**2.2. WSN node structure**

The basic structure of WSN is that it is composed of sensor nodes and base stations. Sensor nodes, viewed as communicating parties in WSN, are more than simple sensing devices. In fact, every node holds an embedded system that performs three main functions:


Looking at the above functions, the requirements on the sensor hardware will be as follows [11,12,21,22,23,17]:


processing unit of a smart dust mote prototype is a 4 MHz Atmel AVR8535 microcontroller with 8 KB instruction flash memory, 512 bytes RAM and 512 bytes EEPROM [24]. TinyOS operating system is used on this processor, which has 3500 bytes OS code space and 4500 bytes available code space

