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Pla, P. d., Pellaco, L., Dwivedi, S., Händel, P. & Jaldén, J. (2020). Clock Synchronization Over Networks: Identifiability of the Sawtooth Model. IEEE Open Journal of Signal Processing, 1, 14-27
Open this publication in new window or tab >>Clock Synchronization Over Networks: Identifiability of the Sawtooth Model
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2020 (English)In: IEEE Open Journal of Signal Processing, E-ISSN 2644-1322, Vol. 1, p. 14-27Article in journal (Refereed) Published
Abstract [en]

In this paper, we analyze the two-node joint clock synchronization and ranging problem. We focus on the case of nodes that employ time-to-digital converters to determine the range between them precisely. This specific design choice leads to a sawtooth model for the captured signal, which has not been studied before from an estimation theoretic standpoint. In the study of this model, we recover the basic conclusion of a well-known article by Freris, Graham, and Kumar in clock synchronization. More importantly, we discover a surprising identifiability result on the sawtooth signal model: noise improves the theoretical condition of the estimation of the phase and offset parameters. To complete our study, we provide performance references for joint clock synchronization and ranging using the sawtooth signal model by presenting an exhaustive simulation study on basic estimation strategies under different realistic conditions. With our contributions in this paper, we enable further research in the estimation of sawtooth signal models and pave the path towards their industrial use for clock synchronization and ranging.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2020
Keywords
Clock synchronization, ranging, identifiability, sawtooth model, sensor networks, round-trip time (RTT)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-310097 (URN)10.1109/OJSP.2020.2978762 (DOI)000722891600003 ()2-s2.0-85094059815 (Scopus ID)
Note

Not duplicate with DiVA 1540492, 1343762.

QC 20220319

Available from: 2022-03-19 Created: 2022-03-19 Last updated: 2024-01-08Bibliographically approved
Pla, P. d., Pellaco, L., Dwivedi, S., Händel, P. & Jaldén, J. (2020). Clock synchronization over networks using sawtooth models. In: 2020 IEEE international conference on acoustics, speech, and signal processing: . Paper presented at IEEE International Conference on Acoustics, Speech, and Signal Processing, MAY 04-08, 2020, Barcelona, SPAIN (pp. 5945-5949). Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>Clock synchronization over networks using sawtooth models
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2020 (English)In: 2020 IEEE international conference on acoustics, speech, and signal processing, Institute of Electrical and Electronics Engineers (IEEE) , 2020, p. 5945-5949Conference paper, Published paper (Refereed)
Abstract [en]

Clock synchronization and ranging over a wireless network with low communication overhead is a challenging goal with tremendous impact. In this paper, we study the use of time-to-digital converters in wireless sensors, which provides clock synchronization and ranging at negligible communication overhead through a sawtooth signal model for round trip times between two nodes. In particular, we derive Cramer-Rao lower bounds for a linearitzation of the sawtooth signal model, and we thoroughly evaluate simple estimation techniques by simulation, giving clear and concise performance references for this technology.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2020
Series
International Conference on Acoustics Speech and Signal Processing ICASSP, ISSN 1520-6149
Keywords
Clock synchronization, ranging, wireless sensor networks (WSN), round-trip time
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Telecommunications Signal Processing
Identifiers
urn:nbn:se:kth:diva-292077 (URN)10.1109/ICASSP40776.2020.9054426 (DOI)000615970406041 ()2-s2.0-85089219684 (Scopus ID)
Conference
IEEE International Conference on Acoustics, Speech, and Signal Processing, MAY 04-08, 2020, Barcelona, SPAIN
Note

Part of proceedings: ISBN 9781509066315

QC 20210329. QC 20220319

Available from: 2021-03-29 Created: 2021-03-29 Last updated: 2022-06-25Bibliographically approved
Venkitaraman, A., Chatterjee, S. & Händel, P. (2020). Gaussian Processes over Graphs. In: 2020 IEEE International Conference on Acoustics Speech and Signal Processing ICASSP: . Paper presented at 2020 IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP 2020; Barcelona; Spain; 4 May 2020 through 8 May 2020 (pp. 5640-5644). Institute of Electrical and Electronics Engineers (IEEE), Article ID 9053859.
Open this publication in new window or tab >>Gaussian Processes over Graphs
2020 (English)In: 2020 IEEE International Conference on Acoustics Speech and Signal Processing ICASSP, Institute of Electrical and Electronics Engineers (IEEE), 2020, p. 5640-5644, article id 9053859Conference paper, Published paper (Refereed)
Abstract [en]

Kernel Regression over Graphs (KRG) was recently proposed for predicting graph signals in a supervised learning setting, where the inputs are agnostic to the graph. KRG model predicts targets that are smooth graph signals as over the given graph, given the input when all the signals are deterministic. In this work, we consider the development of a stochastic or Bayesian variant of KRG. Using priors and likelihood functions, our goal is to systematically derive a predictive distribution for the smooth graph signal target given the training data and a new input. We show that this naturally results in a Gaussian process formulation which we call Gaussian Processes over Graphs (GPG). Experiments with real-world datasets show that the performance of GPG is superior to a conventional Gaussian Process (without the graph-structure) for small training data sizes and under noisy training.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2020
Series
International Conference on Acoustics Speech and Signal Processing ICASSP, ISSN 1520-6149
Keywords
Graph signal processing, Gaussian processes, Bayesian estimation, kernel regression, graph-Laplacian
National Category
Probability Theory and Statistics
Identifiers
urn:nbn:se:kth:diva-292363 (URN)10.1109/ICASSP40776.2020.9053859 (DOI)000615970405180 ()2-s2.0-85089226492 (Scopus ID)
Conference
2020 IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP 2020; Barcelona; Spain; 4 May 2020 through 8 May 2020
Note

QC 20210401

Available from: 2021-04-01 Created: 2021-04-01 Last updated: 2022-06-25Bibliographically approved
Händel, P., Demir, O. T., Björnson, E. & Ronnow, D. (2020). Impact of Backward Crosstalk in 2 x 2 MIMO Transmitters on NMSE and Spectral Efficiency. IEEE Transactions on Communications, 68(7), 4277-4292
Open this publication in new window or tab >>Impact of Backward Crosstalk in 2 x 2 MIMO Transmitters on NMSE and Spectral Efficiency
2020 (English)In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 68, no 7, p. 4277-4292Article in journal (Refereed) Published
Abstract [en]

We consider backward crosstalk in 2 x 2 transmitters, which is caused by crosstalk from the outputs of the transmitter to the inputs or by the combination of output crosstalk and impedance mismatch. We analyze its impact via feedback networks together with third-order power amplifier non-linearities. We utilize the Bussgang decomposition to express the distorted output signals of the transmitter as a linear transformation of the input plus uncorrelated distortion. The normalized mean-square errors (NMSEs) between the distorted and desired amplified signals are expressed analytically and the optimal closed-form power back-off that minimizes the worst NMSE of the two branches is derived. In the second part of the paper, an achievable spectral efficiency (SE) is presented for the communication from this "dirty" transmitter to another single-antenna receiver. The SE-maximizing precoder is optimally found by exploiting the hardware characteristics. Furthermore, the optimal power back-off is analyzed for two sub-optimal precoders, which either do not exploit any hardware knowledge or only partial knowledge. The simulation results show that the performance of these sub-optimal precoders is close-to-optimal. We also discuss how the analysis in this paper can be extended to transmitters with an arbitrary number of antenna branches.

Place, publisher, year, edition, pages
IEEE, 2020
Keywords
Orthogonal frequency-division multiplexing (OFDM), input back-off, power amplifier, transmitter hardware imperfections, spectral efficiency
National Category
Signal Processing
Identifiers
urn:nbn:se:kth:diva-279202 (URN)10.1109/TCOMM.2020.2988927 (DOI)000552840100027 ()2-s2.0-85088522675 (Scopus ID)
Note

QC 20200824

Available from: 2020-08-24 Created: 2020-08-24 Last updated: 2024-03-15Bibliographically approved
Händel, P. & Ronnow, D. (2020). MIMO and Massive MIMO Transmitter Crosstalk. IEEE Transactions on Wireless Communications, 19(3), 1882-1893
Open this publication in new window or tab >>MIMO and Massive MIMO Transmitter Crosstalk
2020 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 19, no 3, p. 1882-1893Article in journal (Refereed) Published
Abstract [en]

The effects of hardware-induced crosstalk in MIMO transmitters, subject to nonlinear power amplifier distortion, are considered in this paper. A methodology that provides tractable results and a clear understanding of the effects of crosstalk on transmitter performance is introduced and applied to different transmitter models. In particular, a physically motivated 2 x 2 MIMO transmitter model, which is subjected to input and output crosstalk, is studied in detail, as well as a behavior motivated transmitter model, which is subjected to linear crosstalk. For the latter structure, asymptotic results, when the number of transmitters tends to infinity, are derived. These results provide insight into different 1D and 2D transmitter structures in the massive MIMO scenario. The methodology provides tractable analytical results of the performance of the transmitter. It is shown that the transmitter crosstalk degrades the performance in terms of normalized mean squared error with 3 dB going from a 2 x 2 set-up to a 1D array of a massive amount of transmitters, and an additional 3 dB loss going from a 1D to 2D transmitter structure. Transmitter input power back-off optimization is further studied, with back-off determination that takes the effects of MIMO crosstalk into account in order to increase the energy efficiency of the transmitter.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020
Keywords
Orthogonal frequency division multiplexing (OFDM), input back-off, massive MIMO, power amplifier, transmitter hardware imperfections
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-271936 (URN)10.1109/TWC.2019.2959534 (DOI)000521186100030 ()2-s2.0-85081726843 (Scopus ID)
Note

QC 20200420

Available from: 2020-04-20 Created: 2020-04-20 Last updated: 2022-06-26Bibliographically approved
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: 2022-06-26Bibliographically 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: 2022-06-26Bibliographically 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: 2022-06-26Bibliographically 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: 2022-06-26Bibliographically 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: 2022-06-26Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2718-0262

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