Resource Partitioning and User Association With Sleep-Mode Base Stations in Heterogeneous Cellular Networks

In this paper, we minimize the total energy used in a two-tier heterogeneous cellular network (HCN), through the optimization of resource partitioning and user association, assuming that both macro and small-cell base stations may be put into sleep mode. With resource partitioning, one tier of base stations can be put into sleep mode on a fraction of available time/frequency resources to reduce network power consumption. A user association scheme is adopted to alleviate the SINR degradation due to severe inter-tier interference for users close to tier boundaries. By deriving tractable throughput characterizations, we formulate the network-wide energy usage minimization problem and determine the optimal user association and resource partitioning strategies. The maximum achievable network coverage probabilities using the optimal strategies are also investigated. Numerical results show that the proposed resource allocation and user association scheme reduces network energy consumption and improves coverage probability in co-channel heterogeneous networks.