Cooperation alignment for distributed interference management

In this work, we consider an interference channel model in which K receivers cooperatively attempt to decode their intended messages locally by processing and sharing information through limited capacity backhaul links. In contrast to distributed antenna architectures that have been proposed in the literature, where data processing is utterly performed in a centralized fashion, the model considered in this paper aims to capture the essence of decentralized (over the cloud) processing, allowing for a more general class of interference management strategies. Focusing on the three-user case, we characterize the fundamental tradeoff between the achievable communication rates and the corresponding backhaul cooperation rate, in terms of degrees of freedom (DoF). Surprisingly, we show that the optimum communication-cooperation tradeoff remains the same when we move from two-user to three-user interference channels. In the absence of cooperation, this is due to interference alignment, which keeps the fraction of communication dimensions wasted for interference unchanged. When backhaul cooperation is available, we develop a new idea that we call cooperation alignment, which guarantees that the average (per user) backhaul load remains the same as we increase the number of users.