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  • 7451.
    Öhman, Andreas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Jonsson, Oskar
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Simulering och implementering av ett elektriskt motorsystem för minimering av hastighetvariationer2018Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Syftet med examensarbetet är att utse en lämplig ersättare för en motor i en av Saab Dynamics produkter. Den tidigare motorn är en synkronmotor av typen hysteresmotor och nu söks en billigare lösning med liknande prestanda. Applikationen kräver att motorn från stillastående ska kunna accelereras till 600 varv per minut på maximalt 0,5 sekunder. Efter 0,5 sekunder ska medelhastigheten per varv maximalt avvika med 0,2 promille. I utveckling av en ny lösning ingår val av motortyp, styrelektronik och givare samt design av regleralgoritmer. I rapporten beskrivs ett antal motorer som kan vara lämpliga ersättare till den tidigare motorn samt deras styrkor och svagheter. Sedan följer en undersökning och implementation av en av de lämpliga kandidaterna, en borstlös likströmsmotor. Val av givare och styrteknik för den motortypen beskrivs och motorns lämplighet undersöks i en modell skapad i Mathworks Simulinkmiljö där ett reglersystem implementeras. Simuleringar visa att den valda motorn är lämplig för en praktisk implementation. Slutligen beskrivs konstruktionen av en testuppställning som innefattar motor, givare och styrteknik implementerad i en processor som ställer ut strömmen till motorn för att uppnå önskad hastighet. Uppställningen uppfyller kravet i testkörningar och i den bästa körningen är hastighetsvariationerna 7,4 gånger mindre än det specificerade kravet.

  • 7452.
    Öhman, Fredrik
    Linköpings universitet, Institutionen för systemteknik.
    Modulgenerator för Matchade Transistorpar2005Independent thesis Basic level (professional degree)Oppgave
    Abstract [sv]

    Detta examensarbete syftar till att implementera en modulgenerator som automatiskt genererar ett matchat differentialpar. Detta för att enkelt kunna generera detta vanlig förekommande byggblock utan att behöva rita om allt från grunden.

    Modulgeneratorn som konstruerats klarar att skapa upp till 2x2 transistor block matchad layout med eller utan sköld. Programmet skapar med hjälp av indata från konstruktören en skräddarsydd layout som kan användas som byggblock i integrerade kretsar.

    Examensarbetet är slutfört och har genomgått omfattande testning

    The aim of this thesis is to implement a module generator that automatically generates a matched differential pair. That is, to easily create new pairs without having to draw everything from scratch.

    The module generator is able to create matched layouts with up to 2x2 transistor blocks with or without a guard-ring. The program uses a number of input parameters from the user to customize the layout. Hence, the generated blocks can be used in a large range of analog integrated circuits.

  • 7453.
    Öhr, Jonas
    et al.
    ABB, Sweden.
    Moberg, Stig
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Wernholt, Erik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hanssen, Sven
    ABB, Sweden.
    Pettersson, Jens
    ABB, Sweden.
    Persson, Sofie
    ABB, Sweden.
    Sander-Tavallaey, Shiva
    ABB, Sweden.
    Identification of Flexibility Parameters of 6-axis Industrial Manipulator Models2006Inngår i: Proceedings of the 2006 International Conference on Noise and Vibration Engineering, 2006, s. 3305-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A method for identification of flexibility parameters of a 18 DOF (degrees offreedom) robot prototype model is proposed. Experiments show the strengthof the method and the results indicates that flexibilities in the bearings and thearms, taken together, are of the same order as the flexibilities in the gears.

  • 7454.
    Öhr, Jonas
    et al.
    ABB, Sweden.
    Moberg, Stig
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Wernholt, Erik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hanssen, Sven
    ABB, Sweden.
    Pettersson, Jens
    ABB, Sweden.
    Persson, Sofie
    ABB, Sweden.
    Sander-Tavallaey, Shiva
    ABB, Sweden.
    Identification of Flexibility Parameters of 6-axis Industrial Manipulator Models2006Rapport (Annet vitenskapelig)
    Abstract [en]

    A method for identification of flexibility parameters of a 18 DOF (degrees offreedom) robot prototype model is proposed. Experiments show the strengthof the method and the results indicates that flexibilities in the bearings and thearms, taken together, are of the same order as the flexibilities in the gears.

  • 7455.
    Öhrn, Philip
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Åstrand, Markus
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Direct Lift Control of Fighter Aircraft2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Direct lift control for aircraft has been around in the aeronautical industry for decades but is mainly used in commercial aircraft with dedicated direct lift control surfaces. The focus of this thesis is to investigate if direct lift control is feasible for a fighter aircraft, similar to Saab JAS 39 Gripen, without dedicated control surfaces.

    The modelled system is an aircraft that is inherently unstable and contains nonlinearities both in its aerodynamics and in the form of limited control surface deflection and deflection rates. The dynamics of the aircraft are linearised around a flight case representative of a landing scenario. Direct lift control is then applied to give a more immediate relation from pilot stick input to change in flight path angle while also preserving the pitch attitude.

    Two different control strategies, linear quadratic control and model predictive control, were chosen for the implementation. Since fighter aircraft are systems with fast dynamics it was important to limit the computational time. This constraint motivated the use of specialised methods to speed up the optimisation of the model predictive controller.

    Results from simulations in a nonlinear simulation environment supplied by Saab, as well as tests in high-fidelity flight simulation rigs with a pilot, proved that direct lift control is feasible for the investigated fighter aircraft. Sufficient control authority and performance when controlling the flight path angle were observed. Both developed controllers have their own advantages and which strategy is the most suitable depends on what the user prioritises. Pilot workload during landing as well as precision at touch down were deemed similar to conventional control.

  • 7456.
    Öijerholm, Mikael
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Institutionen för systemteknik.
    Aspects of the choice of sampling frequency in the control system of a gas turbine2009Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    At Siemens, plcs are used to control the gas turbines, and to execute the code in the plcs cyclic interrupts are used. If the execution time for the interrupt becomes close to the cyclic time of the interrupt the load of the plc increases. High load levels can lead to situations were segments of code are not executed on time or even not executed at all. In this thesis an analysis of the regulators used to govern a gas turbine has been performed. The purpose of the analysis is to study the performance of the regulators for different cycle times with the aim to be able to reduce the load by sampling more slowly.

    To determine the load contribution from each regulator a review of the regulators and their execution times has been made. For the analysis the Matlab program Simulink has been used to make models of the regulators, which have then been sampled at different rates. With this information it is possible to determine for which cycle times each regulator has accepetable performance and how much load each regulator contributes with. A save of load of approximately 2 percent can be obtained without loosing too much performance.

  • 7457.
    Öresjö, Per
    Linköpings universitet, Institutionen för systemteknik.
    A High Speed Sigma Delta A/D-Converter for a General Purpose RF Front End in 90nm-Technology2007Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this report a transistor-level design of a GHz Sigma-Delta analog-to-digital converter for an RF front end is proposed. The design is current driven, where the integration is done directly over two capacitances and it contains no operational amplifiers.

    The clock frequency used for verification was 2.5 GHz and the output band-width was 10 MHz. The system is flexible in that the number of internal bits can be scaled easily and in this report a three-bit system yielding an SNR of 76.5 dB as well as a four-bit system yielding an SNR of 82.5 dB are analyzed.

  • 7458.
    Örn, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Szilassy, Martin
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Dil, Bram
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    A Novel Multi-Step Algorithm for Low-Energy Positioning Using GPS2016Inngår i: Fusion 2016, 19th International Conference on Information Fusion: Proceedings, 2016, s. 1469-1476Konferansepaper (Fagfellevurdert)
    Abstract [en]

    GPS is widely used for localization and tracking, however traditional GPS receivers consume too much energy for many applications. This paper implements and evaluates the performance of a low-energy GPS prototype. The main difference is that a traditional GPS needs to sample signals transmitted by satellites for 30 seconds to estimate its position. Our prototype reduces this time by three orders of magnitude and it can compute positions from only 2 milliseconds of data. We present a new algorithm that increases robustness by filtering on estimated residuals instead of using an altitude database. In addition, we show that our new algorithm works with both fixed and moving targets. The solution consists of (1) a portable device that samples the GPS signal and (2) a server that utilizes Doppler navigation and Coarse Time Navigation to estimate positions. We performed tests in a wide variety of environments and situations. These tests show that our prototype provides a median positioning error of roughly 40 meters even when the GPS receiver is moving at 80 kilometres per hour.

  • 7459.
    Örn, Sara
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Realistic Multi-Cell Interference Coordination in 4G/LTE2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In the LTE mobile system, all cells use the same set of frequencies. This means that a user could experience interference from other cells. A method that has been studied in order to reduce this interference and thereby increase data rate or system throughput is to coordinate scheduling between cells. Good results of this have been found in different studies. However, the interference is generally assumed to be known. Studies using estimated interference and simulating more than one cluster of cells have found almost no gain.

    This thesis will focus on how to use information from coordinated scheduling and other traffic estimates to do better interference estimation and link adaption. The suggested method is to coordinate larger clusters and use the coordination information, as well as estimates of which cells will be transmitting, to make estimates of interference from other cells. The additional information from interference estimation is used in the link adaptation. Limitations in bandwidth of the backhaul needed to send data between cells are considered, as well as the delay it may introduce. A limitation of the scope is that MIMO or HetNet scenarios have not been simulated.

    The suggested method for interference estimation and link adaptation have been implemented and simulated in a system simulator. The method gives a less biased estimate of SINR, but there are no gains in user bit rate. The lesser bias is since the method is better at predicting high SINR than the base estimate is. The lack of gains regarding user bit rate may result from the fact that in the studied scenarios, users where not able to make use of the higher estimated SINR since the base estimate is already high.

    The conclusion is that the method might be useful in scenarios where there are not full load, but the users either have bad channel quality or are able to make use of very high SINR. Such scenarios could be HetNet or MIMO scenarios, respectively.

  • 7460.
    Östberg, Gustav
    Linköpings universitet, Institutionen för systemteknik.
    A Comparative Study of Efficient Power Amplifiers in CMOS2008Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    During later years communication schemes for handheld devices have increased in complexity due to the desire to increase the throughput, i.e. the amount of information sent over a medium simultaneously. Increasing throughput can be accomplished, not only by modulating the phase or frequency, but also the amplitude. This leads to tougher requirements on the power amplifier. The conventional power amplifiers, which have the ability to follow the envelope of the carrier, are inefficient. This thesis aims to compare two old but revived architectures which exploit high-efficiency amplifiers and still have a linear relationship between the input and output. The architectures; the Polar Linearization Technique and Outphasing share the same foundation. Based on literature, the polar technique have been more successful of employing examples fufilling communication standards. The polar technique is also more versatile regarding power combiners, distortion correction and alternative implementations. The simulations performed in this thesis results show that the polar amplifier is less sensitive to process variations and has higher maximum efficiency. On the other hand, the outphasing topology have the highest linearity figures.

  • 7461.
    Österberg, Johan
    et al.
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Ekblom, Carl-David
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    USB 2.0 Audio device2012Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    The main task of this project were to develop, hardware and software that could stream audio data via USB 2.0. This project were based on XMOS, USB 2.0 design. In this project we have brought an idea to reality in the form of a finished product. This with verification help from engineers on Syncore technologies. Under the development process the functionality surrounding component databases, provided by Altium designer, were to be evaluated. To be mentioned is that Altium designer was the software used to develop the PCB in this project. After many hours spent developing, we finally got the hardware and software to behave in the way it was suppose to do. That is, to be able to stream audio data from a high-resolution source(PC/MAC/unit with S/PDIF out, maximum resolution 24-bit 192 kHz). This to both S/PDIF and analog stereo out via RCA-connectors. The sound quality from a possible subjective point of view is very good and we are happy with the result. We think that the functionality surrounding component databases are convenient in many applications. Not just the fact that you easily can generate an up to date pricing of all components used in a project, you can also shorten the development process. This because the developer don't have to recreate schematic symbols and footprints that has already been created. Which of course was the fundamental idea behind the database functionality. These are just a few examples of its advantages. To be considered is the fact that the administration surrounding the component databases can be very time consuming. To take full advantage of Altium designers functionalities we think that it needs a dedicated administrator that maintains the database repository.

  • 7462.
    Östh, Joakim
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Study of Six-Port Modulators and Demodulators for High-Speed Data Communications2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    There is an increasing demand for high-speed wireless data communications to support consumers’ need for, among other things, real time streaming of high definition video and fast file transfers. One radio architecture that has a potential to meet the increasing demand for high-speed data communications is a radio technique based on the six-port architecture. In addition to high-speed, the six-port radio also allows low power consumption and low cost. In this thesis, a comprehensive study of the six-port radio technique for high data rate (> 1 Gbit/s) and low complexity are presented.

    Firstly, a technique to suppress the carrier leakage was proposed, analyzed and verified by measurements. The proposed technique uses only a phase shifting network between the six-port correlator and its variable impedance loads, hence it is easy to implement. When the proposed carrier leakage suppression technique is used together with differential control signals, it also has the benefit of both improving the linearity and increasing the output power of the modulator. The same carrier leakage suppression technique can also be used in a six-port demodulator (receiver) to improve its performance.

    Secondly, Schottky diodes were proposed to be used as high-speed variable impedance loads. A six-port modulator operating at 7.5 GHz, using the carrier leakage suppression technique together with Schottky diodes as variable impedance loads, was manufactured. Measurements on a 16 quadrature amplitude modulated (QAM) signal with a symbol rate of 300 Msymbol/s, i.e., a data rate of 1.2 Gbit/s, have proved high-speed operation, good modulation properties as well as carrier leakage suppression.

    Thirdly, a six-port demodulator was built for high data rate applications and measurements were conducted to characterize its performance. Demodulation of a 16-QAM signal at a data rate of 1.67 Gbit/s results in an acceptable bit error rate and error vector magnitude (EVM) performance.

    Last but not least, new diode configurations were proposed, analyzed and verified for use in six-port demodulators. Using the proposed diode configurations, the use of differential amplifiers, as commonly used in a six-port demodulator, can be avoided. Avoiding the use of differential amplifiers allows high-speed processing and at the same time reduces the power consumption and implementation complexity. In the context of the new diode configurations, it was shown that a six-port receiver has better EVM vs frequency performance and lower implementation complexity, compared to a five-port or four-port receiver.

    Delarbeid
    1. Direct Carrier Six-Port Modulator Using a Technique to Suppress Carrier Leakage
    Åpne denne publikasjonen i ny fane eller vindu >>Direct Carrier Six-Port Modulator Using a Technique to Suppress Carrier Leakage
    Vise andre…
    2011 (engelsk)Inngår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 59, nr 3, s. 741-747Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    This paper presents a direct carrier six-port modulator. To allow arbitrary load impedances to be used and for suppression of carrier leakage, a new circuit architecture with a technique to suppress carrier leakage is proposed and implemented. A theoretical model of the proposed modulator is derived. A prototype modulator utilizing diodes for impedance generation is designed and fabricated for a center frequency of 7.5 GHz for verification of the proposed technique. Measurements show good modulation properties when a 16 quadrature amplitude modulation signal at 100 Msymbol/s is generated, as well as good carrier leakage suppression.

    sted, utgiver, år, opplag, sider
    IEEE Institute of Electrical and Electronics, 2011
    Emneord
    Carrier leakage suppression, direct carrier modulator, six-port correlator
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-67308 (URN)10.1109/TMTT.2011.2104972 (DOI)000288460500026 ()
    Tilgjengelig fra: 2011-04-08 Laget: 2011-04-08 Sist oppdatert: 2019-06-17bibliografisk kontrollert
    2. Carrier Leakage Suppression and EVM Dependence on Phase Shifting Network in Six-Port Modulator
    Åpne denne publikasjonen i ny fane eller vindu >>Carrier Leakage Suppression and EVM Dependence on Phase Shifting Network in Six-Port Modulator
    2012 (engelsk)Konferansepaper, Oral presentation only (Fagfellevurdert)
    Abstract [en]

    In six-port modulators a phase shifting network on specific ports can be used to suppress the carrier leakage that may be present if this network is not present. A model is derived to predict the carrier leakage suppression and error vector magnitude (EVM) as a function of the phase shifting network Sparameters. Both carrier leakage suppression and EVM can be expressed by the same error function. The error function can be used to find the allowed amplitude and phase mismatch in the phase shifting network, or to optimize the performance of a phase shifting network over a given frequency range. A broadband phase shifting network, based on a loaded transmission line, is designed and optimized to operate at a relative bandwidth of 60% for an EVM < 10%. This should be compared to a phase shifting network based on a single transmission line with a corresponding bandwidth of only 12%. The broadband phase shifting network is useful for six-port modulators with carrier leakage suppression, targeting UWB applications.

    sted, utgiver, år, opplag, sider
    IEEE, 2012
    Emneord
    Six-Port Modulator, Carrier Leakage, EVM, Broadband
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-77194 (URN)10.1109/ICMMT.2012.6230247 (DOI)978-1-4673-2184-6 (ISBN)
    Konferanse
    International Conference on Microwave and Millimeter Wave Technology ICMMT, May 5-8, Shenzhen, China
    Tilgjengelig fra: 2012-05-08 Laget: 2012-05-08 Sist oppdatert: 2019-06-17bibliografisk kontrollert
    3. Schottky diode as high-speed variable impedance load in six-port modulators
    Åpne denne publikasjonen i ny fane eller vindu >>Schottky diode as high-speed variable impedance load in six-port modulators
    Vise andre…
    2011 (engelsk)Inngår i: ICUWB 2011: 2011 IEEE International Conference on Ultra-Wideband (ICUWB), 2011, s. 68-71Konferansepaper, Oral presentation only (Fagfellevurdert)
    Abstract [en]

    The use of Schottky diodes as high-speed variable impedance loads in six-port modulators are proposed and analyzed in this paper. The impedance dependency of diode parameters and local oscillator power are investigated by theoretical analysis and simulations. A prototype for a direct carrier six-port modulator using Schottky diodes for impedance generation is designed and fabricated for a center frequency of 7.5 GHz. Measurements show good modulation properties when a 16 quadrature amplitude modulation signal at 300 Msymbol/s is generated, i.e., at a data rate of 1.2 Gbit/s, validating the use of Schottky diodes as high-speed variable impedance loads in six-port modulators.

    Serie
    IEEE International Conference on Ultra- Wideband (ICUWB), ISSN 2162-6588 ; 2011
    Emneord
    Schottky diodes, electric impedance measurement, modulators, oscillators, quadrature amplitude modulation
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-77196 (URN)10.1109/ICUWB.2011.6058924 (DOI)978-1-4577-1762-8 (ISBN)978-1-4577-1763-5 (ISBN)
    Konferanse
    IEEE International Conference on Ultra-Wideband (ICUWB),14-16 September, 2011, Bologna, Spain
    Tilgjengelig fra: 2012-05-08 Laget: 2012-05-08 Sist oppdatert: 2019-06-17bibliografisk kontrollert
    4. Six-Port Gigabit Demodulator
    Åpne denne publikasjonen i ny fane eller vindu >>Six-Port Gigabit Demodulator
    Vise andre…
    2011 (engelsk)Inngår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 59, nr 1, s. 125-131Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    This paper presents measurement results for a six-port-based demodulator designed for a center frequency of 7.5 GHz and with a bandwidth of 1 GHz for operation in the ultra-wideband band. The demodulator includes the six-port correlator, diodes, and amplifiers needed to recover the baseband data. Measurement results show that the prototype supports data rates at 1.7 Gbit/s with bit-error rate 5 . 10(-5) if a two-tap linear equalizer is used and bit-error rate 4 . 10(-3) if only threshold detection is used. The measured performance of the used six-port correlator including the amplifiers is presented and their influence on the overall system performance is discussed. Limitations in the present system and possible improvements are also considered.

    sted, utgiver, år, opplag, sider
    IEEE Institute of Electrical and Electronics, 2011
    Emneord
    Demodulator, six-port correlator
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-66297 (URN)10.1109/TMTT.2010.2091198 (DOI)000286109400015 ()
    Tilgjengelig fra: 2011-03-11 Laget: 2011-03-11 Sist oppdatert: 2019-06-17bibliografisk kontrollert
    5. Diode Configurations in Six-Port Receivers with Simplified Interface to Amplifier and Filter
    Åpne denne publikasjonen i ny fane eller vindu >>Diode Configurations in Six-Port Receivers with Simplified Interface to Amplifier and Filter
    Vise andre…
    2010 (engelsk)Inngår i: 2010 IEEE International Conferenceon Ultra-Wideband (ICUWB2010): Proceedings – Volume 1, Piscataway, NJ, USA: IEEE , 2010, s. 1-4Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    This paper presents two new diode configurations for use with six-port based demodulators. The first proposed diode configuration allows a simplified diode to filter/amplifier interface. The second configuration allows for full-wave rectification and suppression of odd-order harmonics. A demodulator prototype utilizing the new diode concept is designed for a center frequency of 7.5 GHz and with a bandwidth of 1 GHz for verification. The demodulator includes the six-port correlator, diodes and amplifiers needed to recover the baseband data.

    sted, utgiver, år, opplag, sider
    Piscataway, NJ, USA: IEEE, 2010
    Emneord
    amplifiers, demodulators, diodes, radio receivers
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-77198 (URN)10.1109/ICUWB.2010.5615597 (DOI)978-1-4244-5306-1 (ISBN)978-1-4244-5305-4 (ISBN)
    Konferanse
    IEEE International Conference on Ultra-Wideband (ICUWB),20-23 September, 2010, Nanjing, China
    Tilgjengelig fra: 2012-05-08 Laget: 2012-05-08 Sist oppdatert: 2019-06-17bibliografisk kontrollert
    6. Performance Evaluation of Six-Port Receivers with Simplified Interface to Amplifier and Filter
    Åpne denne publikasjonen i ny fane eller vindu >>Performance Evaluation of Six-Port Receivers with Simplified Interface to Amplifier and Filter
    Vise andre…
    2011 (engelsk)Konferansepaper, Oral presentation only (Fagfellevurdert)
    Abstract [en]

    In six-port modulators a phase shifting network on specific ports can be used to suppress the carrier leakage that may be present if this network is not present. A model is derived to predict the carrier leakage suppression and error vector magnitude (EVM) as a function of the phase shifting network Sparameters. Both carrier leakage suppression and EVM can be expressed by the same error function. The error function can be used to find the allowed amplitude and phase mismatch in the phase shifting network, or to optimize the performance of a phase shifting network over a given frequency range. A broadband phase shifting network, based on a loaded transmission line, is designed and optimized to operate at a relative bandwidth of 60% for an EVM < 10%. This should be compared to a phase shifting network based on a single transmission line with a corresponding bandwidth of only 12%. The broadband phase shifting network is useful for six-port modulators with carrier leakage suppression, targeting UWB applications.

    Emneord
    Six-Port Modulator, Carrier Leakage, EVM, Broadband
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-77200 (URN)10.1109/ICUWB.2011.6058824 (DOI)978-1-4577-1762-8 (ISBN)978-1-4577-1763-5 (ISBN)
    Konferanse
    IEEE International Conference on Ultra-Wideband (ICUWB), 14-16 September 2011, Bologna, Spain
    Tilgjengelig fra: 2012-05-08 Laget: 2012-05-08 Sist oppdatert: 2019-06-17bibliografisk kontrollert
    7. Data and Carrier Interleaving in Six-Port Receivers for Increased Data Rate
    Åpne denne publikasjonen i ny fane eller vindu >>Data and Carrier Interleaving in Six-Port Receivers for Increased Data Rate
    Vise andre…
    2010 (engelsk)Inngår i: 2010 IEEE International Conferenceon Ultra-Wideband (ICUWB2010: Proceedings - Volume 1, 2010, s. 1-4Konferansepaper, Oral presentation only (Fagfellevurdert)
    Abstract [en]

    This paper proposes how antenna polarization can be utilized to increase the maximum data rate in a multiple six-port receiver system. By utilizing data and carrier interleaving, the total information bandwidth increases and therefore the maximum data rate. Prototype antennas were manufactured and the measured results were later used in a simulation model with three channels for verification of the concept.

    Emneord
    Antennas, electromagnetic wave polarisation, radio receivers
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-77201 (URN)10.1109/ICUWB.2010.5614449 (DOI)978-1-4244-5306-1 (ISBN)978-1-4244-5305-4 (ISBN)
    Konferanse
    IEEE International Conference on Ultra-Wideband (ICUWB), 20-23 September, Nanjing, China
    Tilgjengelig fra: 2012-05-08 Laget: 2012-05-08 Sist oppdatert: 2019-06-17bibliografisk kontrollert
    8. Baseband complexity comparison of six-, five-, and four-port receivers
    Åpne denne publikasjonen i ny fane eller vindu >>Baseband complexity comparison of six-, five-, and four-port receivers
    Vise andre…
    2012 (engelsk)Inngår i: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 54, nr 6, s. 1502-1506Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The use of six-port correlators to implement six-port receivers has been intensively studied. The six-port receiver can also be modified to a five-port or a four-port receiver. However, the six-, five-, or four-port receiver solution requires different baseband processing to recover the baseband In-phase (I) and Quadrature-phase (Q) data. A unified mathematical model for the six-, five- and four-port receivers is presented in this article. Possible solutions to recover the baseband data are discussed and compared. The investigation shows that the six-port receiver has advantages over the five- and four-port receivers in terms of complexity when analog baseband processing is used. Simulations are conducted to verify the model and to estimate the error vector magnitude versus frequency; the simulation also shows that the six-port receiver operates over a wider bandwidth than the five- or four-port receiver.

    sted, utgiver, år, opplag, sider
    Wiley-Blackwell, 2012
    Emneord
    six-port receiver, five-port receiver, four-port receiver, baseband complexity
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-76606 (URN)10.1002/mop.26833 (DOI)000301715800045 ()
    Tilgjengelig fra: 2012-04-13 Laget: 2012-04-13 Sist oppdatert: 2019-06-17
    9. LO Leakage in Six-Port Modulators and Demodulators and its Suppression Techniques
    Åpne denne publikasjonen i ny fane eller vindu >>LO Leakage in Six-Port Modulators and Demodulators and its Suppression Techniques
    2012 (engelsk)Konferansepaper, Oral presentation only (Fagfellevurdert)
    Abstract [en]

    In a six-port demodulator utilizing diodes for power detection, impedance mismatch at the interface between the six-port correlator and diodes generates unwanted local oscillator (LO) leakage to the radio frequency (RF) port. A six-port modulator that uses variable reflection coefficients at specific ports to generate a modulated RF may also suffer from LO leakage if there is a static part in the reflection coefficient. It is known that LO leakage to the RF port not only generates unwanted emission of the LO signal, but also degrades the receiver system performance due to a dynamic dc offset and second-order non-linearity at the detected baseband signal. How this LO leakage appears to the RF port in six-port demodulators and modulators are analyzed. Two different approaches to suppress the LO leakage is then discussed: a) diode impedance matching and b) introduction of a λ/4 line on specific ports. The performance when λ/4 lines are used on specific ports is verified by measurement for both a demodulator and a modulator. The measurement shows high suppression of the LO leakage.

    sted, utgiver, år, opplag, sider
    IEEE, 2012
    Emneord
    Six-Port Correlator, Six-Port Receiver, LO Leakage, LO Suppression
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-77207 (URN)10.1109/MWSYM.2012.6258402 (DOI)978-1-4673-1086-4 (ISBN)978-1-4673-1085-7 (ISBN)
    Konferanse
    International Microwave Symposium, June 17-22, Montréal, Canada
    Tilgjengelig fra: 2012-05-08 Laget: 2012-05-08 Sist oppdatert: 2019-06-17bibliografisk kontrollert
  • 7463.
    Östh, Joakim
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Karlsson, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Serban, Adriana
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Gong, Shaofang
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    A Comparative Study of Single-Ended vs. Differential Six-Port Modulators for Wireless Communications2015Inngår i: IEEE Transactions on Circuits and Systems Part 1: Regular Papers, ISSN 1549-8328, E-ISSN 1558-0806, Vol. 62, nr 2, s. 564-570Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    If present, nonlinear effects in a six-port modulator cause distortion and degradation of the quality of the modulated output waveform. How nonlinear effects occur and their impact on system performance were derived in a mathematical model. The model shows that non-ideal performance of the passive six-port correlator is the main contributor to nonlinear distortion. Simulations and measurements on two manufactured six-port modulators were used to validate the theory and to give deeper insight on system performance. It is shown that by using a differentially signaled six-port modulator instead of a single-ended six-port modulator, better performance is achieved over a wide bandwidth. For an error vector magnitude of less than 10%, the relative bandwidth was measured to 12% for the single-ended but 30% for the differentially signaled modulator

  • 7464.
    Östlund, Per
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Stavåker, Kristian
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap, PELAB - Laboratoriet för programmeringsomgivningar. Linköpings universitet, Tekniska högskolan.
    Parallel Simulation of Equation-Based Models on CUDA-Enabled GPUs2010Inngår i: Proceedings of the 9th Workshop on Parallel/High-Performance Object-Oriented Scientific Computing POOSC '10, New York, USA: ACM , 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Our contributions with this work are methods and a prototype implementation for compiling and executing a limited set of equation-based mathematical models (written in the object-oriented equation-based modeling language Modelica) on CUDA-enabled GPUs. We look at methods of finding parallelism in Modelica models, that can be used on the massively parallel CUDA architecture. The methods have been implemented in a new back-end module of the OpenModelica compiler (an open-source Modelica compiler). This paper shows that it is possible to automatically generate simulation code for pure continuous-time models that can be reduced to an ordinary differential equation system without algebraic loops and where the initial values of all variables and parameters are known at compile time. It is possible to get some speedup compared with simulation on a single CPU core, a (approximated) relative speedup of 4.6 was for instance obtained for one model.

  • 7465.
    Östlund, Pierre
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Design, implementation och simulering av ett MAC-protokoll för mobila trådlösa sensornätverk2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Trådlösa sensornätverk byggs upp av trådlösa sensorer, som gemensamt arbetar för att lösa en viss uppgift. Ett exempel på en sådan uppgift kan vara insamling av pollennivåer i luften över en stor yta. Sensornoderna vidarebefordrar datan sinsemellan tills den når en datainsamlingsnod någonstans i nätverket där den sedan lagras och efterbehandlas. Generellt gäller att sensornoder är små, billiga, kommunicerar trådlöst och har en väldigt lång livslängd. Traditionellt sett har sen- sornoder också antagits vara statiska (stillastående), vilket medför begränsningar om noderna bärs av exempelvis människor eller monteras på fordon.

    I detta examensarbete presenteras matmac , ett mac-protokoll som designats för att hantera mobila noder i trådlösa sensornätverk. En referensimplementa- tion av matmac har implementerats i operativsystemet Contiki och utvärderats med varierande konfigurationsparametrar, rörelsehastigheter och dataintensitet i simulatorn Cooja. Resultatet från utvärderingen visar att mekanismerna för mo- bilitetshantering i matmac främjar sensornodernas förmåga att pålitligt överföra data trots att de är mobila. 

  • 7466.
    Östman, Christian
    et al.
    Linköpings universitet. Linköpings universitet, Institutionen för systemteknik.
    Forsberg, Anna
    Linköpings universitet. Linköpings universitet, Institutionen för systemteknik.
    Support System for Landing with an Autonomous Unmanned Aerial Vehicle2009Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    There are a number of ongoing projects developing autonomous vehicles, both helicopters and airplanes. The purpose of this thesis is to study a concept for calculating the height and attitude of a helicopter. The system will be active during landing. This thesis includes building an experimental setup and to develop algorithms and software.

    The basic idea is to illuminate the ground with a certain pattern and in our case we used laser pointers to create this pattern. The ground is then filmed and the images are processed to extract the pattern. This provides us with information about the height and attitude of the helicopter. Furthermore, the concept implies that no equipment on the ground is needed. With further development the sensor should be able to calculate the movement of the underlying surface relative to the helicopter. This is very important when landing on a moving surface, e.g. a ship at sea.

    To study the concept empirically an experimental setup was constructed. The setup provides us with the necessary information to evaluate how well the system could perform in reality. The setup is built with simple and cheap materials. In the setup an ordinary web camera and laser pointers that are avaliable for everyone have been used.

  • 7467.
    Östring, Måns
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Closed Loop Identification of the Physical Parameters of an Industrial Robot2001Inngår i: Proceedings of the Third Conference on Computer Science and Systems Engineering, 2001, s. 191-198Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    This paper discusses experimental identication of a flexible robot under strong feedback. Black-box models are compared with physically parameterized models. The parameters in the physical models and the blackbox models are identified from the input-output data using prediction error methods. We also investigate the importance of noise models when performing identication under strong feedback. The robot that we use is a commercial ABB robot, IRB 1400.

  • 7468.
    Östring, Måns
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Closed Loop Identification of the Physical Parameters of an Industrial Robot2001Inngår i: Proceedings of the 32nd International Symposium on Robotics, 2001Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper discusses experimental identication of a flexible robot under strong feedback. Black-box models are compared with physically parameterized models. The parameters in the physical models and the blackbox models are identified from the input-output data using prediction error methods. We also investigate the importance of noise models when performing identification under strong feedback. The robot that we use is a commercial ABB robot, IRB 1400.

  • 7469.
    Östring, Måns
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Closed Loop Identification of the Physical Parameters of an Industrial Robot2000Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper discusses experimental identication of a flexible robot under strong feedback. Black-box models are compared with physically parameterized models. The parameters in the physical models and the blackbox models are identified from the input-output data using prediction error methods. We also investigate the importance of noise models when performing identication under strong feedback. The robot that we use is a commercial ABB robot, IRB 1400.

  • 7470.
    Östring, Måns
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Identification, Diagnosis, and Control of a Flexible Robot Arm2002Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The most important factors in manufacturing are quality, cost, and productivity. The trend is towards lighter robots with increased mechanical flexibilities, and therefore there is a need to include the flexibilities in the robot models to obtain good performance of the robot. The core theme in this thesis is modeling and identification of the physical parameters of an ABB IRB 1400 industrial robot. The approximation made is that the robot arm can be described using a finite number of masses connected by springs and dampers. It has been found that a three-mass model gives a reasonably good description of the robot when moving around axis one. The physical parameters of this model are identified using off-line and on-line algorithms. The algorithms are based on prediction error methods. For the on-line identication the Matlab System Identifiation Toolbox is used. For the on-line identication the algorithm used is a modified version of a recursive prediction error method to cope with continuous time models. The models are then used in diagnosis and control. Two ways of doing diagnosis using on-line identification are investigated. Estimating some of the physical parameters of the robot arm recursively makes it possible to monitor important aspects of the system such as friction and load. LQG control of the flexible robot arm is also studied with the aim of good disturbance rejection. Aspects that have been studied are unstable regulators and the use of accelerometers.

  • 7471.
    Östring, Måns
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On Modeling, Fault Detection and Fault Isolation of Valve and Pipe System2000Rapport (Annet vitenskapelig)
    Abstract [en]

    Valve and pipe systems are used in many areas. Often there is redundancy in the system. If one valve breaks it may be possible to lead the gas (or fluid) another way. To do this automatically we have to be able to detect and isolate faults. In this report, we show a way to use discrete event dynamical system models for analyzing where to put sensors in a valve and pipe system.

  • 7472.
    Östring, Måns
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Svante
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Recursive Identification of Physical Parameters in a Flexible Robot Arm2002Rapport (Annet vitenskapelig)
    Abstract [en]

    Recursive identification of physically parameterized models of continuous time systems is considered. As an example a model of a single link flexible robot arm is considered. The aim of the identification is to generate on-line estimates of physical parameters that can be used for, e.g., diagnosis purposes. For evaluation the algorithm is applied to data from an industrial robot, and three important parameters are identified using only measurements of the motor angle.

  • 7473.
    Östring, Måns
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Svante
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Norrlöf, Mikael
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Closed-Loop Identification of an Industrial Robot Containing Flexibilities2001Rapport (Annet vitenskapelig)
    Abstract [en]

    Closed-loop identification of an industrial robot of the type ABB IRB 1400 is considered. Data are collected when the robot is subject to feedback control and moving around axis one. Both black-box and physically parameterized models are identified. A main purpose is to model the mechanical flexibilities. It is found that a model consisting of three-masses connected by springs and dampers gives a good description of the dynamics of the robot.

  • 7474.
    Östring, Måns
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Svante
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Norrlöf, Mikael
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Closed-Loop Identification of an Industrial Robot Containing Flexibilities2003Inngår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 11, nr 3, s. 291-300Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Closed-loop identification of an industrial robot of the type ABB IRB 1400 is considered. Data are collected when the robot is subject to feedback control and moving around axis one. Both black-box and physically parameterized models are identified. A main purpose is to model the mechanical flexibilities. It is found that a model consisting of three-masses connected by springs and dampers gives a good description of the dynamics of the robot.

  • 7475.
    Östring, Måns
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Tjärnström, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Norrlöf, Mikael
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Modeling of Industrial Robot for Identification, Monitoring and Control2002Inngår i: Proceedings of the 2002 International Symposium on Advanced Control of Industrial Processes, 2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we study the problem of a modeling, identifying, and monitoring an industrial robot. We start by showing how a robot can be modeled in increasing degree of accuracy using high end tools such as MathModelica. This model can be transformed semi-automatically into a minimal state-space form which in turn can be used for identification. Moreover, the physically connected equations can be identified recursively, making it possible to monitor critical parts of the robot. When attached to a well trimmed detection scheme this provides a big help for operators, who easily can track problems with the process.

  • 7476.
    Östring, Måns
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Tjärnström, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Norrlöf, Mikael
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Modeling of Industrial Robot for Identification, Monitoring and Control2002Rapport (Annet vitenskapelig)
    Abstract [en]

    In this paper we study the problem of a modeling, identifying, and monitoring an industrial robot. We start by showing how a robot can be modeled in increasing degree of accuracy using high end tools such as MathModelica. This model can be transformed semi-automatically into a minimal state-space form which in turn can be used for identification. Moreover, the physically connected equations can be identified recursively, making it possible to monitor critical parts of the robot. When attached to a well trimmed detection scheme this provides a big help for operators, who easily can track problems with the process.

  • 7477.
    Özdogan, Özgecan
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Massive MIMO With Spatially Correlated Rician Fading Channels2019Inngår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, nr 5, s. 3234-3250Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper considers multi-cell massive multiple-input multiple-output systems, where the channels are spatially correlated Rician fading. The channel model is composed of a deterministic line-of-sight path and a stochastic non-line-of-sight component describing a practical spatially correlated multipath environment. We derive the statistical properties of the minimum mean squared error (MMSE), element-wise MMSE, and least-square channel estimates for this model. Using these estimates for maximum ratio combining and precoding, rigorous closed-form uplink (UL) and downlink (DL) achievable spectral efficiency (SE) expressions are derived and analyzed. The asymptotic SE behavior, when using the different channel estimators, are also analyzed. The numerical results show that the SE is higher when using the MMSE estimator than that of the other estimators, and the performance gap increases with the number of antennas.

  • 7478.
    Özdogan, Özgecan
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Uplink Spectral Efficiency of Massive MIMO with Spatially Correlated Rician Fading2018Inngår i: 2018 IEEE 19TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC), IEEE , 2018, s. 216-220Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper considers the uplink (UL) of a multicell Massive MIMO (multiple-input multiple-output) system with spatially correlated Rician fading channels. The channel model is composed of a deterministic line-of-sight (LoS) path and a stochastic non-line-of-sight (NLoS) component describing a spatially correlated multipath environment. We derive the statistical properties of the minimum mean squared error (MMSE) and least-square (LS) channel estimates for this model. Using these estimates for maximum ratio (MR) combining, rigorous closed-form UL spectral efficiency (SE) expressions are derived. Numerical results show that the SE is higher when using the MMSE estimator than the LS estimator, and the performance gap increases with the number of antennas. Moreover, Rician fading provides higher achievable SEs than Rayleigh fading since the LoS path improves the sum SE.

  • 7479.
    Özdogan, Özgecan
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Zhang, Jiayi
    Beijing Jiaotong Univ, Peoples R China.
    Cell-Free Massive MIMO with Rician Fading: Estimation Schemes and Spectral Efficiency2018Inngår i: 2018 CONFERENCE RECORD OF 52ND ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS, AND COMPUTERS, IEEE , 2018, s. 975-979Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As the cell sizes in cellular networks shrink, the inter-cell interference becomes more of an issue. Instead of operating each cell autonomously, we can connect all the access points (APs) together to form a cell-free massive MIMO (multiple-input multiple-output) system that can alleviate interference by spatial processing. Previous studies have focused on Rayleigh fading channels, but in densely deployed systems, it is likely that some of the users will have line-of-sight (LoS) propagation to some of the APs. In this paper, we model this by arbitrarily distributed Rician fading channels. Two types of channel estimators are considered: a classical least-square (LS) estimator and a Bayesian minimum mean square error (MMSE) estimator. We derive closed-form spectral efficiency (SE) expressions for the uplink (UL) and downlink (DL) when using each of these estimators for maximum ratio (MR) processing. The performance difference is evaluated numerically to figure out under which conditions it is beneficial to know the channel statistics when estimating a channel.

  • 7480.
    Özkan, Emre
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Fritsche, Carsten
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Online EM algorithm for joint state and mixture measurement noise estimation2012Inngår i: 15th International Conference on Information Fusion (FUSION), 2012, IEEE , 2012, s. 1935-1940Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this study, we aim to estimate the unknown multi-modal measurement noise distribution of nonlinear state space models. The unknown noise distribution is modeled as a mixture of exponential family of distributions. We use the Expectation-Maximization (EM) method in order to jointly estimate the unknown parameters as well as the states. The online version of the EM algorithm is implemented by using particle filtering techniques. The resulting algorithm is a noise adaptive particle filter which is applicable to many sensor models having multi-modal noise distributions with unknown parameters.

  • 7481.
    Özkan, Emre
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Lindsten, Fredrik
    University of Cambridge, England.
    Fritsche, Carsten
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Recursive Maximum Likelihood Identification of Jump Markov Nonlinear Systems2015Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 63, nr 3, s. 754-765Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an online method for joint state and parameter estimation in jump Markov non-linear systems (JMNLS). State inference is enabled via the use of particle filters which makes the method applicable to a wide range of non-linear models. To exploit the inherent structure of JMNLS, we design a Rao-Blackwellized particle filter (RBPF) where the discrete mode is marginalized out analytically. This results in an efficient implementation of the algorithm and reduces the estimation error variance. The proposed RBPF is then used to compute, recursively in time, smoothed estimates of complete data sufficient statistics. Together with the online expectation maximization algorithm, this enables recursive identification of unknown model parameters including the transition probability matrix. The method is also applicable to online identification of jump Markov linear systems(JMLS). The performance of the method is illustrated in simulations and on a localization problem in wireless networks using real data.

  • 7482.
    Özkan, Emre
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Lundquist, Christian
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Bayesian Approach to Jointly Estimate Tire Radii and Vehicle Trajectory2011Inngår i: Proceedings of the International IEEE Conference on Intelligent Transportation Systems, Washington DC, USA: IEEE conference proceedings, 2011, s. 1-6Konferansepaper (Fagfellevurdert)
    Abstract [en]

    High-precision estimation of vehicle tire radii is considered, based on measurements on individual wheel speeds and absolute position from a global navigation satellite system (GNSS). The wheel speed measurements are subject to noise with time-varying covariance that depends mainly on the road surface. The novelty lies in a Bayesian approach to estimate online the time-varying radii and noise parameters using a marginalized particle filter, where no model approximations are needed such as in previously proposed algorithms based on the extended Kalman filter. Field tests show that the absolute radius can be estimated with millimeter accuracy, while the relative wheel radius on one axle is estimated with submillimeter accuracy.

  • 7483.
    Özkan, Emre
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Saha, Saikat
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Smidl, Vaclav
    Institute of Information Theory and Automation, Czech Repbulic.
    Non-Parametric Bayesian Measurement Noise Density Estimation in Non-Linear Filtering2011Inngår i: Acoustics, Speech and Signal Processing (ICASSP), 2011, IEEE , 2011, s. 5924-5927Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this study, we investigate online Bayesian estimation of the measurement noise density of a given state space model using particle filters and Dirichlet process mixtures. Dirichlet processes are widely used in statistics for nonparametric density estimation. In the proposed method, the unknown noise is modeled as a Gaussian mixture with unknown number of components. The joint estimation of the state and the noise density is done via particle filters. Furthermore, the number of components and the noise statistics are allowed to vary in time. An extension of the method for the estimation of time varying noise characteristics is also introduced.

  • 7484.
    Özkan, Emre
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Smidl, Vaclav
    Institute of Information Theory and Automation, Czech Republic.
    Saha, Saikat
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Lundquist, Christian
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Marginalized Adaptive Particle Filtering for Nonlinear Models with Unknown Time-Varying Noise Parameters2013Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 49, nr 6, s. 1566-1575Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Knowledge of the noise distribution is typically crucial for the state estimation of general state-space models. However, properties of the noise process are often unknown in the majority of practical applications. The distribution of the noise may also be non-stationary or state dependent and that prevents the use of off-line tuning methods. For linear Gaussian models, Adaptive Kalman filters (AKF) estimate unknown parameters in the noise distributions jointly with the state. For nonlinear models, we provide a Bayesian solution for the estimation of the noise distributions in the exponential family, leading to a marginalized adaptive particle filter (MAPF) where the noise parameters are updated using finite dimensional sufficient statistics for each particle. The time evolution model for the noise parameters is defined implicitly as a Kullback-Leibler norm constraint on the time variability, leading to an exponential forgetting mechanism operating on the sufficient statistics. Many existing methods are based on the standard approach of augmenting the state with the unknown variables and attempting to solve the resulting filtering problem. The MAPF is significantly more computationally efficient than a comparable particle filter that runs on the full augmented state. Further, the MAPF can handle sensor and actuator offsets as unknown means in the noise distributions, avoiding the standard approach of augmenting the state with such offsets. We illustrate the MAPF on first a standard example, and then on a tire radius estimation problem on real data.

  • 7485.
    Čirkić, Mirsad
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Efficient MIMO Detection Methods2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    For the past decades, the demand in transferring large amounts of data rapidly and reliably has been increasing drastically. One of the more promising techniques that can provide the desired performance is multiple-input multiple-output (MIMO) technology where multiple antennas are placed at both the transmitting and receiving side of the communication link. This performance potential is extremely high when the dimensions of the MIMO system are increased to an extreme (in the number of hundreds or thousands of antennas). One major implementation difficulty of the MIMO technology is the signal separation (detection) problem at the receiving side of the MIMO link, which holds for medium-size MIMO systems and even more so for large-size systems. This is due to the fact that the transmitted signals interfere with each other and that separating them can be very difficult if the MIMO channel conditions are not beneficial, i.e., the channel is not well-conditioned.

    The main problem of interest is to develop algorithms for practically feasible MIMO implementations without sacrificing the promising performance potential that such systems bring. These methods involve inevitably different levels of approximation. There are computationally cheap methods that come with low accuracy and there are computationally expensive methods that come with high accuracy. Some methods are more applicable in medium-size MIMO than in large-size MIMO and vice versa. Some simple methods for instance, which are typically inaccurate for medium-sized settings, can achieve optimal accuracy for certain large-sized settings that offer close-to-orthogonal spatial signatures. However, when the dimensions are overly increased, then even these (previously) simple methods become computationally burdensome. In different MIMO setups, the difficulty in detection shifts since methods with optimal accuracy are not the same. Therefore, devising one single algorithm which is well-suited for feasible MIMO implementations in all settings is not easy.

    This thesis addresses the general MIMO detection problem in two ways. One part treats a development of new and more efficient detection techniques for the different MIMO settings. The techniques that are proposed in this thesis demonstrate unprecedented performance in many relevant cases. The other part revolves around utilizing already proposed detection algorithms and their advantages versus disadvantages in an adaptive manner. For well-conditioned channels, low-complexity detection methods are often sufficiently accurate. In such cases, performing computationally very expensive optimal detection would be a waste of computational power. This said, for MIMO detection in a coded system, there is always a trade-off between performance and complexity. Intuitively, computational resources should be utilized more efficiently by performing optimal detection only when it is needed, and something simpler when it is not. However, it is not clear whether this is true or not. In trying to answer this, a general framework for adaptive computational-resource allocation to different (“simple” and “difficult”) detection problems is proposed. This general framework is applicable to any MIMO detector and scenario of choice, and it is exemplified using one particular detection method for which specific allocation techniques are developed and evaluated.

    Delarbeid
    1. Allocation of Computational Resources for Soft MIMO Detection
    Åpne denne publikasjonen i ny fane eller vindu >>Allocation of Computational Resources for Soft MIMO Detection
    2011 (engelsk)Inngår i: IEEE Journal of Selected Topics in Signal Processing, ISSN 1932-4553, Vol. 5, nr 8, s. 1451-1461Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    We consider soft MIMO detection for the case of block fading. That is, the transmitted codeword spans over several independent channel realizations and several instances of the detection problem must be solved for each such realization. We develop methods that adaptively allocate computational resources to the detection problems of each channel realization, under a total per-codeword complexity constraint. Our main results are a formulation of the problem as a mathematical optimization problem with a well-defined objective function and constraints, and algorithms that solve this optimization problem efficiently computationally.

    sted, utgiver, år, opplag, sider
    IEEE conference proceedings, 2011
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-69612 (URN)10.1109/JSTSP.2011.2162719 (DOI)000297348500006 ()
    Merknad
    ©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Mirsad Čirkić, Daniel Persson and Erik G. Larsson, Allocation of Computational Resources for Soft MIMO Detection, 2011, accepted IEEE Journal of Selected Topics in Signal Processing Tilgjengelig fra: 2011-07-06 Laget: 2011-07-06 Sist oppdatert: 2016-08-31
    2. Approximating the LLR Distribution for a Class of Soft-Output MIMO Detectors
    Åpne denne publikasjonen i ny fane eller vindu >>Approximating the LLR Distribution for a Class of Soft-Output MIMO Detectors
    2012 (engelsk)Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, nr 12, s. 6421-6434Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    We present approximations of the LLR distribution for a class of fixed-complexity soft-output MIMO detectors, such as the optimal soft detector and the soft-output via partial marginalization detector. More specifically, in a MIMO AWGN setting, we approximate the LLR distribution conditioned on the transmitted signal and the channel matrix with a Gaussian mixture model (GMM). Our main results consist of an analytical expression of the GMM model (including the number of modes and their corresponding parameters) and a proof that, in the limit of high SNR, this LLR distribution converges in probability towards a unique Gaussian distribution.

    sted, utgiver, år, opplag, sider
    Institute of Electrical and Electronics Engineers (IEEE), 2012
    Emneord
    Fixed-complexity sphere-decoder; Gaussian mixture model; LLR distribution; MIMO detection; partial marginalization
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-87205 (URN)10.1109/TSP.2012.2217336 (DOI)000311805000024 ()
    Merknad

    On the defence date of the Licentiate Thesis the status of this article was Manuscript and the title was Approximating the LLR Distribution for the Optimal and Partial Marginalization MIMO Detectors.

    Tilgjengelig fra: 2013-01-14 Laget: 2013-01-14 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    3. SUMIS: Near-Optimal Soft-In Soft-Out MIMO Detection with Low and Fixed Complexity
    Åpne denne publikasjonen i ny fane eller vindu >>SUMIS: Near-Optimal Soft-In Soft-Out MIMO Detection with Low and Fixed Complexity
    2014 (engelsk)Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 62, nr 12, s. 3084-3097Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The fundamental problem of interest here is soft-input soft-output multiple-input multiple-output (MIMO) detection. We propose a method, referred to as subspace marginalization with interference suppression (SUMIS), that yields unprecedented performance at low and fixed (deterministic) complexity. Our method provides a well-defined tradeoff between computational complexity and performance. Apart from an initial sorting step consisting of selecting channel-matrix columns, the algorithm involves no searching nor algorithmic branching; hence the algorithm has a completely predictable run-time and allows for a highly parallel implementation. We numerically assess the performance of SUMIS in different practical settings: full/partial channel state information, sequential/iterative decoding, and low/high rate outer codes. We also comment on how the SUMIS method performs in systems with a large number of transmit antennas.

    sted, utgiver, år, opplag, sider
    IEEE Signal Processing Society, 2014
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-103671 (URN)10.1109/TSP.2014.2303945 (DOI)000338122400005 ()
    Tilgjengelig fra: 2014-01-22 Laget: 2014-01-22 Sist oppdatert: 2017-12-06
    4. On the Complexity of Very Large Multi-User MIMO Detection
    Åpne denne publikasjonen i ny fane eller vindu >>On the Complexity of Very Large Multi-User MIMO Detection
    2014 (engelsk)Inngår i: 2014 IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), IEEE, IEEE Press, 2014, s. 55-59Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    This work discusses efficient techniques for detection in large-size multi-user multiple-input multiple-output (MIMO) systems that are highly overdetermined. We exemplify the application of conjugate gradient methods in the setup of our interest and compare its performance with respect to methods based on the Neumann series expansion. We bring to light some important insights on the performance versus complexity tradeoffs that have not been uplifted before.

    sted, utgiver, år, opplag, sider
    IEEE Press, 2014
    Serie
    IEEE International Workshop on Signal Processing Advances in Wireless Communications, ISSN 2325-3789
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-103672 (URN)10.1109/SPAWC.2014.6941316 (DOI)000348859000012 ()978-1-4799-4903-8 (ISBN)
    Konferanse
    IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
    Tilgjengelig fra: 2014-01-22 Laget: 2014-01-22 Sist oppdatert: 2016-09-13bibliografisk kontrollert
  • 7486.
    Čirkić, Mirsad
    Linköpings universitet, Institutionen för systemteknik.
    Modular General-Purpose Data Filtering for Tracking2008Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In nearly allmodern tracking systems, signal processing is an important part with state estimation as the fundamental component. To evaluate and to reassess different tracking systems in an affordable way, simulations that are in accordance with reality are largely used. Simulation software that is composed of many different simulating modules, such as high level architecture (HLA) standardized software, is capable of simulating very realistic data and scenarios.

    A modular and general-purpose state estimation functionality for filtering provides a profound basis for simulating most modern tracking systems, which in this thesis work is precisely what is created and implemented in an HLA-framework. Some of the most widely used estimators, the iterated Schmidt extended Kalman filter, the scaled unscented Kalman filter, and the particle filter, are chosen to form a toolbox of such functionality. An indeed expandable toolbox that offers both unique and general features of each respective filter is designed and implemented, which can be utilized in not only tracking applications but in any application that is in need of fundamental state estimation. In order to prepare the user to make full use of this toolbox, the filters’ methods are described thoroughly, some of which are modified with adjustments that have been discovered in the process.

    Furthermore, to utilize these filters easily for the sake of user-friendliness, a linear algebraic shell is created, which has very straight-forward matrix handling and uses BOOST UBLAS as the underlying numerical library. It is used for the implementation of the filters in C++, which provides a very independent and portable code.

  • 7487.
    Čirkić, Mirsad
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Optimization of Computational Resources for MIMO Detection2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    For the past decades, the demand in transferring large amounts of data rapidly and reliably has been increasing drastically. One of the more promising techniques that can provide the desired performance is the multiple-input multiple-output (MIMO) technology where multiple antennas are placed at both the transmitting and receiving side of the communication link. One major implementation difficulty of the MIMO technology is the signal separation (detection) problem at the receiving side of the MIMO link. This is due to the fact that the transmitted signals interfere with each other and that separating them can be very difficult if the MIMO channel conditions are not beneficial, i.e., the channel is not well-conditioned.

    For well-conditioned channels, low-complexity detection methods are often sufficiently accurate. In such cases, performing computationally very expensive optimal detection would be a waste of computational power. This said, for MIMO detection in a coded system, there is always a trade-off between performance and complexity. The fundamental question is, can we save computational resources by performing optimal detection only when it is needed, and something simpler when it is not? This is the question that this thesis aims to answer. In doing so, we present a general framework for adaptively allocating computational resources to different (“simple” and“difficult”) detection problems. This general framework is applicable to any MIMO detector and scenario of choice, and it is exemplified using one particular detection method for which specific allocation techniques are developed and evaluated.

    Delarbeid
    1. Allocation of Computational Resources for Soft MIMO Detection
    Åpne denne publikasjonen i ny fane eller vindu >>Allocation of Computational Resources for Soft MIMO Detection
    2011 (engelsk)Inngår i: IEEE Journal of Selected Topics in Signal Processing, ISSN 1932-4553, Vol. 5, nr 8, s. 1451-1461Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    We consider soft MIMO detection for the case of block fading. That is, the transmitted codeword spans over several independent channel realizations and several instances of the detection problem must be solved for each such realization. We develop methods that adaptively allocate computational resources to the detection problems of each channel realization, under a total per-codeword complexity constraint. Our main results are a formulation of the problem as a mathematical optimization problem with a well-defined objective function and constraints, and algorithms that solve this optimization problem efficiently computationally.

    sted, utgiver, år, opplag, sider
    IEEE conference proceedings, 2011
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-69612 (URN)10.1109/JSTSP.2011.2162719 (DOI)000297348500006 ()
    Merknad
    ©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Mirsad Čirkić, Daniel Persson and Erik G. Larsson, Allocation of Computational Resources for Soft MIMO Detection, 2011, accepted IEEE Journal of Selected Topics in Signal Processing Tilgjengelig fra: 2011-07-06 Laget: 2011-07-06 Sist oppdatert: 2016-08-31
    2. Approximating the LLR Distribution for a Class of Soft-Output MIMO Detectors
    Åpne denne publikasjonen i ny fane eller vindu >>Approximating the LLR Distribution for a Class of Soft-Output MIMO Detectors
    2012 (engelsk)Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, nr 12, s. 6421-6434Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    We present approximations of the LLR distribution for a class of fixed-complexity soft-output MIMO detectors, such as the optimal soft detector and the soft-output via partial marginalization detector. More specifically, in a MIMO AWGN setting, we approximate the LLR distribution conditioned on the transmitted signal and the channel matrix with a Gaussian mixture model (GMM). Our main results consist of an analytical expression of the GMM model (including the number of modes and their corresponding parameters) and a proof that, in the limit of high SNR, this LLR distribution converges in probability towards a unique Gaussian distribution.

    sted, utgiver, år, opplag, sider
    Institute of Electrical and Electronics Engineers (IEEE), 2012
    Emneord
    Fixed-complexity sphere-decoder; Gaussian mixture model; LLR distribution; MIMO detection; partial marginalization
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-87205 (URN)10.1109/TSP.2012.2217336 (DOI)000311805000024 ()
    Merknad

    On the defence date of the Licentiate Thesis the status of this article was Manuscript and the title was Approximating the LLR Distribution for the Optimal and Partial Marginalization MIMO Detectors.

    Tilgjengelig fra: 2013-01-14 Laget: 2013-01-14 Sist oppdatert: 2017-12-06bibliografisk kontrollert
  • 7488.
    Čirkić, Mirsad
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Near-Optimal Soft-Output Fixed-Complexity MIMO Detection via Subspace Marginalization and Interference Suppression2012Inngår i: 2012 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING (ICASSP), IEEE Signal Processing Society, 2012, , s. 4s. 2805-2808Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The fundamental problem of our interest here is soft MIMO detection. We propose a method that yields excellent performance, atlow and at fixed (deterministic) complexity. Our method provides a well-defined tradeoff between computational complexity and performance. Apart from an initial step consisting of selecting columns,the algorithm involves no searching nor algorithmic branching; hence the algorithm has a completely predictable run-time, and it is readily and massively parallelizable.

  • 7489.
    Čirkić, Mirsad
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    On the Complexity of Very Large Multi-User MIMO Detection2014Inngår i: 2014 IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), IEEE, IEEE Press, 2014, s. 55-59Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This work discusses efficient techniques for detection in large-size multi-user multiple-input multiple-output (MIMO) systems that are highly overdetermined. We exemplify the application of conjugate gradient methods in the setup of our interest and compare its performance with respect to methods based on the Neumann series expansion. We bring to light some important insights on the performance versus complexity tradeoffs that have not been uplifted before.

  • 7490.
    Čirkić, Mirsad
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    SUMIS: Near-Optimal Soft-In Soft-Out MIMO Detection with Low and Fixed Complexity2014Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 62, nr 12, s. 3084-3097Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The fundamental problem of interest here is soft-input soft-output multiple-input multiple-output (MIMO) detection. We propose a method, referred to as subspace marginalization with interference suppression (SUMIS), that yields unprecedented performance at low and fixed (deterministic) complexity. Our method provides a well-defined tradeoff between computational complexity and performance. Apart from an initial sorting step consisting of selecting channel-matrix columns, the algorithm involves no searching nor algorithmic branching; hence the algorithm has a completely predictable run-time and allows for a highly parallel implementation. We numerically assess the performance of SUMIS in different practical settings: full/partial channel state information, sequential/iterative decoding, and low/high rate outer codes. We also comment on how the SUMIS method performs in systems with a large number of transmit antennas.

  • 7491.
    Čirkić, Mirsad
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Persson, Daniel
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Allocation of Computational Resources for Soft MIMO Detection2011Inngår i: IEEE Journal of Selected Topics in Signal Processing, ISSN 1932-4553, Vol. 5, nr 8, s. 1451-1461Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider soft MIMO detection for the case of block fading. That is, the transmitted codeword spans over several independent channel realizations and several instances of the detection problem must be solved for each such realization. We develop methods that adaptively allocate computational resources to the detection problems of each channel realization, under a total per-codeword complexity constraint. Our main results are a formulation of the problem as a mathematical optimization problem with a well-defined objective function and constraints, and algorithms that solve this optimization problem efficiently computationally.

  • 7492.
    Šmídl, Václav
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Forgetting in Marginalized Particle Filtering and its Relation to Forward Smoothing2011Rapport (Annet vitenskapelig)
    Abstract [en]

    The problem of degeneracy in marginalized particle filtering is addressed. In particular, we note that the degeneracy is caused by loss of entropy of the posterior distribution and design maximum entropy estimates to prevent this. The main technique used in this report is known as forgetting. Itis shown that it can be used to suppress the problem with degeneracy, however, it is not a proper cure for the problem of stationary parameters. The problem of marginal-marginalized particle filter for sufficient statistics is also studied. The resulting algorithm is found to have remarkable similarities with the algorithm known as forward smoothing.

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