User Association Based Cooperative Energy-Saving Mechanism in Heterogeneous 5G Access Networks

To reduce the energy consumption in heterogeneous 5G access networks, we propose a cooperative energy-saving mechanism based on user association (UA-CESM). Joint processing (JP) and centralized resource scheduling are introduced into the mechanism to solve inadequate coverage problem caused by base-station (BS) dormancy by means of cooperative BS selection and BS state control. First, the number of candidate dormant BSs is obtained on the basis of statistical traffic valley. Second, for heterogeneous cellular networks with relays, a BS selection model is designed to find cooperative BS set and a candidate dormant BS group. Finally, an energy-saving optimization strategy based on bipartite graph is proposed to realize user association from candidate dormant BSs to appropriate cooperative BSs. The simulation results show that the average rate of edge users is increased by 92.5%, and the coverage can be compensated without extra transmission power in the proposed mechanism.