Energy-Efficient SWIPT-Empowered D2D Mode Selection

While mode selection has been envisioned as the most cost-effective way to address the interference issue in Device-to-Device (D2D) communications, existing works have been largely conducted without consideration of the energy depletion of devices. In this paper we investigate simultaneous wireless information and power transfer (SWIPT) empowered mode selection based on stochastic geometry. As a mean of solving it, system energy efficiency is formulated by determining the closed-form ergodic energy-harvested and ergodic capacity of D2D and cellular users in reuse, dedicated, and cellular communication modes with the time switching and power splitting architectures of SWIPT. We then leverage the derived results, along with the energy efficiency to design an energy-efficient mode selection mechanism. Our simulation results show that the developed mechanism is able to select the best mode for D2D communication with better energy efficiency, especially in an ultra-dense cellular network as compared with a state-of-the-art mode selection approach.

I. Introduction

While interference management [1]–[4], plays a critical role in implementing Device-to-Device (D2D) communications in cellular networks, mode selection [5]–[8], has been realized as the most useful means. The aim is to select one of the following three communication modes; reuse, dedicated, and cellular. In the reuse mode, D2D communications are carried out by letting D2D users reuse the cellular uplink resources at the expense of possible interference between D2D links and the reused cellular links. On the other hand, the dedicated mode requires certain spectrum resources, which are solely reserved for D2D users by the base station. In this case there would be no interference between D2D links and cellular links. In cellular mode, D2D users act just like cellular users and the base station serves as a relay to transfer data between D2D transmitters and receivers. Also, in this mode there would be no interference between D2D and cellular communications. In general, the interference experienced by D2D and cellular users is not the same as in different modes, which leads to a varying system performance.