Precoding in multigateway multibeam satellite systems

This paper considers a multigateway multibeam satellite system with multiple feeds per beam. In these systems, each gateway serves a set of beams (cluster) so that the overall data traffic is generated at different geographical areas. Full frequency reuse among beams is considered so that interference mitigation techniques are mandatory. Precisely, this paper aims at designing the precoding scheme which, in contrast to single gateway schemes, entails two main challenges. First, the precoding matrix shall be separated into feed groups assigned to each gateway. Second, complete channel state information (CSI) is required at each gateway, leading to a large communication overhead. In order to solve these problems, a design based on a regularized singular value block decomposition of the channel matrix is presented so that both intercluster (i.e., beams of different clusters) and intracluster (i.e., beams of the same cluster) interference is minimized. In addition, different gateway cooperative schemes are analyzed in order to keep the inter-gateway communication low. Furthermore, the impact of the feeder link interference (i.e., interference between different feeder links) is analyzed and it is shown both numerically and analytically that the system performance is reduced severely whenever this interference occurs even though precoding reverts this additional interference. Finally, multicast transmission is also considered. Numerical simulations are shown considering the latest fixed broadband communication standard DVB-S2X so that the quantized feedback effect is evaluated. The proposed precoding technique results to achieve a performance close to the single gateway operation even when the cooperation among gateways is low.Postprint (author's final draft

Precoding in multigateway multibeam satellite systems

This paper considers a multigateway multibeam satellite system with multiple feeds per beam. In these systems, each gateway serves a set of beams (cluster) so that the overall data traffic is generated at different geographical areas. Full frequency reuse among beams is considered so that interference mitigation techniques are mandatory. Precisely, this paper aims at designing the precoding scheme which, in contrast to single gateway schemes, entails two main challenges. First, the precoding matrix shall be separated into feed groups assigned to each gateway. Second, complete channel state information (CSI) is required at each gateway, leading to a large communication overhead. In order to solve these problems, a design based on a regularized singular value block decomposition of the channel matrix is presented so that both intercluster (i.e., beams of different clusters) and intracluster (i.e., beams of the same cluster) interference is minimized. In addition, different gateway cooperative schemes are analyzed in order to keep the inter-gateway communication low. Furthermore, the impact of the feeder link interference (i.e., interference between different feeder links) is analyzed and it is shown both numerically and analytically that the system performance is reduced severely whenever this interference occurs even though precoding reverts this additional interference. Finally, multicast transmission is also considered. Numerical simulations are shown considering the latest fixed broadband communication standard DVB-S2X so that the quantized feedback effect is evaluated. The proposed precoding technique results to achieve a performance close to the single gateway operation even when the cooperation among gateways is low.Postprint (author's final draft

Transmit Beamforming Design with Received-Interference Power Constraints: The Zero-Forcing Relaxation

The use of multi-antenna transmitters is emerging as an essential technology of the future wireless communication systems. While Zero-Forcing Beamforming (ZFB) has become the most popular low-complexity transmit beamforming design, it has some drawbacks basically related to the effort of "trying" to invert the channel coefficients towards the interfered users. In particular, ZFB performs poorly in the low Signal-to-Noise Ratio (SNR) regime and does not work when the interfered users outnumber the transmit antennas. In this paper, we study in detail an alternative transmit beamforming design framework, where we allow some residual received-interference power instead of trying to null it completely out. Subsequently, we provide a close-form non-iterative optimal solution that avoids the use of sophisticated convex optimization techniques that compromise its applicability onto practical systems. Supporting results based on numerical simulations show that the proposed transmit beamforming is able to perform close to the optimal with much lower computational complexity.Grant numbers : TERESA - Hybrid TERrEstrial/Satellite Air Interface for 5G and Beyond project (code : TEC2017-90093-C3-1-R).@ 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

Evaluation of wave loads on a new type of perforated caisson

Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.A new type of perforated breakwater has been tested combining the advantages of cylindrical geometry with stepped wave energy dissipation. Thus, the new type of caisson implies a significant reduction of maximum wave forces, as well as loads transmitted to the foundation in comparison with conventional vertical breakwater and other types of perforated caissons. Starting from a brief description of the model and test results, this paper describes the development of a methodology for the estimation of maximum wave loads on this type of breakwater, in order to become a generalisable tool for predesign purposes. Construction and installation constraints of this new type of caisson are also assessed. These need to be taken into account in order to keep some advantages from the proposed design, while noting the key factors from a practical point of view.Peer ReviewedPostprint (published version

Shorter Still: Compressing C-C Single Bonds

How short can a C-C single bond get? The bonding in a set of molecules that are related structurally to previously synthesized or theoretically examined systems with short C-C bonds is investigated. According to calculations, a single C-C bond could be compressed to 1.313 A! To the best of our knowledge, this is the shortest single C-C bond reported to date. This shortening is a consequence of a change in the C-C-C bond angle, θ, to minimize strain in the cages and an effort to offset the tension in the surrounding bridges

Land use change and its socio-economic implications in the MazahuaArea of the Mexican highlands

A nivel mundial, regional y local existen diversos factores que influyen en el cambio del uso del suelo, como son los ambientales, demográficos, económicos y socioculturales, en su conjunto llegan a provocar un deterioro ambiental y pérdida de la diversidad biológica (Bocco, 2001). Las investigaciones de los procesos de cambio de uso del suelo (identificación y análisis de los factores e impactos en los ecosistemas), incluyen además de la caracterización y diagnóstico de las diversas cubiertas (naturales y artificiales), usos del suelo que comprenden un determinado territorio. En la actualidad para este tipo de estudios se ha propuesto el uso de metodologías y procedimientos estadísticos innovadores, que se complementan con técnicas de trabajo de campo, así como el uso y aplicación de herramientas de los denominados sistemas de información geográfica y de cartografía automatizada (Turner y Meyer 1994)

Cambio de uso de suelo e implicaciones socioeconómicas en un área mazahua del altiplano mexicano

Se analizan los cambios de uso del suelo entre 2000 y 2010 de la región mazahua del Estado de México y sus implicaciones socioeconómicas. El estudio se sustenta en la geografía socioeconómica de Bonfil (1996) y los procesos de cambio de uso del suelo de Fernández y Prados (2010) para evaluar los cambios de uso del suelo. Se utilizó clasificación supervisada de máxima probabilidad y datos socioeconómicos y demográficos. Los resultados de análisis de imágenes fueron verificados mediante recorridos en campo. Los cambios pueden deberse al crecimiento poblacional, en los modos de vida y su consecuente demanda de alimentos y viviendas.Se analizan los cambios de uso del suelo entre 2000 y 2010 de la región mazahua del Estado de México y sus implicaciones socioeconómicas. El estudio se sustenta en la geografía socioeconómica de Bonfil (1996) y los procesos de cambio de uso del suelo de Fernández y Prados (2010) para evaluar los cambios de uso del suelo. Se utilizó clasificación supervisada de máxima probabilidad y datos socioeconómicos y demográficos. Los resultados de análisis de imágenes fueron verificados mediante recorridos en campo. Los cambios pueden deberse al crecimiento poblacional, en los modos de vida y su consecuente demanda de alimentos y viviendas

Activity monitoring in professional soccer goalkeepers during training and match play

The purpose of the present study was to quantify the external load of professional soccer goalkeepers. Twenty professional goalkeepers participated in the study. Data were classified according to the number of days before or after the match day (MD) as follows: MD-4, MD-3, MD-2, MD-1 for the sessions before the match, and MD+1 for the session after the match. The total running distance covered (TD), the high metabolic load (HMLD), the number of high metabolic load efforts (HMLE) were progressively reduced from MD-4 to MD-1 but the values of these variables were always inferior to MD (ES: -3.79 to −1.11). There was a tendency for a progressive reduction in the number of high-intensity accelerations (ACC) and decelerations (DEC) from MD-4 to MD-1 although the values of ACC/DEC were superior to MD (ES: 0.19 to 2.05). Overall, MD-2 was the day with the lowest external load. During training sessions, starter goalkeepers performed more TD (ES: 0.36) and more HMLE (ES: 0.29) than non-starters. External load was progressively decreased in the days before match play for goalkeepers which is reflective of appropriate recovery and preparation practices within the cohort analysed. However, habitual goalkeepers training has an excess of accelerations/decelerations and a lack of running actions performed at high metabolic loads