Walter Grote
Universidad Técnica Federico Santa María, Electrónica, Faculty Member
... Collaborative Colleagues: Walter Grote: colleagues. Shivendra Panwar: colleagues. The ACM Portal is published by the Association for Computing Machinery. Copyright © 2010 ACM, Inc. Terms of Usage Privacy Policy Code ...
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Page 1. JM Rodríguez, Hristo D. Hristov and Walter Grote Departamento de Electrónica Universidad Técnica Federico Santa María Valparaíso, Chile hristo.hristov@usm.cl Abstract—A number of lens antennas with single-dielectric ...
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A number of lens antennas with single-dielectric phase-correcting Fresnel zone plate (FZP) lenses have been designed and studied numerically at microwave and terahertz frequencies, and contrasted to a similar in size and parameters... more
A number of lens antennas with single-dielectric phase-correcting Fresnel zone plate (FZP) lenses have been designed and studied numerically at microwave and terahertz frequencies, and contrasted to a similar in size and parameters ordinary refractive lens antenna. In a confined frequency band the terahertz grooved-dielectric FZP lenses/antennas with four or more phase-correction steps have gain, beamwidth, cross-polar isolation and input-mismatch comparable to those of the corresponding ordinary lens antenna. An examined 1.5-THz FZP lens antenna designed according to the here-proposed correction in FZP design equation can prevail in gain the ordinary lens antenna, but this finding is not valid for the examined 38-GHz (microwave) FZP lens antenna. Thus, the terahertz FZP lenses are thinner, lighter and effective options to the similar in diameter, focal length and building material ordinary lens for lens antennas construction.
By sharing the protection bandwidth of high- priority connections (HPC) with the bandwidth of low- priority (LPC) ones, NetFailPAC (network failure protection algorithm with class of service) establishes working (HPC and LPC) and... more
By sharing the protection bandwidth of high- priority connections (HPC) with the bandwidth of low- priority (LPC) ones, NetFailPAC (network failure protection algorithm with class of service) establishes working (HPC and LPC) and protection routes (for HPC only) in a WDM network. By using bandwidth as the main metric to select the working and backup paths, it outperforms previous proposals increasing high-priority connection setup capabilities from 0% to 50% without additional infrastructure, while maintaining similar network performance.
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Abstract Underwater Wireless Sensor Networks (UWSN) experience severe communication problems due to large acoustic or electromagnetic (EM) signal attenuation. The propagation of acoustic signals in submarine media is possible with very... more
Abstract Underwater Wireless Sensor Networks (UWSN) experience severe communication problems due to large acoustic or electromagnetic (EM) signal attenuation. The propagation of acoustic signals in submarine media is possible with very low frequency signal carriers ...
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Page 1. JM Rodríguez, Hristo D. Hristov and Walter Grote Departamento de Electrónica Universidad Técnica Federico Santa María Valparaíso, Chile hristo.hristov@usm.cl Abstract—A number of lens antennas with single-dielectric ...
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A conical double-dielectric phase-reversal Fresnel-zone plate (FZP) lens is introduced. We present the lens design equations as functions of cone opening angle. As an example, the phase-reversal lens has been applied to four... more
A conical double-dielectric phase-reversal Fresnel-zone plate (FZP) lens is introduced. We present the lens design equations as functions of cone opening angle. As an example, the phase-reversal lens has been applied to four millimeter-wave antennas with different lens opening semi-angles: 45deg, 60deg, and 75deg (conical lenses) and 90deg (plane lens). The radiation characteristics of these antennas have been calculated and contrasted one-to-another, and to those with the same semi-angles and linear dimensions binary (half-open) FZP lens antennas. The double-dielectric FZP conical arrangement can serve as a conical antenna lens and a radome simultaneously
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ABSTRACT
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Home networking is a developing area of research in telecommunications. The historical development of this sector has been shifting from node to network backbone design, and more recently, to access technologies, that is, from the core to... more
Home networking is a developing area of research in telecommunications. The historical development of this sector has been shifting from node to network backbone design, and more recently, to access technologies, that is, from the core to the periphery of the network. One of the ...
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Abstract Increasingly, wireless networks are being used to provide connection services for devices running applications with very different quality of service requirements. Although this issue has been addressed by the IEEE 802.11e... more
Abstract Increasingly, wireless networks are being used to provide connection services for devices running applications with very different quality of service requirements. Although this issue has been addressed by the IEEE 802.11e standard, the fact is that most networks deployed in ...
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The use of passive repeaters for mobile communications is often discarded because of the inherent losses that these systems introduce. However, the radio signal coverage of indoor areas poses a particularly complex problem in buildings... more
The use of passive repeaters for mobile communications is often discarded because of the inherent losses that these systems introduce. However, the radio signal coverage of indoor areas poses a particularly complex problem in buildings with heavily reinforced concrete walls and ...
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The prediction of wall losses is a fundamental aspect in the planning of cellular systems. The broad variety of building materials and construction codes makes accurate attenuation prediction very difficult without the support of detailed... more
The prediction of wall losses is a fundamental aspect in the planning of cellular systems. The broad variety of building materials and construction codes makes accurate attenuation prediction very difficult without the support of detailed structural data and measurements. In this ...
Resumen.-En este trabajo se resume la experiencia adquirida en el Departamento de Electrónica del la UTFSM para la realización de medidas de propagación de señales electromagnéticas en ambientes confinados, en lo relativo a selección de... more
Resumen.-En este trabajo se resume la experiencia adquirida en el Departamento de Electrónica del la UTFSM para la realización de medidas de propagación de señales electromagnéticas en ambientes confinados, en lo relativo a selección de ambientes, ...
IMPROVING INDOOR SIGNAL COVERAGE BY USE OF THROUGH-WALL PASSIVE REPEATERS Hristo D. Hristov*, Rodolfo Feick, Walter Grote Department of Electronic Engineering Universidad TBcnica Federico Santa Maria Valparaiso, Casilla 1 10-V, Chile... more
IMPROVING INDOOR SIGNAL COVERAGE BY USE OF THROUGH-WALL PASSIVE REPEATERS Hristo D. Hristov*, Rodolfo Feick, Walter Grote Department of Electronic Engineering Universidad TBcnica Federico Santa Maria Valparaiso, Casilla 1 10-V, Chile chris@elo.utfsm.cl
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Una llamada puede experimentar una probabilidad de bloqueo en un sector de celda de un sistema de comunicaciones móviles basado en GSM, cuando todos los canales ya han sido asignados. Con el objeto de disminuir la probabilidad de... more
Una llamada puede experimentar una probabilidad de bloqueo en un sector de celda de un sistema de comunicaciones móviles basado en GSM, cuando todos los canales ya han sido asignados. Con el objeto de disminuir la probabilidad de ocurrencia de este fenómeno para las llamadas de traspaso de una celda a otra, se reserva algunos de los canales para ofrecer un acceso privilegiado. Se propone extender este sistema de prioridad para llamadas entrantes asignando privilegios de acceso en orden creciente a datos, voz sin prioridad, voz con prioridad y traspaso. Estudios previos consideran sólo datos, voz y traspaso, pero incorporar una categoría de voz con prioridad puede ser útil para situaciones de emergencia. En este trabajo se calculan las probabilidades de bloqueo para cada clase de servicio mediante un sistema de ecuaciones basado en una cadena de Markov, para luego ser evaluado numéricamente usando Matlab.
Modern mining procedures aim to replace human resources directly involved in the mineral extraction process by automatic or remote control systems. Data may be collected from sensors, or data and/or video may be transmitted by... more
Modern mining procedures aim to replace human resources directly involved in the mineral extraction process by automatic or remote control systems. Data may be collected from sensors, or data and/or video may be transmitted by telecommunication equipment. The actual technology trend is to do these transmissions using wireless technology (WSN, Wi-Fi, among others). This work summarizes the experience that has been collected from characterizing a Single-Input-Single-Output (SISO) large scale 870 MHz and 2.45 GHz wireless propagation channel in an underground copper mine. Also the Rician K
factor and channel coherence time are calculated for a 2.45 GHz mobile link.
factor and channel coherence time are calculated for a 2.45 GHz mobile link.
Se ha introducido modificaciones a nivel de capa MAC al IEEE 802.11 con el fin de mejorar la calidad de servicio de las prestaciones basadas en filas de espera diferenciadas, para alcanzar mayores niveles de utilización del canal... more
Se ha introducido modificaciones a nivel de capa
MAC al IEEE 802.11 con el fin de mejorar la calidad de servicio
de las prestaciones basadas en filas de espera diferenciadas, para
alcanzar mayores niveles de utilización del canal reduciendo la
ineficiencia propia del protocolo de acceso aleatorio. La
literatura existente apunta mayoritariamente a redes Ad Hoc,
con todos los dispositivos usando la misma versión del estándar.
No obstante, las redes inalámbricas mayormente empleadas
considera dispositivos de distintos tipos comunicándose con un
Access Point (AP). Para analizar el desempeño sujeto a la
elección de parámetros de configuración apropiados se desarrolla
un modelo estocástico de una red inalámbrica heterogénea, con
terminales de voz y datos, operando en modo infraestructura,
destacando la importancia de configurar apropiadamente el AP
IEEE 802.11e/n. Luego se compara estos resultados con un
modelo determinista más simple de evaluar, pero, por lo mismo,
también más impreciso.
MAC al IEEE 802.11 con el fin de mejorar la calidad de servicio
de las prestaciones basadas en filas de espera diferenciadas, para
alcanzar mayores niveles de utilización del canal reduciendo la
ineficiencia propia del protocolo de acceso aleatorio. La
literatura existente apunta mayoritariamente a redes Ad Hoc,
con todos los dispositivos usando la misma versión del estándar.
No obstante, las redes inalámbricas mayormente empleadas
considera dispositivos de distintos tipos comunicándose con un
Access Point (AP). Para analizar el desempeño sujeto a la
elección de parámetros de configuración apropiados se desarrolla
un modelo estocástico de una red inalámbrica heterogénea, con
terminales de voz y datos, operando en modo infraestructura,
destacando la importancia de configurar apropiadamente el AP
IEEE 802.11e/n. Luego se compara estos resultados con un
modelo determinista más simple de evaluar, pero, por lo mismo,
también más impreciso.
World economies that are involved in mining activities are highly motivated to develop sensor networks that are able to send early warning signals to reduce the number of accidents, especially those that involve human injuries or deaths.... more
World economies that are involved in mining activities are highly motivated to develop sensor networks that are able to send early warning signals to reduce the number of accidents, especially those that involve human injuries or deaths. The factors with greatest impact in the cause of accidents in underground mines are the presence of pit gas, landslides and lack of information about the exact location of personnel in the event of a disaster. The development of sensor networks capable of measuring variables of interest related to the factors mentioned in real time, adding wireless communication capabilities for easy deployment and robustness, promises to be of great impact on safety for the mining industry. In this publication the main causes of accidents for underground coal mines are established, based on existing worldwide reports. Variables (temperature, gas, structural faults, fires and/or combustion engine machine effects presence) that can be related to the most frequent causes of disaster and its relevant measuring range are then presented. Sensor technology to measure these variables is also analyzed, taking into account operational principles, measurement range, precision, accuracy, linearity, sturdiness, sampling rate and then related to wireless sensor networks technology energy saving requirements. This publication focuses on coal mines, because these are the most accident prone underground mining environments. However, application of these results to copper mining activities is considered as well.
This paper presents an analytical model to calculate the total MAC delay experimented for packets, for stable network conditions. This model considers that each station of the network has an M/G/1 transmission queue. What differences this... more
This paper presents an analytical model to calculate the total MAC delay experimented for packets, for stable network conditions. This model considers that each station of the network has an M/G/1 transmission queue. What differences this paper from others is that the total delay is derived directly from the exact service time distribution of a packet of the backoff algorithm, instead of using approximations. The no-saturated channel model relies on the idle time of the station, which is also a new approach that avoids approximations from previous models. Evaluations of this model show that it is in close agreement with simulation results.