  In a multi-user scenario where users belong to different operators, any
interference mitigation method needs unavoidably some degree of cooperation
among service providers. In this paper we propose a cooperation strategy based
on the exchange of mutual interference among operators, rather than of decoded
data, to let every operator to recover an augmented degree of diversity either
for channel estimation and multi-user detection. In xDSL scenario where
multiple operators share the same cable binder the interference-cooperation
(IC) approach outperforms data-exchange methods and preserves to certain degree
the privacy of the users as signals can be tailored to prevent each operator to
infer parameters (channel and data) of the users from the other operators.
  The IC method is based on Expectation Maximization estimation shaped to
account for the degree of information that each operator can exchange with the
others during the two steps of multi-user channel estimation and multi-user
detection. Convergence of IC is guaranteed into few iterations and it does not
depend on the structure of the interference. IC performance attains those of
centralized receivers (i.e., one fusion-center that collects all the received
signals from all the users/operators), with some loss when in heavily
interfered multi-user channel such as in twisted-pair communications allocated
beyond 50-100MHz spectrum.
