  In this article, a radio access system with a self-backhauling full-duplex
access node serving legacy half-duplex mobile devices is studied and analyzed.
In particular, it is assumed that the access node is using the same center
frequency for all the transmissions, meaning that also the backhauling is done
using the same frequency resources as the uplink and downlink transmissions. It
is further assumed that the access node has a massive array to facilitate
efficient beamforming and self-interference nulling in its own receiver. As a
starting point, the signal model for the considered access node is first
derived, including all the transmitted and received signals within the cell.
This is then used as a basis for obtaining the sum-rate expressions, which
depict the overall rates experienced by the mobile users that are served by the
access node. In addition, the data rate for the bi-directional backhaul link is
also derived, since the access node must be able to backhaul itself wirelessly.
The maximum achievable sum-rate is then determined by numerically solving an
optimization problem constructed from the data rate expressions. The
full-duplex scheme is also compared to two alternative transmission schemes,
which perform all or some of the transmissions in half-duplex mode. The results
show that the full-duplex capability of the access node is beneficial for
maximizing the sum-rate, meaning that a simple half-duplex transmission scheme
is typically not optimal. In particular, the highest sum-rate is usually
provided by a relay type solution, where the access node acts as a full-duplex
relay between the mobiles and the backhaul node.
