  Unmanned aerial vehicles (UAVs) are widely exploited in environment
monitoring, search-and-rescue, etc. However, the mobility and short flight
duration of UAVs bring challenges for UAV networking. In this paper, we study
the UAV networks with n UAVs acting as aerial sensors. UAVs generally have
short flight duration and need to frequently get energy replenishment from the
control station. Hence the returning UAVs bring the data of the UAVs along the
returning paths to the control station with a store-carry-and-forward (SCF)
mode. A critical range for the distance between the UAV and the control station
is discovered. Within the critical range, the per-node capacity of the SCF mode
is O(n/log n) times higher than that of the multi-hop mode. However, the
per-node capacity of the SCF mode outside the critical range decreases with the
distance between the UAV and the control station. To eliminate the critical
range, a mobility control scheme is proposed such that the capacity scaling
laws of the SCF mode are the same for all UAVs, which improves the capacity
performance of UAV networks. Moreover, the delay of the SCF mode is derived.
The impact of the size of the entire region, the velocity of UAVs, the number
of UAVs and the flight duration of UAVs on the delay of SCF mode is analyzed.
This paper reveals that the mobility and short flight duration of UAVs have
beneficial effects on the performance of UAV networks, which may motivate the
study of SCF schemes for UAV networks.
