  Unlike terrestrial communications, unmanned aerial vehicle (UAV)
communications have some advantages such as line-of-sight (LoS) environment and
flexible mobility, but the interference will be still inevitable. In this
paper, we analyze the effect of interference on the UAV communications by
considering the LoS probability and different channel fadings for LoS and
non-line-of-sight (NLoS) links, affected by the elevation angle of
communication link. We then derive a closed-form outage probability in the
presence of interfering node for all the possible scenarios and environments of
main and interference links. After discussing the impacts of transmitting and
interfering node parameters on the outage probability, we show the existence of
the optimal height of UAV that minimizes the outage probability. We also show
NLoS environment can be better than LoS environment if the average received
power of interference is more dominant than that of transmitting signal in UAV
communications.
