Wireless Sensor Network is a large-scale network of resource-constrained (energy, memory and processing) sensor nodes that are deployed at different locations, in order to monitor physical or environmental conditions. A design problem is that a lot of sensor node platforms exist, and many MAC-layer and protocol configurations can be used. It is also difficult to explore design space to check for feasibility at early design stage. Focusing on widely used IEEE 802.15.4 standard, our simulator-called IDEA1-enables designers to check, through an easy to use graphical environment, the possible use of actual and future systems. That SystemC simulator is also composed of a library (that is periodically improved) of electrical devices and software stacks. It permits to find which hardware system to choose and which software to develop to best fit application requirements.