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  • 1.
    Alissa, S.
    et al.
    Swedish Mapping Cadastral and Land Registration Authority, Sweden.
    Håkansson, M.
    Swedish Mapping Cadastral and Land Registration Authority, Sweden.
    Henkel, P.
    ANavS GmbH, Germany.
    Mittmann, U.
    ANavS GmbH, Germany.
    Huffmeier, Johannes
    RISE Research Institutes of Sweden.
    Rylander, Robert
    RISE Research Institutes of Sweden, Safety and Transport, Safety.
    Low bandwidth network-rtk correction dissemination for high accuracy maritime navigation2021In: TransNav, International Journal on Marine Navigation and Safety of Sea Transportation, ISSN 2083-6473, E-ISSN 2083-6481, Vol. 15, no 1, p. 171-179Article in journal (Refereed)
    Abstract [en]

    More than half of the incidents reported to EMSA relate to nautical events such as collision, groundings and contacts. Knowledge of accurate and high-integrity positioning is therefore not only a need for future automated shipping but a base for today’s safe navigation. Examples on accidents include Ever Given in the Suez Canal and HNoMS Helge Ingstad in Norway. A Network-RTK (NRTK) service can be used as an augmentation technique to improve performance of shipborne GNSS receivers for future positioning of manned and unmanned vessels in restricted areas, such as port areas, fairways, and inland water ways. NRTK service providers generate RTK corrections based on the observations of networks of GNSS reference stations which enables the users to determine their position with centimeter accuracy in real-time using a shipborne GNSS receiver. Selection of appropriate communication channels for dissemination of NRTK corrections data is the key to a secure positioning (localization) service. In PrePare-Ships project, the modern maritime communication system VDES (VHF Data Exchange System) is proposed to distribute SWEPOS (NRTK in Sweden) correction data to shipborne positioning modules. VDES is a very reliable technique and it is compatible with most onboard functionalities. In order to minimize the impact on the overall VDES data capacity in a local area, NRTK correction data shall only occupy a single VDES slot with a net capacity of 650 bytes. Update rates may vary but are preferably at 1Hz. However, NRTK correction data size changes instantly, depending on the number of visible GNSS satellites, and the data rate can therefore sometimes reach in excess of 1000 byte/s. In this study, a smart technique is proposed to reduce size of NRTK correction data to instantly adapt with the VDES requirements by choosing a combination of specific signals, satellites or even constellations such that the data rate is not more than 650 byte/s, and at the same time it achieves optimal positioning performance with the accuracy required by the PrePare-Ships project application. 

  • 2.
    Alissa, S.
    et al.
    Lantmäteriet, Sweden.
    Håkansson, M.
    Lantmäteriet, Sweden.
    Rieck, Carsten
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Dutta, Uttama
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Nord, Stefan
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Bergljung, P.
    Saab TransponderTech, Sweden.
    Bagge, A.
    Saab TransponderTech, Sweden.
    Distribution of the adapted-NRTK correction data via VDES for the shipping navigation safety2021In: Proceedings of the 34th International Technical Meeting of the Satellite Division of the Institute of Navigation, ION GNSS+ 2021, Institute of Navigation , 2021, p. 521-534Conference paper (Refereed)
    Abstract [en]

    In this study the maritime communication system VDES (VHF Data Exchange System) is proposed to distribute Network-RTK (NRTK) correction data to shipborne GNSS receivers in fairways, port areas, or inland water ways. The transport layer used for transmission of VDES messages (related to the standard IEC61162-450) is the UDP multicast protocol. This makes it possible to transmit the RTCM packages from the VDES transponder to the shipborne GNSS receivers as a UDP payload without any additional formatting. In order to minimize the impact on the overall VDES data capacity in a local service area, NRTK correction data shall at most occupy a single VDES slot with a net capacity of 650 bytes denoted Link ID 19. This is the fastest link in VDES. Update rates may vary but are preferably at 1Hz. However, depending on the number of visible satellites NRTK correction data size changes instantly and the data rate can therefore sometimes be in excess of 1000 byte/s per reference station to be distributed. In order to comply with the VDES requirements, the Lantmäteriet Adjustment Solution (LAS) for GNSS correction data adjustment was developed and is presented in this paper. The responsibility of this solution is to produce a correction data stream that complies with the bandwidth limitation of 650 bytes/s. To provide corrections for a potentially large number of users, dissemination is done by broadcasting corrections for a grid of VRSs. The proposed solution has therefore also the capability to combine several correction data streams from several Virtual Reference Stations (VRSs) into one single correction data stream. To reduce the required data rate, the LAS has the ability to filter streamed GNSS correction data in the RTCM3 MSM format constellation-wise, satellite-wise, and signal-wise. The objective is to achieve optimal performance in terms of accuracy for the ship's differential positioning solution, while at the same time adhering to constraints that might locally apply for individual transmitters. For this paper LAS was configured to interface with the SWEPOS to provide reference data to static and kinematic testing scenarios. The results presented here were obtained using RTK post-processing with RTKLib for a combination of GPS and Galileo multi-frequency observations. Results indicated that LAS solution can achieve robust positioning performance with decimeter-level accuracy which meet the requirements expected for the navigation safety at Sea. Adapted-NRTK correction data (LAS data) via VDES has the potential to be part of a world-wide standard VDES application for all vessels sailing under SOLAS and for ships that voluntarily uses VDES in the near future (inland, yachts, navies, leisure).

  • 3.
    Brunnström, Kjell
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Djupsjöbacka, Anders
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Andrén, Börje
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Objective video quality assessment methods for Video assistant refereeing (VAR) Systems2021Report (Other academic)
    Abstract [en]

    This report describes the work and conclusions drawn after phase 4 in the project “Assessment methods for Video assistant refereeing (VAR) System”.

    The performance of six different video quality models have been evaluated, that were identified during phase 1, against the subjective video quality database that was created during phase 3. The results are slightly different for 1080p compared to 1080i. For 1080p the models VQM_VFD, SSIM and VMAF performs the best with Pearson Correlation Coefficients (PCC) above 0.9. For 1080i the PCC drops a bit overall and then VMAF and VQM_VFD are close in performance and performing the best. The overall performance for both formats VMAF an VQM_VFD stands out as the best models. In this comparison VQM_VFD has the added advantage to also be able to perform its own registration i.e. to fix any misalignment between the reference video and the distorted one.

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  • 4.
    Brunnström, Kjell
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Djupsjöbacka, Anders
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Andrén, Börje
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Video quality based on a user study with video professionals for Video Assisted Refereeing (VAR) Systems2021Report (Other academic)
    Abstract [en]

    This document describes a user experiment with the purpose of finding a baseline quality that is suitable for system and a database for training and evaluating the objective quality measurement methods suitable for assessing the video quality of VAR systems. 

    A user experiment was performed involving 25 Swedish video experts. Three different video formats were incorporated 1080p, 1080i and 540i. The degradations were in most cased done using encoding with Motion JPEG (MJPEG) and H.264 in the bitrate range from 80 Mbit/s down to 10 Mbit/s. 

    MJPEG loses quality very fast and already at 80 Mbit/s it has significantly lower quality than the uncompressed reference and then for even lower bitrates the quality falls quickly to bad. On the other hand, H.264 was not found to be significant different from the uncompressed reference until the bitrate had dropped to 10 Mbit/s for 1080p. For 1080i 20 Mbit/s was also weakly and for 540i 20 Mbit/s was significantly lower for some of the scaling methods. For 1080i the deinterlacing requires careful consideration, since the deinterlacing scheme introduced received very low quality scores. For the scaling scheme lanczos was the best and bilinear the worst. 

    Requirement levels on bitrate and the encoders MJPEG and H.264 based on this experiment•    MJPEG require more than 120 Mbit/s•    H.264 require more than 50 Mbit/s

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  • 5.
    Chong, Z.
    et al.
    Dresden University of Technology, Germany.
    Mochaourab, Rami
    Dresden University of Technology, Germany.
    Jorswieck, Eduard
    Dresden University of Technology, Germany.
    Pricing in Noncooperative Interference Channels for Improved Energy Efficiency2010In: EURASIP Journal on Wireless Communications and Networking, Vol. 2010Article in journal (Refereed)
    Abstract [en]

    We consider noncooperative energy-efficient resource allocation in the interference channel. Energy efficiency is achieved when each system pays a price proportional to its allocated transmit power. In noncooperative game-theoretic notation, the power allocation chosen by the systems corresponds to the Nash equilibrium. We study the existence and characterize the uniqueness of this equilibrium. Afterwards, pricing to achieve energy-efficiency is examined. We introduce an arbitrator who determines the prices that satisfy minimum QoS requirements and minimize total power consumption. This energy-efficient assignment problem is formulated and solved. We compare our setting to that without pricing with regard to energy-efficiency by simulation. It is observed that pricing in this distributed setting achieves higher energy-efficiency indifferent interference regimes.

  • 6.
    Dutta, Uttama
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Rieck, Carsten
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Håkansson, M.
    Lantmäteriet, Sweden.
    Gerbeth, D.
    German Aerospace Center, Germany.
    Alissa, S.
    Lantmäteriet, Sweden.
    Nord, Stefan
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Satellite selection in the context of network RTK for limited bandwidth applications2021In: Proceedings of the 34th International Technical Meeting of the Satellite Division of the Institute of Navigation, ION GNSS+ 2021, Institute of Navigation , 2021, p. 2474-2492Conference paper (Refereed)
    Abstract [en]

    The increasing number of modernized GNSS signals and the availability of multi-constellation receivers are crucial for improvements of both precision and robustness of GNSS based positioning. However, the abundance of GNSS observations is not always useable as applications, using differential positioning or other techniques, may have limitations with respect to computational resources or communication bandwidth for reference data, and therefore require a qualified selection of a subset of observations for positioning. This paper is based on the work conducted in the project PREParE SHIPS funded by the European Union Agency for the Space Programme (EUSPA) on the specific application of Maritime Navigation using Network Real Time Kinematic (NRTK) and will focus on the satellite selection algorithms of the Prepare Ships dissemination solution. This study is motivated by data rate requirements and restrictions of the VDES dissemination solution developed in Prepare Ships. The restricted data rate for dissemination of RTK observations via VDES implies the need for a qualified pre-selection of satellite subsets to match the available bandwidth and the requirements of the positioning system. For this, multiple algorithms have been developed and tested in static and dynamic scenarios. Optimization techniques for height (for vertical position), two and three dimensions were examined. Different weighting schemes were used. During the evolution of the satellite selection study, it was concluded that it is necessary to retain satellites with the highest elevation as this will empirically improve integer ambiguity resolution for position fixing. Also fixing a minimum number of satellites for each constellation was required to enable a fair weightage to the different constellations used. Such algorithms should prove to be very useful for research on various Network RTK applications which require/prefer limited bandwidth such as for cadastral surveying and mapping, for airborne geo-referencing of aerial mapping data using Unmanned Aerial Vehicles (UAV) and on the road and sea for positioning and navigation of automated transport. Additionally, these algorithms could also be extended to consider satellite visibility in e.g. urban areas (i.e. urban canyons) by inclusion of true surface information for more robust GNSS positioning in automated transport applications [1]. This could either be for pre-evaluation or for dynamically considering spatial information. While this work is a part of PREParE SHIPS, it is also motivated by a more general applicability of the algorithms presented for other similar applications. RTK correction dissemination with limited bandwidth requirements is very promising for RTK research and therefore this study on optimized selection of satellite subsets is of vital importance and could tap multiple opportunities of huge potential such as those involving NRTK or combination of Precise Point Positioning with RTK. © 2021 Proceedings of the 34th International Technical Meeting of the Satellite Division of the Institute of Navigation, ION GNSS+ 2021. 

  • 7.
    Englund, Cristofer
    et al.
    RISE, Swedish ICT, Viktoria.
    Kovaceva, Jordanka
    Volvo, Sweden.
    Lindman, Magdalena
    Volvo, Sweden.
    Grönvall, John-Fredrik
    Volvo, Sweden.
    Using random forests for data mining data and drowsy driver classification using FOT data2012In: Proceedings of On the Move to Meaningful Internet Systems: OTM 2012, 2012, Vol. 5766, p. 748-758Conference paper (Refereed)
    Abstract [en]

    Data mining techniques based on Random forests are explored to gain knowledge about data in a Field Operational Test (FOT) database. We compare the performance of a Random forest, a Support Vector Machine and a Neural network used to separate drowsy from alert drivers. 25 variables from the FOT data was utilized to train the models. It is experimentally shown that the Random forest outperforms the other methods while separating drowsy from alert drivers. It is also shown how the Random forest can be used for variable selection to find a subset of the variables that improves the classification accuracy. Furthermore it is shown that the data proximity matrix estimated from the Random forest trained using these variables can be used to improve both classification accuracy, outlier detection and data visualization.

  • 8.
    Englund, Cristofer
    et al.
    RISE, Swedish ICT, Viktoria.
    Nilsson, Maria
    RISE, Swedish ICT, Viktoria.
    Voronov, Alexey
    RISE, Swedish ICT, Viktoria.
    The application of data mining techniques to model visual distraction of bicyclists2016In: Expert systems with applications, ISSN 0957-4174, E-ISSN 1873-6793, Vol. 52, p. 99-107Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel approach to modelling visual distraction of bicyclists. A unique bicycle simulator equipped with sensors capable of capturing the behaviour of the bicyclist is presented. While cycling two similar scenario routes, once while simultaneously interacting with an electronic device and once without any electronic device, statistics of the measured speed, head movements, steering angle and bicycle road position along with questionnaire data are captured. These variables are used to model the self-assessed distraction level of the bicyclist. Data mining techniques based on random forests, support vector machines and neural networks are evaluated for the modelling task. Out of the total 71 measured variables a variable selection procedure based on random forests is able to select a fraction of those and consequently improving the modelling performance. By combining the random forest-based variable selection and support vector machine-based modelling technique the best overall performance is achieved. The method shows that with a few observable variables it is possible to use machine learning to model, and thus predict, the distraction level of a bicyclist.

  • 9.
    Englund, Cristofer
    et al.
    RISE, Swedish ICT, Viktoria.
    Verikas, Antanas
    Halmstad University, Sweden; Kaunas University of Technology, Lithuania.
    A novel approach to estimate proximity in a random forest: An exploratory study2012In: Expert systems with applications, ISSN 0957-4174, E-ISSN 1873-6793, Vol. 39, no 17, p. 13046-13050Article in journal (Refereed)
    Abstract [en]

    A data proximity matrix is an important information source in random forests (RF) based data mining, including data clustering, visualization, outlier detection, substitution of missing values, and finding mislabeled data samples. A novel approach to estimate proximity is proposed in this work. The approach is based on measuring distance between two terminal nodes in a decision tree. To assess the consistency (quality) of data proximity estimate, we suggest using the proximity matrix as a kernel matrix in a support vector machine (SVM), under the assumption that a matrix of higher quality leads to higher classification accuracy. It is experimentally shown that the proposed approach improves the proximity estimate, especially when RF is made of a small number of trees. It is also demonstrated that, for some tasks, an SVM exploiting the suggested proximity matrix based kernel, outperforms an SVM based on a standard radial basis function kernel and the standard proximity matrix based kernel.

  • 10.
    Han, M.
    et al.
    Beijing Jiaotong University, China.
    Wang, M.
    Beijing Jiaotong University, China.
    Fan, Yuchuan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Cai, S.
    Beijing Jiaotong University, China.
    Guo, Y.
    Beijing Jiaotong University, China.
    Zhang, N.
    Beijing Jiaotong University, China.
    Schatz, Rickard
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Simultaneous modulation format identification and OSNR monitoring based on optoelectronic reservoir computing2022In: Optics Express, E-ISSN 1094-4087, Vol. 30, no 26, p. 47515-47527Article in journal (Refereed)
    Abstract [en]

    An approach for simultaneous modulation format identification (MFI) and optical signal-to-noise ratio (OSNR) monitoring in digital coherent optical communications is proposed based on optoelectronic reservoir computing (RC) and the signal’s amplitude histograms (AHs) obtained after the adaptive post-equalization. The optoelectronic RC is implemented using a Mach-Zehnder modulator and optoelectronic delay feedback loop. We investigate the performance of the proposed model with the number of symbols, bins of AHs and the hyperparameters of optoelectronic RC. The results show that 100% MFI accuracy can be achieved simultaneously with accurate OSNR estimation for different modulation formats under study. The lowest achievable OSNR estimation mean absolute errors for the dual-polarization (DP)-quadrature phase-shift keying signal, the DP-16-ary quadrature amplitude modulation (16QAM) signal, and the DP-64QAM signal are 0.2 dB, 0.32 dB and 0.53 dB, respectively. The robustness of the proposed scheme is also evaluated when the optoelectronic RC is in presence of additive white Gaussian noises. Then, a proof of concept experiment is demonstrated to further verify our proposed method. The proposed approach offers a potential solution for next-generation intelligent optical performance monitoring in the physical layer.

  • 11. Haunstein, Herbert
    et al.
    Rohde, Harald
    Forzati, Marco
    Pincemin, Erwan
    Mårtensson, Jonas
    Djupsjöbacka, Anders
    RISE, Swedish ICT, Acreo.
    Politi, Tanya
    Combating Physical Layer Degradations: Chapter 62010In: Core and Metro Networks / [ed] Alexandros Stavdas, 2010, p. 381-Chapter in book (Other academic)
  • 12.
    Jorswieck, E.
    et al.
    Dresden University of Technology, Germany.
    Mochaourab, Rami
    Dresden University of Technology, Germany.
    Power Control Game in Protected and Shared Bands: Manipulability of Nash Equilibrium2009Conference paper (Refereed)
    Abstract [en]

    We consider a downlink resource allocation problem for two systems or cells each consisting of a base station and multiple mobile stations. Each cell operates on a protected band for exclusive use and a band shared with the other cell. On simultaneous transmission in the shared band, the two systems disturb one another with interference. The strategies of the systems are their choices of power allocations in their two bands with regard to individual sum power constraints. Here, the conflict present between the systems is best analyzed using game theory. In the first part, we study the static non-cooperative power control game with complete information. Existence and uniqueness of the Nash equilibrium are examined. Based on a suitable feedback model, we ask in the second part, whether the Nash equilibrium can be manipulated by reporting untruthful information within the system. The aim is to find suitable functions to suppress false feedback information from giving advantage to the dishonest system and degrading fairness between the systems. Here, we apply results from mechanism design to propose a modified expected payoff function at the mobile stations to force truthful feedback.

  • 13.
    Jorswieck, E.
    et al.
    Dresden University of Technology, Germany.
    Mochaourab, Rami
    Dresden University of Technology, Germany.
    Secrecy Rate Region of MISO Interference Channel: Pareto Boundary and Non-Cooperative Games2009Conference paper (Refereed)
    Abstract [en]

    Competition in interference channels is modeled using noncooperative game theory. The well known Nash equilibrium often leads to inefficient solutions. In the current work,we study the achievable secrecy rate of a multiple-antenna(MISO) interference channel (IFC). First, we characterizethe Pareto boundary of the secrecy rate region. Next, theparameterization is exploited to compute the Nash equilibrium. In contrast to the usual case in which the rate is considered as utility function, the Nash outcome is not maximum ratio transmission (MRT), it depends on the SNR andthe channel realizations and it can be shown to be almostefficient at all SNR values. All results are illustrated bysample region plots, reaction curves, and average price ofanarchy figures.

  • 14.
    Kakkar, Aditya
    et al.
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Louchet, Hadrien
    VPIphotonics GmBH, Germany.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    A path to use large linewidth LO in 28 Gbd 16-QAM metro links2015In: 2015 European Conference on Optical Communication (ECOC), 2015, article id 7341948Conference paper (Refereed)
    Abstract [en]

    We experimentally investigate the possibility to mitigate local oscillator induced Equalization Enhanced Phase Noise penalty. The results pave the way for the use of even 10 MHz linewidth local oscillator lasers in 28 Gbd 16-QAM metro links.

  • 15.
    Kaline P., Furlan
    Hamburg University, Germany.
    Diaz, Ana (Contributor)
    Paul Scherrer Institut, Switzerland.
    Holler, Mirko (Contributor)
    Paul Scherrer Institut, Switzerland.
    Krekeler, Tobias (Contributor)
    Hamburg University of Technology, Germany.
    Ritter, Martin (Contributor)
    Hamburg University of Technology, Germany.
    Petrov, Alexander Yu. (Contributor)
    Hamburg University of Technology, Germany; ITMO University, Russia.
    Eich, Manfred (Contributor)
    Hamburg University of Technology, Germany.
    Blick, Robert (Contributor)
    Hamburg University of Technology, Germany.
    Schneider, Gerold A. (Contributor)
    Hamburg University of Technology, Germany.
    Greving, Imke (Contributor)
    Hamburg University of Technology, Germany.
    Zierold, Robert (Contributor)
    Hamburg University of Technology, Germany.
    Janßen, Rolf (Contributor)
    Hamburg University of Technology, Germany.
    Photonic materials for high-temperature applications: Synthesis and characterization by X-ray ptychographic tomography2018In: Applied Materials Today, ISSN 2352-9407, Vol. 13, p. 359-369Article in journal (Refereed)
    Abstract [en]

    Photonic materials for high-temperature applications need to withstand temperatures usually higher than 1000 °C, whilst keeping their function. When exposed to high temperatures, such nanostructured materials are prone to detrimental morphological changes, however the structure evolution pathway of photonic materials and its correlation with the loss of material's function is not yet fully understood. Here we use high-resolution ptychographic X-ray computed tomography (PXCT) and scanning electron microscopy (SEM) to investigate the structural changes in mullite inverse opal photonic crystals produced by a very-low-temperature (95 °C) atomic layer deposition (ALD) super-cycle process. The 3D structural changes caused by the high-temperature exposure were quantified and associated with the distinct structural features of the ceramic photonic crystals. Other than observed in photonic crystals produced via powder colloidal suspensions or sol-gel infiltration, at high temperatures of 1400 °C we detected a mass transport direction from the nano pores to the shells. We relate these different structure evolution pathways to the presence of hollow vertexes in our ALD-based inverse opal photonic crystals. Although the periodically ordered structure is distorted after sintering, the mullite inverse opal photonic crystal presents a photonic stopgap even after heat treatment at 1400 °C for 100 h.

  • 16.
    Karlsson, Stefan
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Kozlowski, Marcin
    Silesian University of Technology, Poland.
    Grund Bäck, Lina
    RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
    Andersson, Sara
    Acoustic Agree AB, Sweden.
    Haller, Kristian
    Acoustic Agree AB, Sweden.
    Persson, Kent
    Lund University, Sweden.
    Non‐destructive assessment of the glassstrength using nonlinear acoustics2022Conference paper (Other academic)
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  • 17.
    Kumar, Ashutosh
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Berg, Martin
    RISE Research Institutes of Sweden.
    Wang, Qin
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Salter, Michael
    RISE Research Institutes of Sweden.
    Ramvall, Peter
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Growth of p-type GaN - The role of oxygen in activation of Mg-doping2023In: Power Electronic Devices and Components, ISSN 2772-3704, Vol. 5, article id 100036Article in journal (Refereed)
    Abstract [en]

    The effects of N2 and O2:N2 (1:1) as ambient gases during activation annealing of Mg as p-type doping of GaN have been investigated. The purpose was to understand the mechanisms involved and especially the impact of O2 on the resulting hole concentration and hole mobility. The addition of O2 to the ambient gas during annealing is known to be very effective in reducing the H level of the Mg-doped GaN layer, but the maximum achievable hole concentration and mobility, as determined by Hall characterization, is still higher with pure N2. The difference is explained by an in-diffusion of O to the GaN layer acting as n-dopant and thus giving rise to a compensation effect. It is found that to a large degree only the Mg-H complexes at substitutional (MgGa), i.e., the electrically active acceptor sites that provide free holes, are activated by annealing with N2 only as ambient gas, while annealing with O2:N2 (1:1) also dissociates electrically inactive Mg-H complexes resulting in much less residual H. Thus, the residual H level in relation to the Mg level after activation annealing with N2 only may provide a representative measure of the resulting free hole concentration of the Mg-doped GaN layer.

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  • 18.
    Larsson, Emanuel
    Hamburg University of Technology, Germany.
    De Carlo, Francesco (Contributor)
    Lilleodden, Erica (Contributor)
    Institute of Advanced Ceramics, Hamburg University of Technology, Hamburg 21073, Germany.
    Storm, Malte (Contributor)
    Wilde, Fabian (Contributor)
    Kaixiong, Hu (Contributor)
    Müller, Martin (Contributor)
    Greving, Imke (Contributor)
    Nanoporous gold: a hierarchical and multiscale 3D test pattern for characterizing X-ray nano-tomography systems2019In: Journal of Synchrotron Radiation, ISSN 0909-0495, E-ISSN 1600-5775, Vol. 26, no 1Article in journal (Refereed)
    Abstract [en]

    Full-field transmission X-ray microscopy (TXM) is a well established technique, available at various synchrotron beamlines around the world as well as by laboratory benchtop devices. One of the major TXM challenges, due to its nanometre-scale resolution, is the overall instrument stability during the acquisition of the series of tomographic projections. The ability to correct for vertical and horizontal distortions of each projection image during acquisition is necessary in order to achieve the effective 3D spatial resolution. The effectiveness of such an image alignment is also heavily influenced by the absorption properties and strong contrast of specific features in the scanned sample. Here it is shown that nanoporous gold (NPG) can be used as an ideal 3D test pattern for evaluating and optimizing the performance of a TXM instrument for hard X-rays at a synchrotron beamline. Unique features of NPG, such as hierarchical structures at multiple length scales and high absorbing capabilities, makes it an ideal choice for characterization, which involves a combination of a rapid-alignment algorithm applied on the acquired projections followed by the extraction of a set of both 2D- and 3D-descriptive image parameters. This protocol can be used for comparing the efficiency of TXM instruments at different synchrotron beamlines in the world or benchtop devices, based on a reference library of scanned NPG samples, containing information about the estimated horizontal and vertical alignment values, 2D qualitative parameters and quantitative 3D parameters. The possibility to tailor the ligament sizes of NPG to match the achievable resolution in combination with the high electron density of gold makes NPG an ideal 3D test pattern for evaluating the status and performance of a given synchrotron-based or benchtop-based TXM setup.

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  • 19.
    Larsson, Erik G.
    et al.
    Linköping University, Sweden.
    Jorswieck, Eduard A.
    Dresden University of Technology, Germany.
    Lindblom, Johannes
    Linköping University, Sweden.
    Mochaourab, Rami
    Dresden University of Technology, Germany.
    Game Theory and the Flat-Fading Gaussian Interference Channel: Analyzing Resource Conflicts in Wireless Networks2009In: IEEE signal processing magazine (Print), Vol. 26, no 5, p. 18-27Article in journal (Refereed)
    Abstract [en]

    In this article, we described some basic concepts from noncooperative and cooperative game theory and illustrated them by three examples using the interference channel model, namely, the power allocation game for SISO IFC, the beamforming game for MISO IFC, and the transmit covariance game for MIMO IFC. In noncooperative game theory, we restricted ourselves to discuss the NE and PoA and their interpretations in the context of our application. Extensions to other noncooperative approaches include Stackelberg equilibria and the corresponding question "Who will go first?" We also correlated equilibria where a certain type of common randomness can be exploited to increase the utility region. We leave the large area of coalitional game theory open.

  • 20.
    Mochaourab, Rami
    et al.
    KTH Royal Institute of Technology, Sweden.
    Bengtsson, Mats
    KTH Royal Institute of Technology, Sweden.
    Stable Matching with Externalities for Beamforming and User Assignment in Multi-cell MISO Systems2016In: Proc WSA 2016, 2016, p. 549-554Conference paper (Refereed)
    Abstract [en]

    We consider the problem of distributed joint user association and beamforming in multi-cell multiple-input single-output systems. Assuming perfect local channel state information, each base station applies a distributed beamforming scheme called WSLNR-MAX [1] which depends on the user association in the network. We determine the user association by a proposed stable matching with externalities algorithm which also takes the beamforming vectors at the base stations into account. The merit in the stable matching model is the distributed implementation aspects. Each user asks to be matched with a base station according to his preferences, and each base station decides independently which users to accept. Simulation results reveal efficient distributed operation of the system compared to matching without externalities.

  • 21.
    Mochaourab, Rami
    et al.
    Fraunhofer, Germany.
    Cao, P.
    Technical University of Dresden, Germany.
    Jorswieck, E.
    Technical University of Dresden, Germany.
    Alternating Rate Profile Optimization in Single Stream MIMO Interference Channels2013In: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings, 2013, 2013, p. 4834-4838Conference paper (Refereed)
    Abstract [en]

    We consider a set of transmitter-receiver pairs operating concurrently in the same spectral band. The transmitters and receivers are equipped with multiple antennas and are restricted to apply single stream beamforming. This setting corresponds to the single stream multiple-input multiple-output (MIMO) interference channel. We assume perfect channel state information at the transmitters and the single-user decoding receivers. Efficient operating points in this setting correspond to points on the Pareto boundary of the achievable rate region. Characterizing all Pareto optimal points in the MIMO interference channel is still an unsolved problem. An approach to attain different Pareto optimal points in the MIMO interference channel is rate profile optimization. Given the nonconvexity of the problem, we propose an alternating approach based on successive optimization of the transmit and receive beamforming vectors. For fixed receive beamforming vectors, a solution for the rate profile optimization exists and is solved by a set of convex feasibility problems. For fixed transmit beamforming vectors, we show that the rate profile optimization can be solved by a set of feasibility problems each corresponding to an inverse field of values problem. The convergence of the alternating algorithm is guaranteed to a stationary point of the original problem.

  • 22.
    Mochaourab, Rami
    et al.
    Fraunhofer, Germany.
    Cao, P.
    TU Dresden, Germany.
    Jorswieck, E.
    TU Dresden, Germany.
    Alternating Rate Profile Optimization in Single Stream MIMO Interference Channels2014In: IEEE Signal Processing Letters, Vol. 21, no 2, p. 221-224Article in journal (Refereed)
    Abstract [en]

    The multiple-input multiple-output interference channel is considered with perfect channel information at the transmitters and single-user decoding receivers. With all transmissions restricted to single stream beamforming, we consider the problem of finding all Pareto optimal rate-tuples in the achievable rate region. The problem is cast as a rate profile optimization problem. Due to its nonconvexity, we resort to an alternating approach: For fixed receivers, optimal transmission is known. For fixed transmitters, we show that optimal receive beamforming is a solution to an inverse field of values problem. We prove the solution’s stationarity and compare it with existing approaches.

  • 23.
    Mochaourab, Rami
    et al.
    Dresden University of Technology, Germany.
    Jorswieck, E.
    Dresden University of Technology, Germany.
    Coalition Formation in MISO Interference Channels2011In: 4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing, CAMSAP 2011, 2011, p. 237-240Conference paper (Refereed)
    Abstract [en]

    We consider a multi-link multiple-input single-output interference channel. A link in this setting is noncooperative if its transmission does not take into account the interference it generates at other links. Noncooperative operation of the links is generally not efficient. To improve this situation, we study link cooperation via coalitional games. In coalitional games, a player has an incentive to cooperate with other players if this improves his payoff. We model the setting as a game in coalitional form without transferable utility. The players (links) in a coalition either perform zero forcing transmission or Wiener filter precoding to each other. Necessary and sufficient conditions, in terms of a lower signal-to-noise ratio (SNR) threshold, are provided under which all players have the incentive to cooperate and form a grand coalition. Inaddition, we provide sufficient conditions under which all players have no incentive to cooperate. In this case, the SNR has to be below a specified SNR threshold. Hence, there exists an SNR range in which the links would profit in forming subcoalitions. Therefore, we turn our attention to coalition formation games between the links. We utilize a coalition formation algorithm, called merge-and-split, to determine stable user grouping. Numerical results show that while in the low SNR regime noncooperation is efficient with single-player coalitions, in the high SNR regime all users benefit in forming a grand coalition. Coalition formation shows its significance in the mid SNR regime where subset user cooperation provides joint performance gains.

  • 24.
    Mochaourab, Rami
    et al.
    Dresden University of Technology, Germany.
    Jorswieck, E.
    Dresden University of Technology, Germany.
    Robust Pareto Optimal Beamforming in Two-User Multiple-Input Single-Output Interference Channel2011In: 19TH EUROPEAN SIGNAL PROCESSING CONFERENCE (EUSIPCO-2011), 2011Conference paper (Refereed)
    Abstract [en]

    We consider a two-user multiple-input single-output interference channel in which the receivers treat interference as additive noise. The transmitters are assumed to have imperfect channel state information to the receivers. The transmitters choose their beamforming vectors considering worst case power gains at the receivers. We provide a real-valued parametrization of the beamforming vectors that achieve the Pareto boundary of the rate region with channel uncertainties. Simulation results and high SNR analysis show that the gain in spectrum sharing under imperfect channel state information converges to the setting of time division multiple access. Moreover, we provide analytical results for the maximum sum rate in asymptotic cases of low and high signal to noise ratios.

  • 25.
    Mochaourab, Rami
    et al.
    Fraunhofer, Germany.
    Jorswieck, E.
    Dresden University of Technology, Germany.
    Walrasian Equilibrium Power Allocation in Protected and Shared Bands2012In: 2012 6TH INTERNATIONAL CONFERENCE ON NETWORK GAMES, CONTROL AND OPTIMIZATION (NETGCOOP), 2012Conference paper (Refereed)
    Abstract [en]

    We consider two transmitter-receiver pairs (links) operating on protected and shared frequency bands. Each link has a frequency band to use exclusively without any interference from the other link. A frequency band is shared between the two links. We study the power allocation problem of the two transmitters in the available bands using models from microeconomic theory. We model the setting as a competitive market in which the links are the consumers and transmission power are goods which can be bought by the consumers at specific prices. We assume there exists an authority, the arbitrator, which determines the prices of the goods and forwards them to the consumers. The Walrasian equilibrium in this model is Pareto optimal and corresponds to the prices that equate the demand to the supply of goods. We show that the Walrasian equilibrium always exists in our setting. We provide sufficient conditions for the uniqueness of the Walrasian equilibrium and also for the global stability of the price adjustment process to reach the equilibrium.

  • 26.
    Mochaourab, Rami
    et al.
    Dresden University of Technology, Germany.
    Jorswieck, E. A.
    Dresden University of Technology, Germany.
    Exchange economy in two-user multiple-input single-output interference channels2012In: IEEE Journal on Selected Topics in Signal Processing, Vol. 6, no 2, p. 151-164Article in journal (Refereed)
    Abstract [en]

    We study the conflict between two links in a multiple- input single-output interference channel. This setting is strictly competitive and can be related to perfectly competitive market models. In such models, general equilibrium theory is used to determine equilibrium measures that are Pareto optimal. First, we consider the links to be consumers that can trade goods within themselves. The goods in our setting correspond to beamforming vectors. We utilize the conflict representation of the consumers in the Edgeworth box, a graphical tool that depicts the allocation of the goods for the two consumers, to provide closed-form solution to all Pareto optimal outcomes. Afterwards, we model the situation between the links as a competitive market which additionally defines prices for the goods. The equilibrium in this economy is called Walrasian and corresponds to the prices that equate the demand to the supply of goods. We calculate the unique Walrasian equilibrium and propose a coordination process that is realized by an arbitrator which distributes the Walrasian prices to the consumers. The consumers then calculate in a decentralized manner their optimal demand corresponding to beamforming vectors that achieve the Walrasian equilibrium. This outcome is Pareto optimal and dominates the noncooperative outcome of the systems. Thus, based on the game theoretic model and solution concept, an algorithm for a distributed implementation of the beamforming problem in multiple-input single-output interference channels is provided.

  • 27.
    Mochaourab, Rami
    et al.
    Dresden University of Technology, Germany.
    Jorswieck, E.
    Dresden University of Technology, Germany.
    Ho, K. M. Z.
    Eurecom Institute, France.
    Gesbert, D.
    Eurecom Institute, France.
    Bargaining and Beamforming in Interference Channels2010In: Conference Record - Asilomar Conference on Signals, Systems and Computers 2010, 2010, p. 272-276Conference paper (Refereed)
    Abstract [en]

    Utilizing the real-valued parametrization of each transmitter’s efficient beamforming vectors, we propose a decentralized resource allocation scheme in the multiple-input single-output interference channel. The scheme is motivated by bargaining concepts in game theory. The aim of these concepts is to improve the joint payoff of the users from the Nash equilibrium outcome. In each bargaining-step, each user proposes a strategy. A user accepts any proposal if it increases his payoff. Otherwise, new proposals are made. When all proposals are accepted, a new bargaining-stage begins. We prove the scheme’s convergence and demonstrate its performance by simulations. In comparison to previous approaches, our bargaining outcome is arbitrarily close to the Pareto boundary of the achievable single-user rate region. We further discuss the control overhead and complexity of this scheme.

  • 28.
    Mochaourab, Rami
    et al.
    KTH Royal Institute of Technology, Sweden.
    Jorswieck, Eduard A.
    TU Dresden, Germany.
    Coalitional Games in MISO Interference Channels: Epsilon-Core and Coalition Structure Stable Set2014In: IEEE Transactions on Signal Processing, Vol. 62, no 24, p. 6507-6520Article in journal (Refereed)
    Abstract [en]

    The multiple-input single-output interference channel is considered. Each transmitter is assumed to know the channels between itself and all receivers perfectly and the receivers are assumed to treat interference as additive noise. In this setting, noncooperative transmission does not take into account the interference generated at other receivers which generally leads to inefficient performance of the links. To improve this situation, we study cooperation between the links using coalitional games. The players ( links) in a coalition either perform zero forcing transmission or Wiener filter precoding to each other. The epsilon-core is a solution concept for coalitional games that takes into account the overhead required in coalition deviation. We provide necessary and sufficient conditions for the strong and weak epsilon-core of our coalitional game not to be empty with zero forcing transmission. Since, the epsilon-core only considers the possibility of joint cooperation of all links, we study coalitional games in partition form in which several distinct coalitions can form. We propose a polynomial-time distributed coalition formation algorithm based on coalition merging and prove that its solution lies in the coalition structure stable set of our coalition formation game. Simulation results reveal the cooperation gains for different coalition formation complexities and deviation overhead models.

  • 29.
    Mochaourab, Rami
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Venkitaraman, Arun
    School of Electrical Engineering, Switzerland.
    Samsten, Isak
    Stockholm University, Sweden.
    Papapetrou, Panagiotis
    Stockholm University, Sweden.
    Rojas, Cristian
    KTH Royal Institute of Technology, Sweden.
    Post-hoc Explainability for Time Series Classification: Towards a Signal Processing Perspective2022In: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 39, no 4, p. 119-129Article in journal (Refereed)
    Abstract [en]

    Time series data correspond to observations of phenomena that are recorded over time [1]. Such data are encountered regularly in a wide range of applications, such as speech and music recognition, monitoring health and medical diagnosis, financial analysis, motion tracking, and shape identification, to name a few. With such a diversity of applications and the large variations in their characteristics, time series classification is a complex and challenging task. One of the fundamental steps in the design of time series classifiers is that of defining or constructing the discriminant features that help differentiate between classes. This is typically achieved by designing novel representation techniques [2] that transform the raw time series data to a new data domain, where subsequently a classifier is trained on the transformed data, such as one-nearest neighbors [3] or random forests [4]. In recent time series classification approaches, deep neural network models have been employed that are able to jointly learn a representation of time series and perform classification [5]. In many of these sophisticated approaches, the discriminant features tend to be complicated to analyze and interpret, given the high degree of nonlinearity.

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    fulltext
  • 30.
    Navarro, Jaime Rodrigo
    et al.
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Kakkar, Aditya
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Ozolins, Oskars
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Olmedo, Miguel Iglesias
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Carrier Phase Recovery Algorithms for Coherent Optical Circular mQAM Systems2016In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 34, no 11, p. 2717-2723Article in journal (Refereed)
    Abstract [en]

    The phase noise tolerance of circular multilevel quadrature amplitude modulation (C-mQAM) constellations employing different carrier phase recovery (CPR) algorithms is studied. A differential decoding scheme and a bit mapping for this type of constellations are proposed. A novel CPR scheme for C-mQAM constellations is also presented. The particular distribution of the constellation points in a C-mQAM signal is exploited to reduce the required Nth power for the removal of the modulation component by a factor of two. Hence, the computational complexity of the proposed algorithm is drastically reduced. The combined linewidth symbol duration product (??Ts) tolerance of different CPR algorithms for C-mQAM constellations is studied and compared with the proposed CPR scheme. The results are analyzed at 3.8e-3 and 1e-2 bit error rate forward error correction limits. The proposed CPR scheme achieves similar ??Ts tolerance compared to single stage BPS algorithm while its computational complexity is reduced by group factors of 27.2 | 32.3, and 30.5 | 32.6 (in the form of multipliers | adders) for C-16QAM and C-64QAM, respectively.

  • 31.
    Nazari, Mohammad A.
    et al.
    Chalmers University of Technology, Sweden.
    Seco-Granados, Gonzalo
    Universitat Autonoma de Barcelona, Spain.
    Johannisson, Pontus
    RISE Research Institutes of Sweden. Chalmers University of Technology, Sweden.
    Wymeersch, Henk
    Chalmers University of Technology, Sweden.
    3D Orientation Estimation with Multiple 5G mmWave Base Stations2021In: ICC 2021 - IEEE International Conference on Communications, 2021Conference paper (Refereed)
    Abstract [en]

    We consider the problem of estimating the 3D orientation of a user, using the downlink mmWave signals received from multiple base stations. We show that the received signals from several base stations, having known positions, can be used to estimate the unknown orientation of the user. We formulate the estimation problem as a maximum likelihood estimation in the manifold of rotation matrices. In order to provide an initial estimate to solve our non-linear non-convex optimization problem, we resort to a least squares estimation that exploits the underlying geometry. Our numerical results show that the problem of orientation estimation can be solved when the signals from at least two base stations are received. We also provide the orientation lower error bound, showing a narrow gap between the performance of the proposed estimators and the bound.

  • 32.
    Ozolins, O.
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo.
    An, Y.
    Lali-Dastjerdi, Z.
    Ding, Y.
    Bobrovs, V.
    Ivanovs, G.
    Peucheret, C.
    Cascadability of silicon microring resonators for 40-Gbit/s OOK and DPSK optical signals2012In: 2012 Asia Communications and Photonics Conference (ACP), 2012, p. 1-3Conference paper (Refereed)
    Abstract [en]

    The cascadability of a single silicon micro-ring resonator for CSRZ-OOK and CSRZ-DPSK signals is experimentally demonstrated at 40 Gbit/s for the first time. Error-free performance is obtained for both modulation formats after 5 cascaded resonators.

  • 33.
    Ozolins, Oskars
    et al.
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Pang, Xiaodan
    RISE - Research Institutes of Sweden (2017-2019), ICT.
    Olmedo, Miguel Iglesias
    KTH Royal Institute of Technology, Sweden.
    Udalcovs, Aleksejs
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo. KTH Royal Institute of Technology, Sweden.
    Kakkar, Aditya
    KTH Royal Institute of Technology, Sweden.
    Navarro, Jaime Rodrigo
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    Schatz, Richard
    KTH Royal Institute of Technology, Sweden.
    Westergren, Urban
    KTH Royal Institute of Technology, Sweden.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Jacobsen, Gunnar
    RISE - Research Institutes of Sweden (2017-2019), ICT, Acreo.
    “High-speed optical and wireless transmission - challenges and achievements”2016In: 2016 Advances in Wireless and Optical Communications (RTUWO), 2016Conference paper (Refereed)
    Abstract [en]

    The cloud services together with the huge size datasets are driving demand for bandwidth in datacenters. The 400 Gbps client-side links are demanding a solution. The intensity modulation and direct-detection systems together with integrated semiconductor lasers and modulators appear as promising solution in four optical lanes at 100 Gbps net rate in order to reduce complexity, size, power consumption and cost.

  • 34.
    Ramadan, Mohammed
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Data Science.
    Raza, Shahid
    RISE Research Institutes of Sweden, Digital Systems, Data Science.
    Broadband Jamming Suppression at Subarray Level for Frequency Diverse Array Antenna2022In: Proceedings - 16th International Conference on Signal-Image Technology and Internet-Based Systems, Institute of Electrical and Electronics Engineers Inc. , 2022, p. 231-237Conference paper (Refereed)
    Abstract [en]

    Frequency diverse array (FDA) is a modern and flexible antenna array conception different from the phased array (PA). The FDA utilized a small frequency increment across the antenna elements to achieve a range-dependent beam pattern. Adopting subarray signal processing is one of the critical technologies in new PAs that plays a significant role in clutter and noise jammer suppression. However, it experiences serious performance regression in the case of broadband jamming. This paper proposes a concrete scheme based on FDA subarray signal processing coupled with real-time delay processing to counteract broadband jamming. Therefore, the FDA combines real-time delay processing; the desired target can be distinguished from the clutter and jamming signals at the subarray level. Accordingly, adaptive weights based on space-time finite impulse response (FIR) filter (linearly constrained minimum variance (LCMV) method are applied at all delay outputs of each subarray to achieve optimum performance. The look angle uniquely determines the space steering vector with a different spatial steering vector for each transmitted frequency. The simulation results show that our proposed method is efficient, effective, and practically applicable. 

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