  We consider a scalable user-centric wireless network with dynamic cluster
formation as defined by Bj\"ornsson and Sanguinetti. After having shown the
importance of dominant channel subspace information for uplink (UL) pilot
decontamination and having examined different UL combining schemes in our
previous work, here we investigate precoding strategies for the downlink (DL).
Distributed scalable DL precoding and power allocation methods are evaluated
for different antenna distributions, user densities and UL pilot dimensions. We
compare distributed power allocation methods to a scheme based on a particular
form of UL-DL duality which is computable by a central processor based on the
available partial channel state information. The new duality method achieves
almost symmetric "optimistic ergodic rates" for UL and DL while saving
considerable computational complexity since the UL combining vectors are reused
as DL precoders.
