Malgorzata Janson

Localization in industrial halls via ultra-wideband signals

In this work a study on an indoor ultra-wideband (UWB) localization system for applications in industrial buildings is presented. Industrial environments are known for beeing extremely difficult in terms of wireless communication, mainly due to the fact, that this sort of channels are characterized by high concentration of metal objects, which cause reflections, leading to strong multipath propagation. A three-dimensional model of the warehouse has been created and used for deterministic wave propagation simulations. In the simulation, the transmitter travels along a predefined route. The receiver infrastructure consists of eight antennas with known coordinates. By means of multiple simulations, the channel influence on the UWB signals has been determined. The implications of this influence, in terms of practical system design and localization accuracy, are assessed. Furthermore the influence of pulse detection methods and geometrical configurations of base-stations are investigated. The position calculation of the mobile beacon is realized using Time Difference of Arrival approach (TDoA), employing a direct solution as well as iterative methods. Eventually the accuracy of obtained results and the theoretical limit are considered based on dilution of precision (DOP) evaluations.

Indirect Localization and Imaging of Objects in an UWB Sensor Network

A method for the localization and the rough 2-D microwave imaging of objects is described. It detects and utilizes line-of-sight (LOS) paths between a mobile node and several fixed nodes of a distributed ultrawideband (UWB) sensor network. Objects are imaged in an indirect way, i.e., by a combination of maps, which show the distribution of LOS paths of individual network nodes. The method is demonstrated by means of ray-tracing simulations and measurements in a realistic environment. Performance limitation by diffraction and the question of temporal network node synchronization are discussed.

Dual-polarized UWB antenna array

The paper describes a dual-polarized antenna array for Impulse Radio Ultra Wideband (IR-UWB) applications. Firstly a brief description of the single radiator is given. Next the prototype is presented and measured data is compared with the simulated one. The linear array consisting of four components achieves a very narrow mean 3 dB beam width, which is approx. 15° in the FCC frequency range from 3.1 GHz to 10.6 GHz. The second main lobe of the array factor and the grating lobes are suppressed by the radiation pattern of the single element. The mean cross-polarization suppression in the main beam direction is larger than 20 dB. Next the simulated and measured time domain radiation properties of the antenna array are presented. The array is applicable in the polarimetric, impulse based ultra wideband systems with high angular selectivity and high range resolution.

Directional channel model for ultra-wideband indoor applications

In this paper a hybrid ray tracing/statistical channel model for the ultra-wideband (UWB) frequency range is proposed. The conventional ray tracing model is complemented with randomly distributed point scatterers placed on the surface of large objects like walls. The wave propagation in such scenario is calculated in a deterministic way. The parameters of the scatterers are derived from the measurements of reflection from typical indoor walls.

Polarization diversity in Ultra-Wideband imaging systems

This paper presents an Ultra-Wideband (UWB) indoor imaging system with dual-orthogonal polarized antennas. Both the measurement setup and the algorithm implemented for data processing are introduced. In the presented approach, a 4×1 vertically oriented antenna array is used in order to perform 2D scan. For 3D imaging, single antennas are applied. Emphasis is given to the polarization diversity, through which additional properties of objects such as form, surface structure and orientation are investigated. In this way, some objects are detected, which may remain invisible for single-polarized systems. In addition, the presented approach extends UWB-Radar/Imaging with very high resolution to a high-end system with robust target detection, while providing extensive information about the environment. Such a system can be of great interest in applications such as indoor search-and-rescue operations, motion tracking and indoor navigation.

Accuracy considerations of UWB localization systems dedicated to large-scale applications

This contribution considers the accuracy limits of ultra-wideband localization systems dedicated to large-scale applications. Industrial environments are known for being extremely difficult for wireless communication, mainly because of the high concentration of large metal objects, such as containers or machines; leading to strong multipath propagation. In this work a detailed 3D model of the warehouse is used for wave propagation simulations. In the simulation, the transmitter is moving along the predefined path and the receiver infrastructure consists of eight base stations. The aim is to model the tracking system and asses its accuracy - first, the upper bound of the accuracy is determined under ideal conditions and second, the precision estimation with the inclusion of effects of hardware non-idealities is done. Effects such as the influence of pulse detection methods, pulse shape and geometrical configuration of base-stations are investigated. The position calculation of the mobile beacon is realized using a Time Difference of Arrival approach. Eventually the accuracy of the obtained results and the theoretical limit are considered based on the dilution of precision evaluations.

BER Simulations of a UWB Spatial Multiplexing System Using an Extended Ray-Tracing Approach

This letter investigates the performance of a previously published hybrid channel model, where a standard ray-tracing model is combined with a statistical approach for simulation of dense multipath components. In particular, this hybrid method is compared against measurements and conventional ray-tracing simulations with respect to path loss, delay spread, and bit error rates of a 22 multiple-input-multiple output multiband OFDM (MIMO-MB-OFDM) system. It is seen that the hybrid method outperforms the conventional ray-tracing model, delivering very realistic performance estimates.

Performance of Time Domain Migration Influenced by Non-Ideal UWB Antennas

The antennas in ultrawideband (UWB) systems act as filters in both frequency domain and the spatial domain. This means that the antenna influence on a received signal varies with the wave incidence angle. This is particulary important for imaging systems, which make use of the time information of the received signals. However, since the incidence angles of the signals are not a priori known it is difficult to remove this effect from the measured data. To assess the antenna impact on the performance of the imaging system, in this work, simulated scattered signals are used as input for time domain migration algorithm. Then the image features like position errors, shape of the target image, resolution and coverage of an imaging system are extracted and compared for different real UWB antennas.

A Hybrid Deterministic-Stochastic Propagation Model for Short-Range MIMO-UWB Communication Systems

Abstract This paper presents a computationally effective approach for including dense multipath components in ray tracing simulations of ultra wideband (UWB) channels. Through a combination of a standard ray tracing model with a simple geometric-stochastic model realistic scenario-specific simulations are possible. The frequency and direction selectivity of the channel are reproduced accurately by the model. The structure and parameters of the stochastic part of the model are derived from measurements in the FCC-UWB frequency range. Compared to conventional ray tracing simulations the proposed model reduces considerably the differences between simulated and measured channel characteristics.

Dual-polarized UWB antenna for high-resolution-imaging-systems

This paper presents a modified dual-polarized antenna for UWB-Imaging-Systems with high resolution. The antenna possesses several properties, which are advantageous for UWB-Radar, e.g. high polarization purity, same phase center of radiation for both polarizations, similar beamwidths in the relevant planes, constant delay of the impulse response over the angle etc. The measured radiation characteristics of the prototype are shown and an example of an UWB-Image is presented. The antenna enables microwave imaging with unique resolution, which is in the cm-range in the angle and range direction.