  A key aspect of the fifth-generation wireless communication network will be
the integration of different services and technologies to provide seamless
connectivity. In this paper, we consider using massive multiple-input
multiple-output (mMIMO) to provide backhaul links to a dense deployment of
self-backhauling (s-BH) small cells (SCs) that provide cellular access within
the same spectrum resources of the backhaul. Through a comprehensive
system-level simulation study, we evaluate the interplay between access and
backhaul and the resulting end-to-end user rates. Moreover, we analyze the
impact of different SCs deployment strategies, while varying the time resource
allocation between radio access and backhaul links. We finally compare the
above mMIMO-based s-BH approach to a mMIMO direct access (DA) architecture
accounting for the effects of pilot reuse schemes, together with their
associated overhead and contamination mitigation effects. The results show that
dense SCs deployments supported by mMIMO s-BH provide significant rate
improvements for cell-edge users (UEs) in ultra-dense deployments with respect
to mMIMO DA, while the latter outperforms mMIMO s-BH from the median UEs'
standpoint.
