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  • 1.
    Andersson, Roger
    et al.
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Sjölander, Torbjörn
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Forming a common addressing algorithm for digital CAS register signalling1998Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [en]

    The purpose of this thesis work was to examine the possibility to implement a common addressing algorithm in the digital CAS trunk line programs used at the call setup in an originating exchange. The algorithm formed is described in an SDL-flow and in PLEX-M software code. As result of the thesis work, the addressing parts in some of the trunk line programs was replaced by the designed common algorithm and successfully verified in target machine in MD-laboratory. The amount of code was reduced in all of the tested trunk line programs.

  • 2. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Active Control of Boring Bar Vibrations Using the Leaky Feedback Filtered X-LMS2003Conference paper (Refereed)
    Abstract [en]

    The boring operation is a cumbersome manufacturing process marred by noise and vibration related problems. The manufacturing industry is having trouble with these kinds of metal cutting operations. There exist several approaches to reduce the vibrations in cutting operations in general. Passive tuned dampers in boring bars have been commercially available for some time. An active solution is likely to be more robust to changes in the spectral content, where the passive counterpart have a small operable area, the active solution is able to adapt to these kinds of changes. Active vibration control in boring operations has been proven to be feasible. The algorithm used in the successful experiments was the feedback filtered X-LMS algorithm. This algorithm does however not guarantee a stable behavior, but incorporating a leakage factor will make the algorithm more robust. Power spectral density of boring bar vibration of real cutting experiments show that the leaky filtered X-LMS algorithm is a possible candidate to be a suitable control algorithm. Nyquist diagrams of the controller during operation show that the stability is increased significantly.

  • 3. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Active Control of Machine Tool Vibrations in External Turning Operations2003In: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 217, no 6, p. 869-872Article in journal (Refereed)
    Abstract [en]

    Vibration and noise in metal cutting are ubiquitous problems in the workshop. The external turning operation is one kind of metal cutting that exhibits vibration related problems. Severe noise is also a problem growing in proportion due to regulations in preventing hearing loss. Active vibration control is a potential solution to such problems. With the piezo ceramic actuator technology of today, the size of the actuator can be kept small and still be able to produce a sufficient amount of force for the anti vibrations. Results from several continuous cutting experiments show a 40 dB reduction of the cutting tool vibration level. The design of the active technique enables this technology to be applicable to a general lathe provided the mounting arrangement is fairly similar.

  • 4. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Performance Evaluation of Active Vibration Control of Boring Operations Using Different Active Boring Bars2003Conference paper (Refereed)
    Abstract [en]

    Vibration and noise in boring operations are ubiquitous problems in the workshop. In boring operations, the boring bar is subjected to forces from both the cutting speed and the cutting depth direction. To solve the vibration problem using active techniques would normally require two actuators in order to enable the control of both directions. By mounting one actuator in between the cutting speed and the cutting depth direction it is possible to achieve an active control solution with one actuator. Using only one actuator not only simplifies the control algorithm and saves extra equipment but is also favourable in terms of modifications of the boring bar. The harsh environment in a lathe more or less requires that both sensors and actuators are embedded and sealed into the boring bar. Since the forces that are to be controlled are large, the space needed for the actuator is substantial. Thus using only one actuator will keep the modified boring bar stiffer than a two actuator design. Three boring bars with the actuator mounted at different angles between the cutting speed and the cutting depth directions have been tested. Results from cutting experiments show that the one actuator solution has good potentials to the vibration problem in boring operations.

  • 5. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    Piezo Ceramic Actuators versus High Magnetostrictive Actuators in the Active control of Tool Vibration1999Conference paper (Refereed)
    Abstract [en]

    In the turning operation chatter or vibration is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. In the active control system for the control of tool vibration a tool holder construction with integrated high magnetostrictive actuators was used. However, high magnetostrictive actuators generally have a non-linear behavior and it is a well known fact that non-linear properties in the forward path in an active control system is likely to degrade the robustness of the control system. A new generation embedded active tool holder shanks based on piezo ceramic actuators has been developed. Based on spectrum estimates, both coherence spectrum and frequency response function estimates has been calculated for both the old tool holder construction and the new generation active tool holder shank. From the results it follows that the phase delay is smaller and the linearity of the new generation active tool holder shank are superior compared to the old technology. The physical features and properties of the new generation active tool holders are superior to the old tool holder.

  • 6.
    Bergstrand, Catharina
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Parallellpublicering2002Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Examensarbete är utfört för Gothia System Office AB och innebar att analysera och ta fram ett exempel på hur parallellpublicering fungerar. Parallellpubliceringsexemplet är baserat på Oracle 8.1.7 databas som är implementerad med testdata via script. Själva Parallellpubliceringsprogrammet är skrivet i Java och dess uppgift är att publicera data från databasen med olika utseende beroende på vad man skall använda det till. Utmatning av data från databasen sker via XML som sedan tillförs ett XSL style sheet, eller bearbetas om, av Java-applikation för det slutgiltiga målet. Programvaran som används för att utveckla Java-applikationen är JDeveloper 3.2 och för att framställa dataanalysen, UML = Unified Modeling Language, så används Together 5.02.

  • 7. Brandt, Anders
    A Digital Filter Method for Forced Response Computation2003Conference paper (Refereed)
    Abstract [en]

    Transient forced response of mechanical structures is usually computed using time domain integration. This is often computationally costly, and the numerical precision and stability are concerns. In the present paper, a novel method based on modal superposition, using a new digital filter implementation, is presented. Poles and residues of the model are used as input data, which allows for using data from a finite element model, a lumped parameter model, or from experimental modal analysis. Modal damping can be used if the damping matrix is unknown. With the proposed method, the frequency dependant error can easily be computed, and can be chosen arbitrarily small by selecting proper sampling frequency (time increment). The method is applicable to all linear structures and can be used for stationary or transient input data. Simulation results show that the new method is superior to the alternative methods, at less computational cost.

  • 8. Brandt, Anders
    et al.
    Ahlin, Kjell
    Lagö, Thomas L
    Noise and vibration measurement system basics2006In: SOUND AND VIBRATION, ISSN 0022-460X , Vol. 40, no 4, p. 9-11Article in journal (Refereed)
  • 9. Burakowski, Wojciech
    et al.
    Krieger, Udo R.
    Leibnitz, Kenji
    Beben, Andrzej
    Meo, Michela
    Ors, Tolga
    Garcia-Vidal, Jorge
    Fiedler, Markus
    An overview on activities on wireless networks on the European project COST 2572000Conference paper (Refereed)
    Abstract [en]

    The paper summarises the work on wireless networks inside the COST 257 project, entitled “Impact of new services on the architecture and performance of broadband networks” and chaired by Prof. Tran-Gia of the Technical University of Wurzburg (Germany). This project was established for 4 years (1996-2000) and collected the researchers from 16 European countries represented by 32 organisations. Its topics are modelling, performance, network planning and the analysis of present and future wireless systems.

  • 10. Carlsson, Patrik
    Multi-Timescale Modelling of Ethernet Traffic2003Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ethernet is one of the most common link layer technologies, used in local area networks, wireless networks and wide area networks. There is however a lack of traffic models for Ethernet that is usable in performance analysis. In this thesis we describe an Ethernet traffic model. The model aims at matching multiple moments of the bit rate at several timescales. To match the model parameters to measured traffic, four methods have been developed and tested on real traffic traces. Once a model has been created, it can be used directly in a fluid flow performance analysis. Our results show that, as the number of sources present on an Ethernet link grows, the model becomes better and less complex.

  • 11. Carlsson, Patrik
    et al.
    Ekberg, Anders
    Fiedler, Markus
    On an Implementation of a Distributed Passive Measurement Infrastructure2003Other (Other academic)
    Abstract [en]

    Having access to relevant, up-to-date measurement data is a key issue for network analysis in order to allow for efficient Internet performance monitoring and management. New applications keep appearing; user and protocol behavior keep evolving; traffic mixes and characteristics are continuously changing, which implies that some year old traffic traces may not reflect reality any more. In order to give a holistic view of what is going on in the network, passive measurements have to be carried out at different places simultaneously. Other challenges relate to the simultaneous use of one specific measurement point at a certain location for different measurement processes, and to continuously ongoing measurements needed for capturing long-term traffic behaviors. On this background, this paper proposes a passive measurement infrastructure for a campus backbone, consisting of distributed coordinated measurement points, collected in measurement areas, measurement administration and data management. … The framework is generic with regards to the capturing equipment, ranging from simple PCAP based devices to high-end DAG cards, and dedicated ASICs, in order to promote a large deployment of measurement points. This structure allows for an efficient use of passive monitoring equipment in order to supply researchers and network managers with up-to-date and relevant data.

  • 12. Carlsson, Patrik
    et al.
    Fiedler, Markus
    Multifractal Products of Stochastic Processes: Fluid Flow Analysis2000Conference paper (Refereed)
    Abstract [en]

    The consideration of multifractal properties in network traffic has become a well-known issue in network performance evaluation. We analyze the performance of a fluid flow buffer fed by multifractal traffic described by Norros, Mannersalo and Riedi [1]. We describe specific steps in fluid flow analysis, both for finite and infnite buffer sizes, and point out how toovercome numerical problems. We discuss performance results in form of waiting time quantiles and loss probabilities, which help to estimate whether a trffic concentrator constitutes a bottleneck or not.

  • 13. Carlsson, Patrik
    et al.
    Fiedler, Markus
    Nilsson, Arne A.
    Matching Multi-Fractal Process Parameters Against Real Data Traffic2002Conference paper (Refereed)
    Abstract [en]

    Recent analyses of real data/internet traffic indicate that data traffic exhibits long-range dependence as well as self-similar or multi-fractal properties. By using mathematical models of Internet traffic that share these properties we can perform analytical studies of network traffic. This gives us an opportunity to analyse potential bottlenecks and estimate delays in the networks. Processes with multi-fractal properties can be modeled by multiplying the output of Markov Modulated Rate Processes (MMRP) [1] each defined by four parameters. The MMRP are easily used in stochastic fluid flow modeling. This model is also suited for analysis of other traffic types e.g. VoIP and thus, it allows for integration of different traffic types, i.e. time-sensitive voice traffic with best-effort data traffic. Using this model we can calculate performance parameters for each individual stream that enters the system/model. In this paper we show how to construct a multi-fractal process that is matched to measured data from MMRP sub processes.

  • 14. Carlsson, Patrik
    et al.
    Fiedler, Markus
    Tutschku, Kurt
    Chevul, Stefan
    Nilsson, Arne A.
    Obtaining Reliable Bit Rate Measurements in SNMP-Managed Networks2002Conference paper (Refereed)
    Abstract [en]

    The Simple Network Management Protocol, SNMP, is the most widespread standard for Internet management. As SNMP stacks are available on most equipment, this protocol has to be considered when it comes to performance management, traffic engineering and network control. However, especially when using the predominant version 1, SNMPv1, special care has to be taken to avoid erroneous results when calculating bit rates. In this work, we evalute six off-the-shelf network components. We demonstrate that bit rate measurements can be completely misleading if the sample intervals that are used are either too large or too small. We present solutions and work-arounds for these problems. The devices are evaluated with regards to their updating and response behavior.

  • 15. Claesson, Ingvar
    Dual Microphone input for Mobile Telephony2000Conference paper (Refereed)
  • 16. Claesson, Ingvar
    FFT i ett historiskt perspektiv1997Conference paper (Refereed)
    Abstract [en]

    Några nedslag i Fouriertransformens historia och FFT:ns ursprung från 1805 och framåt behandlas i denna populära betraktelse. Vi stannar upp ett slag hos Gauss, funderar över vad han gjort för oss ingenjörer och vi avslutar med en del praktiska konsekvenser och tips som är aktuella idag.

  • 17. Claesson, Ingvar
    et al.
    Dahl, Mattias
    Nordebo, Sven
    Applied Complex Chebyshev Optimization Using Dual Nested Complex Approximation2001Conference paper (Refereed)
  • 18.
    Claesson, Ingvar
    et al.
    Blekinge Institute of Technology, Department of Signal Processing.
    Håkansson, Lars
    Blekinge Institute of Technology, Department of Signal Processing.
    Lagö, Thomas L
    Robust Control of Machine-Tool Vibration in a Lathe1999Conference paper (Refereed)
    Abstract [en]

    In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration, is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced substantially by active control of the machine-tool vibration. Adaptive feedback control based on the filtered-x LMS-algorithm, enables a reduction of the vibration by up to 40 dB at 1.5 kHz and by approximately 40 dB at 3 kHz. The active control performeds a broadband attenuation of the sound pressure level by up to 35 dB. However, the process of machining a workpiece usually involves a variety of cutting data which in turn are likely to cause substantial variations in the spectral properties of the tool vibrations. Hence, variations in the spectral properties originates from changes in the excitation of the tool holder and changes in the structural response of the tool holder. To handle the potential large variations in the spectral properties of tool vibration in the turning operation the robustness of the control system has to be improved. By applying the leaky version of the filtered-x LMS algorithm in the active control of machine tool vibration it was found that the robustness of the adaptive control system was improved substantially to large variations in the spectral properties of tool vibration.

  • 19. Claesson, Ingvar
    et al.
    Nilsson, Andreas
    Cancellation of Humming GSM Mobile Telephone Noise2003Conference paper (Refereed)
    Abstract [en]

    A sometimes annoying problem in the most internationally widespread cellular telephone system, the GSM system, is an interfering signal generated by the switching nature of TDMA cellular telephone system. A humming noise originating from the speech frames, equivalent to 160 samples of data corresponding to 20 ms at 8 kHz sampling rate is sometimes clearly audible. This paper describes a study of two different software solutions designed to suppress such interference internally in the mobile handset. The methods are Notch Filtering, which is performed on a sample-per-sample basis, and Speech Frame Noise Cancellation, which is an alternative method employing correlators and subtraction, similar to Active Noise Control.

  • 20. Claesson, Ingvar
    et al.
    Nilsson, Andreas
    GSM TDMA Frame Rate Internal Active Noise Cancellation2003In: International Journal of Acoustics and Vibration, ISSN 1027-5851, Vol. 8, no 3, p. 159-166Article in journal (Refereed)
    Abstract [en]

    A common problem in the world's most widely-used cellular telephone system, the GSM system, is the interfering signal generated by the switching nature of TDMA cellular telephony in handheld and other terminals. Signals are sent as chunks of data, speech frames, equivalent to 160 samples of data corresponding to 20 ms at sampling rate of 8 kHz. This paper describes a study of two different software solutions designed to suppress such interference internally in the mobile handset. The methods are 1) notch filtering, which is multiplicative in frequency, and 2) subtractive noise cancellation, which is an alternative method employing correlators. The latter solution is a straigtforward, although somewhat unorthodox, application of "in-wire" active noise control. Since subtraction is performed directly in the time domain, and we have access to the state of the mobile, it is also possible to consider a recurring pause in the interference caused by the idle frame in the transmission, when the mobile listens to other base stations communicating. More complex control algorithms, based on the state of the communication between the handset and the base station, can be utilised.

  • 21. Dahl, Mattias
    Applied Array-Filter Design: Methods and Applications2000Doctoral thesis, comprehensive summary (Other academic)
  • 22. Dahl, Mattias
    On-Site Calibrated Microphone Array for Mobile Communication2000Conference paper (Refereed)
  • 23. Dahl, Mattias
    Speech Recognition in Severely Disturbed Environments Combining Ear-Mic and Active Noise Control2002Conference paper (Refereed)
  • 24. Dahl, Mattias
    et al.
    Claesson, Ingvar
    Nordebo, Sven
    Nordholm, Sven
    Chebyshev Optimization of Circular Arrays1999Conference paper (Refereed)
  • 25. Dahl, Mattias
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    A New General Front-End Technique for Complex Quadratic Programming: Applications to Array Pattern Synthesis2000Report (Other academic)
    Abstract [en]

    This paper presents a new practical approach to complex quadratic programming which solves the broad class of complex approximation problems employing finitization of semi-infinite formulations. The approximation problem may be general with arbitrarily complex basis functions. By using a new technique, the associated semi-infinite quadratic programming problem can be solved taking advantage of the numerical stability and efficiency of conventional quadratic programming software packages. Furthermore, the optimization procedure is simple to describe theoretically and straightforward to implement in computer coding. The new design technique is therefore highly accessible. The complex approximation algorithm is versatile and can be applied to a variety of applications such as narrow-band as well as broad-band beamformers with any geometry, conventional FIR filters, digital Laguerre networks, and digital FIR equalizers. The new algorithm is formally introduced as the quadratic Dual Nested Complex Approximation (DNCA) algorithm. The essence of the new technique, justified by the Caratheodory's dimensionality theorem, is to exploit the finiteness of the related Lagrange multipliers by adapting conventional finite-dimensional quadratic programming to the semi-infinite quadratic programming re-formulation of complex approximation problems. The design criterion in our application is to minimize the side-lobe energy of an antenna array when subjected to a specified bound on the peak side-lobe level. Additional linear constraints are used to form the main-lobe. The design problem is formulated as a semi-infinite quadratic program and solved by using the new front-end applied on top of a software package for conventional finite-dimensional quadratic programming. The proposed optimization technique is applied to several numerical examples dealing with the design of a narrow-band base-station antenna array for mobile communication. The flexibility and numerical efficiency of the proposed design technique are illustrated with these examples where even hundreds of antenna elements are optimized without numerical difficulties.

  • 26. Dahl, Mattias
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    Complex Approximation by Semi-Infinite Quadratic Programming2000Conference paper (Refereed)
  • 27. Dahl, Mattias
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    Complex Chebyshev Optimization Using Conventional Linear Programming: A versatile and comprehensive solution2000Report (Other academic)
    Abstract [en]

    This paper presents a new practical approach to semi-infinite complex Chebyshev approximation. By using a new technique, the general complex Chebyshev approximation problem can be solved with arbitrary base functions taking advantage of the numerical stability and efficiency of conventional linear programming software packages. Furthermore, the optimization procedure is simple to describe theoretically and straightforward to implement in computer coding. The new design technique is therefore highly accessible. The complex approximation algorithm is general and can be applied to a variety of applications such as conventional FIR filters, narrow-band as well as broad-band beamformers with any geometry, the digital Laguerre networks, and digital FIR equalizers. The new algorithm is formally introduced as the Dual Nested Complex Approximation (DNCA) linear programming algorithm. The design example in limelight is array pattern synthesis of a mobile base-station antenna array. The corresponding design formulation is general and facilitates treatment of the solution of problems with arbitrary array geometry and side-lobe weighting. The complex approximation problem is formulated as a semi-infinite linear program and solved by using a front-end applied on top of a software package for conventional finite-dimensional linear programming. The essence of the new technique, justified by the Caratheodory dimensionality theorem, is to exploit the finiteness of the related Lagrange multipliers by adapting conventional finite-dimensional linear programming to the semi-infinite linear programming problem. The proposed optimization technique is applied to several numerical examples dealing with the design of a narrow-band base-station antenna array for mobile communication. The flexibility and numerical efficiency of the proposed design technique are illustrated with these examples where even hundreds of antenna elements are optimized without numerical difficulties.

  • 28.
    Dahlberg, Anders
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Traffic Engineering in a Bluetooth Piconet2002Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    The Bluetooth technology is still in an early stage of development. Much more research can and will be done before the performance of Bluetooth reaches its peak. During the recent years, ideas to integrate Bluetooth units in larger networks have arose, with the Bluetooth unit in the role as access point to the network. This behavior opens up for new possibilities but also increases the requirements on performance. In this thesis the main topic is improvement of piconet performance. The piconet, with the Master unit as access point, is studied from a teletraffic engineering point of view. Different performance attributes and behaviors have been found and investigated. With the outcome of these investigations in mind, new and more efficient policies and algorithms are proposed for both data and voice. A policy increasing the utilization of available bandwidth in a piconet is presented. Furthermore, a proposal is presented where multiple Bluetooth units are used in an efficient manner to support voice calls. The proposed solution does also enable creation of simple teletraffic models to be used for dimensioning.

  • 29. Dahlberg, Anders
    et al.
    Zepernick, Hans-Jürgen
    Mercankosk, Guven
    Fiedler, Markus
    Multi AP concepts for SCO traffic in a Bluetooth based Radio Infrastructure Network2002Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider a radio infrastructure network (RIN), which consists of Bluetooth Access Points (APs) to provide services to ad hoc users. The RIN inherently supports both voice and data connectivity. Since Bluetooth offers the establishment of Synchronous Circuit-Oriented (SCO) traffic, the concept under study features a low-cost alternative to indoor cellular base stations. However, a single AP can serve a maximum of only three SCO channels and may not be capable of satisfying the voice traffic demands in hot spots. In order to offer more bandwidth in a location with high voice traffic, two or more APs may be placed in the same coverage area. Respective AP clusters will be denoted as Multi APs. Three Multi AP concepts for doing the SCO allocation are presented and discussed. Our findings show that employing Multi APs significantly reduces the blocking probability.

  • 30. Dahlberg, Anders
    et al.
    Zepernick, Hans-Jürgen
    Mercankosk, Guven
    Fiedler, Markus
    Multi AP Strategies for SCO Traffic in a Bluetooth based Wireless LAN2003Conference paper (Refereed)
    Abstract [en]

    We consider a Wireless Local Area Network (WLAN) consisting of Bluetooth Access Points (APs). Thus, it inherently offers both ad-hoc voice and data connectivity. As Bluetooth supports Synchronous Circuit-Oriented (SCO) traffic, the concept under study features a low-cost alternative to indoor cellular base stations. Due to the limitation of only three available SCO channels per AP, several APs can be placed in the same coverage area to satisfy voice traffic demands in hot spots. Such AP clusters will be denoted as Multi AP. Three Multi AP strategies for handling the SCO allocation are presented and discussed in terms of signaling and mean time to connect. Our findings show that employing Multi APs significantly reduces the blocking probability. A simple dimensioning rule for the number of APs is given.

  • 31. Dam, Hai Huyen
    et al.
    Nordberg, Jörgen
    Nordholm, Sven
    Non-Causal Delayless Subband Adaptive Equalizer2002Conference paper (Refereed)
    Abstract [en]

    In wireless communication, multiple versions of the transmitted signals arrive at the receiver with different attenuations and time delays. Thus, an equalizer with long filter is required at the receiver to reverse the multipath effects. In this paper, a new non-causal delayless subband equalizer structure is proposed to reduce the computational complexity of the equalizer and to improve the channel tracking capability. This structure avoids the additional delays usually associated with the subband schemes. A design method is formulated to minimize the aliasing effect of the filter bank in the subbands. The significance of employing a non-causal equalizer is also emphasized. Simulation results show that the performance of the new structure is significantly improved by using the design method. Moreover, the complexity of the new subband equalizer is a fraction of the equivalent fullband at the expense of small degradation in the performance.

  • 32. Dam, Hai Huyen
    et al.
    Nordberg, Jörgen
    Nordholm, Sven
    Zepernick, Hans-Jürgen
    Stacking Methods for Non-Causal Delayless Subband Addaptive Equalizer2002Conference paper (Refereed)
  • 33. Dam, Hai Huyen
    et al.
    Nordebo, Sven
    Svensson, Lars
    Approximation of Classical IIR Filters with Additional Specifications2000In: IEEE transactions on circuits and systems. 2, Analog and digital signal processing (Print), ISSN 1057-7130, E-ISSN 1558-125X, Vol. 47, no 12, p. 1536-1540Article in journal (Refereed)
  • 34. Dam, Hai Huyen
    et al.
    Nordebo, Sven
    Svensson, Lars
    Design of Digital Filters as the Sum of Two All--Pass Functions Using the Cepstrum Technique2003In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 51, no 3, p. 726-31Article in journal (Refereed)
  • 35. Dam, Hai Huyen
    et al.
    Nordebo, Sven
    Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
    Teo, Kok Ley
    Cantoni, Antonio
    Frequency Domain Design for Digital Laguerre Networks2000In: IEEE transactions on circuits and systems. 1, Fundamental theory and applications, ISSN 1057-7122, Vol. 47, no 4, p. 578-581Article in journal (Refereed)
  • 36. Dam, Hai Huyen
    et al.
    Teo, Kok Ley
    Liu, Yang
    Nordebo, Sven
    Optimum Pole Position for Digital Laguerre Network with Least Square Error Criterion2000In: Optimization Methods and Applications, Kluwer academic publisher , 2000, p. 321-330Chapter in book (Refereed)
  • 37. Dam, Hai Huyen
    et al.
    Teo, Kok Ley
    Nordebo, Sven
    Cantoni, Antonio
    The Dual Parameterization Approach to Optimal Least Square FIR Filter Design Subject to Maximum Error Constraints2000In: IEEE Transactions on Signal Processing, ISSN 1053-587X , Vol. 48, no 8, p. 2314-2320Article in journal (Refereed)
  • 38. Dam, Hai Huyen
    et al.
    Zepernick, Hans-Jürgen
    Nordberg, Jörgen
    Nordholm, Sven
    Application of a Global Optimization Method to the Design of Complex Spreading Sequences2002Conference paper (Refereed)
  • 39. Dam, Hai Huyen
    et al.
    Zepernick, Hans-Jürgen
    Nordberg, Jörgen
    Nordholm, Sven
    Complex Spreading Sequence Design2002Conference paper (Refereed)
    Abstract [en]

    The performance of code division multiple access system depends on the correlation of the employed spreading code. Low cross-correlation values between spreading sequences are desired to suppress multiple access interference. An auto-correlation function with with a distinct peak enables proper synchronization and suppresses intersymbol interference. However, these requirements contradict each other and a trade-off needs to be established. In this paper, a global two dimensional optimization method is proposed to minimize auto-correlation with cross-correlation being allowed to lie within a fixed region. This approach is applied to design a set of complex valued spreading sequences.

  • 40. Dam, Hai Huyen
    et al.
    Zepernick, Hans-Jürgen
    Nordberg, Jörgen
    Nordholm, Sven
    Design of Complex Spreading Sequences2002Conference paper (Refereed)
  • 41.
    Erman, David
    Blekinge Institute of Technology, Department of Telecommunications and Signal Processing.
    Design and Implementation of an Acoustical Transmission Protocol2002Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    The RoboCup Sony Legged Robot League is an initiative to promote robotics technologies and artificial intelligence in the form of a soccer competition between four-legged robots. The Blekinge Institute of Technology, Royal Institute of Technology, the Universities of ¨ Orebro and Ume°a, competing in the RoboCup domain as Team Sweden , have been participants in the league for three years. To improve the chances of victory in the league, a way to communicate important data between robots is desired. This thesis explores methods for implementing this communication using only the built-in hardware of the robots, i.e. one speaker and two microphones.

  • 42. Fai, Cedric Yiu Ka
    et al.
    Grbic, Nedelko
    Kok-Lay, Teo
    Nordholm, Sven
    A New Design Method for Broadband Microphone Arrays for Speech Input in Automobiles2002In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 9, no 7, p. 222-224Article in journal (Refereed)
    Abstract [en]

    A new design method for broadband microphone arrays is presented. Using sequences of calibration signals, the method is able to design finite-impulse response (FIR) filters with specific performance. The method can control and adjust the speech distortion, noise suppression, and echo cancellation directly. It turns out that a significantly shorter filter length can be applied to achieve better overall performance than the least-squares method or the signal-to-noise plus interference method.

  • 43. Fiedler, Markus
    Direct Evaluation of Required Capacity for ATM Multiplex1998Other (Other academic)
    Abstract [en]

    Required capacity may be used in Connection Admission Control, Network Resource Management or for purposes of planning and dimensioning. From the well-known loss probability formula for the bufferless fluid ow model, an implicit formula for the required capacity for a given QoS per connection may be derived which turns into a closed formula when it is evaluated in a special way. This formula, whose complexity is comparable to that of the original loss probability formula, allows for a quick and exact evaluation of required capacity. Differences to other possibilities of required capacity evaluation are shown, and potential problems affecting the use of the formula are discussed. Finally, the suitability of the equivalent bandwidth in COST-242 for required capacity evaluations is demonstrated.

  • 44. Fiedler, Markus
    Modeling and Analysis of Wireless Network Segments with aid of Teletraffic Fluid Flow Models2000Report (Other academic)
    Abstract [en]

    The fluid flow model is used to model variable server and link rates, as they appear in mobile channels due to fading, bit error recovery and failed channel reservations. Assuming a Gilbert-Elliott model for the channel, the influence of transmission quality on network Quality of Service (QoS) might be studied. Thus, the fluid flow model assumes the role of a model that might be used for dimensioning and performance evaluation both at the edge and inside a network. We present a user-friendly, contemporary, flexible, fast and numerically stabilized computing environment for the fluid flow model with a well-known user interface that is able to handle multiple users and that might be used as well for batch processing. We discuss two case studies that emphasize the crucial impact of the relationship between server and source dynamics on QoS.

  • 45. Fiedler, Markus
    et al.
    Addie, Ron G.
    Verification and application of a second-order scale symmetry for queueing systems1999Conference paper (Refereed)
    Abstract [en]

    In this paper a simple second order scale symmetry is descibed. Because of the application of the central limit theorem to network traffic, which applies whenever the variance of the traffic from individual sources is finite, this scale symmetry is valid asymptotically for a large number of sources independently of the buffer size, the queueing performance parameter under consideration and the source model. Numerical results for on-/off sources show that it gives clear guidance for how system resources must grow in order to cope with increasing traffic, while maintaining or slightly improving queueing performance. Thus, it may be used for dimensioning purposes beyond the reach of sophisticated algorithms. Parallels to equivalent bandwidth approaches are drawn.

  • 46. Fiedler, Markus
    et al.
    Angelin, Lars
    Mobile services: students as need-finders2002Conference paper (Refereed)
    Abstract [en]

    This paper presents a way of identifying new and useful mobile services by letting students act as need-finders and developers of services based on their own needs and ideas. It describes the background and outcomes of a course in mobile services given at Blekinge Institute of Technology (BTH) in spring 2002.

  • 47. Fiedler, Markus
    et al.
    Arvidsson, Åke
    A Resource Allocation Law to Satisfy QoS Demands on ATM Burst and Connection Level1999Other (Other academic)
    Abstract [en]

    In this paper, we show the validity of a quite simple resource allocation law, which is not restricted to one time scale. Besides the fact that this law describes the basic behaviour of resource allocation for sources with variable bit rates, it offers savings of time and memory in practice when systems are to be dimensioned and routing has to be performed, and particularly in dynamic resource allocation with real-time requirements. The law is given as a function of traffc demand and consists of a constant, a linear and a power term. Its coeffcients are in influenced by traffic and system characteristics as well as by QoS requirements and may be determined by a Genetic Algorithm. Many examples show the universal character of this law for sources with variable bit rates.

  • 48. Fiedler, Markus
    et al.
    Arvidsson, Åke
    Required capacity for ATM Virtual Paths for QoS on cell and connection level1999Conference paper (Refereed)
    Abstract [en]

    We show approximation formulae for required capacities (bit rates) of ATM Virtual Paths that cover allocation on cell and connection level at the same time. Such formulae are valuable for dimensioning and routing purposes, as they allow for fast and precise calculations of required capacities and show the kind of dependency on the traffic demand for given traffic characteristics and Qulity of Service requirements. We discuss how to determine the coefficients of the approximation and its precision for connections with on-/off characteristics (voice, data). Finally, we show the gain that might be obtained if statistical multiplexing of variable bit rate connections is taken into account at the cell level.

  • 49. Fiedler, Markus
    et al.
    Carlsson, Patrik
    Nilsson, Arne A.
    Voice and Multi-fractal Data in the Internet2001Conference paper (Refereed)
    Abstract [en]

    In the Internet era there is a need to understand how traditional Public Switched Telephone Network (PSTN) services and the new Internet services can coexist. The best-effort based IP network will have to maintain the level of service that customers from the PSTN world expect. This study contributes to the traffic engineering of such a system by presenting an analytical model for integrating Voice over IP (VoIP) traffic with multi-fractal data traffic. This model is based on the stochastic fluid flow model. Effects on delay and loss performance of adding VoIP traffic to a data link as well as capacity requirements to maintain a certain quality of service are discussed

  • 50. Fiedler, Markus
    et al.
    Ekelin, Annelie
    Dittrich, Yvonne
    Eriksén, Sara
    E-government as co-construction: Networks, accountability, and working relations of technology production and use2003Conference paper (Refereed)
    Abstract [en]

    The project within which this paper was co-authored focuses on the domain of e-government and is a deliberate attempt by the involved partners to cultivate and expand local and regional spaces for situated innovation, design and development of public services and ICT use in the public sector. Our starting point is e-government understood as co-construction. The project is currently being funded by the Innovative Actions within ERDF, the European Regional Development unding. The partners of the e-overnment arena are public service providers, ICT providers and researchers from a number of different disciplines. In this paper, we focus on communication networks and accountability. Are communication networks enablers or disablers for e-government services, and how can they be held accountable to their users? To what extent might we need to help each other unpack ‘black boxes’ and exchange them for ‘glass boxes’ in communicating with users and across disciplinary boundaries? Using metaphors and models from telecommunications, software engineering, informatics, business administration and human work science, and inspired by the Scandinavian tradition of Participatory Design, we attempt to establish a common basis to explore the evolving technologies and practices in e-government.

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