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o began Mark Weiser’s seminal 1991 paper [1] that described his vision of ubiquitous computing, now also called pervasive computing. The essence of that vision was the creation of environments saturated with computing and communication capability, yet gracefully integrated with human users. When articulated, this was a vision too far ahead of its time — the hardware technology needed to achieve it simply did not exist. Not surprisingly, the implementation attempted by Weiser and his colleagues at Xerox PARC fell short. After a decade of hardware progress, many critical elements of pervasive computing that were exotic in 1991 are now viable commercial products: handheld and wearable computers; wireless LANs; and devices to sense and control appliances. We are now better positioned to begin the quest for Weiser ’s vision. Pervasive computing projects have emerged at major universities and in industry. Examples at universities include Project Aura at Carnegie Mellon University, Endeavour at the University of California at Berkeley (UC Berkeley), Oxygen at the Massachusetts Institute of Technology (MIT), and Portalano at the University of Washington. Industry examples include work at AT&T Research in Cambridge, United Kingdom, and at the IBM T. J. Watson Research Center. Each of these projects addresses a different mix of issues in pervasive computing, and a different blend of near-term and far-term goals. Together, they represent a broad communal effort to make pervasive computing a reality. The goal of this article is to help us understand the challenges in computer systems research posed by pervasive computing. We begin by examining its relationship to the closely related fields of distributed systems and mobile computing. Next, we sketch two pervasive computing scenarios, and ask why they are fiction rather than fact today. From that starting point, we delve deeper into some key research problems. To preserve focus on computer systems issues, we avoid digressions into other areas important to pervasive computing such as human-computer interaction, expert systems, and software agents. Related Fields