  In this work, we study the problem of the optimal dissemination of channel
state information (CSI) among K spatially distributed transmitters (TXs)
jointly cooperating to serve K receivers (RXs). One of the particularities of
this work lies in the fact that the CSI is distributed in the sense that each
TX obtains its own estimate of the global multi-user MIMO channel with no
further exchange of information being allowed between the TXs. Although this is
well suited to model the cooperation between non-colocated TXs, e.g., in
cellular Coordinated Multipoint (CoMP) schemes, this type of setting has
received little attention so far in the information theoretic society. We study
in this work what are the CSI requirements at every TX, as a function of the
network geometry, to ensure that the maximal number of degrees-of-freedom (DoF)
is achieved, i.e., the same DoF as obtained under perfect CSI at all TXs. We
advocate the use of the generalized DoF to take into account the geometry of
the network in the analysis. Consistent with the intuition, the derived DoF
maximizing CSI allocation policy suggests that TX cooperation should be limited
to a specific finite neighborhood around each TX. This is in sharp contrast
with the conventional (uniform) CSI dissemination policy which induces CSI
requirements that grow unbounded with the network size. The proposed CSI
allocation policy suggests an alternative to clustering which overcomes
fundamental limitations such as (i) edge interference and (ii) unbounded
increase of the CSIT requirements with the cluster size. Finally, we show how
finite neighborhood CSIT exchange translates into finite neighborhood message
exchange so that finally global interference management is possible with only
local cooperation
