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.

Segurança em redes sem fio: estudo sobre o desenvolvimento de conjuntos de dados para comparação de IDS

Pós-graduação em Engenharia Elétrica - FEIS

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

Pós-graduação em Engenharia Elétrica - FEIS

Cross-layer optimizations in multi-hop ad hoc networks

Unlike traditional wireless networks, characterized by the presence of last-mile, static and reliable infrastructures, Mobile ad Hoc Networks (MANETs) are dynamically formed by collections of mobile and static terminals that exchange data by enabling each other's communication. Supporting multi-hop communication in a MANET is a challenging research area because it requires cooperation between different protocol layers (MAC, routing, transport). In particular, MAC and routing protocols could be considered mutually cooperative protocol layers. When a route is established, the exposed and hidden terminal problems at MAC layer may decrease the end-to-end performance proportionally with the length of each route. Conversely, the contention at MAC layer may cause a routing protocol to respond by initiating new routes queries and routing table updates. Multi-hop communication may also benefit the presence of pseudo-centralized virtual infrastructures obtained by grouping nodes into clusters. Clustering structures may facilitate the spatial reuse of resources by increasing the system capacity: at the same time, the clustering hierarchy may be used to coordinate transmissions events inside the network and to support intra-cluster routing schemes. Again, MAC and clustering protocols could be considered mutually cooperative protocol layers: the clustering scheme could support MAC layer coordination among nodes, by shifting the distributed MAC paradigm towards a pseudo-centralized MAC paradigm. On the other hand, the system benefits of the clustering scheme could be emphasized by the pseudo-centralized MAC layer with the support for differentiated access priorities and controlled contention. In this thesis, we propose cross-layer solutions involving joint design of MAC, clustering and routing protocols in MANETs. As main contribution, we study and analyze the integration of MAC and clustering schemes to support multi-hop communication in large-scale ad hoc networks. A novel clustering protocol, named Availability Clustering (AC), is defined under general nodes' heterogeneity assumptions in terms of connectivity, available energy and relative mobility. On this basis, we design and analyze a distributed and adaptive MAC protocol, named Differentiated Distributed Coordination Function (DDCF), whose focus is to implement adaptive access differentiation based on the node roles, which have been assigned by the upper-layer's clustering scheme. We extensively simulate the proposed clustering scheme by showing its effectiveness in dominating the network dynamics, under some stressing mobility models and different mobility rates. Based on these results, we propose a possible application of the cross-layer MAC+Clustering scheme to support the fast propagation of alert messages in a vehicular environment. At the same time, we investigate the integration of MAC and routing protocols in large scale multi-hop ad-hoc networks. A novel multipath routing scheme is proposed, by extending the AOMDV protocol with a novel load-balancing approach to concurrently distribute the traffic among the multiple paths. We also study the composition effect of a IEEE 802.11-based enhanced MAC forwarding mechanism called Fast Forward (FF), used to reduce the effects of self-contention among frames at the MAC layer. The protocol framework is modelled and extensively simulated for a large set of metrics and scenarios. For both the schemes, the simulation results reveal the benefits of the cross-layer MAC+routing and MAC+clustering approaches over single-layer solutions.

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

Enabling Blocks for Integrated CMOS UWB Transceivers

The last decades have seen an unrivaled growth and diffusion of mobile telecommunications. Several standards have been developed to this purposes, from GSM mobile phone communications to WLAN IEEE 802.11, providing different services for the the transmission of signals ranging from voice to high data rate digital communications and Digital Video Broadcasting (DVB). In this wide research and market field, this thesis focuses on Ultra Wideband (UWB) communications, an emerging technology for providing very high data rate transmissions over very short distances. In particular the presented research deals with the circuit design of enabling blocks for MB-OFDM UWB CMOS single-chip transceivers, namely the frequency synthesizer and the transmission mixer and power amplifier. First we discuss three different models for the simulation of chargepump phase-locked loops, namely the continuous time s-domain and discrete time z-domain approximations and the exact semi-analytical time-domain model. The limitations of the two approximated models are analyzed in terms of error in the computed settling time as a function of loop parameters, deriving practical conditions under which the different models are reliable for fast settling PLLs up to fourth order. Besides, a phase noise analysis method based upon the time-domain model is introduced and compared to the results obtained by means of the s-domain model. We compare the three models over the simulation of a fast switching PLL to be integrated in a frequency synthesizer for WiMedia MB-OFDM UWB systems. In the second part, the theoretical analysis is applied to the design of a 60mW 3.4 to 9.2GHz 12 Bands frequency synthesizer for MB-OFDM UWB based on two wide-band PLLs. The design is presented and discussed up to layout level. A test chip has been implemented in TSMC CMOS 90nm technology, measured data is provided. The functionality of the circuit is proved and specifications are met with state-of-the-art area occupation and power consumption. The last part of the thesis deals with the design of a transmission mixer and a power amplifier for MB-OFDM UWB band group 1. The design has been carried on up to layout level in ST Microlectronics 65nm CMOS technology. Main characteristics of the systems are the wideband behavior (1.6 GHz of bandwidth) and the constant behavior over process parameters, temperature and supply voltage thanks to the design of dedicated adaptive biasing circuits.

Progetto e valutazione di un protocollo MAC per reti wireless ad-hoc

Per dare supporto al traffico multimediale in una rete totalmente distribuita come le reti ad-hoc, il protocollo MAC deve fornire garanzie di QoS. L'IEEE ha sviluppato un standard per supportare le QoS chiamato 802.11e, facente parte della famiglia 802.11. Per dare supporto al QoS viene proposto un nuovo protocollo chiamato PAB che consiste in un accesso al canale preceduto da una serie di invii di burst, inviati alla stessa frequenza dei dati, che inibiscono la trasmissione di stazioni avente minore priorità. Lo scopo di questo protocollo è fornire servizi QoS, evitare starvation e fornire un accesso equo tra le stazioni.

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.

Progettazione ed implementazione di un prototipo per la geolocalizzazione indoor dei device wifi in ambito aeroportuale.

Nel documento vengono trattate le principali tecniche di geolocalizzazione basate sull'elaborazione dei segnali elettromagnetici ricevuti. E' altresì introdotto un sistema di remote positioning basato su test di prossimità rafforzato tramite machine learning tramite un approccio simulativo ed una implementazione reale.

Reti wi-fi e sicurezza

Descrizione dei vari standard 802.11 e della loro evoluzione, analisi dei protocolli di sicurezza e possibili attacchi alle reti wireless.

A Smart TCP Acknowledgment Approach for Multihop Wireless Networks

Reliable data transfer is one of the most difficult tasks to be accomplished in multihop wireless networks. Traditional transport protocols like TCP face severe performance degradation over multihop networks given the noisy nature of wireless media as well as unstable connectivity conditions in place. The success of TCP in wired networks motivates its extension to wireless networks. A crucial challenge faced by TCP over these networks is how to operate smoothly with the 802.11 wireless MAC protocol which also implements a retransmission mechanism at link level in addition to short RTS/CTS control frames for avoiding collisions. These features render TCP acknowledgments (ACK) transmission quite costly. Data and ACK packets cause similar medium access overheads despite the much smaller size of the ACKs. In this paper, we further evaluate our dynamic adaptive strategy for reducing ACK-induced overhead and consequent collisions. Our approach resembles the sender side's congestion control. The receiver is self-adaptive by delaying more ACKs under nonconstrained channels and less otherwise. This improves not only throughput but also power consumption. Simulation evaluations exhibit significant improvement in several scenarios

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.