To some extent, the emergence of networked systems of embedded computers (EmNets) is simply a natural evolution of the historical trend in computing and communications technologies toward smaller, more powerful information technology devices that have become more ubiquitous (see Box 1.1). As computing has migrated from mainframe computers to minicomputers, personal computers, laptops, and, most recently, palmtop computers and information appliances, it has become more widespread and more a part of everyday life for millions. Meanwhile, embedded computers have been used in automobiles, aerospace engineering, and military applications for quite some time. Advances in networking technologies, including the expansion of the Internet and wireless communications networks, have amplified these trends by making information easier to share and increasing the amount of information that is shared.
At the same time, the shift to EmNets represents a radical departure from this lineage. While most traditional computers tend to interact directly with human operators—typically accepting input through a keyboard and providing output on a visual display—EmNets will interact more directly with the physical world. They will sense their environ-
The vision of a world filled with large numbers of computing elements, many of which are hidden inside other objects and networked together, is not new. Trends in the miniaturization of computing and communications elements have been manifested for decades, leading to numerous predictions of computing power being integrated imperceptibly into daily life. One of the leading visionaries, the late Mark Weiser, formerly the chief technologist at the Xerox Palo Alto Research Center (PARC), described in the early 1990s a concept of ubiquitous computing in which computation would blend invisibly into the environment, much as written communication has become so common a part of the physical world that little thought is given to the technology of writing (Weiser, 1991; 1993). Others have elaborated on related themes, coining terms such as pervasive computing (NIST, 1999) and invisible computing (Norman, 1998) to describe the proliferation of information technology into myriad devices and applications. Although differing somewhat in their details, these visions of the future of computing derive from a common set of observations about the rapid pace of innovation in information technology: namely, advances in very-large-scale integrated circuits (VLSI), the increasing bandwidth of wireless and wireline communications media, improvements in wireless communications technologies, and significant efforts in architecture and infrastructure. (See Chapter 2 for a more detailed discussion of enabling technologies.)