Modulation-mode assignment in SVD-assisted multiuser MIMO-OFDM systems

In order to comply with the demand on increasing available data rates in particular in wireless technologies, systems with multiple transmit and receive antennas, also called MIMO (multiple-input multiple-output) systems, have become indispensable for future generations of wireless systems. Due to the strongly increasing demand in high-data rate transmission systems, frequency non-selective MIMO links have reached a state of maturity and frequency selective MIMO links are in the focus of interest. In this field, the combination of MIMO transmission and OFDM (orthogonal frequency division multiplexing) can be considered as an essential part of fulfilling the requirements of future generations of wireless systems. However, single-user scenarios have reached a state of maturity. By contrast multiple users’ scenarios require substantial further research, where in comparison to ZF (zero-forcing) multiuser transmission techniques, the individual user’s channel characteristics are taken into consideration in this contribution. The performed joint optimization of the number of activated MIMO layers and the number of transmitted bits per subcarrier along with the appropriate allocation of the transmit power shows that not necessarily all user-specific MIMO layers per subcarrier have to be activated in order to minimize the overall BER under the constraint of a given fixed data throughput.

Magnetization reversal assisted by half antivortex states in nanostructured circular cobalt disks

The half antivortex, a fundamental topological structure which determines magnetization reversal of submicron magnetic devices with domain walls, has been suggested also to play a crucial role in spin torque induced vortex core reversal in circular disks. Here, we report on magnetization reversal in circular disks with nanoholes through consecutive metastable states with half antivortices. In-plane anisotropic magnetoresistance and broadband susceptibility measurements accompanied by micromagnetic simulations reveal that cobalt (Co) disks with two and three linearly arranged nanoholes directed at 45° and 135° with respect to the external magnetic field show reproducible step-like changes in the anisotropic magnetoresistance and magnetic permeability due to transitions between different intermediate states mediated by vortices and half antivortices confined to the dot nanoholes and edges, respectively. Our findings are relevant for the development of multi-hole based spintronic and magnetic memory devices.

Plataforma MALL (Mobile-Assisted Language Learning) para el aprendizaje y desarrollo del conocimiento del idioma, particularizado en el Inglés

El creciente uso de las Tecnologías de la Información y las Comunicaciones en el ámbito educativo ha hecho posible que existan nuevas formas de enseñanza que facilitan el aprendizaje y la mejora de éste. Una de las ramas educativas que más influenciada se ha visto por esto es la de los idiomas, debido en gran parte a la necesidad global de aprender nuevas lenguas y mejorar sus conocimientos de ellas. Entre todos los idiomas que la gente desea aprender destaca uno por encima de todos, el inglés. Esto viene dado no solo por la presencia de éste a nivel mundial, sino por la gran repercusión en el ámbito educativo, comenzando a ser un requisito indispensable en la realización de estudios superiores. El presente proyecto Fin de Grado pretende contribuir a la mejora del conocimiento del inglés para estudiantes que no han alcanzado un nivel B2 de éste. En éste se desarrolla una plataforma educativa accesible por el mayor número de alumnos posibles, no solo solo a través de ordenadores personales, sino principalmente a través de dispositivos móviles tales como smartphones y tablets. Para que fuese posible una mayor utilización de esta por parte de los estudiantes era necesario la creación de una aplicación que pudiese ser utilizada desde cualquier dispositivo sin importar el sistema operativo empleado. Dicha plataforma educativa está formada por un juego de preguntas en la que los estudiantes deberán contestar correctamente para obtener una puntuación final con la que accederán a una clasificación con el resto de miembros de dicha plataforma. Con éste sistema de puntos se pretende dar una componente de gamificación al juego para motivar a los estudiantes a que sigan compitiendo y realizando test de preguntas. Además a dicha plataforma podrán acceder los profesores administradores de ella para monitorizar y ver resultados de los estudiantes participantes. ABSTRACT. The growing use of Information and Communication Technologies in the educational field has made possible for new teaching ways to exist, thus making learning easier and better. One of the more influenced educational branches by this fact is languages, largely due to a global need to learn them and improve knowledge. Among all the languages that people wish to learn, one stands out above them, English. It is given, not only by its worldwide presence, but by its big scholar repercussion; that English is an essential requirement for higher education. This final degree project aims to improve the english level for those who have a hard time doing it. This project develops an educational accesible platform to the greatest number of students, not only through personal computers, but mainly through mobile devices like smartphones or tablets. To make a great use of it by students possible, it was necessary an application which could be used from any device regardless of the operative system. This teaching platform is formed by a quiz game in which students must answer correctly in order to get a final score which will place them in a ranking composed by other platform members. With this score system it is intended to give a gamification component in order to motivate students to keep playing and answering question tests. Also, in this platform, administration teachers will be able to monitor the students and watch their results.