  Terrestrial-satellite networks are envisioned to play a significant role in
the sixth-generation (6G) wireless networks. In such networks, hot air balloons
are useful as they can relay the signals between satellites and ground
stations. Most existing works assume that the hot air balloons are deployed at
the same height with the same minimum elevation angle to the satellites, which
may not be practical due to possible route conflict with airplanes and other
flight equipment. In this paper, we consider a TSN containing hot air balloons
at different heights and with different minimum elevation angles, which creates
the challenge of non-uniform available serving time for the communication
between the hot air balloons and the satellites. Jointly considering the
caching, computing, and communication (3C) resource management for both the
ground-balloon-satellite links and inter-satellite laser links, our objective
is to maximize the network energy efficiency. Firstly, by proposing a tapped
water-filling algorithm, we schedule the traffic to relay among satellites
according to the available serving time of satellites. Then, we generate a
series of configuration matrices, based on which we formulate the relationship
of relay time and the power consumption involved in the relay among satellites.
Finally, the integrated system model of TSN is built and solved by geometric
programming with Taylor series approximation. Simulation results demonstrate
the effectiveness of our proposed scheme.
