  To allow flexible and cost-efficient network densification and deployment,
the integrated access and backhaul (IAB) was recently standardized by the third
generation partnership project (3GPP) as part of the fifth-generation new radio
(5G-NR) networks. However, the current standardization only defines the IAB for
the terrestrial domain, while non-terrestrial networks (NTNs) are yet to be
considered for such standardization efforts. In this work, we motivate the use
of IAB in NTNs, and we discuss the compatibility issues between the 3GPP
specifications on IAB in 5G-NR and the satellite radio regulations. In
addition, we identify the required adaptation from the 3GPP and/or satellite
operators for realizing an NTN-enabled IAB operation. A case study is provided
for a low earth orbit (LEO) satellite-enabled in-band IAB operation with
orthogonal and non-orthogonal bandwidth allocation between access and
backhauling, and under both time- and frequency-division duplex (TDD/FDD)
transmission modes. Numerical results demonstrate the feasibility of IAB
through satellites, and illustrate the superiority of FDD over TDD
transmission. It is also shown that in the absence of precoding, non-orthogonal
bandwidth allocation between the access and the backhaul can largely degrades
the network throughput.
