An Energy Efficient Cell Selection Framework for Femtocell Networks With Limited Backhaul Link Capacity

Dense deployment of femtocells improves the network capacity without significantly burdening the operator with huge capital and operational expenditure. However, extremely dense deployment of femtocells comes with the cost of increased cochannel interference and higher energy consumption. Additionally, femtocells burden the existing ADSL/broadband lines by using them as backhaul to connect to the cellular core network. A cell selection scheme defines the criteria on which mobile users associate themselves with base stations. This criteria may include received signal quality, available bandwidth, and energy consumption. Hence, cell selection plays a crucial role in system capacity, load balancing, and energy consumption. In this paper, we provide a framework for femtocell deployment in the urban scenario where interference, energy consumption, and backhaul capacity are major concerns. We first model the energy consumption of base stations, user equipment, and wired backhaul links. Then, we propose an efficient spectrum and power allocation technique to mitigate interference and improve bandwidth utilization in the uplink and downlink, respectively. Finally, we suggest a novel QoS-aware cell selection scheme that assigns mobile users to femtocells considering the capacity improvement obtained per unit increase in energy consumption. The proposed cell selection scheme incorporates the energy consumption of the wired backhaul links and their limited capacity constraint into the cell selection criteria. Our proposed spectrum and power allocation technique, when combined with the proposed cell selection, leads to a significant reduction in energy consumption without any deterioration in the system capacity. Simulation results confirm that our proposed framework has the potential to significantly improve the energy efficiency of the network.