Energy-Efficient Joint Scheduling for Relay-Involved D2D Communications

Enabling relay-assisted device-to-device (RA D2D) transmissions is a promising way to fully explore the benefits of developing D2D communications in cellular systems. However, taking relay-assisted D2D mode into account make the scheduling at the base station (BS) even more challenging. This paper focuses on the scheduling issues for the cellular system involving relay-assisted D2D communications. Aiming to maximize the cell-wise energy efficiency (EE), we formulate the issue of joint scheduling on D2D mode selection, channel allocation, and power coordination into a mathematical optimization problem. The formulated problem is then decomposed into two subproblems which can be solved efficiently by referring to our previous work. Particularly, in the context of maximizing the EE, we present a strategy to coordinate the transmit powers for the cellular user equipment (UE) and D2D UE when they are sharing the same channel. Simulation results validate the effectiveness of our proposals on Improving the overall EE.