Nowadays an extensive attention is given to UAVs and their applications. One applications category can be underserved by hybrid systems composed from UAV and ground WSN. UAV can gather data from ground WSN which, at its turn could be initially deployed by the UAV itself.
Ground nodes are limited in battery life, therefore, an efficient communication algorithm will improve their energy autonomy. This paper presents an algorithm with this purpose which makes use of directional antenna for ground nodes together with a novel communication synchronization mechanism. The paper also presents the necessary assumptions related to directional antennas.