  The next generations of mobile networks will be deployed as ultra-dense
networks, to match the demand for increased capacity and the challenges that
communications in the higher portion of the spectrum (i.e., the mmWave band)
introduce. Ultra-dense networks, however, require pervasive, high-capacity
backhaul solutions, and deploying fiber optic to all base stations is generally
considered to be too expensive for network operators. The 3rd Generation
Partnership Project (3GPP) has thus introduced Integrated Access and Backhaul
(IAB), a wireless backhaul solution in which the access and backhaul links
share the same hardware, protocol stack, and also spectrum. The multiplexing of
different links in the same frequency bands, however, introduces interference
and capacity sharing issues, thus calling for the introduction of advanced
scheduling and coordination schemes. This paper proposes a semi-centralized
resource allocation scheme for IAB networks, designed to be flexible, with low
complexity, and compliant with the 3GPP IAB specifications. We develop a
version of the Maximum Weighted Matching (MWM) problem that can be applied on a
spanning tree that represents the IAB network and whose complexity is linear in
the number of IAB-nodes. The proposed solution is compared with
state-of-the-art distributed approaches through end-to-end, full-stack
system-level simulations with a 3GPP-compliant channel model, protocol stack,
and a diverse set of user applications. The results show how that our scheme
can increase the throughput of cell-edge users up to 5 times, while decreasing
the overall network congestion with an end-to-end delay reduction of up to 25
times.
