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  • 1.
    Agevik, Niklas
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Fransson, Henrik
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Grunell, Henrik
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Jakiel, Patrick
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Lundin, Henrik
    KTH, Superseded Departments, Signals, Sensors and Systems.
    On Loudspeaker Linearization Using Pre-Distortion2004In: European DSP Education & Research Symposium (EDERS), 2004Conference paper (Refereed)
    Abstract [en]

    In this paper we present a system for linearizing the combined output of a stereo amplifier and loudspeaker through pre-distortion. Removal of room cancellation effects is also discussed. The system uses white noise to estimate an FIR model with the Recursive Least Squares algorithm and experiments show that this can significantly improve the linearity of the sound system. We show that the system can be extended with a nonlinear model and that this indeed can be implemented on a TexasInstruments TMS320C6701 DSP with excellent performance.

  • 2.
    Ahlin, Lars
    et al.
    Swedish Defence Research Agency (FOI).
    Englund, Eva
    FOI.
    Jönsson, Christian
    FOI.
    Söderquist, Ingrid
    FOI.
    Zander, Jens
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Maguire Jr., Gerald Q.
    KTH, Superseded Departments, Teleinformatics.
    Automous Tactical Communications Possibilities and Problems1997In: MILCOM 97 Proceedings, 1997, p. 393-397Conference paper (Refereed)
    Abstract [en]

    In the battlefield of the future, more and more information will be available for making decisions on a tactical level, provided that this information can be dispersed rapidly and accurately. As a consequence, advanced tactical decision support that now is limited to advanced platforms (e.g. combat aircrafts) will become available at a much lower level, ranging from different kinds of vehicles, down to the individual soldier by means of ultra-light weight ``wearable'' equipment.

    Establishing reliable wireless communications in such a large group of users with unprecidented bandwidth demands and requirements on survivability constitutes a considerable enginerring challenge. In the paper we will, after a short review of some existing approaches, investigate the specific engineering challenges and the fundamental limitations of such low level, autonomous communication systems. Further we give an example of a system architecture, harmonized with a proposed structure for third generation commercial wireless systems (e.g. UMTS). Our conclusions show that mainly distributed computing complexity, device power consumption and available bandwidth constitute the fundamental problems.

  • 3.
    Ahlin, Lars
    et al.
    Swedish Defence Research Agency (FOI).
    Zander, Jens
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Automous tactical communication: problems & possibilities1996Conference paper (Refereed)
    Abstract [en]

    On the battlefield of the future, more and more information will be available for making decisions on a tactical level, provided that this information can be dispersed rapidly and accurately. Sophisticated electronic equipment for communication, information processing and for collection of sensor data are becoming light-weight, small and inexpensive. As a consequence, advanced tactical decision support that now is limited to advanced platforms (e.g. combat aircrafts) will become available at a much lower level, maybe down to the individual soldier. In such a scenario, the number of communicating entities is one or several orders of magnitude larger than in todays tactical systems. Establishing reliable wireless communications in such a large group constitutes a considerable engineering challenge. In this paper we investigate the specific engineering challenges and the fundamental limitations of such low level, autonomous communication systems. Our conclusions are that mainly distributed computing complexity, device power consumption and available bandwidth constitute the fundamental problems.

  • 4. Ahnström, Ulrika
    et al.
    Falk, Johan
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wikström, Maria
    Detection and direction-finding of spread spectrum signals using correlation and narrowband interference rejection2003In: Nordic Matlab Conference 2003, 2003Conference paper (Refereed)
    Abstract [en]

    An algorithm for correlation-based detection of direct sequence spread spectrum signals with direction finding, including direction-filtering and narrow-band interference rejection, is implemented and evaluated in MATLAB. An analog noise-free signal is generated and sampled by a test-bed system. Numerical simulations are run based on data corrupted by mutually uncorrelated white Gaussian noise sequences, and also with recorded noise from two spatially separated HF radio receivers. The simulations and measurements show promising results for detection and direction-finding of covert wideband signals in low SNR and in presence of narrowband interferers. Direction filtering is shown to improve the results.

  • 5.
    Aktas, Bagsen
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Bria, Aurelian
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Evaluation of User Perceived Performance in Sparce Infrastructure Wireless Systems2004Conference paper (Refereed)
    Abstract [en]

    This work tries to evaluate the user perceived performance in a wireless system based on sparse infrastructure (islands of coverage).We investigate a mobile user in a Manhattan environment and the considered service is web browsing. Data caching in the use terminal is employed in order to hide the discontinuities of coverage. We show that for this particular application, the user's behavior of revisiting pages previously accessed makes caching a way to increase the user perceived coverage. Our results show that at low levels of effective area coverage caching brings a large improvement, while the gain is not significant at high levels. If the sparse coverage network is overlaid over a cellular system the obtained results show potential for significant cost savings.

  • 6.
    Al-Askary, Omar
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Iterative decoding of product codes2003Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    Iterative decoding of block codes is a rather old subjectthat regained much interest recently. The main idea behinditerative decoding is to break up the decoding problem into asequence of stages, iterations, such that each stage utilizesthe output from the previous stages to formulate its ownresult. In order for the iterative decoding algorithms to bepractically feasible, the complexity in each stage, in terms ofnumber of operations and hardware complexity, should be muchless than that for the original non-iterative decoding problem.At the same time, the performance should approach the optimum,maximum likelihood decoding performance in terms of bit errorrate.

    In this thesis, we study the problem of iterative decodingof product codes. We propose an iterative decoding algorithmthat best suits product codes but can be applied to other blockcodes of similar construction. The algorithm approaches maximumlikelihood performance. We also present another algorithm whichis suboptimal and can be viewed as a practical implementationof the rst algorithm on product codes. The performance of thesuboptimal algorithm is investigated both analytically and bycomputer simulations. The complexity is also investigated andcompared to the complexity of GMD and Viterbi decoding ofproduct codes.

  • 7.
    Al-Askary, Omar
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Papr reduction of coded OFDM signals based on iterative codeword construction2004In: ISCCSP: 2004 FIRST INTERNATIONAL SYMPOSIUM ON CONTROL, COMMUNICATIONS AND SIGNAL PROCESSING, NEW YORK: IEEE , 2004, p. 763-766Conference paper (Refereed)
    Abstract [en]

    Orthogonal Frequency Division Multiplexing (OFDM) allows transmission of data with high data rates over broad-band radio channels without the need for powerful equalization. However, OFDM is sensitive to non-linearities in the system due to the high Peak to Average Power Ratio (PAPR) in the transmitted signal. In this paper, we propose a simple method for reducing the PAPR in the OFDM signals using the well known BCH codes. The method relies on an iterative procedure to select a codeword that has a low PAPR from a translation of the code to another partition in a larger BCH code. The information about the chosen partition is loaded in the redundancy of the sent codeword and, therefore, no subcarriers are reserved for transmitting this information. The cost payed for this PAPR reduction is reduced error correction capability. Using this method, a reduction of the PAPR of up to 6 dB can be achieved with moderate complexity.

  • 8. Alizadeh Khameneh, Mohammad Amin
    et al.
    Ronnow, D.
    Händel, Peter
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Isaksson, M.
    A new Block-Structure Modeling Technique for RF Power Amplifiers in a 2x2 MIMO System2017In: 2017 13TH INTERNATIONAL CONFERENCE ON ADVANCED TECHNOLOGIES, SYSTEMS AND SERVICES IN TELECOMMUNICATIONS (TELSIKS) / [ed] Milovanovic, BD Doncov, NS Stankovic, ZZ Dimitrijevic, TZ, IEEE , 2017, p. 224-227Conference paper (Refereed)
    Abstract [en]

    A new block-structure behavioral model is proposed for radio frequency power amplifiers in a 2x2 multiple-input multiple-output system including input cross-talk. The proposed model forms kernels of blocks of different nonlinear order that correspond to the significant frequency response of measured frequency domain Volterra kernels. The model can therefore well describe the input-output relationships of the nonlinear dynamic behavior of PAs. The proposed model outperforms conventional models in terms of model errors.

  • 9.
    Altafini, Claudio
    et al.
    SISSA-ISAS International School for Advanced Studies.
    Speranzon, Alberto
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Johansson, Karl Henrik
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Hybrid control of a truck and trailer vehicle2002In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 2289, p. 21-34Article in journal (Other academic)
    Abstract [en]

    A hybrid control scheme is proposed for the stabilization of backward driving along simple paths for a miniature vehicle composed of a truck and a two-axle trailer. When reversing, the truck and trailer can be modelled as an unstable nonlinear system with state and input saturations. Due to these constraints the system is impossible to globally stabilize with standard smooth control techniques, since some initial states necessarily lead to that the so called jack-knife locks between the truck and the trailer. The proposed hybrid control method, which combines backward and forward motions, provide a global attractor to the desired reference trajectory. The scheme has been implemented and successfully evaluated on a radio-controlled vehicle. Results from experimental trials are reported.

  • 10.
    Altafini, Claudio
    et al.
    KTH, Superseded Departments, Mathematics.
    Speranzon, Alberto
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Wahlberg, Bo
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A feedback control scheme for reversing a truck and trailer vehicle2001In: IEEE transactions on robotics and automation, ISSN 1042-296X, Vol. 17, no 6, p. 915-922Article in journal (Refereed)
    Abstract [en]

    A control scheme is proposed for stabilization of backward driving along simple paths for a miniaturized vehicle composed of a truck and a two-axle trailer. The paths chosen are straight lines and arcs of circles. When reversing, the truck and trailer under examination can be modeled as an unstable nonlinear system with state and input saturations. The simplified goal of stabilizing along a trajectory (instead of a point) allows us to consider a system with controllable linearization. Still, the combination of instability and saturations makes the task impossible with a single controller. In fact, the system cannot be driven backward from all initial states because of the jack-knife effects between the parts of the multibody vehicle; it is sometimes necessary to drive forward to enter into a specific region of attraction. This leads to the use of hybrid controllers. The scheme has been implemented and successfully used to reverse the radio-controlled vehicle.

  • 11.
    Amelin, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    The value of transmission capability between countries and regions2000Licentiate thesis, monograph (Other scientific)
  • 12.
    Anderlind, Erik
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Resource allocation in multi-service wireless access networks1997Doctoral thesis, monograph (Other scientific)
  • 13.
    Anderlind, Erik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Mandayam, Narayan B.
    Wireless Information Network Laboratory (WINLAB), Rutgers University.
    Yates, Roy D.
    Wireless Information Network Laboratory (WINLAB), Rutgers University.
    SIR Estimation for Narrow-band M-PSK Modulated Radio Links1995Conference paper (Refereed)
    Abstract [en]

    A large number of radio resource management algorithms  rely on accurate measurements of the signal to interference ratio (SIR). We propose a simple, fast SIR estimator for narrow  band M-PSK modulated signals (M > 2). The estimator does  not require any overhead sequences of known symbols and it is  shown to be asymptotically unbiased. It can produce an accurate estimate for each received signal burst. Numerical results  are presented for a Rayleigh fading channel with one and several  interferers.

  • 14.
    Anderlind, Erik
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Zander, Jens
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A Traffic Model for Non-Real-Time Data Users in Wireless Radio Networks1997In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 1, no 2, p. 37-39Article in journal (Refereed)
    Abstract [en]

    Based on an analysis of Internet protocols for data communication, we propose a simple model for future data traffic in wireless radio networks. Model parameters are selected so as to resemble traffic from the Worldwide Web (WWW) access and from distributed file systems. By changing a single parameter, the model can be switched between resembling up- or down-link traffic. The model is intended for design and performance analysis of radio resource allocation algorithms in future wireless systems.

  • 15.
    Andersin, Michael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Power control and Admission Control in Cellular Radio Systems1996Doctoral thesis, monograph (Other academic)
  • 16.
    Andersin, Michael
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Frodigh, Magnus
    Ericsson Radio Systems.
    Sunell, Kai-Erik
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Distributed Radio Resource Allocation in Highway Microcellular Systems1996In: Wireless information networks: Architecture, resource management, and mobile data, 1996, p. 117-132Conference paper (Refereed)
  • 17.
    Andersin, Michael
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Mandayam, Narayan B.
    Wireless Information Network Laboratory (WINLAB), Rutgers University.
    Yates, Roy D.
    Wireless Information Network Laboratory (WINLAB), Rutgers University.
    Subspace based estimation of the signal to interference ratio for TDMA cellular systems1998In: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196, Vol. 4, no 4, p. 241-247Article in journal (Refereed)
    Abstract [en]

    The Signal-to-Interference Ratio (SIR) has been highlighted in the literature to be a most efficient criterion for several methods aiming at reducing the effects of cochannel interference, e.g., diversity reception, dynamic channel allocation and power control. In this paper we address the problem of how to obtain fast and accurate measurements of this parameter in a practical context. We develop a general SIR estimation technique for narrow-band cellular systems that is based on a signal subspace approach using the sample covariance matrix of the received signal. Simulation results using the frame structure in the GSM system show that the SIR can be estimated to within an error of 0.3 dB after only 200 ms, or within an error of 0.1 dB after only 0.6 seconds.

  • 18.
    Andersin, Michael
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Rosberg, Zvi
    IBM, Haifa Research Laboratory.
    Time Variant Power Control in Cellular Networks1996In: Proceedings of the 1996 7th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC'96, IEEE , 1996, p. 193-197Conference paper (Refereed)
    Abstract [en]

    We study the transmission power control in a cellular network where users' mobility results in a time varying gain matrix. A framework for evaluating the channel quality is specified, and an asymptotic representation of the link gain evolution in time is obtained. Then, a time variant distributed constrained power control (TVPC) which copes with user mobility is derived. The algorithm is compared to a classical distributed constrained power control (DCPC), as well as to a constant-received power control and constant-transmitted power. The comparison reveals that the classical DCPC exhibits an outage probability close to one, unless some counter-measures are taken. The TVPC algorithm however, copes well with users' mobility and provides a close to optimal scale up factor for the signal to interference ratio (SIR) target.

  • 19.
    Andersin, Michael
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Rosberg, Zvi
    IBM, Haifa Research Laboratory.
    Transmission power cost of mobility in cellular networks1996Report (Other academic)
    Abstract [en]

    We study the transmission power control in a cellular network where users mobility results  in a time varying gain matrix. A framework for evaluating the channel quality is specified,  and an asymptotic representation of the link gain evolution in time is obtained. Then, a  variant of a standard Distributed Constrained Power Control (DCPC) which copes with  user mobility is derived. These two power controls, as well as constant­received power and  constant­transmitted power controls are compared with respect to their outage probabilities  in a Manhattan­like microcellular system. The comparison reveals that the classical DCPC  algorithm has an outage probability close to one, unless some counter­measures are taken.  The time variant algorithm however, copes well with users mobility and provides a close to  an optimal scale up factor for the Signal to Interference Ratio (SIR) target. Furthermore, the  time variant algorithm provides a substantial improvement in spectrum utilization compared  to the other algorithms above.

  • 20.
    Andersin, Michael
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Rosberg, Zvi
    IBM, Haifa Research Laboratory.
    Zander, Jens
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Distributed Discrete Power Control in Cellular PCS1998In: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 6, no 3, p. 211-213Article in journal (Refereed)
    Abstract [en]

    Transmitter power control has proven to be an efficient method to control cochannel interference in cellular PCS, and to increase bandwidth utilization. Power control can also improve channel quality, lower the power consumption, and facilitate network management functions such as mobile removals, hand-off and admission control. Most of the previous studies have assumed that the transmitter power level is controlled in a continuous domain, whereas in digitally power controlled systems, power levels are discrete. In this paper we study the transmitter power control problem using only a finite set of discrete power levels. The optimal discrete power vector is characterized, and a Distributed Discrete Power Control (DDPC) algorithm which converges to it, is presented. The impact of the power level grid on the outage probability is also investigated. A microcellular case study is used to evaluate the outage probabilities of the algorithms.<

  • 21.
    Andersin, Michael
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Rosberg, Zvi
    IBM, Haifa Research Laboratory.
    Zander, Jens
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Gradual Removals in Cellular PCS with Constrained Power Control and Noise1996In: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196, Vol. 2, no 1, p. 27-43Article in journal (Refereed)
    Abstract [en]

    In this paper we study the mobile removal problem in a cellular PCS network where  transmitter powers are constrained and controlled by a Distributed Constrained  Power Control (DCPC) algorithm. Receivers are subject to non­negligible noise,  and the DCPC attempts to bring each receiver's CIR above a given target. To  evaluate feasibility and computational complexity, we assume a paradigm where  radio bandwidth is scarce and inter­base station connection is fast.  We show that finding the optimal removal set is an NP-Complete problem,  giving rise for heuristic algorithms. We study and compare among three classes  of transmitter removal algorithms. Two classes consist of algorithms which are  invoked only when reaching a stable power vector under DCPC. The third class  consist of algorithms which combine transmitter removals with power control.  These are One-by-one Removals, Multiple Removals, and Power Control with Removals Combined. In the class of power control with removals combined, we also  consider a distributed algorithm which uses the same local information as DCPC  does.

    All removal algorithms are compared with respect to their outage probabilities  and their time to converge to a stable state. Comparisons are made in a hexagonal macro-cellular system, and in two metropolitan micro-cellular systems. The  Power Control with Removals Combined algorithm emerges as practically the best  approach with respect to both criteria.

  • 22.
    Andersin, Michael
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Rosberg, Zvi
    IBM, Haifa Research Laboratory.
    Zander, Jens
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Soft Admission in Cellular PCS with Constrained Power Control and Noise1995In: Proc 5th WINLAB Workshop on Third Generation Wireless Information Networks, 1995, p. 287-320Conference paper (Refereed)
    Abstract [en]

    We study the mobile admission control problem in a cellular PCS network where trans- mitter powers are constrained and controlled by a Distributed Constrained Power Control (DCPC) algorithm. Receivers are subject to non-negligible noise, and the DCPC attempts to bring each receiver's CIR (Carrier to Interference Ratio) above a given quality target. Two classes of distributed admission controls are considered. One is a Non-Interactive Admission Control (N-IAC), where an admission decision is instantaneously made based on the system state. The other is an Interactive Admission Control (IAC), under which the new mobile is permitted to interact with one or more potential channels before a decision is made. The algorithms are evaluated with respect to their execution time, and their decision errors. Two types of errors are examined. Type I error, where a new mobile is erroneously accepted and results an outage; and type II error, where a new mobile is erroneously rejected and results in blocking. The algorithms in the N-IAC class accept a new mobile, if and only if the uplink and the downlink interferences are below certain corresponding thresholds. These algorithms are subject to errors of type I and type II. In the IAC class, we derive a Soft and Safe (SAS) admission algorithm, which is type I and type II error free, and protects the CIRs of all active links at any moment of time. A Fast-SAS version which is only type I error free, is proposed for practical implementation, and evaluated in several case studies.

  • 23.
    Andersin, Michael
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Zander, Jens
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Roseberg, Zvi
    Soft and safe admission control in cellular networks1997In: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 5, no 2, p. 255-265Article in journal (Refereed)
    Abstract [en]

    We study the mobile admission control problem in a cellular PCS network where transmitter powers are constrained and controlled by a distributed constrained power control (DCPC) algorithm. Receivers are subject to nonnegligible noise, and the DCPC attempts to bring each receiver's CIR (carrier-to-interference ratio) above a given quality target. Two classes of distributed admission control are considered. One is a noninteractive admission control (N-IAC), where an admission decision is instantaneously made based on the system state. The other is an interactive admission control (IAC), under which the new mobile is permitted to interact with one or more potential channels before a decision is made. The algorithms are evaluated with respect to their execution time and their decision errors. Two types of errors are examined: type I error, where a new mobile is erroneously accepted and results in outage; and type II error, where a new mobile is erroneously rejected and results in blocking. The algorithms in the N-IAC class accept a new mobile if and only if the uplink and the downlink interferences are below certain corresponding thresholds. These algorithms are subject to errors of type I and type II. In the IAC class, we derive a soft and safe (SAS) admission algorithm, which is type I and type II error free, and protects the CIR's of all active links at any moment of time. A fast-SAS version, which is only type I error-free, is proposed for practical implementation, and is evaluated in several case studies.

  • 24.
    Andersson, Gunnar
    KTH, Superseded Departments, Signals, Sensors and Systems.
    LPI performance of an adaptive frequency-hopping system in an HF interference environment1996In: Proceedings of the 1996 4th International Symposium on Spread Spectrum Techniques & Applications, ISSSTA'96: Mainz, Ger; 22 September 1996 through 25 September 1996, IEEE , 1996, p. 903-907Conference paper (Refereed)
    Abstract [en]

    Frequency-hopping is considered to be an effective method for combating active jamming in military radio systems. To further improve the performance, so-called adaptive frequency-hopping (AFH), which uses an adaptively selected pool of the “best” hopping-frequencies for the communication, has been proposed. In this paper, we examine the low probability of intercept (LPI) performance of such an AFH system on an interference-limited HF channel. The LPI property is evaluated with respect to two different hostile detectors; the radiometer and a sub-optimum matched filter detector. It is found that the matched filter detector is a much more serious threat against the AFH system, due to its ability to suppress the strong interfering HF signals in the detection process. Furthermore, the LPI performance proves to be very dependent on whether the interceptor can estimate the pool of hopping-frequencies used by the AFH system or not. If the interceptor cannot perform such an estimation, the AFH signal has a high chance of remaining undetected in the dense HF interference environment.

  • 25.
    Andersson, Helene
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Microfluidic devices for biotechnology and organic chemical applications2001Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Imagine if you could combine the power and capabilities ofan entire laboratory in the palm of your hand. Advances inmicrofluidic chip technology promise to integrate andminiaturize multiple lab processes into a single palm-sizeddevice. The advantages of these lab-on-a-chip devices,sometimes also referred to as micro total analysis systems(µTAS), compared with conventional bench-scale systems arenumerous and wide ranging and include: less reagentconsumption, low manufacturing costs, increased performance,faster analysis, high sample throughput, integration andautomation possibilities, and disposability. However,microfluidic devices also present challenges such as theinterfacing to the macro world and detection limits.

    In this thesis the focus has been to develop novel discretemicrofluidic components for biotechnology and organic chemicalapplications with the goal to integrate them to formlab-on-chips. A flow-through filter-chamber device has beendesigned, manufactured and evaluated for chemical analysis onbeads. Passive liquid handling has been integrated on the chipin the form of hydrophobic valves at the inlet channels. Anarray format has also been developed to allow parallel analysisof multiple samples. The filter-chamber functions well forsingle nucleotide analysis using pyrosequencing. Initialevaluations on catalyst screening in the filter-chamber devicehas been performed.

    The suitability of valve-less micropumps for biochemicalapplications is presented. Fluids encountered in variousbiochemical methods, including living cells, that areproblematic for other micropumps have been pumped with goodperformance. This thesis also introduces expandablemicrospheres as a novel component in microfluidics includingapplications such as one-shot valves, micropositioning andsurface enlargement.

    A novel technique for bead immobilization in microfluidicdevices based on surface chemistry is presented in this thesis.Beads for both biochemical assays and organic chemistry havebeen self-sorted and self-assembled in line patterns as narrowas 5 µm on both structured and unstructured substrates.This method will greatly facilitate the generation of screeningplatforms, for example.

    To develop a microfluidic device for catalysis-on-chip,ligands for asymmetric catalysis have successfully beenimmobilized in silicon channels by consecutive microcontactprinting, which is a novel technique presented in thisthesis.

    Keywords:microfluidics, beads, microspheres, silicon,filter-chamber, flow-through, bead trapping, DRIE, passivevalves, fluorocarbon, microfluidic array, adhesive bonding,valve-less micropump, microcontact printing, PDMS,self-assembly, self-sorting, DNA, SNP, pyrosequencing,allele-specific extension, expandable microspheres, catalysis,chiral ligand, monolayer, miniaturization, lab-on-a-chip,µTAS.

  • 26.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    Griss, P.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Expandable microspheres - surface immobilization techniques2002In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 84, no 2-3, p. 290-295Article in journal (Refereed)
    Abstract [en]

    In this study, a novel component for microfluidics is introduced. Expandable microspheres have been studied for their application in microfluidics. Two methods for selective immobilization of expandable microspheres without the use of mechanical barriers on silicon, including patterning by photolithography and self-assembly based on surface chemistry have been shown. After the immobilization step the microspheres were expanded thermally. The expansion is irreversible and the volume of the microspheres increases more than 60 times. Patterns of microspheres with features as small as 15 pm have successfully been generated by photolithography. By using self-assembly the microspheres can conveniently be immobilized in monolayers. Future applications of the expandable microspheres can be as fluidic components, such as one-shot valves or micropumps, positioning other microcomponents or to enlarge the surface area.

  • 27.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    Jonsson, C.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Consecutive microcontact printing - ligands for asymmetric catalysis in silicon channels2001In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 79, no 1, p. 78-84Article in journal (Refereed)
    Abstract [en]

    Consecutive microcontact printing ( mu CP) has been developed to enable multiple functionalization of silicon surfaces, such as the immobilization of chiral ligands. The technique involves two subsequent printing steps using unstructured poly(methylsiloxane) stamps. The pattern is already defined on the substrate, consisting of etched channels. Hence, no precise alignment is needed between the two printing steps. A carboxylic acid group containing reagent was initially printed onto the silicon oxide surface and transformed to an anhydride. hi the second printing step an ester bond was formed with the hydroxy-functionalized ligand. The formed molecular layers were evaluated by contact angle measurements, scanning electron microscopy (SEM) and electron spectroscopy for chemical analysis (ESCA), indicating that the consecutive mu CP was successful. Initially, printing was performed on planar silicon surfaces but to realize a flow-through microfluidic device for high throughput screening a mu CP technique was developed for etched channels. To verify the technique, hydrophobic valves consisting of octadecyltrichlorosilane were formed using mu CP in deep reactive ion etched channels (50 mum wide and 50 mum deep). The printed hydrophobic patches were visualized by SEM and functioned well. Finally, the consecutive mu CP technique was applied to immobilize the ligand in the channels. The channels were then sealed with a low-temperature bonding technique using an adhesive PDMS film, which does not destroy the printed ligand. In this study mu CP is used in a novel manner. It enables a convenient method for performing complex surface modification of etched structures, which is a frequently appearing problem in biochemical microfluidic systems.

  • 28.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    Jonsson, C.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Patterned self-assembled beads in silicon channels2001In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 22, no 18, p. 3876-3882Article in journal (Refereed)
    Abstract [en]

    A novel technique enabling selective bead trapping in microfluidic devices without the use of physical barriers is presented in this paper. It is a fast, convenient and simple method, involving microcontact printing and self-assembly, that can be applied to silicon, quartz or plastic substrates. In the first step, channels are etched in the substrate. The surface chemistry of the internal walls of the channels is then modified by microcontact printing. The chip is submerged in a bead slurry where beads self-assemble based on surface chemistry and immobilize on the internal walls of the channels. Silicon channels (100 mum wide and 50 mum deep) have been covered with monolayers of streptavidin-, amino- and hydroxy-functionalized microspheres and resulted in good surface coverage of beads on the channel walls. A high-resolution pattern of lines of self-assembled streptavidin beads, as narrow as 5 mum, has also been generated on the bottom of a 500 mum wide and 50 mum deep channel. Flow tests were performed in sealed channels with the different immobilized beads to confirm that the immobilized beads could withstand the forces generated by water flowing in the channels. The presented results indicate that single beads can be precisely positioned within microfluidic devices based on self-assembly which is useful as screening and analysis tools within the field of biochemistry and organic chemistry.

  • 29.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    Jonsson, C.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Self-assembled and self-sorted array of chemically active beads for analytical and biochemical screening2002In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 56, no 2, p. 301-308Article in journal (Refereed)
    Abstract [en]

    A technique for generating a general screening platform consisting of dots of immobilized beads on silicon has been developed via self-sorting and -assembly of different kinds of beads. The dots are defined by a teflon-like film, which due to its hydrophobic characteristics also prevents cross-contamination of liquid from different dots. To enable functionalization of individual dots with different target molecules simultaneously a new way of microcontact printing has been explored where different target solutions are printed in parallel using one stamp. In order to show that this platform can be designed for both biochemical assays and organic chemistry, streptavidin-, amino- and hydroxy-functionalized beads have been self-sorted and -assembled both on separate and common platforms. The self-sorting and -arrangement are based on surface chemistry only, which has not previously been reported. Beads of different sizes and material have successfully been immobilized in line patterns as narrow as 5 mum. Besides silicon, quartz and polyethylene have also been used as substrates.

  • 30.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    van den Berg, A.
    Microtechnologies and nanotechnologies for single-cell analysis2004In: Current Opinion in Biotechnology, ISSN 0958-1669, E-ISSN 1879-0429, Vol. 15, no 1, p. 44-49Article, review/survey (Refereed)
    Abstract [en]

    Many efforts are currently underway to try and mimic the properties of single cells with the aim of designing chips that are as efficient as cells. However, cells are nature's nanotechnology engineering at the scale of atoms and molecules, and it might be better to envision a microchip that utilizes a single cell as an experimentation platform. A novel, so-called laboratory-in-a-cell concept has been described, where advantage is taken of micro-and nanotechnological tools to enable precise control of the biochemical cellular environment; these tools also offer the possibility to analyse the composition of single cells. Methods for single-cell handling and analysis are being developed and will be required for this concept to progress further.

  • 31.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    van der Wijngaart, Wouter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Enoksson, P.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Micromachined flow-through filter-chamber for chemical reactions on beads2000In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 67, no 1-2, p. 203-208Article in journal (Refereed)
    Abstract [en]

    A new flow-through micromachined device for chemical reactions on beads has been designed, manufactured, and characterized. The device has an uncomplicated planar design and microfabrication process. Both nonmagnetic and magnetic beads can be collected in the reaction chamber without the use of external magnets. The sample flow-through volume of liquid or gas is adjustable and unlimited. The device is sealed with Pyrex to allow real time optical detection of the chemical reactions. At a constant pressure of 3 kPa at the inlet the flow rate for water is about 3.5 mu l/min without beads in the filter chamber, for all the designs. The smallest reaction chamber has a volume of 0.5 nl and can collect approximately 50 beads with a diameter of 5.50 mu m. At a constant pressure of 3 kPa at the inlet, the flow rate for water is about 2.0 mu l/min when the reaction chamber is completely packed with beads. Hence, the flow rate decreases with about 40% when the reaction chamber is packed with beads. The flow-through microfluidic device is not sensitive to gas bubbles, and clogging of the filter is rare and reversible. The beads are easy to remove from the reaction chamber making the micromachined flow-through device reusable. A new and simple technique for fluid interconnection is developed.

  • 32.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    van der Wijngaart, Wouter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Griss, P.
    Niklaus, Frank
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Hydrophobic valves of plasma deposited octafluorocyclobutane in DRIE channels2001In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 75, no 1-2, p. 136-141Article in journal (Refereed)
    Abstract [en]

    The suitability of using octafluorocyclobutane (C4F8) patches as hydrophobic valves in microfluidic biochemical applications has been shown. A technique has been developed to generate lithographically defined C4F8 hydrophobic patches in deep reactive ion-etched silicon channels. Some of the advantages of this process are that no specific cleaning of the substrate is required, C4F8 is deposited on the sidewalls and the bottom of the channels, a standard photoresist mask can be used to define the patches, and that it is a fast and convenient dry chemical process performed by a standard inductively coupled plasma etcher using the Bosch process. Different patch lengths (200-1000 mum) of C4F8 were deposited in 50 mum wide channels to evaluate which size is most suitable for microfluidic biochemical applications. The valve function of the hydrophobic patches was tested for the following liquids: DD water, acetone, propanol, bead solution and a mixture used for pyrosequencing of DNA. Patch lengths of 200 mum of C4F8 successfully stopped each solution for at least 20 consecutive times. The C4F8 film resists water for at least 5 h. The hydrophobic valve also resists very high concentrations (25%) of surfactants (Tween 80). C4F8 shows a much higher resistance towards water and surface active solutions than previous hydrophobic patches. However, 50% Tween 80 was not stopped at all by the hydrophobic patch. An applied pressure of 760 Pa at the inlet was needed for water to over-run the hydrophobic patch.

  • 33.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    van der Wijngaart, Wouter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Nilsson, Peter
    KTH, Superseded Departments, Biotechnology.
    Enoksson, P.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A valve-less diffuser micropump for microfluidic analytical systems2001In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 72, no 3, p. 259-265Article in journal (Refereed)
    Abstract [en]

    The suitability of valve-less micropumps in biochemistry has been shown. Fluids encountered in various biochemical methods that are problematic for other micropumps have been pumped with good performance. The pump is fabricated as a silicon-glass stack with a new process involving three subsequent deep reactive ion etching steps. Some of the main advantages of the valve-less diffuser pump are the absence of moving parts (excluding the pump diaphragm), the uncomplicated planar design, and high pump performance in terms of pressure head and flow rare. In addition, the micropump is self-priming and insensitive to particles and bubbles present in the pumped media. The results show that the valve-less micropump successfully pumps fluids within the viscosity range of 0.001-0.9 N s/m(2). The micropump is not sensitive to the density, ionic strength, or pH of the pumped media. Effective pumping of solutions containing beads of different sizes was also demonstrated. Living cells were pumped without inducing cell damage and no cell adhesion within the pump chamber was found. No valve-less micropump has previously been reported to pump such a wide variety of fluids.

  • 34.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    van der Wijngaart, Wouter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Micromachined filter-chamber array with passive valves for biochemical assays on beads2001In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 22, no 2, p. 249-257Article in journal (Refereed)
    Abstract [en]

    The filter-chamber array presented here enables a real-time parallel analysis of three different samples on beads in a volume of 3 nL, on a 1 cm(2) chip. The filter-chamber array is a system containing three filter-chambers, three passive valves at the inlet channels and a common outlet. The design enables parallel sample handling and time-controlled analysis. The device is microfabricated in silicon and sealed with a Pyrex lid to enable real-time analysis. Single nucleotide polymorphism analysis by using pyrose-quencing has successfully been performed in single filter-chamber devices. The passive valves consist of plasma-deposited octafluorocyclobutane and show a much higher resistance towards water and surface-active solutions than previous hydrophobic patches. The device is not sensitive to gas bubbles, clogging is rare and reversible, and the filter-chamber array is reusable. More complex (bio)chemical reactions on beads can be performed in the devices with passive valves than in the devices without valves.

  • 35.
    Andersson, Sören
    et al.
    Linköping University.
    Millnert, Mille
    Linköping University.
    Viberg, Mats
    Linköping University.
    Wahlberg, Bo
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A study of adaptive arrays for mobile communication systems1991In: Proceedings - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing, Toronto, Ont, Can, 1991, Vol. 5, no Piscataway, NJ, United States, p. 3289-3292Conference paper (Refereed)
    Abstract [en]

    The application of adaptive antenna techniques to increase the channel capacity in mobile radio communication is discussed. Directional sensitivity is obtained by using an antenna array at the base station, possibly both in receiving and transmitting mode. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction finding following by optimal combination of the antenna outputs. Comparisons to a method based on reference signals are made. Computer simulations are carried out to test the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting cochannel interference, albeit at the expense of high computational requirements.

  • 36.
    Andersson, Tomas
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Selected topics in frequency estimation2003Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    Frequency estimation has been studied for a number of years.One reason for this is that the problem is easy to understand,but difficult to solve. Another reason, for sure, is the largenumber of applications that involves frequency estimation, e.gradar applications using frequency modulated continuous wave(FMCW) techniques where the distance to the target is embeddedin the frequency, resonance sensor system where the outputsignal is given as the frequency displacement from a nominalfrequency, in radio frequency identification systems (RFID)where frequency modulation is used in the communication link,etc. The requirement on the frequency estimator varies with theapplication but typical issues are: accuracy, processing speedor complexity, and ability to handle multiple signals. Many ofthe problems have been solved but there still exist severalopen questions.

    The first part of this thesis addresses the problem offrequency estimation using low complexity algorithms. One wayof achieving such an algorithm is to use 1-bit quantizedsamples of the input signal. Frequency estimation using look-uptables has been studied and the properties of such an estimatorare presented. By analyzing the look-up tables using theHadamard transform a novel type of low-complexity frequencyestimators is proposed. They use operations such as binarymultiplication and addition of precalculated constants. Thisfact makes it suitable in applications where low complexity isa major issue. A hardware demonstrator using the table look-uptechnique has been build and a short description of it isincluded in the thesis.

    Today, the interest of using digital signal processinginstead of analog processing is almost absolute. Accordingly,analog-to-digital converters (ADC) are used in order todigitalize the analog input before digital processing is takenplace. The ADC performance is measured according to the IEEEStandard 1241. The waveform fitting method included in thestandard has been studied in some detail. A criterion for modelselection has been derived using the parsimony principle.Further, an algorithm has been derived for estimation of theparameters of multiple sinusoids using the standardizedwave-fitting method, in combination with the expectationmaximization (EM) algorithm. The performance of the algorithmhas been studied and it is shown to produce statisticallyefficient estimates.

  • 37.
    Andersson, Tomas
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    IEEE Standard 1057, Cramér-Rao Bound and the Parsimony Principle2003In: International Workshop on ADC Modelling and Testing, 2003, p. 231-234Conference paper (Refereed)
  • 38.
    Andersson, Tomas
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Multiple-tone estimation by IEEE standard 1057 and the expectation-maximization algorithm2003In: IMTC/O3: PROCEEDINGS OF THE 20TH IEEE INSTRUMENTATION AND MEASUREMENT TECHNOLOGY CONFERENCE, 2003, p. 739-742Conference paper (Refereed)
    Abstract [en]

    The aim of this work is to present an efficient algorithm for multiple-tone parameter estimation. The algorithm is inspired by the expectation-maximization algorithm, and it utilizes the IEEE standard 1057 for single tone parameter estimation. In the derivation of the algorithm it is assumed that the number of tones are known and that the frequencies are well separated The algorithm is evaluated using data consisting of multiple real-valued tones. The performance of the frequency estimator is studied and compared with the asymptotic Cramer-Rao bound (CRB). It is shown that the algorithm produces statistically efficient frequency estimates at high signal to noise ratios, that is the variance of the estimates reaches the CRB. Finally, it is shown that the algorithm can produce efficient estimates independent of the number of tones in the input signal.

  • 39.
    Andersson, Tomas
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Standardized sine-wave fitting algorithms, extensions and applications2003In: Northern Light Workshop on Sensors, Signals and Systems, Björkliden, Sverige, April 7-9, 2003, 2003Conference paper (Refereed)
    Abstract [en]

    The objective of this paper is to present the statistical properties of the IEEE-STD-1057/IEEE-STD-1241 sine-wave fitting algorithms. The proper Cramér-Rao bound is derived for both the three-parameter and four-parameter algorithms. Further, we investigate the residual, and derive its statistical properties, in both the three- and four-parameter fitting case. In a practical setup were the frequency is almost known, we derive an analytical expression for the mean of the residual. By analysis we compare the two methods and state in which case one should use one over the other. Finally, we present some numerical evaluations confirming our analytical findings.

  • 40.
    Andersson, Tomas
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Toward a Standardized Multi-Sinewave Fit Algorithm2004In: 9th European Workshop on ADC Modelling and Testing, 2004, Vol. 1, p. 337-342Conference paper (Refereed)
    Abstract [en]

    Multi-sinewave test methods require algorithms for multiple-tone parameter estimation.There exist a vast amount of publications on the topic [1]. This paper presents a generalization ofthe IEEE four-parameter sinewave fit algorithm suitable to handle data comprising multiple sinewaves.The proposed method directly estimates the 3p + 1 parameters of a p-tone model. The algorithmis analyzed numerically with emphasize on its convergence properties and statistical efficiency. Theinitialization of the algorithm is of major importance and an attempt to formulate a proper initializationprocedure is presented.

  • 41.
    Andersson, Tomas
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Skoglund, Mikael
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Frequency estimation utilizing the Hadamard transform2001In: 2001 IEEE WORKSHOP ON STATISTICAL SIGNAL PROCESSING PROCEEDINGS, NEW YORK: IEEE , 2001, p. 409-412Conference paper (Refereed)
    Abstract [en]

    Fast analog to digital conversion with only one bit per sample does not only make high sampling rates possible but also reduces the required hardware complexity. For short data buffers or block lengths, it has been shown that tone frequency estimators can be implemented by a simple table look-up. In this paper we present an analysis of such tables using the Hadamard transform. As an outcome of the analysis, we propose a class of nonlinear estimators of low complexity. Their performance is evaluated using numerical simulations. Comparisons are made with the proper Cramer-Rao bound and with the table look-up approach.

  • 42.
    Arvedson, Mats
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Edlund, Magnus
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Eriksson, Ola
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Nordin, Andreas
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Furuskär, Anders
    Ericsson AB, SE-164 80 Stockholm, Sweden.
    Packet or Circuit Switched Voice Radio Bearers-A Capacity Evaluation for GERAN2002Conference paper (Refereed)
    Abstract [en]

    GERAN, including the EDGE radio interface, con-stitutes the 3G evolution of GSM. The use of packet switched voice radio bearers has been discussed in the GERAN standardization, but has as yet not been adopted. This paper presents a thorough capacity comparison of circuit and packet switched voice bearers, applied to GERAN. Thus the standardization decision is verified, but also a framework for future similar investigations is provided. Several parameters affect the relative performance of circuit and packet switching. This report evaluates the effect of four of these parameters, expected to have major impact on the relative performance: reuse factor, resource pool size, voice activity, and additional overhead in the packet switched case. Varying the above parameters, it is seen that in certain blocking-limited scenarios packet switching may increase capacity significantly. The highest overall capacity is however achieved in inter-ference-limited scenarios, for which packet switching provides no capacity gain.

  • 43. Astrom, K. J.
    et al.
    Johansson, Karl H.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Wang, Q. G.
    Design of decoupled PI controllers for two-by-two systems2002In: IEE Proceedings - Control Theory and Applications, ISSN 1350-2379, E-ISSN 1359-7035, Vol. 149, no 1, p. 74-81Article in journal (Refereed)
  • 44.
    Astély, David
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Spatial and spatio-temporal processing with antenna arrays in wireless systems1999Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    This thesis treats some modeling and estimation problems inthe fieldof antenna array signal processing. With multipleantennas at thereceive side, the spatial dimension is added,and processing is performed in both the temporal and spatialdomain. The work is motivated by the interest in using antennaarrays, primarily at thebase stations, in wirelesscommunication systems. Among thepotential benefits areincreased range, fading diversity, interferencerejection andspatially selective transmission.

    The problem of estimating the non-frequency selectivechannels, referred to as spatial signatures, for a uniformlinear array withunknown receiver gain and phase responses isstudied. Sufficientconditions for identifying the spatialsignatures using a plane wavemodel with subspace based methodsare derived, and a closed formESPRIT-like estimator isproposed. Results from simulations andprocessing ofexperimental data show that the absence of receivercalibrationis not critical for uplink signal waveform estimationusing aplane wave model.

    The effects of angular spread caused by multipathpropagation from local scatterers on direction of arrival (DOA)estimation with theMUSIC algorithm are studied. Under theassumption of small angularspread, an approximate distributionof the DOA estimates is derived. An extension to more generalRayleigh and Ricean fading channels is included. Experimentaldata collected in suburban environments havebeen processed, andthe results agree well with the derived distribution.

    A generalized array manifold model for parameterized spatialsignatureestimation in environments with local scattering isproposed. Thearray manifold commonly used for plane waves isgeneralized toinclude linear combinations of the nominal arrayresponse vectors andtheir derivatives. To estimate theparameters of the model, severalsubspace based estimators areproposed.

    Spatio-temporal interference rejection combining fordigitalcommunication systems is considered. The use of a finiteorder linear predictor to take the temporal correlation of theco-channelinterference (CCI) into account is studied, and amaximum likelihoodsequence estimator which handles bothintersymbol interference andtemporally correlated CCI ispresented. Spatio-temporal interferencerejection may providelarge gains over space-only interferencerejection, whichneglects the temporal correlation, especially ininterferencelimited scenarios with angular spread and timedispersion. trainingsequence based estimator of the parametersfor the sequence estimatorwith spatio-temporal interferencerejection is proposed. Resultsfrom processing data collected ina suburban environment with a dualpolarized sector antenna of aGSM base station test bed are presented.

  • 45.
    Astély, David
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Constrained Complexity Spatio-Temporal Interference Rejection Combining1999In: Proceedings of SPAWC’99, Signal Processing Advances in Wireless Communications, IEEE , 1999, p. 110-113Conference paper (Refereed)
    Abstract [en]

    Space-time processing for co-channel interference (CCI) rejection and equalization with antenna arrays may provide large gains over space-only processing, especially in interference limited scenarios. However, taking thetemporal correlation of the noise and CCI process into account leads to sequence detection with highercomplexity as compared to space-only processing that neglects this correlation. We propose the use of the generalized Viterbi algorithm for sequence detection with lower complexity. Special cases include the M-algorithm and the delayed decision feedback sequence estimator. A relevant comparison between spatial andspatio-temporal processing with sequence detectors of the same complexity may thus be performed. Numerical examples show substantial gains for spatio-temporal processing as compared to space-only processing also in this case when the optimality of the sequence detector is traded for interference rejection.

  • 46.
    Astély, David
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    MLSE and Spatio-Temporal Interference Rejection Combining with Antenna Arrays1998In: Proceedings of Eusipco-98, Ninth European Signal Processing Conference, Island of Rhodes, Greece, 1998, p. 1341-1344Conference paper (Refereed)
  • 47.
    Astély, David
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    On Spatio-Temporal Interference Rejection Combining with Antenna Arrays1998Other (Refereed)
  • 48.
    Astély, David
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    The effects of local scattering on direction of arrival estimation with MUSIC1999In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 47, no 12, p. 3220-3234Article in journal (Refereed)
    Abstract [en]

    In wireless communication scenarios, multipath propagation may cause angular spreading as seen from a base station antenna array. Environments where most energy incident on the array is from scatterers local to the mobile transmitters are considered, and the effects on direction of arrival (DOA) estimation with the MUSIC algorithm are studied. Previous work has studied rapidly time-varying channels and concluded that local scattering has a minor effect on DOA estimation in such scenarios. In this work, a channel that is time-invariant during the observation period is considered, and under the assumption of small angular spread, an approximate distribution for the DOA estimates is derived. The results show that local scattering has a significant impact on DOA estimation in the time invariant case. Numerical examples are included to illustrate the analysis and to demonstrate that the results may be used to formulate a simple estimator of angular spread. An extension to more general Rayleigh and Ricean fading channels is also included, In addition, results from processing experimental data collected in suburban environments are presented. Good agreement with the derived distributions is obtained.

  • 49.
    Astély, David
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Swindlehurst, Andrew Lee
    Department of Electrical and Computer Engineering, Brigham Young University, Provo, UT 84602 USA.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Spatial signature estimation for uniform linear arrays with unknown receiver gains and phases1999In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 47, no 8, p. 2128-2138Article in journal (Refereed)
    Abstract [en]

    The problem of spatial signature estimation using a uniform linear array (ULA) with unknown receiver gain and phase responses is studied. Sufficient conditions for identifying the spatial signatures are derived, and a closed-Form ESPRIT-like estimator is proposed, The performance of the method is investigated by means of simulations and on experimental data collected with an antenna array in a suburban environment. The results show that the absence of receiver calibration is not critical for uplink signal waveform estimation using a plane wave model.

  • 50.
    Asztély, David
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Spatial models for narrowband signal estimation with antenna arrays1997Licentiate thesis, monograph (Other scientific)
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