Today, most of commercial wireless sensor network
solutions are based on the IEEE 802.15.4 standard, which
defines the physical and MAC layers for low-power, low
bit rate communications in wireless personal area networks
(WPAN) [23]. IEEE 802.15.4 does not include specifications
on the higher layers of the protocol stack, which is
necessary for the seamless integration of sensor nodes into
the Internet. This is a difficult task for several reasons, the
most important are given below: