Profile of the modulation instabilities in different environments

The coverage area of an WIMAX system operating with 2.5 GHz is analyzed according to the modulation used. The modulation of an antenna depends on the value of the power received and the attenuation of this power leads to regions of different modulations. We used the shadowing model to describe this attenuation. In this model, the different environments are described by different beta values and the distribution of the power values around the mean value is described by a statistical variable. When this distribution is associated with the antenna modulation we can notice that there will be regions associated with two kinds of modulations, leading to instabilities. Furthermore, we noticed that this instability is associated with the beta value: in outdoor environments the instability covers a larger region than in indoor environments.