Range assignment for power optimization in load-coupled heterogeneous networks

We consider the problem of transmission energy optimization via range assignment for Low Power Nodes (LPNs) in Long Term Evolution (LTE) Heterogeneous Networks (HetNets). The optimization is subject to the load coupling model, where the cells interfere with one another. Each cell provides data service for its users so as to maintain a target Quality-of-Service (QoS). We prove that, irrespective the presence of maximum power limit or its value, operating at full load is optimal. We perform energy minimization by optimizing the association between User Equipments (UEs) and cells via selecting cell-specific offsets on LPNs. Moreover, the optimization problem is proved to be NP-hard. We propose a tabu search algorithm for offset optimization (TSO). For each offset, TSO computes the optimal power solution such that all cells operate at full load. Numerical results demonstrate the significant performance improvement of TSO on optimizing the sum transmission energy, compared to the conventional solution where uniform offset is used for all LPNs.