Impact of Densification on Energy Efficiency in Wireless Access Networks

Mobile communication networks alone consume 0.5 percent of the global energy today. Rapidly growing demand for capacity will further increase the energy consumption. Thus, improving energy efficiency has recently gained great interest within the research community not only for environmental awareness but also to lower the operational cost of network operators. Base station deployment strategy is one of the key challenges to be addressed for fulfilling the future capacity demand in an energy efficient manner. In this paper, we investigate the relationship between energy efficiency and densification with regard to network capacity requirement. To this end, we refine the base station power consumption model such that the parameters are determined by the maximum transmit power and develop a simple analytical framework to derive the optimum transmit power that maximizes energy efficiency for a certain capacity target. Our framework takes into account interference, noise and backhaul power consumption. Numerical results show that deployment of smaller cells significantly reduces the base station transmit power, and thus shifts the key elements of energy consumption to idling and backhauling power. Network densification can only be justified when capacity expansion is anticipated.