Joint Uplink-Downlink Cooperative Interference Management With Flexible Cell Associations

We study information theoretic models of interference networks that consist of K Base Station (BS) - Mobile Terminal (MT) pairs. BS i is connected to the MTs with indices in the se t{i,i+1,.. .,i+L}. We fix the value of Land study the per user Degrees of Freedom (puDoF) in large networks. We assume that each MT can be associated with Nc BSs, and these associations are determined by a cloud-based controller that has a global view of the network. An MT has to be associated with a BS, for the BS to transmit its message in the downlink, or have its decoded message in the uplink. We propose puDoF inner bounds for arbitrary values of L for the uplink, and prove their optimality when only zero-forcing schemes are allowed. We then introduce new achievable average uplink-downlink puDoF values, and show their optimality for the range when N
_c
≤ L1/2 and when we restrict our attention to zero-forcing schemes. Additionally, for the remaining range, we characterize the optimal downlink scheme when the uplink-optimal associations are used. Finally, we show that the proposed scheme is information theoretically optimal for Wyner's linear interference network.