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  • 101. Cheng, Shi
    et al.
    Öjefors, E.
    Magrell, J.
    Hjort, Klas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Materialvetenskap. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik. Materialvetenskap.
    Rydberg, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Inverted-F Antenna for 3D integrated wireless sensor applications2007Konferensbidrag (Refereegranskat)
  • 102.
    Cheng, Shi
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System. Signals and systems.
    Öjefors, Erik
    Hallbjörner, Paul
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Ogden, Sam
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik. Materials Science.
    Magrell, J
    Hjort, Klas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik. Materials Science.
    Rydberg, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Body surface backed flexible antennas for 17 GHz wireless body area networks sensor applications2007Konferensbidrag (Refereegranskat)
  • 103.
    Cheng, Shi
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrovågs- och terahertzteknik.
    Öjefors, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Hallbjörner, Paul
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrovågs- och terahertzteknik.
    Ogden, Sam
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik.
    Margell, J.
    Hjort, Klas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik.
    Rydberg, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrovågs- och terahertzteknik.
    Body Surface backed flexible antennas for 17 GHz wireless body area networks sensor applications2007Konferensbidrag (Refereegranskat)
  • 104.
    Cheng, Shi
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Öjefors, Erik
    Magrell, J
    Hjort, Klas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik.
    Rydberg, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Inverted-F antenna for 3D integrated wireless sensor applications2007Konferensbidrag (Refereegranskat)
  • 105. Chockalingam, Sabarathinam
    et al.
    Pieters, Wolter
    Teixeira, André
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Khakzad, Nima
    Van Gelder, Pieter
    Combining Bayesian Networks and Fishbone Diagrams to Distinguish between Intentional Attacks and Accidental Technical Failures2018Ingår i: Proc. Graph. Model. Secur., 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Because of modern societies’ dependence on industrial control systems, adequate response to system failures is essential. In order to take appropriate measures, it is crucial for operators to be able to distinguish between intentional attacks and accidental technical failures. However, adequate decision support for this matter is lacking. In this paper, we use Bayesian Networks (BNs) to distinguish between intentional attacks and accidental technical failures, based on contributory factors and observations (or test results). To facilitate knowledge elicitation, we use extended shbone diagrams for discussions with experts, and then translate those into the BN formalism. We demonstrate the methodology using an example in a case study from the water management domain. M4 - Citavi

  • 106.
    Chong, Michelle S.
    et al.
    KTH Royal Inst Technol, Div Decis & Control Syst, Stockholm, Sweden.
    Sandberg, Henrik
    KTH Royal Inst Technol, Div Decis & Control Syst, Stockholm, Sweden.
    Teixeira, André M.H.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    A Tutorial Introduction to Security and Privacy for Cyber-Physical Systems2019Ingår i: 2019 18Th European Control Conference (ECC), IEEE, 2019, s. 968-978Konferensbidrag (Refereegranskat)
    Abstract [en]

    This tutorial provides a high-level introduction to novel control-theoretic approaches for the security and privacy of cyber-physical systems (CPS). It takes a risk-based approach to the problem and develops a model framework that allows us to introduce and relate many of the recent contributions to the area. In particular, we explore the concept of risk in the context of CPS under cyber-attacks, paying special attention to the characterization of attack scenarios and to the interpretation of impact and likelihood for CPS. The risk management framework is then used to give an overview of and map different contributions in the area to three core parts of the framework: attack scenario description, quantification of impact and likelihood, and mitigation strategies. The overview is by no means complete, but it illustrates the breadth of the problems considered and the control-theoretic solutions proposed so far.

  • 107. Ciuonzo, Domenico
    et al.
    Rossi, Pierluigi Salvo
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Massive MIMO Channel-Aware Decision Fusion2015Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 63, nr 3, s. 604-619Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we provide a study of channel-aware decision fusion (DF) over a "virtual" multiple-input multiple-output (MIMO) channel in the large-array regime at the DF center (DFC). The considered scenario takes into account channel estimation and inhomogeneous large-scale fading between the sensors and the DFC. The aim is the development of (widely) linear fusion rules, as opposed to the unsuitable optimum log-likelihood ratio (LLR). The proposed rules can effectively benefit from performance improvement via a large array, differently from existing suboptimal alternatives. Performance evaluation, along with theoretical achievable performance and complexity analysis, is presented. Simulation results are provided to confirm the findings. Analogies and differences with uplink communication in a multiuser (massive) MIMO scenario are underlined.

  • 108.
    Ciuonzo, Domenico
    et al.
    Department of Industrial and Information Engineering, Second University of Naples, Italien.
    Salvo Rossi, Pierluigi
    Department of Industrial and Information Engineering, Second University of Naples, Italien.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Massive MIMO meets decision fusion: Decode-and-fuse vs. decode-then-fuse2014Ingår i: 2014 IEEE 8TH Sensor Array and Multichannel Signal Processing Workshop (SAM), 2014, s. 265-268Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study channel-aware decision fusion over a multiple-input multiple-output (MIMO) channel in the large-array regime at the decision-fusion center (DFC). Inhomogeneous large-scale fading between the sensors and the DFC is consider in addition to the small-scale fading, and pilot-based channel estimation is performed at the DFC. Linear processing techniques are analyzed in order to design low-complexity alternatives to the optimum log-likelihood ratio test (LLRT). Performance evaluation based on Monte Carlo simulations are presented.

  • 109.
    Danielsson, Thomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    DMX-communication over Bluetooth low energy mesh network2019Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Bluetooth har länge varit standardprotokollet för kommunikation mellan två stycken enheter. 2017 kom tillägget med mesh till Bluetooth. Mesh innebär att andra enheten i närheten ska skicka vidare meddelanden och därigenom tillåta kommunikation mellan enheter som är utanför direkt radiokontakt. DMX är ett protokoll som används inom ljus- och sceneffekter. Bluetooth mesh är utformat för att skicka små datamängder som till exempel sensordata eller styra glödlampor. Denna uppsats kommer utvärdera om det är användbart att skicka DMX-data över Bluetooth mesh.

    En implementation gjordes på Bluetooth utvecklingskort och resultatet visar på en signifikant fördröjning och med hög varians vid överföring av alla DMX-kanaler, vilket innebär att denna implementation inte är användbar vid många användningsområden. Men trots det kan den vid vissa fall vara användningsbar, mycket till hjälp av Bluetooths billiga och utbyggda ekosystem av produkter och tilläggsfunktioner. Eftersom Bluetooth mesh byggs in i en del befintliga byggnader kan de uppoffringar man får göra vid överföringar av DMX-data vara acceptabel då man kan uttnyttja befintliga nät. Strömförbrukningen ökar avsevärt vid mesh jämfört med klassisk lågenergi Bluetooth då mesh måste skanna radiotrafiken konstant. Vid implementationen av lågenergi noder kan dock radio vara i stand-by och starta endast vid speciella tidpunkter och man kan därigenom få avsevärt lägre strömförbrukning, med uppoffringen att DMX-datan inte kan överföras omgående. Det visade sig också att noduppställningen kraftigt påverkade variansen i överföringshastighet och att detta måste ta i hänsyn vid valet om DMX över Bluetooth mesh är användbart i just det fallet.

  • 110.
    Dey, Subhrakanti
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Chiuso, A
    Schenato, L
    Linear Encoder-decoder-controller design over channels with packet loss and quantization noise2015Konferensbidrag (Refereegranskat)
  • 111.
    Dey, Subhrakanti
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Chiuso, A
    Department of Information Engineering, University of Padova, Italien.
    Schenato, L
    Department of Information Engineering, University of Padova, Italien.
    Remote estimation subject to packet loss and quantization noise2013Konferensbidrag (Refereegranskat)
  • 112.
    Dey, Subhrakanti
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Chiuso, Alessandro
    Univ Padua, Dept Informat Engn, I-35131 Padua, Italy..
    Schenato, Luca
    Univ Padua, Dept Informat Engn, I-35131 Padua, Italy..
    Feedback Control Over Lossy SNR-Limited Channels: Linear Encoder-Decoder-Controller Design2017Ingår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 62, nr 6, s. 3054-3061Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we consider the problem of encoding and decoding codesign for linear feedback control of a scalar, possibly unstable, stochastic linear system when the sensed signal is to be transmitted over a finite capacity communication channel. In particular, we consider a limited capacity channel which transmits quantized data and is subject to packet losses. We first characterize the optimal strategy when perfect channel feedback is available, i.e., the transmitter has perfect knowledge of the packet loss history. This optimal scheme, innovation forwarding hereafter, is reminiscent of differential pulse-code modulation schemes adapted to deal with state space models, and is strictly better than a scheme which simply transmits the measured data, called measurement forwarding (MF) hereafter. Comparison in terms of control cost as well as of critical regimes, i.e., regimes where the cost is not finite, are provided. We also consider and compare two popular suboptimal schemes from the existing literature, based on 1) state estimate forwarding and 2) measurement forwarding, which ignore quantization effects in the associated estimator and controller design. In particular, it is shown that surprisingly the suboptimal MF strategy is always better then the suboptimal state forwarding strategy for small signal-to-quantization-noise-ratios.

  • 113.
    Dey, Subhrakanti
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Chiuso, Alessandro
    Department of Information Engineering, University of Padova, Italien.
    Schenato, Luca
    Department of Information Engineering, University of Padova, Italien.
    Remote estimation with noisy measurements subject to packet loss and quantization noise2014Ingår i: IEEE Transactions on Control of Network Systems, Vol. 1, nr 3, s. 204-217Artikel i tidskrift (Refereegranskat)
  • 114. Ding, K
    et al.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Quevedo, Daniel E
    Department of Electrical Engineering, Paderborn University, Tyskland.
    Shi, L
    Stochastic game in remote estimation under DoS attacks2017Ingår i: IEEE Control Systems Letters, Vol. 1, nr 1, s. 146-151Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This letter studies remote state estimation under denial-of-service (DoS) attacks. A sensor transmits its local estimate of an underlying physical process to a remote estimator via a wireless communication channel. A DoS attacker is capable to interfere the channel and degrades the remote estimation accuracy. Considering the tactical jamming strategies played by the attacker, the sensor adjusts its transmission power. This interactive process between the sensor and the attacker is studied in the framework of a zero-sum stochastic game. To derive their optimal power schemes, we first discuss the existence of stationary Nash equilibrium for this game. We then present the monotone structure of the optimal strategies, which helps reduce the computational complexity of the stochastic game algorithm. Numerical examples are provided to illustrate the obtained results.

  • 115.
    Ding, K
    et al.
    HongKong University of Science and Technology.
    Quevedo, Daniel E
    University of Paderborn, Tyskland.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Shi, Ling
    HongKong University of Science and Technology.
    Cross-layer design for remote estimation under DoS attack2016Konferensbidrag (Refereegranskat)
  • 116. Ding, K
    et al.
    Ren, X
    Quevedo, Daniel
    Department of Electrical Engineering, Paderborn University, Tyskland.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Shi, L
    DoS attacks on remote state estimation with asymmetric information2019Ingår i: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 6, nr 2, s. 653-666Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract: In this paper, we consider remote state estimation in an adversarial environment. A sensor forwards local state estimates to a remote estimator over a vulnerable network, which may be congested by an intelligent denial-of-service (DoS) attacker. It is assumed that the acknowledgement information from the remote estimator to the sensor is hidden from the attacker, which thus leads to asymmetric information between the sensor and attacker. Considering the infinite-time goals of the two agents and their asymmetric information structure, we model the conflicting nature between the sensor and the attacker by a stochastic Bayesian game. Solutions for this game under two different structures of public information history are investigated, that is, the open-loop structure (in which players cannot observe their opponents' play) and the closed-loop one (in which players can observe the play causally). For the open-loop history case, the original game problem is transformed into a static Bayesian game. We provide the unique mixed-strategy equilibrium explicitly for this game, and analyze the sensor's advantages brought by the extra information. When it comes to the closed-loo

  • 117.
    Ding, Kemi
    et al.
    Hong Kong Univ Sci & Technol, Dept Elect & Comp Engn, Hong Kong, Hong Kong, Peoples R China.
    Li, Yuzhe
    Univ Alberta, Dept Elect & Comp Engn, Edmonton, AB, Canada.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Shi, Ling
    Hong Kong Univ Sci & Technol, Dept Elect & Comp Engn, Hong Kong, Hong Kong, Peoples R China.
    Multi-sensor Transmission Management for Remote State Estimation under Coordination2017Ingår i: IFAC-PapersOnLine, ISSN 1045-0823, E-ISSN 1797-318X, Vol. 50, nr 1, s. 3829-3834Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper considers the remote state estimation in a cyber-physical system (CPS) using multiple sensors. The measurements of each sensor are transmitted to a remote estimator over a shared channel, where simultaneous transmissions from other sensors are regarded as interference signals. In such a competitive environment, each sensor needs to choose its transmission power for sending data packets taking into account of other sensors’ behavior. To model this interactive decision-making process among the sensors, we introduce a multi-player non-cooperative game framework. To overcome the inefficiency arising from the Nash equilibrium (NE) solution, we propose a correlation policy, along with the notion of correlation equilibrium (CE). An analytical comparison of the game value between the NE and the CE is provided, with/without the power expenditure constraints for each sensor. Also, numerical simulations demonstrate the comparison results.

  • 118.
    Ding, Kemi
    et al.
    Hong Kong Univ Sci & Technol, Dept Elect & Comp Engn, Hong Kong, Hong Kong, Peoples R China..
    Li, Yuzhe
    Hong Kong Univ Sci & Technol, Dept Elect & Comp Engn, Hong Kong, Hong Kong, Peoples R China..
    Quevedo, Daniel E.
    Univ Paderborn, Dept Elect Engn, Paderborn, Germany..
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Shi, Ling
    Hong Kong Univ Sci & Technol, Dept Elect & Comp Engn, Hong Kong, Hong Kong, Peoples R China..
    A multi-channel transmission schedule for remote state estimation under DoS attacks2017Ingår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 78, s. 194-201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper considers a cyber-physical system (CPS) under denial-of-service (DoS) attacks. The measurements of a sensor are transmitted to a remote estimator over a multi-channel network, which may be congested by a malicious attacker. Among these multiple communication paths with different characteristics and properties at each time step, the sensor needs to choose a single channel for sending data packets while reducing the probability of being attacked. In the meanwhile, the attacker needs to decide the target channel to jam under an energy budget constraint. To model this interactive decision making process between the two sides, we formulate a two-player zero-sum stochastic game framework. A Nash Q-learning algorithm is proposed to tackle the computation complexity when solving the optimal strategies for both players. Numerical examples are provided to illustrate the obtained results.

  • 119.
    Ding, Kemi
    et al.
    Hong Kong Univ Sci & Technol, Dept Elect & Comp Engn, Kowloon, Hong Kong, Peoples R China..
    Quevedo, Daniel E.
    Paderborn Univ, Dept Elect Engn, Paderborn, Germany..
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Shi, Ling
    Hong Kong Univ Sci & Technol, Dept Elect & Comp Engn, Kowloon, Hong Kong, Peoples R China..
    A Secure Cross-Layer Design for Remote Estimation under DoS Attack: When Multi-sensor meets Multi-channel2016Ingår i: 2016 IEEE 55Th Conference On Decision And Control (CDC), New York: IEEE, 2016, s. 6297-6302Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper considers security issues of a cyberphysical system (CPS) under denial-of-service (DoS) attacks. The measurements of multiple sensors are transmitted to a remote estimator over a multi-channel network, which may be congested by an intelligent attacker. Aiming at improving the estimation accuracy, we first propose a novel aggregation scheme for the estimator to produce accurate state estimates, from which we obtain a closed-form expression of the expected estimation error covariance. We further develop a sensor attacker game to design the cooperative and defensive channel selection strategy, which avoids the sensors being attacked in an energy-efficient way. Numerical examples are provided to illustrate the developed results.

  • 120.
    Ding, Lianghui
    et al.
    Institute of Image Communication and Network Engineering, Shanghai Jiao Tong University, Shanghai, China.
    Wu, Ping
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Pan, Zhiwen
    National Mobile Communication Research Laboratory, Southeast University, Nanjing, China.
    You, Xiaohu
    National Mobile Communication Research Laboratory, Southeast University, Nanjing, China.
    Lifetime optimization for wireless multihop networks with network coding2012Ingår i: 2012 International Conference on Wireless Communications and Signal Processing (WCSP), October 25-27, 2012, Huangshan, Kina, 2012Konferensbidrag (Refereegranskat)
  • 121.
    Ding, Lianghui
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Wu, Ping
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Wang, Hao
    National Mobile Communications Research Laboratory, Southeast University, Nanjing, China.
    Pan, Zhiwen
    National Mobile Communications Research Laboratory, Southeast University, Nanjing, China.
    Wu, Xiaohu
    National Mobile Communications Research Laboratory, Southeast University, Nanjing, China.
    Lifetime maximization with inter-session network coding in energy constrained wireless networks2011Ingår i: IEEE 73rd Vehicular Technology Conference (VTC 2011-Spring), Budapest, Ungern, 2011Konferensbidrag (Refereegranskat)
  • 122. Ding, Lianghui
    et al.
    Wu, Ping
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Wang, Hao
    National Mobile Communications Research Laboratory, Southeast University, Nanjing, China.
    Pan, Zhiwen
    National Mobile Communication Research Laboratory, Southeast University, Nanjing, China.
    You, Xiaohu
    National Mobile Communications Research Laboratory, Southeast University, Nanjing, China.
    Energy minimization in wireless multihop networks using two-way network coding2011Ingår i: IEEE 73rd Vehicular Technology Conference (VTC-2011-Spring), Budapest, Ungern, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    The total energy minimization in wireless multihop networks using two-way network coding is investigated in this paper. The problem is first formulated as a linear programming problem, then decomposed into two sub-problems using the Lagrangian decomposition, and finally solved with the subgradient method. After that, the backpressure based algorithm is proposed to solve the problem in a distributed manner. The performance of the algorithm is evaluated first in a simple topology for analysis and then in a random topology with different number of flows for practical consideration. Simulation results show that the convergence time increases as the number of nodes in the network, and the energy cost per packet can be saved up to 30% by using two-way network coding.

  • 123.
    Ding, Lianghui
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Wu, Ping
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Wang, Hao
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Pan, Zhiwen
    National Mobile Communication Research Laboratory, Southeast University, Nanjing, China.
    You, Xiaohu
    National Mobile Communication Research Laboratory, Southeast University, Nanjing, China.
    Flow augmenting routing with network coding for lifetime maximization in wireless networks2010Ingår i: 5th International ICST Conference on Communications and Networking in China (ChinaCom'10), Beijing, China, 2010Konferensbidrag (Refereegranskat)
  • 124.
    Ding, Liang-Hui
    et al.
    Institute of Image Communication and Network Engineering, Shanghai Jiao Tong University, Shanghai, Kina.
    Wu, Ping
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Wang, Hao
    National Mobile Communication Research Laboratory, Southeast University, Nanjing, Kina.
    Pan, ZhiWen
    National Mobile Communication Research Laboratory, Southeast University, Nanjing, Kina.
    You, XiaoHu
    National Mobile Communication Research Laboratory, Southeast University, Nanjing, Kina.
    Lifetime maximization routing with network coding in wireless multihop networks2013Ingår i: SCIENCE CHINA-INFORMATION SCIENCES, ISSN 1674-733X, Vol. 56, nr 2, s. 1-15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we consider the lifetime maximization routing with network coding in wireless multihop networks. We first show that lifetime maximization with network coding is different from pure routing, throughput maximization with network coding and energy minimization with network coding. Then we formulate lifetime maximization problems in three different cases of (i) no network coding, (ii) two-way network coding, and (iii) overhearing network coding. To solve these problems, we use flow augmenting routing (FA) for the first case, and then extend the FA with network coding (FANC) by using energy minimized one-hop network coding. After that, we investigate the influence of parameters of FANC, evaluate the performance of FANC with two-way and overhearing network coding schemes and compare it with that without network coding under two different power control models, namely, protocol and physical ones. The results show that the lifetime can be improved significantly by using network coding, and the performance gain of network coding decreases with the increase of flow asymmetry and the power control ability.

  • 125.
    Ding, Lianghui
    et al.
    Institute of Wireless Communication Technologies, Shanghai Jiao Tong University, Shanghai, China.
    Yang, Feng
    Institute of Wireless Communication Technologies, Shanghai Jiao Tong University, Shanghai, China.
    Qian, Liang
    Institute of Wireless Communication Technologies, Shanghai Jiao Tong University, Shanghai, China.
    Liu, Lu
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Wu, Ping
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Cost-delay trade off of network coding in asymmetric two-way relay networks2011Ingår i: 2011 International Symposium on Network Coding NETCOD 2011, Beijing, China, 2011Konferensbidrag (Refereegranskat)
  • 126.
    Djerf, Magnus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Power grid integration using Kalman filtering2012Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Renewable power sources with a relatively uneven or constant DC power production require synchronization methods to work with the current utility power grid. The solution to this synchronization problem has been solved with semiconductor based converters and advanced switching algorithms. To enable switching algorithms that work well with the grids amplitude, phase-shift and frequency, the current waveform has to be measured and estimated.    There are many sources of noise that will add distortion of the current waveform, making its appearance less similar to the grids. The distorted measurement affects the accuracy of the converters negatively. Therefore, using a filter algorithm to attenuate the grid noise is required.  This project uses a Kalman filter with the aim to decrease the noise and estimate the current phase shift for a three phase power-grid.  To achieve reliable and fast calculation, implementing the Kalman filter within a FPGA were done.The project contains results from both simulated MATLAB data and the FPGAs real time data. The method was able to estimate the grid within a few Hz frequency deviation and enable some noise reduction. For larger degree of harmonic distortion during steady state operation, the Kalman filter could remove more of the harmonic distortion. Limits and differences with MATLAB are discussed for the FPGA implemented Kalman filter. 

  • 127.
    Dragan, Krzysztof
    et al.
    AGH University of Science and Technology, Krakow, Polen.
    Dziendzikowski, Michal
    Air Force Institute of Technology, Warszawa, Polen.
    Uhl, Tadeusz
    AGH University of Science and Technology, Krakow, Polen.
    Stepinski, Tadeusz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Remote monitoring of fatigue cracks growth in the aircraft structure based on active piezosensor network during the full scale fatigue test2014Ingår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 588, s. 249-256Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of the major issues from a structural integrity point of view of the aircraft structure is an appropriate health monitoring technology delivery for the damage tolerant philosophy. This paper presents a development of a system for fatigue crack growth monitoring and early damage detection in the PZL 130 ORLIK TC II turbo-prop military trainer aft structure. The maintenance system of the aircraft shifts from the safe-life to the hard-time. The aircraft started Full Scale Fatigue Test (FSFT) which will continue up to 2013. In the article a built block approach for the system design, signal modeling, sensing and signal processing as well as damage detection is presented. Taking into the consideration a previous experience of AGH as well as AFIT, a network of PZT transducers was deployed in the aircraft structure hot-spots. The system components are: remote monitoring unit, signal analysis, graphical user interface, sensor self-diagnostic tools, and data classification model. Description of damage detection capabilities are delivered in the paper. In particular some issues concerning the proposed damage indices and its application to crack growth estimation models are discussed. Fishers Linear Discriminant is used as a method to obtain effective crack growth predictors and one of the self-diagnostic tools used in the system. The results of the data collected from specimen fatigue tests are delivered and cross-validation technique is used to evaluate a classification model based on the damage indices derived.

  • 128.
    Du, Rong
    et al.
    KTH Royal Inst Technol, Dept Network & Syst Engn, S-10044 Stockholm, Sweden.
    Özcelikkale, Ayca
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Fischione, Carlo
    KTH Royal Inst Technol, Dept Network & Syst Engn, S-10044 Stockholm, Sweden.
    Xiao, Ming
    KTH Royal Inst Technol, Dept Informat Sci & Engn, S-10044 Stockholm, Sweden.
    Towards Immortal Wireless Sensor Networks by Optimal Energy Beamforming and Data Routing2018Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, nr 8, s. 5338-5352Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The lifetime of a wireless sensor network (WSN) determines how long the network can be used to monitor the area of interest. Hence, it is one of the most important performance metrics for WSN. The approaches used to prolong the lifetime can be briefly divided into two categories: reducing the energy consumption, such as designing an efficient routing, and providing extra energy, such as using wireless energy transfer (WET) to charge the nodes. Contrary to the previous line of work where only one of those two aspects is considered, we investigate these two together. In particular, we consider a scenario where dedicated wireless chargers transfer energy wirelessly to sensors. The overall goal is to maximize the minimum sampling rate of the nodes while keeping the energy consumption of each node smaller than the energy it receives. This is done by properly designing the routing of the sensors and the WET strategy of the chargers. Although such a joint routing and energy beamforming problem is non-convex, we show that it can be transformed into a semi-definite optimization problem (SDP). We then prove that the strong duality of the SDP problem holds, and hence, the optimal solution of the SDP problem is attained. Accordingly, the optimal solution for the original problem is achieved by a simple transformation. We also propose a lowcomplexity approach based on pre-determined beamforming directions. Moreover, based on the alternating direction method of multipliers, the distributed implementations of the proposed approaches are studied. The simulation results illustrate the significant performance improvement achieved by the proposed methods. In particular, the proposed energy beamforming scheme significantly outperforms the schemes where one does not use energy beamforming, or one does not use optimized routing. A thorough investigation of the effect of system parameters, including the number of antennas, the number of nodes, and the number of chargers, on the system performance is provided. The promising convergence behavior of the proposed distributed approaches is illustrated.

  • 129.
    Dworakowski, Ziemowit
    et al.
    AGH University of Science and Technology, Krakow, Polen.
    Ambrozinski, Lukasz
    AGH University of Science and Technology, Krakow, Polen.
    Packo, Pawel
    AGH University of Science and Technology, Krakow, Polen.
    Dragan, Krzysztof
    AGH University of Science and Technology, Krakow, Polen.
    Stepinski, Tadeusz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Uhl, Tadeusz
    AGH University of Science and Technology, Krakow, Polen.
    Application of artificial neural networks for damage indices classification with the use of Lamb waves for the aerospace structures2014Ingår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 588, s. 12-21Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lamb waves (LW) are used for damage detection and health monitoring due to the long range propagation ability and sensitivity to structural integrity changes as well as their robustness in different applications. However, due to the dispersive character and multimode nature of LWs, analysis of the acquired ultrasonic signals is very complex. It becomes even more difficult when applied to a complex structure, for instance, an aircraft component with riveted joints and stringers characterized by difficult geometries. Therefore, numerous approaches to the evaluation of damage indices have been proposed in the literature. In this paper, comparison a number of damage indices applied to LWs testing in aircraft aluminum panels. The damage indices, known from the literature have been selected from the application point of view. Artificial neural network has been used for the classification of fatigue cracks and artificial damages induced in the specimens taken from a real aircraft structure. Article presents results of simulation, data analysis and data classification obtained using selected and dedicated neural network. The main aim of the presented research was to develop signal processing and signal classification methods for an aircraft health monitoring system. The article presents a part of the research carried out in the project named SYMOST.

  • 130.
    Döttling, Martin
    et al.
    Nokia-Siemens Networks.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Nyström, Johan
    Ericsson AB.
    Johansson, Niklas
    Ericsson AB.
    von Häfen, Jörn
    Nokia-Siemens Networks.
    Chapter 4: System Concept and Architecture2009Ingår i: Radio Technologies and Concepts for IMT-Advanced / [ed] M Döttling, A Osseiran and W Mohr, John Wiley & Sons , 2009Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 131.
    Ehrengren, Gustav
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Tredjeparts möjligheter att positionsbestämma en mobiltelefon2015Självständigt arbete på grundnivå (yrkesexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this thesis, Third parties means and methods to position a mobile phone, various

    existing technologies for mobile phone positioning are studied and how third parties

    using agreements with both webpage and smartphone app owners can get access to

    mobile phone positioning information is dealt with. The technologies include those

    based on GSM networks (2G), UMTS networks (3G), Global Navigation Satellite

    Systems (GNSS), and the Internet. The specific positioning methods that are based on

    the technologies are:

    • Cell Identity (Cell Id), Timing Advance and Time of Arrival Multilateration in GSM

    networks (2G);

    • Cell ID+RTT (Round Trip Time), Observed Time Difference of Arrival (OTDOA),

    Uplink-Time Difference of Arrival (U-TDOA) in UMTS networks (3G);

    • Positioning using Global Navigation Satellite Systems like GPS, GLONASS, Galileo,

    Beidou;

    • Positioning with the help of location fingerprinting and geolocation;

    • Positioning via IP number.

    The thesis also investigates how both IPv4 and IPv6 IP number allocation and leases is

    conducted by Swedish mobile network operators, i.e. the ones that owns and

    administrate mobile phone network infrastructure. Moreover the thesis studies how

    this information can support third parties to position mobile phones.

    The thesis further looks into how the Swedish laws the Electronic Communications

    Act (2003:286) and the Personal Data Act (1998:204) interacts and where and how

    third parties can find loopholes and create opportunities to process information in

    accordance with these Acts. After this, the thesis discusses how third parties using

    agreements with both webpage and smartphone app owners can get access to mobile

    phone positioning information. Finally the thesis concludes how third parties can

    increase their possibilities and enhance their methods on cell phone positioning.

  • 132.
    Ek, Patrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Deployment of Indoor Small-Cells for 4G mobile Broadband2013Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis presents an investigation of the impact of indoor small-cells. It is expected

    that small-cells will be able to increase the throughput and capacity for the existing

    networks. A deployment algorithm is presented with focus on offloading traffic from

    the macro layer. The performance of the deployments created with the proposed

    algorithm, is compared with a reference deployment. The different deployments are

    then simulated in a real network simulator, which performs static simulations in 3

    dimension using the theory of multiple knife-edge diffraction. The small-cells increased

    the throughput and capacity remarkably and additional gains were obtained with the

    proposed algorithm. The thesis also includes strategies for small-cell deployment.

  • 133.
    Ekman, Torbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Prediction of Mobile Radio Channels: Modeling and Design2002Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Prediction of the rapidly fading envelope of a mobile radio channel enables a number of capacity improving techniques like fast resource allocation and fast link adaptation. This thesis deals with linear prediction of the complex impulse response of a channel and unbiased quadratic prediction of the power. The design and performance of these predictors depend heavily on the correlation properties of the channel. Models for a channelwhere the multipath is caused by clusters of scatterers are studied. The correlation for the contribution from a cluster can be approximated as a damped complex sinusoid. A suitable model for the dynamics of the channel is an ARMA-process. This motivates the use of linear predictors.

    A limiting factor in the prediction are the estimation errors on the observed channels. This estimation error, caused by measurement noise and time variation, is analyzed for a block based least squares algorithm which operates on a Jakes channel model. Efficient noise reduction on the estimated channel impulse responses can be obtained with Wienersmoothers that are based on simple models for the dynamics of the channel combined with estimates of the variance of the estimation error.

    Power prediction that is based on the squared magnitude of linear prediction of the taps will be biased. Hence, a bias compensated power predictor is proposed and the optimal prediction coefficients are derived for the Rayleigh fading channel. The corresponding probability density functions for the predicted power are also derived. A performance evaluation of the prediction algorithm is carried out on measured broadband mobile radio channels. The performance is highly dependent on the variance of the estimation error and the dynamics of the individual taps.

  • 134.
    Elmelid, Axel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Automatisk nivåreglering av strålkastare2012Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    To be allowed to sell Z-suspended vehicles with dipped beam Xenon or LED lighting, Scania have to develop automatic headlight level control. This master’s thesis aims to be the foundation to that development.

    The thesis consists of several parts; a market analysis of how competitors to Scania and the general vehicle industry solve this problem; several available principles for detecting the amount of control needed; the construction of a test station for sensors, a control unit and components connected controlled by the control unit; a further theoretical and practical development of one principle – one rotational sensor connected between the chassis and the back drive axis; a state flow model programmed in Simulink that produces the control signal for the headlight leveling from the sensor input.

    Lastly the thesis gives some recommendations to the further development and implementation of automatic headlight level control on Scania vehicles.

  • 135.
    Enander, Filip
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Feasibility study of data transmission via HF link from a small UAV platform2017Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The High Frequency (HF) band, 3-30 MHz, is used when no infrastructure for long-range communications is available. New technology, such as digital signal processing enables higher data rate in the HF band, which in 2000s has resulted in increased commercial use. Reflection of radio waves in the ionosphere allows for beyond horizon communication, and are a unique property of the HF band. However, properties of the ionosphere are highly dependent of radiation from the sun, which varies with geographical location, season and time.

    The use of unmanned areal vehicle (UAV) has increased during the past years. In this project it is investigated if a HF transmitter can be placed on a small UAV platform. The objective is to get an estimation of the probabilities for successful HF transfer of real-time data from a small UAV. For example, the data could be sensor- or position data. When studying a complex problem having several parameters, such as a HF communication system, it is necessary to use the systems approach. This report illustrates the impact of size of the transmitting antenna, transmitter output power and bandwidth as well as different sources of noise and its levels.

    The results and analysis, made in this project, shows that there are feasible solutions for every tested case except at very high latitudes. Frequency planning, that is finding the less occupied channel, is almost as important as maximizing the signal to noise ratio. This project has been carried out on behalf of ÅF Technology in Solna, Sweden.

  • 136.
    Engholm, Marcus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Ultrasonic Arrays for Sensing and Beamforming of Lamb Waves2010Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Non-destructive testing (NDT) techniques are critical to ensure integrity and safety of engineered structures. Structural health monitoring (SHM) is considered as the next step in the field enabling continuous monitoring of structures.

    The first part of the thesis concerns NDT and SHM using guided waves in plates, or Lamb waves, to perform imaging of plate structures. The imaging is performed using a fixed active array setup covering a larger area of a plate. Current methods are based on conventional beamforming techniques that do not efficiently exploit the available data from the small arrays used for the purpose. In this thesis an adaptive signal processing approach based on the minimum variance distortionless response (MVDR) method is proposed to mitigate issues related to guided waves, such as dispersion and the presence of multiple propagating modes. Other benefits of the method include a significant increase in resolution. Simulation and experimental results show that the method outperforms current standard processing techniques.

    The second part of the thesis addresses transducer design issues for resonant ultrasound inspections. Resonant ultrasound methods utilize the shape and frequency of the object's natural modes of vibration to detect anomalies. The method considered in the thesis uses transducers that are acoustically coupled to the inspected structures. Changes in the transducer's electrical impedance are used to detect defects. The sensitivity that can be expected from such a setup is shown to highly depend on the transducer resonance frequency, as well as the working frequency of the instrument. Through simulations and a theoretical argumentation, optimal conditions to achieve high sensitivity are given.

    Delarbeten
    1. Direction of Arrival Estimation of Lamb Waves Using Circular Arrays
    Öppna denna publikation i ny flik eller fönster >>Direction of Arrival Estimation of Lamb Waves Using Circular Arrays
    2011 (Engelska)Ingår i: Structural Health Monitoring, ISSN 1475-9217, E-ISSN 1741-3168, Vol. 10, nr 5, s. 467-480Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

     Uniform circular arrays (UCAs) with 360 degrees azimuthal coverage are very useful for structural health monitoring (SHM) of large planar structures. Difficulties encountered when working with Lamb waves include their dispersive and multi-modal nature. In this paper three different methods for estimating the direction-of-arrival (DOA) of incoming Lamb waves are compared and verified using simulated and experimental data. The previously proposed phase-mode excitation based beamformer is compared with two high-resolution spectral estimation techniques, the Capon method and the multiple signal classification method (MUSIC). Design consideration and guidelines for UCAs are presented. To experimentally evaluate the performance of the considered DOA methods a prototype array consisting of 16 separate pinducers arranged in a ring was constructed. The array was provided with an analog multiplexer that enabled recording signals received by the individual elements using a digital oscilloscope. The array was used for the reception of ultrasonic pulses sent by broadband piezoelectric transmitters and propagating in an aluminum plate. A selection of simulation and experimental results is presented showing the superior performance of the Capon beamformer.

    Nyckelord
    array signal processing, adaptive beamforming, guided waves, dispersive waves, multi-modal waves
    Nationell ämneskategori
    Teknik och teknologier
    Forskningsämne
    Elektroteknik med inriktning mot signalbehandling
    Identifikatorer
    urn:nbn:se:uu:diva-122107 (URN)10.1177/1475921710379512 (DOI)000294287000002 ()
    Tillgänglig från: 2010-04-07 Skapad: 2010-04-06 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
    2. Adaptive Beamforming for Array Imaging of Plate Structures Using Lamb Waves
    Öppna denna publikation i ny flik eller fönster >>Adaptive Beamforming for Array Imaging of Plate Structures Using Lamb Waves
    2010 (Engelska)Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 57, nr 12, s. 2712-2724Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Lamb waves are considered a promising tool for the monitoring of plate structures. Active arrays employing beamforming techniques enables monitoring large areas of plate structures. Dispersion and multiple propagating modes are issues that need to be addressed when working with Lamb waves. Previous work has mainly focused on standard beamforming while reducing the effects of dispersion and multiple modes through frequency selectivity and transducer design. This paper presents a minimum variance distortionless response (MVDR) approach for Lamb waves using a uniform rectangular array (URA) and a single transmitter. Theoretically calculated dispersion curves are used to compensate for dispersion. The combination of the MVDR approach and the two dimensional array improves the suppression of interfering Lamb modes. The proposed approach is evaluated on simulated and experimental data and compared to the standard delay-and-sum (DAS) beamformer. It is shown that the MVDR algorithm performs better in terms of higher resolution and better sidelobe and mode suppression capabilities. Known issues of the MVDR approach, such as, signal cancellation in highly correlated environments, and poor robustness, are addressed using methods that have proven effective for the purpose in other fields of active imaging.

    Nyckelord
    imaging, array processing, adaptive beamforming, Lamb waves, guided waves, structural health monitoring, dispersive waves, multi-modal waves, mode suppression, 2d arrays
    Nationell ämneskategori
    Signalbehandling
    Forskningsämne
    Elektroteknik med inriktning mot signalbehandling
    Identifikatorer
    urn:nbn:se:uu:diva-122187 (URN)10.1109/TUFFC.2010.1745 (DOI)000285359100012 ()
    Tillgänglig från: 2010-04-07 Skapad: 2010-04-07 Senast uppdaterad: 2018-06-08Bibliografiskt granskad
    3. Imaging and Suppression of Lamb Modes Using Multiple Transmitter Adaptive Beamforming
    Öppna denna publikation i ny flik eller fönster >>Imaging and Suppression of Lamb Modes Using Multiple Transmitter Adaptive Beamforming
    (Engelska)Manuskript (preprint) (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Lamb waves have proven to be very useful for plate inspection since large areas of a plate can be covered from a fixed position. This ability makes them suitable for both inspection and structural health monitoring (SHM) applications. During the last decade research on the use of active arrays in combination with beamforming techniques have shown that a fixed array can be used to perform omni-directional monitoring over a large area of a plate structure. The dispersion and multiple ropagating modes are issues that need to be addressed when working with Lamb waves. Previous work has mainly focused on conventional, delay-and-sum (DAS) beamforming, while reducing the effects of dispersion and multiple modes through frequency selectivity and transducer design. The paper describes an adaptive beamforming technique using a minimum variance distortionless response beamforming (MVBF) approach for spatial Lamb wave filtering with multiple transmitters-multiple receivers. Dispersion is compensated for using theoretically calculated dispersion curves. Simulations are used for evaluating the performance of the technique for suppression of interfering Lamb modes, both with and without the presence of mode conversion using different array configurations. An aluminum plate with artificial defects is used for the experimental evaluation. A simple simulation model of the plate is used to compare the performance of different sizes of active arrays. The results show that the MVBF approach performs much better in terms of resolution and interfering mode suppression than the widely used standard beamformer.

    Nyckelord
    imaging, array processing, adaptive beamforming, Lamb waves, guided waves, structural health monitoring, dispersive waves, multi-modal waves, mode suppression, 2d arrays
    Nationell ämneskategori
    Signalbehandling Reglerteknik
    Identifikatorer
    urn:nbn:se:uu:diva-122188 (URN)
    Tillgänglig från: 2010-04-07 Skapad: 2010-04-07 Senast uppdaterad: 2010-04-12
    4. Narrowband ultrasonic spectroscopy for NDE of layered structures
    Öppna denna publikation i ny flik eller fönster >>Narrowband ultrasonic spectroscopy for NDE of layered structures
    2005 (Engelska)Ingår i: INSIGHT, the Journal of The British Institute of Non-Destructive Testing, Vol. 47, s. 220-224Artikel i tidskrift (Refereegranskat) Published
    Identifikatorer
    urn:nbn:se:uu:diva-75944 (URN)
    Tillgänglig från: 2006-03-10 Skapad: 2006-03-10 Senast uppdaterad: 2011-01-11
    5. Designing and evaluating transducers for narrowband ultrasonic spectroscopy
    Öppna denna publikation i ny flik eller fönster >>Designing and evaluating transducers for narrowband ultrasonic spectroscopy
    2005 (Engelska)Ingår i: 2005 IEEE Ultrasonics Symposium, 2005Konferensbidrag, Publicerat paper (Refereegranskat)
    Identifikatorer
    urn:nbn:se:uu:diva-75987 (URN)
    Tillgänglig från: 2006-03-10 Skapad: 2006-03-10 Senast uppdaterad: 2010-04-07
    6. Designing and evaluating transducers for narrowband ultrasonic spectroscopy
    Öppna denna publikation i ny flik eller fönster >>Designing and evaluating transducers for narrowband ultrasonic spectroscopy
    2007 (Engelska)Ingår i: NDT & E international, ISSN 0963-8695, E-ISSN 1879-1174, Vol. 40, nr 1, s. 49-56Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Introduction of new composite materials in aerospace applications has created a demand for an efficient NDE technique. Ultrasonic resonance inspection is especially suitable for the inspection of multilayered structures. In our previous work we have described the principle of narrowband ultrasonic spectroscopy (NBUS), where the surface of an inspected structure is scanned with a resonant transducer whose frequency response is monitored in a narrow frequency band. This paper is concerned with optimizing the NBUS setup consisting of a piezoelectric transducer coupled to a multi-layered structure. Differences in the electrical impedance of a piezoelectric transducer caused by variations of parameters of the inspected structure are estimated using an equivalent circuit model and a finite element analysis. The theoretical analysis presented in the paper results in design guidelines for NBUS transducers.

    Nyckelord
    Narrowband ultrasonic spectroscopy, Transducer design, Layered materials
    Nationell ämneskategori
    Data- och informationsvetenskap Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-13355 (URN)10.1016/j.ndteint.2006.07.006 (DOI)000242411700007 ()
    Tillgänglig från: 2008-01-22 Skapad: 2008-01-22 Senast uppdaterad: 2018-01-12Bibliografiskt granskad
  • 137.
    Engholm, Marcus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Stepinski, Tadeusz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Adaptive Beamforming for Array Imaging of Plate Structures Using Lamb Waves2010Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 57, nr 12, s. 2712-2724Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lamb waves are considered a promising tool for the monitoring of plate structures. Active arrays employing beamforming techniques enables monitoring large areas of plate structures. Dispersion and multiple propagating modes are issues that need to be addressed when working with Lamb waves. Previous work has mainly focused on standard beamforming while reducing the effects of dispersion and multiple modes through frequency selectivity and transducer design. This paper presents a minimum variance distortionless response (MVDR) approach for Lamb waves using a uniform rectangular array (URA) and a single transmitter. Theoretically calculated dispersion curves are used to compensate for dispersion. The combination of the MVDR approach and the two dimensional array improves the suppression of interfering Lamb modes. The proposed approach is evaluated on simulated and experimental data and compared to the standard delay-and-sum (DAS) beamformer. It is shown that the MVDR algorithm performs better in terms of higher resolution and better sidelobe and mode suppression capabilities. Known issues of the MVDR approach, such as, signal cancellation in highly correlated environments, and poor robustness, are addressed using methods that have proven effective for the purpose in other fields of active imaging.

  • 138.
    Engholm, Marcus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Stepinski, Tadeusz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Direction of Arrival Estimation of Lamb Waves Using Circular Arrays2011Ingår i: Structural Health Monitoring, ISSN 1475-9217, E-ISSN 1741-3168, Vol. 10, nr 5, s. 467-480Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     Uniform circular arrays (UCAs) with 360 degrees azimuthal coverage are very useful for structural health monitoring (SHM) of large planar structures. Difficulties encountered when working with Lamb waves include their dispersive and multi-modal nature. In this paper three different methods for estimating the direction-of-arrival (DOA) of incoming Lamb waves are compared and verified using simulated and experimental data. The previously proposed phase-mode excitation based beamformer is compared with two high-resolution spectral estimation techniques, the Capon method and the multiple signal classification method (MUSIC). Design consideration and guidelines for UCAs are presented. To experimentally evaluate the performance of the considered DOA methods a prototype array consisting of 16 separate pinducers arranged in a ring was constructed. The array was provided with an analog multiplexer that enabled recording signals received by the individual elements using a digital oscilloscope. The array was used for the reception of ultrasonic pulses sent by broadband piezoelectric transmitters and propagating in an aluminum plate. A selection of simulation and experimental results is presented showing the superior performance of the Capon beamformer.

  • 139.
    Engholm, Marcus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Stepinski, Tadeusz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Using 2-D Arrays for Sensing Multimodal Lamb Waves2010Ingår i: Conference on Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2010 San Diego, CA, MAR 08-11, 2010 / [ed] Shull PJ, Diaz AA, Wu AF, 2010, Vol. 7649Konferensbidrag (Refereegranskat)
    Abstract [en]

    Monitoring structural integrity of large planar structures requires normally a relatively dense network of uniformly distributed ultrasonic sensors. A 2-D ultrasonic phased array with all azimuth angle coverage would be extremely useful for the structural health monitoring (SHM) of such structures. Known techniques for estimating direction of arriving (DOA) waves cannot efficiently cope with dispersive and multimodal Lamb waves (LWs). In the paper we propose an adaptive spectral estimation technique capable of handling broadband LWs sensed by 2-D arrays, the modified Capon method. Performance of the technique is evaluated using simulated multiple-mode LWs, and verified using experimental data.

  • 140.
    Engholm, Marcus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Stepinski, Tadeusz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Olofsson, Tomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Imaging and suppression of Lamb modes using adaptive beamforming2011Ingår i: Smart materials and structures (Print), ISSN 0964-1726, E-ISSN 1361-665X, Vol. 20, nr 8, s. 1-13Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lamb waves have proven to be very useful for plate inspection because large areas of a plate can be covered from a fixed position. This capability makes them suitable for both inspection and structural health monitoring (SHM) applications. During the last decade, research on the use of active arrays in combination with beamforming techniques has shown that a fixed array can be used to perform omni-directional monitoring of a plate structure. The dispersion and multiple propagating modes are issues that need to be addressed when working with Lamb waves. Previous work has mainly focused on conventional, delay-and-sum (DAS) beamforming, while reducing the effects of multiple modes through frequency selectivity and transducer design. The paper describes an adaptive beamforming technique using a minimum variance distortionless response beamforming (MVBF) approach for spatial Lamb wave filtering with multiple-transmitter-multiple-receiver arrays. Dispersion is compensated for by using theoretically calculated dispersion curves. Simulations are used for evaluating the performance of the technique for suppression of interfering Lamb modes, both with and without the presence of mode conversion using different array configurations. A simple simulation model of the plate is used to compare the performance of different sizes of active arrays. An aluminum plate with artificial defects is used for the experimental evaluation. The results show that the MVBF approach performs a lot better in terms of resolution and suppression of interfering modes than the widely used standard beamformer.

  • 141.
    Engholm, Marcus
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Stepinski, Tadeusz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Olofsson, Tomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Imaging and Suppression of Lamb Modes Using Multiple Transmitter Adaptive BeamformingManuskript (preprint) (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Lamb waves have proven to be very useful for plate inspection since large areas of a plate can be covered from a fixed position. This ability makes them suitable for both inspection and structural health monitoring (SHM) applications. During the last decade research on the use of active arrays in combination with beamforming techniques have shown that a fixed array can be used to perform omni-directional monitoring over a large area of a plate structure. The dispersion and multiple ropagating modes are issues that need to be addressed when working with Lamb waves. Previous work has mainly focused on conventional, delay-and-sum (DAS) beamforming, while reducing the effects of dispersion and multiple modes through frequency selectivity and transducer design. The paper describes an adaptive beamforming technique using a minimum variance distortionless response beamforming (MVBF) approach for spatial Lamb wave filtering with multiple transmitters-multiple receivers. Dispersion is compensated for using theoretically calculated dispersion curves. Simulations are used for evaluating the performance of the technique for suppression of interfering Lamb modes, both with and without the presence of mode conversion using different array configurations. An aluminum plate with artificial defects is used for the experimental evaluation. A simple simulation model of the plate is used to compare the performance of different sizes of active arrays. The results show that the MVBF approach performs much better in terms of resolution and interfering mode suppression than the widely used standard beamformer.

  • 142.
    Ericsson, Lars
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Stepinski, Tadeusz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Algorithms for suppressing ultrasonic backscattering from material structure2002Ingår i: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 40, s. 733-734Artikel i tidskrift (Refereegranskat)
  • 143.
    Eriksson, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Efficient Modelling and Performance Analysis of Wideband Communication Receivers2011Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis deals with Symbol Error Rate (SER)-simulation of wireless communications and its application into throughput analysis of UltraWideband (UWB) systems. The SERs will be simulated in C++ using the Monte Carlo method and when some are calculated, the rest will be estimated using a novel extrapolation method. These SER values will be very accurate and in this thesis go as low as 1.0e-14. Reaching that low values would otherwise be impossible using the traditional Monte Carlo method, because of very large computation time. However, the novel extrapolation method, can simulate a SER-curve in less than 30 seconds. It is assumed that the noise belongs to the Generalized Gaussian distribution family and among them noise from the Normal distribution (Gaussian noise) gives the best result. It is to be noted that Gaussian noise is the most commonly used in digital communication simulations. Although the program is used for throughput analysis of UWB, the program could easily be adapted to various signals. In this thesis, throughput analysis means a plot with symbol rate vs distance. From any given symbols, the user can, with a desired minimum SER, generate an extrapolated SER-curve and see what symbol rate can be achieved by the system, while obeying power constraints of signals imposed by international laws. The developed program is, by comparing with published theoretical results, tested for QAM and PSK cases, but can easily be extended to UWB systems.

  • 144.
    Eriksson, Emil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Refinement of an emulator for the physical layer of the wireless communication of sensor networks2014Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Wireless sensor networks have applications in many different fields and environments, each with their own set of challenges to be overcome. If we can measure and compensate for the properties of the wireless environment at an early stage of the deployment, we will be able to have the sensor network operational in a smaller time frame.

    This report describes the development of an emulator for wireless sensor network of up to eight 802.15.4 complaint sensor nodes. The FPGA-based emulator has been enhanced with several new features to remove some shortcomings of the existing emulator. The emulator now provides the ability to import previously recorded data representing time varying gains of wireless links, the ability to store the signal data generated by the sensor node for later review, as well as a more intuitive user interface to make the emulator more useful as a research tool. A latency issue that previously prevented the use of any communications protocol depending of transmission acknowledgments has been studied and a solution to the issue is presented. A way of introducing external interference to the emulated system has also been investigated and provides a straightforward way of introducing interference to the system without modifying the existing hardware and software.

    Most added features have been designed to be easily modified or expanded upon.