  The impact of buildings blockage on the UAVs communications in different UAVs
heights is studied, when UAVs fly in a given rectangular urban area. This paper
analyzes the properties of blockage behavior of communication links between
UAVs from layers of different heights, including two main stochastic
properties, namely the blockage (or LOS) probabilities, and the state
transition models (birth-death process of LOS propagation). Based on stochastic
geometry methods, the relation between LOS probability and the parameters of
the region and the buildings is derived and verified with simulations.
Furthermore, based on the simulations of the channel state transition process,
we also find the birth-death process can be modeled as a distance continuous
Markov process, and the transition rates are also extracted with their relation
with the height of layers.
