Time-Reversal Massive Multipath Effect and Bandwidth Heterogeneity

The proliferation of new mobile communication devices, such as smartphones and tablets, has led to an exponential growth in network traffic. The demand for supporting the fast-growing consumer data rates urges the wireless service providers and researchers to seek a new efficient radio access technology, which is the so-called 5G technology, beyond what current 4G LTE can provide. On the other hand, ubiquitous RFID tags, sensors, actuators, mobile phones and etc. cut across many areas of modern-day living, which offers the ability to measure, infer and understand the environmental indicators. The proliferation of these devices creates the term of the Internet of Things (IoT). For the researchers and engineers in the field of wireless communication, the exploration of new effective techniques to support 5G communication and the IoT becomes an urgent task, which not only leads to fruitful research but also enhance the quality of our everyday life. Massive MIMO, which has shown the great potential in improving the achievable rate with a very large number of antennas, has become a popular candidate. However, the requirement of deploying a large number of antennas at the base station may not be feasible in indoor scenarios. Does there exist a good alternative that can achieve similar system performance to massive MIMO for indoor environment? In this dissertation, we address this question by proposing the time-reversal technique as a counterpart of massive MIMO in indoor scenario with the massive multipath effect. It is well known that radio signals will experience many multipaths due to the reflection from various scatters, especially in indoor environments. The traditional TR waveform is able to create a focusing effect at the intended receiver with very low transmitter complexity in a severe multipath channel. TR's focusing effect is in essence a spatial-temporal resonance effect that brings all the multipaths to arrive at a particular location at a specific moment. We show that by using time-reversal signal processing, with a sufficiently large bandwidth, one can harvest the massive multipaths naturally existing in a rich-scattering environment to form a large number of virtual antennas and achieve the desired massive multipath effect with a single antenna. Further, we explore the optimal bandwidth for TR system to achieve maximal spectral efficiency. Through evaluating the spectral efficiency, the optimal bandwidth for TR system is found determined by the system parameters, e.g., the number of users and backoff factor, instead of the waveform types. Moreover, we investigate the tradeoff between complexity and performance through establishing a generalized relationship between the system performance and waveform quantization in a practical communication system. It is shown that a 4-bit quantized waveforms can be used to achieve the similar bit-error-rate compared to the TR system with perfect precision waveforms. Besides 5G technology, Internet of Things (IoT) is another terminology that recently attracts more and more attention from both academia and industry. In the second part of this dissertation, the heterogeneity issue within the IoT is explored. One of the significant heterogeneity considering the massive amount of devices in the IoT is the device heterogeneity, i.e., the heterogeneous bandwidths and associated radio-frequency (RF) components. The traditional middleware techniques result in the fragmentation of the whole network, hampering the objects interoperability and slowing down the development of a unified reference model for the IoT. We propose a novel TR-based heterogeneous system, which can address the bandwidth heterogeneity and maintain the benefit of TR at the same time. The increase of complexity in the proposed system lies in the digital processing at the access point (AP), instead of at the devices' ends, which can be easily handled with more powerful digital signal processor (DSP). Meanwhile, the complexity of the terminal devices stays low and therefore satisfies the low-complexity and scalability requirement of the IoT. Since there is no middleware in the proposed scheme and the additional physical layer complexity concentrates on the AP side, the proposed heterogeneous TR system better satisfies the low-complexity and energy-efficiency requirement for the terminal devices (TDs) compared with the middleware approach.

Análisis de los impactos del uso del teléfono móvil en los estilos de vida [ocio y tiempo libre, relaciones sociales, y conductas sedentarias] de los adolescentes en enseñanza secundaria obligatoria de la Comunidad Autónoma de Aragón, España

La presente investigación tuvo como objetivo analizar los impactos del uso del teléfono móvil en los estilos de vida (ocio y tiempo libre, relaciones sociales, y conductas sedentarias) de los adolescentes en enseñanza secundaria obligatoria de la comunidad autónoma de Aragón (España). Comenzamos por revisar conceptualizaciones, revisamos acerca del bienestar y de los hábitos de vida de los adolescentes, el teléfono móvil y sus implicancias para la salud y estilos de vida, sus usos y representationes. Metodológicamente, se trata de un estudio descriptivo y cuantitativo. Realizamos un análisis exploratorio de los datos, y complementariamente testeamos la relación entre variables. En conclusión, podemos afirmar que los adolescentes en Aragón: Tienen una visión positiva de su salud; Entre las conductas sedentarias asociadas a las pantallas, prevalece el uso del teléfono móvil en el fin de semana; La seguridad es la función referencial (valor simbólico) más valorizada del teléfono móvil; Poder comunicarse con los amigos, es la principal razón para querer tener su primer teléfono móvil; Enviar o recibir mensajes de los amigos/as, es la función comunicativa (valor instrumental) más valorizada del teléfono móvil; Escuchar música o la radio, es el mayor uso de la función lúdico-expresiva-organizativa (valor instrumental) del teléfono móvil.

Características del Ciberbullying en los estudiantes de la Unidad Educativa César Dávila Andrade. Cuenca. Ecuador. 2013

Antecedentes: En la actualidad los adolescentes se desenvuelven a la perfección en el uso de la tecnología de la información y comunicación. El internet y la telefonía móvil se han constituido en instrumentos de primer orden para su formación, desarrollo, socialización y diversión; sin embargo, en ocasiones puede que no hagan un buen uso de la tecnología y más bien algunos adolescentes, con una personalidad agresora, se valen de estos medios para perturbar a sus compañeros y realizar nuevas modalidades de acoso escolar. Objetivo: Determinar las características de ciberbullying en los estudiantes de la Unidad Educativa “César Dávila Andrade”. Metodología: Se realizó un estudio cuantitativo descriptivo, el universo estuvo conformado por todos los estudiantes del ciclo básico, a quiénes se les aplicó un formulario modificado del Protocolo de Actuación Escolar ante Ciberbullying de EMICI (Equipo Multidisciplinar de Investigación sobre Ciberbullying); para la tabulación y procesamiento de la información se utilizó el programa SPSS versión 15; como medidas estadísticas se emplearon: frecuencias, medias, porcentajes; para la presentación de los datos se elaboraron tablas de acuerdo a los objetivos y, para el análisis de la información se utilizó estadística descriptiva. Resultados: El ciberbullying se presenta en el 11% de los alumnos: 9.5% en el sexo masculino y 15% en el sexo femenino; el medio más utilizado para acosar son las redes sociales 52%, seguido de mensajes por celular 21.7%; dentro de las consecuencias académicas el 34.2% tiene deseos de no ir al colegio, el 47.4% ha bajado sus calificaciones; en relación a problemas familiares el 42% tiene problemas con sus padres y hermanos y dentro de los problemas psicológicos cerca del 40% se siente deprimido y, la tercera parte de las víctimas de ciberbullying declaran que “creen que es mejor desaparecer”. Conclusiones: Se detectaron casos de ciberbullying con predominio en el sexo femenino evidenciándose un componente de género

Identification technologies to support Alzheimer contexts

Alzheimer's disease makes great demands on care by assistants, due to the fact that they cannot distract their attention from patients while they are at the same time managing records. For that reason, technologies to complement this process need to be adapted. In this work we present a proposal to adapt identification technologies: Radiofrequency Identification (RFID) and Near Field Communications (NFC), focusing especially on the last one. We fuse both technologies and apply them to an Alzheimer's day center. Patients are tagged with two kinds of labels: 13.56Mhz.Mifare for NFC and UHF for RFID. With the first one we tag the context, which means patients, devices (displays, exercise books, etc) and places. With a simple interaction, which involves touching tags with mobile phones, it is possible to manage the information easily. Moreover, with RFID, we localize each patient by the simple act of their passing by an antenna placed in the doors.

mHealth-based Methods for Neuromotor Assessment and Rehabilitation

Recent years observed massive growth in wearable technology, everything can be smart: phones, watches, glasses, shirts, etc. These technologies are prevalent in various fields: from wellness/sports/fitness to the healthcare domain. The spread of this phenomenon led the World-Health-Organization to define the term 'mHealth' as "medical and public health practice supported by mobile devices, such as mobile phones, patient monitoring devices, personal digital assistants, and other wireless devices". Furthermore, mHealth solutions are suitable to perform real-time wearable Biofeedback (BF) systems: sensors in the body area network connected to a processing unit (smartphone) and a feedback device (loudspeaker) to measure human functions and return them to the user as (bio)feedback signal. During the COVID-19 pandemic, this transformation of the healthcare system has been dramatically accelerated by new clinical demands, including the need to prevent hospital surges and to assure continuity of clinical care services, allowing pervasive healthcare. Never as of today, we can say that the integration of mHealth technologies will be the basis of this new era of clinical practice. In this scenario, this PhD thesis's primary goal is to investigate new and innovative mHealth solutions for the Assessment and Rehabilitation of different neuromotor functions and diseases. For the clinical assessment, there is the need to overcome the limitations of subjective clinical scales. Creating new pervasive and self-administrable mHealth solutions, this thesis investigates the possibility of employing innovative systems for objective clinical evaluation. For rehabilitation, we explored the clinical feasibility and effectiveness of mHealth systems. In particular, we developed innovative mHealth solutions with BF capability to allow tailored rehabilitation. The main goal that a mHealth-system should have is improving the person's quality of life, increasing or maintaining his autonomy and independence. To this end, inclusive design principles might be crucial, next to the technical and technological ones, to improve mHealth-systems usability.

Characterisation of noisy speech channels in 2G and 3G mobile networks

As the wireless cellular market reaches competitive levels never seen before, network operators need to focus on maintaining Quality of Service (QoS) a main priority if they wish to attract new subscribers while keeping existing customers satisfied. Speech Quality as perceived by the end user is one major example of a characteristic in constant need of maintenance and improvement. It is in this topic that this Master Thesis project fits in. Making use of an intrusive method of speech quality evaluation, as a means to further study and characterize the performance of speech codecs in second-generation (2G) and third-generation (3G) technologies. Trying to find further correlation between codecs with similar bit rates, along with the exploration of certain transmission parameters which may aid in the assessment of speech quality. Due to some limitations concerning the audio analyzer equipment that was to be employed, a different system for recording the test samples was sought out. Although the new designed system is not standard, after extensive testing and optimization of the system's parameters, final results were found reliable and satisfactory. Tests include a set of high and low bit rate codecs for both 2G and 3G, where values were compared and analysed, leading to the outcome that 3G speech codecs perform better, under the approximately same conditions, when compared with 2G. Reinforcing the idea that 3G is, with no doubt, the best choice if the costumer looks for the best possible listening speech quality. Regarding the transmission parameters chosen for the experiment, the Receiver Quality (RxQual) and Received Energy per Chip to the Power Density Ratio (Ec/N0), these were subject to speech quality correlation tests. Final results of RxQual were compared to those of prior studies from different researchers and, are considered to be of important relevance. Leading to the confirmation of RxQual as a reliable indicator of speech quality. As for Ec/N0, it is not possible to state it as a speech quality indicator however, it shows clear thresholds for which the MOS values decrease significantly. The studied transmission parameters show that they can be used not only for network management purposes but, at the same time, give an expected idea to the communications engineer (or technician) of the end-to-end speech quality consequences. With the conclusion of the work new ideas for future studies come to mind. Considering that the fourth-generation (4G) cellular technologies are now beginning to take an important place in the global market, as the first all-IP network structure, it seems of great relevance that 4G speech quality should be subject of evaluation. Comparing it to 3G, not only in narrowband but also adding wideband scenarios with the most recent standard objective method of speech quality assessment, POLQA. Also, new data found on Ec/N0 tests, justifies further research studies with the intention of validating the assumptions made in this work.

Internationalization strategy: HOLOS Mobile - Angola

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

Knowledge, networks of cities and growth in regional urban systems

The objective of this paper is to measure the impact of different kinds of knowledge and external economies on urban growth in an intraregional context. The main hypothesis is that knowledge leads to growth, and that this knowledge is related to the existence of agglomeration and network externalities in cities. We develop a three-tage methodology: first, we measure the amount and growth of knowledge in cities using the OCDE (2003) classification and employment data; second, we identify the spatial structure of the area of analysis (networks of cities); third, we combine the Glaeser - Henderson - De Lucio models with spatial econometric specifications in order to contrast the existence of spatially static (agglomeration) and spatially dynamic (network) external economies in an urban growth model. Results suggest that higher growth rates are associated to higher levels of technology and knowledge. The growth of the different kinds of knowledge is related to local and spatial factors (agglomeration and network externalities) and each knowledge intensity shows a particular response to these factors. These results have implications for policy design, since we can forecast and intervene on local knowledge development paths.

A diagram of public spaces within urban landscape as a strategy for sustainable urban planning in Chinese cities

Destruction of historical urban fabric in many Chinese cities and towns, without the possibility of its recovery as an urban asset, leads us to consider alternative strategies and criteria for formulating new urban projects, using creative urban planning instruments and strategies to provide a sense of place and identity to the urban landscape. The challenge is to set up an urban structure that constitutes a spatial reference system, a structure consisting of a set of urban landmarks that construct a system of related public spaces, endowed with collective significance and identity. Such a network could include a wide variety of urban typologies and natural elements. An important result of this strategy would be the recovery of the social and cultural values attached to the natural landscape in Chinese civilization. Hangzhou city will be analyzed as a case study

Cities, skills, and regional change

One approach to urban areas emphasizes the existence of certain immutable relationships, such as Zipf's or Gibrat's Law. An alternative view is that urban changereflects individual responses to changing tastes or technologies. This paper examinesalmost 200 years of regional change in the U.S. and finds that few, if any, growth relationships remain constant, including Gibrat's Law. Education does a reasonable jobof explaining urban resilience in recent decades, but does not seem to predict countygrowth a century ago. After reviewing this evidence, we present and estimate a simple model of regional change, where education increases the level of entrepreneurship.Human capital spillovers occur at the city level because skilled workers produce moreproduct varieties and thereby increase labor demand. We find that skills are associatedwith growth in productivity or entrepreneurship, not with growth in quality of life, atleast outside of the West. We also find that skills seem to have depressed housing supplygrowth in the West, but not in other regions, which supports the view that educatedresidents in that region have fought for tougher land-use controls. We also present evidence that skills have had a disproportionately large impact on unemployment duringthe current recession.

Managing Packet Data (Sessions) in 3G Mobile Networks

Tällä hetkellä kolmannen sukupolven matkapuhelinjärjestelmät ovat siirtyneet kaupalliseen vaiheeseen. Universal Mobile Telecommunication System (UMTS) on eräs kolmannen sukupolven matkapuhelinjärjestelmä, jota tullaan käyttämään Euroopassa. Diplomityön päämääränä on tutkia, kuinka pakettivälitteistä tiedonsiirtoa hallitaan UMTS - verkoissa. Diplomityö antaa yleiskuvan toisen sukupolven matkapuhelinjärjestelmien datapalveluiden kehityksestä kolmannen sukupolven nopeisiin matkapuhelinjärjestelmiin. Pakettivälitteisen verkon verkkoarkkitehtuuri on esitetty sekä sen, diplomityön kannalta, tärkeimpien osien toiminnallisuus on selvitetty. Myös pakettipohjaisten datayhteyksien eli istuntojen muodostaminen ja vapauttaminen sekä aktiivisen yhteyden ominaisuuksien muokkaaminen on esitetty tässä diplomityössä. Yhteydenhallintaprotokolla, Session Management (SM), on yksi protokolla, joka osallistuu pakettidatayhteyden hallintaan. SM -protokolla on käsitelty työssä yksityiskohtaisesti. SM -protokollan SDL toteutus on esitetty diplomityön käytännönosassa

Russian mobile telecommunications market: players and trends

Objective of this work was to clarify the competitive situation of Russian mobile telecommunications market: who are the main players, are there many regional operators, what is the possibility of new entrants and how intensive is the competition. In the beginning the history of Russian mobile telecommunications sector is described. In the next chapter environmental factors of the market are examined with the help of PESTEL analysis. After that, players of the market are introduced to ease the following of next chapters. The main theory for this work was industry analysis of five competitive forces by Michael Porter, which is presented before the theory related industry analysis of Russian mobile telecommunications industry. Research for the industry analysis is mainly based on up-to-date articles describing Russian market. As a result of the industry analysis, competitive situation of Russian mobile telecommunications industry and the future prospects are described with the help of factors coming from the PESTEL-analysis. Finally development and future prospects for Russian 3G are reported. As a result of this work, it can be said that Russian mobile telecommunications market is not likely to maintain the growth of previous years, because the market is near saturation. According to passive SIM-cards it has already received saturated. The saturation will also make the market share game between operators more volatile. The market is dominated by three national operators that covered 88% of the income in the first half of 2007. In addition to these three, there are also several regional operators. Structure of the market is likely to consolidate.

Brazilian, Chinese, and Indian exports: is the regional market really a source of learning?

In some Latin American countries the exporting activity starts at a regional level, with producers only later venturing into more competitive markets. The implicit risk is that a country might never progress from the regional stage to a more global market. This article compares the experiences of Brazil, China and India. It is shown that Brazil relied on the regional market far more intensely than these Asian countries. There were clear gains accruing to China and India for having exploited more sophisticated markets from the very beginning of their export drive.