On the Degrees of Freedom of the Cellular Network

In this paper, we consider the problem of the capacity limits of the cellular network, which is modeled as a network consisting of two mutually interfering multiple access channel with multiple antennas at each receiver (e.g. the Base Station). By developing a tight outerbound (in the sense of DoF) and an achievable scheme which exploits the idea of interference alignment, we are able to exactly characterize the degrees of freedom (DoF) of the network when the channel coefficients are time- or frequency-varying, which is, the DoF per cell is KM/K + min (M,K) (where M and K denotes the number of receiver antennas and number of users in a cell, respectively). From the DoF result, it can be observed that when the number of users is large, we can nearly achieve the interference-free DoF of a multi-antenna cell!