We report results from extensive measurements based study to understand the shadow fading correlations. We have particularly studied and analyzed common assumptions done in literature for shadow fading, which is typically modeled as a spatially correlated Gaussian random process in the logarithmic scale. We show that these assumptions, starting from the Gaussianity of the radio propagation environment, do not always hold. We then discuss the assumptions regarding spatial correlations, usually taken to depend only on the distance between the points and assuming that these correlations remain the same throughout the area under consideration. This is done by comparing received power measurements for two different propagation environments, an urban and a sub-urban one, against simulated values based on typical theoretical assumptions. We conclude by explaining how these assumptions should be carefully taken into account and how they can affect simulation results and the performance of applications.
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