The Bridge - Issue 3, 2021 - 25

Feature
Facilitating Satellite-Airborne-Balloon-Terrestrial
Integration for Dynamic and Infrastructure-less Networks
ground users' quality of service (QoS). The work
proposed a game theory model based on a selforganized
model which maximizes the data rate of
ground users. The work considers the HAPs as selforganized
and rational players. The authors in [6]
proposed some techniques for trajectory optimization
where HAPs are equipped with solar panels. The work
proposed two solutions based on a heuristic greedy
algorithm and real-time and low complexity solution.
The objective is to minimize the consumed energy,
that is constrained by the harvested energy amount,
by optimizing the trajectory of the HAPs. Improving
the overall system data rate is also limited by another
key factor in this integration system. For instance, the
authors in [8] proposed to use orthogonal frequency
division multiple access (OFDMA) for multicast
technique to optimize the HAPs' transmit powers,
transmission time slots, and resource block channels
aiming to maximize the total ground user data rate. In
other words, they maximized the number of users that
received the requested multicast streams within the
HAP's service area for a given OFDMA slot frame. The
achieved enhancement in multiple HAPs' capacities
is discussed in [9], where the authors showed that by
exploiting the directionality of user antennas, HAPs can
offer spectral efficiency. This work also discussed how
multiple HAPs can take the advantages of directionality
by sharing the same frequency bandwidth. In a recent
work of ours [10], we proposed a downlink resourceallocation
solution of integrated satellites, HAPs, and
GBSs based on OFDMA to maximize user throughput
considering back-hauling and access-link constraints. In
another work [11], we proposed using TBs connected
with optical fibers as back- hauling stations to support
ground users.
Equipping aerial relay stations with free-space-optical
(FSO) transceivers is a tipping point. Limited research
has proposed equipping aerial relay stations (i.e.,
HAPs and TBs) with FSO transceivers [12, 13]. The
overview of equipping HAPs with optical transmitters
has been discussed in [12]. The work shows that
several Gbps data throughput can be achieved by
using leaser FSO beams. In contrast to this approach,
closed form expressions for bit-error-rate and average
capacity were derived using multiple hop FSO
transmitters in the stratosphere region [13]. However,
all the previous works did not consider managing the
resource allocations in a satellite-airborne-balloonterrestrial
network integration while maintaining the
FSO communication links, nor did they consider issues
of back-hauling and access-link communications.
II. INTEGRATION WITH HYBRID FSO/RF
A. Integration of Aerial RelayStations
Deployment of aerial relay stations in remote, large
geographical infrastructure-less areas with grid power
limitations can be a potential solution to provide
wireless uplink and downlink services to ground
users as shown in Figure 1. Working as relays or
intermediate nodes, aerial stations can maintain the
wireless connectivity by broadcasting the uplink and
downlink signals. Aerial relay stations not only enhance
the uplink and downlink signals but also create a new
dimension to next-generation wireless networks and
service provisioning. In September 2017, Hurricane
Irma (Category 4 Hurricane) hit Florida and damaged
a significant percentage of cellular GBSs. For example,
in some counties in Miami city, Irma caused more
than 50% of GBS failure for days after the hurricane.
Additionally, Irma knocked out power to more than 6.8
million people for several days/weeks [14]. In such
circumstances, aerial relay stations can reach such
affected areas because of their quick and dynamic
deployment [15].
Figure. 1: System model.
The success of deploying aerial relay stations in remote
or challenging areas depends mainly on two factors.
The first factor is the integration with ground users via
access link, while the second factor is the availability
and other parameters related to back-hauling links.
The efficient placement and resource management of
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The Bridge - Issue 3, 2021

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