  Wireless sensors networks performance are strictly related to the medium
access mechanism. An effective one, require non-conventional paradigms for
protocol design due to several constraints. An adequate equilibrium between
communication improvement and data processing capabilities must be
accomplished. To achieve low power operation, several MAC protocols already
proposed for WSN. The aim of this paper is to survey and to analyze the most
energy efficient MAC protocol in order to categorize them and to compare their
performances. Furthermore we have implemented some of WSN MAC protocol under
OMNET++ with the purpose to evaluate their performances.
