  Recently, the millimeter wave (mmWave) bands have been investigated as a
means to support the foreseen extreme data rate demands of next-generation
cellular networks (5G). However, in order to overcome the severe isotropic path
loss and the harsh propagation experienced at such high frequencies, a dense
base station deployment is required, which may be infeasible because of the
unavailability of fiber drops to provide wired backhauling. To address this
challenge, the 3GPP is investigating the concept of Integrated Access and
Backhaul (IAB), i.e., the possibility of providing wireless backhaul to the
mobile terminals. In this paper, we (i) extend the capabilities of the existing
mmWave module for ns-3 to support advanced IAB functionalities, and (ii)
evaluate the end-to-end performance of the IAB architecture through
system-level full-stack simulations in terms of experienced throughput and
communication latency. We finally provide guidelines on how to design optimal
wireless backhaul solutions in the presence of resource-constrained and
traffic-congested mmWave scenarios.
