Genetic Algorithm-based Beamforming in Subarray Architectures for GEO Satellites

The incorporation of subarrays in Direct Radiating Arrays for satellite missions is fundamental in reducing the number of Radio Frequency chains, which correspondingly diminishes cost, power consumption, space, and mass. Despite the advantages, previous beamforming schemes incur significant losses during beam scanning, particularly when hybrid beamforming is not employed. Consequently, this paper introduces an algorithm capable of compensating for these losses by increasing the power, for this, the algorithm will activate radiating elements required to address a specific Effective Isotropic Radiated Power for a beam pattern over Earth, projected from a GeoStationary satellite. In addition to the aforementioned compensation, other beam parameters have been addressed in the algorithm, such as beamwidth and Side Lobe Levels. To achieve these objectives, we propose employing the array thinning concept through the use of genetic algorithms, which enable beam shaping with the desired characteristics and power. The full array design considers an open-ended waveguide, configured to operate in circular polarization within the Ka-band frequency range of 17.7-20.2 GHz

Construcción de una Estrategia para el Monitoreo Integrado de los Ecosistemas de Alta Montaña en Colombia

We present a synthesis of a proposal for integrated monitoring of high Andean ecosystems in Colombia, formulated through a process of discussion and consultation with multiple stakeholders with experience in monitoring mountain ecosystems in the country. The proposal takes as point of departure the need for developing integrated monitoring systems, with an adaptive management approach that allows evaluation of impacts of changes in socio-economic contexts and the effects of global change on biodiversity and ecosystem services. Also, this approach provides relevant information for territorial planning, climate change adaptation and ecological restoration. We prioritize high Andean ecosystems in Colombia because they include strategic ecosystems such as paramos, wetlands and glaciers, are global biodiversity hotspots, provide key ecosystem services including regulation of water provision for a growing rural and urban population, and exhibit a high vulnerability to climate change. There are numerous monitoring schemes at a national level and in the Andean region of Colombia, including initiatives that monitor biomass and carbon, taxonomic and functional diversity, climate, hydrology and glacier dynamics, as well as studies on land-use and socio-economic dynamics. Considering this accumulated experience, we discuss the challenges for their assimilation into an integrated system and propose a multiscale conceptual model of the main drivers of change and the response variables that could be monitored, from the national to the ecosystem/plot scale. Finally, we present the main expected products of the strategy, a possible institutional framework and the next steps that we consider are necessary for promoting its consolidation.Se presenta una síntesis de la propuesta para una estrategia de monitoreo integrado de los ecosistemas de alta montaña en Colombia, formulada a través de un proceso de discusión y consulta con la participación de múltiples actores con experiencia en el monitoreo de ecosistemas altoandinos del país. La propuesta parte de la necesidad de contar con sistemas integrados de monitoreo con un enfoque de manejo adaptativo, que permitan evaluar el impacto de los cambios en el contexto político-económico y el cambio global sobre la biodiversidad y los servicios ecosistémicos, y que aporten insumos para la planificación territorial, la adaptación al cambio climático y la restauración ecológica. Se priorizan los ecosistemas altoandinos de Colombia ya que incluyen ecosistemas estratégicos como los páramos y glaciares y constituyen un hotspot global de biodiversidad, proveyendo servicios ecosistémicos clave como la regulación de la oferta hídrica para una creciente población rural y urbana. Adicionalmente presentan una alta exposición y vulnerabilidad frente al cambio climático. Existe un número importante de experiencias de monitoreo a nivel nacional y en la zona altoandina de Colombia, incluyendo esquemas de seguimiento de biomasa y carbono, diversidad taxonómica y funcional, clima, dinámica hídrica y glaciares, así como cambios en el uso de la tierra y las dinámicas socioambientales. Tomando como base esta experiencia, se discuten los retos que plantea su articulación en un sistema integrado y se presenta la síntesis de un modelo conceptual multiescalar de los principales procesos generadores de cambio y las principales variables respuestas que pudieran ser objeto de monitoreo, desde el ámbito nacional hasta el nivel de ecosistemas o parcelas. Finalmente, se presentan los principales productos esperados de la implementación de la estrategia, un esquema de organización institucional y los próximos pasos que consideramos necesarios para promover su consolidación

Monitoring mountains in a changing world: new horizons for the Global Network for Observations and Information on Mountain Environments (GEO-GNOME)

Mountains are globally distributed environments that provide significant societal benefits, a function that is increasingly compromised by climatic change, environmental stress, political and socioeconomic transformations, and unsustainable use of natural resources. Gaps in our understanding of these processes and their interactions limit our capacity to inform decisions, where both generalities of mountain regions (eg climate processes) and specificities (eg context-specific manifestations of climate risks) matter. The Global Network for Observations and Information on Mountain Environments (GEO-GNOME), a Group on Earth Observations initiative, aims to fill these gaps through accessible Earth Observation (EO) as well as in-situ data and information on global change drivers, conditions, and trends. A workshop convened by the Mountain Research Initiative (MRI) revised GEO-GNOME's work plan, galvanizing a network that promotes relevant monitoring of global change in mountains and is responsive to the integrated knowledge needs of policy, research, and management

Harnessing Supervised Learning for Adaptive Beamforming in Multibeam Satellite Systems

peer reviewedIn today's ever-connected world, the demand for fast and widespread connectivity is insatiable, making multibeam satellite systems an indispensable pillar of modern telecommunications infrastructure. However, the evolving communication landscape necessitates a high degree of adaptability. This adaptability is particularly crucial for beamforming, as it enables the adjustment of peak throughput and beamwidth to meet fluctuating traffic demands by varying the beamwidth, side lobe level (SLL), and effective isotropic radiated power (EIRP). This paper introduces an innovative approach rooted in supervised learning to efficiently derive the requisite beamforming matrix, aligning it with system requirements. Significantly reducing computation time, this method is uniquely tailored for real-time adaptation, enhancing the agility and responsiveness of satellite multibeam systems. Exploiting the power of supervised learning, this research enables multibeam satellites to respond quickly and intelligently to changing communication needs, ultimately ensuring uninterrupted and optimized connectivity in a dynamic world

Mapping evolutionary process: a multi-taxa approach to conservation prioritization

Human-induced land use changes are causing extensive habitat fragmentation. As a result, many species are not able to shift their ranges in response to climate change and will likely need to adapt in situ to changing climate conditions. Consequently, a prudent strategy to maintain the ability of populations to adapt is to focus conservation efforts on areas where levels of intraspecific variation are high. By doing so, the potential for an evolutionary response to environmental change is maximized. Here, we use modeling approaches in conjunction with environmental variables to model species distributions and patterns of genetic and morphological variation in seven Ecuadorian amphibian, bird, and mammal species. We then used reserve selection software to prioritize areas for conservation based on intraspecific variation or species-level diversity. Reserves selected using species richness and complementarity showed little overlap with those based on genetic and morphological variation. Priority areas for intraspecific variation were mainly located along the slopes of the Andes and were largely concordant among species, but were not well represented in existing reserves. Our results imply that in order to maximize representation of intraspecific variation in reserves, genetic and morphological variation should be included in conservation prioritization

User-Centric Beam Selection and Precoding Design for Coordinated Multiple-Satellite Systems

peer reviewedThis paper introduces a joint optimization framework for user-centric beam selection and linear precoding (LP) design in a coordinated multiple-satellite (CoMSat) system, employing a Digital-Fourier-Transform-based (DFT) beamforming (BF) technique. Regarding serving users at their target SINRs and minimizing the total transmit power, the scheme aims to efficiently determine satellites for users to associate with and activate the best cluster of beams together with optimizing LP for every satellite-to-user transmission. These technical objectives are first framed as a complex mixed-integer programming (MIP) challenge. To tackle this, we reformulate it into a joint cluster association and LP design problem. Then, by theoretically analyzing the duality relationship between downlink and uplink transmissions, we develop an efficient iterative method to identify the optimal solution. Additionally, a simpler duality approach for rapid beam selection and LP design is presented for comparison purposes. Simulation results underscore the effectiveness of our proposed schemes across various settings

Flexible Beamforming for Direct Radiating Arrays in Satellite Communications

peer reviewedOnboard satellite communication systems generate and manage coverage beams over the Earth. Depending on data traffic requirements, the number of beams, side lobe levels, nulls, and EIRP, their beamwidth must be efficiently generated and managed. Therefore, this paper describes an approach for beam pattern synthesis applied to geostationary satellite communication systems. The beam pattern synthesis can generate beams with a beamwidth variation from 0.45° to 1.5°, which can be controlled independently for the two principal cuts. In addition, other requirements have been considered, e.g., latitude, and longitude, required EIRP, minimum and maximum side love levels for the two principal cuts, and nulling direction. The output of the synthesizer is a weight matrix with beamforming coefficients of the required beam. The direct radiating array in this contribution utilizes an open-ended waveguide antenna as unit cell elements with a period of 0.875λ0 designed to work in left-hand circular polarization in the frequency band from 17.7 to 20.1 GHz. Since this design is intended for high-data rates applications, the minimum beamwidth requirements are very narrow. Therefore, 36× 36 sub-arrays of 4× 4 unit cells with a period of 3.5λ are considered to accomplish the beamwidth requirements while maintaining reduced computational and time resources for the weight matrix calculation compared to the conventional counterpart of 144× 144 unit cells. The results show that the algorithm, which uses the surrogate optimizer, can compute the weight matrix and synthesize the beam with a slight deviation from the input data

Elevation and latitude drives structure and tree species composition in Andean forests: Results from a large-scale plot network

Our knowledge about the structure and function of Andean forests at regional scales remains limited. Current initiatives to study forests over continental or global scales still have important geographical gaps, particularly in regions such as the tropical and subtropical Andes. In this study, we assessed patterns of structure and tree species diversity along ~ 4000 km of latitude and ~ 4000 m of elevation range in Andean forests. We used the Andean Forest Network (Red de Bosques Andinos, https://redbosques.condesan.org/) database which, at present, includes 491 forest plots (totaling 156.3 ha, ranging from 0.01 to 6 ha) representing a total of 86,964 identified tree stems ≥ 10 cm diameter at breast height belonging to 2341 identified species, 584 genera and 133 botanical families. Tree stem density and basal area increases with elevation while species richness decreases. Stem density and species richness both decrease with latitude. Subtropical forests have distinct tree species composition compared to those in the tropical region. In addition, floristic similarity of subtropical plots is between 13 to 16% while similarity between tropical forest plots is between 3% to 9%. Overall, plots ~ 0.5-ha or larger may be preferred for describing patterns at regional scales in order to avoid plot size effects. We highlight the need to promote collaboration and capacity building among researchers in the Andean region (i.e., South-South cooperation) in order to generate and synthesize information at regional scale.Fil: Malizia, Agustina. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Blundo, Cecilia Mabel. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Carilla, Julieta. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Osinaga Acosta, Oriana. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Cuesta, Francisco. Universidad de Las Américas; Ecuador. Consorcio para el Desarrollo Sostenible de la Ecorregión Andina; EcuadorFil: Duque, Alvaro. Universidad Nacional de Colombia. Sede Medellín; ColombiaFil: Aguirre, Nikolay. Universidad Nacional de Loja. Centro de Investigaciones Tropicales del Ambiente y la Biodiversidad; EcuadorFil: Aguirre, Zhofre. Universidad Nacional de Loja. Centro de Investigaciones Tropicales del Ambiente y la Biodiversidad; EcuadorFil: Ataroff, Michele. Universidad de Los Andes; VenezuelaFil: Baez, Selene. Escuela Politécnica Nacional; EcuadorFil: Calderón Loor, Marco. Universidad de Las Américas; Ecuador. Deakin University; AustraliaFil: Cayola, Leslie. Herbario Nacional de Bolivia; Bolivia. Missouri Botanical Garden; Estados UnidosFil: Cayuela, Luis. Universidad Rey Juan Carlos; EspañaFil: Ceballos, Sergio Javier. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Cedillo, Hugo. Universidad de Cuenca; EcuadorFil: Farfán Ríos, William. Universidad Nacional de San Antonio Abad del Cusco. Herbario Vargas; PerúFil: Feeley, Kenneth J.. University of Miami; Estados UnidosFil: Fuentes, Alfredo Fernando. Herbario Nacional de Bolivia; Bolivia. Missouri Botanical Garden; Estados UnidosFil: Gámez Álvarez, Luis E.. Universidad de Los Andes; VenezuelaFil: Grau, Hector Ricardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Homeier, Juergen. Universität Göttingen; AlemaniaFil: Jadan, Oswaldo. Universidad de Cuenca; EcuadorFil: Llambi, Luis Daniel. Escuela Politécnica Nacional; EcuadorFil: Loza Rivera, María Isabel. University of Missouri; Estados Unidos. Herbario Nacional de Bolivia; Bolivia. Missouri Botanical Garden; Estados UnidosFil: Macía, Manuel J.. Universidad Autónoma de Madrid; EspañaFil: Malhi, Yadvinder. University of Oxford; Reino UnidoFil: Malizia, Lucio Ricardo. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias; ArgentinaFil: Peralvo, Manuel. Consorcio para el Desarrollo Sostenible de la Ecorregión Andina; EcuadorFil: Pinto, Esteban. Consorcio para el Desarrollo Sostenible de la Ecorregión Andina; EcuadorFil: Tello, Sebastián. Missouri Botanical Garden; Estados UnidosFil: Silman, Miles. Center for Energy, Environment and Sustainability; Estados UnidosFil: Young, Kenneth R.. University of Texas at Austin; Estados Unido