  With the increasing network densification, it has become exceedingly
difficult to provide traditional fiber backhaul access to each cell site, which
is especially true for small cell base stations (SBSs). The increasing maturity
of millimeter wave (mmWave) communication has opened up the possibility of
providing high-speed wireless backhaul to such cell sites. Since mmWave is also
suitable for access links, the third generation partnership project (3GPP) is
envisioning an integrated access and backhaul (IAB) architecture for the fifth
generation (5G) cellular networks in which the same infrastructure and spectral
resources will be used for both access and backhaul. In this paper, we develop
an analytical framework for IAB-enabled cellular network using which we provide
an accurate characterization of its downlink rate coverage probability. Using
this, we study the performance of two backhaul bandwidth (BW) partition
strategies, (i) equal partition: when all SBSs obtain equal share of the
backhaul BW, and (ii) load-based partition: when the backhaul BW share of an
SBS is proportional to its load. Our analysis shows that depending on the
choice of the partition strategy, there exists an optimal split of access and
backhaul BW for which the rate coverage is maximized. Further, there exists a
critical volume of cell-load (total number of users) beyond which the gains
provided by the IAB-enabled network disappear and its performance converges to
that of the traditional macro-only network with no SBSs.
