O consumo de dados em dispositivos móveis cresce em taxas que dobram a cada ano. Tal crescimento demonstra como os dispositivos móveis ganham importância e como eles têm sido usados no dia a dia da população. Entretanto, o acesso à Internet ainda possui alto custo e nem sempre está disponível. Esse cenário apresenta o desafio de mantermos o uso dos dispositivos móveis acessível e viável, mesmo quando a Internet não esteja disponível. A comunicação direta entre os dispositivos é vista como alternativa para comunicação sem Internet e, consequentemente, para a redução do tráfego de dados nas redes de celulares. Além disso, ela pode ser útil para manter os dispositivos comunicando entre si mesmo desconectados da Internet. O protocolo Wi-Fi Direct (WD) é uma referência para esse tipo de comunicação, uma vez que seu protocolo não demanda infraestrutura de rede pré-estabelecida para que a comunicação aconteça e utiliza hardware padrão para comunicação Wi-Fi. Apesar dessas vantagens, seu uso é pouco difundido, o que o torna desconhecido pelos usuários, sendo uma das possíveis causas a complexidade de uso. De forma diferente, a conexão com a Internet, que acontece de forma quase espontânea, no WD as partes envolvidas precisam se envolver ativamente, na escolha e autorização, para que a conexão seja estabelecida. A complexidade da comunicação entre dispositivo pode ser constatada quando os usuários utilizam a Internet para enviar dados mesmo que o dispositivo alvo esteja ao lado da origem. Para superar esse obstáculo, a conexão entre os dispositivos deve ser tão ou mais simples do que a ação de enviar um e-mail ou uma mensagem instantânea usando a Internet. Para lidar com esse cenário, este trabalho propõe uma alternativa para comunicação entre dispositivos próximos que não demanda autorização manual prévia a cada conexão com um dispositivo, e que, ainda assim, permita que o usuário decida se quer ou não usar os dados transmitidos por uma conexão. Para isso definimos uma arquitetura que possibilite a conexão e transferência de dados entre os dispositivos próximos sem a necessidade de intervenção prévia do usuário e implementamos o conceito proposto no sistema operacional para dispositivos móveis Android / The consumption data on mobile devices is growing at rates double every year. This growth demonstrates how mobile devices gain importance and how they have been used in everyday life of the population. However, the internet also has high cost and is not always available. This scenario presents the challenge of maintaining the use of affordable and viable mobile devices even when the Internet is not available. Direct communication between the devices is regarded as no alternative for internet communication and, consequently, to reduce the data traffic in cellular networks. Furthermore, it can be useful to keep the devices communicating among themselves disconnected from the Internet. The Wi-Fi Direct (WD) protocol is a reference to this type of communication, since its protocol does not require pre-established network infrastructure for communication to happen and uses standard hardware for Wi-Fi communication. Despite these advantages, its use is not widespread, making it unknown to the users, one of the possible causes of the complexity of use. Differently, the connection to the Internet, which happens almost spontaneously, the WD parties need to engage actively in the selection and authorization for the connection to be established. The complexity of communication between device can be found when users use the Internet to send data even if the target device is adjacent to the source. To overcome this obstacle, the connection between the devices should be as or more simple than the action of sending an email or an instant message using the Internet. To handle this scenario, this paper proposes an alternative for communication between nearby devices that does not require prior manual authorization for each connection to a device, and that still allow the user to decide whether or not to use the data transmitted by a connection. For this we define an architecture that enables the connection and data transfer between nearby devices without the need for prior user intervention and implement the concept proposed in the Android operating system for mobile devices

O consumo de dados em dispositivos móveis cresce em taxas que dobram a cada ano. Tal crescimento demonstra como os dispositivos móveis ganham importância e como eles têm sido usados no dia a dia da população. Entretanto, o acesso à Internet ainda possui alto custo e nem sempre está disponível. Esse cenário apresenta o desafio de mantermos o uso dos dispositivos móveis acessível e viável, mesmo quando a Internet não esteja disponível. A comunicação direta entre os dispositivos é vista como alternativa para comunicação sem Internet e, consequentemente, para a redução do tráfego de dados nas redes de celulares. Além disso, ela pode ser útil para manter os dispositivos comunicando entre si mesmo desconectados da Internet. O protocolo Wi-Fi Direct (WD) é uma referência para esse tipo de comunicação, uma vez que seu protocolo não demanda infraestrutura de rede pré-estabelecida para que a comunicação aconteça e utiliza hardware padrão para comunicação Wi-Fi. Apesar dessas vantagens, seu uso é pouco difundido, o que o torna desconhecido pelos usuários, sendo uma das possíveis causas a complexidade de uso. De forma diferente, a conexão com a Internet, que acontece de forma quase espontânea, no WD as partes envolvidas precisam se envolver ativamente, na escolha e autorização, para que a conexão seja estabelecida. A complexidade da comunicação entre dispositivo pode ser constatada quando os usuários utilizam a Internet para enviar dados mesmo que o dispositivo alvo esteja ao lado da origem. Para superar esse obstáculo, a conexão entre os dispositivos deve ser tão ou mais simples do que a ação de enviar um e-mail ou uma mensagem instantânea usando a Internet. Para lidar com esse cenário, este trabalho propõe uma alternativa para comunicação entre dispositivos próximos que não demanda autorização manual prévia a cada conexão com um dispositivo, e que, ainda assim, permita que o usuário decida se quer ou não usar os dados transmitidos por uma conexão. Para isso definimos uma arquitetura que possibilite a conexão e transferência de dados entre os dispositivos próximos sem a necessidade de intervenção prévia do usuário e implementamos o conceito proposto no sistema operacional para dispositivos móveis Android / The consumption data on mobile devices is growing at rates double every year. This growth demonstrates how mobile devices gain importance and how they have been used in everyday life of the population. However, the internet also has high cost and is not always available. This scenario presents the challenge of maintaining the use of affordable and viable mobile devices even when the Internet is not available. Direct communication between the devices is regarded as no alternative for internet communication and, consequently, to reduce the data traffic in cellular networks. Furthermore, it can be useful to keep the devices communicating among themselves disconnected from the Internet. The Wi-Fi Direct (WD) protocol is a reference to this type of communication, since its protocol does not require pre-established network infrastructure for communication to happen and uses standard hardware for Wi-Fi communication. Despite these advantages, its use is not widespread, making it unknown to the users, one of the possible causes of the complexity of use. Differently, the connection to the Internet, which happens almost spontaneously, the WD parties need to engage actively in the selection and authorization for the connection to be established. The complexity of communication between device can be found when users use the Internet to send data even if the target device is adjacent to the source. To overcome this obstacle, the connection between the devices should be as or more simple than the action of sending an email or an instant message using the Internet. To handle this scenario, this paper proposes an alternative for communication between nearby devices that does not require prior manual authorization for each connection to a device, and that still allow the user to decide whether or not to use the data transmitted by a connection. For this we define an architecture that enables the connection and data transfer between nearby devices without the need for prior user intervention and implement the concept proposed in the Android operating system for mobile devices

Obtaining data simultaneously from different sensors located on different mobile devices can be useful for applications such as sports and medicine. In order for the data from the different sensors to be combined for analysis, the mobile devices need to be time synchronized first. This paper presents an application that can be used to calculate the difference between the internal clocks of two android devices using a combination of the Cristian and Marzullo algorithms. Different methods to connect the devices over Wi-Fi as well as the internet are tested to determine the optimal method for clock synchronization. The paper also validates the synchronization by testing different sensors on two identical android smartphones. The results show that clock synchronization between two mobile devices can be achieved with a round-trip time of 2 milliseconds or less using Wi-Fi Direct. Validation of the synchronization shows that a delay of 7 milliseconds or less can be achieved between two sensors of the same type on two identical android smartphones. It also shows that the least achievable delay between sensors of different types is 16 milliseconds. The conclusion is that once two android smartphones’ clocks are synchronized, only data from sensors of the same type can be combined, with the exception of the camera sensor. Further testing with more robust equipment is needed in order to eliminate human error which could possibly yield more desirable results. / Att erhålla data från olika sensorer som finns på olika mobila enheter kan vara användbart inom exempelvis sport och medicin. För att data från de olika sensorerna ska kunna kombineras för analys måste de mobila enheterna tidssynkroniseras först. Denna rapport presenterar en applikation som kan användas för att beräkna skillnaden mellan de interna klockorna på två Android enheter med en kombination av Cristian- och Marzullo -algoritmerna. Olika metoder för att ansluta enheterna via både Wi-Fi och internet testas för att bestämma den optimala metoden för tidssynkronisering. Rapporten validerar också synkroniseringen genom att testa olika sensorer på två identiska Android -smartphones. Resultaten visar att klocksynkronisering mellan två mobila enheter kan uppnås med en round-trip time på 2 millisekunder eller mindre med Wi-Fi Direct. Validering av synkroniseringen visar att en fördröjning på 7 millisekunder eller mindre kan uppnås mellan två sensorer av samma typ på två identiska Android -smartphones. Det visar också att den minst möjliga fördröjningen mellan sensorer av olika typer är 16 millisekunder. Slutsatsen är att när två Android smartphones är tidssynkroniserade kan endast data från sensorer av samma typ kombineras, med undantag för kamerasensorn. Ytterligare tester med mer robust utrustning behövs för att eliminera mänskliga fel vilket kan möjligen ge mer önskvärda resultat.

The aim of this diploma thesis is to create a practical solution for individual athletes in the form of a digital mirror, which can become an alternative to observing yourself in an ordinary mirror. The work contains and emphasizes the benefits of a digital mirror. Much of the work is devoted to the transfer of video between various devices for the ability to combine multiple videos on a single screen. The core of the solution is a mobile application for the Android platform, which works in various modes, the choice of which depends on how the application is used. The application was continuously tested with a group of users, resulting in iterative improvements to the application's features and the addition of new features. Furthermore, a web variant of the application was implemented, which increases the possibility of using the digital mirror across different platforms. The results of testing show that this whole solution can be used in the practical training of sports exercises and the application has the potential to connect with various sports.

Face à la prolifération des technologies mobiles et à l’augmentation du volume des données utilisées par les applications mobiles, les périphériques consomment de plus en plus de bande passante. Dans cette thèse, nous nous concentrons sur les réseaux Wi-Fi denses comme cela peut être le cas lors d’événements à grande échelle (ex: conférences, séminaire, etc.) où un serveur doit acheminer des données à un grand nombre de périphériques dans une fenêtre temporelle réduite. Dans ce contexte, la consommation de bande passante et les interférences engendrées par les téléchargements parallèles d’une donnée volumineuse par plusieurs périphériques connectés au même réseau dégradent les performances. Les technologies de communication Device-to-Device (D2D) comme Bluetooth ou Wi-Fi Direct permettent de mieux exploiter les ressources du réseau et d’améliorer les performances pour offrir une meilleure qualité d’expérience (QoE) aux utilisateurs. Dans cette thèse nous proposons deux approches pour l’amélioration des performances de la dissémination de données. La première approche, plus adaptée à une configuration mobile, consiste à utiliser des connexions D2D en point-à-point sur une topologie plate pour les échanges de données. Nos évaluations montrent que notre approche permet de réduire les temps de dissémination jusqu’à 60% par rapport à l’utilisation du Wi-Fi seul. De plus, nous veillons à avoir une répartition équitable de la charge énergétique sur les périphériques afin de préserver les batteries les plus faibles du réseau. Nous avons pu voir qu’avec la prise en compte de l’autonomie des batteries et de la bande passante, la sollicitation des batteries les plus faibles peut être réduite de manière conséquente. La deuxième approche, plus adaptée à des configurations statiques, consiste à mettre en place des topologies hiérarchiques dans lesquelles on regroupe les périphériques par clusters. Dans chaque cluster, un périphérique est élu pour être le relais des données qu’il recevra depuis le serveur et qu’il transmettra à ses voisins. Cette approche permet de gérer plus efficacement les interférences en adaptant la puissance du signal afin de limiter la portée des clusters. Dans ce cas, nous avons observé jusqu’à 30 % de gains en temps de dissémination. Dans la continuité des travaux de cette thèse, nous discutons de plusieurs perspectives qu’il serait intéressant d’entreprendre par la suite, notamment l’adaptation automatique du protocole de dissémination à l’état du réseau et l’utilisation simultanée des deux types de topologie plate et hiérarchique. / We are witnessing a proliferation of mobile technologies and an increasing volume of data used by mobile applications. Devices consume thus more and more bandwidth. In this thesis, we focus on dense Wi-Fi networks during large-scale events (such as conferences). In this context, the bandwidth consumption and the interferences caused by the parallel downloads of a large volume of data by several mobile devices that are connected to the same Wi-Fi network degrade the performance of the dissemination. Device-to-Device (D2D) communication technologies such as Bluetooth or Wi-Fi Direct can be used in order to improve network performance to deliver better QoE to users. In this thesis we propose two approaches for improving the performance of data dissemination. The first approach, more suited to a dynamic configuration, is to use point-to-point D2D connections on a flat topology for data exchange. Our evaluations show that our approach can reduce dissemination times by up to 60% compared to using Wi-Fi alone. In addition, we ensure a fair distribution of the energy load on the devices to preserve the weakest batteries in the network. We have observed that by taking into account the battery life and the bandwidth of mobile devices, the solicitation of the weakest batteries can be reduced significantly. The second approach, more adapted to static configurations, consists in setting up hierarchical topologies by gathering mobile devices in small clusters. In each cluster, a device is chosen to relay the data that it receives from the server and forwards it to its neighbors. This approach helps to manage interference more efficiently by adjusting the signal strength in order to limit cluster reach. In this case, we observed up to 30% gains in dissemination time. In the continuity of this thesis work, we discuss three perspectives which would be interesting to be undertaken, in particular the automatic adaptation of the dissemination to the state of the network and the simultaneous use of both topology types, flat and hierarchical.