Marc Loschonsky

Characterization of delay spread for mobile radio communications under collapsed buildings

Numerous investigations of mobile radio communication have been conducted in environments such as urban, outdoor-to-indoor or indoor, only a few are in ruins. Within a running project, I-LOV, a study of a mobile radio propagation channel in urban search and rescue scenarios is conducted. Due to complex environment in ruins, great multipath interference can take place, which strongly impacts communication quality and localization accuracy. This paper focuses on the characterization of time dispersion in such scenarios at GSM 900, GSM 1800 and UMTS frequency bands. High resolution measurements have been performed under collapsed buildings and post-processing data analysis were executed. The mean delay and RMS delay spread has been investigated according to power delay profiles. The effect of frequency window function on impulse responses and delay spread is also researched.

Measurement of mobile radio propagation channel in ruins

Within a running project, I-LOV1, wireless communication channel model for mobile communications is developed based on measurements in reconstructed disaster and salvage scenarios. Due to complex environment in ruins, great multipath interference can take place, which strongly impacts communication quality and localization accuracy. Besides numerous measurements investigated in environments such as urban, outdoor-to-indoor or indoor, only a few are in ruins. This paper presents the first results of channel propagation measurements under collapsed buildings at GSM 900 and GSM 1800 bands. Measurement campaigns were performed in two typical collapsed structures: stratified and chaotic rubbles. The statistical properties of path-loss (PL) and RMS delay spread (DS) are reported.

Large-scale fading model for mobile communications in disaster and salvage scenarios

Within a running project, I-LOV, wireless communication channel model for mobile radio propagation in disaster and salvage scenarios is developed. This contribution focuses on a semi-empirical large-scale fading (LSF) model, which is able to estimate signal power loss between base station and mobile phone under debris. Due to multitude of diverse materials appearing in burying scenarios, the signal loss factor varies heavily depending on electromagnetic properties of involved materials. Additionally, highly variable shape and dimension of rubbles impact strongly the loss factor. Besides numerous LSF models investigated in urban environments, only a few are in ruins. This paper presents a novel modeling concept of LSF in catastrophe scenarios. The proposed LSF model handles the radio propagation way in two parts: outside ruins and through the ruins. Measurements have been conducted at GSM 900 and GSM 1800 bands in collapsed buildings of stratified rubbles, as well as in an avalanche scenario. The model predication fits the measured data well.

Mass Sensitive Thin Film Bulk Acoustic Wave Resonators

The mass sensitive effect of RF-filter technology based film and a solidly-mounted acoustic bulk wave single resonator (FBARs and SBARs) is investigated for metrological use. For a high resolution of a sensor system all systematical errors like cross temperature sensitivity must be eliminated. A high quality factor Q is needed for stable oscillating for minimizing statistical errors. Experiments using FBAR and SBAR single resonators have been carried out in a vapor deposition facility and thermal chamber to analyze mass and temperature sensitive effects. The usage of more than one resonant mode with distinct polarization might allow the compensation of cross sensitivities

Autoregressive Modeling of Mobile Radio Propagation Channel in Building Ruins

This paper addresses an autoregressive (AR) spectral estimation technique adapted for modeling of radio propagation channel in collapsed buildings and urban ruins in the frequency domain. Two mobile communication bands, 900 and 1800 MHz, were investigated. Measured channel frequency responses (CFRs) were firstly modeled by an overestimated AR model. In order to reduce this initial model order, the original CFRs were filtered and decimated. The model order was then optimized using the criteria of the signal-to-noise ratio and the maximum excess delay. According to the different debris structures, antenna polarization and RFs, the final model order was from 3 up to 35. The normalized root mean square error of modeled CFRs was between 0.22-0.38 on average. In order to generate a channel simulator, the statistical distribution functions of the simulator parameters, such as the number, arrival time, and complex amplitude of multipath components, were computed from the AR estimated channel impulse responses. Each of these distributions corresponds to the frequency band, antenna polarization, and ruin structure as well.

New technologies for the search of trapped victims

This paper presents the results of a German research project aiming at improving Urban Search And Rescue (USAR). It comprises two wireless search technologies for the detection and localization of trapped or buried unconscious victims and auxiliary assisting technologies. Victims can be localized through their cellular phone (GSM) if it is active, but it might be out of order. Results detecting inactive phones are presented. However, with this technology a victim without cellular phone cannot be detected. In this case, a ground-penetrating, continuous wave radar can be used that is as well presented. A channel model for estimating signal disturbances in debris between victim and receiving antenna is proposed that aims at improving the accuracy of these technologies. Furthermore, the I-LOV system assists decision-makers by a mobile IT-system called FRIEDAA that allows gathering, processing, and representation of relevant information such as search results and personnel locations in real time. Therefore, infrastructure and inertial sensor based personal localization systems are presented.

a-plane GaN Shear Wave Thin Film Resonator

This paper focuses on metal-organic-vapor-phase-epitaxial (MOVPE) grown on a-plane gallium-nitride (GaN), representing a novel approach for piezoelectric materials with good prospects for quartz-crystal-microbalance (QMB), like sensors with respect to its biocompatibility and frequency filter applications. Material characteristics of gallium-nitride as well as the processing of shear wave resonators and their acoustical characteristics are as well discussed

High overtone bulk acoustic resonators for high temperature sensing applications

High overtone Bulk Acoustic Resonators have been developed for radio-frequency application such as oscillator stabilization, but also as an alternative to surface acoustic wave resonator for sensor development. In the present work, the possibility to operate such devices at temperature up to 800°C is investigated experimentally. Devices built using Aluminum Nitride deposited on Silicon with Platinum electrodes have been manufactured and resonance frequencies near the 434-MHz centered ISM band have been characterized from room conditions to 800°C. Although the exposition to such a temperature yields changes in the device response, it turns out that the operation is partly reversible and that these HBARs could operate without major defects for several tens of hours at such regimes. The development of wireless temperature sensors on this base then reveals accessible.

Self-synchronized energy efficient event detection with wireless sensor networks

The presented work aims at development of a management evaluation system (condition monitoring) in the event of an explosion using a network of wireless sensors. The flow of information in the situation assessment system is made possible with the applied energy autonomous and energy-efficient wireless sensor nodes. Through this evaluation system, we will be able to do a real time assessment on the state of the damaged infrastructure through which we will be able to react to the situation in the area in a timely manner. We will show a new wireless sensor network topology and develop new rules for self-synchronization for energy efficient and collision free communication which is capable of data transmission in the event of an emergency situation.

Radar-based measurements of periodic movements

In this work, the continuous wavelet transform (CWT) is used to analyze periodic motions, measured by contactless Doppler radar, which have small amplitudes, drifting frequencies and dropouts. Using a classical method like fast Fourier transform (FFT) for periodic signals results in loss of the time behavior of the signal, drifting frequencies and dropouts, causing distortion in the frequency peaks of the FFT signal [1]. An alternative is the short-time Fourier transform (STFT), also known as “Windowed FFT” (WFFT), where additional time information is obtained by sequential time shifted windowing of the input signal, but the fixed window size limits its time-frequency resolution [2]. The wavelets of the CWT have frequency dependent sizes, permitting the CWT to have an optimal time-frequency resolution. This enables the identifcation and tracking of the frequency, as well as detecting dropouts of the signals.