Timothy Sohn

A diary study of mobile information needs

Being mobile influences not only the types of information people seek but also the ways they attempt to access it. Mobile contexts present challenges of changing location and social context, restricted time for information access, and the need to share attentional resources among concurrent activities. Understanding mobile information needs and associated interaction challenges is fundamental to improving designs for mobile phones and related devices. We conducted a two-week diary study to better understand mobile information needs and how they are addressed. Our study revealed that depending on the time and resources available, as well as the situational context, people use diverse and, at times, ingenious ways to obtain needed information. We summarize key findings and discuss design implications for mobile technology.

Mobility detection using everyday GSM traces

Recognition of everyday physical activities is difficult due to the challenges of building informative, yet unobtrusive sensors. The most widely deployed and used mobile computing device today is the mobile phone, which presents an obvious candidate for recognizing activities. This paper explores how coarse-grained GSM data from mobile phones can be used to recognize high-level properties of user mobility, and daily step count. We demonstrate that even without knowledge of observed cell tower locations, we can recognize mobility modes that are useful for several application domains. Our mobility detection system was evaluated with GSM traces from the everyday lives of three data collectors over a period of one month, yielding an overall average accuracy of 85%, and a daily step count number that reasonably approximates the numbers determined by several commercial pedometers.

Place-Its: a study of location-based reminders on mobile phones

Context-awareness can improve the usefulness of automated reminders. However, context-aware reminder applications have yet to be evaluated throughout a persons daily life. Mobile phones provide a potentially convenient and truly ubiquitous platform for the detection of personal context such as location, as well as the delivery of reminders. We designed Place-Its, a location-based reminder application that runs on mobile phones, to study people using location-aware reminders throughout their daily lives. We describe the de-sign of Place-Its and a two-week exploratory user study. The study reveals that location-based reminders are useful, in large part because people use location in nuanced ways.

Social disclosure of place: from location technology to communication practices

Communication of ones location as part of a social discourse is common practice, and we use a variety of technologies to satisfy this need. This practice suggests a potentially useful capability that technology may support more directly. We present such a social location disclosure service, Reno, designed for use on a common mobile phone platform. We describe the guiding principles that dictate parameters for creating a usable, useful and ubiquitous service and we report on a pilot study of use of Reno for a realistic social network. Our preliminary results reveal the competing factors for a system that facilitates both manual and automatic location disclosure, and the role social context plays in making such a lightweight communication solution work.

Are GSM Phones THE Solution for Localization

In this paper, we argue that localization solution based on cellular phone technology, specifically GSM phones, is a sufficient and attractive option in terms of coverage and accuracy for a wide range of indoor, outdoor, and placebased location-aware applications. We present preliminary results that indicate that GSM-based localization systems have the potential to detect the places that people visit in their everyday lives, and can achieve median localization accuracies of 5 and 75 meters for indoor and outdoor environments, respectively.

Control, deception, and communication: evaluating the deployment of a location-enhanced messaging service

We report on a two-week deployment of a peer-to-peer, mobile, location-enhanced messaging service. This study is specifically aimed at investigating the need for and effectiveness of automatic location disclosure mechanisms, the emerging strategies to achieve plausible deniability, and at understanding how place and activity are used to communicate plans, intentions and provide awareness. We outline the research that motivated this study, briefly describe the application we designed, and provide details of the evaluation process. The results show a lack of value of automatic messaging functions, confirm the need for supporting plausible deniability in communications, and highlight the prominent use of activity instead of place to indicate ones location. Finally, we offer suggestions for the development of social mobile applications.

iCAP: an informal tool for interactive prototyping of context-aware applications

iCAP is a system that assists users in prototyping context-aware applications. iCAP supports sketching for creating input and output devices, and using these devices to design interaction rules, which can be prototyped in a simulated or real context-aware environment. We were motivated to build our system by the lack of tools currently available for developing rich sensor-based applications. We iterated on the design of our system using paper prototypes and obtained feedback from fellow researchers, to develop a robust system for prototyping context-aware applications.

Peopletones: a system for the detection and notification of buddy proximity on mobile phones

Mobile phones have the potential to be useful agents for their owners by detecting and reporting situations that are of interest. Several challenges emerge in the case of detecting and reporting nice to know situations. Being alerted of these events may not be of critical importance but may be useful if the user is not busy. For detection, the precision of sensing must be high enough to minimize annoying false notifications, despite the constraints imposed by the inaccuracy of commodity sensors and the limited battery power available on mobile phones. For reporting, the notifications cannot be too obtrusive to the user or those in the vicinity. Peripheral cues are appropriate for conveying information like proximity, but have been studied primarily in settings like offices where sensors and cueing mechanisms can be controlled. We explore these issues through the design of PeopleTones, a buddy proximity application for mobile phones. We contribute (1) an algorithm for detecting proximity, (2) techniques for reducing sensor noise and power consumption, and (3) a method for generating peripheral cues. Empirical measurements demonstrate the precision and recall characteristics of our proximity algorithm. A two-week study of three groups of friends using PeopleTones shows that our techniques were effective, enabling the study of how people respond to peripheral cues in the wild. Our qualitative findings underscore the importance of cue selection and personal control for peripheral cues.

What did they do? understanding clickstreams with the WebQuilt visualization system

This paper describes the visual analysis tool WebQuilt, a web usability logging and visualization system that helps web design teams record and analyze usability tests. The logging portion of WebQuilt unobtrusively gathers clickstream data as users complete specified tasks. This data is then aggregated and presented as an interactive graph, where nodes of the graph are images of the web pages visited, and arrows are the transitions between pages. To aid analysis of the gathered usability test data, the WebQuilt visualization provides filtering capabilities and semantic zooming, allowing the designer to understand the test results at the gestalt view of the entire graph, and then drill down to sub-paths and single pages. The visualization highlights important usability issues, such as pages where users spent a lot of time, pages where users get off track during the task, navigation patterns, and exit pages, all within the context of a specific task. WebQuilt is designed to conduct remote usability testing on a variety of Internet-enabled devices and provide a way to identify potential usability problems when the tester cannot be present to observe and record user actions.

Experiences with place lab: an open source toolkit for location-aware computing

Location-based computing (LBC) is becoming increasing important in both industry and academia. A key challenge is the pervasive deployment of LBC technologies; to be effective they must run on a wide variety of client platforms, including laptops, PDAs, and mobile phones, so that location data can be acquired anywhere and accessed by any application. Moreover, as a nascent area, LBC is experiencing rapid innovation in sensing technologies, the positioning algorithms themselves, and the applications they support. Lastly, as a newcomer, LBC must integrate with existing communications and application technologies, including web browsers and location data interchange standard.This paper describes our experience in developing the Place Lab architecture, a widely used first-generation open source toolkit for client-side location sensing. Using a layered, pattern-based architecture, it supports modular development in any dimension of LBC, enabling the field to move forward more rapidly as these innovations are shared with the community as pluggable components. Our experience shows the benefits of domain-specific abstractions, and how we overcame high-level language constraints to support a wide array of platforms in this emerging space. We also describe our experience in re-engineering parts of the architecture based on the needs of the user community, including insights on software licensing issues.