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  • 201.
    Björnson, Emil
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Optimal Coordinated Beamforming in the Multicell Downlink with Transceiver Impairments2012In: 2012 IEEE Global Telecommunications Conference (GLOBECOM), New York: IEEE conference proceedings, 2012, p. 4775-4780Conference paper (Refereed)
    Abstract [en]

    Physical wireless transceivers suffer from a variety of impairments that distort the transmitted and received signals. Their degrading impact is particularly evident in modern systems with multiuser transmission, high transmit power, and low-cost devices, but their existence is routinely ignored in the optimization literature for multicell transmission. This paper provides a detailed analysis of coordinated beamforming in the multicell downlink. We solve two optimization problems under a transceiver impairment model and derive the structure of the optimal solutions. We show numerically that these solutions greatly reduce the impact of impairments, compared with beamforming developed for ideal transceivers. Although the so-called multiplexing gain is zero under transceiver impairments, we show that the gain of multiplexing can be large at practical SNRs.

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  • 202.
    Björnson, Emil
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Capacity Limits and Multiplexing Gains of MIMO Channels with Transceiver Impairments2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 1, p. 91-94Article in journal (Refereed)
    Abstract [en]

    The capacity of ideal MIMO channels has a high-SNR slope that equals the minimum of the number of transmit and receive antennas. This letter analyzes if this result holds when there are distortions from physical transceiver impairments. We prove analytically that such physical MIMO channels have a finite upper capacity limit, for any channel distribution and SNR. The high-SNR slope thus collapses to zero. This appears discouraging, but we prove the encouraging result that the relative capacity gain of employing MIMO is at least as large as with ideal transceivers.

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  • 203.
    Björnson, Emil
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zheng, Gan
    Interdisciplinary Centre for Security, Reliability and Trust, University of Luxembourg.
    Bengtsson, Mats
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Robust Monotonic Optimization Framework for Multicell MISO Systems2012In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, no 5, p. 2508-2523Article in journal (Refereed)
    Abstract [en]

    The performance of multiuser systems is both difficult to measure fairly and to optimize. Most resource allocation problems are nonconvex and NP-hard, even under simplifying assumptions such as perfect channel knowledge, homogeneous channel properties among users, and simple power constraints. We establish a general optimization framework that systematically solves these problems to global optimality. The proposed branch-reduce-and-bound (BRB) algorithm handles general multicell downlink systems with single-antenna users, multiantenna transmitters, arbitrary quadratic power constraints, and robustness to channel uncertainty. A robust fairness-profile optimization (RFO) problem is solved at each iteration, which is a quasiconvex problem and a novel generalization of max-min fairness. The BRB algorithm is computationally costly, but it shows better convergence than the previously proposed outer polyblock approximation algorithm. Our framework is suitable for computing benchmarks in general multicell systems with or without channel uncertainty. We illustrate this by deriving and evaluating a zero-forcing solution to the general problem.

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  • 204. Björsell, Niclas
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A Statistical Evaluation of ADC Histogram Tests with Arbitrary Stimuli Signal2005In: ADDA 2005, 2005, p. 259-264Conference paper (Refereed)
  • 205.
    Björsell, Niclas
    et al.
    Gävle Universitet.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Achievable ADC Performance by Post-Correction Utilizing Dynamic Modeling of the Integral Nonlinearity2008In: EURASIP Journal on Advances in Signal Processing, ISSN 1110-8657, p. 497187-1-497187-10Article in journal (Refereed)
    Abstract [en]

    There is a need for a universal dynamic model of analog-to-digital converters (ADC’s) aimed for postcorrection. However, it is complicated to fully describe the properties of an ADC by a single model. An alternative is to split up the ADC model in different components, where each component has unique properties. In this paper, a model based on three components is used, and a performance analysis for each component is presented. Each component can be postcorrected individually and by the method that best suits the application. The purpose of postcorrection of an ADC is to improve the performance. Hence, for each component, expressions for the potential improvement have been developed. The measures of performance are total harmonic distortion (THD) and signal to noise and distortion (SINAD), and to some extent spurious-free dynamic range (SFDR).

  • 206. Björsell, Niclas
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Analog-to-Digital Converters for High-Speed Applications2005In: GigaHz 2005, 2005, p. 151-154Conference paper (Refereed)
  • 207. Björsell, Niclas
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dynamic behavior models of analog to digital converters aimed for post-correction in wideband applications2006In: 18th IMEKO World Congress 2006: Metrology for a Sustainable Development, 2006, p. 1344-1348Conference paper (Refereed)
    Abstract [en]

    In this paper a dynamic behavior model of analog to digital converters is proposed. The model is aimed for post correction in wideband applications. The suggested post correction method is a combination of look up tables and model based correction.The model consists of three components. The first is a component represented by a Hammerstein model; that is a static nonlinearity followed by a time invariant linear filter. The second component is a nonparametric model caused by significant deviation from the characterized integral nonlinearity and the output from the Hammerstein model. The third component contains of the remaining deviation and is considered as a random model error.Results from simulations verify that the examined ADC can be described by an ordinary Hammerstein model and a static look-up table.

  • 208.
    Björsell, Niclas
    et al.
    Gävle Universitet.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Histogram Tests for Wideband Applications2008In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 57, no 1, p. 70-75Article in journal (Refereed)
    Abstract [en]

    Characterization and testing of analog-to-digital converters (ADCs) are important for many reasons. A histogram test is a common method to characterize the linearity features of an ADC. Two commonly used stimulus signals are sine waves and Gaussian noise. This paper presents a metrological comparison between Gaussian and sine-wave histogram tests for wide-band applications, that is, we evaluate the performance of the characterization of the ADC and the usability of postcorrection. A postcorrection procedure involves the characterization of the ADC nonlinearity and then the use of this information by processing the ADC output samples to remove the distortion. The results show that the Gaussian histogram test gives reasonable accuracy in measuring nonlinearities. However, it does not result in a suitable model for postcorrection in wideband applications. A single-tone sine-wave histogram will be a better basis for postcorrection. The best result can be obtained if the lookup table is trained with several single-tone sine waves in the frequency band.

  • 209. Björsell, Niclas
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On Gaussian and Sine Wave Histogram Tests for Wideband Applications2005In: Proceedings of the IEEE Instrumentation and Measurement Technology Conference, IEEE , 2005, p. 677-682Conference paper (Refereed)
    Abstract [en]

    Characterization and testing of analog-to-digital converters (ADCs) are interesting in many different aspects. Histogram test is a common method to characterize the linearity features of an ADC. Two commonly used stimuli signals are sine waves and Gaussian noise. This paper will present a metrological comparison between Gaussian and sine wave histogram tests for wideband applications; that is evaluate the performance in characterization of the ADC and the usability of post-correction. A post-correction procedure involves characterization of the ADC non-linearity and then utilization of this information by processing the ADC output samples to remove the distortion. The results indicates that even though the Gaussian histogram test seems to give reasonable accuracy to measure non-linearities it is not thereby a suitable model for post-correction. A single-tone sine wave histogram will most likely be a better solution. Best result is to train the look-up table with several single-tone sine waves in the frequency band.

  • 210.
    Björsell, Niclas
    et al.
    Gävle Universitet.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Truncated Gaussian Noise in ADC Histogram Tests2007In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 40, no 1, p. 36-42Article in journal (Refereed)
    Abstract [en]

    One method to characterize analogue to digital converters (ADCs) is to use a histogram, where Gaussian noise may be used as stimulus signal. However, a Gaussian noise signal that excites all transition levels also generates input values outside working range of the ADC. Modern signal generators can generate arbitrary signals. Hence, excluding undesired values outside the ADC full scale can minimize test sequences. Truncating the signal to the working range gives further advantages, which are explored in this paper. The Cramer-Rao lower bound and a minimum variance estimator for histogram tests with an arbitrary stimulus are derived. These are applied for truncated Gaussian noise and the result is theoretically evaluated and compared to untruncated noise. It is shown that accuracy increases for a fixed sample length and that variation over transition levels decrease.

  • 211.
    Björsell, Niclas
    et al.
    University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Medawar, Samer
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Improved estimate of parametric models for analogue to digital converters by using weighted integral nonlinearity data2010In: 17th Symposium IMEKO TC4 - Measurement of Electrical Quantities, 15th International Workshop on ADC Modelling and Testing, and 3rd Symposium IMEKO TC19 - Environmental Measurements, 2010, p. 597-600Conference paper (Refereed)
    Abstract [en]

    Error modelling has played a major role in generating post-corrections of analogue to digital converters (ADC). Benefits by using parametric models for post-correction are that they requires less memory and that they are easier to identify for arbitrary signals. However, the parameters are estimated in two steps; firstly, the integral nonlinearity (INL) is estimated and secondly, the model parameters. In this paper we propose a method to improve the performance in the second step, by utilizing information about the statistical properties of the first step.

  • 212.
    Björsell, Niclas
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Isaksson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rönnow, Daniel
    Kautz-Volterra modelling of an analogue-to-digital converter using a stepped three-tone excitation2007In: 12th IMEKO TC-4 International Workshop on ADC MODELLING AND TESTING, 2007, p. 107-112Conference paper (Refereed)
    Abstract [en]

    In many test and measurement applications, the analogue-to-digital converter (ADC) is the limiting component. Using post-correction methods can improve the performance of the component as well as the over all measurement system. In this paper an ADC is characterised by a Kautz-Volterra (KV) model, which utilises a model-based post-correction of the ADC with general properties and a reasonable number of parameters. Results that are based on measurements on a high-speed 12-bit ADC, shows good results for a third order model.

  • 213.
    Björsell, Niclas
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Isaksson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rönnow, Daniel
    Gävle Universitet.
    Kautz-Volterra modelling of analogue-to-digital converters2010In: Computer Standards & Interfaces, ISSN 0920-5489, E-ISSN 1872-7018, Vol. 32, no 3, p. 126-129Article in journal (Refereed)
    Abstract [en]

    In many test and measurement applications, the analogue-to-digital converter (ADC) is the limiting component. Using post-correction methods can improve the performance of the component as well as the overall measurement system. In this paper an ADC is characterised by a Kautz–Volterra (KV) model, which utilises a model-based post-correction of the ADC with general properties and a reasonable number of parameters. It is also shown that the inverse model has the same dynamic properties as the direct KV model. Results that are based on measurements on a high-speed 12-bit ADC show good results for a third-order model.

  • 214.
    Björsell, Niclas
    et al.
    University of Gävle, Radio center for measurement technology.
    Nader, Charles
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Multi-tone design for out-of-band characterization of nonlinear RF modules using harmonic sampling2010In: 2010 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2010 - Proceedings, IEEE, 2010, p. 620-623Conference paper (Refereed)
    Abstract [en]

    In this paper we evaluate the generation of a multi-tone set for characterizing the behavior of nonlinear radio frequency (RF) modules in its out-of-band when harmonic sampling is used as digitizer. The purpose is to provide the reader with a tool to select proper frequencies and record length for a given application and test-bed. The method is based on simulations and the use of Sidon sequences. The proposed method is applicable to sparse discrete frequency multi-tones.

  • 215. Björsell, Niklas
    et al.
    Suchánek, Petr
    Czech Tech Univ Prague.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rönnow, Daniel
    Gävle Universitet.
    Measuring Volterra Kernels of Analog To Digital Converters Using a Stepped Three-Tone Scan2008In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 57, no 4, p. 666-671Article in journal (Refereed)
    Abstract [en]

    The Volterra theory can be used to mathematically model nonlinear dynamic components such as analog-to-digital converters (ADCs). This paper describes how frequency-domain Volterra kernels of an ADC are determined from measurements. The elements of the Volterra theory are given, and practical issues are considered, such as methods for signal conditioning and finding the appropriate test signals scenario and suitable sampling frequency. The results show that, for the used pipeline ADC, the frequency dependence is significantly stronger for second-order difference products than for sum products and the linear frequency dependence was not as pronounced as that of the second-order Volterra kernel. It is suggested that the Volterra kernels have the symmetry properties of a specific box model, namely, the parallel Hammerstein system.

  • 216.
    Blasco-Serrano, Ricardo
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Coding Strategies for Compress-and-Forward Relaying2010Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The deployment of large communication networks with many autonomous devices has opened new possibilities for transmission. In particular cooperation among the different nodes has been identified as an enabling technology to satisfy the increasing demand of resources. This thesis studies different coding strategies for cooperation in relay channels in the form of compress-and-forward.

    In the first part of this thesis we consider the application of the newly introduced polar codes for compress-and-forward relaying in relay channels with orthogonal receivers. First we construct polar codes for compress-and-forward relaying based on Slepian-Wolf coding for the scenario where the capacity of the relay-destination channel is large enough. We then consider the more general picture where the capacity of the relay-destination channel is arbitrary. As for Wyner-Ziv coding, we employ nested polar codes for source and channel coding that allow for compression at any desired distortion and exploit the correlation between the observations of the source transmission to minimize the transmission rate over the relay-destination channel. This construction allows for transmission at the prominent compress-and-forward rate under some additional constraints.

    In the second part of this thesis we propose a new coding strategy for compress-and-forward relaying for half-duplex Gaussian channels. Our code construction is based on simple code concatenation for joint source-channel coding at the relay and iterative decoding at the destination. Finally, we propose several realizations of the structure at the relay and different iterative decoding algorithms in order to adapt the construction to different scenarios. Our simulation results show remarkable performance gains over other cooperation strategies such as decode-and-forward and amplify-and-forward in the scenarios where both source-relay and relay-destination links have low signal-to-noise ratios.

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  • 217.
    Blasco-Serrano, Ricardo
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On Compression and Coordination in Networks2013Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The current trends in communications suggest that the transfer of information between machines will soon predominate over the traditional human-oriented exchange. The new applications in machine-to-machine communications demand for a new type of networks that are much larger and, especially, much denser. However, there are currently many challenges that hinder an efficient deployment of such networks. In this thesis, we study some fundamental and practical aspects of two of these challenges: coordination and compression.

    The problem of coordination in a network is that of organizing the nodes to make them work together. The information-theoretic abstraction of this corresponds to generating actions with a desired empirical distribution. In this thesis, we construct polar codes for coordination for a variety of topologies. These codes combine elements of source coding, used to produce the actions, with elements of channel coding, used to obtain efficient descriptions. We show that our constructions achieve several fundamental coordination limits in a structured manner and with affordable complexity.

    Then, we consider the problem of coordinating communications to control the interference created to an external observer, measured in terms of its empirical distribution.

    To study the relationship between communication and interference, we introduce the notion of communication-interference capacity region. We obtain a complete characterization of this region for the single user scenario and a partial solution for a multiple user case. Our results reveal a fundamental tradeoff between communication, coordination, and interference in this type of networks.

    The second problem considered in this thesis, compression, involves capturing the essence of data and discarding the irrelevant aspects to obtain compact representations. This takes on a new dimension in networks, where the importance of data is no longer a local matter. In this thesis, we show that polar codes are also suitable for achieving information-theoretic bounds that involve compression in networks. More precisely, we extend our coordination constructions to realize compress-and-forward relaying with affordable complexity.

    In the last part of the thesis, we take a network approach to the problem of compressive sensing and develop methods for partial support set recovery. We use these methods to characterize the tradeoff between the measurement rate and the mean square error. Finally, we show that partial support recovery is instrumental in minimizing measurement outages when estimating random sparse signals. 

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  • 218.
    Blasco-Serrano, Ricardo
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Lv, Jing
    Dresden University of Technology.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jorswieck, Eduard
    Dresden University of Technology.
    Kliks, Adrian
    Poznan University of Technology.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Comparison of Underlay and Overlay Spectrum Sharing Strategies in MISO Cognitive Channels2012In: 2012 7th International ICST Conference on Cognitive Radio Oriented Wireless Networks and Communications (CROWNCOM), IEEE Computer Society, 2012, p. 224-229Conference paper (Refereed)
    Abstract [en]

    We consider an extension of the cognitive radio channel model in which the secondary transmitter has to obtain (“learn”) the primary message in a first phase rather than having non-causal knowledge of it. We propose an achievable rate region that combines elements of decode-and-forward relaying with coding for the pure cognitive radio channel model. Moreover, we find the choice of parameters that maximize the secondary rate under a primary rate constraint. Finally, we compare numerically the performance of our system to that of an underlay scheme that combines beamforming, rate splitting, and successive decoding. We observe that although the overlay design provides higher rates, the losses due to the first phase are quite severe. In fact, for the considered scenarios, cleverly designed underlay schemes can provide comparable performance.

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  • 219.
    Blasco-Serrano, Ricardo
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Lv, Jing
    Dresden University of Technology.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jorswieck, Eduard
    Dresden University of Technology.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Multi-antenna transmission for underlay and overlay cognitive radio with explicit message-learning phase2013In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499Article in journal (Refereed)
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  • 220.
    Blasco-Serrano, Ricardo
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Andersson, Mattias
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rathi, Vishwambhar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Polar Codes for Cooperative Relaying2012In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 60, no 11, p. 3263-3273Article in journal (Refereed)
    Abstract [en]

    We consider the symmetric discrete memoryless relay channel with orthogonal receiver components and show that polar codes are suitable for decode-and-forward and compress-and-forward relaying. In the first case we prove that polar codes are capacity achieving for the physically degraded relay channel; for stochastically degraded relay channels our construction provides an achievable rate. In the second case we construct sequences of polar codes that achieve the compress-and-forward rate by nesting polar codes for source compression into polar codes for channel coding. In both cases our constructions inherit most of the properties of polar codes. In particular, the encoding and decoding algorithms and the bound on the block error probability O(2 (N beta)) which holds for any 0 < beta < 1/2.

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  • 221.
    Blasco-Serrano, Ricardo
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Rathi, Vishwambhar
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Polar codes for compress-and-forward in binary relay channels2010In: 44th Asilomar Conference on Signals, Systems and Computers, Asilomar 2010, IEEE conference proceedings, 2010, p. 1743-1747Conference paper (Refereed)
    Abstract [en]

    We construct polar codes for binary relay channels with orthogonal receiver components. We show that polar codes achieve the cut-set bound when the channels are symmetric and the relay-destination link supports compress-and-forward relaying based on Slepian-Wolf coding. More generally, we show that a particular version of the compress-and-forward rate is achievable using polar codes for Wyner-Ziv coding. In both cases the block error probability can be bounded as O(2-Nβ) for 0 < β < 1/2 and sufficiently large block length N.

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  • 222.
    Blasco-Serrano, Ricardo
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Bandwidth efficient compress-and-forward relaying based on joint source-channel coding2011In: 2011 IEEE Wireless Communications and Networking Conference, WCNC 2011, IEEE conference proceedings, 2011, p. 1800-1804Conference paper (Refereed)
    Abstract [en]

    We propose a new code design for compress-and-forward relaying over bandlimited relay-to-destination channels. The main contribution of this paper is a code design based on joint (source-channel) coding and modulation that uses the correlation between the observations at the relay and the destination as protection against channel errors. This allows for relay nodes with reduced complexity, shifting most of the processing requirements to the destination node. Moreover, by using scalar quantizers with an entropy constraint our system provides remarkable performance in channel conditions where neither amplify-and-forward nor compress-and-forward efficiently exploit the presence of a relay node. Simulation results confirm the benefits of our proposed system.

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    fulltext
  • 223.
    Blasco-Serrano, Ricardo
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Communication and interference coordination2014In: 2014 Information Theory and Applications Workshop, ITA 2014 - Conference Proceedings, IEEE conference proceedings, 2014, p. 6804218-Conference paper (Refereed)
    Abstract [en]

    We study the problem of controlling the interference created to an external observer by a communication processes. We model the interference in terms of its type (empirical distribution), and we analyze the consequences of placing constraints on the admissible type. Considering a single interfering link, we characterize the communication-interference capacity region. Then, we look at a scenario where the interference is jointly created by two users allowed to coordinate their actions prior to transmission. In this case, the tradeoff involves communication and interference as well as coordination. We establish an achievable communication-interference region and show that efficiency is significantly improved by coordination.

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    fulltext
  • 224.
    Blasco-Serrano, Ricardo
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Compress-and-forward relaying based on symbol-wise joint source-channel coding2010In: IEEE International Conference on Communications, IEEE conference proceedings, 2010, p. 1-5Conference paper (Refereed)
    Abstract [en]

    We propose a new compress-and-forward implementation for the relay channel based on joint source-channel coding techniques. The relay performs scalar quantization of its observation in combination with a redundant index mapping. Our system utilizes the correlation between the quantized signal and the direct-link observation of the transmitted symbols as redundancy for error protection on the relay-to-destination link. In order to fully exploit this correlation the destination requires iterative decoding to recover the quantized observation sent by the relay. Once regenerated, this quantized signal is optimally combined with the direct-link observation to decode the message conveyed by the source. By quantizing the observed signal itself rather than a measure on the reliability of the information bits (e.g. a posteriori probabilities from a decoder), and by using digital communication methods on the relay-to-destination link our system yields superior performance to that of amplify-and-forward, decode-and-forward and previous implementations of compress-and-forward based on soft decoding.

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    fulltext
  • 225.
    Blasco-Serrano, Ricardo
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Polar Codes for Coordination in Cascade Networks2012In: International Zurich Seminar on Communications: February 29-March 2, 2012, Sorell Hotel Zürichberg, Zurich, Switzerland proceedings, Zürich: Eidgenössische Technische Hochschule Zürich , 2012, p. 55-58Conference paper (Refereed)
    Abstract [en]

    We consider coordination in cascade networks and construct sequences of polar codes that achieve any point in a special region of the empirical coordination capacity region. Our design combines elements of source coding to generate actions with the desired type with elements of channel coding to minimize the communication rate. Moreover, we bound the probability of malfunction of a polar code for empirical coordination. Possible generalizations and open problems are discussed.

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    fulltext
  • 226.
    Blasco-Serrano, Ricardo
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Ericsson Research.
    Zachariah, Dave
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Division of Systems and Control. Division of Systems and Control. Uppsala University.
    Sundman, Dennis
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A Measurement Rate-MSE Tradeoff for Compressive Sensing Through Partial Support Recovery2014In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 62, no 18, p. 4643-4658Article in journal (Refereed)
    Abstract [en]

    We study the fundamental relationship between two relevant quantities in compressive sensing: the measurement rate, which characterizes the asymptotic behavior of the dimensions of the measurement matrix in terms of the ratio m/ log n (m being the number of measurements and n the dimension of the sparse signal), and the mean square estimation error. First, we use an information-theoretic approach to derive sufficient conditions on the measurement rate to reliably recover a part of the support set that represents a certain fraction of the total signal power when the sparsity level is fixed. Second, we characterize the mean square error of an estimator that uses partial support set information. Using these two parts, we derive a tradeoff between the measurement rate and the mean square error. This tradeoff is achievable using a two-step approach: first support set recovery, then estimation of the active components. Finally, for both deterministic and random signals, we perform a numerical evaluation to verify the advantages of the methods based on partial support set recovery.

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    fulltext
  • 227.
    Blasco-Serrano, Ricardo
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zachariah, Dave
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sundman, Dennis
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Thobaben, Ragnar
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    An Achievable Measurement Rate-MSE Tradeoff in Compressive Sensing Through Partial Support Recovery2013In: 2013 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), New York: IEEE , 2013, p. 6426-6430Conference paper (Refereed)
    Abstract [en]

    For compressive sensing, we derive achievable performance guarantees for recovering partial support sets of sparse vectors. The guarantees are determined in terms of the fraction of signal power to be detected and the measurement rate, defined as a relation between the dimensions of the measurement matrix. Based on this result we derive a tradeoff between the measurement rate and the mean square error, and illustrate it by a numerical example.

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    fulltext
  • 228. Bloch, Anthony
    et al.
    Camarinha, Margarida
    Colombo, Leonardo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Variational obstacle avoidance problem on Riemannian manifolds2017In: 2017 IEEE 56TH ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2017, p. 145-150Conference paper (Refereed)
    Abstract [en]

    We introduce variational obstacle avoidance problems on Riemannian manifolds and derive necessary conditions for the existence of their normal extremals. The problem consists of minimizing an energy functional depending on the velocity and covariant acceleration, among a set of admissible curves, and also depending on a navigation function used to avoid an obstacle on the workspace, a Riemannian manifold. We study two different scenarios: a general one on a Riemannian manifold and a sub-Riemannian problem. By introducing a left-invariant metric on a Lie group, we also study the variational obstacle avoidance problem on a Lie group. We apply the results to the obstacle avoidance problem of a planar rigid body and a unicycle.

  • 229. Bloch, Anthony
    et al.
    Clark, William
    Colombo, Leonardo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Quasivelocities and Symmetries in Simple Hybrid Systems2017In: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, IEEE , 2017, p. 1529-1534Conference paper (Refereed)
    Abstract [en]

    This paper discusses Hamel's formalism for simple hybrid systems and explores the role of reversing symmetries in these system with a continuous-discrete combined dynamics. By extending Hamel's formalism to the class of simple hybrid systems with impulsive effects, we derive, under some conditions, the dynamics of Lagrangian hybrid systems and Hamiltonian hybrid systems. In particular, we derive Euler-Poincare and Lie-Poisson equations for systems with impulsive effects as a simple hybrid system. A reversing symmetry in the phase-space permits one to construct a time reversible hybrid Hamiltonian system. Based on the invariance of a Hamiltonian function by a reversing symmetry, we can find sufficient conditions for the existence of periodic solutions for these simple hybrid systems.

  • 230.
    Blomberg, Niclas
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rojas, Cristian R.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wahlberg, Bo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Regularization Paths for Re-Weighted Nuclear Norm Minimization2015In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 22, no 11, p. 1980-1984Article in journal (Refereed)
    Abstract [en]

    We consider a class of weighted nuclear norm optimization problems with important applications in signal processing, system identification, and model order reduction. The nuclear norm is commonly used as a convex heuristic for matrix rank constraints. Our objective is to minimize a quadratic cost subject to a nuclear norm constraint on a linear function of the decision variables, where the trade-off between the fit and the constraint is governed by a regularization parameter. The main contribution is an algorithm to determine the so-called approximate regularization path, which is the optimal solution up to a given error tolerance as a function of the regularization parameter. The advantage is that we only have to solve the optimization problem for a fixed number of values of the regularization parameter, with guaranteed error tolerance. The algorithm is exemplified on a weighted Hankel matrix model order reduction problem.

  • 231.
    Blomberg, Niclas
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rojas, Cristian
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wahlberg, Bo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Approximate Regularization Paths for Nuclear Norm Minimization using Singular Value Bounds: with Implementation and Extended Appendix2015Conference paper (Refereed)
    Abstract [en]

    The widely used nuclear norm heuristic for rank minimizationproblems introduces a regularization parameter which isdifficult to tune. We have recently proposed a method to approximatethe regularization path, i.e., the optimal solution asa function of the parameter, which requires solving the problemonly for a sparse set of points. In this paper, we extendthe algorithm to provide error bounds for the singular valuesof the approximation. We exemplify the algorithms on largescale benchmark examples in model order reduction. Here,the order of a dynamical system is reduced by means of constrainedminimization of the nuclear norm of a Hankel matrix.

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    fulltext
  • 232.
    Blomqvist, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Wahlberg, Bo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On the relation between weighted frequency-domain maximum-likelihood power spectral estimation and the prefiltered covariance extension approach2007In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 55, no 1, p. 384-389Article in journal (Refereed)
    Abstract [en]

    The aim of this correspondence is to study the connection between weighted frequency-domain maximum-likelihood power spectral estimation and the time-domain prefiltered covariance extension approach. Weighting and prefiltering are introduced to emphasize the model fit in a certain frequency range. The main result is that these two methods are very closely related for the case of autoregressive (AR) model estimation, which implies that both can be formulated as convex optimization problems. Examples illustrating the methods and the effect of prefiltering/weighting are provided.

  • 233.
    Bo, Stefano
    et al.
    KTH, School of Computer Science and Communication (CSC), Computational Biology, CB. KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Aurell, Erik
    KTH, School of Computer Science and Communication (CSC), Computational Biology, CB. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Eichhorn, Ralf
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Celani, Antonio
    Optimal stochastic transport in inhomogeneous thermal environments2013In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 103, no 1, p. 10010-Article in journal (Refereed)
    Abstract [en]

    We consider the optimization of the average entropy production in inhomogeneous temperature environments within the framework of stochastic thermodynamics. For systems modeled by Langevin equations (e.g. a colloidal particle in a heat bath) it has been recently shown that a space-dependent temperature breaks the time reversal symmetry of the fast velocity degrees of freedom resulting in an anomalous contribution to the entropy production of the overdamped dynamics. We show that optimization of entropy production is determined by an auxiliary deterministic problem formally analogous to motion on a curved manifold in a potential. The "anomalous contribution" to entropy plays the role of the potential and the inverse of the diffusion tensor is the metric. We also find that entropy production is not minimized by adiabatically slow, quasi-static protocols but there is a finite optimal duration for the transport process. As an example we discuss the case of a linearly space-dependent diffusion coefficient.

  • 234.
    Bodriagov, Oleksandr
    et al.
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Buchegger, Sonja
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Encryption for Peer-to-Peer Social Networks2011Conference paper (Refereed)
    Abstract [en]

    To address privacy concerns over online social networking services, several distributed alternatives have been proposed. These peer-to-peer (P2P) online social networks do not rely on centralized storage of user data. Instead, data can be stored not only on a computer of a profile owner but almost anywhere (friends’ computers, random peers from the social network, third-party external storage, etc.). Since the external storage is often untrusted or only semi-trusted, encryption plays a fundamental role in security of P2P social networks. Encryption, however, also adds some overhead in both the time and space domains. To be scalable, a system that relies heavily on encryption should use as efficient algorithms as possible. It also needs to provide the functionality of changing access rights at reasonable cost, and, crucially, the system should preserve privacy properties itself. That is, beyond user data confidentiality, it has to protect against information leakage about users’ access rights and traffic analysis. In this paper we explore the requirements of encryption for P2P social networks in detail and propose a list of criteria for evaluation. We then compare a set of approaches from the literature according to these criteria. We find that none of the current P2P architectures for social networks manages to achieve secure, efficient, 24/7 access control enforcement and data storage. They either rely on trust, require constantly running servers for each user, use expensive encryption, or fail to protect privacy of access information. In the search for a solution that better fulfills the criteria, we found that some broadcast encryption (BE) schemes exhibit several desirable properties. We thus propose to use BE schemes with high performance encryption/decryption regardless of the number of identities/groups for an efficient encryption-based access control in the P2P environment. We define relevant properties for the BE schemes to be used in the P2P social network scenario and describe advantages that such schemes have compared to encryption techniques used in existing P2P architectures.

  • 235.
    Bodriagov, Oleksandr
    et al.
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Buchegger, Sonja
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    P2P social networks with broadcast encryption protected privacy2012In: Privacy and Identity Management for Life, IFIP International Federation , 2012, p. 197-206Conference paper (Refereed)
    Abstract [en]

    Users of centralized online social networks (OSN) do not have full control over their data. The OSN provider can collect and mine user data and intentionally or accidentally leak it to third parties. Peer-to-peer (P2P) social networks address this problem by getting rid of the central provider and giving control to the users. However, existing proposals of P2P social networks have many drawbacks: reliance on trust, expensive anonymization or encryption techniques, etc. We propose to use broadcast encryption for data protection because of its efficiency and ability to not disclose information about who can decrypt what. We present an architecture of a P2P social network that uses a composition of public-key cryptography, broadcast encryption, and symmetric cryptography. The architecture provides confidentiality and limited integrity protection. It defines privacy-preserving profiles that allow users to quickly find data encrypted for them while preventing attackers from learning who can access which data.

  • 236. Boem, F.
    et al.
    Xu, Yuzhe
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Parisini, T.
    A distributed pareto-optimal dynamic estimation method2015In: 2015 European Control Conference, ECC 2015, Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 3673-3680Conference paper (Refereed)
    Abstract [en]

    In this paper, a novel distributed model-based prediction method is proposed using sensor networks. Each sensor communicates with the neighboring nodes for state estimation based on a consensus protocol without centralized coordination. The proposed distributed estimator consists of a consensus-filtering scheme, which uses a weighted combination of sensors information, and a model-based predictor. Both the consensus-filtering weights and the model-based prediction parameter for all the state components are jointly optimized to minimize the variance and bias of the prediction error in a Pareto framework. It is assumed that the weights of the consensus-filtering phase are unequal for the different state components, unlike consensus-based approaches from literature. The state, the measurements, and the noise components are assumed to be individually correlated, but no probability distribution knowledge is assumed for the noise variables. The optimal weights are derived and it is established that the consensus-filtering weights and the model-based prediction parameters cannot be designed separately in an optimal way. The asymptotic convergence of the mean of the prediction error is demonstrated. Simulation results show the performance of the proposed method, obtaining better results than distributed Kalman filtering. 

  • 237.
    Boem, Francesca
    et al.
    Department of Industrial and Information Engineering, University of Trieste.
    Xu, Yuzhe
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Parisini, Thomas
    Department of Industrial and Information Engineering, University of Trieste.
    A distributed estimation method for sensor networks based on Pareto optimization2012In: Decision and Control (CDC), 2012 IEEE 51st Annual Conference on, IEEE , 2012, p. 775-781Conference paper (Refereed)
    Abstract [en]

    A novel distributed estimation method for sensor networks is proposed. The goal is to track a time-varying signal that is jointly measured by a network of sensor nodes despite the presence of noise: each node computes its local estimate as a weighted sum of its own and its neighbors' measurements and estimates and updates its weights to minimize both the variance and the mean of the estimation error by means of a suitable Pareto optimization problem. The estimator does not rely on a central coordination: both parameter optimization and estimation are distributed across the nodes. The performance of the distributed estimator is investigated in terms of estimation bias and estimation error. Moreover, an upper bound of the bias is provided. The effectiveness of the proposed estimator is illustrated via computer simulations and the performances are compared with other distributed schemes previously proposed in the literature. The results show that the estimation quality is comparable to that of one of the best existing distributed estimation algorithms, guaranteeing lower computational cost and time.

  • 238.
    Boem, Francesca
    et al.
    Department of Industrial and Information Engineering, University of Trieste.
    Xu, Yuzhe
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Parisini, Thomas
    Department of Industrial and Information Engineering, University of Trieste.
    Distributed Fault Detection using Sensor Networks and Pareto Estimation2013In: 2013 European Control Conference, ECC 2013, IEEE conference proceedings, 2013, p. 932-937Conference paper (Refereed)
    Abstract [en]

    In this paper, a preliminary novel distributed fault detection architecture for dynamic systems using sensor networks and a distributed estimation method based on Pareto optimization is proposed. The goal is to monitor large-scale or distributed systems by using a sensor network where each node acts as a local estimation agent without centralized coordination. Probabilistic detection thresholds related to a given rate of false alarms are derived in several different scenarios as far as the measurement pattern and the nominal dynamics is concerned. Preliminary simulation results show the effectiveness of the proposed fault detection methodology.

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    yuzhe2013
  • 239. Bombois, Xavier
    et al.
    den Dekker, Arjan J.
    Rojas, Cristian R.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Van den Hof, Paul M. J.
    Optimal experiment design for hypothesis testing applied to functional magnetic resonance imaging2011In: Proceedings of the 18th IFAC World Congress, 2011, p. 9953-9958Conference paper (Refereed)
    Abstract [en]

    Hypothesis testing is a classical methodology of making decisions using experimental data. In hypothesis testing one seeks to discover evidence that either accepts or rejects a given null hypothesis H0. The alternative hypothesis H1 is the hypothesis that is accepted when H0 is rejected. In hypothesis testing, the probability of deciding H1 when in fact H0 is true is known as the false alarm rate, whereas the probability of deciding H1when in fact H1is true is known as the detection rate (or power) of the test. It is not possible to optimize both rates simultaneously. In this paper, we consider the problem of determining the data to be used for hypothesis testing that maximize the detection rate for a given false alarm rate. We consider in particular a hypothesis test which is relevant in functional magnetic resonance imaging (fMRI).

  • 240.
    Bombois, Xavier
    et al.
    TU Delft.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Optimal input design for robust H2 deconvolution filtering2009In: 15th IFAC Symposium on System Identification, SYSID 2009, Elsevier BV , 2009, Vol. 42, no PART 1, p. 934-939Conference paper (Refereed)
    Abstract [en]

    Deconvolution filtering where the system and noise dynamics are obtained by parametric system identification is considered. Consistent with standard identification methods, ellipsoidal uncertainty in the estimated parameters is considered. Three problems are considered: 1) Computation of the worst case H2 performance of a given deconvolution filter in this uncertainty set. 2) Design of a filter which minimizes the worst case H2 performance in this uncertainty set. 3) Input design for the identification experiment, subject to a limited input power budget, such that the filter in 2) gives the smallest possible worst-case H2 performance. It is shown that there are convex relaxations of the optimization problems corresponding to 1) and 2) while the third problem can be treated via iterating between two convex optimization problems.

  • 241.
    Bombois, Xavier
    et al.
    TU Delft.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Scorletti, Gerard
    Ecole Centrale de Lyon.
    Identification for robust H-2 deconvolution filtering2010In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 46, no 3, p. 577-584Article in journal (Refereed)
    Abstract [en]

    This paper addresses robust deconvolution filtering when the system and noise dynamics are obtained by parametric system identification. Consistent with standard identification methods, the uncertainty in the estimated parameters is represented by an ellipsoidal uncertainty region. Three problems are considered: (1) computation of the worst case H-2 performance of a given deconvolution filter in this uncertainty set; (2) design of a filter which minimizes the worst case H-2 performance in this uncertainty set; (3) input design for the identification experiment, subject to a limited input power budget, such that the filter in (2) gives the smallest possible worst case H-2 performance. It is shown that there are convex relaxations of the optimization problems corresponding to (1) and (2) while the third problem can be treated via iterating between two convex optimization problems.

  • 242. Bonetto, Riccardo
    et al.
    Rossi, Michele
    Tomasin, Stefano
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Joint Optimal Pricing and Electrical Efficiency Enforcement for Rational Agents in Microgrids2017In: IEEE Access, E-ISSN 2169-3536, Vol. 5, p. 19782-19798Article in journal (Refereed)
    Abstract [en]

    In electrical distribution grids, the constantly increasing number of power generation devices based on renewables demands a transition from a centralized to a distributed generation paradigm. In fact, power injection from distributed energy resources (DERs) can be selectively controlled to achieve other objectives beyond supporting loads, such as the minimization of the power losses along the distribution lines and the subsequent increase of the grid hosting capacity. However, these technical achievements are only possible if alongside electrical optimization schemes, a suitable market model is set up to promote cooperation from the end users. In contrast with the existing literature, where energy trading and electrical optimization of the grid are often treated separately, or the trading strategy is tailored to a specific electrical optimization objective, in this paper, we consider their joint optimization. We also allow for a modular approach, where the market model can support any smart grid optimization goal. Specifically, we present a multi-objective optimization problem accounting for energy trading, where: 1) DERs try to maximize their profit, resulting from selling their surplus energy; 2) the loads try to minimize their expense; and 3) the main power supplier aims at maximizing the electrical grid efficiency through a suitable discount policy. This optimization problem is proved to be non-convex, and an equivalent convex formulation is derived. Centralized solutions are discussed and a procedure to distribute the solution is proposed. Numerical results to demonstrate the effectiveness of the so obtained optimal policies are finally presented, showing the proposed model results in economic bene fits for all the users (generators and loads) and in an increased electrical efficiency for the grid.

  • 243. Bonivento, A.
    et al.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sangiovanni-Vincentelli, A.
    SERAN: a protocol for clustered WSNs in industrial control and automation2009In: 2009 6th IEEE Annual Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks Workshops, 2009, Vol. SECON Workshops 2009, p. 236-238Conference paper (Refereed)
    Abstract [en]

    A system level design methodology for clustered wireless sensor networks based on a semi-random communication protocol called SERAN is presented. The protocol is grounded on a mathematical model that allows to optimize the protocol parameters, and a network initialization and maintenance procedure. SERAN is a two-layer (routing and MAC) protocol. At both layers, SERAN combines a randomized and a deterministic approach. While the randomized component provides robustness over unreliable channels, the deterministic component avoids an explosion of packet collisions and allows our protocol to scale with network size. The combined result is a high reliability and major energy savings when dense clusters are used. Our solution is based on a mathematical model that characterizes performance accurately without resorting to extensive simulations. Thanks to this model, the user needs only to specify the application requirements in terms of end-to-end packet delay and packet loss probability, select the intended hardware platform, and the protocol parameters are set automatically to satisfy latency requirements and optimize for energy consumption.

  • 244. Borges de Sousa, J.
    et al.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Speranzon, A.
    Silva, J.
    A control architecture for multiple submarines in coordinated search missions2005Conference paper (Refereed)
    Abstract [en]

    A control architecture for executing multi-vehicle search algorithms is presented. The proposed hierarchical structure consists of three control layers: maneuver controllers, vehicle supervisors and team controllers. The system model is described as a dynamic network of hybrid automata in the programming language Shift and allows reasoning about specification and dynamical properties in a formal setting. The particular search problem that is studied is that of finding the minimum of a scalar field using a team of autonomous submarines. As an illustration, a coordination scheme based on the Nelder-Mead simplex optimization algorithm is presented and illustrated through simulations.

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    multirobot_iwur05
  • 245.
    Boskos, Dimitris
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Abstractions of Varying Decentralization Degree for Coupled Multi-Agent Systems2016In: 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 81-86, article id 7798250Conference paper (Refereed)
    Abstract [en]

    In this paper, we aim at the development of a decentralized abstraction framework for multi-agent systems under coupled constraints, with the possibility for a varying degree of decentralization. The methodology is based on the analysis employed in our recent work, where decentralized abstractions based exclusively on the information of each agent's neighbors were derived. In the first part of this paper, we define the notion each agent's m-neighbor set, which constitutes a measure for the employed degree of decentralization. Then, sufficient conditions are provided on the space and time discretization that provides the abstract system's model, which guarantee the extraction of a meaningful transition system with quantifiable transition possibilities.

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    fulltext
  • 246.
    Boskos, Dimitris
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Online Abstractions for Interconnected Multi-Agent Control Systems2017Conference paper (Refereed)
    Abstract [en]

    In this paper, we aim at the development of an online abstraction framework for multi-agent systems under coupled constraints. The motion capabilities of each agent are abstracted through a finite state transition system in order to capture reachability properties of the coupled multi-agent system over a finite time horizon in a decentralized manner. In the first part of this work, we define online abstractions by discretizing an overapproximation of the agents' reachable sets over the horizon. Then, sufficient conditions relating the discretization and the agents' dynamics are provided, in order to quantify the agents' transition possibilities.

    Download full text (pdf)
    fulltext
  • 247.
    Boskos, Dmitris
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Decentralized abstractions for feedback interconnected multi-agent systems2016In: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2016, p. 282-287Conference paper (Refereed)
    Abstract [en]

    The purpose of this paper is to define abstractions for multi-agent systems under coupled constraints. In the proposed decentralized framework, we specify a finite or countable transition system for each agent which only takes into account the discrete positions of its neighbors. The dynamics of the considered systems consist of two components. An appropriate feedback law which guarantees that certain performance requirements (e.g., connectivity) are preserved and induces the coupled constraints, and additional free inputs which are exploited for the accomplishment of high level tasks. In this work we provide sufficient conditions on the space and time discretization for the abstraction of the system's behaviour which ensure that we can extract a well posed and hence meaningful transition system.

    Download full text (pdf)
    fulltext
  • 248.
    Boskos, Dmitris
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Robust connectivity analysis for multi-agent systems2016In: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2016, p. 6767-6772Conference paper (Refereed)
    Abstract [en]

    In this paper we provide a decentralized robust control approach, which guarantees that connectivity of a multi-agent network is maintained when certain bounded input terms are added to the control strategy. Our main motivation for this framework is to determine abstractions for multi-agent systems under coupled constraints which are further exploited for the synthesis of high level plans.

    Download full text (pdf)
    fulltext
  • 249. Bottegal, G.
    et al.
    Risuleo, Riccardo Sven
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zamani, M.
    Ninness, B.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On maximum likelihood identification of errors-in-variables models2017In: IFAC-PapersOnLine, E-ISSN 2405-8963, Vol. 50, no 1, p. 2824-2829Article in journal (Refereed)
    Abstract [en]

    In this paper, we revisit maximum likelihood methods for identification of errors-in-variables systems. We assume that the system admits a parametric description, and that the input is a stochastic ARMA process. The cost function associated with the maximum likelihood criterion is minimized by introducing a new iterative solution scheme based on the expectation-maximization method, which proves fast and easily implementable. Numerical simulations show the effectiveness of the proposed method.

  • 250.
    Bottegal, Giulio
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Aravkin, Aleksandr Y.
    Hjalmarsson, Hakan
    Pillonetto, Gianluigi
    Robust EM kernel-based methods for linear system identification2016In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 67, p. 114-126Article in journal (Refereed)
    Abstract [en]

    Recent developments in system identification have brought attention to regularized kernel-based methods. This type of approach has been proven to compare favorably with classic parametric methods. However, current formulations are not robust with respect to outliers. In this paper, we introduce a novel method to robustify kernel-based system identification methods. To this end, we model the output measurement noise using random variables with heavy-tailed probability density functions (pdfs), focusing on the Laplacian and the Student's t distributions. Exploiting the representation of these pdfs as scale mixtures of Gaussians, we cast our system identification problem into a Gaussian process regression framework, which requires estimating a number of hyperparameters of the data size order. To overcome this difficulty, we design a new maximum a posteriori (MAP) estimator of the hyperparameters, and solve the related optimization problem with a novel iterative scheme based on the Expectation-Maximization (EM) method. In the presence of outliers, tests on simulated data and on a real system show a substantial performance improvement compared to currently used kernel-based methods for linear system identification. (C) 2016 Elsevier Ltd. All rights reserved.

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