How D2D communication influences energy efficiency of small cell network with sleep scheme

In this paper, we consider the potential influences on energy efficiency when Device to Device (D2D) communication is introduced to small cell network with sleep scheme. To begin with, we obtain the optimal sleep strategy for small cells, then we define parameters sleep ratio (SR) and maximum sleeping cell (MSC) to describe system dormant situation. Furthermore, parameters λ and θ are defined to indicate the D2D offloading ratio as well as geographic distribution of D2D users. We show that D2D communication will always be energy beneficial to the base station side. However, when considering the overall energy consumption (users included), D2D Assisted Sleep Mode (DASM) may cost more energy than D2D Forbidden Sleep Mode (DFSM). We demonstrate that to obtain the λ scope where DASM is energy efficient, it equals to calculate the positive range of a quadratic function f(θ,λ). Therefore, D2D scheduling scheme should be self-adaptive according to the f(θ, λ) curve to keep the network energy efficient. The analysis method in this paper should be universal regardless of the specific system models.