In this paper, the authors consider a heterogeneous network consisting in several macro nodes and pico nodes. The goal is to associate users, belonging to this network, to one of the nodes, while maximizing the sum rate of all users. They also want to analyze the load balancing achieved by this association. Therefore, they develop a new theoretical framework to study cell association for the downlink of multi-cell networks and derive an upper bound on the achievable sum rate. They propose a dynamic cell association heuristic, which achieves performance close to optimal. Finally, they verify their results through numerical evaluations and implement the proposed heuristic in an LTE simulator to demonstrate its viability.