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  • 301.
    Andersson, Peter
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Test Case for Adaptive Control: Car Steering1981Ingår i: Proceedings of the 1981 IFAC Symposium on Theory and Applications of Digital Control, 1981Konferensbidrag (Refereegranskat)
  • 302.
    Andersson, Peter
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Test Case for Adaptive Control: Car Steering1981Rapport (Övrigt vetenskapligt)
  • 303.
    Andersson, Pontus
    Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Visuell processreglering2007Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats
    Abstract [sv]

    Examensarbetet handlar om att ta fram en processmodell för nivåreglering och det innehåller flera utmaningar. Vätskesystemets dynamik och balans måste beaktas likväl som lämpliga reglermetoder samt modellens utseende. I den här rapporten behandlas hela händelseförloppet från initialskedet till en färdig produkt redo att visas för en publik. Läsaren får möjlighet att närmare granska de komponenter som modellen är uppbyggd av, ta del av programmeringsarbetet och de omfattande test av modellen som utförts. Flera teknikområden belyses men fokus riktas särskilt på ABB:s styrsystem AC800M/800xA, fältbussteknik och reglerstrategier. PID-regulatorn har under arbetet spelat en stor roll och reglerstrategier som innefattar bl.a. framkoppling och kaskadkoppling analyseras och diskuteras. För att bedöma skillnader i val av reglermetod används grafer från praktiska försök. Rapportens upplägg med flertalet illustrationer och den genomgripande tekniska dokumentationen hjälper läsaren att förstå modellens funktion och uppbyggnad.

  • 304.
    Andersson, Rickard
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem.
    Algorithm for Handoff in VDL mode 42010Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    VDL mode 4 is a digital data link operating in the VHF band, its mainly use is for the aviation industry.VDL4 can as an example provide with positioning data, speed information of aircrafts or vehicles equipped with a VDL4 transponder. A connection between the groundsystem and the airborne system is called a point to point connection, which can be used for various applications. This data link needs to be transferred between groundstations during flights in order maintain the connection, which is called handoff.

    The handoff process needs to be quick enough to not drop the link and at the same time a low rate of handoffs is desirable. The data link is regarded as a narrow resource and link management data for handoff is considered as overhead.

    This thesis studies how to make the handoff procedure optimal with respect to involved aspects. Previous research of handoff algorithms and models of the VHF-channel are treated. Standardized parameters and procedures in VDL4 and are explored in order to find an optimal solution for the handoff procedure in VDL4.

    The studied topics are analyzed and it is concluded to suggest an algorithm based on an adaptive hysteresis including signal quality and positioning data provided in VDL4. Standardized parameters which could be useful in the handoff procedure are commented, since the VDL4 standards are under development.

  • 305.
    Andersson, Rikard
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Emberg, Johan
    Linköpings universitet, Institutionen för datavetenskap.
    Hazell, Sofie
    Linköpings universitet, Institutionen för datavetenskap.
    Laestander, Hjalmar
    Linköpings universitet, Institutionen för datavetenskap.
    Norberg, Gustaf
    Linköpings universitet, Institutionen för datavetenskap.
    Elmfeldt Rönnmark, Maximilian
    Linköpings universitet, Institutionen för datavetenskap.
    Buciuto Sundelin, Bruno
    Linköpings universitet, Institutionen för datavetenskap.
    Törngren, Erik
    Linköpings universitet, Institutionen för datavetenskap.
    Heat n' Eat: Utvecklingen av en användbar e-butik med fokus på navigerbarhet2017Självständigt arbete på grundnivå (kandidatexamen), 12 poäng / 18 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Studenter idag har brist på både tid och pengar. Samtidigt ökar e-handeln och specifikt matförsäljningen över internet. Rapporten har som avsikt att undersöka möjligheterna för en tjänst, i form av en webbapplikation, som erbjuder studenter högkvalitativ mat inom deras budget på ett enkelt sätt. Via en marknadsundersökning på Campus Valla uttryckte studenter avsaknad av en sådan tjänst. Studien genomfördes genom att ta fram teori rörande användbarhet och navigerbarhet. Studenter som grupp har ofta ont om tid och är vana vid att få snabb och tydlig information vilket god navigerbarhet säkerställer. Efter teoristudien genomfördes användartester på målgruppen. Som ett resultat utvecklades webbapplikationen Heat n’ Eat. För att uppnå god navigerbarhet blev utformningen en simpel struktur med produkterna i fokus. Ett avslutande användartest visade att webbapplikationen kan anses vara användbar med fokus på navigerbarhet.

  • 306.
    Andersson, Robby
    Linköpings universitet, Institutionen för systemteknik.
    FPGA design of a controller for a CAN controller.2003Självständigt arbete på grundnivå (yrkesexamen)Studentuppsats
    Abstract [en]

    This diploma work describes how an FPGA is designed to control a CAN controller. It describes the different tools used when working with Actel’s design tools and the sequence of work applied. It gives a short overview of a multiplexer, the CAN bus, an analog/digital-converter and some more information on the actual FPGA. It also brings up the design process of the FPGA, planning, coding, simulating, testing and finally programming the FPGA. The different parts implemented in the FPGA are a shift-register and two state- machines that are connected with each other. They work together to control the SJA1000 CAN controller made by Philips. They also receive data from the analog/digital-converter that they forward onwards to the CAN controller that forward the data on the CAN bus.

  • 307.
    Andersson, Samuel
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Ekberg, Björn
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Prestandaoptimering av spelet Go Supernova2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Som underlag för den här rapporten använder vi oss av vårtspel Go Supernova. Det är skrivet i Java med hjälp avramverket LibGDX. Vi har undersökt hur man kan optimeraspelet för att kunna hantera så många objekt som möjligt menändå hålla ett bra spelflöde utan att förstöra den vision vihade när vi skapade spelet från första början. Vi har kommitfram till att ljusmotorn box2dlights använder sig av mycketprocessorkraft och användningen av den behövde justeras föratt tillfredsställa våra krav. Vi kommer även att tala omdesignval av spelets interna delar som gjorde att vi kundeundvika prestandaförluster.

  • 308.
    Andersson, Stefan
    Linköpings universitet, Institutionen för systemteknik, Elektroniska komponenter. Linköpings universitet, Tekniska högskolan.
    Multiband LNA Design and RF-Sampling Front-Ends for Flexible Wireless Receivers2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The wireless market is developing very fast today with a steadily increasing number of users all around the world. An increasing number of users and the constant need for higher and higher data rates have led to an increasing number of emerging wireless communication standards. As a result there is a huge demand for flexible and low-cost radio architectures for portable applications. Moving towards multistandard radio, a high level of integration becomes a necessity and can only be accomplished by new improved radio architectures and full utilization of technology scaling. Modern nanometer CMOS technologies have the required performance for making high-performance RF circuits together with advanced digital signal processing. This is necessary for the development of low-cost highly integrated multistandard radios. The ultimate solution for the future is a software-defined radio, where a single hardware is used that can be reconfigured by software to handle any standard. Direct analog-to-digital conversion could be used for that purpose, but is not yet feasible due to the extremely tough requirements that put on the analog-to-digital converter (ADC). Meanwhile, the goal is to create radios that are as flexible as possible with today’s technology. The key to success is to have an RF front-end architecture that is flexible enough without putting too tough requirements on the ADC.

    One of the key components in such a radio front-end is a multiband multistandard low-noise amplifier (LNA). The LNA must be capable of handling several carrier frequencies within a large bandwidth. Therefore it is not possible to optimize the circuit performance for just one frequency band as can be done for a single application LNA. Two different circuit topologies that are suitable for multiband multistandard LNAs have been investigated, implemented, and measured. Those two LNA topologies are: (i) wideband LNAs that cover all the frequency bands of interest (ii) tunable narrowband LNAs that are tunable over a wide range of frequency bands.

    Before analog-to-digital conversion the RF signal has to be downconverted to a frequency manageable by the analog-to-digital converter. Recently the concept of direct sampling of the RF signal and discrete-time signal processing before analog-to-digital conversion has drawn a lot of attention. Today’s CMOS technologies demonstrate very high speeds, making the RF-sampling technique appealing in a context of multistandard operation at GHz frequencies. In this thesis the concept of RF sampling and decimation is used to implement a flexible RF front-end, where the RF signal is sampled and downconverted to baseband frequency. A discrete-time switched-capacitor filter is used for filtering and decimation in order to decrease the sample rate from a value close to the carrier frequency to a value suitable for analog-to-digital conversion. To demonstrate the feasibility of this approach an RF-sampling front-end primarily intended for WLAN has been implemented in a 0.13 μm CMOS process.

    Delarbeten
    1. A Tuned, Inductorless, Recursive Filter LNA in CMOS
    Öppna denna publikation i ny flik eller fönster >>A Tuned, Inductorless, Recursive Filter LNA in CMOS
    2002 (Engelska)Ingår i: Proceedings of the European Solid-State Circuit Conference (ESSCIRC), Florens, Italy, September, 2002, s. 351-354Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    An active recursive filter approach is proposed for the implementation of an inductorless, tuned LNA in CMOS. Such an LNA was designed and fabricated ina 0.8 μm CMOS process. In simulation, the feasibility of this type of LNA was demonstrated, and reasonably good performance was obtained. The fabricated device shows a center frequency tuning range from 250 MHz to 975 MHz. Gain and Q value are tunable in a wide range. The LNA exhibits an input referred 1 dB compression point of -31 dB m and a noise figure of approximately 3 dB measured at 900 MHz center frequency.

    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14084 (URN)
    Konferens
    28th European Solid-State Circuit Conference (ESSCIRC). Firenze, Italy, September 24-26, 2002.
    Tillgänglig från: 2006-10-16 Skapad: 2006-10-16 Senast uppdaterad: 2013-10-31
    2. An Active Recursive RF Filter in 0.35 μm BiCMOS
    Öppna denna publikation i ny flik eller fönster >>An Active Recursive RF Filter in 0.35 μm BiCMOS
    2005 (Engelska)Ingår i: Journal of Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, Vol. 44, nr 3, s. 213-218Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    An active recursive filter approach is proposed for the implementaion of an inductorless, tuneable RF filter in BiCMOS. A test circuit was designed and manufactured in a 0.35 μm SiGe BiCMOS technology. In simulations, the feasibility of this type of filter was demonstrated and reasonably good performance was obtained. The simulations show a center frequency tuning range from 6 to 9.4 GHz and a noise figure of 8.8 to 10.4 dB depending on center frequency. Gain and Q-value are tunable in a wide range. Simulated IIP-3 and 1-dB compression point is −26 and −34 dBm respectively, simulated at the center frequency 8.5 GHz and with 15 dB gain. Measurements on the fabricated device shows a center frequency tuning range from 6.6 to 10 GHz, i.e. slightly higher center frequencies were measured than the simulated.

    Nyckelord
    active filter, tuneable recursive filter for multicarrier systems, inductorless RF filter, tuneable gain and Q
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14085 (URN)10.1007/s10470-005-3002-2 (DOI)
    Tillgänglig från: 2006-10-16 Skapad: 2006-10-16 Senast uppdaterad: 2013-10-31
    3. A 750 MHz to 3 GHz Tunable Narrowband Low-Noise Amplifier
    Öppna denna publikation i ny flik eller fönster >>A 750 MHz to 3 GHz Tunable Narrowband Low-Noise Amplifier
    2005 (Engelska)Ingår i: Proceedings of the Norchip 2005 Conference, Oulu, Finland, 2005, s. 8-11Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    An active recursive filter approach is proposed for the implementation of an inductorless, tunable LNA in CMOS. A test circuit was designed and manufactured in a 0.18 μm CMOS technology. The feasibility of this type of LNA was demonstrated in both simulations and measurements and reasonably good performance was obtained. The measurements show a center frequency tuning range from 0.75-3 GHz and a minimum noise figure of 4.8 dB. Gain and Q value are also tunable in a wide range. Measured IIP-3 and 1-dB compression point is -24 dBm and -29.5 dBm respectively, measured at the center frequency 1.7 GHz and with 21 dB gain.

    Nyckelord
    CMOS integrated circuits, UHF amplifiers, active filters, circuit tuning, integrated circuit design, low noise amplifiers, recursive filters, CMOS technology, active recursive filter, inductorless low-noise amplifier, tunable narrowband low-noise amplifier
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14086 (URN)10.1109/NORCHP.2005.1596976 (DOI)
    Tillgänglig från: 2006-10-16 Skapad: 2006-10-16
    4. Wideband LNA for a Multistandard Wireless Receiver in 0.18 μm CMOS
    Öppna denna publikation i ny flik eller fönster >>Wideband LNA for a Multistandard Wireless Receiver in 0.18 μm CMOS
    2003 (Engelska)Ingår i: Proceedings of the 29th European Solid-State Circuits Conference, 2003. ESSCIRC '03, 2003, s. 655-658Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    A differential wideband LNA for a multistandard receiver has been designed and implemented in 0.18μm CMOS. The circuit topology is a two-stage amplifier with active feedback. The input stage is a common-source stage with a common-drain stage in the feedback loop for impedance matching. Bandwidth enhancement with inductive shunt-peaking is used for maximizing the bandwidth. Measurements on the fabricated device show a power gain of 13.1 dB and a 3-dB bandwidth of nearly 7 GHz together with an IIP3 and a 1-dB compression point of -4.7 dBm and -15.2 dBm respectively. The measured noise figures are 3.3 dB at 1 GHz and 5.5 dB at 6 GHz. Reported LNAs with similar performance are usually implemented with bipolar transistors or MESFETs.

    Nyckelord
    CMOS integrated circuits, integrated circuit design, radio receivers, wideband amplifiers
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14087 (URN)10.1109/ESSCIRC.2003.1257220 (DOI)0-7803-7995-0 (ISBN)
    Konferens
    29th European Solid-State Circuits Conference, 2003. Estoril, Portugal, September 16-18.
    Tillgänglig från: 2006-10-16 Skapad: 2006-10-16 Senast uppdaterad: 2013-10-31
    5. Wideband LNA for aMultistandard RF-Sampling Front-End in 0.13 μm CMOS
    Öppna denna publikation i ny flik eller fönster >>Wideband LNA for aMultistandard RF-Sampling Front-End in 0.13 μm CMOS
    (Engelska)Manuskript (Övrigt vetenskapligt)
    Abstract [en]

    The pad pitch of modern RF ICs is in order of few tens of micrometers. Connecting the large number of high speed I/Os to outside world with good signal fidelity and low cost is extremely challenging. To cope with this requirement, we need reflection-free transmission lines from on-chip pad to on-board SMA connectors. Such a transmission line is very hard to design due to the difference in on-chip and on-board feature size and the requirement for extremely large bandwidth. In this paper, we propose the use of narrow tracks close to chip and wide tracks away from the chip. This narrow to wide transition in width results in impedance discontinuity. A step change in substrate thickness is utilized to cancel the effect of the width discontinuity, thus achieving a reflection-free microstrip. To verify the concept several microstrips were designed on multilayer FR4 PCB without any additional manufacturing steps. The TDR measurements reveal that impedance variation is less then 3Ω for 50Ω microstrip when the width changes from 165μm to 940μm and substrate thickness changes from 100μm to 500μm. The Sparameter measurement on same microstrip shows S11 better then -9dB for the frequency range 1-6GHz

    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14088 (URN)
    Tillgänglig från: 2006-10-16 Skapad: 2006-10-16 Senast uppdaterad: 2018-10-08
    6. Channel length as a design parameter for low noise wideband LNAs in deep submicron CMOS technologies
    Öppna denna publikation i ny flik eller fönster >>Channel length as a design parameter for low noise wideband LNAs in deep submicron CMOS technologies
    2004 (Engelska)Ingår i: Proceedings of the Norchip 2004 Conference, Oslo, Norway, November, 2004, s. 123-126Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    In this paper, measurements of drain thermal noise for three NMOS devices with different channel lengths was carried out. The three NMOS devices were all implemented in a 0.18 μm CMOS technology, with channel lengths 0.18. 0.36, and 0.72 μm, respectively. The result was then compared with simulated data using the BSIM3- model and parameters provided by the vendor Large discrepancies between measurements and simulations were observed. This work was done in order to understand how to utilize transistor length as a design parameter to achieve optimal noise gures for wideband LNAs in deep submicron technologies.

    Nyckelord
    CMOS, wideband LNAs
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14089 (URN)10.1109/NORCHP.2004.1423838 (DOI)0-7803-8510-1 (ISBN)
    Tillgänglig från: 2006-10-16 Skapad: 2006-10-16 Senast uppdaterad: 2013-10-31
    7. SC Filter for RF Down Conversion with Wideband Image Rejection
    Öppna denna publikation i ny flik eller fönster >>SC Filter for RF Down Conversion with Wideband Image Rejection
    2006 (Engelska)Ingår i: Proceedings of the ISCAS 2006 conference, Kos, Greece, 2006, s. 3542-3545Konferensbidrag, Publicerat paper (Refereegranskat)
    Nyckelord
    SF filter, RF downconversion, RF sampling
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14090 (URN)
    Tillgänglig från: 2006-10-16 Skapad: 2006-10-16 Senast uppdaterad: 2009-04-24
    8. SC Filter for RF Sampling and Downconversion with Wideband Image Rejection
    Öppna denna publikation i ny flik eller fönster >>SC Filter for RF Sampling and Downconversion with Wideband Image Rejection
    2006 (Engelska)Ingår i: Journal of Analog Integrated Circuits and Signal Processing by Springer, special issue: MIXDES, ISSN 0925-1030, Vol. 49, nr 2, s. 115-122Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this paper we present an SC filter for RF downconversion using the direct RF sampling and decimation technique. The circuit architecture is generic and it features high image rejection for wideband signals and good linearity. An SC implementation in 0.13μm CMOS suitable for an RF of 2.4 GHz and 20 MHz signal bandwidth is presented as a demonstrator. Simulation results obtained using Cadence Spectre simulation tools are included.

    Nyckelord
    RF sampling, Decimation filter, SC filter, Wideband image rejection
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14091 (URN)10.1007/s10470-006-7833-2 (DOI)
    Tillgänglig från: 2006-10-16 Skapad: 2006-10-16
    9. Noise Analysis and Noise Estimation of an RF-Sampling Front-End using an SC Decimation Filter
    Öppna denna publikation i ny flik eller fönster >>Noise Analysis and Noise Estimation of an RF-Sampling Front-End using an SC Decimation Filter
    2006 (Engelska)Ingår i: Proceedings of the MIXDES 2006 Conference, Gdynia, Poland, 2006, s. 343-348Konferensbidrag, Publicerat paper (Refereegranskat)
    Nyckelord
    RF sampling, decimation, thermal- and 1/f-noise, SC filter
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14092 (URN)
    Tillgänglig från: 2006-10-16 Skapad: 2006-10-16 Senast uppdaterad: 2009-04-24
    10. Multiband Direct RF-Sampling Receiver Front-End for WLAN in 0.13 μm CMOS
    Öppna denna publikation i ny flik eller fönster >>Multiband Direct RF-Sampling Receiver Front-End for WLAN in 0.13 μm CMOS
    (Engelska)Manuskript (Övrigt vetenskapligt)
    Abstract [en]

    In this paper a flexible RF-sampling front-end primarily intended for WLAN operating in the 2.4 GHz and 5- 6 GHz bands is presented. The circuit is implemented in a 0.13 mum CMOS process with certain built-in test features. It consists of a wideband LNA and a SC discrete-time decimation filter used as a sampling IQ down-converter. The architecture is generic and scalable in frequency and it can operate at a sampling frequency up to 3 GHz and RF carrier up to 6 GHz. The decimation factor is 8 or 16 rendering the following A/D conversion feasible. The frequency response, linearity, and NF of the whole front-end have been measured. At the power consumption of 176 mW the circuit achieves specs that are satisfactory for WLAN applications.

    Identifikatorer
    urn:nbn:se:liu:diva-14093 (URN)10.1109/ECCTD.2007.4529563 (DOI)
    Tillgänglig från: 2006-10-16 Skapad: 2006-10-16 Senast uppdaterad: 2014-08-19
  • 309.
    Andersson, Sören
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Asymptotic Analysis of Subspace Methods for Beamspace Direction-of-Arrival Estimation using Large Arrays1992Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Asymptotic analysis methods for performance prediction of so-called subspace directionof -arrival estimation methods has been developed earlier, assuming that a large-enough number of array measurements, or snapshots, is collected. This paper also addresses the problem of making performance predictions, but for beamspace-based subspace methods. The novel approach in this paper assumes the number of array elements to be large, while the number of snapshots is arbitrary. The perturbation effect, due to additive sensor noise, on a certain subspace is used for establishing the asymptotic behavior of direction-of-arrival estimates. The asymptotic estimation errors for the estimators resulting from Signal Subspace Fitting methods, such as WSF, and Noise Subspace Fitting (NSF) methods, such as MUSIC and a multi-dimensional counterpart to WSF, are shown to be asymptotically unbiased and normally distributed. Provided that the array response vectors become orthogonal when the number of array elements increases, the NSF methods are shown to give consistent estimates even in the case of fully coherent emitter signals, and the WSF method is shown to be consistent for coherent emitter signals even without this assumption. Comparisons with results for Maximum-Likelihood methods yield conditions for guaranteeing efficiency of the methods. Some simulation examples are also included.

  • 310.
    Andersson, Sören
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Beamspace Transformation Matrix Design using Numerical Optimization1992Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This paper addresses the problem of designing a data-dimension reducing transformation matrix, to be used for beamspace direction-of-arrival (DOA) estimation. The design of the transformation matrix is based on numerical optimization techniques. The criteria to be satisfied is to retain as much as possible of the achievable, optimal estimation accuracy using the non-reduced data-sizes, while also taking into account the sidelobe levels of the beampattern. Comparisons of estimation accuracy and sensitivity to out-of-sector emitters for the design methods considered herein are carried out by means of simulation examples, using the WSF-method for the DOA-estimation. In order to reduce the number of parameters to be optimized, a parametrization of the transformation matrix is made, that utilizes the properties of Householder-reflections.

  • 311.
    Andersson, Sören
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On Dimension Reduction in Sensor Array Signal Processing1992Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    During the last decades, sensor array signal processing has been a very active research area. More recently, relations between many of the proposed methods has been examined. The problem of assessing the estimation accuracy of these methods has also been addressed. Realworld applications of these techniques involves spatial distribution of several sensors to be used for collecting measurements of interesting emitted waveforms. From the measurements, detection and localization as well as estimation of the emitted waveforms can be accomplished. Common examples of applications are radar (electromagnetic waveforms) and sonar (acoustical underwater waveforms).

    Another aspect of array processing that recently has been addressed in the literature is that of dimension reduction, where the data vectors collected at the sensor outputs are reduced in size. This reduction is employed mainly in order to lower the amount of computations necessary for obtaining the parameter-estimates of interest; hut some other improvcments has also been observed. These include, e.g., lower sensitivity to sensor noise correlations and, for some estimation methods, higher resolution capability.

    In this thesis, it is demonstrated how to make the dimension reduction in an optimal fashion, where the optimality is with respect to estimation accuracy. More precisely, an expression to be satisfied by a transformation matrix acting on the sensor outputs is derived , that preserves the optimally achievable estimation accuracy (the Cramer-Rao bound) also in the reduced space. A transformation matrix design method that tries to reduce some unwanted properties of the optimal transformation is also outlined and examined. This method is based on numerical optimization of a particular performance mea.sure, motivated by the insight obtained in the process of finding the optimal transformation.

    l\foreover, an asymptotic analysis is performed, using the reduced data vectors, that examines the estimation accuracy of several estimation methods when a !arge number of sensor elements is used. This analysis is valid for a fairly general transformation matrix, and the methods considered are the Weighted Subspace Fitting (WSF) and Noise Subspace Fitting (NSF) methods, including MUSIC. By employing the optimal transformation matrix, the WSF method is shown to to be efficient, i.e., to attain the Cramer-Rao bound. An examination of the estimation accuracy, compared to that optimally attainable, is performed for the case when the transformation matrix differs from the optimal one. Finally, an application is studied, considering the potential use of sensor arrays in mobile communication systems.

  • 312.
    Andersson, Sören
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On Optimal Dimension Reduction for Sensor Array Signal Processing1991Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The computational complexity for direction-of-arrival estimation using sensor arrays increases very rapidly with the number of sensors in the array. One way to lower the amount of computations is to employ some kind of reduction of the data dimension. This is usually accomplished by employing linear transformations for mapping full dimension data into a lower dimensional space. Different approaches for selecting these transformations have been proposed. In this paper, a transformation matrix is derived that makes it possible to theoretically attain the full-dimension Cramér-Rao bound also in the reduced space. A bound on the dimension of the reduced data set is given, above which it is always possible to obtain the same accuracy for the estimates of the source localizations, using the lower-dimension data, as that achievable by using the full dimension data. Furthermore, a method is devised for designing the transformation matrix. Numerical examples, using this design method, are presented, where the achievable performance of the (optimal) Weighted Subspace Fitting method with full dimension data is compared to the performance obtained with reduced dimension data. The problem of estimating parameters of sinusoidal signals from noisy data is also addressed by a direct application of the results derived herein.

  • 313.
    Andersson, Sören
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On Two-Stage Schemes for Beamspace Direction-of-Arrival Estimation1992Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This paper addresses performance analysis of two-stage methods for direction-of-arrival (DOA) estimation. By first finding crude initial DOA-estimates, the idea is to use these estimates for designing a transformation matrix as the first step. Then this matrix is employed for mapping the data to the lower-dimensional beamspace. Different ways for obtaining the first-stage DOA-estimates are discussed and various trade-offs that have to be considered are pointed out. The beamspace version of the Weighted Subspace Fitting (WSF) method is used for obtaining the final DOA estimates. An approximate performance bound is stated that assumes the first-stage DOA-estimates to be close to the true DOAs. For comparing the performance of some different ways to obtain the first-stage DOA-estimate, some numerical examples are included.

  • 314.
    Andersson, Sören
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Optimal Dimension Reduction for Sensor Array Signal Processing1991Ingår i: Proceedings of the 25h Asilomar Conference on Signals, Systems and Computers, 1991, s. 918-922Konferensbidrag (Refereegranskat)
    Abstract [en]

    The computational complexity for direction-of-arrival estimation using sensor arrays increases very rapidly with the number of sensors in the array. One way to lower the amount of computations is to employ some kind of reduction of the data dimension. This is usually accomplished by employing linear transformations for mapping full-dimension data into a lower-dimensional space. In the present work, a transformation matrix is derived, that makes it possible to attain the full-dimension Cramer-Rao bound also in the reduced space. A bound on the dimension of the reduced data set is given, above which it is always possible to obtain the same accuracy for the lower-dimension estimates of the source localizations as that achievable by using the full-dimension data. Furthermore, a method is devised for designing the transformation matrix.

  • 315.
    Andersson, Sören
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Optimal Dimension Reduction for Sensor Array Signal Processing1991Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The computational complexity for direction-of-arrival estimation using sensor arrays increases very rapidly with the number of sensors in the array. One way to lower the amount of computations is to employ some kind of reduction of the data dimension. This is usually accomplished by employing linear transformations for mapping full-dimension data into a lower-dimensional space. In the present work, a transformation matrix is derived, that makes it possible to attain the full-dimension Cramer-Rao bound also in the reduced space. A bound on the dimension of the reduced data set is given, above which it is always possible to obtain the same accuracy for the lower-dimension estimates of the source localizations as that achievable by using the full-dimension data. Furthermore, a method is devised for designing the transformation matrix.

  • 316.
    Andersson, Sören
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Reduced Dimension Beam-Space Transformation Design using Optimization1990Rapport (Övrigt vetenskapligt)
  • 317.
    Andersson, Sören
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Sensor Array Processing: Application to Mobile Communication Systems and Dimension Reduction1990Licentiatavhandling, monografi (Övrigt vetenskapligt)
  • 318.
    Andersson, Sören
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Millnert, Mille
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Viberg, Mats
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Wahlberg, Bo
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Study of Adaptive Arrays for Mobile Communication Systems1991Ingår i: Proceedings of the 1991 International Conference on Acoustics, Speech and Signal Processing, 1991, s. 3289-3292Konferensbidrag (Refereegranskat)
    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.

  • 319.
    Andersson, Sören
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Millnert, Mille
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Viberg, Mats
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Wahlberg, Bo
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Study of Adaptive Arrays for Mobile Communication Systems1990Rapport (Övrigt vetenskapligt)
    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.

  • 320.
    Andersson, Sören
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Millnert, Mille
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Viberg, Mats
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Wahlberg, Bo
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    An Adaptive Array for Mobile Communication Systems1990Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The use of adaptive antenna techniques to increase the channel capacity 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 followed by optimal combination of the antenna outputs. Comparison with a method based on reference signals is 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.

  • 321.
    Andersson, Sören
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Millnert, Mille
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Viberg, Mats
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Wahlberg, Bo
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    An Adaptive Array for Mobile Communication Systems1991Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 40, nr 1, s. 230-236Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of adaptive antenna techniques to increase the channel capacity 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 followed by optimal combination of the antenna outputs. Comparison with a method based on reference signals is 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.

  • 322.
    Andersson, Sören
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Nehorai, Arye
    Yale University, USA.
    Analysis of a polarized seismic wave model1994Rapport (Övrigt vetenskapligt)
    Abstract [en]

    We present a model for polarized seismic waves where the data are collected by three-component geophone receivers. The model is based on two parameters describing the polarization properties of the waveforms. These parameters are the ellipticity and the orientation angle of the polarization ellipse. The model describes longitudinal waveforms (P-waves) as well as elliptically polarized waves. For the latter waves the direction-of-propagation of the waveform is in the plane spanned by the ellipse's major and minor axes; Rayleigh waves are treated as a special case. We analyze the identifiability of the models and derive the Cramer-Rao and mean-square-angular-error (MSAE) bounds involving one or two three-component geophones.

  • 323.
    Andersson, Sören
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Nehorai, Arye
    Yale University, USA.
    Optimal Dimension Reduction for Array Processing: Generalized1993Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This correspondence extends previously reported work [1, 2] on the problem, or rather possibility, of achieving optimality of beamspace (BS) array processing, where use is made of dimensionally reduced data vectors. The optimality here is with respect to the best possible element space (ESP) parameter estimation accuracy, i.e., the Cramér-Rao bound.

  • 324.
    Andersson, Sören
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Nehorai, Arye
    Yale University, USA.
    Some Comparisons of Cramer-Rao Bounds for Vector Sensors and Scalar Sensor Arrays for Array Processing1993Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The effect from polarization of emitted wave fronts on the parameter estimation accuracy for an array composed only of sensors sensitive to just one polarization direction has not been addressed in the literature this far. Antennas with such characteristics are, e.g., dipole (or scalar) antennas. A vector sensor, on the other hand, is a sensor whose output data consists of, for the electromagnetic case, the complete electric and magnetic fields at the sensor. This paper examines some of the effects on the Cram'er-Rao Bound for the elevation and/or azimuth angles to a single source emitting a polarized (electromagnetic) waveform. Since only one vector sensor is needed for estimation of both azimuth and elevation, it would be of interest to compare the lower parameter estimation error bound resulting from the vector sensor data model to the "ordinary" one, i.e. the data model used for scalar arrays. Such comparisons, both analytically and numerically, are herein made for an acoustic data model, as well as for an electromagnetic measurement model, for some simple scenarios and array configurations.

  • 325.
    Andersson, Sören
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Stoica, Petre
    Polytechnic Institute of Bucharest, Romania.
    Viberg, Mats
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Nehorai, Arye
    Yale University, USA.
    Eigenvector Matrix-Beamformers in Array Processing1994Rapport (Övrigt vetenskapligt)
  • 326.
    Andersson, Thord
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Läthén, Gunnar
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Lenz, Reiner
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Borga, Magnus
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Modified Gradient Search for Level Set Based Image Segmentation2013Ingår i: IEEE Transactions on Image Processing, ISSN 1057-7149, E-ISSN 1941-0042, Vol. 22, nr 2, s. 621-630Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Level set methods are a popular way to solve the image segmentation problem. The solution contour is found by solving an optimization problem where a cost functional is minimized. Gradient descent methods are often used to solve this optimization problem since they are very easy to implement and applicable to general nonconvex functionals. They are, however, sensitive to local minima and often display slow convergence. Traditionally, cost functionals have been modified to avoid these problems. In this paper, we instead propose using two modified gradient descent methods, one using a momentum term and one based on resilient propagation. These methods are commonly used in the machine learning community. In a series of 2-D/3-D-experiments using real and synthetic data with ground truth, the modifications are shown to reduce the sensitivity for local optima and to increase the convergence rate. The parameter sensitivity is also investigated. The proposed methods are very simple modifications of the basic method, and are directly compatible with any type of level set implementation. Downloadable reference code with examples is available online.

  • 327.
    Andersson, Tobias
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Increased Autonomy for Construction Equipment using Laser2010Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    At working sites all around monotonic tasks are performed. If one were able

    to automatize these kinds of tasks there would be a large economical profit to

    collect. Volvo CE are in the process of developing an autonomous wheel loader,

    to perform these types of monotonic, uniform tasks. The project is intended to

    be performed mainly be thesis workers. This report is the eighth thesis in this

    project. Earlier work has made the loader able to see a pile using a laser scanner.

    The machine can also see and fill a hauler. The usage of the laser scanner can

    only be made while the loader is standing still. The aim of this thesis work has

    been to make the loader able to scan its environment while it is moving. To do

    this an inertial measurement unit has been used for keeping track of the scanners

    orientation during a scan. The work of this thesis has resulted in a working set-up

    on the machine, and a robust framework for future work.

     

  • 328.
    Andersson, Tobias
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Wahlsten, Johan
    Linköpings universitet, Institutionen för systemteknik.
    Delta-Sigma Modulation Applied to Switching RF Power Amplifiers2007Självständigt arbete på grundnivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats
    Abstract [en]

    Background:

    The task of this thesis is to investigate the possibility of using non-linear high efficiency switching power amplifiers with spectrally efficient varying envelope modulation schemes and, if possible, further investigate such a solution on a high level.

    The thesis focuses on the theory necessary to understand the technical issues related to power amplifiers and the procedures behind simulating and measuring the characteristics of different power amplifier configurations. The thesis also covers basic theory behind Delta-Sigma-modulators. The theory is needed to draw conclusions about the feasibility of using a Delta-Sigma-modulator as input to a switching amplifier.

    Results:

    Using a Delta-Sigma-modulated input to a switching amplifier inherently degrades the performance, mainly because of poor coding efficiency and high switching activity. However, by merely using a switching amplifier as a mixer it is shown to be possible to transmit a non-constant envelope signal, with digital logic. The resulting circuit is, however, not an amplifier and it should not be seen as the final result. As already mentioned: the result lies in the investigation of a using Delta-Sigma-modulator as input to a switching amplifier.

    Conclusion:

    From this investigation we believe that the widely known technique: pulse width modulation (PWM), together with a tuned switching amplifier and some linearization technique, for example pre-distortion, is a better way to go. Much effort should be put in understanding the fundamental limits and possibilities of an efficient tuned switching power amplifier.

  • 329.
    Andersson, Torbjörn
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Concepts and Algorithms for Non-Linear System Identifiability1994Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Recently, commutative algebra and differential algebra have come to use as mathematical tools for solving problems in automatic control. We will use these tools to answer questions regarding identifiability for models given as a set of differential polynomials. A constructive algorithm, Ritt's algorithm, has been modified for this specific situation. Furthermore, comparisons between Ritt's algorithm and Buchberger's algorithm, to answer the identifiability question when the model structures are given in state space form, are performed. The basic problem is that the computational complexity rapidly increases with the problem size. We examine various ways to simplify the computations in this respect, but it must also be stressed that the complexity increase is inherent in the problem.

    In identification from a deterministic point of view an algorithm is said to be robustly convergent if the true system is regained when the noise level tends to zero. In this thesis we introduce a concept close to this performance measure; robust global identifiability. A model structure, i.e., a smoothly parameterized set of models, is said to be robustly globally identifiable if there exist an identification algorithm such that the true parameters are regained when the noise level tends to zero. In this thesis we show that global identifiability implies robust global identifiability when the considered model structure is a characteristic set of differential polynomials. This means that any model structure with parameters, that can be uniquely estimated from data has this robustness property.

    Finally, a method for estirnation of residence time in continuous flow systems with varying dynamics is discussed. By resampling, i.e., choosing time instants different from the given sampling instants, and interpolation between measured data points, we obtain a continuous fl.ow system with constant residence time expressed in a new resampled time vector. We assume that the fiow patterns in the systems are invariant. The new data set is then used for identification of parameters in a chosen model structure. From the identified model, the residence time is readily calculated and a procedure for that is briefly described. The presented method is readily extended to enable use in recursive identification. In that case the modified recursive identification method is an improvement of the tracking ability compared to an ordinary recursive routine.

  • 330.
    Andersson, Torbjörn
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Pucar, Predrag
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Estimation of Residence Time in Continuous Flow Systems with Dynamics1994Ingår i: Proceedings of the 10th IFAC Symposium on System Identification, 1994, Vol. 3, s. 401-406Konferensbidrag (Refereegranskat)
    Abstract [en]

    A method for estimation of residence time in continuous flow systems with varying dynamics is presented. By resampling, i.e., choosing time instants different from the given sampling instants, and interpolation between measured data points, we obtain a continuous flow system with constant residence time expressed in the new resampled time vector. We assume the flow patterns in the systems are invariant. The new data set is then used for identification of parameters in a chosen model structure. From the identified model, the residence time is readily calculated and a procedure for that is briefly described. The presented method is readily extended to enable use in recursive identification. In that case, however, as an improvement of tracking ability of an ordinary recursive routine.

  • 331.
    Andersson, Torbjörn
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Pucar, Predrag
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Estimation of Residence Time in Continuous Flow Systems with Dynamics1994Rapport (Övrigt vetenskapligt)
    Abstract [en]

    A method for estimation of residence time in continuous flow systems with varying dynamics is presented. By resampling, i.e., choosing time instants different from the given sampling instants, and interpolation between measured data points, we obtain a continuous flow system with constant residence time expressed in the new resampled time vector. We assume the flow patterns in the systems are invariant. The new data set is then used for identification of parameters in a chosen model structure. From the identified model, the residence time is readily calculated and a procedure for that is briefly described. The presented method is readily extended to enable use in recursive identification. In that case, however, as an improvement of tracking ability of an ordinary recursive routine.

  • 332.
    Andersson, Torbjörn
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Pucar, Predrag
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Estimation of Residence Time in Continuous Flow Systems with Dynamics1994Rapport (Övrigt vetenskapligt)
    Abstract [en]

    A method for estimation of residence time in continuous flow systems with varying dynamics is presented. By resampling, i.e., choosing time instants different from the given sampling instants, and interpolation between measured data points, we obtain a continuous flow system with constant residence time expressed in the new resampled time vector. We assume the flow patterns in the systems are invariant. The new data set is then used for identification of parameters in a chosen model structure. From the identified model, the residence time is readily calculated and a procedure for that is briefly described. The presented method is readily extended to enable use in recursive identification. In that case, however, as an improvement of tracking ability of an ordinary recursive routine.

  • 333.
    Andersson, Torbjörn
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Pucar, Predrag
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Estimation of Residence Time in Continuous Flow Systems with Dynamics1995Ingår i: Journal of Process Control, ISSN 0959-1524, E-ISSN 1873-2771, Vol. 5, nr 1, s. 9-17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method for estimation of residence time in continuous flow systems with varying dynamics is presented. By resampling, i.e., choosing time instants different from the given sampling instants, and interpolation between measured data points, we obtain a continuous flow system with constant residence time expressed in the new resampled time vector. We assume the flow patterns in the systems are invariant. The new data set is then used for identification of parameters in a chosen model structure. From the identified model, the residence time is readily calculated and a procedure for that is briefly described. The presented method is readily extended to enable use in recursive identification. In that case, however, as an improvement of tracking ability of an ordinary recursive routine. Keywords : System identification, residence time estimation, time-varying systems, variable flow and/or volume, continuous flow systems, recursive identification.

  • 334.
    Andersson, Torbjörn
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Pucar, Predrag
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Estimation of Residence Time in Continuous Flow Systems with Varying Flow and Volume1993Rapport (Övrigt vetenskapligt)
    Abstract [en]

    A method for estimation of residence time in continuous flow vessels with variable flow and volume is presented. By resampling, i.e., choosing time instants different from the given sampling instants, and interpolation of measured data points, we obtain a continuous flow system with constant residence time expressed in the new resampled time vector, assuming the flow patterns in the vessels and tanks are invariant. The new data set is then used for identification of parameters in a chosen model structure. From the identified model the residence time is easily calculated and a procedure for that is briefly described. The presented method is easily extended to enable use in recursive identification but then as an improvement of tracking ability of an ordinary recursive routine.

  • 335.
    Andersson, Torbjörn
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Pucar, Predrag
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Identifying Models using Piecewise Linear Approximation of Input Signals1992Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Very often in system identification problems it is assumed that the input signal is piecewise constant but in many practical cases this is not the fact. In such cases when the input signal is continuous it shows that a piecewise linear approximation of the input signal leads to a better model. In this report it is shown how to handle system identification problems using state space descriptions and the assumption of piecewise linear input signals with MathWork's system identification software.

  • 336.
    Andersson, Torbjörn
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Pucar, Predrag
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Isaksson, Alf
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Projekt operatörsverktyg, delprojekt 4: Modeller för massatransport och beräkning av uppehållstid i fiberlinjen. Slutrapport1992Rapport (Övrigt vetenskapligt)
  • 337.
    Andersson, Torbjörn
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Pucar, Predrag
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Identification Aspects of Inter-Sample Input Behavior1994Ingår i: Proceedings of the 10th IFAC Symposium on System Identification, 1994, Vol. 3, s. 137-142Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this contribution aspects of inter-sample input signal behavior are examined. The starting point is that parametric identification always is performed on basis of discrete-time data. This is valid for identification of discrete-time models as well as continuous-time models. The usual assumptions on the input signal are; i) it is band-limited, ii) it is piecewise constant or iii) it is piecewise linear. One point made in this paper is that if a discrete-time model is used, the best possible (in the model structure) adjustment to data is made. This is independent of the assumption on the input signal. However, a transformation of the obtained discrete model to a continuous one is not possible without additional assumptions on the input signal. The other point made is that the frequency functions of the discrete models very well coincides with the frequency functions of the discretized continuous time models and the continuous time transfer function fitted in the frequency domain.

  • 338.
    Andersson, Torbjörn
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Pucar, Predrag
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Identification Aspects of Inter-Sampling Behavior1994Rapport (Övrigt vetenskapligt)
    Abstract [en]

    In this contribution aspects of inter-sample input signal behavior are examined. The starting point is that parametric identication always is performed on basis of discrete-time data. This is valid for identication of discrete-time models as well as continuous-time models. The usual assumptions on the input signal are; i) it is band-limited, ii) it is piecewise constant or iii) it is piecewise linear. One point made in this paper is that if a discrete-time model is used, the best possible (in the model structure) adjustment to data is made. This is independent of the assumption on the input signal. However, a transformation of the obtained discrete model to a continuous one is not possible without additional assumptions on the input signal. The other point made is that the frequency functions of the discrete models very well coincides with the frequency functions of the discretized continuous time models and the continuous time transfer function fitted in the frequency domain.

  • 339.
    Andersson, Veronika
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Sjöstedt, Hanna
    Linköpings universitet, Institutionen för systemteknik.
    Improved effort estimation of software projects based on metrics2005Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats
    Abstract [en]

    Saab Ericsson Space AB develops products for space for a predetermined price. Since the price is fixed, it is crucial to have a reliable prediction model to estimate the effort needed to develop the product. In general software effort estimation is difficult, and at the software department this is a problem.

    By analyzing metrics, collected from former projects, different prediction models are developed to estimate the number of person hours a software project will require. Models for predicting the effort before a project begins is first developed. Only a few variables are known at this state of a project. The models developed are compared to a current model used at the company. Linear regression models improve the estimate error with nine percent units and nonlinear regression models improve the result even more. The model used today is also calibrated to improve its predictions. A principal component regression model is developed as well. Also a model to improve the estimate during an ongoing project is developed. This is a new approach, and comparison with the first estimate is the only evaluation.

    The result is an improved prediction model. There are several models that perform better than the one used today. In the discussion, positive and negative aspects of the models are debated, leading to the choice of a model, recommended for future use.

  • 340.
    Andersson, Viktor
    Linköpings universitet, Institutionen för systemteknik, Datorseende.
    Semantic Segmentation: Using Convolutional Neural Networks and Sparse dictionaries2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The two main bottlenecks using deep neural networks are data dependency and training time. This thesis proposes a novel method for weight initialization of the convolutional layers in a convolutional neural network. This thesis introduces the usage of sparse dictionaries. A sparse dictionary optimized on domain specific data can be seen as a set of intelligent feature extracting filters. This thesis investigates the effect of using such filters as kernels in the convolutional layers in the neural network. How do they affect the training time and final performance?

    The dataset used here is the Cityscapes-dataset which is a library of 25000 labeled road scene images.The sparse dictionary was acquired using the K-SVD method. The filters were added to two different networks whose performance was tested individually. One of the architectures is much deeper than the other. The results have been presented for both networks. The results show that filter initialization is an important aspect which should be taken into consideration while training the deep networks for semantic segmentation.

  • 341.
    Andreas, Svensson
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Model Predictive Control with Invariant Sets in Artificial Pancreas for Type 1 Diabetes Mellitus2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis deals with Model Predictive Control (MPC) for artificial pancreas for Type 1 Diabetes Mellitus patients. A control strategy exploiting invariant sets in MPC for blood glucose level control is developed, to the authors knowledge for the first time. The work includes various types of invariant sets relevant for the artificial pancreas problem, and different ways to incorporate them into the MPC strategy. The work is an extension to the zone MPC controller for artificial pancreas developed at University of California Santa Barbara and Sansum Diabetes Research Institute.

    The evaluation of the proposed control strategy is done in silico in the U.S. Food and Drug Administration approved metabolic simulator. The trials show some promising results in terms of more rapid meal responses and decreased variability between the subjects than the zone MPC. An attempt to robust control employing invariant sets proved to be less promising in the evaluations. The results indicate that the direct application of known robust control techniques is not appropriate, and that more appropriate robust control techniques must be searched for, or developed, more specific to the artificial pancreas control.

    Altogether, this thesis pinpoints a possible future direction of artificial pancreas control design, with MPC based on invariant sets.

  • 342.
    Andreu-Cabedo, Yasmina
    et al.
    University of Central Lancashire, England.
    Castellano, Pedro
    University of Central Lancashire, England.
    Colantonio, Sara
    National Research Council Italy, Italy.
    Coppini, Giuseppe
    National Research Council Italy, Italy.
    Favilla, Riccardo
    National Research Council Italy, Italy.
    Germanese, Danila
    National Research Council Italy, Italy.
    Giannakakis, Giorgos
    Fdn Research and Technology, Greece.
    Giorgi, Daniela
    National Research Council Italy, Italy.
    Larsson, Marcus
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Marraccini, Paolo
    National Research Council Italy, Italy.
    Martinelli, Massimo
    National Research Council Italy, Italy.
    Matuszewski, Bogdan
    University of Central Lancashire, England.
    Milanic, Matijia
    Norvegian University of Science and Technology, Norway.
    Pascali, Mariantonietta
    National Research Council Italy, Italy.
    Pediaditis, Mattew
    Fdn Research and Technology, Greece.
    Raccichini, Giovanni
    National Research Council Italy, Italy.
    Randeberg, Lise
    Norvegian University of Science and Technology, Norway.
    Salvetti, Ovidio
    National Research Council Italy, Italy.
    Strömberg, Tomas
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    MIRROR MIRROR ON THE WALL... AN INTELLIGENT MULTISENSORY MIRROR FOR WELL-BEING SELF-ASSESSMENT2015Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON MULTIMEDIA and EXPO (ICME), IEEE , 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    The face reveals the healthy status of an individual, through a combination of physical signs and facial expressions. The project SEMEOTICONS is translating the semeiotic code of the human face into computational descriptors and measures, automatically extracted from videos, images, and 3D scans of the face. SEMEOTICONS is developing a multisensory platform, in the form of a smart mirror, looking for signs related to cardio-metabolic risk. The goal is to enable users to self-monitor their well-being status over time and improve their life-style via tailored user guidance. Building the multisensory mirror requires addressing significant scientific and technological challenges, from touch-less data acquisition, to real-time processing and integration of multimodal data.

  • 343.
    André, Simon
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Design and Optimization of Controllers for an Electro-Hydraulic System2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Electro-Hydraulic (EH) systems are commonly used in the industry for applications that require high power-weight ratios and large driving forces. The EH system studied in this master thesis have recently been upgraded with new hardware components and as a part of this upgrade a new controller was requested. The system consists of a controller that computes a control signal for an electric motor. The motor drives a gear pump that generates a flow of hydraulic fluid. The flow is then directed to a cylinder. The movements of a piston in the cylinder is affected by the flow and the piston position can be measured. The measured piston position is then fed back to the controller and the control loop is complete. The system was previously controlled using a Proportional-Integral-Derivative (PID) controller and the purpose of this thesis is to compare the old controller with alternative control strategies suitable for this application. The evaluation of the controllers is based on both software and hardware simulations and results in a recommendation for final implementation of the best suited controller. The control strategies chosen for investigation are: a retuned PID controller, a PID controller with feed forward from reference, a PID based cascade controller, a Linear Quadratic (LQ) controller, and a Model Predictive Controller (MPC). To synthesize the controllers an approximate model of the system is formed and implemented in the software environment Matlab Simulink. The model is tuned to fit recorded data and provides a decent estimation of the actual system. The proposed control strategies are then simulated and evaluated in Simulink with the model posing as the real system. These simulations resulted in the elimination of the cascade controller as a possible candidate since it proved unstable for large steps in the reference signal. The remaining four controllers were all selected for simulation on the real hardware system. Unfortunately the MPC was never successfully implemented on the hardware due to some unknown compatibility error and hence eliminated as a possible candidate. The three remaining control strategies, PID, PID with feed forward from reference and the LQ controller, were all successfully implemented and simulated on hardware. The results from the hardware simulations compared to simulations made with the old controller, as well as the results from the software simulations, were then evaluated. Depending on the purpose one of two control strategies is recommended for this application. The LQ controller achieved the best overall performance and is presented as the control strategy best suited for this application.

  • 344.
    Andrén, Filip
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Optimization of Random Access in 3G Long Term Evolution2009Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Before a mobile can commence services it needs to have access to a base station. The access method is often referred to as random access (RA). One way to measure the performance of the RA procedure is the access delay (AD) of the mobiles, where AD is the time from which a mobile wants to start a RA attempt until it has received access.

    There are different approaches to optimize the RA procedure. Manual optimization is possible but costly. Automated optimization is preferable because of the lower costs and the possibility to change configuration fast in the base station when the operational conditions change. This thesis focuses on automated optimization of the RA procedure with regard to AD.

    A controllability and observability study of AD is first presented in this thesis. The controllability study shows that AD can be controlled by a number of RA parameters, whereas the observability study show that AD cannot always be correctly observed. The next part of this thesis presents a controller synthesis, where three different controllers are presented to control a specified percentile of AD. It is shown, through experiments, that the controllers derived can be used to optimize the RA procedure with regard to AD.

  • 345.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Askoxylakis, Ioannis
    FORTH, Institute of Computer Science, Greece.
    Fowler, Scott
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Gundlegård, David
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Traganitis, Apostolos
    FORTH, Institute of Computer Science, Greece.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Security and Resilience in Cognitive Radio Networks2011Ingår i: European Research Consortium for Informatics and Mathematics Magazine, ISSN 0926-4981, nr 85, s. 48-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    After more than a decade of research, system securityand resilience is now the major technological barrier forthe Cognitive Radio (CR) to be adopted by the telecommunication industry. New ideas are required tomake CR networks secure and robust against attacks taking advantage the inherent characteristics of the CR functionality. This work explores key points that urgentlyneed to be addressed.

  • 346.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Avgouleas, Ioannis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Fitzgerald, Emma
    Lund University, Sweden.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten. University of Maryland, MD 20742 USA.
    Allocation of Heterogeneous Resources of an IoT Device to Flexible Services2016Ingår i: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 3, nr 5, s. 691-700Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Internet-of-Things (IoT) devices can be equipped with multiple heterogeneous network interfaces. An overwhelmingly large amount of services may demand some or all of these interfaces available resources. Herein, we present a precise mathematical formulation of assigning services to interfaces with heterogeneous resources in one or more rounds. For reasonable instance sizes, the presented formulation produces optimal solutions for this computationally hard problem. We prove the NP-completeness of the problem and develop two algorithms to approximate the optimal solution for big instance sizes. The first algorithm allocates the most demanding service requirements first, considering the average cost of interfaces resources. The second one calculates the demanding resource shares and allocates the most demanding of them first by choosing randomly among equally demanding shares. Finally, we provide simulation results giving insight into services splitting over different interfaces for both cases.

  • 347.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Avgouleas, Ioannis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Flexible allocation of heterogeneous resources to services on an IoT device2015Ingår i: 2015 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 99-100Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the Internet of Things (IoT), devices and gateways may be equipped with multiple, heterogeneous network interfaces which should be utilized by a large number of services. In this work, we model the problem of assigning services' resource demands to a device's heterogeneous interfaces and give a Mixed Integer Linear Program (MILP) formulation for it. For meaningful instance sizes the MILP model gives optimal solutions to the presented computationally-hard problem. We provide insightful results discussing the properties of the results on the properties of the derived solutions with respect to the splitting of services to different interfaces.

  • 348.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Chen, Lei
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    A Fully Decentralized and Load-Adaptive Fractional Frequency Reuse Scheme2011Ingår i: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2011 IEEE 19th International Symposium on, 2011, s. 425-428Konferensbidrag (Refereegranskat)
    Abstract [en]

    A new fully decentralized dynamic fractional frequency reuse (FFR)-based scheme for cellular OFDMA networks is introduced. FFR is a technique to mitigate inter-cell interference to improve the throughput of interference-limited users on the cell edge, to the expense of the rest of the cell's users and the aggregate throughput. The proposed scheme aims to limit the FFR-incurred loss of the center users' throughput, while still providing sufficient bandwidth for the cell edge users' communication. This is done by local information sharing and distributed optimization. The resulting flexibility of frequency reuse can be especially beneficial in scenarios with non-uniform and time-varying load. The optimization task is accomplished by solving a knapsack problem in each cell, where the goal is to maximize the center throughput while maintaining acceptable degradation on the cell edge with respect to the original FFR allocation. The performance improvement resulting from the distributed and dynamic FFR scheme is demonstrated by snapshot simulations on an 81-cells network with asymmetric cell load. The proposed scheme achieves up to a 62% gain in cell-center throughput with a cost of no more than 18% at the edges when compared to the classic FFR scheme. The overall system throughput improvement ranges from 22% to 58%.

  • 349.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Efrat, Alon
    University of Arizona, AZ 85721 USA.
    Packer, Eli
    IBM Research Haifa, Israel.
    Polishchuk, Valentin
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Sedov, Leonid
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    BBTM: New life for old ATM2016Ingår i: 2016 IEEE/AIAA 35TH DIGITAL AVIONICS SYSTEMS CONFERENCE (DASC), IEEE , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates algorithmic questions related to the possibility of managing UAV traffic with beacon-based navigation, which we dub BBTM - Beacon-Based Traffic Management. The specific problem addressed is: How to install the minimum number of beacons in a mountainous terrain to ensure connectivity among a given set of UAS terminals on the terrain? BBTM is relevant for low-cost UAVs operating in remote areas not on time-critical missions, and may also be used as a backup system for better-equipped UAS in case the precise positioning or control information is lost, spoofed or jammed. We give algorithms for the beacon tower placement and evaluate their performance both on synthetic and real-world terrain data; the experiments suggest that our solutions can be used to efficiently quantify costs of establishing direct-visibility routing networks for UAS management.

  • 350.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Papadakis, Stefanos
    FORTH.
    Traganitis, Apostolos
    FORTH & UoC.
    Vasilios, Siris
    AUEB.
    Adjacent Channel Interference in 802.11a Is Harmful: Testbed Validation of a Simple Quantification Model2011Ingår i: IEEE COMMUNICATIONS MAGAZINE, ISSN 0163-6804, Vol. 49, nr 3, s. 160-166Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wireless LAN radio interfaces based on the IEEE 802.11a standard have lately found widespread use in many wireless applications. A key reason for this was that although the predecessor, IEEE 802.11b/ g, had a poor channelization scheme, which resulted in strangling adjacent channel interference (ACI), 802.11a was widely believed to be ACI-free due to a better channelization combined with OFDM transmission. We show that this is not the case. ACI does exist in 802.11a, and we can quantify its magnitude and predict its results. For this, we present minor modifications of a simple model originally introduced by [1] that allow us to calculate bounding values of the 802.11a ACI, which can be used in link budget calculations. Using a laboratory testbed, we verify the estimations of the model, performing experiments designed to isolate the affected 802.11 mechanisms. This isolation was enabled by not using the wireless medium, and emulating it over cables and attenuators. Our results show clear throughput degradation because of ACI in 802.11a, the magnitude of which depends on the interfering data rates, packet sizes, and utilization of the medium.

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