Shravan Gaonkar

Micro-Blog: sharing and querying content through mobile phones and social participation

Recent years have witnessed the impacts of distributed content sharing (Wikipedia, Blogger), social networks (Facebook, MySpace), sensor networks, and pervasive computing. We believe that significant more impact is latent in the convergence of these ideas on the mobile phone platform. Phones can be envisioned as people-centric sensors capable of aggregating participatory as well as sensory inputs from local surroundings. The inputs can be visualized in different dimensions, such as space and time. When plugged into the Internet, the collaborative inputs from phones may enable a high resolution view of the world. This paper presents the architecture and implementation of one such system, called Micro-Blog. New kinds of application-driven challenges are identified and addressed in the context of this system. Implemented on Nokia N95 mobile phones, Micro-Blog was distributed to volunteers for real life use. Promising feedback suggests that Micro-Blog can be a deployable tool for sharing, browsing, and querying global information.

EnLoc: Energy-Efficient Localization for Mobile Phones

A growing number of mobile phone applications utilize physical location to express the context of information. Most of these location-based applications assume GPS capabilities. Unfortunately, GPS incurs an unacceptable energy cost that can reduce the phones battery life to less than nine hours. Alternate localization technologies, based on WiFi or GSM, improve battery life at the expense of localization accuracy. This paper quantifies this important tradeoff that underlies a range of emerging services. Driven by measurements from Nokia N95 phones, we develop an energy-efficient localization framework called EnLoc. The framework characterizes the optimal localization accuracy for a given energy budget, and develops prediction- based heuristics for real-time use. Evaluation on traces from real users demonstrates the possibility of achieving good localization accuracy for a realistic energy budget.

Using mobile phones to write in air

Numerous sensors in modern mobile phones enable a range of people-centric applications. This paper envisions a system called PhonePoint Pen that uses the in-built accelerometer in mobile phones to recognize human writing. By holding the phone like a pen, a user should be able to write short messages or draw simple diagrams in the air. The acceleration due to hand gestures can be translated into geometric strokes, and recognized as characters. We prototype the PhonePoint Pen on the Nokia N95 platform, and evaluate it through real users. Results show that English characters can be identified with an average accuracy of 91.9%, if the users conform to a few reasonable constraints. Future work is focused on refining the prototype, with the goal of offering a new user-experience that complements keyboards and touch-screens.

Möbius 2.3: An extensible tool for dependability, security, and performance evaluation of large and complex system models

Möbius 2.3 is an extensible dependability, security, and performance modeling environment for large-scale discrete-event systems. It provides multiple model formalisms and solution techniques, facilitating the representation of each part of a system in the formalism that is most appropriate for it, and the application of the solution method or methods best-suited to estimating the systems behavior. Since its initial release in 2001, many advances have been made in Möbiuss design and implementation that have strengthened its place in the modeling and analysis community. With almost a decade of widespread academic and industrial use, Möbius has proven itself to be useful in a wide variety of modeling situations. This paper documents the current feature set of Möbius 2.3, emphasizing recent significant enhancements.

Designing dependable storage solutions for shared application environments

The costs of data loss and unavailability can be large, so businesses use many data protection techniques such as remote mirroring, snapshots, and backups to guard against failures. Choosing an appropriate combination of techniques is difficult because there are numerous approaches for protecting data and allocating resources. Storage system architects typically use ad hoc techniques, often resulting in overengineered expensive solutions or underprovisioned inadequate ones. In contrast, this paper presents a principled automated approach for designing dependable storage solutions for multiple applications in shared environments. Our contributions include search heuristics for intelligent exploration of the large design space and modeling techniques for capturing interactions between applications during recovery. Using realistic storage system requirements, we show that our design tool produces designs that cost up to two times less in initial outlays and expected data penalties than the designs produced by an emulated human design process. Additionally, we compare our design tool to a random search heuristic and a genetic algorithm metaheuristic, and show that our approach consistently produces better designs for the cases we have studied. Finally, we study the sensitivity of our design tool to several input parameters.

PhonePoint pen: using mobile phones to write in air

The ability to note down small pieces of information, quickly and ubiquitously, can be useful. This paper proposes a system called PhonePoint Pen that uses the in-built accelerometer in mobile phones to recognize human writing. By holding the phone like a pen, an user should be able to write short messages or even draw simple diagrams in air. The acceleration due to hand gestures can be converted into an image, and sent to the users Internet email address for future reference. We motivate the utility of such a system through simple use-cases and applications, and present the design and implementation challenges towards a functional prototype. Our early results show that the PhonePoint Pen is feasible if the user is restricted to a few simple constraints.

Energy-Efficient Localization via Personal Mobility Profiling

Location based services are on the rise, many of which assume GPS based localization. Unfortunately, GPS incurs an unacceptable energy cost that can reduce the phone’s battery life to less than ten hours. Alternate localization technology, based on WiFi or GSM, improve battery life at the expense of localization accuracy. This paper quantifies this important tradeoff that underlies a wide range of emerging applications. To address this tradeoff, we show that humans can be profiled based on their mobility patterns, and such profiles can be effective for location prediction. Prediction reduces the energy consumption due to continuous localization. Driven by measurements from Nokia N95 phones, we develop an energy-efficient localization framework called EnLoc. Evaluation on real user traces demonstrates the possibility of achieving good localization accuracy for a realistic energy budget.

Performance and dependability modeling with Möbius

Möbius is a multi-paradigm multi-solution framework to describe and analyze stochastic models of discrete-event dynamic systems. Möbius is widely used in academia and industry for the performance and dependability assessment of technical systems. It comes with a design of experiments as well as automated support for distributing a series of simulation experiments over a network to support the exploration of design spaces for real-world applications. In addition to that, the Möbius simulator interfaces with Traviando, a separate trace analyzer and visualizer that helps to investigate the details of a complex model for validation, verification, and debugging purposes. In this paper, we outline the development of a multi-formalism model of a Lustre-like file system, the analysis of its detailed simulated behavior, and the results obtained from a simulation study.

Designing Dependable Storage Solutions for Shared Application Environments

The costs of data loss and unavailability can be large, so businesses use many data protection techniques such as remote mirroring, snapshots, and backups to guard against failures. Choosing an appropriate combination of techniques is difficult because there are numerous approaches for protecting data and allocating resources. Storage system architects typically use ad hoc techniques, often resulting in overengineered expensive solutions or underprovisioned inadequate ones. In contrast, this paper presents a principled automated approach for designing dependable storage solutions for multiple applications in shared environments. Our contributions include search heuristics for intelligent exploration of the large design space and modeling techniques for capturing interactions between applications during recovery. Using realistic storage system requirements, we show that our design tool produces designs that cost up to two times less in initial outlays and expected data penalties than the designs produced by an emulated human design process. Additionally, we compare our design tool to a random search heuristic and a genetic algorithm metaheuristic, and show that our approach consistently produces better designs for the cases we have studied. Finally, we study the sensitivity of our design tool to several input parameters.

Micro-Blog: map-casting from mobile phones to virtual sensor maps

The synergy of phone sensors (microphone, camera, GPS, etc.), wireless capability, and ever-increasing device density can lead to novel people-centric applications. Unlike traditional sensor networks, the next generation networks may be participatory, interactive, and in the scale of human users. Millions of global data points can be organized on a visual platform, queried, and sophistically answered through human participation. Recent years have witnessed the isolated impacts of distributed knowledge sharing (Wikipedia), social networks, sensor networks, and mobile communication. We believe that significant more impact is latent in their convergence, that can to be drawn out through innovations in applications. This demonstration, called Micro-Blog, is a first step towards this goal.