  We consider an integrated access and backhaul (IAB) node operating in
full-duplex (FD) mode. We analyze simultaneous transmission from the New Radio
gNB to the IAB node on the backhaul uplink, IAB node to a user equipment (UE)
on the access downlink, and IAB transmitter to the IAB receiver on the
self-interference (SI) channel. Our contributions include (1) a low complexity
algorithm to jointly design the hybrid analog/digital beamformers for all three
nodes to maximize the sum spectral efficiency of the access and backhaul links
by canceling SI and maximizing received power; (2) derivation of all-digital
beamforming and spectral efficiency upper bound for use in benchmarking; and
(3) simulations to compare full vs. half duplex modes, hybrid vs. all-digital
beamforming algorithms, proposed hybrid vs. conventional beamforming
algorithms, and spectral efficiency upper bound. In simulations, the proposed
algorithm shows significant reduction in SI power and increase in sum spectral
efficiency.
