  The degrees of freedom (DoF) available for communication provides an
analytically tractable way to characterize the information-theoretic capacity
of interference channels. In this paper, the DoF of a K-user interference
channel is studied under the assumption that the transmitters can cooperate via
coordinated multi-point (CoMP) transmission. In [1], the authors considered the
linear asymmetric model of Wyner, where each transmitter is connected to its
own receiver and its successor, and is aware of its own message as well as M-1
preceding messages. The per user DoF was shown to go to M/(M+1) as the number
of users increases to infinity. In this work, the same model of channel
connectivity is considered, with a relaxed cooperation constraint that bounds
the maximum number of transmitters at which each message can be available, by a
cooperation order M. We show that the relaxation of the cooperation constraint,
while maintaining the same load imposed on a backhaul link needed to distribute
the messages, results in a gain in the DoF. In particular, the asymptotic limit
of the per user DoF under the cooperation order constraint is (2M)/(2M+1) .
Moreover, the optimal transmit set selection satisfies a local cooperation
constraint. i.e., each message needs only to be available at neighboring
transmitters. [1] A. Lapidoth, S. Shamai (Shitz) and M. A. Wigger, "A linear
interference network with local Side-Information," in Proc. IEEE International
Symposium on Information Theory (ISIT), Nice, Jun. 2007.
