Base Station Operation and User Association in HetNets: Complexity and Heuristic Algorithms

This paper studies the base station operation and association problem for energy-efficient heterogeneous cellular networks. The objective is to find a set of base stations to activate and to associate users to base stations under minimum rate requirements. The problem is formulated as a nonconvex program and is shown to be NP-hard. Then, the problem is reduced to a base station operation problem where the association of users becomes straightforward. Based on this reduction, a brute force algorithm is developed and its complexity is discussed. To solve the problem efficiently in polynomial-time, an heuristic algorithm is proposed. Simulation results illustrate the performance of the proposed algorithm and compares it to the brute force algorithm and a benchmark algorithm.