Construcción de mapas de cobertura para comunicaciones inalámbricas

Conocer ciertas características sobre cómo es la propagación de la señal en determinados entornos es de vital importancia para el uso efectivo de una red de comunicaciones inalámbrica. Dependiendo de la complejidad del medio podemos utilizar como guía uno o varios modelos de propagación, pudiéndose llegar a buenas aproximaciones sobre el comportamiento de la señal. Bien sea para desarrollar modelos (empíricos o deterministas) o validarlos, se requieren mediciones experimentales. En otros casos no se dispone de un modelo de propagación, por lo que la única opción radica en tomar mediciones prácticas. Cualquiera sea el caso, a través de la representación de estas mediciones en función de la posición obtenemos lo que se suele llamar un mapa de comunicaciones o mapa de cobertura. Situados en este contexto, en este trabajo se desarrollaron herramientas para la construcción de mapas de comunicaciones a gran escala y a pequeña escala. Pensando en una solución modular, se desarrollaron diversos módulos para el meta sistema operativo ROS y se implementaron en un vehículo real todoterreno, y en un robot Pioneer P3AT. Se realizaron pruebas en un ambiente de especial interés para el grupo RoPeRT (Robotics, Perception and Real Time) de la Universidad de Zaragoza: el túnel ferroviario de Somport, que conecta Francia con España. Se obtuvo un mapa de cobertura a gran escala de una sección de especial interés, de unos 2.5 km de largo con cambio de pendiente, y uno más detallado a menor escala de una sección de 1 Km, donde aparecen atenuaciones importantes. Se compararon los resultados con un modelo de propagación basado en “Ray Tracing” (trazado de rayos), desarrollado por Valenzuela (1993). Se obtuvieron similitudes como la existencia de un notable fading, pero a la vez diferencias que dan importancia a las mediciones realizadas, como la ubicación de este fading y diversas atenuaciones que no aparecen en las simulaciones. Se verificó la repetibilidad de estos fenómenos realizando diversos experimentos, inclusive en días diferentes, cuestión que no se ha sido tratada con importante énfasis en la literatura. También se encontró que, debido a variaciones transversales, aplicando una diversidad espacial muy superior a la de las tarjetas comerciales, podemos mejorar la calidad de señal en la mayoría del trayecto estudiado. Los resultados obtenidos pueden ser utilizados tanto para el despliegue óptimo de redes inalámbricas, hasta inclusive para el desarrollo de técnicas de navegación para equipos multi-robot manteniendo la comunicación

Ground robotics in tunnels: Keys and lessons learned after 10 years of research and experiments

The work reported in this article describes the research advances and the lessons learned by the Robotics, Perception and Real-Time group over a decade of research in the field of ground robotics in confined environments. This study has primarily focused on localization, navigation, and communications in tunnel-like environments. As will be discussed, this type of environment presents several special characteristics that often make well-established techniques fail. The aim is to share, in an open way, the experience, errors, and successes of this group with the robotics community so that those that work in such environments can avoid (some of) the errors made. At the very least, these findings can be readily taken into account when designing a solution, without needing to sift through the technical details found in the papers cited within this text

Prog Electromagn Res C Pier C

Understanding wireless channels in complex mining environments is critical for designing optimized wireless systems operated in these environments. In this paper, we propose two physics-based, deterministic ultra-wideband (UWB) channel models for characterizing wireless channels in mining/tunnel environments - one in the time domain and the other in the frequency domain. For the time domain model, a general Channel Impulse Response (CIR) is derived and the result is expressed in the classic UWB tapped delay line model. The derived time domain channel model takes into account major propagation controlling factors including tunnel or entry dimensions, frequency, polarization, electrical properties of the four tunnel walls, and transmitter and receiver locations. For the frequency domain model, a complex channel transfer function is derived analytically. Based on the proposed physics-based deterministic channel models, channel parameters such as delay spread, multipath component number, and angular spread are analyzed. It is found that, despite the presence of heavy multipath, both channel delay spread and angular spread for tunnel environments are relatively smaller compared to that of typical indoor environments. The results and findings in this paper have application in the design and deployment of wireless systems in underground mining environments.CC999999/Intramural CDC HHS/United States2018-02-14T00:00:00Z29457801PMC5812029vault:2734

Measurement, Modeling, and OFDM Synchronization for the Wideband Mobile-to-Mobile Channel

Wideband measurements of the mobile-to-mobile channel, especially of the harshest channels, are necessary for proper design and certification testing of mobile-to-mobile communications systems. A complete measurement implies that the Doppler and delay characteristics are measured jointly. However, such measurements have not previously been published. The main objective of the proposed research is to develop channel models for specific scenarios from data obtained in a wideband mobile-to-mobile measurement campaign in the 5.9 GHz frequency band. For this purpose we developed a channel sounding system including a novel combined waveform. In order to quantify and qualify either the recorded channel or the proposed generated channel, we developed a simulation test-bed that includes all the characteristics of the proposed digital short range communications (DSRC) standard. The resulting channel models needed to comply with the specifications required by hardware channel emulators or software channel simulators. From the obtained models, we selected one to be included in the IEEE 802.11p standard certification test. To further aid in the development of software radio based receivers, we also developed an orthogonal frequency division multiplexing (OFDM) synchronization algorithm to analyze and compensate synchronization errors produced by inaccessible system clocks.Ph.D.Committee Chair: Ingram, Mary Ann; Committee Member: Lanterman, Aaron; Committee Member: Li, Ye; Committee Member: Pratt, Thomas G.; Committee Member: Rogers, Peter H