2. Different challenges

To make these wireless networks work effectively, a number of challenges have to be met. A sensor is small and inexpensive. It has little memory capacity, so it can't carry a complete map of the network, nor can it learn throughout its lifetime to avoid saturating its memory. It doesn't have much computing power, so it can't perform complicated calculations such as integrals or cosines. It has a limited source of energy, which needs to be conserved as much as possible to ensure that the network lives as long as possible. Finally, depending on the application, sensors can be mobile (if affixed to animals or vehicles, for example), which introduces a network topology that is constantly dynamic and not always predictable.

The greatest challenges are of course linked to the self-organization of these networked sensors, and to the primitives required to retrieve the...