Connecting the Physical World with Pervasive Networks

M ark Weiser envisioned a world in which computing is so pervasive that everyday devices can sense their relationship to us and to each other. They could, thereby, respond so appropriately to our actions that the computing aspects would fade into the background. Underlying this vision is the assumption that sensing a broad set of physical phenomena, rather than just data input, will become a common aspect of small, embedded computers and that these devices will communicate with each other (as well as to some more powerful infrastructure) to organize and coordinate their actions. Recall the story of Sal in Weiser’s article; Sal looked out her window and saw “tracks” as evidence of her neighbors’ morning strolls. What sort of system did this seemingly simple functionality imply? Certainly Weiser did not envision ubiquitous cameras placed throughout the neighborhood. Such a solution would be far too heavy for the application’s relatively casual nature as well as quite invasive with respect to personal privacy. Instead, Weiser posited the existence of far less intrusive instrumentation in neighborhood spaces— perhaps smart paving stones that could detect local activity and indicate the walker’s direction based on exchanges between neighboring nodes. As we have marched technology forward, we are now in a position to translate this aspect of Weiser’s vision to reality and apply it to a wide range of important applications, both computing and social. Other articles in this issue address the user interface-, application-, software-, and device-level design challenges associated with realizing Weiser’s vision. Here, we address the challenges and opportunities of instrumenting the physical world with pervasive networks of sensor-rich, embedded computation. Such systems fulfill two of Weiser’s key objectives— ubiquity, by injecting computation into the physical world with high spatial density, and invisibility, by having the nodes and collectives of nodes operate autonomously. Of particular importance to the technical community is making such pervasive computing itself pervasive. We need reusable building blocks that can help us move away from the specialized instrumentation of each particular environment and move toward building reusable techniques for sensing, computing, and manipulating the physical world. The physical world presents an incredibly rich set of input modalities, including acoustics, image, motion, vibration, heat, light, moisture, pressure, ultrasound, radio, magnetic, and many more exotic modes. Traditionally, sensing and manipulating the This article addresses the challenges and opportunities of instrumenting the physical world with pervasive networks of sensor-rich, embedded computation. The authors present a taxonomy of emerging systems and outline the enabling technological developments. R E A C H I N G F O R W E I S E R ’ S V I S I O N