  We consider a scalable user-centric wireless network with dynamic cluster
formation as defined by Bj\"ornsson and Sanguinetti. Several options for
scalable uplink (UL) processing are examined including: i) cluster size and SNR
threshold criterion for cluster formation; ii) UL pilot dimension; iii) local
detection and global (per cluster) combining. We use a simple model for the
channel vector spatial correlation, which captures the fact that the
propagation between UEs and RRHs is not isotropic. In particular, we define the
ideal performance based on ideal but partial CSI, i.e., the CSI that can be
estimated based on the users to antenna heads cluster connectivity. In
practice, CSI is estimated from UL pilots, and therefore it is affected by
noise and pilot contamination. We show that a very simple subspace projection
scheme is able to basically attain the same performance of perfect but partial
CSI. This points out that the essential information needed to pilot
decontamination reduces effectively to the dominant channel subspaces.
