Energy efficiency analysis in device-to-device communication underlaying cellular networks

The energy efficiency (EE) has become an increasingly important issue in wireless communications because of the increasing energy cost and concern over the environmental issues. In this paper, the EE is focused and analyzed in device-to-device (D2D) communication underlaying cellular networks when the resources are shared by D2D and cellular users in three modes, namely, Non-Orthogonal Sharing mode (NOS), Orthogonal Sharing mode (OS), and Cellular Mode (CM). In addition, energy efficient power allocation schemes in the three modes are discussed under the maximum transmission power constraint. Numerical simulations are performed in a single-cell environment and the EE performance in these modes are simulated by varying three system parameters: a) the location of the cellular user, b) the distance between D2D users, c) the distance between the D2D pair and the Base Station (BS). The results demonstrate that it is more preferable that the D2D users communicate with each other directly in terms of the energy efficiency.