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Wahlström, J., Skog, I., Händel, P., Bradley, B., Madden, S. & Balakrishnan, H. (2020). Smartphone Placement Within Vehicles. IEEE transactions on intelligent transportation systems (Print), 21(2), 669-679
Open this publication in new window or tab >>Smartphone Placement Within Vehicles
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2020 (English)In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 21, no 2, p. 669-679Article in journal (Refereed) Published
Abstract [en]

Smartphone-based driver monitoring is quickly gaining ground as a feasible alternative to competing in-vehicle and aftermarket solutions. Currently the main challenges for data analysts studying smartphone-based driving data stem from the mobility of the smartphone. In this paper, we use kernel-based k-means clustering to infer the placement of smartphones within vehicles. The trip segments are mapped into fifteen different placement clusters. As a part of the presented framework, we discuss practical considerations concerning e.g., trip segmentation, cluster initialization, and parameter selection. The proposed method is evaluated on more than 10 000 kilometers of driving data collected from approximately 200 drivers. To validate the interpretation of the clusters, we compare the data associated with different clusters and relate the results to real-world knowledge of driving behavior. The clusters associated with the label "Held by hand" are shown to display high gyroscope variances, low maximum speeds, low correlations between the measurements from smartphone-embedded and vehicle-fixed accelerometers, and short segment durations.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020
Keywords
Vehicles, Accelerometers, Telematics, Gyroscopes, Insurance, Sensor phenomena and characterization, inertial sensors, smartphones, kernel-based k-means clustering
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-271302 (URN)10.1109/TITS.2019.2896708 (DOI)000515647600017 ()2-s2.0-85079345671 (Scopus ID)
Note

QC 20200331

Available from: 2020-03-31 Created: 2020-03-31 Last updated: 2020-03-31Bibliographically approved
Alizadeh, M., Händel, P. & Rönnow, D. (2019). Behavioral modeling and digital pre-distortion techniques for RF PAs in a 3 x 3 MIMO system. International journal of microwave and wireless technologies, 11(10), 989-999
Open this publication in new window or tab >>Behavioral modeling and digital pre-distortion techniques for RF PAs in a 3 x 3 MIMO system
2019 (English)In: International journal of microwave and wireless technologies, ISSN 1759-0795, E-ISSN 1759-0787, Vol. 11, no 10, p. 989-999Article in journal (Refereed) Published
Abstract [en]

Modern telecommunications are moving towards (massive) multi-input multi-output (MIMO) systems in 5th generation (5G) technology, increasing the dimensionality of the systems dramatically. In this paper, the impairments of radio frequency (RF) power amplifiers (PAs) in a 3 x 3 MIMO system are compensated in both the time and the frequency domains. A three-dimensional (3D) time-domain memory polynomial-type model is proposed as an extension of conventional 2D models. Furthermore, a 3D frequency-domain technique is formulated based on the proposed time-domain model to reduce the dimensionality of the model, while preserving the performance in terms of model errors. In the 3D frequency-domain technique, the bandwidth of the system is split into several narrow sub-bands, and the parameters of the model are estimated for each sub-band. This approach requires less computational complexity, and also the procedure of the parameters estimation for each sub-band can be implemented independently. The device-under-test consists of three RF PAs including input and output cross-talk channels. The proposed techniques are evaluated in both behavioral modeling and digital pre-distortion (DPD) perspectives. The experimental results show that the proposed DPD technique can compensate the errors of non-linearity and memory effects in the both time and frequency domains.

Place, publisher, year, edition, pages
Cambridge University Press, 2019
Keywords
Radio frequency power amplifier, non-linearity, memory effects, multiple-input multiple-output (MIMO), behavioral modelling, digital pre-distortion
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-266173 (URN)10.1017/S1759078719000862 (DOI)000500870900001 ()2-s2.0-85067662944 (Scopus ID)
Note

QC 20200113

Available from: 2020-01-13 Created: 2020-01-13 Last updated: 2020-01-13Bibliographically approved
Händel, P. & Wahlström, J. (2019). Digital contraceptives based on basal body temperature measurements. Biomedical Signal Processing and Control, 52, 141-151
Open this publication in new window or tab >>Digital contraceptives based on basal body temperature measurements
2019 (English)In: Biomedical Signal Processing and Control, ISSN 1746-8094, E-ISSN 1746-8108, Vol. 52, p. 141-151Article in journal (Refereed) Published
Abstract [en]

Digital contraceptives and fertility awareness products are currently offered as convenient smartphone applications. The first legitimate contraceptive smartphone app was recently introduced on the European market, with the digital processing based on measurements of the female user's basal body temperature (BBT). According to recent pilot market data, at some Swedish hospitals, up to 5–10% of women seeking abortion had become involuntarily pregnant while using the product. This fact motivates a review of the research on fertility determination based on BBT measurements. This paper provides the first estimation theoretical review and evaluation of BBT-based ovulation detection. From an engineering perspective, it is concluded that the available detection algorithms have similar performance and that the performance is rather insensitive to a one- or two-decimal resolution of the employed thermometer. Further, we highlight that when using the output from proposed ovulation detection algorithms, one must consider not only the uncertainty in the relative time difference of the detected temperature shift and the ovulation, but also the statistical uncertainty of the detection methods due to noisy measurements.

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Basal body temperature method, Digital contraceptives, Fertility detection, Medical information systems, Ovulation detection, Commerce, mHealth, Physiology, Signal detection, Smartphones, Temperature measurement, Basal body temperatures (BBT), Body temperature, Body temperature measurements, Detection algorithm, Engineering perspective, Smart-phone applications, Statistical uncertainty, Uncertainty analysis
National Category
Computer and Information Sciences
Identifiers
urn:nbn:se:kth:diva-252467 (URN)10.1016/j.bspc.2019.04.019 (DOI)000473381100015 ()2-s2.0-85064463556 (Scopus ID)
Note

QC 20190715

Available from: 2019-07-15 Created: 2019-07-15 Last updated: 2019-07-29Bibliographically approved
Händel, P. & Rönnow, D. (2019). Modeling Mixer and Power Amplifier Impairments. IEEE Microwave and Wireless Components Letters, 29(7), 441-443
Open this publication in new window or tab >>Modeling Mixer and Power Amplifier Impairments
2019 (English)In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 29, no 7, p. 441-443Article in journal (Refereed) Published
Abstract [en]

Combating the effects of mixer and power amplifier (PA) imperfections on transmitter performance is crucial for the design of wireless systems. PA compression and in-phase/quadrature imbalance are analyzed for a single-input-single-output transmitter model. The influence of the imperfection on the normalized mean squared error (NMSE) of the transmitter is studied using an analytical framework that relies on the classic Bussgang theory. The study concludes with a closed-form expression for the NMSE that provides insights into the behavior of the transmitter.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
Dirty radio, input backoff, orthogonal frequency division multiplexing (OFDM), power amplifier (PA)
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-255393 (URN)10.1109/LMWC.2019.2915647 (DOI)000474589400001 ()2-s2.0-85068688857 (Scopus ID)
Note

QC 20190729

Available from: 2019-07-29 Created: 2019-07-29 Last updated: 2019-07-29Bibliographically approved
Ronnow, D. & Händel, P. (2019). Nonlinear Distortion Noise and Linear Attenuation in MIMO Systems-Theory and Application to Multiband Transmitters. IEEE Transactions on Signal Processing, 67(20), 5203-5212
Open this publication in new window or tab >>Nonlinear Distortion Noise and Linear Attenuation in MIMO Systems-Theory and Application to Multiband Transmitters
2019 (English)In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 67, no 20, p. 5203-5212Article in journal (Refereed) Published
Abstract [en]

Nonlinear static multiple-input multiple-output (MIMO) systems are analyzed. The matrix formulation of Bussgang's theorem for complex Gaussian signals is rederived and put in the context of the multivariate cumulant series expansion. The attenuation matrix is a function of the input signals' covariance and the covariance of the input and output signals. The covariance of the distortion noise is in addition a function of the output signal's covariance. The effect of the observation bandwidth is discussed. Models of concurrent multiband transmitters are analyzed. For a transmitter with dual non-contiguous hands expressions for the normalized mean square error (NMSE) vs input signal power are derived for uncorrelated, partially correlated, and correlated input signals. A transmitter with arbitrary number of non-contiguous hands is analysed for correlated and uncorrelated signals. In an example, the NMSE is higher when the input signals are correlated than when they are uncorrelated for the same input signal power and it increases with the number of frequency hands. A concurrent dual band amplifier with contiguous bands is analyzed; in this case the NMSE depends on the bandwidth of the aggregated signal.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Bussgang theory, carrier aggregation, concurrent dual band, MIMO, multiband transmitter, nonlinear distortion
National Category
Signal Processing
Identifiers
urn:nbn:se:kth:diva-261290 (URN)10.1109/TSP.2019.2935896 (DOI)000485741500001 ()2-s2.0-85077734457 (Scopus ID)
Note

QC 20191009

Available from: 2019-10-09 Created: 2019-10-09 Last updated: 2020-03-09Bibliographically approved
Venkitaraman, A., Chatterjee, S. & Händel, P. (2019). On Hilbert transform, analytic signal, and modulation analysis for signals over graphs. Signal Processing, 156, 106-115
Open this publication in new window or tab >>On Hilbert transform, analytic signal, and modulation analysis for signals over graphs
2019 (English)In: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 156, p. 106-115Article in journal (Refereed) Published
Abstract [en]

We propose Hilbert transform and analytic signal construction for signals over graphs. This is motivated by the popularity of Hilbert transform, analytic signal, and modulation analysis in conventional signal processing, and the observation that complementary insight is often obtained by viewing conventional signals in the graph setting. Our definitions of Hilbert transform and analytic signal use a conjugate symmetry-like property exhibited by the graph Fourier transform (GFT), resulting in a 'one-sided' spectrum for the graph analytic signal. The resulting graph Hilbert transform is shown to possess many interesting mathematical properties and also exhibit the ability to highlight anomalies/discontinuities in the graph signal and the nodes across which signal discontinuities occur. Using the graph analytic signal, we further define amplitude, phase, and frequency modulations for a graph signal. We illustrate the proposed concepts by showing applications to synthesized and real-world signals. For example, we show that the graph Hilbert transform can indicate presence of anomalies and that graph analytic signal, and associated amplitude and frequency modulations reveal complementary information in speech signals.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Graph signal processing, Analytic signal, Hilbert transform, Demodulation, Anomaly detection
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-240988 (URN)10.1016/j.sigpro.2018.10.016 (DOI)000453494200011 ()2-s2.0-85056192636 (Scopus ID)
Note

QC 20190110

Available from: 2019-01-10 Created: 2019-01-10 Last updated: 2019-06-11Bibliographically approved
Venkitaraman, A., Chatterjee, S. & Händel, P. (2019). Predicting Graph Signals Using Kernel Regression Where the Input Signal is Agnostic to a Graph. IEEE TRANSACTIONS ON SIGNAL AND INFORMATION PROCESSING OVER NETWORKS, 5(4), 698-710
Open this publication in new window or tab >>Predicting Graph Signals Using Kernel Regression Where the Input Signal is Agnostic to a Graph
2019 (English)In: IEEE TRANSACTIONS ON SIGNAL AND INFORMATION PROCESSING OVER NETWORKS, ISSN 2373-776X, Vol. 5, no 4, p. 698-710Article in journal (Refereed) Published
Abstract [en]

We propose a kernel regression method to predict a target signal lying over a graph when an input observation is given. The input and the output could be two different physical quantities. In particular, the input may not be a graph signal at all or it could be agnostic to an underlying graph. We use a training dataset to learn the proposed regression model by formulating it as a convex optimization problem, where we use a graph-Laplacian based regularization to enforce that the predicted target is a graph signal. Once the model is learnt, it can be directly used on a large number of test data points one-by-one independently to predict the corresponding targets. Our approach employs kernels between the various input observations, and as a result the kernels are not restricted to be functions of the graph adjacency/Laplacian matrix. We show that the proposed kernel regression exhibits a smoothing effect, while simultaneously achieving noise-reduction and graph-smoothness. We then extend our method to the case when the underlying graph may not be known apriori, by simultaneously learning an underlying graph and the regression coefficients. Using extensive experiments, we show that our method provides a good prediction performance in adverse conditions, particularly when the training data is limited in size and is noisy. In graph signal reconstruction experiments, our method is shown to provide a good performance even for a highly under-determined subsampling.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Kernel, Signal processing, Mathematical model, Machine learning, Training, Predictive models, Image reconstruction, Linear model, regression, kernels, graph signal processing, graph-Laplacian
National Category
Computer Sciences
Identifiers
urn:nbn:se:kth:diva-264148 (URN)10.1109/TSIPN.2019.2936358 (DOI)000492993200007 ()2-s2.0-85071685668 (Scopus ID)
Note

QC 20191209

Available from: 2019-12-09 Created: 2019-12-09 Last updated: 2020-01-07Bibliographically approved
Pettersson, D., Lillieskold, J., Händel, P. & Agerman, J. (2019). Usage-based auto insurance on the swedish market: A case study. In: PICMET 2019 - Portland International Conference on Management of Engineering and Technology: Technology Management in the World of Intelligent Systems, Proceedings. Paper presented at 2019 Portland International Conference on Management of Engineering and Technology, PICMET 2019, 25 August 2019 through 29 August 2019. Institute of Electrical and Electronics Engineers Inc.
Open this publication in new window or tab >>Usage-based auto insurance on the swedish market: A case study
2019 (English)In: PICMET 2019 - Portland International Conference on Management of Engineering and Technology: Technology Management in the World of Intelligent Systems, Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2019Conference paper, Published paper (Refereed)
Abstract [en]

The Swedish consumer market for auto insurance is in a process of transformation from traditional insurance to usage-based insurance (UBI) based on telematics. The Swedish market can be characterized as having a high level of diffusion and use of digital technologies, yet while auto UBI is well established on several markets internationally it has been struggling on the Swedish. An exploratory case study has been performed covering actors in the Swedish eco system around UBI: incumbent insurance companies, challengers, and technology providers. Interviews have been carried out with key employees and decision makers to understand which opportunities and challenges they perceive in areas ranging from technology to market and how these influence decisions to engage or not to engage in such innovations. The results indicate among other things that national characteristics influence the establishment of auto UBI; the expected technological development creates a window of opportunity preventing incumbents from engaging; the slowly increasing market penetration by UBI offered by challengers will eventually force incumbents to react; although sales of a UBI service is generally not considered profitable for an incumbent they consider or apply different strategies for self-disruption.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2019
Keywords
Decision making, Insurance, Intelligent systems, Consumer market, Digital technologies, Exploratory case studies, Insurance companies, Market penetration, National characteristics, Technological development, Technology providers, Commerce
National Category
Economics and Business
Identifiers
urn:nbn:se:kth:diva-268554 (URN)10.23919/PICMET.2019.8893870 (DOI)2-s2.0-85075638079 (Scopus ID)9781890843403 (ISBN)
Conference
2019 Portland International Conference on Management of Engineering and Technology, PICMET 2019, 25 August 2019 through 29 August 2019
Note

QC 20200325

Available from: 2020-03-25 Created: 2020-03-25 Last updated: 2020-03-25Bibliographically approved
Wahlström, J., Jaldén, J., Skog, I. & Händel, P. (2018). Alternative em Algorithms for Nonlinear State-Space Models. In: 21st International Conference on Information Fusion, FUSION 2018: . Paper presented at 21st International Conference on Information Fusion, FUSION 2018, 10-13 July 2018, Cambridge, ENGLAND (pp. 1260-1267). Institute of Electrical and Electronics Engineers Inc.
Open this publication in new window or tab >>Alternative em Algorithms for Nonlinear State-Space Models
2018 (English)In: 21st International Conference on Information Fusion, FUSION 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 1260-1267Conference paper, Published paper (Refereed)
Abstract [en]

The expectation-maximization algorithm is a commonly employed tool for system identification. However, for a large set of state-space models, the maximization step cannot be solved analytically. In these situations, a natural remedy is to make use of the expectation-maximization gradient algorithm, i.e., to replace the maximization step by a single iteration of Newton's method. We propose alternative expectation-maximization algorithms that replace the maximization step with a single iteration of some other well-known optimization method. These algorithms parallel the expectation-maximization gradient algorithm while relaxing the assumption of a concave objective function. The benefit of the proposed expectation-maximization algorithms is demonstrated with examples based on standard observation models in tracking and localization. 

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2018
Keywords
Expectation-maximization, Levenberg-Marquardt, system identification, the Gauss-Newton method, trust region, Identification (control systems), Image segmentation, Information fusion, Newton-Raphson method, Positron emission tomography, Religious buildings, Signal receivers, State space methods, Concave objective functions, Expectation - maximizations, Expectation-maximization algorithms, Gauss-Newton methods, Nonlinear state space models, State - space models, Maximum principle
National Category
Computer and Information Sciences
Identifiers
urn:nbn:se:kth:diva-236699 (URN)10.23919/ICIF.2018.8455234 (DOI)000495071900172 ()2-s2.0-85054096276 (Scopus ID)9780996452762 (ISBN)
Conference
21st International Conference on Information Fusion, FUSION 2018, 10-13 July 2018, Cambridge, ENGLAND
Funder
Swedish Foundation for Strategic Research
Note

QC 20181112

Available from: 2018-11-12 Created: 2018-11-12 Last updated: 2020-01-07Bibliographically approved
Alizadeh, M., Händel, P. & Rönnow, D. (2018). Basis Function Decomposition Approach in Piece-Wise Modeling for RF Power Amplifiers. In: 6th Telecommunications forum TELFOR 2018: . Paper presented at 26th Telecommunications forum TELFOR 2018, Serbia, Belgrade, November 20-21, 2018.. Belgrade, Serbia
Open this publication in new window or tab >>Basis Function Decomposition Approach in Piece-Wise Modeling for RF Power Amplifiers
2018 (English)In: 6th Telecommunications forum TELFOR 2018, Belgrade, Serbia, 2018Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, a new approach is proposed to decompose the basis functions in a piece-wise modeling technique for nonlinear radio frequency (RF) power amplifiers. The proposed technique treats the discontinuity problem of the model output at the joint points between different operating points, whereas preserves the linear and nonlinear properties of the original model within each region. Experimental results show that the proposed technique outperforms the conventional piece-wise model in terms of model errors.

Place, publisher, year, edition, pages
Belgrade, Serbia: , 2018
Keywords
Nonlinear dynamic RF power amplifier, behavioral modeling, piece-wise models, digital predistortion.
National Category
Signal Processing
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-241117 (URN)10.1109/TELFOR.2018.8611865 (DOI)000459714200035 ()2-s2.0-85062060510 (Scopus ID)978-1-5386-7171-9 (ISBN)
Conference
26th Telecommunications forum TELFOR 2018, Serbia, Belgrade, November 20-21, 2018.
Note

QC 20190114

Available from: 2019-01-11 Created: 2019-01-11 Last updated: 2019-05-21Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2718-0262

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