1.
Lundberg, Magnus, et al.
(författare)
Context aware power optimizations of wireless embedded Internet systems
2004
Ingår i: From the electrometer to the networked instruments. - Piscataway, NJ : IEEE Communications Society. - 078038248X ; , s. 91-95
Konferensbidrag (refereegranskat) abstract
A key issue in research around embedded Internet systems (EIS) is to reduce power consumption. We envision EIS devices with lifetimes in the range of months or even years. This calls for developing aggressive power management techniques with a high degree of context awareness. As a first step towards this goal we introduce a design methodology for making context aware power optimizations of EIS. The presented design methodology which is verified by experimental results is a promising first step in prolonging operating time of battery powered wireless EIS.
2.
Larsson, Erik G., 1974-
(författare)
The ubiquitous signal processing : Applications to communications, spectral analysis and array processing
2001
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
This dissertation is concerned with statistical signal processing and its applications. The thesis consists of three parts: I) applications to wireless communications, II) applications to spectral analysis and III) applications to array processing.In part I, an iterative receiver for interference suppression in a system using orthogonal space-time block codes (STBC) is derived. An extension of STBC to frequency-selective fading is developed and receiver structures are devised. Furthermore, the orthogonal frequency division multiplexing (OFDM) technique is discussed. New algorithms for synchronization and channel estimation in an OFDM system are proposed and the optimal design of training sequences in an OFDM system with transmit diversity is discussed.In part II, computationally efficient implementations of nonparametric spectral estimators are derived. A new high-resolution nonparametric spectral estimation method is devised and analyzed. Furthermore, a novel spectral analysis method for both one and two-dimensional discontinuously sampled data is developed.In part III, a new high-resolution finding technique is developed for the case when the observed data contain missing samples. Furthermore, Cramer-Rao bounds for direction estimation are examined under deterministic and stochastic data models, respectively. Finally, an algorithm for blind source separation is discussed and analyzed.
3.
4.
Bengtsson, Lars, 1963
(författare)
Signalbehandling
2003
Ingår i: Tabeller och Formler. - Stockholm : Liber AB. - 9147050926 ; , s. 355-360
Bokkapitel (övrigt vetenskapligt/konstnärligt) abstract
Denna formel- och tabellsamling innehåller grundläggande definitioner, tabeller och formler inom det naturvetenskapliga och tekniska området. Boken är lämplig för högskoleingenjörsutbildning och grundläggande utbildningar för civilingenjörer. Författarnas inriktning har varit att ge boken en sådan bredd att den också kan användas som referenslitteratur på gymnasiet.
5.
Lundin, Henrik, et al.
(författare)
On External Calibration of Analog-to-Digital Converters
2001
Ingår i: IEEE Workshop on Statistical Signal Processing. - NEW YORK : IEEE. ; , s. 377-380
Konferensbidrag (refereegranskat) abstract
External calibration and compensation of analog-to-digital converters is considered. Two novel methods are presented. Both methods employ multiple calibration frequencies in order to improve the wide-band performance of the converter. Also, a dynamic table indexing is introduced to further improve the performance. A recursive sine-wave reconstruction filter algorithm is developed for calibration purposes. The proposed methods are evaluated using experimental converter data. Results indicate that the dynamic indexing provides good correction performance, also at frequencies not used during calibration. Thus, wide-band calibration can be achieved.
6.
Mamontov, Eugen, 1955, et al.
(författare)
High-Dimensional Nonlinear Diffusion Stochastic Pprocesses. Modelling for Engineering Applications
2001
Bok (övrigt vetenskapligt/konstnärligt) abstract
This book is the first one devoted to high-dimensional (or large-scale) diffusion stochastic processes (DSPs) with nonlinear coefficients. These processes are closely associated with nonlinear Ito's stochastic ordinary differential equations (ISODEs) and with the space-discretized versions of nonlinear Ito's stochastic partial integro-differential equations. The latter models include Ito's stochastic partial differential equations (ISPDEs). The book presents the new analytical treatment which can serve as the basis of a combined, analytical-numerical approach to greater computational efficiency in engineering problems. A few examples discussed in the book include: the high-dimensional DSPs described with the ISODE systems for semiconductor circuits; the nonrandom model for stochastic resonance (and other noise-induced phenomena) in high-dimensional DSPs; the modification of the well-known stochastic-adaptive-interpolation method by means of bases of function spaces; ISPDEs as the tool to consistently model non-Markov phenomena; the ISPDE system for semiconductor devices; the corresponding classification of charge transport in macroscale, mesoscale and microscale semiconductor regions based on the wave-diffusion equation; the fully time-domain nonlinear-friction aware analytical model for the velocity covariance of particle of uniform fluid, simple or dispersed; the specific time-domain analytics for the long, non-exponential "tails" of the velocity in case of the hard-sphere fluid. These examples demonstrate not only the capabilities of the developed techniques but also emphasize the usefulness of the complex-system-related approaches to solve some problems which have not been solved with the traditional, statistical-physics methods yet. From this veiwpoint, the book can be regarded as a kind of complement to such books as "Introduction to the Physics of Complex Systems. The Mesoscopic Approach to Fluctuations, Nonlinearity and Self-Organization" by Serra, Andretta, Compiani and Zanarini, "Stochastic Dynamical Systems. Concepts, Numerical Methods, Data Analysis" and "Statistical Physics: An Advanced Approach with Applications" by Honerkamp which deal with physics of complex systems, some of the corresponding analysis methods and an innovative, stochastics-based vision of theoretical physics. To facilitate the reading by nonmathematicians, the introductory chapter outlines the basic notions and results of theory of Markov and diffusion stochastic processes without involving the measure-theoretical approach. This presentation is based on probability densities commonly used in engineering and applied sciences.
7.
Martin, Cristoff, et al.
(författare)
Approximate Transmit Covariance Optimization of MIMO Systems with Covariance Feedback
2003
Ingår i: Proceedings Asilomar Conference on Signals, Systems & Computers. - : IEEE. ; , s. 1047-1051
Konferensbidrag (refereegranskat) abstract
The data rate of a multiple input, multiple output (MIMO) communication link can be improved if knowledge about the channel statistics is exploited at the transmitter. However, many realistic system scenarios require computationally prohibitive Monte Carlo methods in order to optimize the transmit covariance for maximization of the exact mutual information. This paper instead considers an approximative approach to maximize the performance of a communication link where covariance feedback is available at the transmitter. The algorithm presented is based on an asymptotic expression of the mutual information that allows for correlation at both the transmit and the receive side of the system. From simulations we demonstrate significant gain over beamforming and pure divversity schemes in many realistic system scenarios.
8.
Wahlberg, Patrik, et al.
(författare)
Approximate time-variable coherence analysis of multichannel signals
2002
Ingår i: Multidimensional Systems and Signal Processing. - Norwell : Kluwer Academic Publishers. - 0923-6082 .- 1573-0824. ; 13:3, s. 237-264
Tidskriftsartikel (refereegranskat) abstract
We present a new method for signal extraction from noisy multichannel epileptic seizure onset EEG signals. These signals are non-stationary which makes time-invariant filtering unsuitable. The new method assumes a signal model and performs denoising by filtering the signal of each channel using a time-variable filter which is an estimate of the Wiener filter. The approximate Wiener filters are obtained using the time-frequency coherence functions between all channel pairs, and a fix-point algorithm. We estimate the coherence functions using the multiple window method, after which the fix-point algorithm is applied. Simulations indicate that this method improves upon its restriction to assumed stationary signals for realistically non-stationary data, in terms of mean square error, and we show that it can also be used for time-frequency representation of noisy multichannel signals. The method was applied to two epileptic seizure onset signals, and it turned out that the most informative output of the method are the filters themselves studied in the time-frequency domain. They seem to reveal hidden features of the epileptic signal which are otherwise invisible. This algorithm can be used as preprocessing for seizure onset EEG signals prior to time-frequency representation and manual or algorithmic pattern classification.
9.
Kliewer, J, et al.
(författare)
On the utilization of residual source redundancy for iterative joint source-channel decoding of variable-length codes
2002
Ingår i: ISIT. - NEW YORK : IEEE. - 0780375017 ; , s. 199-199
Konferensbidrag (refereegranskat) abstract
We present a novel symbol-based a-posteriori probability (APP) decoder for packetized variable-length encoded source indices transmitted over wireless channels, which exploits residual index correlations after source encoding for error correction. By additionally protecting the variable-length encoded bitstream with channel codes, an iterative decoding scheme can be obtained where the proposed APP source decoder serves as constituent decoder.
10.
Lundin, Henrik, et al.
(författare)
Analog-to-Digital Converter Error Correction using Frequency Selective Tables
2002
Ingår i: RadioVetenskap och Kommunikation (RVK). ; , s. 487-490
Konferensbidrag (övrigt vetenskapligt/konstnärligt) abstract
Error correction for analog-to-digital converters(ADCs) is considered. The frequency-dependent na-ture of ADC errors motivates the proposal of a novel scheme, incorporating look-up table correction andfast frequency estimation. The method is evaluated using experimental converter data, and the performance, measured in SFDR and SINAD, is found tobe superior to that of non frequency-dependent correction methods.
