  Wireless communication highly depends on the cellular ground base station
(GBS). A failure of the cellular GBS, fully or partially, during natural or
man-made disasters creates a communication gap in the disaster-affected areas.
In such situations, public safety communication (PSC) can significantly save
the national infrastructure, property, and lives. Throughout emergencies, the
PSC can provide mission-critical communication and video transmission services
in the affected area. Unmanned aerial vehicles (UAVs) as flying base stations
(UAV-BSs) are particularly suitable for PSC services as they are flexible,
mobile, and easily deployable. This manuscript considers a multi-UAV-assisted
PSC network with an observational UAV receiving videos from the affected area's
ground users (AGUs) and transmitting them to the nearby GBS via a relay UAV.
The objective of the proposed study is to maximize the average utility of the
video streams generated by the AGUs upon reaching the GBS. This is achieved by
optimizing the positions of the observational and relay UAVs, as well as the
distribution of communication resources, such as bandwidth, and transmit power,
while satisfying the system-designed constraints, such as transmission rate,
rate outage probability, transmit power budget, and available bandwidth. To
this end, a joint UAVs placement and resource allocation problem is
mathematically formulated. The proposed problem poses a significant challenge
for a solution. Considering the block coordinate descent and successive convex
approximation techniques, an efficient iterative algorithm is proposed.
Finally, simulation results are provided which show that our proposed approach
outperforms the existing methods.
