range predictions (up to several wavelengths) of the small-scale fading of radio channels. The purpose is to enable advanced 5G downlink transmission schemes that require accurate channel state information at transmitters, such as massive MIMO and coherent joint transmission, for vehicular users. We here present a proof of concept for the recently introduced predictor antenna scheme which promises a significant increase in prediction horizon compared to conventional techniques. Predictor antennas utilize the exterior of moving vehicles by placing antenna arrays on top of their roofs. They are used to estimate the fading radio channels that are encountered later by the following antennas. The level of predictability is determined by the correlation between the channel measured at the predictor antenna and the channel that is later encountered by the following antennas when they move to that position. That correlation, and the resulting prediction errors, are assessed on a large set of measurement data sampled at vehicular velocities, at a carrier frequency of 2.53 GHz, from a multitude of urban fading environments. These represent a wide variety of propagation environments, including narrow and wide roads, intersections, dense urban environments and residential areas. Using low-pass filtered predictor antenna measurements, the obtained average prediction Normalized Mean Squared Error (NMSE) is -11 dB for prediction horizons of 0.25 wavelengths and -8.5 dB for horizons of 3 wavelengths. This represents an order of magnitude increase of the prediction horizons as compared to time-series prediction that typically, in practice, fails to work for prediction beyond 0.3 wavelengths in space. As a result, we have a tool that enables advanced 5G transmit schemes for vehicular users and vehicle-to-infrastructure links.

  • 82.
    Bladlund, Sara
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Evolution of 3D User Distribution Models in Real Network Simulator2010Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The report treats the development and evaluation of a three dimensional user distribution model for a real network simulator. The simulator is used to create realistic predictions of real networks with the use of high resolution maps including a building data base and network data and also an advanced radio model for LTE. Previously all simulations have been performed with a two dimensional user distribution, i.e. all users situated on the ground level. Since it is considered plausible that many LTE users will be indoors in buildings with multiple floors, several three dimensional user distribution models with users not only on the ground floor but also on the higher floors has been developed and implemented in the simulator. The models all account for the change in path loss and SINR to be expected and have been compared in computational time and credibility. The simulations show that by the use of such a three dimensional model there is a significant improvement at low loads but at high loads the interference becomes dominant and the results show a deterioration and approaches the results of the ordinary two dimensional model. The seventh and last model to be investigated shows a desirable computational speed that still does not compromise too much with the accuracy and detailing of the model and is therefore recommended for normal use.

  • 83.
    Bondesson, Carl
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Modelling of Safety Concepts for Autonomous Vehicles using Semi-Markov Models2018Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Autonomous vehicles is soon a reality in the every-day life. Though before it is used commercially the vehicles need to be proven safe. The current standard for functional safety on roads, ISO 26262, does not include autonomous vehicles at the moment, which is why in this project an approach using semi-Markov models is used to assess safety. A semi-Markov process is a stochastic process modelled by a state space model where the transitions between the states of the model can be arbitrarily distributed. The approach is realized as a MATLAB tool where the user can use a steady-state based analysis called a Loss and Risk based measure of safety to assess safety. The tool works and can assess safety of semi-Markov systems as long as they are irreducible and positive recurrent. For systems that fulfill these properties, it is possible to draw conclusions about the safety of the system through a risk analysis and also about which autonomous driving level the system is in through a sensitivity analysis. The developed tool, or the approach with the semi-Markov model, might be a good complement to ISO 26262.

  • 84.
    Brandt, Rasmus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Polynomial Matrix Decompositions: Evaluation of Algorithms with an Application to Wideband MIMO Communications2010Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The interest in wireless communications among consumers has exploded since the introduction of the "3G" cell phone standards. One reason for their success is the increasingly higher data rates achievable through the networks. A further increase in data rates is possible through the use of multiple antennas at either or both sides of the wireless links.

    Precoding and receive filtering using matrices obtained from a singular value decomposition (SVD) of the channel matrix is a transmission strategy for achieving the channel capacity of a deterministic narrowband multiple-input multiple-output (MIMO) communications channel. When signalling over wideband channels using orthogonal frequency-division multiplexing (OFDM), an SVD must be performed for every sub-carrier. As the number of sub-carriers of this traditional approach grow large, so does the computational load. It is therefore interesting to study alternate means for obtaining the decomposition.

    A wideband MIMO channel can be modeled as a matrix filter with a finite impulse response, represented by a polynomial matrix. This thesis is concerned with investigating algorithms which decompose the polynomial channel matrix directly. The resulting decomposition factors can then be used to obtain the sub-carrier based precoding and receive filtering matrices. Existing approximative polynomial matrix QR and singular value decomposition algorithms were modified, and studied in terms of decomposition quality and computational complexity. The decomposition algorithms were shown to give decompositions of good quality, but if the goal is to obtain precoding and receive filtering matrices, the computational load is prohibitive for channels with long impulse responses.

    Two algorithms for performing exact rational decompositions (QRD/SVD) of polynomial matrices were proposed and analyzed. Although they for simple cases resulted in excellent decompositions, issues with numerical stability of a spectral factorization step renders the algorithms in their current form purposeless.

    For a MIMO channel with exponentially decaying power-delay profile, the sum rates achieved by employing the filters given from the approximative polynomial SVD algorithm were compared to the channel capacity. It was shown that if the symbol streams were decoded independently, as done in the traditional approach, the sum rates were sensitive to errors in the decomposition. A receiver with a spatially joint detector achieved sum rates close to the channel capacity, but with such a receiver the low complexity detector set-up of the traditional approach is lost.

    Summarizing, this thesis has shown that a wideband MIMO channel can be diagonalized in space and frequency using OFDM in conjunction with an approximative polynomial SVD algorithm. In order to reach sum rates close to the capacity of a simple channel, the computational load becomes restraining compared to the traditional approach, for channels with long impulse responses.

  • 85.
    Breitholtz, Nils
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Controller programming with CoDeSys for an automated timber sorting system2010Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This report describes the development of weight measurement application and transducer positioning for the A Sort prototype that has been developed for automatic grading and sorting of timber. The prototype consists of a transportation system with hydraulic and electrical motors, a measurement system with laser scanners and acoustic measurement equipment and a control program for the automated process with CoDeSys. The objective was to integrate these parts in an automatic system process, controlling a prototype designed for acoustic measurement of logs. The devices were installed and configured to communicate via an existing fieldbus line using CANopen as communication protocol. A control program was made for each task and implemented in the control process for the automatic measurement of logs. Two load cells were installed beneath a moving tilt and the measurement equipment was tested and calibrated using three different logs with known weight. The testing showed that in order to get higher accuracy the construction needs to be modified. Photo cells were installed on the measurement frames and a program was made in order to make the acoustic measurement of the logs work properly.

  • 86.
    Brykt, Joakim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Development of a Digital Optimal Filter Platform2018Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This report is the result of a Master Thesis project which is a part of the Master programme in Electrical Engineering at Uppsala universitet.

    The purpose of this Master Thesis project is to develop an embedded platform for the design and implementation of optimal digital filters, in particular, the Kalman and the Wiener filter. In this project these filters are used for noise reduction on noisy signals. The project is a further development of a previous Master Thesis project where a Universal Filter Bank was developed. The Filter Bankis used for designing and implementing various linear digital filters such as lowpass, highpass, bandpass and bandstop. The Filter Bank is a hand held box with two input and two output connections and a human-device interface (HDI) including a Liquid Crystal Display (LCD) and a keypad. It contains anti-aliasing and reconstruction (analog) filters and an ARM 32-bit Microcontroller Unit (MCU) which is programmed in the C programming language. The HDI lets the user specify a desired digital filter.

    In this project the Kalman and Wiener filtering algorithms were first developed in MATLAB and tested with simulated autoregressive–movingaverage (ARMA) processes (signals) in additive white noise. Aftershown to work, they were implemented on the ARM 32-bit MCU development kit, and finally ported to the Filter Bank. A user interface specially for the specifications of the filters has been created.

    The Kalman and Wiener filtering algorithms have been tested using the same noisy ARMA processes and assessed in terms of the Normalized Mean Square Error (NMSE). The results have shown that both the Wiener and Kalman filters running on the development kit and the Filter Bank are successful in reducing noise. The Kalman filter is shown to perform better than the Wiener filter, which can be due to the extra information about the signal used in the Kalman filter. The performance of both algorithms are heavily dependent on the pre knowledge about the desired signal.

  • 87.
    Brännmark, Lars-Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Robust audio precompensation with probabilistic modeling of transfer function variability2009Ingår i: 2009 IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA2009), New York City, NY, 2009Konferensbidrag (Refereegranskat)
  • 88.
    Brännmark, Lars-Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Robust Sound Field Control for Audio Reproduction: A Polynomial Approach to Discrete-Time Acoustic Modeling and Filter Design2011Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    This thesis is concerned with the design and analysis of robust discrete-time filters for audio equalization and sound field control in real reverberant environments. Inspired by methods in polynomial control theory, a unified framework for acoustic modeling and filter design is developed. The work on modeling is centered around three main themes: First, the acoustic channel between a loudspeaker and a point in space is studied in time, frequency and space, and a polynomial matrix fraction description with diagonal denominator is selected as a physically motivated channel model. As a means for representing channel uncertainties, a probabilistic design model is proposed. Second, the concept of sound field dimensionality, based on the Karhunen-Loève expansion of the sound field, is explored and integrated into the polynomial systems context. Third, a method for spatial interpolation of acoustic transfer functions is proposed and evaluated. Interpolation errors are accounted for by applying the probabilistic uncertainty model to the interpolated data. The work on filter design can be categorized into single- and multichannel methods. The single-channel problem concerns the improvement of the impulse and frequency responses of a single loudspeaker over a region in space, by means of a scalar prefilter. This problem is posed in a SIMO (single-input multiple-output) feedforward control setting, and is solved using polynomial methods. The solution offers several useful insights and results. In particular, new results are derived regarding the adverse pre-ringing problem associated with mixed phase filters. Based on the new results, a refined mixed phase method is proposed that is practically free from pre-ringing artifacts. In the multichannel problem, a desired spatio-temporal sound field is approximated by the joint use of several loudspeakers. This problem is initially formulated and solved by feedforward control over a continuous spatial domain, assuming full knowledge of the spatial field. To obtain a practically feasible design, the control criterion is then spatially discretized, resulting in a standard MIMO(multiple-input multiple-output) linear quadratic feedforward control problem. Since information is generally lost in the discretization process, a robust design based on spatial interpolation and probabilistic error modeling is proposed. The multichannel designs are assessed in an automotive setting, using practical measurements of a nine-channel sound system in a car.

  • 89.
    Brännmark, Lars-Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System. Dirac AB, Uppsala.
    Ahlén, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Multichannel Room Correction with Focus Control2015Ingår i: Journal of The Audio Engineering Society, ISSN 0004-7554, ISSN 1549-4950, Vol. 63, nr 1-2, s. 21-30Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Digital equalization of audio systems is mostly performed on a channel-by-channel basis, i.e., loudspeakers are equalized separately and independently of each other. In reverberant rooms the spatial variability of the loudspeaker room transfer function puts a limit on what can be achieved with such single-channel approaches, and considerably more far-reaching results can be obtained with multichannel methods. In this paper we present a multichannel equalizer design method where the loudspeaker to be equalized is assisted by several support loudspeakers that act in combination to improve the response of the main loudspeaker while suppressing the reverberation of the listening room. However, since a full dereverberation may not always be desirable, we shall here study the proposed method from the perspective of how to control the amount of room correction for a given number of contributing support loudspeakers. The amount of correction is controlled by a scalar parameter that we interpret as a "focus control," enabling the user to slide seamlessly between a single-channel equalizer and a full multichannel inversion of the room.

  • 90.
    Brännmark, Lars-Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Ahlén, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Robust loudspeaker equalization based on position-independent excess phase modeling2008Ingår i: 2008 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING, VOLS 1-12, 2008, s. 385-388Konferensbidrag (Refereegranskat)
    Abstract [en]

    A well known problem in loudspeaker equalization is that mixed phase design of the inverse filter causes residual "pre-ringings" in the equalized system, due to the spatial variability of loudspeakerroom transfer functions. A common strategy for robust and perceptually acceptable equalization is therefore to use minimum phase filters only. In this paper, a method for cautious mixed phase equalization is proposed. By analysis of a set of room transfer functions, it is concluded that some non-minimum phase zeros are insensitive to receiver position, and can therefore be robustly inverted. The method improves upon a minimum phase equalization by extending the minimum phase model with a robustly invertible all pass link. Validation measurements show that the time-domain aspect of equalization is improved throughout the spatial region of interest, while preringings are kept at a very low and prespecified level.

  • 91.
    Brännmark, Lars-Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Ahlén, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Spatially robust audio compensation based on SIMO feedforward control2009Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 57, nr 5, s. 1689-1702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper introduces a single-input multiple-output (SIMO) feedforward approach to the single-channel loudspeaker equalization problem. Using a polynomial multivariable control framework, a spatially robust equalizer is derived base on a set of room transfer functions (RTFs) and a multipoint mean-square error (MSE) criterion. In contrast to earlier multipoint methods, the polynomial approach provides analytical expressions for the optimum filter, involving the RTF polynomials and certain spatial averages thereof. However, a direct use of the optimum solution is questionable from a perceptual point of view. Despite its multipoint MSE optimality, the filter exhibits similar, albeit less severe, problems as those encountered in nonrobust single-point designs. First, in the case of mixed phase design it is shown to cause residual "pre-ringings" and undesirable magnitude distortion in the equalized system. Second, due to insufficient spatial averaging when using a limited number of RTFs in the design, the filter is overfitted to the chosen set of measurement points, thus providing insufficient robustness. A remedy to these two problems is proposed, based on a   constrained MSE design and a method for clustering of RTF zeros. The outcome is a mixed phase compensator with a time-domain performance preferable to that of the original unconstrained design.

  • 92.
    Brännmark, Lars-Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Ahlén, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Variable control of the pre-response error in mixed phase audio precompensation2009Ingår i: 2009 IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA 2009), New York CIty, NY, 2009Konferensbidrag (Refereegranskat)
  • 93.
    Brännmark, Lars-Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Bahne, Adrian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Ahlén, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Compensation of Loudspeaker-Room Responses in a Robust MIMO Control Framework2013Ingår i: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, Vol. 21, nr 6, s. 1201-1216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new multichannel approach to robust broadband loudspeaker-room equalization is presented. Traditionally, the equalization (or room correction) problem has been treated primarily by single-channel methods, where loudspeaker input signals are prefiltered individually by separate scalar filters. Single-channel methods are generally able to improve the average spectral flatness of the acoustic transfer functions in a listening region, but they cannot reduce the variability of the transfer functions within the region. Most modern audio reproduction systems, however, contain two or more loudspeakers, and in this paper we aim at improving the equalization performance by using all available loudspeakers jointly. To this end we propose a polynomial based MIMO formulation of the equalization problem. The new approach, which is a generalization of an earlier single-channel approach by the authors, is found to reduce the average reproduction error and the transfer function variability over a region in space. Moreover, pre-ringing artifacts are avoided, and the reproduction error below 1000 Hz is significantly reduced with an amount that scales with the number of loudspeakers used.

  • 94.
    Brännmark, Lars-Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Bahne, Adrian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Ahlén, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Improved loudspeaker-room equalization using multiple loudspeakers and MIMO feedforward control2012Ingår i: Acoustics, Speech and Signal Processing (ICASSP), 2012 IEEE International Conference, 2012, s. 237-240Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a new multichannel approach to robust loudspeaker-room equalization is presented. Traditionally, the equalization (or room correction) problem has been treated mostly by single-channel methods, with loudspeaker signals being prefiltered individually by separate scalar filters. Single-channel methods can generally improve the average spectral flatness of the acoustic transfer functions in a listening region, but the variability of the transfer functions within the region cannot be affected. Most modern audio reproduction systems, however, contain two or more loudspeakers, and in this paper we aim at improving the equalization performance by using all available loudspeakers jointly. To this end we propose a general MIMO formulation of the problem, which is a multichannel generalization of an earlier single-channel approach by the authors. The new approach is found to reduce the average reproduction error and the spatial variability of the acoustic transfer functions. Moreover, pre-ringing artifacts are avoided, and the reproduction error below 1000 Hz is significantly reduced with an amount that scales with the number of loudspeakers used.

  • 95.
    Brännmark, Lars-Johan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Controlling the impulse responses and the spatial variability in digital loudspeaker-room correction2015Konferensbidrag (Refereegranskat)
  • 96.
    Casimiro Ericsson, Nilo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.