Introduction
Many applications of wireless sensor networks require a large set of sensors (potentially hundreds or thousands) to regularly report their readings to a central server to undertake off-line data analysis. These applications, for instance environmental or structural monitoring, HVAC systems, or object tracking, also require the sensors to be running for as long a period of time as possible. Limited energy ressources available on a sensor module (a.k.a. mote) drive the need for efficient scheduling of sensing and networking activities, so as to maximize the application lifetime.