User association and wireless backhaul bandwidth allocation for 5G heterogeneous networks in the millimeter-wave band

Abstract

The user association and wireless backhaul bandwidth allocation for a two-tier heterogeneous network (HetNet) in the millimeter wave (mmWave) band is proposed in this article. The two-tier HetNet is built up with a macro base station (MBS) and several small cell SBSs, where the MBS is assumed to be equipped with large-scale antenna arrays but the SBSs only have single-antenna capability and they rely on the wireless link to the MBS for backhaul. The sum of logarithmic user rate, which is established according to the result of multi-user Multiple Input Multiple Output (MIMO) downlink employing Zero-Force Beamforming (ZFBF), is chosen as the network utility for the objective function. And a distributed optimization algorithm based on primal and dual decomposition is used to jointly optimize the user association variable x _j,i and the wireless backhaul bandwidth factor β. Simulation results reveal that the distributed optimization algorithm jointly optimizing two variables outperforms the conventional SINR-based user association strategies.