 and her detailed comments on many versions of the report.
Daniel P. Siewiorek, Carnegie Mellon University, and Andrew J. Viterbi, Viterbi Group, LLC.
Information technology (IT) is on the verge of another revolution. Driven by the increasing capabilities and ever declining costs of com- puting and communications devices, IT is being embedded into a growing range of physical devices linked together through networks and will become ever more pervasive as the component technologies become smaller, faster, and cheaper. These changes are sometimes obvious—in pagers and Internet-enabled cell phones, for example—but often IT is buried inside larger (or smaller) systems in ways that are not easily visible to end users. These networked systems of embedded computers, referred to as EmNets throughout this report, have the potential to change radi- cally the way people interact with their environment by linking together a range of devices and sensors that will allow information to be collected, shared, and processed in unprecedented ways. The range of applications continues to expand with continued research and development. Examples of ways in which EmNets will be applied include the following: EmNets will be implemented as a kind of digital nervous system to enable instru- mentation of all sorts of spaces, ranging from in situ environmental moni- toring to surveillance of battlespace conditions; EmNets will be employed in personal monitoring strategies (both defense related and civilian), com- bining information from sensors on and within a person with information from laboratory tests and other sources; and EmNets will dramatically affect scientific data collection capabilities, ranging from new techniques for precision agriculture and biotechnological research to detailed envi- ronmental and pollution monitoring.
The use of EmNets throughout society could well dwarf previous milestones in the information revolution. The effects of Moore’s law1 and related trends in computing and communications are making all of this possible. Ongoing work in microelectromechanical systems (MEMS) will enable sensing and actuation on the scale of a nanometer. The possibili- ties for miniaturization extend into all aspects of life, and the potential for embedding computing and communications technology quite literally everywhere is becoming a reality. IT will eventually become an invisible component of almost everything in everyone’s surroundings.
WHAT IS DIFFERENT ABOUT EMNETS?
EmNets are more than simply the next step in the evolution of the personal computer or the Internet. Building on developments in both areas, EmNets will also be operating under a set of constraints that will demand more than merely incremental improvements to more traditional networking and information technology. EmNets will tend to be tightly coupled to the physical world. Unlike a desktop computer, which is itself a piece of office furniture, EmNets will be integrated into furniture and other objects in the environment. Individuals will interact with the ob- jects and devices of which EmNets are a part, but it is unlikely that they will think of it as interacting with a computer system. A complex, net- worked, computational system will often be invisible when things are working properly.
EmNet components will also be highly resource constrained. In con- trast to the Internet, which still consists primarily of tethered devices, EmNet components are likely to be small, untethered devices operating under physical constraints such as limited energy and the need for ad- equate heat dissipation. EmNets will also be constrained by bandwidth and memory limitations.
1Moore’s law refers to the observation by Gordon Moore in 1965 that each new micropro- cessor contains roughly twice as much capacity as its predecessor, and each chip is usually released within 18 to 24 months of the previous chip. As this trend has continued, comput- ing power has risen exponentially.
likely heterogeneity and large number of interacting elements that will make up an EmNet; this makes interoperability a key concern. Finally, EmNets will often be used and interacted with by people who are not experts in EmNet-related technology. Managing all of these constraints and creating a system that functions properly for the application domain while remaining understandable and manageable by human operators, users, and—in many cases—casual passersby, is a large challenge for EmNet designers.
As an example, consider a transportation information system based on EmNet technology. Such a system will certainly be large in size and scale, possibly encompassing the entire highway system of the United States. Components of it would probably be embedded in long-lived physical structures (such as bridges, traffic lights, individual cars, and perhaps even the paint on the roads). Some components will be tethered, but many would be resource constrained while computing data and com- municating it wirelessly when necessary. The many pieces of such a system will of necessity be heterogeneous, not only in form but also in function. There may be subsystems that communicate to consumers in private vehicles, others that relay information from emergency vehicles to synchronize traffic lights, still others that provide traffic data and analysis to highway engineers, and perhaps some that communicate to law en- forcement. Issues of how information will be communicated to those interacting with the system are of great importance in such an environ- ment. Safety is a critical concern; issues of privacy and security arise as well, along with concerns about reliability.
The rest of this report identifies areas in which research is needed to enable such EmNets and to make them a successful reality. Below are highlights of some of these areas as well as particular recommendations to federal funding agencies.
Realizing the great promise of EmNets requires more than the mere advance of individual technologies—it will rely on numerous subsystems working together in an efficient, unattended, comprehensible, and trust- worthy manner. Many aspects of the needed research are highly interdis- ciplinary because of the intricate ways in which EmNet systems interact with the physical world. In the absence of programs aimed at solving some of the basic research problems, it is likely that many of the benefits of EmNets will simply not be realized.
safety, and privacy protection issues. As EmNets become increasingly critical to our communication, transportation, power distribution, and health-care infrastructures, the consequences of failures and security breaches will become increasingly severe. By the time EmNets are broadly deployed, it may not be feasible to give them technological fixes because their components are so widely dispersed.
This report by the Committee on Networked Systems of Embedded Computing, convened by the Computer Science and Telecommunications Board of the National Research Council, identifies and explores the many research questions that must be answered before there can be implemen- tation and use of widespread networked embedded computing devices. It examines the enabling technologies that will facilitate the development and broad deployment of EmNets, and it explores three key areas in which a great deal of new research will be required for EmNets to achieve their full potential: (1) self-configuration and adaptive coordination, (2) building trustworthy EmNets (including issues of privacy, security, reliability, safety, and usability), and (3) models of computation. Enabling technologies and these key areas of research, explored in depth in Chap- ters 2, 3, 4, and 5, are briefly described below.
Given the expected pervasive and ubiquitous nature of EmNets, it will be necessary for these systems to be able to configure themselves and adapt to their environments automatically. Self-configuration and adaptive coordination comprise a spectrum of changes that a system makes to itself in response to occurrences both internal to it and external. EmNets will be relatively long lived, which greatly increases their chances of being upgraded, extended, and otherwise modified. Moreover, EmNets will be exposed to both continual environmental and component dynamics. In effect, the original EmNet must be designed with automatic reconfigura- tion and adaptation in mind, especially when the specifics of that recon- figuration cannot be known at design time. Current work in distributed systems has not solved the problem of systems operating under the con- straints that networked systems of embedded computers will experience, particularly with respect to computational resources, communication limi- tations, and energy restrictions.
will appear in hybrid environments of mobile and static networks; their nodes will be diverse in capability, energy availability, and quality of connectivity; the wireless layer is both diverse and limited by energy constraints, making low power discovery a challenge. Some of the issues that will need to be investigated and resolved for configuration and adap- tation to succeed in EmNets include stable localized control, abstraction, and memory use. Research issues related to service discovery include the scaling of discovery protocols, security, and the development of adequate failure models for automatically configured networks.
Adaptive coordination involves changes in the behavior of a system as it responds to changes in the environment or system resources. Coor- dination will not be mediated by humans because EmNets are so large and the time scale over which the adaptation will need to take place is too short for a human to be able to intervene. Achieving adaptive coordina- tion in EmNets will not only require drawing on the lessons learned from adaptive coordination in existing distributed systems, but it will also re- quire meeting the radical new challenges of EmNets that are due to the physically embedded nature of the collaborative control tasks and the massive numbers of elements, all combined with the relatively con- strained capabilities of individual elements. Adaptive coordination is a fairly new area of investigation, particularly as it applies to EmNets. To obtain necessary adaptability in EmNets, research is needed in three ar- eas: exploiting massive redundancy to achieve system robustness and longevity, decentralized control, and collaborative processing.
EmNets will be deployed in large numbers and will become an essen- tial part of the fabric of everyday life. In the same way that people often assume that electric power and telephone