  Cellular networks equipped with mobile edge computing (MEC) servers can be
beneficial for unmanned aerial vehicles (UAVs) with limited onboard computation
power and battery life-time. In this paper, we compare energy consumption of a
UAV connected to cellular MEC servers in various possible scenarios such as
onboard/MEC processing or parallel computation. Using detailed 3GPP-based
modelings, we provide quantitative understanding of the most energy efficient
approach and its relation with communication technologies, computation factors,
and mobility parameters. Our findings show that, across the different
frequencies from sub-6GHz to THz bands, the mmWave cellular MEC network is more
energy efficient than UAV's onborad processing for a broader range of network
densities. Secondly, while the UAV propulsion power consumption is
non-decreasing function of velocity, the UAV movement cost yet can be optimized
to further provide remarkable energy savings as compared to hovering. Finally,
our results show that the most energy efficient approach can be obtained if
mobility of UAV is combined with efficient parallel onboard-MEC processing.
