REACHING FOR WEISER’S VISION Disappearing Hardware In Mark Weiser’s vision of ubiquitous computing, computers disappear from conscious thought. From a hardware perspective, the authors examine how far we’ve succeeded in implementing this vision and how far we have to go. or many tasks today, the use of comput- (such as spell checkers, calculators, electronic trans- ers is not entirely satisfactory. The inter- lators, electronic books, and Web pads). These actions take effort and are often difficult. devices have a specialized interface and address the The traditional, and still prevalent, com- desired goal of ease of use. In contrast, a PC is a gen- puting experience is sitting in front of a eralized machine, which makes it attractive to pur- Fbox, our attention completely absorbed in the dia- chase—the one-time investment having the potential log required to complete the details of a greater task. for many different uses. However, in other ways it Putting this in perspective, the real objective is the adds a level of complexity and formalism that hin- task’s completion, not the interaction with the tools ders the casual user. we use to perform it. Mark Weiser wanted to explore whether we could To illustrate the point further, if somebody asks design radically new kinds of computer systems. you for an electric drill, do they want to use a drill, These systems would allow the orchestration of or do they really want a hole? The answer is prob- devices with nontraditional form factors that lend ably the latter—but computers are currently very themselves to more natural, tacit interaction. They much a drill, requiring knowl- would take into account the space in which people 1 Roy Want and Trevor Pering edge, training, effort, and skill to worked, allowing positional and manipulative — Intel Research, Santa Clara use correctly. Creating a hole is rather than just keyboard and mouse—interactions. relatively simple, and many hid- Along with specialization and the use of embedded Gaetano Borriello den computers invisibly accom- computers, support for mobile computing and wire- University of Washington and plish what seem to be simple less data networks is an important facet of this Intel Research, Seattle tasks, such as regulating our cars’ vision—in other words, invisible connectivity. A goal Keith I. Farkas brakes. But unlike other inani- of this exploration is that we would learn to build Compaq Western Research mate objects, a computer system computer systems that do not distract the user; ide- Laboratory might be able to infer the result ally, the user might even forget the hardware is pres- autonomously and affect the ent.2 In essence, Weiser was proposing that well- desired outcome, increasing both designed computer systems would become invisible its potential and end-user complexity. Realizing this to the user and that our conscious notion of com- potential while managing the complexity is the fun- puter hardware would begin to disappear. Some damental challenge facing computer system years later, Don Norman popularized this concept researchers. in his book The Invisible Computer.3 An important trend over the last decade is the In this article, we survey the progress toward emergence of specialized, task-specific hardware Weiser’s vision from a hardware viewpoint. Where 36 PERVASIVEcomputing 1536-1268/02/$17.00 © 2002 IEEE Figure 1. Hardware improvement over the last decade: (a) the Xerox ParcTab, the first context-sensitive computer (1992). The design shows the limited display available at that time—a 128- × 64-pixel, monochrome LCD. (b) a typical PDA available today with a color 240- × 320-pixel VGA (transreflective) screen. have we been, where are we, and where are we headed? What characteristics will make hardware disappear from our conscious- ness, and what will it take to achieve them? Where we’ve been The research community embraced Weiser’s call to explore ubiquitous com- puting. For example, his vision inspired the work at the Xerox Palo Alto Research (a) (b) Center (PARC) in the early 1990s and such projects as ParcTab,4 Mpad,5 and Liveboard.6 Olivetti Research’s Active a pen and paper. Most of these products use: if we notice it’s there, it’s distracting Badge7 and Berkeley’s InfoPad8 projects have fallen by the wayside: Momenta and us from our real task. For example, if we also embraced this research direction, as EO, IBM’s early ThinkPad, and later the notice that we are using a slow wireless net- did other notable centers of excellence, Apple Newton, the Casio Zoomer, and Gen- work connection instead of just editing our such as at Carnegie Mellon University, eral Magic’s pad. For these designs, the ben- files, then the action of accessing the files is IBM, Rutgers University, Georgia Tech, efit-to-cost ratio was just not large enough. getting in the way of the real task, which is and the University of Washington. Unfor- To be successful, these new devices had to contained in the files themselves. If the link tunately, many of the early systems were either be better than the traditional pencil- is fast and robust, we will not notice it and based on technologies that were barely and-paper technology they were replacing can focus on the content. Likewise, if a dis- adequate for the task, so they fell short of or provide desired new functionality. The play can present only a poor representa- designer expectations. physical hardware was the dominating fac- tion of a high-quality underlying image, we Figures 1a and 1b illustrate the extent tor, and almost every design aspect affected see a bad display. A high-quality display of hardware improvement over the last acceptance: size, weight, power consump- suspends our belief that the image is only decade. In 1990, no Wireless Local Area tion, computation speed, richness of inter- a representation. Network standards existed; the processors face, and simplicity of design. The four most notable improvements in suitable for mobile devices operated at only We started to cross the acceptability hardware technology during the last decade a few megahertz, while PCs were typically threshold only in the latter half of the that directly affected ubiquitous comput- shipping with up to 50-MHz processors. decade with the Palm Pilot. It was smaller ing are wireless networking, processing The early electronic organizers (pen-based and lighter, focused on simple applications, capability, storage capacity, and high-qual- PDAs had not been invented) proudly and incorporated a novel one-button ity displays. Furthermore, the current pop- claimed 128 Kbytes of memory, while PCs approach to data synchronization. Finally, ular adoption of emerging technology, such shipped with 30-Mbyte disks. The displays an electronic organizer was useful for a sig- as cell phones and PDAs, strongly indicates were also quite crude: laptops used mono- nificant number of people and had real that the market is generally ready for chrome VGA, and the few handheld advantages over the more traditional paper advanced new technology. This adoption, devices available mainly used character- products such as Day-Timers. The com- however, requires common standards based displays. puter industry was beginning to move in across many products and locales. Industry soon responded to the challenge the right direction. with a tighter focus on mobile computing. Wireless networking A flurry of early products hit the market, Where we are Although progress in wireless connec- particularly in the tablet style, that tried to For hardware to disappear from our tivity was initially slow, it has increased. make using computers feel more like using consciousness, we require transparency of This area has witnessed two distinct devel- JANUARY–MARCH 2002 PERVASIVEcomputing 37 REACHING FOR WEISER’ S VISION opment trends. The first is in short-range The emergence of the latter IEEE wire- means that we can operate these devices at connectivity standards, such as Bluetooth less standards allows for communication higher speeds, increasing their effective per- (IEEE 802.15) and the IrDA (Infrared Data cells that span many hundreds of feet with formance. Additionally, reduced transistor Association) standards, which are primar- sufficient bandwidth to make us feel as if sizes decrease power consumption, allevi- ily for simple device-to-device communi- we were connected to a wired LAN, but ating some of the perpetual problems sur- cation. Bluetooth, which will get its first without a physical connection’s con- rounding energy storage technologies. real test in the marketplace in 2002, was straints. IEEE 802.11b has already been The combination of more transistors on designed as a short-range cable replace- widely adopted, and 802.11a is expected a given area of silicon and a reduced power ment, allowing for proximate interaction to follow with higher bandwidths. Next- budget has brought us the capabilities of and the discovery of resources in the user’s generation digital cellular networks such mid-1980’s desktop computers in today’s locality. IrDA had a similar aim. But as 2.5G (for example, General Packet battery-operated, handheld PDAs. Two because infrared signaling requires a line Radio Service and NTT’s DoCoMo—with examples are the Motorola Dragonball of sight, users had to physically place greater than 24 million users) and the com- and Intel StrongARM processors, the most devices next to each other, often an incon- ing 3G networks will extend these capa- common processors used by today’s PDAs. venience. This technology, which predates bilities to cover entire metropolitan areas. Besides providing low power consumption Bluetooth by many years, has been con- The wireless networking of today and and high performance, these processors sidered a market failure. (The sidebar lists the immediate future thus enables portable integrate their DRAM and LCD con- URLs for Bluetooth, IrDA, and other areas ubiquitous hardware that remains con- trollers and a host of other interface I/O of interest in this article.) nected to the global infrastructure.