Andy Hopper

The active badge location system

A novel system for the location of people in an office environment is described. Members of staff wear badges that transmit signals providing information about their location to a centralized location service, through a network of sensors. The paper also examines alternative location techniques, system design issues and applications, particularly relating to telephone call routing. Location systems raise concerns about the privacy of an individual and these issues are also addressed.

The anatomy of a context-aware application

We describe a sensor-driven, or sentient, platform for context-aware computing that enables applications to follow mobile users as they move around a building. The platform is particularly suitable for richly equipped, networked environments. The only item a user is required to carry is a small sensor tag, which identifies them to the system and locates them accurately in three dimensions. The platform builds a dynamic model of the environment using these location sensors and resource information gathered by telemetry software, and presents it in a form suitable for application programmers. Use of the platform is illustrated through a practical example, which allows a users current working desktop to follow them as they move around the environment.

A new location technique for the active office

Configuration of the computing and communications systems found at home and in the workplace is a complex task that currently requires the attention of the user. Researchers have begun to examine computers that would autonomously change their functionality based on observations of who or what was around them. By determining their context, using input from sensor systems distributed throughout the environment, computing devices could personalize themselves to their current user, adapt their behaviour according to their location, or react to their surroundings. The authors present a novel sensor system, suitable for large-scale deployment in indoor environments, which allows the locations of people and equipment to be accurately determined. We also describe some of the context-aware applications that might make use of this fine-grained location information.

Virtual network computing

VNC is an ultra thin client system based on a simple display protocol that is platform independent. It achieves mobile computing without requiring the user to carry any hardware. VNC provides access to home computing environments from anywhere in the world, on whatever computing infrastructure happens to be available-including, for example, public Web browsing terminals in airports. In addition, VNC allows a single desktop to be accessed from several places simultaneously, thus supporting application sharing in the style of computer supported cooperative work (CSCW). The technology underlying VNC is a simple remote display protocol. It is the simplicity of this protocol that makes VNC so powerful. Unlike other remote display protocols such as the X Window System and Citrixs ICA, the VNC protocol is totally independent of operating system, windowing system, and applications. The VNC system is freely available for download from the ORL Web site at http://www.orl.co.uk/vnc/. We begin the article by summarizing the evolution of VNC from our work on thin client architectures. We then describe the structure of the VNC protocol, and conclude by discussing the ways we use VNC technology now and how it may evolve further as new clients and servers are developed.

A distributed location system for the active office

Distributed systems for locating people and equipment will be at the heart of tomorrows active offices. Computer and communications systems continue to proliferate in the office and home. Systems are varied and complex, involving wireless networks and mobile computers. However, systems are underused because the choices of control mechanisms and application interfaces are too diverse. It is therefore pertinent to consider which mechanisms might allow the user to manipulate systems in simple and ubiquitous ways, and how computers can be made more aware of the facilities in their surroundings. Knowledge of the location of people and equipment within an organization is such a mechanism. Annotating a resource database with location information allows location-based heuristics for control and interaction to be constructed. This approach is particularly attractive because location techniques can be devised that are physically unobtrusive and do not rely on explicit user action. The article describes the technology of a system for locating people and equipment, and the design of a distributed system service supporting access to that information. The application interfaces made possible by or that benefit from this facility are presented.<<ETX>>

Active badges and personal interactive computing objects

The authors describe a family of personal active badges developed for location of people and devices in the computer environment. Applications include location and paging of individuals as well as control of computer systems. Active badges are one type of a range of portable computers connected to cordless communication systems that can now be made. Because of their small size and application such devices are referred to as personal interactive computing objects. A speculative discussion of how such devices may be used in the traditional computing environment is given. >

Broadband ultrasonic location systems for improved indoor positioning

Ultrasonic location systems are a popular solution for the provision of fine-grained indoor positioning data. Applications include enhanced routing for wireless networks, computer-aided navigation, and location-sensitive device behavior. However, current ultrasonic location systems suffer from limitations due to their use of narrowband transducers, This paper investigates the use of broadband ultrasound for indoor positioning systems. Broadband ultrasonic transmitter and receiver units have been developed and characterized. The utilization of these units to construct two positioning systems with different architectures serves to highlight and affirm the concrete, practical benefits of broadband ultrasound for locating people and devices indoors.

TRIP: A Low-Cost Vision-Based Location System for Ubiquitous Computing

Abstract:Sentient Computing provides computers with perception so that they can react and provide assistance to user activities. Physical spaces are made sentient when they are wired with networks of sensors capturing context data, which is communicated to computing devices spread through the environment. These devices interpret the information provided and react by performing the actions expected by the user. Among the types of context information provided by sensors, location has proven to be especially useful. Since location is an important context that changes whenever the user moves, a reliable location-tracking system is critical to many sentient applications. However, the sensor technologies used in indoor location tracking are expensive and complex to deploy, configure and maintain. These factors have prevented a wider adoption of Sentient Computing in our living and working spaces. This paper presents TRIP, a low-cost and easily deployable vision-based sensor technology addressing these issues. TRIP employs off-the-shelf hardware (low-cost CCD cameras and PCs) and printable 2-D circular markers for entity identification and location. The usability of TRIP is illustrated through the implementation of several sentient applications.

Predicting the Performance of Virtual Machine Migration

With the ability to move virtual machines between physical hosts, live migration is a core feature of virtualisation. However for migration to be useful, deployable feature on a large (datacentre) scale, we need to predict migration times with accuracy. In this paper, we characterise the parameters affecting live migration with particular emphasis on the Xen virtualisation platform. We discuss the relationships between the important parameters that affect migration and highlight how migration performance can vary considerably depending on the workload. We further provide 2 simulation models that are able to predict migration times to within 90% accuracy for both synthetic and real-world benchmarks.

Pandora - an experimental system for multimedia applications

Pandora is a joint project between Olivetti Research Cambridge and the University of Cambridge Computer Laboratory. The project is investigating the use of multimedia workstations in a working environment with particular emphasis on digital video. It endeavours to place a camera on the desktop to make generation of multimedia documents as easy as producing text. We are aiming to produce a number of new applications as well as to provide insights into the way computer systems should be designed.The project is in three stages. In the first a peripheral, Pandoras Box, has been designed. This box can be attached to any one of a range of workstations and provides multimedia features. In the second stage a number of such systems are being deployed amongst a community of systems developers and application writers. Finally we will use the experimental system in our daily work to evaluate new applications. From the users point of view the normal workstation environment is maintained but additional features are available.This paper describes the design decisions which must be taken when incorporating video in a workstation. A description of the Pandoras Box peripheral which provides multimedia features is given. Finally the distributed system under construction is discussed.