liu.seSearch for publications in DiVA
Change search
Refine search result
1234567 101 - 150 of 496
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 101.
    Dully, Michael
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Traffic Safety Evaluation of Future Road Lighting Systems2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    While new road lighting technologies, either LED or adaptive road lighting systems, offer a wide range of unique potential benefits (mainly in terms of energy savings), it is necessary to evaluate the safety impacts of these technologies on road users. The literature survey shows that providing light on previous unlit roads has a positive effect on traffic safety. Reducing the amount of light has the opposite effect. These studies are usually conducted by using crash numbers, which makes it impossible to draw conclusions on changes in driving behaviour. Driving behaviour analyses need special approaches and indicators. Therefore indirect indicators such as speed and safety relationship, jerky driving and traffic conflict parameters are presented. The individual character of such data is difficult to deal with and limits big scale analyses. In order to have a practical example of such indicators a case study is conducted. Floating car data collected in Vienna is used to analyse travel speeds of taxi drivers at two LED test sites. A simple before-after analysis is used with data from January 2011 to May 2012 in order to examine an expected increase in speed due to a better visual performance of LED light. However the results show either no changes at all or a trend in speed reduction of 1km/h in average. Unfavourable test site locations might limit the significance of the results.

  • 102.
    Duong, Le
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    A model to predict the coverage of VHF transmissions2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    VHF står för "Very High Frequency" och är ett frekvensband som ligger i området 30 - 300 MHz. Maritim VHF är standard för Sjöfartsverket och fungerar över hela världen. Det är ett kommunikationssystem som bidrar till ökad säkerhet och kan rädda liv på sjön. Andra vanliga kommunikationssystem som mobiltelefoni fungerar inte tillförlitligt. Idag fungerar mobiltelefoni i stora delar av skärgården och längs kusterna men när det gäller kommunikation mellan fartyg längre ut till havs är den maritima VHF-kommunikationen överlägsen. Sjöfartsverket driver för sitt eget och kunders behov ett mobilradionätverk kallat kustradionätverket. Radiotrafiken i nätet sker både på Very High Frequency (VHF) och Medium frequency (MF). VHF-systemet är ett internationellt system som bland annat används till att kommunicera till sjöss och den trafiken befinner sig i frekvensbandet 155.5 - 162.025 MHz. Inom VHF-bandet finns det 55 kanaler. Kanalerna vid kustradiostationen kallas för duplexkanaler och innebär att kustradiostationerna sänder och tar emot signaler på två olika frekvenser. Radioutbredningen hos antennen som är installerad på basstationen har riktverkan i vissa riktningar och dämpningar i andra. Detta kan ses i strålningsdiagrammet under kapitlet "Täckningsmodell" och avsnittet antennen. Andra faktorer som kan påverka radioutbredningen är förluster i basstationenssystemet, topologin hos området mellan sändare och mottagare samt väderberoende utbredningsegenskaper. Genom att hitta de tänkbara faktorer som påverkar signalutbredningen kan en täckningsmodell förutses. Det är förluster som finns i basstationen, radiolänken samt förluster vid mottagarantennen.

  • 103.
    Duong, Quoc-Tai
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    Efficient Integrated Circuits for Wideband Wireless Transceivers2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The proliferation of portable communication devices combined with the relentless demand for higher data rates has spurred the development of wireless communication standards which can support wide signal bandwidths. Benefits of the complementary metal oxide semiconductor (CMOS) process such as high device speeds and low manufacturing cost have rendered it the technology of choice for implementing wideband wireless transceiver integrated circuits (ICs). This dissertation addresses the key challenges encountered in the design of wideband wireless transceiver ICs. It is divided into two parts. Part I describes the design of crucial circuit blocks such as a highly selective wideband radio frequency (RF) front-end and an on-chip test module which are typically found in wireless receivers. The design of high-speed, capacitive DACs for wireless transmitters is included in Part II.

    The first work in Part I is the design and implementation of a wideband RF frontend in 65-nm CMOS. To achieve blocker rejection comparable to surface-acousticwave (SAW) filters, the highly selective and tunable RF receiver utilizes impedance transformation filtering along with a two-stage architecture. It is well known that the low-noise amplifier (LNA) which forms the first front-end stage largely decides the receiver performance in terms of noise figure (NF) and linearity (IIP3/P1dB). The proposed LNA uses double cross-coupling technique to reduce NF while complementary derivative superposition (DS) and resistive feedback are employed to achieve high linearity. The resistive feedback also enhances input matching. In measurements, the front-end achieves performance comparable to SAW filters with blocker rejection greater than 38 dB, NF 3.2–5.2 dB, out-of-band IIP3 > +17 dBm and blocker P1dB > +5 dBm over a frequency range of 0.5–3 GHz.

    The second work in Part I is the design of an RF amplitude detector for on-chip test. As the complexity of RF ICs continues to grow, the task of testing and debugging them becomes increasingly challenging. The degradation in performance or the drift from the optimal operation points may cause systems to fail. To prevent this effect and ensure acceptable performance in the presence of process, voltage and temperature variations (PVT), test and calibration of the RF ICs become indispensable. A wideband, high dynamic range RF amplitude detector design aimed at on-chip test is proposed. Gain-boosting and sub-ranging techniques are applied to the detection circuit to increase the gain over the full range of input amplitudes without compromising the input impedance. A technique suitable for on-chip third/second-order intercept  point (IP3/IP2) test by embedded RF detectors is also introduced.

    Part II comprises the design and analysis of high-speed switched-capacitor (SC) DACs for 60-GHz radio transmitters. The digital-to-analog converter (DAC) is one of the fundamental building blocks of transmitters. SC DACs offer several advantages over the current-steering DAC architecture. Specifically, lower capacitor mismatch helps the SC DAC to achieve higher linearity. The switches in the SC DAC are realized by MOS transistors in the triode region which substantially relaxes the voltage headroom requirement. Consequently, SC DACs can be implemented using lower supply voltages in advanced CMOS process nodes compared to their currentsteering counterparts. The first work in Part II analyzes the factors limiting the performance of capacitive pipeline DACs. It is shown that the DAC performance is  limited mainly by the clock feed-through and settling effects in the SC  arrays while the impact of capacitor mismatch and kT/C noise are found to be negligible. Based on this analysis, the second work in Part II proposes the split-segmented SC array DAC to overcome the clock feed-through problem since this topology eliminates pipelined charge propagation. Implemented in 65-nm CMOS, the 12-bit SC DAC achieves a Spurious Free Dynamic Range (SFDR) greater than 44 dB within the input signal bandwidth (BW) of 1 GHz with on-chip memory embedded for digital data generation. Power dissipation is 50 mW from 1.2 V supply. Similar performance is achieved with a lower supply voltage (0.9 V) which shows the scalability of the SC DAC for more advanced CMOS technologies. Furthermore, the proposed SC DAC satisfies the spectral mask of the IEEE 802.11ad WiGig standard with a second-order reconstruction filter and hence it can be used for the 60-GHz radio baseband.

    List of papers
    1. Analysis and design of low noise transconductance amplifier for selective receiver front-end
    Open this publication in new window or tab >>Analysis and design of low noise transconductance amplifier for selective receiver front-end
    2015 (English)In: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 85, no 2, p. 361-372Article in journal (Refereed) Published
    Abstract [en]

    Analysis and design of a low-noise transconductance amplifier (LNTA) aimed at selective current-mode (SAW-less) wideband receiver front-end is presented. The proposed LNTA uses double cross-coupling technique to reduce noise figure (NF), complementary derivative superposition, and resistive feedback to achieve high linearity and enhance input matching. The analysis of both NF and IIP3 using Volterra series is described in detail and verified by SpectreRF (A (R)) circuit simulation showing NF less than 2 dB and IIP3 = 18 dBm at 3 GHz. The amplifier performance is demonstrated in a two-stage highly selective receiver front-end implemented in 65 nm CMOS technology. In measurements the front-end achieves blocker rejection competitive to SAW filters with noise figure 3.2-5.2 dB, out of band IIP3 greater than+17 dBm and blocker P-1dB greater than+5 dBm over frequency range of 0.5-3 GHz.

    Place, publisher, year, edition, pages
    Springer, 2015
    Keywords
    Low-noise transconductance amplifier (LNTA); Highly linear LNA; Wideband LNA; SAW-less receiver; Wideband selective RF front-end
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-122187 (URN)10.1007/s10470-015-0629-5 (DOI)000361984600014 ()
    Available from: 2015-10-26 Created: 2015-10-23 Last updated: 2017-12-01Bibliographically approved
    2. Two Stage Highly Selective Receiver Front End Based on Impedance Transformation Filtering
    Open this publication in new window or tab >>Two Stage Highly Selective Receiver Front End Based on Impedance Transformation Filtering
    2015 (English)In: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 62, no 5, p. 421-425Article in journal (Refereed) Published
    Abstract [en]

    In order to achieve blocker rejection comparable to surface acoustic wave (SAW) filters, we propose a two-stage tunable receiver front-end architecture based on impedance frequency transformation and low-noise transconductance amplifier (LNTA) circuits. The filter rejection is captured by a linear periodically varying model that includes band limitation by the LNTA output impedance and the related parasitic capacitances of the impedance transformation circuit. The effect of thermal noise folding on the circuit noise figure, as well as clock phase mismatch on filter gain are also discussed. As a proof of concept, a chip design of a tunable radio-frequency front end using 65-nm CMOS technology is presented. In measurements the circuit achieves blocker rejection competitive to SAW filters with noise figure 3.2-5.2 dB, out of band IIP3 > +17 dBm and blocker P1 dB > +5 dBm over frequency range of 0.5-3 GHz.

    Keywords
    SAW-less receiver, N-path filter, wideband selective RF front-end
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-112879 (URN)10.1109/TCSII.2014.2385213 (DOI)000353636400001 ()
    Available from: 2014-12-18 Created: 2014-12-18 Last updated: 2017-12-05Bibliographically approved
    3. Wideband RF Detector Design for High Performance On-Chip Test
    Open this publication in new window or tab >>Wideband RF Detector Design for High Performance On-Chip Test
    2012 (English)In: NORCHIP 2012, IEEE , 2012, p. 1-4Conference paper, Published paper (Refereed)
    Abstract [en]

    A wideband, high dynamic range RF amplitude detector design aimed at on-chip test is presented. Boosting gain and sub-ranging techniques are applied to the detection circuit to increase gain over the full range of input amplitudes without compromising the input impedance. Followed by a variable gain amplifier (VGA) and a 9-bit A/D converter the RF detector system, designed in 65 nm CMOS, achieves in simulation the minimum detectable signal of -58 dBm and 63 dB dynamic range over 0.5 GHz - 9 GHz band with input impedance larger than 4 kΩ. The detector is intended for on-chip calibration and the attained specifications put it among the reported state-of-the-art solutions.

    Place, publisher, year, edition, pages
    IEEE, 2012
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-86345 (URN)10.1109/NORCHP.2012.6403140 (DOI)978-1-4673-2222-5 (ISBN)978-1-4673-2221-8 (ISBN)
    Conference
    IEEE NORCHIP 2012, 12-13 November 2012, Copenhagen, Denmark
    Available from: 2012-12-13 Created: 2012-12-13 Last updated: 2016-01-18
    4. Focused Calibration for Advanced RF Test with Embedded RF Detectors
    Open this publication in new window or tab >>Focused Calibration for Advanced RF Test with Embedded RF Detectors
    2013 (English)In: European Conference on Circuit Theory and Design (ECCTD), 2013, IEEE , 2013, p. 1-4Conference paper, Published paper (Refereed)
    Abstract [en]

    In this paper a technique suitable for on-chip IP3/IP2 RF test by embedded RF detectors is presented. A lack of spectral selectivity of the detectors and diverse nonlinearity of the circuit under test (CUT) impose stiff constraints on the respective test measurements for which focused calibration approach and a support by customized models of CUT is necessary. Also cancellation of second-order intermodulation effects produced by the detectors under the two-tone test is required. The test technique is introduced using a polynomial model of the CUT. Simulation example of a practical CMOS LNA under IP3/IP2 RF test with embedded RF detectors is presented showing a good measurement accuracy.

    Place, publisher, year, edition, pages
    IEEE, 2013
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-97268 (URN)10.1109/ECCTD.2013.6662259 (DOI)9783000437854 (ISBN)9783000434303 (ISBN)
    Conference
    21st European Conference on Circuit Theory and Design (ECCTD), September 8-12, Dresden, Germany
    Available from: 2013-09-05 Created: 2013-09-05 Last updated: 2016-01-18Bibliographically approved
    5. Design and Analysis of High Speed Capacitive Pipeline DACs
    Open this publication in new window or tab >>Design and Analysis of High Speed Capacitive Pipeline DACs
    2014 (English)In: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 80, no 3, p. 359-374Article in journal (Refereed) Published
    Abstract [en]

    Design of a high speed capacitive digital-to-analog converter (SC DAC) is presented for 65 nm CMOS technology. SC pipeline architecture is used followed by an output driver. For GHz frequency operation with output voltage swing suitable for wireless applications (300 mVpp) the DAC performance is shown to be limited by the capacitor array imperfections. While it is possible to design a highly linear output driver with HD3 < -70 dB and HD2 < -90 dB over 0.55 GHz band as we show, the maximum SFDR of the SC DAC is 45 dB with 8-bit resolution and Nyquist sampling of 3 GHz. The analysis shows the DAC performance is determined by the clock feed-through and settling effects in the SC array and not by the capacitor mismatch or kT/C noise, which appear negligible in this application. The capacitor array is designed based on the DAC design area defined in terms of the switch size and unit capacitance value. A tradeoff between the DAC bandwidth and resolution accompanied by SFDR is demonstrated. The high linearity of the output driver is attained by a combination of two techniques, the derivative superposition (DS) and resistive source degeneration. In simulations the complete Nyquist-rate DAC achieves SFDR of 45 dB with 8-bit resolution for signal bandwidth 1.36 GHz. With 6-bit and 5.5 GHz bandwidth 33 dB SFDR is attained. The total power consumption of the SC DAC is 90 mW with 1.2 V supply and clock frequency of 3 GHz.

    Keywords
    capacitive DAC, high speed DAC, highly linear output driver
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-105516 (URN)10.1007/s10470-014-0350-9 (DOI)000342079400005 ()
    Available from: 2014-03-25 Created: 2014-03-25 Last updated: 2019-09-05
    6. A 1-GHz Bandwidth 12-bit SC DAC for 60-GHz Radio in 65-nm CMOS
    Open this publication in new window or tab >>A 1-GHz Bandwidth 12-bit SC DAC for 60-GHz Radio in 65-nm CMOS
    (English)Manuscript (preprint) (Other academic)
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering Signal Processing Communication Systems
    Identifiers
    urn:nbn:se:liu:diva-124007 (URN)
    Available from: 2016-01-18 Created: 2016-01-18 Last updated: 2019-09-05Bibliographically approved
    7. Tunable Selective Receiver Front-End with Impedance Transformation Filtering
    Open this publication in new window or tab >>Tunable Selective Receiver Front-End with Impedance Transformation Filtering
    2016 (English)In: International journal of circuit theory and applications, ISSN 0098-9886, E-ISSN 1097-007X, Vol. 44, no 5, p. 1071-1093Article in journal (Refereed) Published
    Abstract [en]

    A highly selective impedance transformation filtering technique suitable for tunable selective RF receivers is proposed in this paper. To achieve blocker rejection comparable to SAW filters, we use a two stage architecture based on a low noise trans-conductance amplifier (LNTA). The filter rejection is captured by a linear periodically varying (LPV) model that includes band limitation by the LNTA output impedance and the related parasitic capacitances of the impedance transformation circuit. This model is also used to estimate “back folding” by interferers placed at harmonic frequencies. Discussed is also the effect of thermal noise folding and phase noise on the circuit noise figure. As a proof of concept a chip design of a tunable RF front-end using 65 nm CMOS technology is presented. In measurements the circuit achieves blocker rejection competitive to SAW filters with noise figure 3.2-5.2 dB,out of bandIIP3 > +17 dBm and blocker P1dB > +5 dBm over frequency range of 0.5—3 GHz.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2016
    Keywords
    SAW-less receiver; N-path filter; wideband selective RF front-end
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-122701 (URN)10.1002/cta.2125 (DOI)000376206000009 ()
    Available from: 2015-11-16 Created: 2015-11-16 Last updated: 2017-12-01Bibliographically approved
    8. Low Noise Transconductance  Amplifier Design for Continuous-Time Delta Sigma Wideband Frontend
    Open this publication in new window or tab >>Low Noise Transconductance  Amplifier Design for Continuous-Time Delta Sigma Wideband Frontend
    2011 (English)In: European Conference on Circuit Theory and Design (ECCTD), Linköping, Sweden: IEEE conference proceedings, 2011, p. 825-828Conference paper, Published paper (Refereed)
    Abstract [en]

    A low-noise transconductance amplifier (LNTA) aimed at continuous-time ΣΔ wideband frontend is presented. In this application, the LNTA operates with a capacitive load to provide high linearity and sufficient Gm gain over a wide frequency band. By combination of various circuit techniques the LNTA, which is designed in 65nm CMOS, achieves in simulation the noise figure less than 1.35 dB and linearity of maximum IIP3 = 13.6 dBm over 0.8 - 5 GHz band. The maximum transconductance Gm = 11.6 mS, the return loss S11 <; -14 dB while the total power consumption is 3.9 mW for 1.2 V supply.

    Place, publisher, year, edition, pages
    Linköping, Sweden: IEEE conference proceedings, 2011
    Keywords
    Low-noise transconductance amplifier (LNTA), continuous-time ΣΔ RF frontend, high linearity LNA, wideband LNA
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-73028 (URN)10.1109/ECCTD.2011.6043832 (DOI)978-1-4577-0617-2 (ISBN)978-1-4577-0616-5 (ISBN)
    Conference
    20th European Conference on Circuit Theory and Design, Linköping, 29-31 Aug. 2011
    Available from: 2011-12-14 Created: 2011-12-14 Last updated: 2016-01-18Bibliographically approved
    9. Highly linear open-loop output driver design for high speed capacitive DACs
    Open this publication in new window or tab >>Highly linear open-loop output driver design for high speed capacitive DACs
    2013 (English)In: 2013 NORCHIP, 11–12 November, 2013, Vilnius, LITHUANIA, 2013, p. 1-4Conference paper, Published paper (Refereed)
    Abstract [en]

    Design of a high speed output driver for capacitive digital-to-analog converters (SC DACs) is presented. As the output voltage swing of those DACs is usually greater than 300 mVpp the driver is designed for large signal operation that is a challenge in terms of the DAC linearity. Two non-linearity cancellation techniques are applied to the driver circuit, the derivative superposition (DS) and the resistive source degeneration resulting in HD3 <; -70 dB and HD2 <; -90 dB over the band of 0.5-4 GHz in 65-nm CMOS. For the output swing of 300 mVpp and 1.2 V supply its power consumption is 40 mW. For verification the driver is implemented in a 12-bit pipeline SC DAC. In simulations the complete Nyquist-rate DAC achieves SFDR of 64 dB for signal bandwidth up to 2.2 GHz showing a negligible non-linearity contribution by the designed driver for signal frequencies up to 1.3 GHz and a degradation by 3 dB at 2.2 GHz.

    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-102930 (URN)10.1109/NORCHIP.2013.6702039 (DOI)9781479916474 (ISBN)
    Conference
    31st Norchip Conference, 11-12 November 2013, Vilnius, Lithuania
    Available from: 2014-01-08 Created: 2014-01-08 Last updated: 2019-09-05Bibliographically approved
  • 104.
    Duong, Quoc-Tai
    et al.
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    Bhide, Ameya
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    A 1-GHz Bandwidth 12-bit SC DAC for 60-GHz Radio in 65-nm CMOSManuscript (preprint) (Other academic)
  • 105.
    Eamrurksiri, Techin
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Implementation and Analysis of Spectrum Sensing Algorithms for SIMO Links2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cognitive radio is an autonomous transceiver that is continuously sensing theongoing communication in its environment, it then starts the communication whenever it is appropriate. Therefore, cognitive radio helps improving the spectrum utilization of the overall communication system. However, without suitable spectrum sensing techniques, cognitive radio would fail. Hence, in this thesis we investigate and implement various spectrum sensing algorithms via software defined radio for both single antenna and multiple antenna cases. The main communi-cation scheme that we are using is OFDM. Moreover, both computer simulations and real-world measurements, have also been done for comparison and analysis ofthe detector’s performance. The detectors we are using are based on correlationfunction of the received signal and generalized likelihood ratio test with its eigen-value. The results from the simulations and measurements are then representedas probability of missed detection curves for different signal to noise ratios. Ourresults show that the performance of the generalized likelihood ratio test baseddetectors are at least 2 dB better than the correlation based detector in our mea-surement. Moreover, our simulations show that they are able to outperform thecorrelation function detector by more than 6 dB. Although, generalized likelihoodratio test based detectors seem to be better than the correlation function baseddetector, it requires more computational power which may limit its practical use.

  • 106.
    Ecker, Grit
    et al.
    INFORM GmbH, Germany.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Koster, Arie M. C. A.
    Rhein Westfal TH Aachen, Germany.
    Schmeink, Anke
    Rhein Westfal TH Aachen, Germany.
    Accurate optimization models for interference constrained bandwidth allocation in cellular networks2019In: Computers & Operations Research, ISSN 0305-0548, E-ISSN 1873-765X, Vol. 101Article in journal (Refereed)
    Abstract [en]

    In cellular networks, the signal-to-interference-plus-noise ratio (SINR) is a key metric for link availability and quality. For network planning purposes, a straightforward modeling unfortunately yields numerically difficult optimization models. Further, given a required data rate of a link, its bandwidth consumption depends nonlinearly on the SINR. In this paper, we develop two novel approaches to jointly model SINR-based link availability and bandwidth requirements accurately. The first approach is a set-wise formulation from a users point of view, while the second one exploits discrete channel quality indicators. We compare these formulations with three known approximate approaches numerically, revealing the clear outperformance of our approaches in terms of exactness. Moreover, since the exact models comprise an exponential number of either variables or constraints, we discuss their pros and cons in a further computational study and develop a more efficient algorithm dealing implicitly with the involved constraints. (C) 2018 Elsevier Ltd. All rights reserved.

    The full text will be freely available from 2021-08-22 11:09
  • 107.
    Egnell, Jakob
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Network usage profiling for applications on the Android smart phone2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Android, a platform for smartphones and mobile devices, is becoming more and more present in the market. Nevertheless, the battery runtime of smartphones is short and strongly influenced by the network usage. Some proposals exist to reduce the energy consumption associated to the network usage and increase the smartphone runtime. But for adjusting them for a real improvement it is required to study the network utilisation triggered by the smartphone applications. With this analysis the applications communication patterns can be obtained and used to predict the network usage and the amount of data expected.

    In order to gather network statistics of the running applications, a logger application is implemented for the Android platform to log network statistics of running applications. The statistics are analysed on a PC computer to obtain the applications' communication patterns. A number of applications are selected, sorted by the rankings of downloads and type. A detailed analysis of the network usage is presented. This analysis identifies some of their patterns, some application characteristics and groups of applications from the determined network usage. The network usages for applications with similar functionalities are compared and lessons learnt from the analysis are discussed. Finally, some improvements for our logger application and analysis are discussed.

  • 108.
    Ekman, Björn
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Machine Learning for Beam Based Mobility Optimization in NR2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One option for enabling mobility between 5G nodes is to use a set of area-fixed reference beams in the downlink direction from each node. To save power these reference beams should be turned on only on demand, i.e. only if a mobile needs it. An User Equipment (UE) moving out of a beam's coverage will require a switch from one beam to another, preferably without having to turn on all possible beams to find out which one is the best.

    This thesis investigates how to transform the beam selection problem into a format suitable for machine learning and how good such solutions are compared to baseline models. The baseline models considered were beam overlap and average Reference Signal Received Power (RSRP), both building beam-to-beam maps. Emphasis in the thesis was on handovers between nodes and finding the beam with the highest RSRP. Beam-hit-rate and RSRP-difference (selected minus best) were key performance indicators and were compared for different numbers of activated beams.

    The problem was modeled as a Multiple Output Regression (MOR) problem and as a Multi-Class Classification (MCC) problem. Both problems are possible to solve with the random forest model, which was the learning model of choice during this work. An Ericsson simulator was used to simulate and collect data from a seven-site scenario with 40 UEs. Primary features available were the current serving beam index and its RSRP. Additional features, like position and distance, were suggested, though many ended up being limited either by the simulated scenario or by the cost of acquiring the feature in a real-world scenario.

    Using primary features only, learned models' performance were equal to or worse than the baseline models' performance. Adding distance improved the performance considerably, beating the baseline models, but still leaving room for more improvements.

  • 109.
    Ericsson, Marcus
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Transmission, Storage, and Visualization of Data with ANT+2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Ultra low-powers wireless technology sensors uses when devices is used to consumeslow power. ANT+ sensors can run for years on a single coin battery. In thethesis the ANT+ sensor data is used in an application that can store and visualizethe data.

  • 110.
    Eriksson, Jonas
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Moosavi, Reza
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Complexity Reduction of Blind Decoding Schemes Using CRC Splitting2012In: 2012 IEEE Global Communications Conference (GLOBECOM), IEEE , 2012, p. 3731-3736Conference paper (Refereed)
    Abstract [en]

    Blind decoding, used on control channels of some multi-user wireless  access systems, is a technique for achieving adaptive modulation and  coding. The idea is to adapt the modulation and coding scheme to the  channel quality but instead of signaling the parameters used  explicitly, the receiver blindly tries a number of fixed parameter  combinations until a successful decoding attempt is detected, with  the help of a cyclic redundancy check. In this paper we suggest a  new method for reducing the complexity and energy consumption  associated with such blind decoding schemes. Our idea is to use a  mini-CRC injected early in the data stream to determine if the  current decoding attempt is using the correct modulation and coding  parameters. We analyze and exemplify the complexity gain of this  approach and also investigate the impact of the rearrangement of the  CRC scheme in terms of the probability of undetected error. The  presented results for the complexity gain are promising and the  impact on the error detection capability turns out to be small if  any.

  • 111.
    Eriksson, Marcus
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Analysis of Digital Predistortion in a Wideband Arbitrary Waveform Generator2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Digital predistortion is a signal processing technique used to remove undesired distortions caused by nonlinear system effects. This method is predominately used to linearize power amplifiers in communication systems in order to achieve efficient transmitter circuits. However, the technique can readily be applied to cancel undesired nonlinear behavior in other types of systems.

    This thesis investigates the effectiveness of digital predistortion in the context of a wideband arbitrary waveform generator. A theoretical foundation discussing nonlinear system models, predistortion architectures and system identification methods is complemented with a simulation study and followed by verification on a real system.

    The best predistorter is able to fully suppress the undesired distortions for any fixed two-tone sinusoidal signal. Furthermore, the results indicate the existence of a wideband predistorter which yield acceptable suppression over a frequency range of several hundred MHz.

  • 112.
    Eriksson, T.
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Körner, J.
    Bell Laboratories, Murray Hill, USA / Mathematical Institute of the Hungari an Academy of Sciences, Budapest, Hungary.
    Successive Encoding of Correlated Sources1982Report (Other academic)
    Abstract [en]

    The encoding of a discrete memoryless multiple source  for reconstruction of a sequence  with  is considered. We require that the encoding should be such that  is encoded first without any consideration of  , while in a seeond part of the encoding this latter sequence is encoded based on knowledge of the outcome of the first encoding. The resulting scheme is called successive encoding. We find general outer and inner bounds for the corresponding set of achievable rates along with a complete single letter characterization for the special case  . Comparisons with the Slepian-Wolf problem [3] and the Ahlswede-Körner-Wyner side information problem [2 ], [9) are carried out.

  • 113.
    Eriksson, Viktor
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Extraction of radio frequency quality metric from digital video broadcast streams by cable using software defined radio2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this master thesis was to investigate how effiecient the extractionof radiofrequency quality metrics from digital video broadcast (DVB) streamscan become using software defined radio. Software defined radio (SDR) is a fairlynew technology that offers you the possibility of very flexible receivers and transmitters where it is possible to upgrade the modulation and demodulation overtime.

    Agama is interested in SDR for use in the Agama Analyzer, a widely deployedmonitoring probe running on top of standard services. Using SDR, Agama coulduse that in all deployments, such as DVB by cable/terrestrial/satellite (DVBC/T/S), which would simplify logistics.

    This thesis is an implementation of a SDR to be able to receive DVB-C. TheSDR must perform a number of adaptive algorithms in order to prevent the received symbols from being significantly different from the transmitted ones. Themain parts of the SDR include timing recovery, carrier recovery and equalization.Timing recovery performs synchronization between the transmitted and receivedsymbols and the carrier recovery performs synchronization between the carrierwave of the transmitter and the local oscillator in the receiver. The thesis discusses various methods to perform the different types of synchronizations andequalizations in order to find the most suitable methods.

  • 114.
    Fahlborg, Daniel
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Measuring one-way Packet Delay in a Radio Network2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Radio networks are expanding, becoming more advanced, and pushing the limits of what is possible. Services utilizing the radio networks are also being developed in order to provide new functionality to end-users worldwide. When discussing 5G radio networks, concepts such as driverless vehicles, drones and near zero communication delay are recurrent. However, measures of delay are needed in order to verify that such services can be provided -- and measuring this is an extensive task. Ericsson has developed a platform for simulating a radio environment surrounding a radio base station. Using this simulator, this project involved measuring one-way packet delay in a radio network, and performing a Quality of Service evaluation of a radio network with a number of network applications in concern. Application data corresponding to video streams, or Voice over IP conversations, were simulated and packet delay measurements were used to calculate and evaluate the Quality of Service provided by a radio network. One of the main conclusions of this project was that packet delay variations are asymmetric in uplink, which suggests usage of non-conventional jitter measurement techniques.

  • 115.
    Fathi, Mohammad
    et al.
    University of Kurdistan.
    Karipidis, Eleftherios
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Distributed Resource Optimization in Multicell OFDMA Networks2012In: Proceedings of the IEEE Wireless Communications and Networking Conference (WCNC), IEEE , 2012, p. 1316-1320Conference paper (Refereed)
    Abstract [en]

    We consider the joint allocation of receiver, bit, and power to subcarriers in the downlink of multicell orthogonal frequency-division multiple-access (OFDMA) networks. Assuming that the cells share the entire bandwidth and that the rates are discrete, we formulate the joint allocation problem as a nonlinear mixed integer program (MIP), which however has exponential worst-case complexity. We capitalize on the capability of the receivers to measure the interference-plus-noise on every subcarrier and decompose the joint problem into a set of smaller-scale linear MIPs solved by individual base stations. Accordingly, we propose a distributed algorithm with linear complexity, in which the base stations participate in the problem solution in a round-robin manner. Simulation results demonstrate the effectiveness of the proposed algorithm in comparison with the iterative waterfilling algorithm and the successive optimal solution, by means of standard branch-and-cut solvers, of the individual MIPs.

  • 116.
    Faxén, Linnea
    Linköping University, Department of Electrical Engineering, Communication Systems.
    A Study on Segmentation for Ultra-Reliable Low-Latency Communications2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To enable wireless control of factories, such that sensor measurements can be sent wirelessly to an actuator, the probability to receive data correctly must be very high and the time it takes to the deliver the data from the sensor to the actuator must be very low. Earlier, these requirements have only been met by cables, but in the fifth generation mobile network this is one of the imagined use cases and work is undergoing to create a system capable of wireless control of factories. One of the problems in this scenario is when all data in a packet cannot be sent in one transmission while ensuring the very high probability of reception of the transmission. This thesis studies this problem in detail by proposing methods to cope with the problem and evaluating these methods in a simulator. The thesis shows that splitting the data into multiple segments and transmitting each at an even higher probability of reception is a good candidate, especially when there is time for a retransmission. When there is only one transmission available, a better candidate is to send the same packet twice. Even if the first packet cannot achieve the very high probability of reception, the combination of the first and second packet might be able to.

  • 117.
    Faxér, Sebastian
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Self-optimization of Antenna Sectorization2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sectorization is a well-established method of increasing the capacity of telecommunicationnetworks. With modern Active Antenna Systems (AAS) comes the abilityto change sectorization order dynamically, both in horizontal and vertical plane.The purpose of this thesis is to investigate when (and what type of) sectorizationis benficial. A theoretical analysis as well as simulations are performed in orderto determine which quantities to look at when making the decision to apply sectorization.Based on the conclusions from these investigations, a self-optimizingalgorithm that only turns on sectorization when it increases network performanceis developed and evaluated. It is shown that large gains can be achieved by onlyturning on sectorization when the right conditions are met. Further, we show thatadditional gains can be seen if antenna parameters such as downtilt and distributionof transmission power between sectors are set properly. Self-optimizingalgorithms for tuning of these parameters are developed and evaluated as well.NyckelordKeywords

  • 118.
    Fischer, Benjamin
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Vehicular Group Membership Resilient to Malicious Attacks2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    There is a range of tools and techniques in the realm of information security that can be used to enhance the security of a distributed network protocol and some of them introduce new problems. A security analysis of the distributed network protocol SLMP is made and three vulnerabilities are identified; messages can be intercepted and tampered with, nodes can fake id, and leader nodes can do a lot of harm if they are malicious. Three versions of SLMP that aims to remedy these vulnerabilities are implemented and the results show that while they remedy the vulnerabilities some of them introduce new problems. 

  • 119.
    Fontan, Angela
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Altafini, Claudio
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Modeling wireless power transfer in a network of smart devices: a compartmental system approach2018In: 2018 EUROPEAN CONTROL CONFERENCE (ECC), IEEE , 2018, p. 1468-1473Conference paper (Refereed)
    Abstract [en]

    Wireless power transfer technology provides a possible sustainable and cost-effective way to prolong indefinitely the lifetime of networks of smart devices needed in future Internet-of-Things, while equipping them with batteries of limited capacity. In this paper we show that the theory of compartmental systems, positive interconnected systems exchanging mass (here power) and ruled by mass conservation laws, provides a suitable framework to describe wireless power transfer networks. In particular we show that sustainability of the network of smart devices corresponds to each of them being alimented, directly or indirectly, by nodes having an external source of power, condition known as inflow connectivity in the compartmental systems literature. The framework allows to compute the topology which is optimal in terms of maximizing the overall efficiency of the power transfer.

  • 120.
    Fountoulakis, Emmanouil
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Performance Analysis and Optimization for Time Critical Networking2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Future communication systems will be characterized by heterogeneous traffic and requirements. Time critical applications like cyberphysical systems, augmented and virtual reality, raise the need for a low-latency based network. At the same time, conventional devices requiring for high throughput will co-exist with time critical applications. Besides the new technologies, new scheduling and optimization techniques are needed to face these challenges. 

    In this thesis, we investigate the issues arising from the deployment of these technologies. In Paper I, we explore the benefits of dynamic Transmission Time Interval (TTI) selection in a heterogeneous network environment. We consider packets with deadlines and we optimize jointly the TTI length and the channel allocation. After proving the NP-hardness of the problem, we propose a greedy algorithm taking decisions in polynomial time. The first work opens new questions regarding the deadline-constrained traffic such as how the minimum average drop rate can be achieved. In Paper II, we consider power-limited devices with deadline-constrained traffic. Lyapunov optimization methods are explored to solve the problem with time average objective and constraints. We develop a dynamic, polynomial time, algorithm that finds an approximation of the dropping rate minimization problem under average power constraints. 

    Besides the new techniques, future communication systems will require the development of new technologies for a more exible and elastic network. Multi-access Edge Computing (MEC) and Virtual Network Function (VNF) technologies are considered two of the key technologies for next generation networks. In Paper III, we analyze the performance of a network that hosts VNF and consists of MEC servers and servers at the core. As a first step, we consider a simple end-to-end communication system and provide analytical expressions for the end-to-end delay and system throughput by applying tools from queueing theory. Based on the first step, we provide the methodology for analyzing scaled-up systems with arbitrary number of servers. Simulation results show that our analytical model performs well. Furthermore, this work provides insights for the design and performance optimization of such systems such as optimal ow control and resource allocation.

    List of papers
    1. An Examination of the Benefits of Scalable TTI for Heterogeneous Traffic Management in 5G Networks
    Open this publication in new window or tab >>An Examination of the Benefits of Scalable TTI for Heterogeneous Traffic Management in 5G Networks
    Show others...
    2017 (English)In: 2017 15TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS NETWORKS (WIOPT), IEEE , 2017Conference paper, Published paper (Refereed)
    Abstract [en]

    The rapid growth in the number and variety of connected devices requires 5G wireless systems to cope with a very heterogeneous traffic mix. As a consequence, the use of a fixed transmission time interval (TTI) during transmission is not necessarily the most efficacious method when heterogeneous traffic types need to be simultaneously serviced. This work analyzes the benefits of scheduling based on exploiting scalable TTI, where the channel assignment and the TTI duration are adapted to the deadlines and requirements of different services. We formulate an optimization problem by taking individual service requirements into consideration. We then prove that the optimization problem is NP-hard and provide a heuristic algorithm, which provides an effective solution to the problem. Numerical results show that our proposed algorithm is capable of finding near-optimal solutions to meet the latency requirements of mission critical communication services, while providing a good throughput performance for mobile broadband services.

    Place, publisher, year, edition, pages
    IEEE, 2017
    Keywords
    5G; scalable TTI; deadline-constrained traffic; low latency; channel allocation; service-centric scheduler
    National Category
    Communication Systems
    Identifiers
    urn:nbn:se:liu:diva-142996 (URN)10.23919/WIOPT.2017.7959871 (DOI)000413806500010 ()978-3-9018-8290-6 (ISBN)
    Conference
    15th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt)
    Note

    Funding Agencies|European Unions Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant [643002]

    Available from: 2017-11-13 Created: 2017-11-13 Last updated: 2019-10-08
    2. Dynamic Power Control for Packets with Deadlines
    Open this publication in new window or tab >>Dynamic Power Control for Packets with Deadlines
    Show others...
    2018 (English)In: 2018 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), IEEE , 2018Conference paper, Published paper (Refereed)
    Abstract [en]

    Wireless devices need to adapt their transmission power according to the fluctuating wireless channel in order to meet constraints of delay sensitive applications. In this paper, we consider delay sensitivity in the form of strict packet deadlines arriving in a transmission queue. Packets missing the deadline while in the queue are dropped from the system. We aim at minimizing the packet drop rate under average power constraints. We utilize tools from Lyapunov optimization to find an approximate solution by selecting power allocation. We evaluate the performance of the proposed algorithm and show that it achieves the same performance in terms of packet drop rate with that of the Earliest Deadline First (EDF) when the available power is sufficient. However, our algorithm outperforms EDF regarding the trade-off between packet drop rate and average power consumption.

    Place, publisher, year, edition, pages
    IEEE, 2018
    Series
    IEEE Global Communications Conference, ISSN 2334-0983
    Keywords
    Deadline-constrained traffic; power efficient algorithms; Lyapunov optimization; centralized scheduler; dynamic algorithms
    National Category
    Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-158394 (URN)10.1109/GLOCOM.2018.8648124 (DOI)000465774306017 ()978-1-5386-4727-1 (ISBN)
    Conference
    IEEE Global Communications Conference (GLOBECOM)
    Note

    Funding Agencies|European Unions Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant [643002, 642743]; Center for Industrial Information Technology (CENIIT)

    Available from: 2019-06-28 Created: 2019-06-28 Last updated: 2019-10-08
  • 121.
    Fountoulakis, Emmanouil
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Liao, Qi
    Nokia Bell Labs, Germany.
    Suryaprakash, Vinay
    Nokia Bell Labs, Germany.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    An Examination of the Benefits of Scalable TTI for Heterogeneous Traffic Management in 5G Networks2017In: 2017 15TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS NETWORKS (WIOPT), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    The rapid growth in the number and variety of connected devices requires 5G wireless systems to cope with a very heterogeneous traffic mix. As a consequence, the use of a fixed transmission time interval (TTI) during transmission is not necessarily the most efficacious method when heterogeneous traffic types need to be simultaneously serviced. This work analyzes the benefits of scheduling based on exploiting scalable TTI, where the channel assignment and the TTI duration are adapted to the deadlines and requirements of different services. We formulate an optimization problem by taking individual service requirements into consideration. We then prove that the optimization problem is NP-hard and provide a heuristic algorithm, which provides an effective solution to the problem. Numerical results show that our proposed algorithm is capable of finding near-optimal solutions to meet the latency requirements of mission critical communication services, while providing a good throughput performance for mobile broadband services.

  • 122.
    Fowler, Scott
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Baravdish, George
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Formulation of Path Selection by means of maximum flow and minimum delay on a Free Space Optical Topology2016In: 2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    Wireless radio-frequency (RF) technologies has had universal wide-scale deployment. Despite this, the practical limitations of the RF spectrum being unable to meet the challenges (e.g. lack of security, high interference, limited bandwidth, scalability) of RF based communication networks have become increasingly apparent over the past decade. With the evergrowing of data heavy wireless communications, especially on the last mile (e.g. wireless mesh network) and the backbone, methods are required to help addresses the problem RF have been facing for the next generation network. Faced with such daunting obstacles in RF-only networks, the use of Free Space Optical (FSO) for wireless communications was proposed. FSO is a promising solution to security, limited spectrum bandwidth, the scalability problem of wireless mesh networks, but also the advantage of large transmission distance, free license, interference immunity, and high-bandwidth. Despite the major advantages of FSO technology, its widespread use has been hampered by atmospheric turbulence-induced fading. However, FSO is still consider to be a practical solution to RF challenges. To maximize the potential of FSO networks, we study the problem of maximum path resource flow for a route and minimum linear delay while the FSO topology under atmospheric turbulence. Such methods can be easy adopted to SDN to manage the data flow at the linkor network-layer.

  • 123.
    Fozooni, Milad
    et al.
    Queen's University of Belfast, North Ireland, UK.
    Matthaiou, Michail
    Queen's University of Belfast, North Ireland, UK.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Duong, Trung Q.
    Queen's University of Belfast, North Ireland, UK.
    Performance Limits of MIMO Systems with Nonlinear Power Amplifiers2015In: 2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), Institute of Electrical and Electronics Engineers (IEEE), 2015Conference paper (Refereed)
  • 124.
    Franco, Antonio
    et al.
    Lund University, Sweden.
    Fitzgerald, Emma
    Lund University, Sweden.
    Landfeldt, Björn
    Lund University, Sweden.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    LUPMAC: A Cross-Layer MAC Technique to Improve the Age of Information Over Dense WLANs2016In: 2016 23RD INTERNATIONAL CONFERENCE ON TELECOMMUNICATIONS (ICT), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    Age of Information (AoI) is a relatively new metric introduced to capture the freshness of a particular piece of information. While throughput and delay measurements are widely studied in the context of dense IEEE 802.11 Wireless LANs (WLANs), little is known in the literature about the AoI in this context. In this work we study the effects on the average AoI and its variance when a sensor node is immersed in a dense IEEE 802.11 WLAN. We also introduce a new cross layer MAC technique, called Latest UPdate MAC (LUPMAC), aimed at modifying the existing IEEE 802.11 in order to minimize the average AoI at the receiver end. This technique lets the MAC layer keep only the most up to date packets of a particular piece of information in the buffer. We show, through simulation, that this technique achieves significant advantages in the case of a congested dense IEEE 802.11 WLAN, and it is resilient to changes in the variance of the total network delay.

  • 125.
    Fransson, Emelie
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Driving behavior modeling and evaluation of merging control strategies - A microscopic simulation study on Sirat Expressway2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Bangkok is a city where the congestion levels have been a major problem for many years. In 2017, Bangkok was rated the most congested city in Asia, and the second most congested in the world. According to The Expressway Authority of Thailand (EXAT), on-ramp merging is one of the most critical problem that causes congestion on the urban expressways. EXAT have evaluated several merging control strategies through microscopic traffic simulation to find suitable strategies for implementation in real life. However, their simulation studies were all based on the assumption that all motorists strictly follow the traffic rules. This is not the actual case in Bangkok, where the drivers ignore both solid lines and striped areas, as well as utilize the shoulder lane on a regular basis. The aim of this thesis is to investigate if it is possible to include this complex driving behavior in existing microscopic simulation models. A second objective is to identify merging control strategies that can reduce the occurrence and the effects of this driving behavior in order to increase the throughput at an on-ramp area on Sirat Expressway. A model was built in VISSIM and calibrated based on data collected from video recordings. In the study, parameters that are significant for the driving behavior modeling, as well as the difficulties that arise from performing a realistic calibration of the model using video observations and model-specific constraints, are identified. From the video recordings it was discovered that the main problem causing the congestion was a result of the mainline traffic who traversed to the on-ramp. Two merging control strategies were suggested to address this problem: the installment of a center barrier, and successive merging areas. The results confirmed that both actions can improve the traffic situation in terms of reducing the individual travel time. Installing a center barrier was the most efficient option and reduced the travel time by 16.58 % on the mainline and 63.24 % at the on-ramp.

  • 126.
    Frostensson, Tomas
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Hardware Implementation and Assessment of a Soft MIMO Detector Based On SUMIS2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To allow faster and more reliable wireless communication a technique is to use multiple antennas in the transmitter and receiver. This technique is called MIMO. The usage of MIMO adds complexity to the receiver that must determine what the transmitter actually sent. This thesis focuses on hardware implementation suitable for an FPGA of a detection algorithm called SUMIS.

    A background to detection and SUMIS in particular is given as a theoretical aid for a better understanding of how an algorithm like this can be implemented. An introduction to hardware and digital design is also presented.

    A subset of the operations in the SUMIS algorithm such as matrix inversion and sum of logarithmic values are analyzed and suitable hardware architectures are presented. These operations are implemented in RTL hardware using VHDL targeted for an FPGA, Virtex-6 from Xilinx.

    The accuracy of the implemented operations is investigated showing promising results alongside of a presentation of the necessary resource usage.

    Finally other approaches to hardware implementation of detection algorithms are discussed and more suitable approaches for a future implementation of SUMIS are commented on. The key aspects are flexibility through software reprogrammability and area efficiency by designing a custom processor architecture. 

  • 127.
    Fuchs, Adel
    et al.
    Jerusalem Coll Technol, Israel.
    Stulman, Ariel
    Jerusalem Coll Technol, Israel.
    Gurtov, Andrei
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Hardening Opportunistic HIP2017In: PROCEEDINGS OF THE 20TH ACM INTERNATIONAL CONFERENCE ON MODELLING, ANALYSIS AND SIMULATION OF WIRELESS AND MOBILE SYSTEMS (MSWIM17), ASSOC COMPUTING MACHINERY , 2017, p. 123-127Conference paper (Refereed)
    Abstract [en]

    As mobile and multi-homed devices are becoming ubiquitous, the need for a dynamic, yet secure communication protocol is unavoidable. The Host Identity Protocol (HIP) was constructed to meet this requirement; to provide significantly more secure mobility and multi-homing capabilities. HIP opportunistic mode, which is to be used when other, more trusted mechanisms are lacking, is based on a leap of faith (LoF) paradigm. In this paper, we analyze different Man in the middle (MiTM) attacks which might occur under this LoF, and propose a set of tweaks for hardening opportunistic HIP (HOH) that strengthen opportunistic modes security.

  • 128.
    Gabry, Frédéric
    et al.
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Li, Nan
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Schrammar, Nicolas
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Girnyk, Maksym
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Karipidis, Eleftherios
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Thobaben, Ragnar
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Rasmussen, Lars K.
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Skoglund, Mikael
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Secure Broadcasting in Cooperative Cognitive Radio Networks2012In: Proceedings of the Future Network and Mobile Summit Conference, 2012Conference paper (Refereed)
  • 129.
    Gangula, Rajeev
    et al.
    Institut EURECOM.
    Gesbert, David
    Institut EURECOM.
    Lindblom, Johannes
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    On the Value of Spectrum Sharing among Operators in Multicell Networks2013In: Proceedings of the 77th IEEE Vehicular Technology Conference (VTC'13), IEEE , 2013, p. 1-5Conference paper (Refereed)
    Abstract [en]

    This work considers the benefits of allowing spectrum sharing among co-located wireless service providers operating in the same multicell network. Although spectrum sharing was shown to be valuable in some scenarios where the created interference can be eliminated, the benefits have not clearly shown for multicell networks with aggressive reuse. We explore this question and show that spectrum sharing is preferred for just a certain subset of the users defined by their distance from the serving bases, while beyond this distance, an orthogonal division of resources between operators gives better results. The claims are backed with theoretical analysis matching our simulations.

  • 130.
    Garcia, Nil
    et al.
    Chalmers, Sweden.
    Wymeersch, Henk
    Chalmers, Sweden.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Haimovich, Alexander M.
    New Jersey Institute Technology, NJ 07102 USA.
    Coulon, Martial
    University of Toulouse, France.
    Direct Localization for Massive MIMO2017In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 65, no 10, p. 2475-2487Article in journal (Refereed)
    Abstract [en]

    Large-scale MIMO systems are well known for their advantages in communications, but they also have the potential for providing very accurate localization, thanks to their high angular resolution. A difficult problem arising indoors and outdoors is localizing users over multipath channels. Localization based on angle of arrival (AOA) generally involves a two-step procedure, where signals are first processed to obtain a users AOA at different base stations, followed by triangulation to determine the users position. In the presence of multipath, the performance of these methods is greatly degraded due to the inability to correctly detect and/or estimate the AOA of the line-of-sight (LOS) paths. To counter the limitations of this two-step procedure which is inherently suboptimal, we propose a direct localization approach in which the position of a user is localized by jointly processing the observations obtained at distributed massive MIMO base stations. Our approach is based on a novel compressed sensing framework that exploits channel properties to distinguish LOS from non-LOS signal paths, and leads to improved performance results compared to previous existing methods.

  • 131.
    Garrido Gálvez, Mario
    et al.
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    Huang, Shen-Jui
    Novatek Corp, Taiwan.
    Chen, Sau-Gee
    National Chiao Tung University, Taiwan.
    Gustafsson, Oscar
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    The Serial Commutator FFT2016In: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 63, no 10, p. 974-978Article in journal (Refereed)
    Abstract [en]

    This brief presents a new type of fast Fourier transform (FFT) hardware architectures called serial commutator (SC) FFT. The SC FFT is characterized by the use of circuits for bit-dimension permutation of serial data. The proposed architectures are based on the observation that, in the radix-2 FFT algorithm, only half of the samples at each stage must be rotated. This fact, together with a proper data management, makes it possible to allocate rotations only every other clock cycle. This allows for simplifying the rotator, halving the complexity with respect to conventional serial FFT architectures. Likewise, the proposed approach halves the number of adders in the butterflies with respect to previous architectures. As a result, the proposed architectures use the minimum number of adders, rotators, and memory that are necessary for a pipelined FFT of serial data, with 100% utilization ratio.

  • 132.
    Geraci, Giovanni
    et al.
    Universitat Pompeu Fabra, Barcelona, Spain.
    Garcia-Rodriguez, Adrian
    Nokia Bell Labs, Dublin, Ireland.
    Galati Giordano, Lorenzo
    Nokia Bell Labs, Dublin, Ireland.
    Lopez-Perez, David
    Nokia Bell Labs, Dublin, Ireland.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Understanding UAV Cellular Communications: From Existing Networks to Massive MIMO2018In: IEEE Access, E-ISSN 2169-3536, Vol. 6, no 1, p. 67853-67865Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to bestow the reader with a timely study of UAV cellular communications, bridging the gap between the 3GPP standardization status quo and the more forward-looking research. Special emphasis is placed on the downlink command and control (C&C) channel to aerial users, whose reliability is deemed of paramount technological importance for the commercial success of UAV cellular communications. Through a realistic side-by-side comparison of two network deployments – a present-day cellular infrastructure versus a next-generation massive MIMO system – a plurality of key facts are cast light upon, with the three main ones summarized as follows: 1) UAV cell selection is essentially driven by the secondary lobes of a base station’s radiation pattern, causing UAVs to associate to far-flung cells; 2) over a 10 MHz bandwidth, and for UAV heights of up to 300 m, massive MIMO networks can support 100 kbps C&C channels in 74% of the cases when the uplink pilots for channel estimation are reused among base station sites, and in 96% of the cases without pilot reuse across the network; and 3) supporting UAV C&C channels can considerably affect the performance of ground users on account of severe pilot contamination, unless suitable power control policies are in place.

  • 133.
    Ghazanfari, Amin
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Power Control for Multi-Cell Massive MIMO2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The cellular network operators have witnessed significant growth in data traffic in the past few decades. This growth occurs due to the increases in the number of connected mobile devices, and further, the emerging mobile applications developed for rendering video-based on-demand services. As the frequency bandwidth for cellular communication is limited, significant effort was dedicated to improve the utilization of the available spectrum and increase the system performance via new technologies. For example, 3G and 4G networks were designed to facilitate high data traffic in cellular networks in past decades. Nevertheless, there is a necessity for new cellular network technologies to accommodate the ever-growing data traffic demand. 5G is behind the corner to deal with the tremendous data traffic requirements that will appear in cellular networks in the next decade.

    Massive MIMO (multiple-input-multi-output) is one of the backbone technologies in 5G networks. Massive MIMO originated from the concept of multi-user MIMO. It consists of base stations (BSs) implemented with a large number of antennas to increase the signal strengths via adaptive beamforming and concurrently serving many users on the same time-frequency blocks. As an outcome of using Massive MIMO technology, there is a notable enhancement of both sum spectral efficiency (SE) and energy efficiency (EE) in comparison with conventional MIMO based cellular networks. Resource allocation is an imperative factor to exploit the specified gains of Massive MIMO. It corresponds to properly allocating resources in the time, frequency, space, and power domains for cellular communication. Power control is one of the resource allocation methods to deliver high spectral and energy efficiency of Massive MIMO networks. Power control refers to a scheme that allocates transmit powers to the data transmitters such that the system maximizes some desirable performance metric.

    In the first part of this thesis, we investigate reusing the resources of a Massive MIMO system, for direct communication of some specific user pairs known as device-to-device (D2D) underlay communication. D2D underlay can conceivably increase the SE of traditional Massive MIMO systems by enabling more simultaneous transmissions on the same frequencies. Nevertheless, it adds additional mutual interference to the network. Consequently, power control is even more essential in this scenario in comparison with conventional Massive MIMO systems to limit the interference that is caused between the cellular network and the D2D communication, thereby enabling their coexistence. In this part, we propose a novel pilot transmission scheme for D2D users to limit the interference to the channel estimation phase of cellular users in comparison with the case of sharing pilot sequences for cellular and D2D users. We also introduce a novel pilot and data power control scheme for D2D underlaid Massive MIMO systems. This method aims at assuring that D2D communication enhances the SE of the network in comparison with conventional Massive MIMO systems.

    In the second part of this thesis, we propose a novel power control approach for multi-cell Massive MIMO systems. The new power control approach solves the scalability issue of two well-known power control schemes frequently used in the Massive MIMO literature, which are based on the network-wide max-min and proportional fairness performance metrics. We first explain the scalability issue of these existing approaches. Additionally, we provide mathematical proof for the scalability of our proposed method. Our scheme aims at maximizing the geometric mean of the per-cell max-min SE. To solve this optimization problem, we prove that it can be rewritten in a convex form and then be solved using standard optimization solvers.

    List of papers
    1. Optimized Power Control for Massive MIMO With Underlaid D2D Communications
    Open this publication in new window or tab >>Optimized Power Control for Massive MIMO With Underlaid D2D Communications
    2019 (English)In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, no 4, p. 2763-2778Article in journal (Refereed) Published
    Abstract [en]

    In this paper, we consider device-to-device (D2D) communication that is underlaid in a multi-cell massive multiple-input multiple-output (MIMO) system and proposes a new framework for power control and pilot allocation. In this scheme, the cellular users (CUs) in each cell get orthogonal pilots which are reused with reuse factor one across cells, while all the D2D pairs share another set of orthogonal pilots. We derive a closed-form capacity lower bound for the CUs with different receive processing schemes. In addition, we derive a capacity lower bound for the D2D receivers and a closed-form approximation of it. We provide power control algorithms to maximize the minimum spectral efficiency (SE) and to maximize the product of the signal-to-interference-plus-noise ratios in the network. Different from prior works, in our proposed power control schemes, we consider joint pilot and data transmission optimization. Finally, we provide a numerical evaluation, where we compare our proposed power control schemes with the maximum transmit power case and the case of conventional multi-cell massive MIMO without D2D communication. Based on the provided results, we conclude that our proposed scheme increases the sum SE of multi-cell massive MIMO networks.

    Place, publisher, year, edition, pages
    IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
    Keywords
    MIMO systems; power control; optimization methods; interference suppression
    National Category
    Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-157237 (URN)10.1109/TCOMM.2018.2890240 (DOI)000465242700012 ()
    Note

    Funding Agencies|European Unions Horizon 2020 research and innovation programme [641985]

    Available from: 2019-06-13 Created: 2019-06-13 Last updated: 2019-10-07
  • 134.
    Gundlegård, David
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Transport Analytics Based on Cellular Network Signalling Data2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cellular networks of today generate a massive amount of signalling data. A large part of this signalling is generated to handle the mobility of subscribers and contains location information that can be used to fundamentally change our understanding of mobility patterns. However, the location data available from standard interfaces in cellular networks is very sparse and an important research question is how this data can be processed in order to efficiently use it for traffic state estimation and traffic planning.

    In this thesis, the potentials and limitations of using this signalling data in the context of estimating the road network traffic state and understanding mobility patterns is analyzed. The thesis describes in detail the location data that is available from signalling messages in GSM, GPRS and UMTS networks, both when terminals are in idle mode and when engaged in a telephone call or a data session. The potential is evaluated empirically using signalling data and measurements generated by standard cellular phones. The data used for analysis of location estimation and route classification accuracy (Paper I-IV in the thesis) is collected using dedicated hardware and software for cellular network analysis as well as tailor-made Android applications. For evaluation of more advanced methods for travel time estimation, data from GPS devices located in Taxis is used in combination with data from fixed radar sensors observing point speed and flow on the road network (Paper V). To evaluate the potential in using cellular network signalling data for analysis of mobility patterns and transport planning, real data provided by a cellular network operator is used (Paper VI).

    The signalling data available in all three types of networks is useful to estimate several types of traffic data that can be used for traffic state estimation as well as traffic planning. However, the resolution in time and space largely depends on which type of data that is extracted from the network, which type of network that is used and how it is processed.

    The thesis proposes new methods based on integrated filtering and classification as well as data assimilation and fusion that allows measurement reports from the cellular network to be used for efficient route classification and estimation of travel times. The thesis also shows that participatory sensing based on GPS equipped smartphones is useful in estimating radio maps for fingerprint-based positioning as well as estimating mobility models for use in filtering of course trajectory data from cellular networks.

    For travel time estimation, it is shown that the CEP-67 location accuracy based on the proposed methods can be improved from 111 meters to 38 meters compared to standard fingerprinting methods. For route classification, it is shown that the problem can be solved efficiently for highway environments using basic classification methods. For urban environments the link precision and recall is improved from 0.5 and 0.7 for standard fingerprinting to 0.83 and 0.92 for the proposed method based on particle filtering with integrity monitoring and Hidden Markov Models.

    Furthermore, a processing pipeline for data driven network assignment is proposed for billing data to be used when inferring mobility patterns used for traffic planning in terms of OD matrices, route choice and coarse travel times. The results of the large-scale data set highlight the importance of the underlying processing pipeline for this type of analysis. However, they also show very good potential in using large data sets for identifying needs of infrastructure investment by filtering out relevant data over large time periods.

    List of papers
    1. The Smartphone As Enabler for Road Traffic Information Based on Cellular Network Signalling
    Open this publication in new window or tab >>The Smartphone As Enabler for Road Traffic Information Based on Cellular Network Signalling
    2013 (English)In: Intelligent Transportation Systems (ITSC), 2013, IEEE , 2013, p. 2106-2112Conference paper, Published paper (Refereed)
    Abstract [en]

    The higher penetration rate of GPS-enabled smartphones together with their improved processing power and battery life makes them suitable for a number of participatory sensing applications. The purpose of this paper is to analyse how GPS-enabled smartphones can be used in a participatory sensing context to build a radio map for RSS-based positioning, with a special focus on road traffic information based on cellular network signalling. The CEP-67 location accuracy achieved is 75 meters for both GSM and UMTS using Bayesian classification. For this test site, the accuracy is similar for GSM and UMTS, with slightly better results for UMTS in the CEP-95 error metric. The location accuracy achieved is good enough to avoid large errors in travel time estimation for highway environments, especially considering the possibility to filter out estimates with low accuracy using for example the posterior bin probability in Bayesian classification. For urban environments more research is required to determine how the location accuracy will affect the path inference problem in a dense road network. The location accuracy achieved in this paper is also sufficient for other traffic information types, for example origin-destination estimation based on location area updates.

    Place, publisher, year, edition, pages
    IEEE, 2013
    National Category
    Engineering and Technology Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-102022 (URN)10.1109/ITSC.2013.6728540 (DOI)978-147992914-6 (ISBN)
    Conference
    16th International IEEE Conference on Intelligent Transportation Systems (ITSC 2013), 6-9 October 2013, The Hague, Netherlands
    Available from: 2013-11-26 Created: 2013-11-26 Last updated: 2018-11-15
    2. Handover location accuracy for travel time estimation in GSM and UMTS
    Open this publication in new window or tab >>Handover location accuracy for travel time estimation in GSM and UMTS
    2009 (English)In: IET Intelligent Transport Systems, ISSN 1751-956X, E-ISSN 1751-9578, Vol. 3, no 1, p. 87-94Article in journal (Refereed) Published
    Abstract [en]

    Field measurements from the GSM and UMTS networks are analysed in a road traffic information context. The measurements indicate a potentially large improvement using UMTS signalling data compared with GSM regarding handover location accuracy. These improvements can be used to generate real-time traffic information with higher quality and extend the geographic usage area for cellular-based travel time estimation systems. The results con. rm previous reports indicating that the technology has a large potential in GSM and also show that the potential might be even larger and more. exible using UMTS. Assuming that non-vehicle terminals can be. ltered out, that vehicles are tracked to the correct route and that handovers can be predicted correctly, a conclusion from the experiments is that the handover location accuracy in both GSM and UMTS will be sufficient to estimate useful travel times, also in urban environments. In a real system, these tasks are typically very challenging, especially in an urban environment. Further, it is reasonably established that the location error will be minor for the data obtained from UMTS.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-16517 (URN)10.1049/iet-its:20070067 (DOI)
    Available from: 2013-04-05 Created: 2009-01-30 Last updated: 2018-11-15Bibliographically approved
    3. Route Classification in Travel Time Estimation Based on Cellular Network Signaling
    Open this publication in new window or tab >>Route Classification in Travel Time Estimation Based on Cellular Network Signaling
    2009 (English)In: Proceedings of 12th International IEEE Conference on Intelligent Transport Systems (ITSC), October 3-7, St. Louis, USA, 2009, p. 474-479Conference paper, Published paper (Refereed)
    Abstract [en]

    Travel time estimation based on cellular network signaling is a promising technology for delivery of wide area travel times in real-time. The technology has received much attention recently, but few academic research reports has so far been published in the area, which together with uncertain location estimates and environmental dependent performance makes it difficult to assess the potential of the technology. This paper aims to investigate the route classification task in a cellular travel time estimation context in detail. In order to estimate the magnitude of the problem, two classification algorithms are developed, one based on nearest neighbor classification and one based on Bayesian classification. These are then evaluated using field measurements from the GSM network. A conclusion from the results is that the route classification problem is not trivial even in a highway environment, due to effects of multipath propagation and changing radio environment. In a highway environment the classification problem can be solved rather efficiently using e.g., one of the methods described in this paper, keeping the effect on travel time accuracy low. However, in order to solve the route classification task in urban environments more research is required.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-50949 (URN)10.1109/ITSC.2009.5309692 (DOI)978-1-4244-5520-1 (ISBN)978-1-4244-5519-5 (ISBN)
    Conference
    12th International IEEE Conference on Intelligent Transport Systems (ITSC), October 3-7, St. Louis, USA
    Available from: 2013-04-05 Created: 2009-10-15 Last updated: 2018-11-15Bibliographically approved
    4. Travel Time and Point Speed Fusion Based on a Macroscopic Traffic Model and Non-linear Filtering
    Open this publication in new window or tab >>Travel Time and Point Speed Fusion Based on a Macroscopic Traffic Model and Non-linear Filtering
    Show others...
    2015 (English)In: 2015 IEEE 18th International Conference on Intelligent Transportation Systems, IEEE conference proceedings, 2015, p. 2121-2128Conference paper, Published paper (Refereed)
    Abstract [en]

    The number and heterogeneity of traffic sensors are steadily increasing. A large part of the emerging sensors are measuring point speeds or travel times and in order to make efficient use of this data, it is important to develop methods and frameworks for fusion of point speed and travel time measurements in real-time. The proposed method combines a macroscopic traffic model and a non-linear filter with a new measurement model for fusion of travel time observations in a system that uses the velocity of cells in the network as state vector. The method aims to improve the fusion efficiency, especially when travel time observations are relatively long compared to the spatial resolution of the estimation framework. The method is implemented using the Cell Transmission Model for velocity (CTM-v) and the Ensemble Kalman Filter (EnKF) and evaluated with promising results in a test site in Stockholm, Sweden, using point speed observations from radar and travel time observations from taxis.

    Place, publisher, year, edition, pages
    IEEE conference proceedings, 2015
    Series
    IEEE International Conference on Intelligent Transportation Systems-ITSC, ISSN 2153-0009
    Keywords
    Cell Transmisson Model, Data fusion, Ensemble Kalman Filtering, Traffic state estimation
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-129376 (URN)10.1109/ITSC.2015.343 (DOI)000376668802033 ()978-1-4673-6595-6 (ISBN)
    Conference
    2015 IEEE 18th International Conference on Intelligent Transportation Systems. 15-18 Sept. 2015, Las Palmas
    Available from: 2016-06-17 Created: 2016-06-17 Last updated: 2018-11-15Bibliographically approved
    5. Travel demand estimation and network assignment based on cellular network data
    Open this publication in new window or tab >>Travel demand estimation and network assignment based on cellular network data
    2016 (English)In: COMPUTER COMMUNICATIONS, ISSN 0140-3664, Vol. 95, p. 29-42Article in journal (Refereed) Published
    Abstract [en]

    Cellular networks signaling data provide means for analyzing the efficiency of an underlying transportation system and assisting the formulation of models to predict its future use. This paper describes how signaling data can be processed and used in order to act as means for generating input for traditional transportation analysis models. Specifically, we propose a tailored set of mobility metrics and a computational pipeline including trip extraction, travel demand estimation as well as route and link travel flow estimation based on Call Detail Records (CDR) from mobile phones. The results are based on the analysis of data from the Data for development "D4D" challenge and include data from Cote dlvoire and Senegal. (C) 2016 Elsevier B.V. All rights reserved.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE BV, 2016
    Keywords
    Mobility analytics; Travel demand estimation; Traffic modeling; Mobile phone call data; Cellular network data; Call detail records; Intelligent transport systems
    National Category
    Computer Engineering
    Identifiers
    urn:nbn:se:liu:diva-134086 (URN)10.1016/j.comcom.2016.04.015 (DOI)000390722300004 ()
    Note

    Funding Agencies|Swedish Governmental Agency for Innovation Systems (VINNOVA)

    Available from: 2017-01-26 Created: 2017-01-22 Last updated: 2018-11-19
  • 135.
    Gunnarsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology. Ericsson Research, Linköping, Sweden.
    Lindsten, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Carlsson, N.
    Ericsson Research, Linköping, Sweden; Volvo Cars, Gothanburg, Sweden.
    Particle filtering for network-based positioning terrestrial radio networks2014In: Data Fusion & Target Tracking 2014: Algorithms and Applications (DF&TT 2014), IET Conference on, Institution of Engineering and Technology , 2014, Vol. 2014, no 629 CPConference paper (Refereed)
    Abstract [en]

    There is strong interest in positioing in wireless networks, partly to support end user service needs, but also to support network management with network-based network information. The focus in this paper is on the latter, while using measurements that are readily available in wireless networks. We show how thesignal direction of departure and inter-distance between the base station and the mobile terminal can be estimated, and how particle filters and smoothers can be used to post-process the measurements. The methods are evaluated in a live 3GPP LTE network with promising results inlcuding position error medians of less than 100 m.

  • 136.
    Gurtov, Andrei
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Liyanage, Madhusanka
    Centre for Wireless Communications, University of Oulu, Finland.
    Korzun, Dmitry
    Petrozavodsk State University, Petrozavodsk, Kareliya Republits, Russia.
    Secure Communication and Data Processing Challenges in the Industrial Internet2016In: Baltic Journal of Modern Computing, ISSN 2255-8942, E-ISSN 2255-8950, Vol. 4, no 4, p. 1058-1073Article in journal (Refereed)
    Abstract [en]

    The next industrial revolution is foreseen to happen with upcoming Industrial Internet that combines massive data collected by industrial sensors with data analysis for improving the efficiency of operations. Collecting, pre-processing, storing and analyzing such real-time data is a complex task with stringent demands on communication intelligence, QoS and security. In this paper we outline some challenges facing the Industrial Internet, namely integration with 5G wireless networks, Software Defined Machines, ownership and smart processing of digital sensor data. We propose a secure communication architecture for the Industrial Internet based on Smart Spaces and Virtual Private LAN Services. It is a position paper, describing state-of-the-art and a roadmap for future research on the Industrial Internet.

  • 137.
    Gustafsson, Magnus
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory.
    Lightweight M2M Solution on Android Platform2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Machine-to-machine communication (M2M) is a generic term for technologies dealing with autonomous communication between machines. For the last 10 years a wide range of business areas utilize a variety of different M2M solutions for remote management of equipment. Common for almost all of those solutions is that they are expensive and require the infrastructure to be adapted to them. They are also usually built out of several different systems working together and thus there are several systems that require maintenance.

    This thesis investigates the possibility to develop a lightweight alternative to existing M2M solutions using only common devices and protocols. Lightweight here means that the system should be flexible, have a low cost for set-up and operation and that both ends should be mobile. By developing a lightweight M2M architecture the technology may become available in new business areas and new types of services may arise. 

    In the thesis a prototype is implemented. The purpose of the prototype is to practically verify whether a lightweight M2M solution is possible to develop in this manner. The solution uses the Android platform for back-end and user interface and a Cinterion TC65T as slave device to which the sensors can be connected. The implemented system is limited in terms of security and performance but still acts as a proof of concept for this kind of M2M solution.

  • 138.
    Gustafsson, Oscar
    et al.
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    Bertilsson, Erik
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    Klasson, Johannes
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    Ingemarsson, Carl
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    Approximate Neumann Series or Exact Matrix Inversion for Massive MIMO? (Invited Paper)2017In: Proceedings 2017 IEEE 24th Symposium on Computer Arithmetic (ARITH), London, UK, 24-26 July 2017 / [ed] Neil Burgess, Javier Bruguera, and Florent de Dinechin, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 62-63Conference paper (Refereed)
    Abstract [en]

    Approximate matrix inversion based on Neumann series has seen a recent increased interest motivated by massive MIMO systems. There, the matrices are in many cases diagonally dominant, and, hence, a reasonable approximation can be obtained within a few iterations of a Neumann series. In this work, we clarify that the complexity of exact methods are about the same as when three terms are used for the Neumann series, so in this case, the complexity is not lower as often claimed. The second common argument for Neumann series approximation, higher parallelism, is indeed correct. However, in most current practical use cases, such a high degree of parallelism is not required to obtain a low latency realization. Hence, we conclude that a careful evaluation, based on accuracy and latency requirements must be performed and that exact matrix inversion is in fact viable in many more cases than the current literature claims.

  • 139.
    Haque, Muhammad Fahim Ul
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    Pulse-Width Modulated RF Transmitters2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The market for wireless portable devices has grown signicantly over the recent years.Wireless devices with ever-increased functionality require high rate data transmissionand reduced costs. High data rate is achieved through communication standards such asLTE and WLAN, which generate signals with high peak-to-average-power ratio (PAPR),hence requiring a power amplier (PA) that can handle a large dynamic range signal. Tokeep the costs low, modern CMOS processes allow the integration of the digital, analogand radio functions on to a single chip. However, the design of PAs with large dynamicrange and high eciency is challenging due to the low voltage headroom.

    To prolong the battery life, the PAs have to be power-ecient as they consume a sizablepercentage of the total power. For LTE and WLAN, traditional transmitters operatethe PA at back-o power, below their peak efficiency, whereas pulse-width modulation(PWM) transmitters use the PA at their peak power, resulting in a higher efficiency.PWM transmitters can use both linear and SMPAs where the latter are more power efficient and easy to implement in nanometer CMOS. The PWM transmitters have a higher efficiency but suffer from image and aliasing distortion, resulting in a lower dynamic range,amplitude and phase resolution.

    This thesis studies several new transmitter architectures to improve the dynamicrange, amplitude and phase resolution of PWM transmitters with relaxed filtering requirements.The architectures are suited for fully integrated CMOS solutions, in particular forportable applications.

    The first transmitter (MAF-PWMT) eliminates aliasing and image distortions whileallowing the use of SMPAs by combining RF-PWM and band-limited PWM. The transmittercan be implemented using all-digital techniques and exhibits an improved linearity and spectral performance. The approach is validated using a Class-D PA based transmitter where an improvement of 10.2 dB in the dynamic range compared to a PWM transmitter for a 1.4 MHz of LTE signal is achieved.

    The second transmitter (AC-PWMT) compensates for aliasing distortion by combining PWM and outphasing. It can be used with switch-mode PAs (SMPAs) or linear PAs at peak power. The proposed transmitter shows better linearity, improved spectral performanceand increased dynamic range as it does not suffer from AM-AM distortion of the PAs and aliasing distortion due to digital PWM. The idea is validated using push-pull PAs and the proposed transmitter shows an improvement of 9 dB in the dynamic rangeas compared to a PWM transmitter using digital pulse-width modulation for a 1.4 MHzLTE signal.

    The third transmitter (MD-PWMT) is an all-digital implementation of the second transmitter. The PWM is implemented using a Field Programmable Gate Array(FPGA) core, and outphasing is implemented as pulse-position modulation using FPGA transceivers, which drive two class-D PAs. The digital implementation offers the exibility to adapt the transmitter for multi-standard and multi-band signals. From the measurement results, an improvement of 5 dB in the dynamic range is observed as compared to an all-digital PWM transmitter for a 1.4 MHz LTE signal.

    The fourth transmitter (EP-PWMT) improves the phase linearity of an all-digital PWM transmitter using PWM and asymmetric outphasing. The transmitter uses PWM to encode the amplitude, and outphasing for enhanced phase control thus doubling the phase resolution. The measurement setup uses Class-D PAs to amplify a 1.4 MHz LTEup-link signal. An improvement of 2.8 dB in the adjacent channel leakage ratio is observed whereas the EVM is reduced by 3.3 % as compared to an all-digital PWM transmitter.

    The fifth transmitter (CRF-ML-PWMT) combines multilevel and RF-PWM, whereas the sixth transmitter (CRF-MP-PMWT) combines multiphase PWM and RF-PWM. Both transmitters have smaller chip area as compared to the conventional multiphase and multilevel PWM transmitters, as a combiner is not required. The proposed transmitters also show better dynamic range and improved amplitude resolution as compared to conventional RF-PWM transmitters.

    The solutions presented in this thesis aims to enhance the performance and simplify the digital implementation of PWM-based RF transmitters.

    List of papers
    1. Combined RF and Multilevel PWM Switch Mode Power Amplifier
    Open this publication in new window or tab >>Combined RF and Multilevel PWM Switch Mode Power Amplifier
    2013 (English)In: Norchip Conference, IEEE , 2013, p. 1-4Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper presents a novel power amplifier (PA) architecture based on the combination of radio frequency pulse width modulation (RFPWM) and multilevel PWM. The architecture provides better dynamic range at high carrier frequency compared to RFPWM. The benefits of this architecture over multilevel PWM are that it only requires a single PA and no combiner. The average efficiency for an 802.11g baseband signal is better than multilevel PWM. Our results also shows that the proposed technique exhibit a constant dynamic range at carrier frequency of 3, 4 and 5 GHz, in contrast to RFPWM which shows a decrease in dynamic range for increase in carrier frequency.

    Place, publisher, year, edition, pages
    IEEE, 2013
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-102929 (URN)10.1109/NORCHIP.2013.6702010 (DOI)978-1-4799-1647-4 (ISBN)
    Conference
    NORCHIP 2013; NOV 11-12, 2013, Vilnius, Lithuania
    Available from: 2014-01-08 Created: 2014-01-08 Last updated: 2019-01-04
    2. Combined RF and Multiphase PWM Transmitter
    Open this publication in new window or tab >>Combined RF and Multiphase PWM Transmitter
    2015 (English)In: 2015 European Conference on Circuit Theory and Design (ECCTD), IEEE , 2015, p. 264-267Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper presents two novel transmitter architectures based on the combination of radio-frequency pulse-width modulation and multiphase pulse-width modulation. The proposed transmitter architectures provide good amplitude resolution and large dynamic range at high carrier frequency, which is problematic with existing radio-frequency pulse-width modulation based transmitters. They also have better power efficiency and smaller chip area compared to multiphase pulse-width modulation based transmitters.

    Place, publisher, year, edition, pages
    IEEE, 2015
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-122703 (URN)10.1109/ECCTD.2015.7299999 (DOI)000380498200001 ()978-1-4799-9877-7 (ISBN)
    Conference
    2015 European Conference on Circuit Theory and Design (ECCTD), Trondheim, Norway, August 24-26, 2015
    Available from: 2015-11-16 Created: 2015-11-16 Last updated: 2017-01-18Bibliographically approved
  • 140.
    He, Qing
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Revisiting Optimal Link Activation and Minimum-Time Scheduling in Wireless Networks2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    With the popularity of wireless communications in the last two decades, data traffic is exponentially increasing and requests high speed transmission. However, the resources, in particular, spectrum and energy, are limited. Therefore, network optimization with the objective of utilizing radio resource as efficiently as possible is crucial to the sustainable development of wireless communications.

    Link activation and scheduling are two classic problems of access coordination and resource allocation for multiple links that share a common channel. The problems originate from the broadcast nature of wireless media and are of significance in more complicated cross-layer optimization problems. Although there is a rich amount of literature, the problems remain challenging and are extended by novel setups incorporating new interference management technologies.

    In this thesis, we revisit these two fundamental problems with the main methods of mathematical modelling and applied optimization. The first two papers address the scheduling problem that amounts to emptying a given amount of data in minimum time. We derive theoretical insights including problem complexity, optimality conditions, as well as problem approximation and algorithmic framework, in general and for a class of networks with a particular structure. In the third paper, we incorporate cooperative transmission and interference cancellation with maximum link activation. Theoretical results and algorithm development are provided. Simulation study shows the new setup brings significant performance gain in comparison with the conventional approach.

    List of papers
    1. Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework
    Open this publication in new window or tab >>Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework
    2014 (English)In: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 60, no 2, p. 1083-1100Article in journal (Refereed) Published
    Abstract [en]

    We consider a set of transmitter-receiver pairs, or links, that share a wireless medium and address the problem of emptying backlogged queues with given initial size at the transmitters in minimum time. The problem amounts to determining activation subsets of links, and their time durations, to form a minimum-time schedule. Scheduling in wireless networks has been studied under various formulations before. In this paper, we present fundamental insights and solution characterizations that include: 1) showing that the complexity of the problem remains high for any continuous and increasing rate function; 2) formulating and proving sufficient and necessary optimality conditions of two baseline scheduling strategies that correspond to emptying the queues using one-at-a-time or all-at-once strategies; and 3) presenting and proving the tractability of the special case in which the transmission rates are functions only of the cardinality of the link activation sets. These results are independent of physical-layer system specifications and are valid for any form of rate function. We then develop an algorithmic framework for the solution to this problem. The framework encompasses exact as well as sub-optimal, but fast, scheduling algorithms, all under a unified principle design. Through computational experiments, we finally investigate the performance of several specific algorithms from this framework.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2014
    Keywords
    Algorithm; optimality; scheduling; wireless networks
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-104836 (URN)10.1109/TIT.2013.2292065 (DOI)000330286100022 ()
    Available from: 2014-02-28 Created: 2014-02-28 Last updated: 2018-08-14
    2. Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks
    Open this publication in new window or tab >>Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks
    2016 (English)In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 3, no 3, p. 322-331Article in journal (Other academic) Published
    Abstract [en]

    We consider a wireless network with a set of transmitter-receiver pairs, or links, that share a common channel, and address the problem of emptying finite traffic volume from the transmitters in minimum time. This, so called, minimum-time scheduling problem has been proved to be NP-hard in general. In this paper, we study a class of minimum-time scheduling problems in which the link rates have a particular structure. We show that global optimality can be reached in polynomial time and derive optimality conditions. Then we consider a more general case in which we apply the same approach and obtain an approximation as well as lower and upper bounds to the optimal solution. Simulation results confirm and validate our approach.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2016
    Keywords
    algorithm, interference, optimality, scheduling, wireless networks
    National Category
    Communication Systems Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-112446 (URN)10.1109/TCNS.2015.2512678 (DOI)000384701100010 ()
    Note

    At the time for thesis presentation publication was in status: Manuscript

    Available from: 2014-11-27 Created: 2014-11-27 Last updated: 2019-07-15Bibliographically approved
    3. Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks
    Open this publication in new window or tab >>Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks
    2017 (English)In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 16, no 2, p. 408-421Article in journal (Refereed) Published
    Abstract [en]

    We address the maximum link activation problem in wireless networks with new features, namely when the transmitters can perform cooperative transmission, and the receivers are able to perform successive interference cancellation. In this new problem setting, which transmitters should transmit and to whom, as well as the optimal cancellation patterns at the receivers, are strongly intertwined. We present contributions along three lines. First, we provide a thorough tractability analysis, proving the NP-hardness as well as identifying tractable cases. Second, for benchmarking purposes, we deploy integer linear programming for achieving global optimum using off-theshelf optimization methods. Third, to overcome the scalability issue of integer programming, we design a sub-optimal but efficient optimization algorithm for the problem in its general form, by embedding maximum-weighted bipartite matching into local search. Numerical results are presented for performance evaluation, to validate the benefit of cooperative transmission and interference cancellation for maximum link activation and to demonstrate the effectiveness of the proposed algorithm.

    Place, publisher, year, edition, pages
    IEEE, 2017
    National Category
    Communication Systems Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-112447 (URN)10.1109/TMC.2016.2546906 (DOI)000393808500009 ()
    Conference
    2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), September 2-5, Washington DC, DC, USA
    Note

    Funding agencies: Swedish Research Council; EU FP7 Marie Curie [324515, 329313]; National Science Foundation [CCF-0728966, CCF-1420651]; ONR [N000141410107]

    Available from: 2014-11-27 Created: 2014-11-27 Last updated: 2018-08-14Bibliographically approved
  • 141.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks2016In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 3, no 3, p. 322-331Article in journal (Other academic)
    Abstract [en]

    We consider a wireless network with a set of transmitter-receiver pairs, or links, that share a common channel, and address the problem of emptying finite traffic volume from the transmitters in minimum time. This, so called, minimum-time scheduling problem has been proved to be NP-hard in general. In this paper, we study a class of minimum-time scheduling problems in which the link rates have a particular structure. We show that global optimality can be reached in polynomial time and derive optimality conditions. Then we consider a more general case in which we apply the same approach and obtain an approximation as well as lower and upper bounds to the optimal solution. Simulation results confirm and validate our approach.

  • 142.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Department of Electrical and Computer Engineering, University of Maryland, USA.
    Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks2017In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 16, no 2, p. 408-421Article in journal (Refereed)
    Abstract [en]

    We address the maximum link activation problem in wireless networks with new features, namely when the transmitters can perform cooperative transmission, and the receivers are able to perform successive interference cancellation. In this new problem setting, which transmitters should transmit and to whom, as well as the optimal cancellation patterns at the receivers, are strongly intertwined. We present contributions along three lines. First, we provide a thorough tractability analysis, proving the NP-hardness as well as identifying tractable cases. Second, for benchmarking purposes, we deploy integer linear programming for achieving global optimum using off-theshelf optimization methods. Third, to overcome the scalability issue of integer programming, we design a sub-optimal but efficient optimization algorithm for the problem in its general form, by embedding maximum-weighted bipartite matching into local search. Numerical results are presented for performance evaluation, to validate the benefit of cooperative transmission and interference cancellation for maximum link activation and to demonstrate the effectiveness of the proposed algorithm.

  • 143.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Ephremides, Anthony
    Univ Maryland, MD 20742 USA.
    Optimal Link Scheduling for Age Minimization in Wireless Systems2018In: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 64, no 7, p. 5381-5394Article in journal (Refereed)
    Abstract [en]

    Information age is a recently introduced metric to represent the freshness of information in communication systems. We investigate age minimization in a wireless network and propose a novel approach of optimizing the scheduling strategy to deliver all messages as fresh as possible. Specifically, we consider a set of links that share a common channel. The transmitter at each link contains a given number of packets with time stamps from an information source that generated them. We address the link transmission scheduling problem with the objective of minimizing the overall age. This minimum age scheduling problem (MASP) is different from minimizing the time or the delay for delivering the packets in question. We model the MASP mathematically and prove it is NP-hard in general. We also identify tractable cases as well as optimality conditions. An integer linear programming formulation is provided for performance benchmarking. Moreover, a steepest age descent algorithm with better scalability is developed. Numerical study shows that, by employing the optimal schedule, the overall age is significantly reduced in comparison to other scheduling strategies.

  • 144.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD 20742 USA.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. University of Maryland, MD 20742 USA.
    Optimizing Freshness of Information: On Minimum Age Link Scheduling in Wireless Systems2016In: 2016 14TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS NETWORKS (WIOPT), IEEE , 2016, p. 115-122Conference paper (Refereed)
    Abstract [en]

    There is a growing interest in age of information, which is a newly introduced metric that measures the freshness of information in communication systems. We investigate the age of information in wireless networks and propose the novel approach of optimizing the scheduling strategy to deliver the information as timely as possible. We consider a set of links that share a common channel, each containing a number of packets with time stamps, and address the scheduling problem with the objective of minimizing the overall information age. We model this problem mathematically and prove it is NP-hard in general. Fundamental insights including tractable cases and optimality conditions are presented. An integer linear programming formulation is provided for performance benchmarking. Moreover, a steepest age decent algorithm with better scalability is developed. Numerical study shows that, by employing the optimal schedule, the overall information age is significantly reduced in comparison to other scheduling strategies.

  • 145.
    Helders, Fredrik
    Linköping University, Department of Electrical Engineering, Communication Systems.
    Visualizing Carrier Aggregation Combinations2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As wireless communications is becoming an increasingly important part of ourevery day lives, the amount of transmitted data is constantly growing, creating ademand for ever-increasing data rates. One of the technologies used for boostingdata rates is carrier aggregation, which allows for wireless units to combine multipleconnections to the cellular network. However, there is a limited number ofpossible combinations defined, meaning that there is a need to search for the bestcombination in any given setup. This thesis introduces software capable of organizingthe defined combinations into tree structures, simplifying the search foroptimal combinations as well as allowing for visualizations of the connectionspossible. In the thesis, a proposed method of creating these trees is presented,together with suggestions on how to visualize important combination characteristics.Studies has also been made on different tree traversal algorithms, showingthat there is little need for searching through all possible combinations, but thata greedy approach has a high performance while substantially limiting the searchcomplexity.

  • 146.
    Hiran, Rahul
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Shahmehri, Nahid
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Crowd-based Detection of Routing Anomalies on the Internet2015In: Proc. IEEE Conference on Communications and Network Security (IEEE CNS), Florence, Italy, Sept. 2015., IEEE Computer Society Digital Library, 2015, p. 388-396Conference paper (Refereed)
    Abstract [en]

    The Internet is highly susceptible to routing attacks and there is no universally deployed solution that ensures that traffic is not hijacked by third parties. Individuals or organizations wanting to protect themselves from sustained attacks must therefore typically rely on measurements and traffic monitoring to detect attacks. Motivated by the high overhead costs of continuous active measurements, we argue that passive monitoring combined with collaborative information sharing and statistics can be used to provide alerts about traffic anomalies that may require further investigation. In this paper we present and evaluate a user-centric crowd-based approach in which users passively monitor their network traffic, share information about potential anomalies, and apply combined collaborative statistics to identify potential routing anomalies. The approach uses only passively collected round-trip time (RTT) measurements, is shown to have low overhead, regardless if a central or distributed architecture is used, and provides an attractive tradeoff between attack detection rates (when there is an attack) and false alert rates (needing further investigation) under normal conditions. Our data-driven analysis using longitudinal and distributed RTT measurements also provides insights into detector selection and the relative weight that should be given to candidate detectors at different distances from the potential victim node.

  • 147.
    Hiran, Rahul
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Shahmehri, Nahid
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Does Scale, Size, and Locality Matter?: Evaluation of Collaborative BGP Security Mechanisms2016In: 2016 IFIP NETWORKING CONFERENCE (IFIP NETWORKING) AND WORKSHOPS, IEEE , 2016, p. 261-269Conference paper (Refereed)
    Abstract [en]

    The Border Gateway Protocol (BGP) was not designed with security in mind and is vulnerable to many attacks, including prefix/subprefix hijacks, interception attacks, and imposture attacks. Despite many protocols having been proposed to detect or prevent such attacks, no solution has been widely deployed. Yet, the effectiveness of most proposals relies on largescale adoption and cooperation between many large Autonomous Systems (AS). In this paper we use measurement data to evaluate some promising, previously proposed techniques in cases where they are implemented by different subsets of ASes, and answer questions regarding which ASes need to collaborate, the importance of the locality and size of the participating ASes, and how many ASes are needed to achieve good efficiency when different subsets of ASes collaborate. For our evaluation we use topologies and routing information derived from real measurement data. We consider collaborative detection and prevention techniques that use (i) prefix origin information, (ii) route path updates, or (iii) passively collected round-trip time (RTT) information. Our results and answers to the above questions help determine the effectiveness of potential incremental rollouts, incentivized or required by regional legislation, for example. While there are differences between the techniques and two of the three classes see the biggest benefits when detection/prevention is performed close to the source of an attack, the results show that significant gains can be achieved even with only regional collaboration.

  • 148.
    Hossain, M. M. Aftab
    et al.
    Aalto Univ, Finland; KTH Royal Inst Technol, Sweden.
    Cavdar, Cicek
    KTH Royal Inst Technol, Sweden.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Jantti, Riku
    Aalto Univ, Finland.
    Energy Saving Game for Massive MIMO: Coping With Daily Load Variation2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 3, p. 2301-2313Article in journal (Refereed)
    Abstract [en]

    Massive MIMO (MM) is one of the leading technologies that can cater for very high capacity demand. However, energy consumption of MM systems needs to be load adaptive in order to cope with the significant temporal load variations (TLV) over a day. In this paper, we propose a game-theoretic model for studying load adaptive multicell massive MIMO system where each base station (BS) adapts the number of antennas to the TLV in order to maximize the downlink energy efficiency (EE). The utility function considered here is defined as the number of bits transferred per Joule of energy. In order to incorporate the TLV, the load at each BS is modeled as an M/G/m/m state dependent queue under the assumption that the network is dimensioned to serve a maximum number of users at the peak load. The EE maximization problem is formulated in a game theoretic framework where the number of antennas to be used by a BS is determined through the best response iteration. This load adaptive system achieves around 24% higher EE and saves around 40% energy compared to a baseline system where the BSs always run with the fixed number of antennas that is most energy efficient at the peak load and that can be switched OFF when there is no traffic.

  • 149.
    Hossain, M. M. Aftab
    et al.
    Aalto University, Finland.
    Cavdar, Cicek
    KTH Royal Institute of Technology, Sweden.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Jäntti, Riku
    Aalto University, Finland.
    Energy-Efficient Load-Adaptive Massive MIMO2015In: 2015 IEEE GLOBECOM WORKSHOPS (GC WKSHPS), 2015Conference paper (Refereed)
  • 150.
    Hoymann, Christian
    et al.
    Ericsson Research, Sweden; Ericssons 3GPP RAN Delegat, Sweden.
    Astely, David
    Nokia Networks, Sweden; Ericsson, Sweden.
    Stattin, Magnus
    Ericsson Research, Sweden.
    Wikstrom, Gustav
    Ericsson Research, Sweden.
    (Thomas) Cheng, Jung-Fu
    Ericsson Silicon Valley, Sweden.
    Hoglund, Andreas
    Ericsson Research, Sweden.
    Frenne, Mattias
    Ericsson, Sweden.
    Blasco, Ricardo
    Ericsson Research, Sweden.
    Huschke, Joerg
    Ericsson GmbH, Germany.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering. Ericsson Research, Sweden.
    LTE Release 14 Outlook2016In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 54, no 6, p. 44-49Article in journal (Refereed)
    Abstract [en]

    Todays 4G LTE systems bring unprecedented mobile broadband performance to over a billion of users across the globe. Recently, work on a 5G mobile communication system has begun, and next to a new 5G air interface, LTE will be an essential component. The evolution of LTE will therefore strive to meet 5G requirements and to address 5G use cases. In this article, we provide an overview of foreseen key technology areas and components for LTE Release 14, including latency reductions, enhancements for machine-type communication, operation in unlicensed spectrum, massive multi-antenna systems, broadcasting, positioning, and support for intelligent transportation systems.

1234567 101 - 150 of 496
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf