The previous chapter considered the design concerns, to do with arrays of intelligent sensors, and the design of intelligent sensor nodes themselves. This chapter looks at the same components, but from the point of view of the system into which they are integrated, and the concerns of designing a viable system as a whole. This further elaboration is required since large, ad hoc networks are extremely complex. Chapter 9 covered what the network system had to do, but producing a system organisation that is actually capable of performing the tasks described requires some overall structuring abstractions, in order to tackle the complexity of the overall design. The question of what precisely these structuring abstractions should be is an active research topic in its own right, and in this chapter two different approaches to the matter are presented.

At this level, the concern is with the connectivity of the nodes, from a system point of view, rather than their position in space (although there must be a way to discover this). Rather than considering the sensor system as an array, the topic of interest is the behaviour of the system as a network, which is the hardware and software realisation of the array. The chapter starts by examining some of the proposed applications for such networks, in order to provide some context for the following discussion. System design abstractions fulfil a role as a working metaphor for the system designers, and must therefore be accessible and...