A mobile ad-hoc network is an autonomous network of mobile devices that are connected via wireless links. In such networks there is no pre-existing infrastructure and nodes are free to move in a random fashion. Due to this mobility mobile ad-hoc networks have dynamic topologies. A host in the network typically has limited bandwidth and energy resources. Routing is a major challenge in the development of such systems and there have been many solutions proposed in the recent past. The aim of this work is to design and implement a routing scheme for a Positional Communication System (PCS). The PCS is a network of mobile handheld pocket PCs connected via wireless interfaces. The system allows voice and data communication between nodes in the network. This dissertation addresses the process of designing a routing protocol for an ad-hoc network. There have been many proposed algorithms that solve the routing problem in a mobile ad-hoc network. It is a difficult task to compare the performance of'these protocols qualitatively as there are many parameters that affect network performance. Various simulation packages for networks of this type exist. One such package is the Network Simulator (NS-2). It is a discrete time event simulator that can be used to model wired and wireless networks. This dissertation presents NS-2 simulations that compare four recently proposed routing algorithms. From this comparison study it is shown that on-demand algorithms perform best in a mobile ad-hoc environment. The dissertation then describes the design of a novel on-demand routing algorithm. The ondemand algorithms proposed thus far use a blind flooding technique during the route discovery process. This method is inefficient and creates excessive routing overhead. The routing protocol proposed in the dissertation implements a query localization technique that significantly reduces the network traffic. The protocol also introduces a load checking metric in addition to the metric used by most on-demand schemes, namely hop count. Simulation results show that such a scheme makes the on-demand routing algorithm more efficient and scalable than existing ones. It is widely believed that prior to implementing a routing protocol in real world systems it is essential that it is tested and validated on a test-bed. The dissertation presents the implementation of an on-demand routing algorithm in a Positional Communication System test-bed, where each handheld PC in the network runs an embedded Linux operating system. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

In this thesis, we focused on two problems in mobile application development: contextualization and large-scale testing. We identified the limitations of current contextualization and testing solutions. On one hand, advanced-remote-computing- based mobilization does not provide context awareness to the mobile applications it mobilized, so we presented contextify to provide context awareness to them without rewriting the applications or changing their source code. Evaluation results and user surveys showed that contextify-contextualized applications reduce users' time and effort to complete tasks. On the other hand, current mobile application testing solutions cannot conduct tests at the UI level and in a large-scale manner simultaneously, so we presented and implemented automated cloud computing (ACT) to achieve this goal. Evaluation results showed that ACT can support a large number of users and it is stable, cost-efficiency as well as time-efficiency.

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Augmented Reality is one of the hottest trends in mobile media, yet there is a substantial lack of user studies within this field of research. The purpose of this study is to evaluate the value of mobile augmented reality as a vehicle for information delivery on the basis of a usability and design analysis. Using a multi-­dimensional qualitative method, this study examines the impressions of users and designers regarding mobile augmented reality, along with a heuristic evaluation of select mobile applications. This analysis finds that (1) users believe mobile augmented reality offers great promise as a medium for visual communication, and (2) it’s current execution is limited by technical restraints, design flaws and a lack of compelling content. It is concluded that mobile augmented reality will one day revolutionize how consumers engage geographical and time-basedinformation. Yet, like all new technologies, mobile augmented reality needs time to mature in order to address these limitations. Finally, based on the findings of this study, this thesis offers suggested guidelines for future developments in this medium. / Department of Telecommunications

Our research posits a context-sensitive, adaptable, assistive services and technology system (CAAST) that takes advantage of the advancements in mobile computing to provide barrier-free access to environmental information and devices. To inform our research we explore the following topics: the deficiencies associated with current assistive technologies; the advances in wireless sensor node technology; the interference and accuracy problems associated with wireless location detection; the coordination problems associated with service discovery; the management and coordination problems associated with decentralized sensor nodes; the separation of information and activities from the human interface; the efficiency and abstraction problems associated with interface description languages; and the adaptation of information and activities to meet the needs of those with disabilities. As a result of our research into these areas we devise an assistive technology, CAAST, that intends to be a comprehensive approach to universal access to information and activities for those with disabilities. / Department of Computer Science

The proliferation of electronic devices supporting sensing, actuation, and wireless communication enables the monitoring and/or control of a variety of physical systems with digital communication. Such “cyber physical systems” blur the boundaries of the digital and physical worlds, where correct information about the physical world is needed for the correct operation of the digital system. Often in these systems the physical source or destination of information is as important as the information itself. However, the omni-directional and invisible nature of wireless communication makes it difficult to determine communication endpoints. This allows a malicious party to intercept wireless messages or pose as other entities in the system. As such, these systems require new protocols to associate the endpoints of digital communication with physical entities. Traditional security approaches that associate cryptographic keys with names can help verify endpoints in static systems where a string accurately describes the role of a device. In other systems, the role of a device depends on its physical properties, such as location, which change over time. This dynamic nature implies that identification of an endpoint based on a static name is insufficient. Instead, we can leverage devices’ sensing and actuation capabilities to verify the physical properties and determine the physical endpoints of communication. We investigate three different scenarios where the physical source and/or destination is important and propose endpoint verification techniques: verifying the physical endpoints during an exchange between two smartphones, verifying the receiver of information is in a physical space to enable location-based access control, and verifying the source of information to protect Vehicle-to-Vehicle (V2V) applications. We evaluate our proposals in these systems and show that our solutions fulfill the security requirements while utilizing existing hardware. Exchanging Information Between Smartphones Shake on it (SHOT) allows users to verify the endpoints during an exchange of information between two smartphones. In our protocol, the phones use their vibrators and accelerometers to establish a human-observable communication channel. The users hold the phones together while the phones use this channel to bootstrap and verify the authenticity of an exchange that occurs over the higher-bandwidth wireless channel. Users can detect the injection of information from other devices as additional vibrations, and prevent such attacks. Our implementation of SHOT for the DROID smartphone is able to support sender and receiver verification during an exchange between two smartphones in 15 seconds on average. Location-Based Access Control We propose using location-based access control to protect sensitive files on laptops, without requiring any effort from the user to provide security. With a purely wireless electronic system, verifying that a given device is in a physical space is a challenge; either the definition of the physical space is vague (radio waves can travel beyond walls) or the solution requires expensive hardware to measure a message’s time of flight. Instead, we use infrared as a signal that walls can contain. We develop key derivation protocols that ensure only a receiver in the physical room with access to the signal can derive the key. We implement a system that uses the laptop’s webcam to record the infrared signal, derive a key, and decrypt sensitive files in less than 5 seconds. Source Verification for V2V Networks A number of V2V applications use information about nearby vehicles to prevent accidents or reduce fuel consumption. However, false information about the positioning of vehicles can cause erroneous behavior, including accidents that would not occur in the absence of V2V. As such, we need a way to verify which vehicle sent a message and that the message accurately describes the physical state of that vehicle. We propose using LED lights on vehicles to broadcast the certificate a vehicle is currently using. Receivers can use onboard cameras to film the encoding of the certificate and estimate the relative location of the vehicle. This visual channel allows a receiver to associate a physical vehicle at a known location with the cryptographic credentials used to sign a location claim. Our simulations indicate that even with a pessimistic visual channel, visual verification of V2V senders provides sufficient verification capabilities to support the relevant applications.

Smartphones and tablets have been growing in popularity. These ultra mobile devices bring in new challenges for efficient network operations because of their mobility, resource constraints and richness of features. There is thus an increasing need to adapt network protocols to these devices and the traffic demands on wireless service providers. This dissertation focuses on identifying design limitations in existing network protocols when operating in ultra mobile environments and developing algorithmic solutions for the same. Our work comprises of three components. The first component identifies the shortcomings of TCP flow control algorithm when operating on resource constrained smartphones and tablets. We then propose an Adaptive Flow Control (AFC) algorithm for TCP that relies not just on the available buffer space but also on the application read-rate at the receiver. The second component of this work looks at network deduplication for mobile devices. With traditional network deduplication (dedup), the dedup source uses only the portion of the cache at the dedup destination that it is aware of. We argue in this work that in a mobile environment, the dedup destination (say the mobile) could have accumulated a much larger cache than what the current dedup source is aware of. In this context, we propose Asymmetric caching, a solution which allows the dedup destination to selectively feedback appropriate portions of its cache to the dedup source with the intent of improving the redundancy elimination efficiency. The third and final component focuses on leveraging network heterogeneity for prefetching on mobile devices. Our analysis of browser history of 24 iPhone users show that URLs do not repeat exactly. Users do show a lot of repetition in the domains they visit but not the particular URL. Additionally, mobile users access web content over diverse network technologies: WiFi and cellular (3G/4G). While data is unlimited over WiFi, users typically have monthly limits on data over the cellular network. In this context, we propose Precog, an action-based prefetching solution to reduce cellular data footprint on smartphones and tablets.

This thesis describes a universal multimedia access system and its implementation details. In the context of this thesis, universal multimedia access means accessing multimedia content over ubiquitous computer networks, using different computing platforms. The computer networks involve both wired and wireless networks, and computing platforms involve wired PC&rsquo / s, mobile PC&rsquo / s and personal digital assistants (PDA). The system is built on client/server architecture. Video data is H.263 coded and carried over RTP. Java Media Framework is utilized and its capabilities are extended with special plug-ins when necessary.

Nominally, one can expect any user of modern technology to at least carry a handheld device of the class of an iPAQ (perhaps in the form of a cellphone). The availability of technology in the environment (home, office, public spaces) also continues to grow at an amazing pace. With advances in technology, it is feasible to remain connected and enjoy services that we care about, be it entertainment, sports, or plain work, anytime anywhere. We need a system that supports seamless migration of services from handhelds to the environment (or vice versa) and between environments. Virtualization technology is able to support such a migration by providing a common virtualized interface on both source and destination. In this dissertation, we focus on two levels of virtualization to address issues for seamless mobility. We first identify three different kinds of spaces and three axes to support mobility in these spaces. Then we present two systems that address these dimensions from different perspectives. For middleware level virtualization, we built a system called MobiGo that can capture the application states and restore the service execution with saved states at the destination platform. It provides the architectural elements for efficiently managing different states in the different spaces. Evaluation suggested that the overhead of the system is relatively small and meets user's expectation. On the other hand, for device level virtualization, Chameleon is a Xen-like system level virtualization system to support device level migration and automatic capability adaptation at a lower level. Chameleon is able to capture and restore device states and automatically accommodate the heterogeneity of devices to provide the migration of services. Device level virtualization can address some issues that cannot be addressed in middleware level virtualization. It also has less requirements than middleware level virtualization in order to be applied to existing systems. Through performance measurements, we demonstrate that Chameleon introduces minimal overhead while providing capability adaptation and device state migration for seamless mobility in ubiquitous computing environments.

Mobile computing devices like handhelds are becoming ubiquitous and so is computing embedded in cyber-physical systems like cameras, smart sensors, vehicles, and many others. Further, the computation and communication resources present in these settings are becoming increasingly powerful. The resulting, rich execution platforms are enabling increasingly complex applications and system uses. These trends enable richer execution platforms for running ever more complex distributed applications. This thesis explores these opportunities (i) for cooperative mobile platforms, where the combined resources of multiple computing devices and the sensors attached to them can be shared to better address certain application needs, and (ii) for distributed platforms where opportunities for cooperation are further strengthened by virtualization. The latter offers efficient abstractions for device sharing and application migration that enable applications to operate across dynamically changing and heterogeneous systems without their explicit involvement. An important property of cooperative distributed platforms is that they jointly and cooperatively provide and maintain the collective resources needed by applications. Another property is that these platforms make decisions about the resources allocated to certain tasks in a decentralized fashion. In contrast to volunteer computing systems, however, cooperation implies the commitment of resources as well as the commitment to jointly managing them. The resulting technical challenges for the mobile environments on which this thesis is focused include coping with dynamic network topology, the runtime addition and removal of devices, and resource management issues that go beyond resource usage and scheduling to also include topics like energy consumption and battery drain. Platform and resource virtualization can provide important benefits to cooperative mobile platforms, the key one being the ability to hide from operating systems and applications the complexities implied by collective resource usage. To realize this opportunity, this thesis extends current techniques for device access and sharing in virtualized systems, particularly to improve their flexibility in terms of their ability to make the implementation choices needed for efficient service provision and realization in the mobile and embedded systems targeted by this work. Specifically, we use middleware-based approaches to flexibly extend device and service implementations across cooperative and virtualized mobile platforms. First, for cooperating platforms, application-specific overlay networks are constructed and managed in response to dynamics at the application level and in the underlying infrastructure. When virtualizing these platforms, these same middleware techniques are shown capable of providing uniform services to applications despite platform heterogeneity and dynamics. The approach is shown useful for sharing and remotely accessing devices and services, and for device emulation in mobile settings.