  Many studies have tried to evaluate wireless networks and especially the IEEE
802.15.4 standard. Hence, several papers have aimed to describe the
functionalities of the physical (PHY) and medium access control (MAC) layers.
They have highlighted some characteristics with experimental results and/or
have attempted to reproduce them using theoretical models. In this paper, we
use the first way to better understand IEEE 802.15.4 standard. Indeed, we
provide a comprehensive model, able more faithfully to mimic the
functionalities of this standard at the PHY and MAC layers. We propose a
combination of two relevant models for the two layers. The PHY layer behavior
is reproduced by a mathematical framework, which is based on radio and channel
models, in order to quantify link reliability. On the other hand, the MAC layer
is mimed by an enhanced Markov chain. The results show the pertinence of our
approach compared to the model based on a Markov chain for IEEE 802.15.4 MAC
layer. This contribution allows us fully and more precisely to estimate the
network performance with different network sizes, as well as different metrics
such as node reliability and delay. Our contribution enables us to catch
possible failures at both layers.
