User Association in Dense mmWave Networks based on Rate Requirements

Commonly considered user association frameworks in millimeter-wave communications are based on the sum rate maximization, and they essentially neglect user specific rate and service requirements. Furthermore, new features of millimeter-wave communications including spatial multiplexing, connectivity to multiple coordinated base stations and dense base station deployment are not considered. In this work, we propose a two-step optimization framework for single-shot user association in dense millimeter-wave networks which takes into account users' rate requirements, multi-connectivity, and hybrid transceiver architecture for spatial multiplexing. The proposed framework considers multiple RF chains at each base station and assigns them to different users that also have multiple RF chains for connectivity with more than one base station. In the first step, the objective of the user association is to maximize the number of users with satisfied rate requirements while minimizing network underutilization. In the second step, remaining RF chains are assigned to users, whose rate requirement has not been met, such that network sum rate is maximized. This is a novel problem formulation for user associate in millimeter-wave networks. We propose low complexity sub-optimal user association algorithms based on this formulation, numerically evaluate the optimal and sub-optimal solutions, and compare them to the conventional association approaches in terms of the number of associated users and network sum rate.