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  • 1.
    Al-Alosi, Muhammed
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Framtidsmöjligheter med 5G mobilnät2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report introduces various mobile network technologies, 1G to 5G. Focus is on the future 5G mobile networks, how it works and what opportunities will come with it. The report also covers the base stations that will be used in the future mobile network, with a brief description of the terminal in 5G network and the services that will be available with it. The protocol stack in 5G network is also covered. Moreover the report presents the Wi-Fi 802.11u standard that will be a part of the future mobile network. We can also read about how the 5G network will solve certain problems that are related to today's networks technologies. Finally, the report describes different access technologies that are used in the telecommunications systems.

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    Framtidsmöjligheter med 5G mobilnät
  • 2.
    Anani, Adi
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    M-learning in review: Technology, standard and evaluation2008In: Journal of Communication and Computer, ISSN 1548-7709, Vol. 5, no 11, p. 1-6Article in journal (Refereed)
    Abstract [en]

    Nowadays E-learning as a form of learning depending on networks and computer devices has been expanding by leaps and bounds. As a special kind of E-learning, M-learning (mobile learning) aims at the use of mobile devices anywhere at anytime by anybody. In this paper, the technologies to develop a M-learning system is deeply analyzed according to the layer model at first. Secondly, from the view of application, the standardization in M-learning is researched in order to accelerate the development and popularization of M-learning. Finally, quality estimation of M-learning system is discussed from the view of QoE (quality of experiences). The experience form end-user is the sole effective norm to judge the result of M-learning technology. It is no doubt that technologies, standardization and evaluation will play very important parts in the course of M-learning development.

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    FULLTEXT01
  • 3.
    Anani, Adi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Zhang, Deng-yin
    Institute of Signal Processing and Transmission, Nanjing University of Posts and Telecommunications, China.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    QoS-guaranteed packet scheduling in wireless networks2009In: The Journal of China Universities of Posts and Telecommunications, ISSN 1005-8885, Vol. 16, no 2, p. 63-67Article in journal (Refereed)
    Abstract [en]

    To guarantee the quality of service (QoS) of a wireless network, a new packet scheduling algorithm using cross-layer design technique is proposed in this article. First, the demand of packet scheduling for multimedia transmission in wireless networks and the deficiency of the existing packet scheduling algorithms are analyzed. Then the model of the QoS-guaranteed packet scheduling (QPS) algorithm of high speed downlink packet access (HSDPA) and the cost function of packet transmission are designed. The calculation method of packet delay time for wireless channels is expounded in detail, and complete steps to realize the QPS algorithm are also given. The simulation results show that the QPS algorithm that provides the scheduling sequence of packets with calculated values can effectively improve the performance of delay and throughput.

  • 4.
    Asan, Noor Badariah
    et al.
    Ångström Laboratory, Microwaves in Medical Engineering Group, Department of Electrical Engineering, Uppsala University, Uppsala, Sweden; Centre for Telecommunication Research and Innovation (CeTRI), Fakulti Kejuruteraan Elektronik dan Kejuruteraan Komputer, Universiti Teknikal Malaysia Melaka, Durian Tunggal, Malaysia.
    Hassan, Emadeldeen
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Department of Electronics and Electrical Communications, Menoufia University, Menouf, Egypt; Hannover Centre for Optical Technologies, Cluster of Excellence PhoenixD, Leibniz University Hannover, Hanover, Germany; Faculty of Mechanical Engineering, Institute of Transport and Automation Technology, Leibniz University Hannover, Garbsen, Germany.
    Perez, Mauricio D.
    Ångström Laboratory, Microwaves in Medical Engineering Group, Department of Electrical Engineering, Uppsala University, Uppsala, Sweden.
    Joseph, Laya
    Ångström Laboratory, Microwaves in Medical Engineering Group, Department of Electrical Engineering, Uppsala University, Uppsala, Sweden.
    Berggren, Martin
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Voigt, Thiemo
    Department of Information Technology, Uppsala University, Uppsala, Sweden.
    Augustine, Robin
    Ångström Laboratory, Microwaves in Medical Engineering Group, Department of Electrical Engineering, Uppsala University, Uppsala, Sweden.
    Fat-IntraBody Communication at 5.8 GHz: Verification of Dynamic Body Movement Effects using Computer Simulation and Experiments2021In: IEEE Access, E-ISSN 2169-3536, Vol. 9, p. 48429-48445Article in journal (Refereed)
    Abstract [en]

    This paper presents numerical modeling and experimental validation of the signal path loss at the 5.8 GHz Industrial, Scientific, and Medical (ISM) band, performed in the context of fat-intrabody communication (fat-IBC), a novel intrabody communication platform using the body-omnipresent fat tissue as the key wave-guiding medium. Such work extends our previous works at 2.0 and 2.4 GHz in the characterization of its performance in other useful frequency range. In addition, this paper also includes studies of both static and dynamic human body movements. In order to provide with a more comprehensive characterization of the communication performance at this frequency, this work focuses on investigating the path loss at different configurations of fat tissue thickness, antenna polarizations, and locations in the fat channel. We bring more realism to the experimental validation by using excised tissues from porcine cadaver as both their fat and muscle tissues have electromagnetic characteristics similar to those of human with respect to current state-of-art artificial phantom models. Moreover, for favorable signal excitation and reception in the fat-IBC model, we used topology optimized waveguide probes. These probes provide an almost flat response in the frequency range from 3.2 to 7.1 GHz which is higher than previous probes and improve the evaluation of the performance of the fat-IBC model. We also discuss various aspects of real-world scenarios by examining different models, particularly homogeneous multilayered skin, fat, and muscle tissue. To study the effect of dynamic body movements, we examine the impact of misalignment, both in space and in wave polarization, between implanted nodes. We show in particular that the use of fat-IBC techniques can be extended up in frequency to a broadband channel at 5.8 GHz.

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    fulltext
  • 5. Bagheri, Shahriar
    et al.
    Jafarov, Tural
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Sepehri, Nariman
    Beneficially Combining LQR and PID to Control Longitudinal Dynamics of a SmartFly UAV2016In: 7TH IEEE ANNUAL INFORMATION TECHNOLOGY, ELECTRONICS & MOBILE COMMUNICATION CONFERENCE IEEE IEMCON-2016 / [ed] Chakrabarti S, Saha HN, 2016Conference paper (Refereed)
    Abstract [en]

    The problem of control system design for longitudinal axis of a small-size flying wing is studied. The new controller proposed is comprised of two controllers working together to provide robust stability and step reference tracking for the nonlinear dynamics of SmartFly UAV. More precisely, Linear Quadratic Regulator (LQR) is used together with Proportional, Integral, Derivative (PID) controller. The inspiration comes from the fact that each of the mentioned controllers have advantages and disadvantages that cannot be neglected. LQR, as an optimal in terms of energy-like regulator, provides robust stability with a minimized energy-like performance index. It is also very computationally efficient. But, when it comes to the transient of particular output, LQR is not the best solution. On the other hand, PID has the advantage of a possibility to tune the gains for optimized transient behavior, especially for well-behaving plants. Furthermore, PID controller is particularly useful for tracking problems. However, PID is often not robust (in terms of parameter uncertainties) and it is also difficult to tune PID parameters for unstable systems. By differentiating between system stability and performance in the controller design process, it is possible to benefit from both controllers, using them along side together in one system. Functionality of this method was verified through computer simulation in MATLAB/SIMULINK for a nonlinear model of SmartFly UAV. Closed-loop system performance was evaluated in terms of robustness and step reference tracking.

  • 6.
    Brännback, Andreas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    FTTX-Analysverktyg anpassat för Telias nät2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A tool for analyzing the status of Fiber to the X (FTTX) customers in Telia’s network has been programmed in the Python programming language. The system consists of a module divided structure where analysis functions of similar types are bundled into module files. The system is designed to be easily further developed by adding more analysis modules in future projects. To perform an analysis on a specific customer, the system retrieves technical data parameters from the switch which the customer is connected to, and compares these parameters against predetermined values to find deviations. Simple Network Management Protocol (SNMP) and Telnet are the primary protocols used to retrieve data. Hypertext Transfer Protocol (HTTP) is used to transfer data as system input and output. The result of an analysis is sent as Extensible Markup Language (XML) back to the server that originally requested the start of an analysis. The XML reply contains technical data parameters describing the customer’s connection status and an analytical response based on these technical parameters. The amount of data presented in the XML response varies slightly depending on the type of switch the customer is connected to. Switches of older hardware types generally presents less customer port data compared to more modern switches. Less customer port data leads to poor detail in the analytical response, and therefore, this analysis tool is better suited to the modern switches found in Telia's network.

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    fulltext
  • 7.
    Carls, Johan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    NGN – Nästa Generations Nätverk (Nätverks- och Riskanalys) för Piteå Kommun2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    My mission has been to technical documentation and identify Piteå Municipality's existing network infrastructure. Everything has been summarized in several different areas: Network Services, Network-related services, Technology, Management/Control and Security. A risk analysis has been developed where I have identified a total of 28 risks and deficiencies in the municipality's existing network infrastructure. 4 risks and deficiencies under Design, 9 risks and deficiencies under Security, 5 risks and deficiencies under Network related services, 2 risks and deficiencies under Network Services, 2 risks and deficiencies under Management/Control and 5 risks and deficiencies under Technology. All risks and deficiencies have been categorized in order of low, medium and high risks and deficiencies of varying action time (0-24 + months). This final report has been the basis for then developing a new future-proof network infrastructure using a Requirements and Vision for the Municipality of Piteå.

  • 8.
    Dong, H.
    et al.
    Network Technology Research Centre, Nanyang Technological University, Singapore.
    Shum, P.
    Network Technology Research Centre, Nanyang Technological University, Singapore.
    Yan, M.
    Network Technology Research Centre, Nanyang Technological University, Singapore.
    Zhou, J. Q.
    Network Technology Research Centre, Nanyang Technological University, Singapore.
    Ning, G. X.
    Network Technology Research Centre, Nanyang Technological University, Singapore.
    Gong, Y. D.
    Institute for InfoComm Research, Singapore.
    Wu, C. Q.
    School of Science, Beijing Jiaotong University, China.
    Generalized Mueller matrix method for polarization mode dispersion measurement in a system with polarization-dependent loss or gain2006In: Optics Express, E-ISSN 1094-4087, Vol. 14, no 12, p. 5067-5072Article in journal (Refereed)
    Abstract [en]

    A generalized Mueller matrix method (GMMM) is proposed to measure the polarization mode dispersion (PMD) in an optical fiber system with polarization-dependent loss or gain (PDL/G). This algorithm is based on the polar decomposition of a 4×4 matrix which corresponds to a Lorentz transformation. Compared to the generalized Poincaré sphere method, the GMMM can measure PMD accurately with a relatively larger frequency step, and the obtained PMD data has very low noise level.

  • 9.
    Dong, H.
    et al.
    Network Technology Research Centre, Nanyang Technological University, Singapore, Singapore.
    Shum, P.
    Network Technology Research Centre, Nanyang Technological University, Singapore, Singapore.
    Yan, M.
    Network Technology Research Centre, Nanyang Technological University, Singapore, Singapore.
    Zhou, J.Q.
    Network Technology Research Centre, Nanyang Technological University, Singapore, Singapore.
    Ning, G.X.
    Network Technology Research Centre, Nanyang Technological University, Singapore, Singapore.
    Gong, Y.D.
    Institute for Inforcomm Research, Singapore, Singapore.
    Wu, C.Q.
    School of Science, Beijing Jiaotong University, Beijing, China.
    Measurement of Mueller matrix for an optical fiber system with birefringence and polarization-dependent loss or gain2007In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 274, no 1, p. 116-123Article in journal (Refereed)
    Abstract [en]

    In an optical fiber system with both birefringence and polarization-dependent loss or gain (PDL/G), a set of input polarization states and their corresponding outputs are deduced to fulfill some general relationships in Stokes space, by considering the fact that the Mueller matrix of such an optical fiber system meets Lorentz transformation. Then, it can be proven that the minimum number of input polarization states is three for an explicit determination of such a Mueller matrix and no independent input parameter is redundant. Based on the theoretical findings, a general and simple approach is proposed to measure the Mueller matrix. The requirements regarding the choices of three inputs are presented for achieving optimum measurement stability and accuracy. Experimental results on an optical fiber system, formed by two 10-km long single-mode fibers with an optical isolator in between, show excellent agreement with the theory.

  • 10. Dong, Hui
    et al.
    Shum, Ping
    Gong, Yandong
    Yan, Min
    Nanyang Technological University, Network Technology Research Centre, Singapore.
    Zhou, Junqiang
    Wu, Chongqing
    Measurement of polarization mode dispersion vectors in optical fibers using a virtual Mueller matrix method2007In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 46, no 3, article id 035007Article in journal (Refereed)
    Abstract [en]

    A virtual Mueller matrix method is proposed to measure the first- and second-order polarization mode dispersion (PMD) vectors in optical fibers. This method not only can use a large frequency step to attain low-noise PMD vector data, but also does not require knowledge of the input polarization states. Our measurement method has a simpler setup and is more accurate than the traditional Mueller matrix method.

  • 11.
    Eriksson Selin, William
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Study of antenna arrays for direction finding2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The new Bluetooth standard (Bluetooth 5.1) contains direction finding specifications. Specifications for received signal strength indicator(RSSI) using measures of signal strength in order to give a sense of how far away an object is has been present in earlier versions. It will now be accompanied with the possibility of angle of arrival estimation(AoA). AoA estimation in Bluetooth utilizes antenna arrays. Antenna arrays are formations of many individual antenna elements working together. The difference between the measured data at each antenna is dependent on the orientation and position of the antenna elements as well as on phase of an incoming electromagnetic signal. By looking at the phase shifts between the antenna elements in an antenna array it is possible to find an estimation of the direction of where the incoming signal is coming from. 

    The goal of this thesis is to investigate if the NicheTM antenna(concept developed by Proant AB) is applicable for AoA estimation. In the project we have simulated the different characteristics of the Niche antenna and done extensive simulations of different types of configurations of an Niche antenna array. The commercial electromagnetics simulator CST MW studio suite has been used for simulations. A formation that works well with regards to stability and mutual coupling has been found. The simulated results have also been confirmed by measurements on a mechanically constructed antenna array. Measurements have been carried out in an anechoic chamber. We have done full radiation pattern measurements of the antenna array. The antenna array that we have created can estimate the angle of arrival of an incoming signal with an accuracy of 2.7o with a certainty of one standard deviation. For increased accuracy in the AoA estimation a MATLAB code utilizing the MUSIC(MUltiple SIgnal Classification) algorithm with our variant of the steering vector has been written.

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    fulltext
  • 12.
    Forsberg, Evelina
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Enterprise Voice Simulation (EVS) för mobila enheter i BYOD miljö.2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report introduces the Umeå University background to the introduction of Lync Server 2013 stable established in 2014. The wireless network at Umeå University used by students and employees with mobile devices such as smartphones and laptops. The throughput into the wireless network is affected by different types of traffics from various devices in whole network infrastructure. This report covered closer glance at "Voice UDP" and "Lync Enterprise Voice" with a focus on congestion control for transfers of RTP traffic between mobile clients and 802.11 to identify the quality of a Lync call, "VoIP over WLAN”. The method is based on references with MOS scale of 1 to 5 in order to compare which mobile device should qualify for best achieved Quality of Experience. The results of the eight selected mobile devices showed that the Samsung Galaxy s2 topped the overall benchmark for minimum dropped and most passed packets. The iPhone 5 resulted in the worst mobile device for RTP traffic with the most amount of lost packets and the lowest amount of passing packets.Benchmark:Benchmark measured by the total summation of percent and pmeasurement references, Voice MOS, packet loss, maximum Consecutive

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    Enterprise_Voice_Simulation
  • 13. Gacanin, Haris
    et al.
    Sjödin, Tomas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Adachi, Fumiyuki
    On Channel Estimation for Analog Network Coding in a Frequency-Selective Fading Channel2011In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, article id 980430Article in journal (Refereed)
    Abstract [en]

    Recently, broadband analog network coding (ANC) was introduced for high-speed transmission over the wireless (frequency-selective fading) channel. However, ANC requires the knowledge of channel state information (CSI) for self-information removal and coherent signal detection. In ANC, the users' pilot signals interfere during the first slot, which renders the relay unable to estimate CSIs of different users, and, consequently, four time-slot pilot-assisted channel estimation (CE) is required to avoid interference. Naturally, this will reduce the capacity of ANC scheme. In this paper, we theoretically analyze the bit error rate (BER) performance of bi-directional broadband ANC communication based on orthogonal frequency division multiplexing (OFDM) radio access. We also theoretically analyze the performance of the channel estimator's mean square error (MSE). The analysis is based on the assumption of perfect timing and frequency synchronization. The achievable BER performance and the estimator's MSE for broadband ANC is evaluated by numerical and computer simulation. We discuss how, and by how much, the imperfect knowledge of CSI affects the BER performance of broadband ANC. It is shown that the CE scheme achieves a slightly higher BER in comparison with ideal CE case for a low and moderate mobile terminal speed in a frequency-selective fading channel.

  • 14.
    Georgakis, Apostolos
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Part-of-speech tagging for client-side link prefetching2007In: Proceedings of the IASTED European Conference on Internet and Multimedia Systems and Applications / [ed] Marco Roccetti, Anaheim: ACTA Press, 2007, p. 272-277Conference paper (Refereed)
    Abstract [en]

    In this paper a client-side algorithm that learns and predicts user requests is presented. The proposed approach is based on a user behavior profile. The profile is based on textual information extracted from visited web pages. The novelty of the paper is in the use of a part-of-speech tagger to filter the useful user-keywords. The keywords comprising the profile are employed by a transparent and speculative link weighting mechanism. The generated weights are used in estimating future web traversing. Afterwards some linked web pages are prefetched and stored locally in the browser's cache. A comparison between the proposed algorithms and four other client-side algorithms yield improved cache-hit rates given a moderate bandwidth overhead.

  • 15. Gustafson, Carl
    et al.
    Bolin, David
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Tufvesson, Fredrik
    Modeling the Cluster Decay in mm-Wave Channels2014In: 2014 8TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP), 2014, p. 803-807Conference paper (Refereed)
    Abstract [en]

    The cluster power is an important parameter for cluster-based wireless channel models. This paper addresses modeling and estimation of the cluster power for wireless channels. A novel way of estimating the cluster decay and cluster fading, where the effects of the noise floor is taken into account, is presented. Due to the noise floor present in the measurement, only a limited number of clusters are available when estimating the cluster decay. It is shown that the estimated cluster decay and cluster fading can be improved if the effects of the noise floor and cluster fading are modeled and taken into account in the estimation step. If the noise floor is not taken into account in the estimation of the cluster decay, the resulting model can overestimate the RMS delay spread. Further, the paper includes estimates of the cluster decay and fading based on measured clusters for an indoor wireless mm-Wave channel in a conference room environment.

  • 16.
    Johansson, Daniel
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Automatic microphone mixing for a daisy chain connected multi-microphone speakerphone setup2016Independent thesis Advanced level (degree of Master (Two Years)), 300 HE creditsStudent thesis
    Abstract [en]

    Speakerphones are an essential part of making remote meetings with groups of people possible. An important ingredient to achieve a satisfying teleconferencing experience is good audio pickup quality of the speakerphone.

    Limes Audio supports a multi-microphone speakerphone reference design with daisy chain connectivity. This implies a structure where several microphone signals need to be mixed down to one output channel for transmission.This thesis is focused on the challenges of automatically mixing down these multiple microphone signals to one output with minimum amount of reverberation and extraneous noise.

    In this thesis, I thoroughly analyze the automatic microphone mixing problem and the existing implementation from Limes Audio. I review a selection of alternative mixing methods, propose a new method, and compare the performance of them using objective speech quality and intelligibility measures.

    One significant part of the process has been to define a suitable test protocol for assessing the performance of different mixer implementations, and the project has resulted in a test procedure which could be used for evaluating the automaticmixing performance of competing products in the future.

    The results from my evaluation show that the best quality is achieved by using a single microphone per speaker. The current method tries to do this and achieves relatively good performance compared to the alternatives. The proposed method with somewhat different characteristics performs worse in some scenarios, but better in others.

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    fulltext
  • 17.
    Johansson Sävenberg, David
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Fiberoptisk nätplanering2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report describes how you can build a fiberoptical broadband network in and for the community of Ersliden outside the city of Umeå. The system design is planned after a detailed description of the network requirements.

    The report is in two parts. The first part brings up the planning of the fiberoptic network. The second describes the wireless access point.

    This study brings up what kind of fiberoptics the network should have, and how nodes and channelization are planned. It also provides examples of hardware that matches the network’s needs.

    Download full text (pdf)
    fulltext
  • 18.
    Johansson Sävenberg, David
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Projektering av ett LAN; Summit Kista2016Independent thesis Basic level (degree of Bachelor), 180 HE creditsStudent thesis
    Abstract [en]

    The purpose of this project is to build a local area network for Summit, a company in Kista outside the city of Stockholm, which is also for the use of their customers. The aim was that the local area network should be usable by at least 400 customers simultaneously and that the LAN should be both reliable and secure. I began the project with a pilot study where I researched different methods I could use to help me build the network.

    Over the course of the project I chose hardware that was suitable for the network’s needs; I configured it; and I documented the whole network. When I was finished with the configuration and documentation I installed the whole network in the building.

    The result of this project is a huge success as a fully working local area network.  I also managed to implement all the network’s needs described in the specification: everything from the network’s speed to how the network is segmented for the most secure way of handling sensitive data.

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    Examensrapport Nätprojekt
  • 19.
    Karlsson, Johannes
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Anani, Adi
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Enabling real-time video services over ad-hoc networks opens the gates for e-learning in areas lacking infrastructure2009In: International Journal of Interactive Mobile Technologies (iJIM), E-ISSN 1865-7923, Vol. 3, no 4, p. 17-23Article in journal (Refereed)
    Abstract [en]

    In this paper we suggest a promising solution to come over the problems of delivering e-learning to areas with lack or deficiencies in infrastructure for Internet and mobile communication. We present a simple, reasonably priced and efficient communication platform for providing e-learning. This platform is based on wireless ad-hoc networks. We also present a preemptive routing protocol suitable for real-time video communication over wireless ad-hoc networks. Our results show that this routing protocol can significantly improve the quality of the received video. This makes our suggested system not only good to overcome the infrastructure barrier but even capable of delivering a high quality e-learning material.

  • 20.
    Kouma, Jean-Paul
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Large-scale face images retrieval: a distribution coding approach2009In: ICUMT 2009 - International Conference on Ultra Modern Telecommunications, 2009Conference paper (Other academic)
    Abstract [en]

    Great progress in face recognition technology has been made recently. Such advances will provide us the possibility to build a new generation of search engine: Face Google, searching from person photos. It is very challenging to find a person from a very large or extremely large database which might hold face images of millions or hundred millions of people. The indexing technology used in most commercial search engines like Google, is very efficient for text-based search, unfortunately, it is no longer useful for image search. A solution is to use partial information (signature) about all the face images for search. The retrieval speed is approximately proportional to the size of a signature image. In this paper we will study a totally new way to compress the signature images based on the observation that the face signature images and the query images are highly correlated if they are from the same individual. The face signature image can be greatly compressed (one or two orders of magnitude improvement) by use of knowledge of the query images. We can expect the new compression algorithm to speed up face search 10 to 100 times. The challenge is that query images are not available when we compress their signature image. Our approach is to transfer the face search problem into the so-called ”Wyner-Ziv Coding” problem, which could give the same compression efficiency even if the query images are not available until we decompress signature images. A practical compression scheme based on LDPC codes is developed to compress face signature images.

  • 21.
    Kynman, Ossian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Analysis and Measurement of Key Performance Indicators for MIMO Antennas2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Multiple-in multiple-out (MIMO) is a wireless communication technique where antenna arrays, at the receiver and transmitter, utilize signal multipath propagation to increase data throughput capacity. The unique benefits MIMO provides have over the last 20 years led to the steady increase in usage in both Wi-Fi and mobile networks. Predicting the performance of an antenna array designed for MIMO is more difficult than predicting the performance of a single antenna. This is due to the increased performance deriving from the processed combination of information from each antenna element. To determine the increased benefits that additional antenna elements can provide to a wireless system, the statistical correlation between the signals received from all antenna element needs to be evaluated. This correlation is expressed with the correlation coefficient $\rho$. The correlation coefficient may be estimated from the far field radiation pattern measured in an anechoic chamber, or measured from the statistically isotropic and homogeneous radiation environment provided by a reverberation chamber. However, Blanch, et al. 2003, proposed a much simpler method to estimate the correlation coefficient using a Vector Network Analyzer (VNA) to measure scattering parameters (S-parameters) while assuming perfect antenna efficiency. In 2005 Hallbjörner proposed a modified version of the estimation including the effect of antenna efficiency. This project aimed to measure and compare the results from the two types of chamber tests along with the two S-parameter based approximation methods mentioned. To accomplish this, three different antenna arrays, with four elements each with varying efficiency and mutual coupling, were designed and manufactured. The antenna arrays were then measured in an anechoic chamber, in a reverberation chamber, and had their S-parameters determined with a VNA. From the measurements it was found that the results from both types of chamber tests agree well, indicating that both tests are viable methods of signal correlation estimation. The S-parameter method proposed by Blanch was found to be inaccurate for the antennas tested, likely due to low radiation efficiencies. However, the approximation method proposed by Hallbjörner produced better results, but requires the efficiencies of the antennas which is generally not simple to determine. In conclusion it is found that S-parameter measurements, which are commonly used by the wireless industry, do not provide valid estimates of the MIMO performance of antenna arrays unless they are complemented with measurements of antenna efficiency.

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  • 22.
    Li, Fei
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Key Lab of Broadband Wireless Communication and Sensor Network Technology, Nanjing University of Posts and Telecommunication, Ministry of Education, Nanjing, China.
    Zhou, Lizhi
    Key Lab of Broadband Wireless Communication and Sensor Network Technology, Nanjing University of Posts and Telecommunication, Ministry of Education, Nanjing, China.
    Liu, Li
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    A quantum search based signal detection for MIMO-OFDM systems2011In: 18th International Conference on Telecommunications, ICT 2011, IEEE, 2011, p. 276-281, article id 5898934Conference paper (Refereed)
    Abstract [en]

    Multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) is considered as candidates for future broadband wireless services. In this paper a novel signal detection scheme based on Grover's quantum search algorithm is proposed for MIMO-OFDM systems. Grover's quantum search algorithm is based on the concept and principles of quantum computing, such as quantum bit, quantum register and quantum parallelism. An analysis is given to the theoretical basis of Grover's algorithm and the performance of Grover's algorithm is evaluated. A novel signal detector based on Grover's algorithm (GD) for MIMO-OFDM system is proposed. The simulation results show that the proposed detector has more powerful properties in bit error rate than MMSE detector and VBLAST-MMSE detector. The performance of the proposed GD detector is close to optimal when the failure probability is 0.001. When the failure probability is 0.00001, the performance of GD detector declines. In this case, our proposed improved Grover's algorithm based detector is still close to the optimal ML detector. The complexity of GD and IGD is O(√N). It's much better than classical ML detector which complexity is O(N). 

  • 23.
    Li, Fei
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Key Lab of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education, Nanjing University of Posts and Telecommunications, Nanjing, China.
    Zhu, Dongpo
    Key Lab of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education, Nanjing University of Posts and Telecommunications, Nanjing, China.
    Tian, Feng
    Key Lab of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education, Nanjing University of Posts and Telecommunications, Nanjing, China.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Cognitive radio spectrum sharing using improved Quantum Genetic Algorithm2011In: 2011 International Conference on Wireless Communications and Signal Processing, WCSP 2011, IEEE, 2011, article id 6096690Conference paper (Refereed)
    Abstract [en]

    A key challenge in cognitive radios (CR) network is how to adaptively and efficiently allocate transmission powers and spectrum among CR users according to the surrounding environment. In this paper, we propose a novel spectrum sharing based on our improved Quantum Genetic Algorithm (QGA) in a non-cooperative game for CR network. We improved the original QGA by quantum crossover operator, in order to overcome the shortcoming of the original QGA easily falling into a local extremum when used to optimize the continuous functions with many extrema. We used our improved QGA as a competitive strategy and conducted several simulations in two-user system and multi-user system. From simulation results, it is evident that the proposed improved QGA based spectrum sharing scheme has better convergence rate and higher sum capacity than GA based scheme even in multi-user CR system, namely up to 2bit/s/Hz increase in capacity. The simulation results also show that the population size of QGA affect sum capacity of cognitive radio system. The results demonstrated the effectiveness and the applicability of QGA in spectrum sharing in multi-user cognitive radio system. 

  • 24.
    Li, Fei
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Institute of Signal Processing and Transmission, Key Lab of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education, Nanjing University of Posts and Telecommunications, Nanjing, China.
    Zhu, Dongpo
    Institute of Signal Processing and Transmission, Key Lab of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education, Nanjing University of Posts and Telecommunications, Nanjing, China.
    Tian, Feng
    Institute of Signal Processing and Transmission, Key Lab of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education, Nanjing University of Posts and Telecommunications, Nanjing, China.
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Improved quantum genetic algorithm for competitive spectrum sharing in cognitive radios2012In: 2011 International Conference in Electrics, Communication and Automatic Control Proceedings / [ed] Ran Chen, Springer, 2012, p. 1203-1209Conference paper (Refereed)
    Abstract [en]

    This chapter investigates a kind of whole new approach to spectrum sharing in cognitive radio (CR) system, quantum-inspired approach. First, we improved Quantum Genetic Algorithm (QGA) by adding quantum crossover operator to overcome the shortcomings of the original QGA, easily falling into a local extremum when used to optimize the continuous functions with many extrema. We then propose a novel spectrum sharing scheme in noncooperative game for CR system based on our improved QGA. We use QGA as competitive strategies and provide simulation results that confirm the proposed schemes have better convergence rate and higher sum capacity than genetic algorithm (GA)-based scheme, namely at most 1 bit/s/Hz increase in capacity. The results demonstrate the effectiveness and the applicability of QGA in spectrum sharing in CR system.

  • 25.
    Lindberg, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Decision Support Systems: Diagnostics and Explanation methods: In the context of telecommunication networks2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis work, conducted at Ericsson Software Research, aims to recommend a system setup for a tool to help troubleshooting personal at network operation centres (NOC) who monitors the telecom network. This thesis examines several different artificial intelligence algorithms resulting in the conclusion that Bayesian networks are suitable for the aimed system. Since the system will act as a decision support system it needs to be able to explain how recommendations have been developed. Hence a number of explanation methods have been examined. Unfortunately no satisfactory method was found and thus a new method was defined, modified explanation tree (MET) which visually illustrates the variables of most interest in a so called tree structure. The method was implementation and after some initial testing the method has gained some positive first feedback from stakeholders. Thus the final recommendation consists of a system based on a Bayesian model where the gathered training data is collected earlier from the domain. The users will thus obtain recommendations for the top ranked cases and afterwards get the option to get further explanation regarding the specific cause. The explanation aims to give the user situation awareness and help him/her in the final action to solve the problem.                       

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    Decision Support Systems: Diagnostics and Explanation methods
  • 26.
    Lundström, Benjamin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    IT-säkerhet: Största IT-säkerhetshoten mot svenska företag och organisationer idag, samt kontemporära bekämpningsmetoder och verktyg mot dessa IT-säkerhetshot.2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A number of IT-related threats have emerged since the birth of internet. In the beginning they were harmless but over time they developed into fearsome criminal tools for economic purposes. The collective name for such code is Malware. An attacker has a vast variety of tools at their disposal for unauthorized access, depriving legitimate users of their access or in other ways practice criminal activity for economic gain among other things.

    Protective and Counter measures include Firewalls, different Analyze and Detection systems (IDS/IPS) and Chryptology. But in order to fully combat the IT-threats, Security education and Incident management is needed through incident planning, reports, documentation, backup and information classing.

    Contemporary threats of significance are elucidated. Stuxnet (2009), which halted the Iranian nuclear weapons research. Flamer (2010), a Cyber weapon developed for traceless information gathering. BlackEnergy (2015) and the attack on the power supply in the Ukraine. The DDoS-attack on Swedish media aswell as Petya (2016) which is the next gen Ransomeware.

    It’s vital for businesses and organizations to protect their most vital asset, information. Both against cybercriminals but also against the increasing threat of cyber weapons and cyberterrorism.

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  • 27.
    Manchester, Ian R
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Savkin, Andrey V
    Faruqi, Farhan A
    Method for optical-flow-based precision missile guidance2008In: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, Vol. 44, no 3, p. 835-851Article in journal (Refereed)
    Abstract [en]

    A new precision guidance law is presented for three-dimensional intercepts against a moving target In contrast to previously published guidance laws, it does not require knowledge of the range to the target. This makes it appropriate for use on platforms which have an imaging device, such as a video camera, as a primary sensor. We prove that with idealized dynamic model, the guidance law results in zero miss distance, and a formula is given for impact angle error which tends to zero as does target speed, making this method particularly suitable against slow moving targets. Computer simulations are used to test the law with a more realistic model, with a video camera and optical-flow algorithm providing target information. It is shown to perform well compared with another law from the literature, despite requiring less information.

  • 28.
    Mishra, Tapas Kumar
    et al.
    Srm University, Department of Computer Science Engineering, Amaravati, Andhra Pradesh, India.
    Sahoo, Kshira Sagar
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Srm University, Department of Computer Science Engineering, Amaravati, Andhra Pradesh, India.
    Bilal, Muhammad
    Hankuk University of Foreign Studies, Department of Computer Engineering, Yongin-si, South Korea.
    Shah, Sayed Chhattan
    Hankuk University of Foreign Studies, Department of Information and Communication Engineering, Yongin-si, South Korea.
    Mishra, Manas Kumar
    F. M. Autonomous College, Department of Computer Science, Balasore, Odisha, India.
    Adaptive congestion control mechanism to enhance TCP performance in cooperative IoV2023In: IEEE Access, E-ISSN 2169-3536, Vol. 11, p. 9000-9013Article in journal (Refereed)
    Abstract [en]

    One of the main causes of energy consumption in Internet of Vehicles (IoV) networks is an ill-designed network congestion control protocol, which results in numerous packet drops, lower throughput, and increased packet retransmissions. In IoV network, the objective to increase network throughput can be achieved by minimizing packets re- transmission and optimizing bandwidth utilization. It has been observed that the congestion control mechanism (i.e., the congestion window) can plays a vital role in mitigating the aforementioned challenges. Thus, this paper present a cross-layer technique to controlling congestion in an IoV network based on throughput and buffer use. In the proposed approach, the receiver appends two bits in the acknowledgment (ACK) packet that describes the status of the buffer space and link utilization. The sender then uses this information to monitor congestion and limit the transmission of packets from the sender. The proposed model has been experimented extensively and the results demonstrate a significantly higher network performance percentage in terms of buffer utilization, link utilization, throughput, and packet loss.

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  • 29.
    Nilsson, Thomas
    Umeå University, Faculty of Science and Technology, Computing Science.
    Distributed Multiple Access and Service Differentiation Algorithms for Wireless Networks2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Communicating over a wireless channel poses many unique challenges not found in wired communication because of the special characteristics of the wireless channel. The capacity in a wireless network is typically scarce as a result of the limited bandwidth and many distinct phenomenons, like attenuation and interference, that work destructively on the received signals.

    The Medium Access Control (MAC) layer is responsible for sharing this limited resource among the users. This allocation problem should be handled by considering the Quality of Service (QoS) requirements of each user as to maximize the utility. Efficient MAC algorithms are crucial in minimizing collisions between transmissions and thus achieving high utilization of the channel.

    This thesis focuses on conflict resolution and service differentiation algorithms for wireless local area networks, where there is no central control of the channel and each sender independently contends for access.

    In part I, we study three approaches to improve the IEEE 802.11(e) standards with focus on QoS. In the first approach, utility functions are considered, that model application preferences, to achieve service differentiation and maximize the aggregated utility. We provide algorithms for two subsidiary problems that arise from the maximization problem, and show that a near--optimal solution is found. In the second approach a collision detection algorithm for multicast transmissions is proposed, that increases the reliability for multicast compared to the protected unicast traffic. The third approach is an improved MAC algorithm for the QoS standard IEEE 802.11e. The improved algorithm outperforms the standard and achieves close to optimal performance for large number of scenarios, which significantly reduces the need of adjusting the contention parameters.

    In part II, we focus on channel bursting protocols that use noise bursts to resolve channel conflicts. These protocols is capable of achieving very low collision probability. We propose two new bursting protocols, that achieve very high channel utilization, and show that the bursting technique has good fairness properties and provides efficient support for service differentiation. We also show that it is possible to reduce the number of bursts without loosing performance.

    In part III, the optimal backoff distribution that minimizes the collision probability is derived. We then propose a heuristic backoff distribution with similar properties that yields high channel utilization. An extension for service differentiation is provided where the sizes of the backoff windows are adjusted.

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  • 30.
    Nilsson, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Jäntti, Riku
    Generic stationary backoff distributions for distributed multiple access control2014In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 56, no 3, p. 383-398Article in journal (Refereed)
    Abstract [en]

    In this paper, we study the characteristics of two different backoff schemes: one that maximizes the channel utilization and one that maximizes the probability of a successful transmission. Our results indicate that while the latter provides slightly lower channel utilization, its shape is much less sensitive to the number of contending nodes. That is, the channel utilization is kept almost constant for a very wide range of node densities if the backoff distribution has increasing shape. This motivates us to propose a simple heuristic backoff scheme called the Truncated Geometric Backoff Distribution (TGBD). We provide simple analytical expressions for the probability of a successful transmission and the channel utilization. We also show that the TGBD can easily be extended to support service differentiation by adjusting the window lengths, and we provide a simple approximation that gives the relative share of the capacity for a node in a priority class compared to nodes in other classes. This extended backoff scheme easily outperforms the much more complex Quality of Service (QoS) standard, IEEE802.11e EDCA. Finally, a two-stage backoff model, based on the TGBD, is proposed that further increases the probability of a successful transmission. Results indicate that the channel utilization is almost independent of the number of contending nodes.

  • 31. Ruffini, Stefano
    et al.
    Iovanna, Paola
    Forsman, Mats
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Thyni, Tomas
    A Novel SDN-Based Architecture to Provide Synchronization as a Service in 5G Scenarios2017In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 55, no 3, p. 210-216Article in journal (Refereed)
    Abstract [en]

    Moving toward 5G, network synchronization is expected to play a key role in the successful deployment of the new mobile communication networks. This article presents an application of SDN (software defined networking) and NFV (network function virtualization) principles to the network synchronization area, making it possible to offer synchronization as a service. The approach is based on defining a harmonization layer that orchestrates radio and heterogeneous transport domains by means of a suitable subset of abstracted information exchanged among the domains, and by making use of virtualized synchronization functions.

  • 32.
    Rönnbäck, Sven
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wernersson, Åke
    LiTH.
    Range statistics and suppressing snowflakes detects for laser range finders in snowfall2010In: Intelligent systems: from theory to practice / [ed] Vassil Sgurev, Mincho Hadjiski and Janusz Kacprzyk, Berlin Heidelberg: Springer , 2010, p. 261-277Chapter in book (Refereed)
    Abstract [en]

    This paper presents statistics on registrations from laser range finders in snowfall. The sensors are standard laser range finders in robotics, the LMS200 and the URG-04LX. Three different working cases were identified for the pulsed laser range finder. 1) Normal operation with background objects present within the range of the sensor. 2) Close range objects where ranges to objects are shorter than the pulse length. 3) Free-space in the background. The findings are summarized as: •  Two laser range finders have been used, one that sends out a pulsed wide beam and one with a modulated narrow laser beam. The narrow beam laser has better penetration between the snowflakes. •  Median filtering shows a substantial reduction in snowflake detects. •  The gamma distribution describes fairly well the range distribution of detected snowflakes. •  In an intense snowfall where about 24% of the ranges detected snowflakes. •  A time-polar median filter showed good results in suppressing snowflakes in range data.

  • 33.
    Saremi, Amin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Spatial audio signal processing for speech telecommunication inside vehicles2022In: Advances in fundamental and applied research on spatial audio / [ed] Brian F.G. Katz; Piotr Majdak, London: InTech, 2022, p. 175-192Chapter in book (Refereed)
    Abstract [en]

    Since the introduction of hands-free telephony applications and speech dialog systems in automotive industry in 1990s, microphones have been mounted in car cabins to capture, and route the driver's speech signals to the corresponding telecommunication networks. A car cabin is a noisy and reverberant environment where engine activity, structural vibrations, road bumps, and cross-talk interferences can add substantial amounts of acoustic noise to the captured speech signal. To enhance the speech signal, a variety of real-time signal enhancement methods such as acoustic echo cancellation, noise reduction, de-reverberation, and beamforming are typically applied. Moreover, the recent introduction of AI-driven online voice assistants in automotive industry has resulted in new requirements on speech signal enhancement methods to facilitate accurate speech recognition. In this chapter, we focus on spatial filtering techniques that are designed to spatially enhance signals that arrive from certain directions while attenuating signals that originate from other locations. The fundamentals of conventional beamforming and echo cancelation are explained and are accompanied by some real-world examples. Moreover, more recent techniques (namely blind source segregation, and neural-network based adaptive beamforming) are presented in the context of automotive applications. This chapter provides the readers with both fundamental and hands-on insights into the fast-growing field of automotive speech signal processing.

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  • 34.
    Sjödin, Tomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Gacanin, Haris
    Department of Electrical and Communication Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan.
    Adachi, Fumiyuki
    Department of Electrical and Communication Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan.
    Two-slot channel estimation for analog network coding based on OFDM in a frequency-selective fading channel2010In: IEEE Vehicular Technology Conference, IEEE, 2010, p. 1-5Conference paper (Refereed)
    Abstract [en]

    Recently, broadband analog network coding (ANC) was introduced to utilize high-data rate transmission over the wireless - frequency selective fading - channel. However, ANC requires the knowledge of channel state information (CSI) for self-information removal and coherent signal detection. In this paper, we propose a two-slot pilot-assisted CE for bi-directional broadband ANC. In the first slot, two users transmit their respective pilots to the relay, where the users' pilot signals are designed to avoid the interference and consequently, allow the relay to estimate the CSIs from both users. During the second slot the relay broadcast its pilot signal to both users that estimate the corresponding CSIs. It was shown by computer simulation that, even with imperfect CSI, the BER performance of broadband ANC gives a satisfactory performance for a low and moderate mobile terminal speed in a frequency-selective fading channel.

  • 35.
    Sjöström, Daniel
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Undersökning av Carlshöjdsskolans trådlösa infrastruktur, Analysis of the wireless infrastructure in Carlshöjdsskolan2014Independent thesis Basic level (university diploma), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    WLAN is an exciting technology that is about to take over the market completely for the simple reason that it is very easily accessible. This makes it harder to spot places where the signal does not reach and therefore have developed software that makes it possible to simulate a visual coverage map.

    The goal of this paper is to describe techniques, noise and emissions that occur within the WLAN. The survey and comparison is made on Carlshöjdsskolans wireless infrastructure where there's a dozen accesspoints.

  • 36.
    Sköld, Jonathan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Augmented Visualisation of Radio Path Propagation2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Computational electromagnetic (CEM) simulations are an important tool in the deployment and development of wireless communications. By utilising a MATLAB-based CEM simulator this thesis aims to develop and expand the simulation toolboxes for visualising radio path propagation with a focus on indoor environment and using new technologies such as virtual reality (VR). The vision is to be able to find new ways of exploring radio deployments to find their strengths and weaknesses in different environments. The goal of the work is to create a visualisation application using Unreal Engine that can interface with the MATLAB-based CEM simulator. The developed application can interpret spatial simulation-domains, ray-tracing/path propagation data, and scalar fields. In addition, the application can construct 3D-worlds from the spatial data and display radio path propagation in VR. Values for scalar fields can be viewed when selecting specific parameters, however, potential improvements will allow for the visualisation of entire scalar fields. There are many opportunities for future work from this thesis, both immediate small improvements and larger feature additions.

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    Master's_Thesis_Jonathan_Sköld.pdf
  • 37.
    Song, Yi
    et al.
    Laboratory of Photonics and Microwave Engineering, School of Information and Communication Technology, Royal Institute of Technology, Electrum 229, Kista, Sweden.
    Wang, Jing
    Laboratory of Photonics and Microwave Engineering, School of Information and Communication Technology, Royal Institute of Technology, Electrum 229, Kista, Sweden.
    Li, Qiang
    Laboratory of Photonics and Microwave Engineering, School of Information and Communication Technology, Royal Institute of Technology, Electrum 229, Kista, Sweden.
    Yan, Min
    Laboratory of Photonics and Microwave Engineering, School of Information and Communication Technology, Royal Institute of Technology, Electrum 229, Kista, Sweden.
    Qiu, Min
    Laboratory of Photonics and Microwave Engineering, School of Information and Communication Technology, Royal Institute of Technology, Electrum 229, Kista, Sweden.
    Broadband coupler between silicon waveguide and hybrid plasmonic waveguide2010In: Optics Express, E-ISSN 1094-4087, Vol. 18, no 12, article id 13173Article in journal (Refereed)
    Abstract [en]

    Efficient broadband coupling of light between a dielectric waveguide and a hybrid plasmonic waveguide is investigated theoretically. A plasmonic linear taper is used as a coupler which connects the two types of waveguides. Broadband coupling is realized by such a compact plasmonic taper with a length of only 0.4μm, which achieves a coupling efficiency of 70% (1.5dB) at the 1.55μm telecommunication wavelength.

  • 38. Thylen, Lars
    et al.
    Holmström, Petter
    Wosinski, Lech
    Jaskorzynska, Bozena
    Naruse, Makoto
    Kawazoe, Tadashi
    Ohtsu, Motoichi
    Yan, Min
    Laboratory of Photonics and Microwave Engineering, Royal Institute of Technology (KTH), Kista, Sweden.
    Fiorentino, Marco
    Westergren, Urban
    Nanophotonics for low-power switches2013In: Optical fiber telecommunications VIA: components and subsystems / [ed] Ivan P. Kaminow; Tingye Li; Alan E. Willner, Oxford: Academic Press, 2013, 6, p. 205-241Chapter in book (Refereed)
    Abstract [en]

    This chapter treats several approaches for employing nanophotonics or near-nanophotonics concepts to create low-power switches. The partly interrelated issues of low-power dissipation and small device footprint are elucidated and figures of merit for switches formulated. Both optically and electronically controlled optical switches are treated and the crucial role of material development emphasized, illustrated by several examples, including both theoretical analysis of switch concepts and experimentally realized switches. Thus, electronically controlled switches based on hybrid, metamaterial, and nanoparticle plasmonics, electrooptic polymers as well as switches based on silicon and photonic crystals are discussed. The all-optical switches focus on third-order nonlinear effects and carrier-induced refractive index changes in III–V materials, as well as on emerging concepts of near-field-coupled quantum-dot switches. A brief comparison to electronic switches is done.

  • 39.
    Townend, Paul
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Wo, Tianyu
    Beihang University, China.
    Welcome message from the general chairs of IEEE JCC 20222022In: Proceedings: 2022 IEEE 13th International Conference on Joint Cloud Computing, IEEE Computer Society, 2022, p. VIII-VIIIChapter in book (Other academic)
  • 40.
    ur Rehman, Shafiq
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Liu, Li
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    iFeeling: vibrotactile rendering of human emotions on mobile phones2010In: Mobile multimedia processing: fundamentals, methods, and applications, Springer, 2010, p. 1-20Conference paper (Refereed)
    Abstract [en]

    Today, the mobile phone technology is mature enough to enable us to effectively interact with mobile phones using our three major senses namely, vision, hearing and touch. Similar to the camera, which adds interest and utility to mobile experience, the vibration motor in a mobile phone could give us a new possibility to improve interactivity and usability of mobile phones. In this chapter, we show that by carefully controlling vibration patterns, more than 1-bit information can be rendered with a vibration motor. We demonstrate how to turn a mobile phone into a social interface for the blind so that they can sense emotional information of others. The technical details are given on how to extract emotional information, design vibrotactile coding schemes, render vibrotactile patterns, as well as how to carry out user tests to evaluate its usability. Experimental studies and users tests have shown that we do get and interpret more than one bit emotional information. This shows a potential to enrich mobile phones communication among the users through the touch channel.

  • 41.
    ur Réhman, Shafiq
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Expressing emotions through vibration for perception and control2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis addresses a challenging problem: “how to let the visually impaired ‘see’ others emotions”. We, human beings, are heavily dependent on facial expressions to express ourselves. A smile shows that the person you are talking to is pleased, amused, relieved etc. People use emotional information from facial expressions to switch between conversation topics and to determine attitudes of individuals. Missing emotional information from facial expressions and head gestures makes the visually impaired extremely difficult to interact with others in social events. To enhance the visually impaired’s social interactive ability, in this thesis we have been working on the scientific topic of ‘expressing human emotions through vibrotactile patterns’.

    It is quite challenging to deliver human emotions through touch since our touch channel is very limited. We first investigated how to render emotions through a vibrator. We developed a real time “lipless” tracking system to extract dynamic emotions from the mouth and employed mobile phones as a platform for the visually impaired to perceive primary emotion types. Later on, we extended the system to render more general dynamic media signals: for example, render live football games through vibration in the mobile for improving mobile user communication and entertainment experience. To display more natural emotions (i.e. emotion type plus emotion intensity), we developed the technology to enable the visually impaired to directly interpret human emotions. This was achieved by use of machine vision techniques and vibrotactile display. The display is comprised of a ‘vibration actuators matrix’ mounted on the back of a chair and the actuators are sequentially activated to provide dynamic emotional information. The research focus has been on finding a global, analytical, and semantic representation for facial expressions to replace state of the art facial action coding systems (FACS) approach. We proposed to use the manifold of facial expressions to characterize dynamic emotions. The basic emotional expressions with increasing intensity become curves on the manifold extended from the center. The blends of emotions lie between those curves, which could be defined analytically by the positions of the main curves. The manifold is the “Braille Code” of emotions.

    The developed methodology and technology has been extended for building assistive wheelchair systems to aid a specific group of disabled people, cerebral palsy or stroke patients (i.e. lacking fine motor control skills), who don’t have ability to access and control the wheelchair with conventional means, such as joystick or chin stick. The solution is to extract the manifold of the head or the tongue gestures for controlling the wheelchair. The manifold is rendered by a 2D vibration array to provide user of the wheelchair with action information from gestures and system status information, which is very important in enhancing usability of such an assistive system. Current research work not only provides a foundation stone for vibrotactile rendering system based on object localization but also a concrete step to a new dimension of human-machine interaction.

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  • 42.
    ur Réhman, Shafiq
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Khan, Muhammad Sikandar Lal
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Liu, Li
    Nanjing University of Posts and Telecommunications, Nanjing, China.
    Li, Haibo
    Media technology and interaction design, Royal Institute of Technology (KTH), Sweden; Nanjing University of Posts and Telecommunications, Nanjing, China.
    Vibrotactile TV for immersive experience2014In: Signal and Information Processing Association Annual Summit and Conference (APSIPA), 2014 Asia-Pacific, 2014Conference paper (Refereed)
    Abstract [en]

    Audio and video are two powerful media forms to shorten the distance between audience/viewer and actors or players in the TV and films. The recent research shows that today people are using more and more multimedia contents on mobile devices, such as tablets and smartphones. Therefore, an important question emerges - how can we render high-quality, personal immersive experiences to consumers on these systems? To give audience an immersive engagement that differs from `watching a play', we have designed a study to render complete immersive media which include the `emotional information' based on augmented vibrotactile-coding on the back of the user along with audio-video signal. The reported emotional responses to videos viewed with and without haptic enhancement, show that participants exhibited an increased emotional response to media with haptic enhancement. Overall, these studies suggest that the effectiveness of our approach and using a multisensory approach increase immersion and user satisfaction.

  • 43.
    Vivas, Fulvio Yesid
    et al.
    Departamento de Telemática, Universidad del Cauca, Popayán, Cauca, Colombia.
    Caicedo, Oscar Mauricio
    Departamento de Telemática, Universidad del Cauca, Popayán, Cauca, Colombia.
    Nieves, Juan Carlos
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A semantic and knowledge-based approach for handover management2021In: Sensors, E-ISSN 1424-8220, Vol. 21, no 12, article id 4234Article in journal (Refereed)
    Abstract [en]

    Handover Management (HM) is pivotal for providing service continuity, enormous reliabil-ity and extreme-low latency, and meeting sky-high data rates, in wireless communications. Current HM approaches based on a single criterion may lead to unnecessary and frequent handovers due to a partial network view that is constrained to information about link quality. In turn, HM approaches based on multicriteria may present a failure of handovers and wrong network selection, decreasing the throughput and increasing the packet loss in the network. This paper proposes SIM-Know, an approach for improving HM. SIM-Know improves HM by including a Semantic Information Model (SIM) that enables context-aware and multicriteria handover decisions. SIM-Know also introduces a SIM-based distributed Knowledge Base Profile (KBP) that provides local and global intelligence to make contextual and proactive handover decisions. We evaluated SIM-Know in an emulated wireless network. When the end-user device moves at low and moderate speeds, the results show that our approach outperforms the Signal Strong First (SSF, single criterion approach) and behaves similarly to the Analytic Hierarchy Process combined with the Technique for Order Preferences by Similarity to the Ideal Solution (AHP-TOPSIS, multicriteria approach) regarding the number of handovers and the number of throughput drops. SSF outperforms SIM-Know and AHP-TOPSIS regarding the handover latency metric because SSF runs a straightforward process for making handover decisions. At high speeds, SIM-Know outperforms SSF and AHP-TOPSIS regarding the number of handovers and the number of throughput drops and, further, improves the throughput, delay, jitter, and packet loss in the network. Considering the obtained results, we conclude that SIM-Know is a practical and attractive solution for cognitive HM.

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  • 44. Wu, Jinsong
    et al.
    Bisio, Igor
    Gniady, Chris
    Hossain, Ekram
    Valla, Massimo
    Li, Haibo
    Umeå University, Faculty of Science and Technology, Umeå Centre for Interaction Technology (UCIT). KTH, Stockholm, Sweden.
    Context-aware networking and communications: part 22014In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 52, no 8, p. 64-65Article in journal (Other academic)
  • 45. Zhu, Yinian
    et al.
    Shum, Ping
    Bay, Hui-Wen
    Yan, Min
    Network Technology Research Center, Nanyang Technological University, Research TechnoPlaza, Singapore.
    Yu, Xia
    Hu, Juanjuan
    Hao, Jianzhong
    Lu, Chao
    Strain-insensitive and high-temperature long-period gratings inscribed in photonic crystal fiber2005In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 30, no 4, p. 367-369Article in journal (Refereed)
    Abstract [en]

    We fabricate and demonstrate strain-insensitive and high-temperature long-period gratings in endlessly single-mode photonic crystal fiber by use of focused pulses of a CO2 laser and a periodic stress relaxation technique without geometrical deformation and elongation of the fiber. The thermal dependence of mode coupling at 1299.59 nm is 10.9 pm/°C from 24 to 992 °C, whereas the coefficient of strain sensitivity is −0.192 pm/𝜇𝜖-0.192 pm/−0.192 pm/𝜇𝜖 up to the maximum strain of 2.74%𝜖2.74%−0.192 pm/𝜖. It is found for what is believed to be the first time that, in contrast with the traditional fiber case, the coupling resonance shifts toward shorter wavelengths under applied strain, indicating that the refractive index of the core is decreased as a result of the rebuilding of tension attributed to the stress-elastic effect, and the cladding modes is highly dispersive because of airholes arranged in the fiber cladding.

1 - 45 of 45
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