  The number of disasters has increased over the past decade where these
calamities significantly affect the functionality of communication networks. In
the context of 6G, airborne and spaceborne networks offer hope in disaster
recovery to serve the underserved and to be resilient in calamities. Therefore,
this paper surveys the state-of-the-art literature on post-disaster wireless
communication networks and provides insights for the future establishment of
such networks. In particular, we first give an overview of the works
investigating the general procedures and strategies for counteracting any
large-scale disasters. Then, we present the possible technological solutions
for post-disaster communications, such as the recovery of the terrestrial
infrastructure, installing aerial networks, and using spaceborne networks.
Afterward, we shed light on the technological aspects of post-disaster
networks, primarily the physical and networking issues. We present the
literature on channel modeling, coverage and capacity, radio resource
management, localization, and energy efficiency in the physical layer and
discuss the integrated space-air-ground architectures, routing,
delay-tolerant/software-defined networks, and edge computing in the networking
layer. This paper also presents interesting simulation results which can
provide practical guidelines about the deployment of ad hoc network
architectures in emergency scenarios. Finally, we present several promising
research directions, namely backhauling, placement optimization of aerial base
stations, and the mobility-related aspects that come into play when deploying
aerial networks, such as planning their trajectories and the consequent
handovers.
