Introduction and Motivation

The exponential increasing integration density, as dictated by Moore’s law [Moo65, Intb], together with recent advantages in Micro ElectroMechanical Systems and wireless communications, allow electronics to be so small and powerful that they can be integrated into any physical object (Figure 1.1). This observation opens up a whole new world of opportunities: clothes and furniture can be made smart, machine and construction monitoring can be automated, and accurate tracking of personnel and goods becomes feasible. The environment becomes sensitive and responsive to the presence of people and sympathetic to their needs. Distributed networks of small, intelligent, embedded devices provide us with information, communication and entertainment, and promise to make our future life easier and our surroundings more secure and pleasant. Different buzz words have been used to refer to this brave new world: “smart dust” [Kah99], “ubiquitous computing” [Win91], “pervasive computing” [Sat01], and “ambient intelligence” [Aar03, Phi] popped up in scientific and later also in popular literature.

The basic unit, which allows all these promising applications, is a microsensor node. Several of these microsensor nodes configure themselves into a wireless distributed network for collecting, processing, and disseminating wide ranges of complex data [Rag02, Aky02b]. The sensor node is typically made up out of a limited set of components, containing one or more sensors, a limited storage and control system, an energy subsystem, including the energy supply and energy management, and a wireless communication unit.