Large-scale fading characterization in curved modern subway tunnels

This paper presents extensive propagation measurements conducted in a modern arched tunnel with 300 m and 500 m radii of curvature with horizontal polarizations at 920 MHz, 2400 MHz, and 5705 MHz, respectively. Based on the measurements, statistical metrics of propagation loss and shadow fading in all the measurement cases are extracted. Furthermore, for each of the large-scale fading parameters, extensive analysis and discussions are made to reveal the physical laws behind the observations. The quantitative results and findings are useful to realize intelligent transportation systems in the subway system

Measurement and analysis of extra propagation loss of tunnel curve

Wave propagation experiences extra loss in curved tunnels, which is highly desired for network planning. Extensive narrow-band propagation measurements are made in two types of Madrid subway tunnels (different cross sections and curvatures) with various configurations (different frequencies and polarizations). A ray tracer validated by the straight and curved parts of the measuring tunnels is employed to simulate the reference received signal power by assuming the curved tunnel to be straight. By subtracting the measured received power in the curved tunnels from the simulated reference power, the extra loss resulting from the tunnel curve is extracted. Finally, this paper presents the figures and tables quantitatively reflecting the correlations between the extra loss and radius of curvature, frequency, polarization, and cross section, respectively. The results are valuable for statistical modeling and the involvement of the extra loss in the design and network planning of communication systems in subway tunnels

Experimental characterization of the radio channel for systems with large bandwidth and multiple antennas

[SPA] Cada día son necesarias comunicaciones mejores y más eficientes, con mayores anchos de banda y mayores tasas de transferencias de datos. Por un lado los sistemas de múltiples antenas, MIMO, surgieron como una técnica para optimizar el uso de la potencia y el espectro. Por otro lado, los sistemas Ultra-Wideband, UWB, han ganado recientemente el interés de la comunidad científica por su gran ancho de banda combinado con su baja potencia de transmisión. A la hora de diseñar y testear nuevos dispositivos de comunicaciones inalámbricas, es esencial poseer un conocimiento preciso del canal de propagación por el que se propagan dichas señales. Esta tesis, se basa en el modelado del canal de propagación para sistemas de gran ancho de banda y múltiples antenas desde un punto de vista experimental. Primeramente se presentan las mejoras y desarrollos realizados en el ámbito de los sistemas de medida del canal, dado que es necesario disponer de equipos adecuados y precisos para realizar adecuadas medidas del canal. Seguidamente, se analiza el canal MIMO-UWB en interiores. Se realiza un análisis en profundidad de varios parámetros, especialmente parámetros de una antena como las pérdidas de propagación, el factor de polarización cruzada o la dispersión del retardo. Finalmente, la tesis particulariza el análisis del canal en un entorno especial como es el caso de túneles. Se realiza un análisis experimental de parámetros de una antena como multi antena para luego evaluar las prestaciones que pueden brindar varias técnicas de diversidad como es en el dominio de la frecuencia, la polarización, el espacio o el tiempo.[ENG] Wireless communications have become essential in our society [Rappaport, 1996], [Parsons, 2000]. Nowadays, people need to be connected everywhere and at any time, and demand faster and enhanced communications every day. New applications requires higher data rates and, therefore, higher bandwidths. On the one hand, Multiple-Input Multiple-Output (MIMO) systems were proposed as one solution to achieve higher data rates and optimize the use of the spectrum. On the other hand, more recently, systems with an ultra large bandwidth, and particularly Ultra-Wideband (UWB) systems, have gained the interest of the scientific community. Such interest is owing to the extremely high data rates offered and its possible coexistence with existing systems due to the its low transmitted power. However, this improvement in mobile communications involves the development and testing of new wireless communications systems. Precise knowledge of the radio channel is an essential issue to design this new devices and, thus, reach such improvement in wireless communications. In general, the modeling of the radio channel can be undertaken in two main ways: Theoretically, where the channel is characterized by means of simulations and theoretical approaches. - Experimentally, where the radio channel is characterized by means of the analysis of measurements carried out in real scenarios. This thesis is mainly focused on the experimental characterization of the radio channel for systems with large bandwidth and multiple antennas (MIMO). However, characterizing experimentally the MIMO wideband channel implies the availability of adequate and accurate channel sounders.Universidad Politécnica de CartagenaUniversité des Sciences et Technologies de Lille (USTL)Programa de doctorado en Tecnologías de la Información y Comunicacione

Experimental characterization of non-stationary V2I radio channel in tunnels

The fading process in vehicular communications is inherently non-stationary. In this paper, vehicle-to-infrastructure (V2I) radio channel measurements are performed inside a tunnel for low and medium traffic conditions to estimate the stationarity time, in addition to the time-varying RMS delay and Doppler spreads. Furthermore, we show the good fit of the spreads to a lognormal distribution, as well as for the Rician K-factor of the fading amplitude. From our analysis we conclude that the traffic density has an impact on the large-scale parameters as it increases delay and Doppler spreads, while reducing the correlation between them as well as the average K-factor. Larger traffic densities may be required to impact the stationarity time

Measurements and analysis of large-scale fading characteristics in curved subway tunnels at 920 MHz, 2400 MHz, and 5705 MHz

ave propagation characteristics in curved tunnels are of importance for designing reliable communications in subway systems. This paper presents the extensive propagation measurements conducted in two typical types of subway tunnels—traditional arched “Type I” tunnel and modern arched “Type II” tunnel—with300- and 500-m radii of curvature with different configurations—horizontal and vertical polarizations at 920, 2400, and 5705 MHz, respectively. Based on the measurements, statistical metrics of propagation loss and shadow fading (path-loss exponent, shadow fading distribution, autocorrelation, and cross-correlation) in all the measurement cases are extracted. Then, the large-scale fading characteristics in the curved subway tunnels are compared with the cases of road and railway tunnels, the other main rail traffic scenarios, and some “typical” scenarios to give a comprehensive insight into the propagation in various scenarios where the intelligent transportation systems are deployed. Moreover, for each of the large-scale fading parameters, extensive analysis and discussions are made to reflect the physical laws behind the observations. The quantitative results and findings are useful to realize intelligent transportation systems in the subway system

Experimental study on the impact of antenna characteristics on non-stationary V2I channel parameters in tunnels

This paper analyses the experimentally-assessed dual-polarized (DP) mobile channel in a tunnel environment at 1.35 GHz under traffic conditions. We investigate the impact of antenna polarization and radiation pattern on the non-stationary vehicle-to-infrastructure (V2I) channel. Basic channel evaluation metrics are examined including path gain, co-polarization ratio (CPR), and cross-polarization discrimination (XPD). In addition, the stationarity region is estimated using the channel correlation function approach, and used to calculate the time-varying delay and Doppler power profiles. Statistical models are presented for parameters like CPR, XPD, RMS delay and Doppler spreads, where the lognormal distribution provides the best fit. The polarization and the opening angle of the antennas into the propagation channel are found to strongly influence the observed non-stationarity of the channel. They impact the degree of multipath richness that is captured, thus providing different path gain, delay and Doppler spreads. Based on our analysis, the directional antenna with vertical polarization provides the longest stationarity time of 400 ms at 90 km/h, as well as the highest path gain and lowest dispersion. Furthermore, the DP channel capacity is calculated and its dependence on different normalization approaches is investigated. We propose a more accurate normalization for the DP channels that takes the conservation of energy into account. Moreover, the subchannels correlation coefficients are determined. While the condition number is found to be low on average, the correlation results show high correlation among the DP subchannels. As conclusion, we show how the CPR and XPD play the main role in providing multiplexing gain for DP tunnel channels

Análisis teórico-experimental del canal radio en microceldas y entornos especiales para sistemas de comunicaciones móviles de banda ancha

Las comunicaciones inalámbricas forman parte de la vida diaria de la sociedad en la que vivimos. La comunicación a cualquier hora y desde cualquier lugar se ha convertido en requisito indispensable de calidad de las mismas. Además de esto, se ha incrementado la necesidad del intercambio de datos; cuando antes lo único que se requería eran simples conversaciones de voz, ahora son las transmisiones de datos a alta velocidad. Este aumento requiere sistemas avanzados de telecomunicaciones que permitan poder afrontar estas necesidades. La demanda de transferencia de grandes volúmenes de información vía radio hace necesario dirigir los esfuerzos hacia soluciones que aumenten la capacidad utilizando los escasos recursos radio. También está tomando mucha importancia la posibilidad de comunicación desde cualquier ubicación y en cualquier instante. La comunicación desde el interior de túneles, centros comerciales y en medios de transporte 2 Capítulo 1 entre otros lugares empieza a ser un nuevo requisito de diseño en los sistemas modernos de telecomunicaciones. Una de las tecnologías que permite aumentar la capacidad del bucle radio es la de comunicaciones de banda ancha, cuya capacidad es proporcional al ancho de banda utilizado. El análisis de estos sistemas se complica con respecto a los sistemas tradicionales, ya que surgen nuevos parámetros que caracterizan su comportamiento (apéndice B). Otra forma de aumentar la capacidad consiste en el uso de múltiples antenas a ambos lados del enlace de la comunicación. De esta forma es posible alcanzar eficiencias espectrales (bits/sg/Hz) impensables para sistemas convencionales. Esto es posible siempre y cuando se garantice que las señales que llegan y salen de los diversos elementos radiantes estén lo suficientemente decorreladas. Esta nueva tecnología se denominada en inglés MIMO (Múltiple-Input Múltiple-Output) (apéndice D). El desarrollo de estos sistemas de comunicaciones móviles pasa por disponer de modelos teóricos que tengan en cuenta los principales mecanismos de propagación en los distintos tipos de entornos. Estos modelos de propagación pueden proceder bien del análisis de los datos recogidos en campañas de medidas, o bien de modelos más complejos que resuelven el problema electromagnético desde un punto de vista teórico. Estos últimos buscan soluciones aproximadas que sean fáciles de implementar, y suelen dar lugar a resultados cuya solución es compromiso entre el tiempo de cálculo y precisión. En esta tesis se ha utilizado el modelo de trazado de rayos basado en la Óptica Geométrica (GO) y la Teoría Uniforme de la Difracción (UTD) (apéndice A). Por otra parte, la medida del canal radio es esencial para el estudio del mismo, ya que permite tanto la obtención de datos necesarios para la implementación de modelos como la verificación de estos. El objetivo principal de esta tesis es el estudio tanto teórico como experimental del canal radio en entornos microcelulares y especiales como túneles. Teórico, desde el punto de vista de desarrollar modelos eficientes de canal para sistemas de banda ancha y sistemas MIMO, y experimental, desde el punto de vista de la toma de medidas reales en estos entornos y la comparación con los modelos teóricos.Universidad Politécnica de Cartagen

Time-Reversal UWB Wireless Communication-Based Train Control in Tunnel

This paper reports an evaluation of UWB radio technology and Time-Reversal (TR) technique in tunnel environments for train-to-wayside communication. UWB technology has the potential to offer simultaneous ground-totrain communication, train location and obstacle detection in front of the trains. Time-Reversal channel pre-filtering facilitates signal detection and helps reduce interference. Thus, UWB-TR combination provides a challenging, economically sensible, as well as technically effective alternative solution to existing signaling technologies used in urban transport systems. This paper deals with deterministic channel modeling and its characterization in tunnel environment. It reports simulation performance evaluation of UWB-TR combinations in the developed channel model