An Energy-efficient Macro-micro Hierarchical Structure with Resource Allocation in OFDMA Cellular Systems

Macro-micro networks, as typical hierarchical networks, are advanced in increasing the network capacity as well as in decreasing the network energy consumption during peak hours. However, the fluctuation of traffic load over space and time brings challenges and opportunities in energy saving. In this paper, we develop both resource optimization schemes and hierarchical cell structure switchings, which are rarely considered together, to lower the energy consumption. We first proposed a radio resource allocation scheme to minimize energy consumption while satisfying given rate requirements in a single cell. Furthermore, switching between different hierarchical cell structures, which can be accomplished by adjusting the coverage areas of base stations and switching off the micro stations, is considered to adapt the changing traffic load. Simulation results show that our structure can meet the transmission rate requirements and simultaneously decrease the energy consumption significantly.