Computing devices and applications are now used beyond the desktop, in diverse environments, and this trend toward ubiquitous computing is accelerating. One challenge that remains in this emerging research field is the ability to enhance the behavior of any application by informing it of the context of its use. By context, we refer to any information that characterizes a situation related to the interaction between humans, applications and the surrounding environment. Context-aware applications promise richer and easier interaction, but the current state of research in this field is still far removed from that vision. This is due to three main problems: (1) the notion of context is still ill defined; (2) there is a lack of conceptual models and methods to help drive the design of context-aware applications; and (3) no tools are available to jump-start the development of context-aware applications. In this paper, we address these three problems in turn. We first define context, identify categories of contextual information, and characterize context-aware application behavior. Though the full impact of context-aware computing requires understanding very subtle and high-level notions of context, we are focusing our efforts on the pieces of context that can be inferred automatically from sensors in a physical environment. We then present a conceptual framework that separates the acquisition and representation of context from the delivery and reaction to context by a contextaware application. We have built a toolkit, the Context Toolkit, that instantiates this conceptual framework and supports the rapid development of a rich space of context-aware applications. We illustrate the usefulness of the conceptual framework by describing a number of contextaware applications that h...

Abstract. The use of context is important in interactive applications. It is particularly important for applications where the user’s context is changing rapidly, such as in both handheld and ubiquitous computing. In order to better understand how we can use context and facilitate the building of context-aware applications, we need to more fully understand what constitutes a contextaware application and what context is. Towards this goal, we have surveyed existing work in context-aware computing. In this paper, we provide an overview of the results of this survey and, in particular, definitions and categories of context and context-aware. We conclude with recommendations for how this better understanding of context inform a framework for the development of context-aware applications. 1

Context-aware computing is a mobile computing paradigm in which applications can discover and take advantage of contextual information (such as user location, time of day, nearby people and devices, and user activity). Since it was proposed about a decade ago, many researchers have studied this topic and built several context-aware applications to demonstrate the usefulness of this new technology. Context-aware applications (or the system infrastructure to support them), however, have never been widely available to everyday users. In this survey of research on context-aware systems and applications, we looked in depth at the types of context used and models of context information, at systems that support collecting and disseminating context, and at applications that adapt to the changing context. Through this survey, it is clear that context-aware research is an old but rich area for research. The difficulties and possible solutions we outline serve as guidance for researchers hoping to make context-aware computing a reality. 1.

Context is a key issue in interaction between human and computer, describing the surrounding facts that add meaning. In mobile computing research published the parameter location is most often used to approximate context and to implement context-aware applications. We propose that ultra-mobile computing, characterized by devices that are operational and operated while on the move (e.g. PDAs, mobile phones, wearable computers), can significantly benefit from a wider notion of context. To structure the field we introduce a working model for context, discuss mechanisms to acquire context beyond location, and application of context-awareness in ultra-mobile computing. We investigate the utility of sensors for context-awareness and present two prototypical implementations - a light sensitive display and an orientation aware PDA interface. The concept is then extended to a model for sensor fusion to enable more sophisticated context recognition. Based on an implementation of the model an exp...

Analyzing the way people use ultra-mobile devices (personal digital assistants, smart mobile phones, handheld and wearable computers) it becomes apparent that the periods of interaction are much shorter than in traditional mobile settings. Notebook computers are mainly used in a temporary stationary setting, e.g. one takes a notebook to a meeting and takes note and a salesman takes a mobile

Context-awareness is one of the drivers of the ubiquitous computing paradigm, whereas a well designed model is a key accessor to the context in any context-aware system. This paper provides a survey of the the most relevant current approaches to modeling context for ubiquitous computing. Numerous approaches are reviewed, classified relative to their core elements and evaluated with respect to their appropriateness for ubiquitous computing. 1.

Piconet is a general-purpose, low-power ad hoc radio network. It provides a base level of connectivity to even the simplest of sensing and computing objects. It is our intention that a full range of portable and embedded devices may make use of this connectivity. This article outlines the Piconet system, under development at the Olivetti and Oracle Research Laboratory (ORL). The authors discuss the motivation for providing this low-level "embedded networking," and describe their experiences of building such a system. The article concludes with a commentary on some of the implications that power saving, and other considerations central to Piconet, have on the design of the system.

The use of context in mobile devices is receiving increasing attention in mobile and ubiquitous computing research. In this article we consider how to augment mobile devices with awareness of their environment and situation as context. Most work to date has been based on integration of generic sensor, in particular for positioning and for vision. We propose the integration of diverse simple sensors as alternative, aimed at awareness of situational context that can not be inferred from location, and targeted at resource constraint device platforms that typically do not permit processing of visual context. We have investigated multi-sensor contextawareness in a series of project and report experience from development of a number of device prototypes. These include development of an awareness module used for augmentation of a mobile phone, of the Mediacup exemplifying context-enabled everyday artefacts, and of the Smart-Its platform for aware mobile devices. The prototypes have been explored in a range of applications, to validate the multi-sensor approach to awareness, but moreover to develop new perspectives of how embedded context-awareness can be applied in mobile and ubiquitous computing.

AbstractÐSome location estimation methods, such as the GPS satellite navigation system, require nonstandard features either in the mobile terminal or the network. Solutions based on generic technologies not intended for location estimation purposes, such as the cell-ID method in GSM/GPRS cellular networks, are usually problematic due to their inadequate location estimation accuracy. In order to enable accurate location estimation when only inaccurate measurements are available, we present an approach to location estimation that is different from the prevailing geometric one. We call our approach the statistical modeling approach. As an example application of the proposed statistical modeling framework, we present a location estimation method based on a statistical signal power model. We also present encouraging empirical results from simulated experiments supported by real-world field tests. Index TermsÐLocation estimation, mobile terminals, signal propagation, statistical modeling. 1

In this article smart appliances are characterized as devices that are attentive to their environment. We introduce a terminology for situation, sensor data, context, and context-aware applications because it is important to gain a thorough understanding of these concepts to successfully build such artifacts. In the article the relation between a real-world situation and the data read by sensors is discussed; furthermore, an analysis of available sensing technology is given. Then we introduce an architecture that supports the transformation from sensor data to cues then to contexts as a foundation to make context-aware applications. The article suggests a method to build context-aware devices; the method starts from situation analysis, offers a structured way for selection of sensors, and finally suggests steps to determine recognition and abstraction methods. In the final part of the article the question of how this influences the applications is raised and the areas of user int...