Increasing Energy Efficiency via Transmit Power Spreading in Dense Femto Cell Networks

Adding Femto Base Stations (FBSs) has become a common approach toward capacity and coverage enhancements in the current cellular networks. Moreover, rapidly growing demand for capacity results in ultradense deployments of FBS and these skyrocket the energy consumption of the cellular networks. Thus, increasing Energy Efficiency (EE) has gained great importance in small cell research to minimize the impact on the environment. In this paper, we first model a problem to maximize the EE of an FBS network. Then, we suggest a heuristic approach to calculate the transmission power of FBSs in terms of spreading factors that maximize the EE of the network while protecting User Equipments’ (UEs’) signal to interference plus noise ratio threshold and quality of service requirements. Moreover, transmit power spreading decreases energy consumption and co-tier interference among neighboring FBSs. The proposed approach does not require any feedback from neighboring FBSs but depends on the channel quality indicator from its associated UEs. The study is carried out in two different scenarios: outdoor with open access mode FBSs and indoor with closed access mode FBSs. The simulation results indicate increase in FBS network EE and energy saving without any loss in throughput. The results depict up to $54.2\%$ gain in EE in indoor scenario with closed access FBSs and up to $7.2\%$ gain in EE in outdoor scenario with open access FBSs.