Energy-Efficient Transmission for Uplink NOMA in Wireless-Powered D2D Communications

We study energy-efficient resource allocation of overlaying device-to-device (D2D) communication in wireless cellular network. In this system, two D2D users first harvest wireless energy from a base station (BS) and then the far D2D user transmits information to the near D2D user. Besides, the near D2D user transmits information of both two users to the BS via NOMA scheme. Due to the interference of NOMA scheme, maximizing energy efficiency (bits/Joule) of the D2D system is a non-convex problem. We formula the problem taking into account the quality of-service requirements of the D2D users. Exploiting the fractional programming theory and difference of convex (DC) programming, we obtain a sub-optimal resource allocation policy. Our solution reveals that the optimal energy-efficient D2D communication should occur if the far D2D user transmits information to the near D2D user with the minimal required rate. Simulation results are provided to demonstrate the advantage of energy efficiency of the proposed algorithm comparing with two baseline schemes.