Energy-Efficient User Association in HetNets: An Evolutionary Game Approach

The rising environmental awareness and the exponential growth of capacity demand have made energy efficiency an important issue to be addressed by cellular network operators. In this paper, an energy-efficient user association scheme is proposed for heterogeneous networks (HetNets) using an evolutionary game theoretic approach to maximize the energy efficiency of the whole network with the consideration of fairness among users. The dynamics of user association is formulated as the process of an evolutionary game. Each user in HetNets is modeled as a player who adjusts and chooses its base station (BS) selection strategy in order to ensure its payoff no less than the average payoff of the population. In the proposed evolutionary game based user association scheme, the learning process is formulated as replicator dynamics. The user association process ends when the system reaches an equilibrium state, where all players get the evolutionary stability strategy in the game. Simulation results show that the proposed user association scheme significantly improves both energy efficiency and user fairness compared to the conventional reference signal receiving power (RSRP) based user association scheme. Comparing with Nash Bargaining Solution (NBS) based user association scheme, the proposed scheme achieves comparable energy efficiency with reduced computation complexity and improved user fairness.