Wireless Content Caching for Small Cell and D2D Networks

The fifth generation wireless networks must provide fast and reliable connectivity while coping with the ongoing traffic growth. It is of paramount importance that the required resources, such as energy and bandwidth, do not scale with traffic. While the aggregate network traffic is growing at an unprecedented rate, users tend to request the same popular contents at different time instants. Therefore, caching the most popular contents at the network edge is a promising solution to reduce the traffic and the energy consumption over the backhaul links. In this paper, two scenarios are considered, where caching is performed either at a small base station, or directly at the user terminals, which communicate using Device-to-Device (D2D) communications. In both scenarios, joint design of the transmission and caching policies is studied when the user demands are known in advance. This joint design offers two different caching gains, namely, the pre-downloading and local caching gains. It is shown that the finite cache capacity limits the attainable gains, and creates an inherent tradeoff between the two types of gains. In this context, a continuous time optimization problem is formulated to determine the optimal transmission and caching policies that minimize a generic cost function, such as energy, bandwidth, or throughput. The jointly optimal solution is obtained by demonstrating that caching files at a constant rate is optimal, which allows reformulation of the problem as a finite-dimensional convex program. The numerical results show that the proposed joint transmission and caching policy dramatically reduces the total cost, which is particularised to the total energy consumption at the Macro Base Station (MBS), as well as to the total economical cost for the service provider, when users demand economical incentives for delivering content to other users over the D2D links

Los modos de representación gráfico lineal y cartesiano en la comprensión del concepto de sucesión numérica en estudiantes de segundo ciclo enseñanza secundaria obligatoria

Esta investigación forma parte de un trabajo cuyo objetivo es la compresión del concepto de sucesión numérica en los estudiantes de secundaria. El enfoque proporcionado por distintos investigadores en relación a los modos de representación y las aportaciones de Piaget y García en relación al desarrollo de un esquema a través de los niveles intra, inter y trans, nos proporciona información sobre el desarrollo de la comprensión del concepto de sucesión numérica a través del uso de los modos de representación gráficos, lineal y cartesiano, por parte de los estudiantes en la resolución de una tarea

Las progresiones como indicador de la comprensión del concepto de sucesión numérica en alumnos de segundo ciclo de enseñanza secundaria obligatoria

Este trabajo forma parte de una investigación que aborda la compresión del concepto de sucesión numérica en los estudiantes de secundaria. La perspectiva proporcionada por la obra de Piaget y García en relación con el desarrollo de un esquema a través de varios niveles (intra, inter y trans), nos proporciona la prueba empírica de cómo el uso de las progresiones por parte de los estudiantes en la resolución de una tarea, proporciona información del desarrollo de la comprensión. Este uso nos permite profundizar sobre los niveles en el desarrollo del concepto sucesión numérica

Science, Technology, and Innovation Governance for Social Inclusion and Sustainable Development in Latin America

The introduction of the concept of governance in Latin America belongs to the neoliberal policies of privatization that tried to trace and assure that public funds, especially international loans, can overcome several corruption problems and the lag in the bargaining between public and private actors. The idea that transparency and accountability in the private actors that receive contracts from the States with the slogan of competitiveness reach bankruptcy. In this framework, studies in science, technology, and innovation (STI) began to interest in governance as a way to explain how policy and research networks create space, mechanisms, and instruments to negotiate and steer policies and actions and create a better future. The scientific challenges to solve complex problems need several actors and fields beyond traditional ministries and bureaucratic governments jurisdictions. Then, governance arises to understand the coordination between several stakeholders that are able to collaborate and develop systems to achieve common goals. This chapter introduces the book that covers the research shared in the congress “Governance of science, technology, and innovation for inclusive and sustainable development in Latin America” organized by the Network on Governance and Management of Science, Technology, and Innovation—(Red GCTI) with a critical point of view. The main contribution is to show the topics, approaches, controversies, trends, and challenges in the Latin American research of STI governance for social inclusion and sustainability