Cell-free Massive multiple-input multiple-output
(MIMO) ensures ubiquitous communication at high spectral
efficiency (SE) thanks to increased macro-diversity as compared
cellular communications. However, system scalability and performance
are limited by fronthauling traffic and interference.
Unlike conventional precoding schemes that only suppress intra-cell
interference, full-pilot zero-forcing (fpZF), introduced in [1],
actively suppresses also inter-cell interference, without sharing
channel state information (CSI) among the access points (APs).
In this study, we derive a new closed-form expression for
the downlink (DL) SE of a cell-free Massive MIMO system
with multi-antenna APs and fpZF precoding, under imperfect
CSI and pilot contamination. The analysis also includes max-min
fairness DL power optimization. Numerical results show
that fpZF significantly outperforms maximum ratio transmission
scheme, without increasing the fronthauling overhead, as long as
the system is sufficiently distributed.