Throughout the history of computing, there has been a trend for the ratio of processing elements to people to increase, resulting in the creation and popularization of new usage paradigms. At the start of the modern computer age, many individual users shared a single mainframe in one central location. In the early 1980s, however, significant developments in microprocessor technologies ushered in the desktop era, resulting in a one-to-one correspondence between individual users and their computers. Computer resources were now intrinsically distributed. The growth of the internet allowed these resources to connect to each other. The pervasive computing paradigm is the next logical stage in this trend, resulting in the original computer-human ratio reversing, so that multiple computational devices are available to each individual user. In reality, this point was passed a number of years ago. Mobile phones, personal digital assistants (PDAs), portable music players, as well as numerous embedded devices that people now take for granted, has resulted in computing technologies being embedded into the fabric of everyday life. Thus, for the first time, the desire of computing resources being available on an anywhere, anytime basis is a realistic objective. In addition to computing being available everywhere, pervasive computing has a second key element. This tenet states that user interaction with these universal computing elements should occur in as natural and intuitive a manner as possible. Thus, pervasive computing technology should be assimilated transparently into the user’s natural environment. Rather than deal with the entirety of this broad topic, the focus of this article is to provide an overview of the key developments on one particular technology which is essential to the realization of the pervasive computing vision: the wireless sensor network.
The original vision for pervasive computing, originally termed ubiquitous computing and frequently referred to as such, was articulated in 1988 by Mark Weiser (1952-1999), then of Xerox’s Palo Alto Research Center (PARC) in California. The fundamental concept underlying his proposal was that a person’s interactions with computers should be as natural and intuitive as possible. One important consequence of this is that interactions should not be localized to a desktop-style interface, but rather, should be embedded within everyday objects, thus facilitating access to computational resources when and where necessary. In essence, it is a fusion of the anytime, anywhere computing concept augmented with an inherent need for embedded and intelligent user interfaces. Weiser observed that the technologies which have the greatest impact are those that people do not regard as technology per se, but, rather, as an integral component of their environment. He used writing, perhaps the original precursor to the information technology revolution, to illustrate his concept (Weiser, 1991, p. 94).
Pervasive computing technologies should be seen as an extension of an individual’s own capabilities, rather than an interface to a restricted set of predefined abilities. Instead of limiting people to a standard interface, pervasive computing envisages many different kinds of devices and interfaces for a myriad of tasks (Abowd, Mynatt, & Rodden, 2002). As an demonstration, Weiser’s team at PARC developed three kinds of devices corresponding to the inch, the foot, and the yard scale, which they entitled tabs, pads, and boards, respectively. These devices were designed to emulate commonly used office objects like post-it notes, paper note books, and bulletin boards, while providing enhanced computational capacities tailored to the scale of the device in question, and portability where appropriate (Weiser, 1991, p. 103).
Key Terms in this Chapter
Actuator: In the context of sensor networks, any output device. Actuators allow a WSN node to influence its environment, providing a feedback channel through which its decisions can be enacted.
Context-Awareness: The property of a system that allows it to adjust its behavior based on physical environmental cues, such as location, or user presence or absence. This necessitates the use of sensor networks which can monitor the relevant properties of the environment.
Sensor: In the context of sensor networks, any input device other than the communications transceiver, for example, a microphone or barometer. The sensors and transceiver produce a sensor node’s input data, which is used to inform its actions.
Human Computer Interaction (HCI): The study of how people and computers interact, the effects of these interactions on both the users and the computers, and the design and testing of new user interfaces for the purpose of improving the computer’s user-friendliness. HCI combines aspects of computer science, engineering, psychology, sociology, aesthetics, and ergonomics, as well as many other fields.
Wireless Sensor Network: A network comprised of small, communication-enabled microcontrollers with an array of sensors and actuators which rely on batteries or ambient environmental energy for power. These components are often referred to as sensor nodes.
Agents: In this article, the word agent refers to software entities which are capable of displaying autonomous, cooperative, and flexible behavior directed towards achieving a set of internal goals. A group of agents which operate together is called a multi-agent system (MAS).
Pervasive Computing: Also known as ubiquitous computing, this is the study of how computing can be integrated into the environment in a way that makes it easily accessible to users. It includes an emphasis on ease and naturalness of use, and unobtrusiveness is paramount.