Análise e projeto de superfícies seletivas em frequência multibanda e/ou banda larga

Frequency selective surfaces (Frequency Selective Surface - FSS) are often used in various applications in telecommunications. Some of these applications may require that these structures have response with multiple resonance bands. Other applications require that the FSS response have large frequency range, to meet the necessary requirements. FSS to design with these features there are numerous techniques cited in the scientific literature. Thus, the purpose of this paper is to examine some common techniques such as: Overlap of FSS; Elements combined; Elements Elements convolucionados and fractals. And designing multiband FSS and / or broadband selecting simple ways in terms of construction and occupy the smallest possible space, aiming at practical applications. Given these requirements, three projects FSS were performed: a technology applied to IEEE 802.11 a/b/g/n and two projects for application in UWB. In project development, commercial software Ansoft DesignerTM and experimental results were satisfactory was used

Extensões ao Projeto LVWNet: mobilidade, interação com equipamentos reais, comunicação direta, e registro dinâmico de nós

Due to the constantly increasing use of wireless networks in domestic, business and industrial environments, new challenges have emerged. The prototyping of new protocols in these environments is typically restricted to simulation environments, where there is the need of double implementation, one in the simulation environment where an initial proof of concept is performed and the other one in a real environment. Also, if real environments are used, it is not trivial to create a testbed for high density wireless networks given the need to use various real equipment as well as attenuators and power reducers to try to reduce the physical space required to create these laboratories. In this context, LVWNet (Linux Virtual Wireless Network) project was originally designed to create completely virtual testbeds for IEEE 802.11 networks on the Linux operating system. This paper aims to extend the current project LVWNet, adding to it the features like the ability to interact with real wireless hardware, provides a initial mobility ability using the positioning of the nodes in a space coordinates environment based on meters, with loss calculations due to attenuation in free space, enables some scalability increase by creating an own protocol that allows the communication between nodes without an intermediate host and dynamic registration of nodes, allowing new nodes to be inserted into in already in operation network

Predição de qualidade de experiência para internet do futuro em arquiteturas heterogêneas de redes sem fio móveis

As Redes da Próxima Geração consistem no desenvolvimento de arquiteturas que viabilizem a continuidade de serviços que proporcionem sempre a melhor conectividade (Always Best Connectivity - ABC) aos usuários móveis com suporte adequado à Qualidade de Experiência (QoE) para aplicações multimídia de alta definição, nesse novo contexto as arquiteturas têm perspectiva orientada a serviços e não a protocolos. Esta tese apresenta uma arquitetura para redes da próxima geração capaz de fornecer acesso heterogêneo sem fio e handover vertical transparente para as aplicações multimídia. A tese considera diferentes tecnologias sem fio e também adota o padrão IEEE 802.21 (Media Independent Handover – MIH) para auxiliar na integração e gerenciamento das redes heterogêneas sem fio. As tecnologias que a arquitetura possui são: IEEE 802.11 (popularmente denominada de WiFi), IEEE 802.16 (popularmente denominada de WiMAX) e LTE (popularmente denominada de redes 4G). O objetivo é que arquitetura tenha a capacidade de escolher entre as alternativas disponíveis a melhor conexão para o momento. A arquitetura proposta apresenta mecanismos de predição de Qualidade de Experiência (Quality of Experience - QoE) que será o parâmetro decisivo para a realização ou não do handover para uma nova rede. A predição para determinar se haverá ou não mudança de conectividade será feita com o uso da inteligência computacional de Redes Neurais Artificiais. Além disso a arquitetura também apresenta um mecanismo de descarte seletivo de pacotes especifico para aplicações multimídia. A proposta é avaliada via simulação utilizando-se o ns-2 (Network Simulator) e os resultados de desempenho são apresentados através das métricas de QoS, de QoE e também visualmente através da exibição de frames dos vídeos transmitidos na arquitetura.

O emprego de técnicas de qualidade de serviço em redes sem fio aplicado à automação predial

Pós-graduação em Engenharia Elétrica - FEIS

Caracterización y modelado de prestaciones en redes inalámbricas para aplicaciones con calidad de servicio

Programa de doctorado: Tecnologías de las Telecomunicaciones (bienio 98/00). La fecha de publicación es la fecha de lectura

Sistemi OFDM: prestazioni di livello fisico

I primi studi su Orthogonal Frequency Division Multiplexing (OFDM) sono stati fatti fin dal 1960, ma negli ultimi anni la modulazione OFDM è emersa come una tecnica di modulazione chiave commerciale per i sistemi di comunicazione ad alta velocità. La ragione principale di questo crescente interesse è dovuto alla sua capacità di fornire dati ad alta velocità impiegando sistemi con complessità bassa e contrastando l'interferenza intersimbolo (ISI) e quella intercanale (ICI). Per questo motivo la modulazione OFDM è stata adottata da diversi sistemi digitali wireline e wireless standard, come Digital Audio Broadcasting (DAB), Asymmetric Digital Subscriber Line (ADSL), Wireless Local Area Network (IEEE 802.11 a,g,n) oppure per WiMAX e LTE.

Performance Analysis and Comparison between Legacy-PSM and U-APSD

This paper evaluates the performance of the most popular power saving mechanisms defined in the IEEE 802.11 standard, namely the Power Save Mode (Legacy-PSM) and the Unscheduled Automatic Power Save Delivery (U-APSD). The assessment comprises a detailed study concerning energy efficiency and capability to guarantee the required Quality of Service (QoS) for a certain application. The results, obtained in the OMNeT++ simulator, showed that U-APSD is more energy efficient than Legacy-PSM without compromising the end-to- end delay. Both U-APSD and Legacy-PSM revealed capability to guarantee the application QoS requirements in all the studied scenarios. However, unlike U-APSD, when Legacy-PSM is used in the presence of QoS demanding applications, all the stations connected to the network through the same access point will consume noticeable additional energy.

Towards End-User Driven Power Saving Control in Android devices

Abstract. During the last decade mobile communications increasingly became part of people's daily routine. Such usage raises new challenges regarding devices' battery lifetime management when using most popular wireless access technologies, such as IEEE 802.11. This paper investigates the energy/delay trade-off of using an end-user driven power saving approach, when compared with the standard IEEE 802.11 power saving algorithms. The assessment was conducted in a real testbed using an Android mobile phone and high-precision energy measurement hardware. The results show clear energy benefits of employing user-driven power saving techniques, when compared with other standard approaches.

Integración Wi-Fi en un proyecto ICT

La instalación de Infraestructuras Comunes de Telecomunicación (IICCTT) en el interior de las edificaciones para el acceso a los servicios de telecomunicación facilitó la incorporación a las viviendas de las nuevas tecnologías de forma económica y transparente para los usuarios. Actualmente, todos los edificios de nueva construcción deben presentar un proyecto ICT firmado por un Ingeniero Técnico de Telecomunicación de la especialidad correspondiente o un Ingeniero de Telecomunicación. La legislación que las regula afecta a todo tipo de viviendas con independencia del poder adquisitivo del comprador, y contribuye de manera decisiva a que disminuyan a corto y medio plazo las desigualdades sociales en lo relativo al acceso a servicios de telecomunicación tales como telefonía, Internet, telecomunicación por cable, radiodifusión sonora y televisión analógica, digital, terrenal o por satélite, etc.. Desde 1997, el Colegio Oficial de Ingenieros de Telecomunicación junto con otras organizaciones públicas y privadas ha participado en la elaboración de la normativa aplicable a las Infraestructuras Comunes de Telecomunicación, dando lugar al actual decreto, el Real Decreto 346/2011, de 11 de Marzo. El propósito general de este proyecto es diseñar una red Wi-Fi a partir de las canalizaciones e instalaciones del proyecto ICT de un conjunto de viviendas unifamiliares, para que todas ellas dispongan de conexión a internet de forma inalámbrica. Para llevar a cabo este diseño, se ha realizado un estudio de las características del estándar IEEE 802.11, conocido como Wi-Fi, analizando las posibilidades de comunicación inalámbrica que ofrece, así como las limitaciones que presenta en la actualidad. Se ha analizado el proyecto ICT del conjunto de viviendas, estudiando la viabilidad de utilizar sus instalaciones para implementar la red Wi-Fi, añadiendo tanto las canalizaciones como los dispositivos comerciales necesarios para llevar a cabo dicha implementación. Además, se ha estudiado la posibilidad de integrar la red Wi-Fi utilizando el cableado de televisión de la propia ICT. Por último, se ha estudiado la gran importancia que al Hogar Digital se da en el Real Decreto 346/2011, de 11 de marzo, por el que se aprueba el Reglamento regulador de las Infraestructuras Comunes de Telecomunicaciones para el acceso a los servicios de telecomunicación en el interior de las edificaciones, presentando los aspectos fundamentales que se persiguen con la domotización de la vivienda como mejora de vida de sus habitantes. Abstract The installation of Telecommunications Common Infrastructures (TCIs, in Spanish Infraestructuras Comunes de Telecomunicación –IICCTT-) in the buildings, in order to gain access to telecommunications services, facilitated the incorporation into the houses of new technologies in an economical and transparent way for users. Nowadays, every new construction building must have a TCI project signed by a Telecommunications Engineer or a Technical Telecommunications Engineer with the appropriate specialization. The legislation that regulates TCIs affects every kind of houses, independently of the buyer´s purchasing power, and contributes decisively to decrease in short and medium terms the social inequalities concerning the access to the telecommunication services, such as telephony, Internet, wired telecommunications, audible broadcasting and digital, analogical, land, satellite television, etc.. Since 1997, the Telecommunications Engineer Official College, together with other public and private organizations, has been elaborating the regulations for the TCIs, giving rise to the current decree, the Royal Decree 346/2011, of 11th of March. The general purpose of this project is to design a Wi-Fi network based on the canalizations and installations of the TCI project of a housing development, in such a way that every house is provided with a wireless connection to the Internet. In order to carry out this design, the characteristics of the standard IEEE 802.11, known as Wi-Fi, have been studied, analyzing the wireless-communication possibilities that it offers, as well as the constraints that it presents currently. The TCI project has been analyzed, studying the feasibility of using its installations to implement the Wi-Fi network, adding the canalizations and commercial devices required to execute the aforementioned implementation. Besides, the possibility of integrating the Wi-Fi network using the television wires of the TCI project has been investigated. Finally, it has been studied the great importance that has been given to Digital Home in the Royal Decree 346/2011, of 11th of March, that approves the regulatory Regulations of Telecommunications Common Infrastructures for the access to telecommunications services inside the buildings, presenting the essential aspects that are pursued with the house domotization as a way to improve the quality of life of its inhabitants.

Supporting eradication of maternal child malnutrition in developing countries: a case from Nicaragua scenario.

World Health Organization actively stresses the importance of health, nutrition and well-being of the mother to foster children development. This issue is critical in the rural areas of developing countries where monitoring of health status of children is hardly performed since population suffers from a lack of access to health care. The aim of this research is to design, implement and deploy an e-health information and communication system to support health care in 26 rural communities of Cusmapa, Nicaragua. The final solution consists of an hybrid WiMAX/WiFi architecture that provides good quality communications through VoIP taking advantage of low cost WiFi mobile devices. Thus, a WiMAX base station was installed in the health center to provide a radio link with the rural health post "El Carrizo" sited 7,4 km. in line of sight. This service makes possible personal broadband voice and data communication facilities with the health center based on WiFi enabled devices such as laptops and cellular phones without communications cost. A free software PBX was installed at "San José de Cusmapa" health care site to enable communications for physicians, nurses and a technician through mobile telephones with IEEE 802.11 b/g protocol and SIP provided by the project. Additionally, the rural health post staff (midwives, brigade) received two mobile phones with these same features. In a complementary way, the deployed health information system is ready to analyze the distribution of maternal-child population at risk and the distribution of diseases on a geographical baseline. The system works with four information layers: fertile women, children, people with disabilities and diseases. Thus, authorized staff can obtain reports about prenatal monitoring tasks, status of the communities, malnutrition, and immunization control. Data need to be updated by health care staff in order to timely detect the source of problem to implement measures addressed to alleviate and improve health status population permanently. Ongoing research is focused on a mobile platform that collects and automatically updates in the information system, the height and weight of the children locally gathered in the remote communities. This research is being granted by the program Millennium Rural Communities of the Technical University of Madrid.

An evaluation of TCP over wired-to-wireless networks

To exploit the popularity of TCP as still the dominant sender and protocol of choice for transporting data reliably across the heterogeneous Internet, this thesis explores end-to-end performance issues and behaviours of TCP senders when transferring data to wireless end-users. The theme throughout is on end-users located specifically within 802.11 WLANs at the edges of the Internet, a largely untapped area of work. To exploit the interests of researchers wanting to study the performance of TCP accurately over heterogeneous conditions, this thesis proposes a flexible wired-to-wireless experimental testbed that better reflects conditions in the real-world. To exploit the transparent functionalities between TCP in the wired domain and the IEEE 802.11 WLAN protocols, this thesis proposes a more accurate methodology for gauging the transmission and error characteristics of real-world 802.11 WLANs. It also aims to correlate any findings with the functionality of fixed TCP senders. To exploit the popularity of Linux as a popular operating system for many of the Internet’s data servers, this thesis studies and evaluates various sender-side TCP congestion control implementations within the recent Linux v2.6. A selection of the implementations are put under systematic testing using real-world wired-to-wireless conditions in order to screen and present a viable candidate/s for further development and usage in the modern-day heterogeneous Internet. Overall, this thesis comprises a set of systematic evaluations of TCP senders over 802.11 WLANs, incorporating measurements in the form of simulations, emulations, and through the use of a real-world-like experimental testbed. The goal of the work is to ensure that all aspects concerned are comprehensively investigated in order to establish rules that can help to decide under which circumstances the deployment of TCP is optimal i.e. a set of paradigms for advancing the state-of-the-art in data transport across the Internet.

Directionality based preventive link maintenance scheme for mobile ad hoc networks

The purpose of this study was to design a preventive scheme using directional antennas to improve the performance of mobile ad hoc networks. In this dissertation, a novel Directionality based Preventive Link Maintenance (DPLM) Scheme is proposed to characterize the performance gain [JaY06a, JaY06b, JCY06] by extending the life of link. In order to maintain the link and take preventive action, signal strength of data packets is measured. Moreover, location information or angle of arrival information is collected during communication and saved in the table. When measured signal strength is below orientation threshold , an orientation warning is generated towards the previous hop node. Once orientation warning is received by previous hop (adjacent) node, it verifies the correctness of orientation warning with few hello pings and initiates high quality directional link (a link above the threshold) and immediately switches to it, avoiding a link break altogether. The location information is utilized to create a directional link by orienting neighboring nodes antennas towards each other. We call this operation an orientation handoff, which is similar to soft-handoff in cellular networks. ^ Signal strength is the indicating factor, which represents the health of the link and helps to predict the link failure. In other words, link breakage happens due to node movement and subsequently reducing signal strength of receiving packets. DPLM scheme helps ad hoc networks to avoid or postpone costly operation of route rediscovery in on-demand routing protocols by taking above-mentioned preventive action. ^ This dissertation advocates close but simple collaboration between the routing, medium access control and physical layers. In order to extend the link, the Dynamic Source Routing (DSR) and IEEE 802.11 MAC protocols were modified to use the ability of directional antennas to transmit over longer distance. A directional antenna module is implemented in OPNET simulator with two separate modes of operations: omnidirectional and directional. The antenna module has been incorporated in wireless node model and simulations are performed to characterize the performance improvement of mobile ad hoc networks. Extensive simulations have shown that without affecting the behavior of the routing protocol noticeably, aggregate throughput, packet delivery ratio, end-to-end delay (latency), routing overhead, number of data packets dropped, and number of path breaks are improved considerably. We have done the analysis of the results in different scenarios to evaluate that the use of directional antennas with proposed DPLM scheme has been found promising to improve the performance of mobile ad hoc networks. ^

A 802.11p prototype implementation

This paper presents an IEEE 802.11p full-stack prototype implementation to data exchange among vehicles and between vehicles and the roadway infrastructures. The prototype architecture is based on FPGAs for Intermediate Frequency (IF) and base band purposes, using 802.11a based transceivers for RF interfaces. Power amplifiers were also addressed, by using commercial and in-house solutions. This implementation aims to provide technical solutions for Intelligent Transportation Systems (ITS) field, namely for tolling and traffic management related services, in order to promote safety, mobility and driving comfort through the dynamic and real-time cooperation among vehicles and/or between vehicles and infrastructures. The performance of the proposed scheme is tested under realistic urban and suburban driving conditions. Preliminary results are promising, since they comply with most of the 802.11p standard requirements.

BANMAC: an opportunistic MAC protocol for reliable communications in body area networks

We consider reliable communications in Body Area Networks (BAN), where a set of nodes placed on human body are connected using wireless links. In order to keep the Specific Absorption Rate (SAR) as low as possible for health safety reasons, these networks operate in low transmit power regime, which however, is known to be error prone. It has been observed that the fluctuations of the Received Signal Strength (RSS) at the nodes of a BAN on a moving person show certain regularities and that the magnitude of these fluctuations are significant (5 - 20 dB). In this paper, we present BANMAC, a MAC protocol that monitors and predicts the channel fluctuations and schedules transmissions opportunistically when the RSS is likely to be higher. The MAC protocol is capable of providing differentiated service and resolves co-channel interference in the event of multiple co-located BANs in a vicinity. We report the design and implementation details of BANMAC integrated with the IEEE 802.15.4 protocol stack. We present experimental data which show that the packet loss rate (PLR) of BANMAC is significantly lower as compared to that of the IEEE 802.15.4 MAC. For comparable PLR, the power consumption of BANMAC is also significantly lower than that of the IEEE 802.15.4. For co-located networks, the convergence time to find a conflict-free channel allocation was approximately 1 s for the centralized coordination mechanism and was approximately 4 s for the distributed coordination mechanism.