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  • 151. Hult, Tommy
    et al.
    Mohammed, Abbas
    Estimation of the TOA performance of Loran-C2004Conference paper (Refereed)
    Abstract [en]

    Loran-C is a navigational aid that relies on the ability to make correct estimates of the Times of Arrival (TOAs) of signals received over a noisy radio channel. How good is the performance of Loran-C in this respect? Is it close to optimal? Are there perhaps better estimation techniques available than we currently employ? In this paper we use Estimation Theory to find the optimal limit of the accuracy of TOA estimates, for a given signal-to-noise ratio (SNR). Specifically, we compute the Cramer-Rao Lower Bound (CRLB) which specifies the absolute minimum error variance that can be achieved by an unbiased estimator. From the CRLB we can estimate the best repeatable accuracy that can be attained using a set of TOAs. We compute here the CRLBs for the TOA of a Loran-C signal with both Additive White Gaussian Noise (AWGN) and Additive Coloured Gaussian Noise (ACGN). We then employ the Maximum Likelihood Estimator (MLE) and compare its results with that of CRLB. Simulation results show that the MLE approaches the minimum variance obtained by CRLB for SNR values of practical and reliable Loran-C operation.

  • 152. Hult, Tommy
    et al.
    Mohammed, Abbas
    HAP Diversity and Compact MIMO Antennas for High Data Rate Communications2006Conference paper (Refereed)
    Abstract [en]

    In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with HAP diversity and OFDM techniques in order to increase the data rates in HAP communication systems. Simulation results show that the MIMO system provides superior performance as compared to the single HAP case.

  • 153. Hult, Tommy
    et al.
    Mohammed, Abbas
    Indoor Propagation Simulation using FEM for Short-Range Wireless Communication Systems Operating at 2.4 GHz2005Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate the wave propagation effects of a short-range wireless device, like the Bluetooth, in an indoor office environment. Specifically, we investigate line of sight (LOS) and non line of sight (NLOS) propagation scenarios and verify the theoretical statistics of the fading using real measurements and finite element method (FEM) simulations of the environment. The simulations are also used for assessing the impact on propagation when doors are opened or closed. In addition, we also investigate the improvement in performance resulting from receive diversity gain of a system employing multiple receive antennas with various combining techniques.

  • 154. Hult, Tommy
    et al.
    Mohammed, Abbas
    MIMO ANTENNA APPLICATIONS FOR HIGH ALTITUDE PLATFORMS2006Conference paper (Refereed)
    Abstract [en]

    In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with HAP (High Altitude Platforms) diversity techniques in order to increase the data rates in HAP communication systems. Simulation results show that the MIMO system provides superior performance as compared to the single HAP case.

  • 155. Hult, Tommy
    et al.
    Mohammed, Abbas
    MIMO Antenna Applications for LEO Satellite Communications2005Conference paper (Refereed)
    Abstract [en]

    This paper addresses the potential gain of using multiple antennas and MIMO-OFDM techniques 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.

  • 156. Hult, Tommy
    et al.
    Mohammed, Abbas
    MIMO for HAPs: an idea whose time has come2006Conference paper (Refereed)
    Abstract [en]

    In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with HAP diversity techniques in order to increase the data rates in HAP communication systems. Simulation results show that the MIMO system provides superior performance as compared to the single HAP case

  • 157. Hult, Tommy
    et al.
    Mohammed, Abbas
    MULTIPATH PROPAGATION ASSESSMENT FOR A 2.4 GHZ SHORT-RANGE WIRELESS COMMUNICATION SYSTEM2006Conference paper (Refereed)
    Abstract [en]

    In this paper we assess the effects of multipath propagation on the link performance of a short-range wireless device, like the Bluetooth, in an indoor office environment. Specifically, we analyze the non line of sight (NLOS) propagation scenario and confirm the theoretical statistics of the fading using real measurements and finite element method (FEM) simulations of the environment. The simulations are also used for assessing the impact of multipath propagation when doors are opened or closed. In addition, we also investigate the improvement in performance resulting from receive diversity gain of a system employing multiple receive antennas with various combining techniques.

  • 158. Hult, Tommy
    et al.
    Mohammed, Abbas
    Novel Applications of MIMO Antenna System for Active Suppression of Electromagnetic Fields2005Report (Other academic)
    Abstract [en]

    Active suppression of noise and vibrations is a well established field of research with many applications in acoustic and mechanical industries. In this report we test some of these active control methods combined with MIMO antenna system in order to assess their validity and performance when applied to electromagnetic fields. The application that we evaluated is a model of a mobile phone equipped with one ordinary transmitting antenna and a number of actuator-antennas which purpose is to cancel out the electromagnetic field at a specific volume in space (e.g. at the human head) while maintaining a predefined level of the overall output power of the system. This power control is achieved through the use of a quadratic constraint on the active control algorithm. In addition, we will also investigate the impact of MIMO antenna parameters and carrier frequency on the performance of the system. Simulation results show the promise of using the adaptive control algorithms and MIMO system to attenuate the electromagnetic field power density.

  • 159. Hult, Tommy
    et al.
    Mohammed, Abbas
    Performance Evaluation of Adaptive Signal Processing and MIMO Antenna System for the Reduction of Electromagnetic Field Density2007Conference paper (Refereed)
  • 160. Hult, Tommy
    et al.
    Mohammed, Abbas
    Power Constrained Active Suppression of Electromagnetic Fields Using MIMO Antenna System2004Conference paper (Refereed)
  • 161. Hult, Tommy
    et al.
    Mohammed, Abbas
    Power Constrained Space-Time Processing for Suppression of Electromagnetic Fields2005In: Journal of Communication Software and Systems, ISSN 1845-6421, E-ISSN 1846-6079, Vol. 1, no 1Article in journal (Refereed)
    Abstract [en]

    Active suppression of noise and vibrations is a well established field of research with many applications in acoustic and mechanical industries. In this paper we investigate the possibility of applying these adaptive active control methods with the aim of lowering the electromagnetic power density at a specific volume in space using the superposition principle and space-time processing employing the full MIMO (Multiple Input Multiple Output) antenna system setup. The application that we evaluated is a model of a mobile phone equipped with one ordinary transmitting antenna and two actuator-antennas which purpose is to cancel out the electromagnetic field at the human head while maintaining a predefined level of the overall output power of the system. This power control is achieved through the use of a quadratic constraint on the active control algorithm. Simulation results show the promise of using the adaptive control algorithms and MIMO system to attenuate the electromagnetic field power density

  • 162. Hult, Tommy
    et al.
    Mohammed, Abbas
    Suppression of EM Fields using Active Control Algorithms2004In: Radioengineering, ISSN 1210-2512, E-ISSN 1805-9600, Vol. 13, no 3, p. 22-25Article in journal (Refereed)
    Abstract [en]

    Active methods for attenuating acoustic pressure fields have been successfully used in many applications. In this paper we investigate some of these active control methods in combination with a MIMO antenna system in order to assess their validity and performance when applied to electromagnetic fields. The application that we evaluated in this paper is a model of a mobile phone equipped with one ordinary transmitting antenna and two actuator-antennas which purpose is to reduce the electromagnetic field at a specific area in space (e.g. at the human head). Simulation results show the promise of using the adaptive active control algorithms and MIMO system to attenuate the electromagnetic field power density.

  • 163. Hult, Tommy
    et al.
    Mohammed, Abbas
    THE IMPACT OF MIMO ANTENNA SYSTEM AND CARRIER FREQUENCYON ACTIVE CONTROL SUPPRESSION OF ELECTROMAGNETIC FIELD2004Conference paper (Refereed)
    Abstract [en]

    There have been several studies done, with conflicting results, on the effects of cell-phone radiation on the human body. The amount of radiation emitted from most cell phones is very minute. However, given the close proximity of the phone to the head, it is entirely possible for the radiation to cause harm. If you want to be on the safe side, the easiest way to minimize the radiation you are exposed to is to position the antenna as far from your head as possible. Utilizing a hands-free kit, a car-kit antenna or a cell phone whose antenna is even a couple of inches farther from the head can do this most effectively. This paper makes a contribution to that discussion by proposing a new approach by employing adaptive active control algorithms combined with a Multiple-Input Multiple-Output (MIMO) antenna system to suppress the electromagnetic field at a certain area in space. We will also investigate the effects of the size and number of MIMO antenna elements and test the algorithms at different carrier frequencies (e.g., other GSM bands and UMTS).

  • 164. Hult, Tommy
    et al.
    Mohammed, Abbas
    Theoretical Analysis and Assessment of Depolarization Effects on the Performance of High Altitude Platforms2008Conference paper (Refereed)
  • 165. Hult, Tommy
    et al.
    Mohammed, Abbas
    Falletti, Emanuela
    Sellone, Fabrizio
    Analysis of Depolarizing Effects and Impact on the Performance of a Multiple Satellite System Employing Polarization Diversity2007Conference paper (Refereed)
  • 166. Hult, Tommy
    et al.
    Mohammed, Abbas
    Falletti, Emanuela
    Sellone, Fabrizio
    Multi-Antenna Multi-HAP Channel Model for Space-Polarization2008Conference paper (Refereed)
  • 167. Hult, Tommy
    et al.
    Mohammed, Abbas
    Grace, David
    WCDMA Coverage Enhancement from Multiple High Altitude Platforms2008Conference paper (Refereed)
  • 168. Hult, Tommy
    et al.
    Mohammed, Abbas
    Grace, David
    Yang, Zhe
    Performance of a Multiple HAP System Employing Multiple Polarization2006Conference paper (Refereed)
  • 169. Hultgren, Anders
    et al.
    Nilsson, Magnus
    Kulesza, Wlodek
    Walther, Björn
    Integration av matematik och teknik på ingenjörsutbildningar2008Conference paper (Other academic)
    Abstract [sv]

    I detta bidrag presenterar vi en uppläggning av integrerade kurser i matematik och tillämpningar, vilken använts inom högskoleingenjörsutbildningen vid Högskolan i Kalmar. Kursverksamheten, som bedrivs inom ramen för kurspaketet ingenjörsvetenskap, tillgodoser såväl behovet av att betona matematikens roll som ett generellt och abstrakt verktyg för problemlösning som behovet av att ge studenterna bra baskunskaper i matematik i anslutning till möjliga tillämpningsområden.

  • 170.
    Hussain, Rizwan
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    ADAPTIVE POWER CONTROL BY USING THE RECEIVED SNR AS A PROXY FOR DISTANCE TO OPTIMIZE THE SPECTRUM USAGE IN A COGNITIVE RADIO SYSTEMADAPTIVE POWER CONTROL BY USING THE RECEIVED SNR AS A PROXY FOR DISTANCE TO OPTIMIZE THE SPECTRUM USAGE IN A COGNITIVE RADIO SYSTEM2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In this thesis work we have proposed an Adaptive Power Transmission scheme for Cognitive Radio. The proposed scheme estimates the distance between the primary user and the Cognitive Radio, using the SNR as proxy for distance, also utilizing the information of IT (Interference Temperature). On the basis of these information the Cognitive radio adaptively changes its transmit power to prevent the primary user from harmful interference. The most challenging problem of cognitive radio is the interference which occurs when a cognitive radio accesses a licensed band but fails to notice the presence of the licensed user. Another challenge is to compute the correct distance between the cognitive radio and the primary user. To allow the cognitive radio to access the same spectrum band where the primary user is operating creates a problem, in such case; the cognitive radio may interfere with the primary system, hence degrading the quality of service for the primary receiver. The Primary goal of this work is to propose Adaptive power control based on the estimated distance R_cr^pr between the cognitive radio and primary user. We will discuss the transmit power being controlled on the basis of distance. But there is no such method to calculate the exact distance between the cognitive radio and the primary user, so that we interpret distance in terms of SNR. We will propose a method to make the CR so intelligent that it can determine the maximum level of the transmission power which does not cause any harmful interference to the primer user’s quality of service.

  • 171.
    Hussain, Sajid
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Dynamic Radio Resource Management in 3GPP LTE2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Orthogonal Frequency Division Multiple Access (OFDMA) is specified as downlink multiple access scheme in 3GPP LTE which divides the available bandwidth into multiple narrow orthogonal frequency bands. Thus, there is no ISI (Inter Symbol Interference) within the cell boundary. As the whole frequency spectrum is available in a cell site there would be greater chance of ICI (Intercell Interference) among the cell edge users of adjoining cells if frequency bands are allocated without any arrangement. This ICI can be mitigated with the help of different arrangements of frequency bands allocations and possibly with different transmission power distinguishing between the cell centre users and cell edge users. In this thesis work different ICI mitigation techniques are analyzed with different frequency allocation schemes and transmission power, and also different radio resource scheduling algorithms are analysed to enhance bandwidth efficiency and throughput.

  • 172. Håkansson, Lars
    et al.
    Claesson, Ingvar
    A Solution to Control Path Differences in The Feedback Filtered-x LMS Control of Boring Bar Vibration2004Conference paper (Refereed)
    Abstract [en]

    The internal turning operation is a common metal working operation that is usually associated with vibration problems. Boring bar vibration affect the result of the machining, in particular the surface finish. Furthermore, the tool life is correlated with the amount of vibration and the acoustic noise introduced. The noise level is sometimes almost unbearable. Generally, the motion of a boring bar is greatest in the cutting speed direction, and related to one of the bars two fundamental bending modes. A self tuning solution that has a high potential to further reduce the vibration problems in internal turning is the adaptive active control of boring bar vibration based on the feedback filtered-x LMS algorithm and boring bars with embedded actuators. The filtered-x LMS requires an estimate of the control path. To obtain a practical estimation of the control path, to avoid internal turning with severe vibration levels, usually requires that the control path is estimated off-line, i.e. the boring bar is not in contact with the workpiece. However, the control path usually differs between continuous cutting operations and when the boring bar is not in contact with the workpiece, and a phase difference of approximately 90 degrees generally occurs at the resonance frequency to be controlled. This phase difference constitutes a severe problem concerning the feedback filtered-x LMS control. By using a short FIR-filter control path estimate sufficient phase accuracy is obtained to enable robust adaptive control of bar vibration, which attenuates the vibration level with up to approximately 40 dB.

  • 173. Håkansson, Lars
    et al.
    Johansson, Sven
    Claesson, Ingvar
    Chapter 78 Machine Tool Noise, Vibration and Chatter Prediction and Control2005In: HANDBOOK OF NOISE AND VIBRATION CONTROL / [ed] Crocker, Malcolm J., New York: To be published by by John Wiley & Sons , 2005Chapter in book (Other academic)
    Abstract [en]

    A frequent problem in the manufacturing industry today is the vibrations or chatter induced by metal cutting, e.g. turning, milling and boring operations. Vibrations in boring operations or internal turning operations, for example,are inevitable and constitute a major problem for the manufacturing industry. Tool vibrations in metal cutting affect the result of machining, particularly the surface finish. Furthermore, tool life is correlated with the degree of vibration and acoustic noise introduced. Generally, tool vibrations are related to a low-order bending mode of, for example, the tool holder shank in external turning, the boring bar in internal turning, spindle-cutter assembly in milling, etc. Tool chatter or vibration problems in internal turning or milling may be reduced, for example, by using boring bars and milling adapters with passive tuned dampers. These are usually manually tuned to increase the dynamic stiffness of the boring bar or milling adapter at one of the eigenfrequencies of its low-order bending modes. Active control approaches for the attenuation of the bending motion of boring bars, tool holder shanks and spindle-cutter assembly in milling have been developed; such approaches involve both adaptive and time-invariant feedback control. In addition, prediction and control methods for controlling cutting data to maintain stable cutting, i.e. to avoid cutting data resulting in chatter, have been developed.

  • 174. Håkansson, Lars
    et al.
    Johansson, Sven
    Claesson, Ingvar
    Machine Tool Noise, Vibration and Chatter Prediction and Control2007In: HANDBOOK OF NOISE AND VIBRATION CONTROL / [ed] Crocker, Malcolm J., New York: John Wiley & Sons , 2007Chapter in book (Other academic)
  • 175.
    Iqbal, Muhammad Imran
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Aibinu, Abiodun Musa
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Gubbal, Nagendra Srinivas
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Khan, Asim
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    AUTOMATIC DIAGNOSIS OF DIABETIC RETINOPATHY USING FUNDUS IMAGES2006Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    This thesis applies the process and knowledge of digital signal processing and image processing to diagnose diabetic retinopathy from images of retina. The Pre-Processing stage equalizes the uneven illumination associated with fundus images and also removes noise present in the image. Segmentation stage clusters the image into two distinct classes while the Disease Classifier stage was used to distinguish between candidate lesions and other information. Method of diagnosis of red spots, bleeding and detection of vein-artery crossover points were also developed in this work using the colour information, shape, size, object length to breadth ration as contained in the digital fundus image in the detection of this disease. In addition to diagnosis of Diabetic Retinopathy (DR), two graphical user interfaces (GUI’s) were also developed during this work, this first is for collection of lesion data information and was used by the ophthalmologist in marking images for database while the second GUI is for automatic diagnosing and displaying the diagnosis result in a more friendly user interface and is as shown in chapter three of this report. The algorithm was tested with a separate set of 25 fundus images. From this, the Receiver Operating Characteristics (ROC) was determined for red spot disease and bleeding, while cross over points were only detected leaving further classification as part of future work needed to complete this global project. Sensitivity (classify abnormal fundus images as abnormal) and specificity (classify normal fundus image as normal) was calculated for the algorithm is given as 98% and 61%.

  • 176. Iqbal, Muhammad Imran
    et al.
    Aibinu, A.M.
    Nilsson, Mikael
    Tijani, I. B.
    Salami, M.J.E.
    Detection of Vascular Intersection in Retina Fundus Image Using Modified Cross Point Number and Neural Network Technique2008Conference paper (Refereed)
    Abstract [en]

    Vascular intersection can be used as one of the symptoms for monitoring and diagnosis of diabetic retinopathy from fundus images. In this work we apply the knowledge of digital image processing, fuzzy logic and neural network technique to detect bifurcation and vein-artery cross-over points in fundus images. The acquired images undergo preprocessing stage for illumination equalization and noise removal. Segmentation stage clusters the image into two distinct classes by the use of fuzzy c-means technique, neural network technique and modified cross-point number (MCN) methods were employed for the detection of bifurcation and cross-over points. MCN uses a 5x5 window with 16 neighboring pixels for efficient detection of bifurcation and cross over points in fundus images. Result obtained from applying this hybrid method on both real and simulated vascular points shows that this method perform better than the existing simple cross-point number (SCN) method, thus an improvement to the vascular point detection and a good tool in the monitoring and diagnosis of diabetic retinopathy. ©2008 IEEE.

  • 177. Iqbal, Muhammad Imran
    et al.
    Zepernick, Hans-Jürgen
    Engelke, Ulrich
    Error Sensitivity Analysis for Wireless JPEG2000 Using Perceptual Quality Metrics2008Conference paper (Refereed)
    Abstract [en]

    Quality assessment of mobile and wireless multimedia services including image and video applications has gained increased attention in recent years as a means of facilitating efficient radio resource management. In particular, approaches that utilize perceptual-based metrics are becoming more dominant, as conventional fidelity metrics such as the peak signal-to-noise ratio (PSNR) may not correlate well with quality as perceived by the human observer. In this paper, we focus on the error sensitivity analysis for images given in the wireless JPEG2000 (JPWL) format using perceptual quality metrics. Specifically, the perceptual quality improvements obtained by progressively decoding an increasing number of image packets are examined. It is shown that the considered perceptual quality metrics exploiting structural image features may accompany or replace the PSNR-based error sensitivity description (ESD) marker segment in the wireless JPEG2000 standard. This addition will increase the effectiveness of the ESD marker segment as it facilitates the communication of reduced-reference information about the image quality from the transmitter to the receiver. In addition, the proposed approach can be used to guide the design of preferential error control coding schemes, link adaptation techniques, and selective retransmission of packets with respect to their contribution to overall quality as perceived by humans.

  • 178. Isaksson, Lennart
    et al.
    Fiedler, Markus
    On-Demand Ad Hoc Routing with Modified Reverse Path Forwarding for Bluetooth2004Conference paper (Refereed)
    Abstract [en]

    In an ad hoc network connection establishment is done to secure a path for routing packets from source to destination. This path is then maintained to secure further transmissions. In the case of Wireless Personal Area Networks (WPAN) which are more flexible, this is not usable. This is especially the case for Bluetooth. Some constraints in Bluetooth demands a more flexible on-demand ad hoc network compared to other types of ad hoc network protocols. Initially we found that creating a scatternet is not practically possible using Bluetooth version 1.1. The slave/slave bridge is not implemented into the hardware to create a scatternet. In this paper, we present a modified version of the Reverse Path Forwarding (RPF) algorithm to make it suitable for Bluetooth routing. With an on-demand ad hoc network solution together with the modified RPF algorithm we present a suitable solution for Bluetooth packets to be routed in a flexible ad hoc network. To be able to test the modified RPF and the on-demand ad hoc network, a test platform has also been developed.

  • 179. Isaksson, Lennart
    et al.
    Fiedler, Markus
    Optimization of the Random Backoff Boundary of the Bluetooth FHSS Technique2005Conference paper (Refereed)
    Abstract [en]

    The goal of an ad hoc network is to create a wireless connection when needed between nodes. Regarding Bluetooth (IEEE 802.15.1) the so-called state machine based on the selection box is responsible for the Frequency Hopping (FH). In this state machine a particular sub-state (random backoff) is heavily involved in the time-to-connect between two devices.

  • 180. Jamil, Momin
    et al.
    Zepernick, Hans-Jürgen
    Pettersson, Mats
    On Integrated Radar and Communication Systems Using Oppermann Sequences2008Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider the design of integrated radar and communication systems that utilize weighted pulse trains with the elements of Oppermann sequences serving as complex-valued weights. An analytical expression of the ambiguity function for weighted pulse trains with Oppermann sequences is derived. Given a family of Oppermann sequences, it is shown that the related ambiguity function depends only on one sequence parameter. This property simplifies the design of the associated weighted pulse trains as it constrains the degrees of freedom. In contrast to the single polyphase pulse compression sequences that are typically deployed in radar applications, the families considered in this paper form sets of sequences. As such, they readily facilitate also multiple-access in communication systems. Numerical examples are provided that show the wide range of options offered by Oppermann sequences in the design of integrated radar and communication systems.

  • 181. Jamil, Momin
    et al.
    Zepernick, Hans-Jürgen
    Pettersson, Mats
    Performance Assessment of Polyphase Pulse Compression Codes2008Conference paper (Refereed)
    Abstract [en]

    The performance of conventional polyphase pulse compression codes such as the Frank, Frank-Zadoff-Chu (FZC), P1, P2, P3, P4, and Px codes will be compared with Oppermann codes. While the majority of the former code classes focus on radar applications, Oppermann codes have been discussed only within the context of code-division multiple-access (CDMA) systems. In this paper, we therefore consolidate findings on the conventional codes and extend the performance assessment to Oppermann codes by accounting for Doppler shifts as needed in radar applications. It is shown that Oppermann codes can conceptually support integrated radar and communication systems as compared to the P1, P2, P3, P4, and Px codes where this is not readily feasible. The numerical results given here illustrate that Oppermann codes outperform Px codes in the presence of Doppler shifts as supported by the ambiguity function.

  • 182.
    Johansson, Anders
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Acoustic Sound Source Localisation and Tracking: in Indoor Environments2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    With advances in micro-electronic complexity and fabrication, sophisticated algorithms for source localisation and tracking can now be deployed in cost sensitive appliances for both consumer and commercial markets. As a result, such algorithms are becoming ubiquitous elements of contemporary communication, robotics and surveillance systems. Two of the main requirements of acoustic localisation and tracking algorithms are robustness to acoustic disturbances (to maximise localisation accuracy), and low computational complexity (to minimise power-dissipation and cost of hardware components). The research presented in this thesis covers both advances in robustness and in computational complexity for acoustic source localisation and tracking algorithms. This thesis also presents advances in modelling of sound propagation in indoor environments; a key to the development and evaluation of acoustic localisation and tracking algorithms. As an advance in the field of tracking, this thesis also presents a new method for tracking human speakers in which the problem of the discontinuous nature of human speech is addressed using a new state-space filter based algorithm which incorporates a voice activity detector. The algorithm is shown to achieve superior tracking performance compared to traditional approaches. Furthermore, the algorithm is implemented in a real-time system using a method which yields a low computational complexity. Additionally, a new method is presented for optimising the parameters for the dynamics model used in a state-space filter. The method features an evolution strategy optimisation algorithm to identify the optimum dynamics’ model parameters. Results show that the algorithm is capable of real-time online identification of optimum parameters for different types of dynamics models without access to ground-truth data. Finally, two new localisation algorithms are developed and compared to older well established methods. In this context an analytic analysis of noise and room reverberation is conducted, considering its influence on the performance of localisation algorithms. The algorithms are implemented in a real-time system and are evaluated with respect to robustness and computational complexity. Results show that the new algorithms outperform their older counterparts, both with regards to computational complexity, and robustness to reverberation and background noise. The field of acoustic modelling is advanced in a new method for predicting the energy decay in impulse responses simulated using the image source method. The new method is applied to the problem of designing synthetic rooms with a defined reverberation time, and is compared to several well established methods for reverberation time prediction. This comparison reveals that the new method is the most accurate.

  • 183.
    Johansson, Jimmy
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Tang, Jessica
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Nilsson, Erica
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Aktiv bullerdämpning i ventilationssystem2005Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Examensarbetet utfördes på Avdelningen för signalbehandling vid Blekinge Tekniska Högskola i samarbete med företaget Lindab AB i Båstad. Arbetet är en vidareutveckling av tidigare examensarbete på institutionen. Intresset för bullerdämpning har ökat dramatiskt på senare tid, då forskning visat bullrets negativa inverkan på folk. Buller är inte bara skadligt för hörseln, utan kan även vara psykiskt påfrestande och ger upphov till trötthet och huvudvärk. För att undertrycka buller i t.ex. ventilationskanaler, används i dagsläget nästan enbart passiva dämpare, d.v.s. dämpare med poröst material som absorberar buller. Problemet med dessa dämpare är att de endast dämpar effektivt ner till ca 300 Hz. Eftersom våglängderna under denna frekvens är längre än en meter, skulle det krävas väldigt stora dämpare för att kunna absorbera buller i detta frekvensområde. Det aktiva systemet fungerar bra upp till ca 400 Hz, vilket gör att en kombination av dessa dämpare skulle vara en mer komplett lösning. Principen för aktiv bullerdämpning är att dämpa buller med hjälp av ”motbuller”. En eller ett antal referensmikrofoner, placerade på lämpliga ställen, används för att mäta ljudet. Dessa mätvärden behandlas i signalprocessorer, varefter motljud alstras i en eller flera strategiskt placerade högtalare. Ju mer exakt motbuller vi kan alstra, desto bättre blir effekten och desto tystare blir det. Till hjälp att ställa in ”motljudet” används en eller flera felmikrofoner, runt vilka en ljuddämpning erhålles. Tekniken börjar användas alltmer inom områden som t.ex. i fläkttrummor och bilar. Men för att tekniken ska slå igenom, krävs det bättre prestanda till ett bättre pris. Tidigare examensarbetare har lyckats få en bra dämpning med relativt billiga komponenter genom att placera det aktiva systemet precis vid mynningen innan luften går ut i rummet. En vindavledare har tillverkats m.h.a. ett cigarrfodral, vilket resulterade i att en billig mikrofon med egentillverkad vindavledare gav systemet minst lika bra prestanda som en dyr, kalibrerad mikrofon. Vårt examensarbete har främst varit inriktad på experiment med olika konfigurationer - att komma fram till vilken uppställning eller inställning som ger systemet bäst prestanda. Vi undersökte bl.a. hur nära böjen kunde vara, efter felmikrofonen, utan att påverka systemets prestanda. Våra mätningar visade att ju kortare längd efter felmikrofonen, desto bättre dämpning. Tester gjordes även på olika längder på det adaptiva FIR-filtrets koefficientvektor, där en koefficientlängd på 128 var den mest gynnsamma i våra experiment. Vi reglerade både temperaturen i rummet och flödeshastigheter i ventilationskanalen för att se om det påverkade dämpningen av systemet. När det var 15°C i rummet fördröjdes impulssvaret i systemet en aning i förhållandet till impulssvaret vid 30°C i rummet. Dock förändrades dämpningen marginellt. Vad gäller flödeshastigheter så undertrycktes bullret bäst när flödeshastigheten i ventilationskanalen var på 2.8 m/s. Ytterligare en referensmikrofon infördes för att undvika eventuella stående vågor. Dock fick vi snarlika resultat som om vi bara hade haft en referensmikrofon. I sista experimentet varierades ventilationskanalens diameter runt felmikrofonen. Detta gjordes för att undvika ev. turbulens runt mikrofonen. Bäst prestanda fick vi när ventilationskanalens diameter vid felmikrofonen var 40 cm. Det övriga systemet hade en diameter på ca 30 cm.

  • 184. Johansson, Sven
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Aircraft Cabin Noise and Vibration Prediction and Active Control2007In: HANDBOOK OF NOISE AND VIBRATION CONTROL / [ed] Crocker, Malcolm J., New York: John Wiley & Sons , 2007Chapter in book (Other academic)
  • 185. Johansson, Sven
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    AIRCRAFT CABIN NOISE AND VIBRATION PREDICTION AND ACTIVE CONTROL2005In: HANDBOOK OF NOISE AND VIBRATION CONTROL / [ed] Crocker, Malcolm J., New York: To be published by John Wiley & Sons , 2005Chapter in book (Other academic)
    Abstract [en]

    The active control of noise and vibration in passenger aircraft cabins generally rely on adaptive multi channel feedforward control of disturbing acoustic cabin modes based on a set of control sources and error sensors with optimized locations, or on feedback control in active headsets or in quiet seats. The structural aircraft fuselage vibrations produced by the propulsion system and turbulence pressure fluctuations acting on the external fuselage generally excite the interior cabin sound field. Cabin noise in turboprop aircraft and jet aircraft with tail-mounted engines are usually dominated by tonal noise related to the fundamental blade passage frequency and the jet engine spool imbalance frequencies respectively. The jet noise -engine exhaust noise- and turbulent boundary layer noise, on the other hand, have broadband characteristics. The active control of tonal noise in aircraft is of global character and involves multi channel active noise control or multi channel active structural acoustic control. The locations of the secondary sources and error sensors are optimized for the acoustic noise attenuation over a range of flight conditions and are selected from a set of potential configurations. Generally, the active control systems for reducing the tonal cabin noise are based on variants of the multi channel Filtered-X LMS algorithm, and both time domain and frequency domain algorithms are used. Feedback control in active headsets or in silent seats addresses the broadband cabin noise.

  • 186. Jung, Younchan
    et al.
    Atwood, J. William
    Zepernick, Hans-Jürgen
    Improving VoIP Quality Using Silence Description Packets in the Jitter Buffer2008In: IEICE transactions on communications, ISSN 0916-8516, E-ISSN 1745-1345, Vol. E91-B, no 11Article in journal (Refereed)
    Abstract [en]

    The basic playout scheme (BAS) is designed not to take into account network impairment information during silence periods. We propose a jitter-robust playout mechanism (RST), which uses silence description (SID) packets. The lateness loss percentages are compared between the BAS and the RST algorithms. We report that the accuracy of the playout schedule calculation in the BAS is getting worse as the previous silence interval increases and our proposed RST algorithm is more effective in removing high jitter than the BAS. Under high jitter Internet conditions, the accuracy of the estimates and therefore the resulting of VoIP playout quality can be significantly improved by using the SID packets in the playout schedule recalculation.

  • 187.
    Kabodi, Azad
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Development and simulation of a Hamiltonian observer for an industrial application2008Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In this thesis work a fourth order and a third order Hamiltonian observer are presented. The observers are developed for the series loaded resonant converter and the performance of the observers has been studied under different conditions by simulating the system. This thesis addresses questions of importance when a control system should be implemented on an FPGA.

  • 188.
    Karlsson, Magnus
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Distansövervakning av givare i hemmet2005Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [sv]

    Examensarbetet belyser så väl fördelar som nackdelar under utveckling av USB-enheter med PIC processorn PIC16C745 som grund. Processorn används i detta projekt för att möjliggöra en effektiv distansövervakning via USB gränssnittet. I detta projekt har en USB-enhet konstruerats med uppgiften att leverera data från olika givare till en PC. Vidare publiceras dessa data på Internet via en webbserver. Givarna är av typen analoga och binära. Till de analoga givarna hör två stycken temperatur- och en ljusgivare. De binära givarna är till för att mäta om dörrar och/eller fönster är öppna eller stängda. Informationsflödet från givarna går via en centralenhet baserad på PIC16C745 enheten, genom en PC med Windows XP och en webbserver. Slutligen når informationen vidare till den aktuella besökaren via Internet och en webbläsare. Gränssnittet mot besökaren är en ren webbsida med grafer, som uppdateras med ett visst tidsintervall. Resultatet av examensarbete har vart lyckosamt då all implementation och konstruktion ebbat ut i ett fungerande system för övervakning av hemmet.

  • 189. Karlsson, Magnus
    et al.
    Holmberg, Torbjörn
    Hultgren, Anders
    Lenells, Matz
    A Structural Modeling Flow for Switched Electrical Networks2009Conference paper (Refereed)
    Abstract [en]

    A structural flow for modeling of switched electrical circuits by means of an example a switched DC/DC converter will be presented. The modeling flow has a minimal amount of hand calculations and is suitable for script implementation in suitable mathematical computer software such as Matlab or similar. Switched Hamiltonian Differential Algebraic Equation models and Differential Equation models are obtained which are suitable for analysis in the time domain. Linear models, which can be transformed to the frequency domain for analysis, are obtained from the Hamiltonian models. The duty cycle will be included in the input vector enabling the full system analysis considering the system transfer functions audio susceptibility, output impedance, and control, i.e., the duty cycle to output voltage.

  • 190. Kathir, Kamal
    et al.
    Mohammed, Abbas
    Erman, Maria
    Cooperative Communications2009Conference paper (Refereed)
  • 191.
    Khalid, Farhan
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Real-time Modeling and Analysis of a Multiple-Input-Multiple-Output (MIMO) Wireless System over Acoustic Channel2005Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Multiple-input-multiple-output (MIMO) wireless systems employ multiple transmitter and receiver antennas, and offer a manifold increase in system capacity and improvement in signal quality, as compared to conventional wireless systems being used at present. MIMO uses spatial multiplexing and exploits multipath propagation to its benefit for increasing system capacity as opposed to conventional wireless systems, while the spatial diversity at the transmitter as well as the receiver ensures better signal quality in terms of the bit-error rate (BER). This thesis is concerned with the modeling and analysis of a MIMO wireless system using the air acoustic transmission channel. Various performance measures have been carried out on this system in real-time and the results analyzed. The system has been modeled for a stationary indoor environment and demonstrates the application of MIMO principles for data rate maximization. The designed system is a 2 x 2 MIMO digital transmission system which simultaneously transmits two independent BPSK modulated bit streams. This system makes use of a Singular Value Decomposition (SVD) based MIMO equalization scheme which requires the channel state information (CSI) to be known at the transmitter. Therefore, MIMO channel estimation is also part of the implementation. The acoustic transmission channel varies considerably from the radio channel. It uses a low carrier frequency and supports very low data rates. In addition, the multipath delay spread may be significantly larger due to slow propagation speed of acoustic waves over large distances. It is comparatively more difficult to model the acoustic channel and multiple filter taps are required for better channel estimation. However, the MIMO principles are equally valid for the acoustic channel as indicated by the results presented in this thesis.

  • 192.
    Khan, Muhammad Adnan
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Shinwari, Naseer-Ud-Din
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Analysis and simulation of channel equalization in TDD-CDMA2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The field of telecommunications has made tremendous progress of the past decade, especially in the area of wireless communications. The world becoming a global village due the advancement in the field of wireless communications, the requirement for standardization and uniformity becomes an essential issue. CDMA is the efficient technology that has emerged in the last decade and has revolutionized the pre-existing mobile communication concepts. CDMA is a spread spectrum-based technique for multiplexing, that provides and alternative to TDMA for Second Generation cellular networks. In FDD-CDMA the uplink and downlink transmissions use two separate frequency bands for duplex transmission. It would be correct to call TDD-CDMA as one of the flavors of CDMA technology and has taken the concept to a whole new level of performance, simplicity and cost effectiveness. In TDD-CDMA, the uplink and downlink transmissions use the same frequency band for duplex transmission by using synchronized time intervals. The TDD-CDMA (TD_CDMA) is very similar to FDD CDMA on all of its higher-level functionality. The major differences are in the physical layer, where TDD-CDMA combines TDMA and CDMA elements while FDD-CDMA combine FDMA and CDMA elements. This Research will focus on different features of TDD-CDMA and implementing channel equalization in Matlab. Channel equalization: In channel Equalization we implement the channel estimation algorithm to equalize the channel and reduce the BER in the received signal. The Channel equalization is carried out at the receiver.

  • 193. Khan, Muhammad Gufran
    On Coherent and Non-coherent Receiver Structures for Impulse Radio UWB Systems2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The demand and growth of short-range wireless communications has been tremendous in the past few years for a diverse range of applications. There is significant interest in ultra wideband (UWB) as a physical layer technology for both high-data-rate (HDR), and low power, low-data-rate (LDR) short-range communications. The unique qualities of UWB such as large bandwidth, very low power spectral density (PSD) and fine time-resolution provide higher channel capacity, reduced fading effects and position location capability in a UWB system. The extremely wide bandwidth of UWB systems also poses many system design challenges to achieve low cost and low-complexity UWB devices. The UWB systems have difficulties in using digital signal processing (DSP) technology, require high sampling frequencies and also face frequency dependent signal distortion. The propagation characteristics of UWB signals also require consideration as it differs significantly from traditional narrowband systems. In this thesis, the issue of design and performance evaluation of coherent and non-coherent receivers for detection of impulse radio (IR) UWB signals is addressed. The coherent RAKE and non-coherent transmitted reference (TR) receiver structures are investigated for low power and low-data-rate wireless sensor network applications. First, the performance of coherent RAKE receivers for a single-user system operating in non-line-of-sight (NLOS) scenarios in an industrial environment is evaluated. The results and performance comparison is presented for partial RAKE (PRake) and selective RAKE (SRake) using maximal ratio combining (MRC) and equal gain combining (EGC). Secondly, the recursive structures of conventional TR and averaged TR schemes are presented to decrease the performance loss associated with the low-complexity TR scheme for IR-UWB systems. Further, a doublet-shift TR (DSTR) signaling and detection scheme is presented for IR-UWB systems. The simulation results validate that the doublet-shift TR signaling scheme improves the performance over conventional TR signaling scheme. Finally, dual-doublet TR (DDTR) signaling and detection schemes are proposed. The proposed dual-doublet TR schemes recover 25 to 50% energy/rate loss of conventional TR scheme. The performance of receiver structures is evaluated in terms of uncoded bit-error-rate (BER) over the channels measured in a medium-sized industrial environment and standard IEEE 802.15.4a multipath channels.

  • 194. Khan, Muhammad Gufran
    et al.
    Ashraf, Asim A.
    Karedal, Johan
    Tufvesson, Fredrik
    Molisch, Andreas F.
    Measurements and Analysis of UWB Channels in Industrial Environments2005Conference paper (Refereed)
    Abstract [en]

    Communication in industrial environments is an important scenario for ultra wideband (UWB) systems. The characteristics of this environment differ considerably from office environments, where most of the channel measurements reported in the literature are performed. In this paper, we present the results and analysis of UWB channel measurements in an industrial environment. We investigate both peer-to-peer non-line-of-sight (P-P NLOS) and base station NLOS (BS NLOS) scenarios. The measurements are performed in the frequency range 3.1 to 8 GHz, at distances 2-16 m, using a vector network analyzer in conjunction with virtual antenna arrays. From these measurements, we extract channel model parameters such as power delay profiles, pathloss exponents, rms delay spread and the percentage of energy captured by RAKE receivers with a finite number of fingers. In addition, Saleh- Valenzuela parameters such as ray and cluster power decay constants and distribution of cluster interarrival times are extracted.

  • 195. Khan, Muhammad Gufran
    et al.
    Nordberg, Jörgen
    Performance Evaluation of RAKE Receiver for Low Data Rate UWB Systems using Multipath Channels for Industrial Environments2008Report (Other academic)
    Abstract [en]

    Since US FCC passed a resolution in 2002 allowing ultra wideband (UWB) transmissions within a specified unlicensed spectral mask, the interest in UWB technology has grown tremendously. The large bandwidth, low power spectral density (PSD), high multiple access capability and high resolution are some qualities of UWB technology. For UWB communication systems, the industrial environments are an important scenario. However, due to large number of metallic scatterers in the environment, the multipath offered by UWB channels is dense and many multipath components have significant energy. In this report, the performance evaluation of RAKE receivers for a single user system operating in non-line-of-sight (NLOS) scenarios in industrial environments is presented. The channels used for the evaluation are measured in a medium-sized industrial environment. In addition, the standard IEEE 802.15.4a channel model for NLOS industrial environment is used for comparison with the results of the measured channels. The performance is compared for partial RAKE (PRake) and selective RAKE (SRake) in terms of uncoded bit-error-rate (BER) with the assumption that the channel is known. The effect of different number of fingers on BER of PRake and Srake is studied. Moreover, the performance of maximal ratio combining (MRC) and equal gain combining (EGC) is compared for PRake and Srake receiver. The results also provide a performance comparison between different Tx-Rx separations. Finally, based on the simulation results, conclusions are presented considering the performance and complexity issues.

  • 196. Khan, Muhammad Gufran
    et al.
    Nordberg, Jörgen
    Recursive Transmitted Reference Receivers for Impulse Radio UWB Systems2008Report (Other academic)
    Abstract [en]

    For the detection of impulse radio (IR) UWB signals, RAKE receivers or transmitted reference (TR) autocorrelation receivers can be used. The complexity of RAKE receiver increases significantly when the number of received multipath components is large. The TR scheme is a low-complexity alternative as it does not require channel estimation. However, there is a performance loss associated with the low-complexity TR scheme. The recursive structures of the conventional TR and averaged TR schemes are presented to improve the detection performance of IR-UWB signals. The performance of proposed schemes is evaluated over the standard IEEE 802.15.4a multipath channels. The performance is compared with conventional TR receivers in terms of uncoded bit-error-rate (BER), assuming that the channel is quasi-static. For averaged and recursive averaged TR schemes, the TR sequence is also slightly modified. The simulation results validate that the proposed schemes have better performance by about 2 dB than the conventional TR and averaged TR receivers.

  • 197. Khan, Muhammad Gufran
    et al.
    Nordberg, Jörgen
    Claesson, Ingvar
    A Doublet-Shift Transmitted Reference Scheme for Ultra-Wideband Communication Systems2007Conference paper (Refereed)
    Abstract [en]

    The transmitted reference (TR) scheme has gained attention for ultra-wideband (UWB) communications as it bypasses the complex task of channel estimation and provides a simple receiver structure. However, the low-complexity detection in this scheme is achieved at the expense of a loss in performance. To this end, this paper proposes a doublet-shift TR (DsTR) signaling and detection scheme to improve the performance of conventional TR impulse radio UWB system. The performance of the proposed scheme is compared with conventional TR signaling scheme in terms of uncoded bit error rate (BER). The simulation results validate that the doublet-shift TR scheme achieves about 1.5-2 dB better performance than the conventional TR scheme. The DsTR scheme does not require extra energy and still has the low-complexity.

  • 198. Khan, Muhammad Gufran
    et al.
    Nordberg, Jörgen
    Claesson, Ingvar
    An energy-efficient signaling and detection scheme for transmitted reference UWB systems2008Conference paper (Refereed)
    Abstract [en]

    The transmitted reference (TR) schemes do not require the complex task of channel estimation and provide a simple receiver structure. However, the low-complexity detection in conventional TR scheme is achieved at the expense of 50% energy/rate loss. In this paper, an energy-efficient TR signaling and detection scheme is presented with the aim to improve the performance of conventional TR impulse radio UWB system. The proposed scheme is a combination of the conventional TR scheme and the differential TR scheme. The simulation results validate that the proposed TR scheme utilizes 1.76 dB less energy per bit and recovers 25% rate loss of conventional TR scheme, while maintaining the same BER performance. Further, the proposed ATR scheme improves the BER performance by about 2 dB using simple averaging of the reference pulses. ©2008 IEEE.

  • 199. Khan, Muhammad Gufran
    et al.
    Nordberg, Jörgen
    Claesson, Ingvar
    Detection of Impulse Radio Ultra-Wideband Signals using Recursive Transmitted Reference Receivers2007Conference paper (Refereed)
    Abstract [en]

    For the detection of impulse radio (IR) UWB signals, complex RAKE receiver or low-complexity transmitted reference (TR) autocorrelation receivers can be used. However, there is a performance loss associated with the low-complexity TR scheme. This paper proposes recursive structures of the conventional TR and averaged TR schemes to improve the detection performance of IR-UWB signals. The performance of proposed schemes is evaluated over the standard IEEE 802.15.4a multipath channels. The performance is compared with conventional TR receivers in terms of uncoded bit-error-rate (BER), assuming that the channel is quasi-static. For averaged and recursive averaged TR schemes, the TR sequence is also slightly modified. The simulation results validate that the proposed schemes has better performance by about 2 dB than the conventional TR and averaged TR receivers.

  • 200. Khan, Muhammad Gufran
    et al.
    Nordberg, Jörgen
    Mohammed, Abbas
    Claesson, Ingvar
    Performance Evaluation of RAKE Receiver for UWB Systems using Measured Channels in Industrial Environments2006Conference paper (Refereed)
    Abstract [en]

    The industrial environments are an important scenario for ultra wideband (UWB) communication systems. However, due to large number of metallic scatterers in the surroundings, the multipath offered by UWB channels is dense with significant energy. In this paper, the performance of RAKE receivers operating in a non line-of-sight (NLOS) scenario in these environments is evaluated. The channels used for the evaluation are measured in a medium-sized industrial environment. In addition, a standard IEEE 802.15.4a channel model is used for comparison with the results of the measured data. The performance of partial RAKE (PRake) and selective RAKE (SRake)is evaluated in terms of uncoded bit-error-rate (BER) using different number of fingers. The performance of maximal ratio combining (MRC) and equal gain combining (EGC) is compared for the RAKE receiver assuming perfect knowledge of the channel state. Finally, based on the simulation results, conclusions are drawn considering the performance and complexity issues for system design in these environments.

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