  Benefiting from the usage of the high-frequency band, utilizing part of the
large available bandwidth for wireless backhauling is feasible without
considerable performance sacrifice. In this context, integrated access and
backhaul (IAB) was proposed by 3GPP to reduce the fiber optics deployment cost
of 5G and beyond networks. In this paper, we first give a brief introduction of
IAB based on the 3GPP release. After that, we survey existing research on IAB
networks, the integrations of IAB to cache-enabled network, optical
communication transport network, and the non-terrestrial network. Finally, we
discuss the challenges and opportunities that might arise while developing and
commercializing IAB networks.
