Browsing by Subject "Mobile computing."
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Item Open Access Camera-based 3D interaction for handheld devices(Bilkent University, 2010) Pekin, Tacettin SercanUsing handheld devices is a very important part of our daily life. Interacting with them is the most unavoidable part of using them. Today’s user interface designs are mostly adapted from desktop computers. The result of this was difficulties of using handheld devices. However processing power, new sensing technologies and cameras are already available for mobile devices. This gives us the possibility to develop systems to communicate through different modalities. This thesis proposes some novel approaches, including finger detection, finger tracking and object motion analysis, to allow efficient interaction with mobile devices. As the result of my thesis, a new interface between users and mobile devices is created. This is a new way of interaction with the mobile device. It enables direct manipulation on objects. The technique does not require any extra hardware. The interaction method, maps an object’s motion (such as a finger’s or a predefined marker’s motion) to a virtual space to achieve manipulation which is moving in front of the camera. For Finger Detection, a new method is created based on the usage of the mobile devices and structure of thumb. A fast two dimensional color-based scene analysis method is applied to solve the problem. For Finger Tracking, a new method is created based on the movement ergonomics of thumb when holding the mobile device on hand. Extracting the three dimensional movement from the two dimensional RGB data is an important part of this section of the study. A new 3D pointer data and pointer image is created for usage with 3D input and 3D interaction of 3D scenes. Also direct manipulation for low cost is achieved.Item Open Access A context aware approach for enhancing gesture recognition accuracy on handheld devices(Bilkent University, 2010) Yıldırım, Hacı MehmetInput capabilities (e.g. joystick, keypad) of handheld devices allow users to interact with the user interface to access the information and mobile services. However, these input capabilities are very limited because of the mobile convenience. New input devices and interaction techniques are needed for handheld devices. Gestural interaction with accelerometer sensor is one of the newest interaction techniques on mobile computing. In this thesis, we introduce solutions that can be used for automatically enhancing the gesture recognition accuracy of accelerometer sensor, and as a standardized gesture library for gestural interaction on touch screen and accelerometer sensor. In this novel solution, we propose a framework that decides on suitable signal processing techniques for acceleration sensor data for a given context of the user. First system recognizes the context of the user using pattern recognition algorithm. Then, system automatically chooses signal ltering techniques for recognized context, and recognizes gestures. Gestures are also standardized for better usage. In this work, we also present several experiments which show the feasibility and e ectiveness of our automated gesture recognition enhancement system.Item Open Access Data dissemination strategies for mobile peer-to-peer information systems with applications to healthcare(Bilkent University, 2009) Özbekoğlu, Fatih MelihPeer-to-peer (P2P) architecture is becoming increasingly popular for various applications, replacing the classical Client-Server architecture. With the enhanced capabilities of mobile devices (PDAs, mobile phones, etc.) wireless networks started to take advantage of P2P paradigm along with its properties like infrastructure-free operation, scalability, balanced and distributed workload. Mobile peer-to-peer (MP2P) networks refer to the application of P2P architecture over wireless networks. Problems about dissemination of data in both P2P and MP2P networks are widely studied, and there are many proposed solutions. Healthcare information systems are helping clinicians to hold the information belonging to patients and diseases, and to communicate with each other since early 1950s. Today, they are widely used in hospitals, being constructed using Client-Server network architecture. Wireless technologies are also applied to medical domain, especially for monitoring purposes. In this thesis, we present and evaluate various data dissemination strategies to work on a mobile peer-to-peer (MP2P) network designed for a medical healthcare environment. First, the designed network system is presented along with the network topology. Then, the proposed data dissemination strategies are described. And finally, these strategies are evaluated according to the properties and needs of a medical system.Item Open Access Dual-finger 3D interaction techniques for mobile devices(Bilkent University, 2012) Telkenaroğlu, CanThree-dimensional capabilities on mobile devices are increasing, and interactivity is becoming a key feature of these tools. It is expected that users will actively engage with the 3D content, instead of being passive consumers. Because touchscreens provide a direct means of interaction with 3D content by directly touching and manipulating 3D graphical elements, touch-based interaction is a natural and appealing style of input for 3D applications. However, developing 3D interaction techniques for handheld devices using touch-screens is not a straightforward task. One issue is that when interacting with 3D objects, users occlude the object with their fingers. Furthermore, because the user’s finger covers a large area of the screen, the smallest size of the object users can touch is limited. In this thesis, we first inspect existing 3D interaction techniques based on their performance with handheld devices. Then, we present a set of precise Dual-Finger 3D Interaction Techniques for a small display. Then, we present the results of an experimental study, where we evaluate the usability, performance, and error rate of the proposed and existing 3D interaction techniques. Finally, we integrate the proposed methods of different user modes.Item Open Access Random delay techniques for location privacy in VANETs(Bilkent University, 2013) Albakır Çatal, SatiyeVehicular ad hoc network (VANET) is an emerging new communication technology which has attracted a lot of research attention from academic community and industry. It is promising technology to provide safer and efficient traffic conditions. This is realized by letting vehicles to exchange safety messages. This messaging increases the awareness of vehicles about their neighboring vehicles positions and warns drivers about dangerous situations. However, availability of such information facilitates the tracking of vehicles. So, this information must be protected against the potential misuse. In this thesis, we address the problem of achieving location privacy in VANETs with randomly changing identifiers (i.e. pseudonyms) in the presence of a global passive adversary. We suggest adding a random delay to message broadcast period after the vehicle update its pseudonym in mix zones. By this way, we want to mitigate the linkability between pseudonyms. This could help to make tracking more difficult and increase safety and confidence of drivers using VANET. Instead of adding delay to safety messages completely random, one step taken further and delay is added according to the silent vehicle number in mix zone. We also investigated the effects of different number of mix-zone placements in the network to the location privacy of users. Several simulations have been performed to evaluate the performance of the systems. The results of experiments show that adding delay to message broadcast period improves location privacy of drivers in VANET and also provide information about the relationship between the strength of the adversary and the level of privacy achieved by changing pseudonyms.Item Open Access Using a data mining approach for the prediction of user movements in mobile environments(Bilkent University, 2003) Yavaş, GökhanMobility prediction is one of the most essential issues that need to be explored for mobility management in mobile computing systems. In this thesis, we propose a new algorithm for predicting the next inter-cell movement of a mobile user in a Personal Communication Systems network. In the first phase of our three-phase algorithm, user mobility patterns are mined from the history of mobile user trajectories. In the second phase, mobility rules are extracted from these patterns, and in the last phase, mobility predictions are accomplished by using these rules. The performance of the proposed algorithm is evaluated through simulation as compared to two other prediction methods. The performance results obtained in terms of Precision and Recall indicate that our method can make more accurate predictions than the other methods.