Power Control for Full-Duplex D2D Communications Underlaying Cellular Networks

As two promising candidate techniques for the 5G mobile communication system, device-to-device (D2D) communications and full-duplex communications have drawn significant research interests. Since full-duplex communications are suitable for use in low transmit power scenarios to lower the residual self-interference (SI), while D2D communications work in short distance scenarios which result in low transmit power, it is natural to integrate full-duplex into D2D communications. In this paper, we investigate the power control for full-duplex D2D communications underlaying cellular networks. Specifically, we formulate the power control problem by maximizing the achievable sum-rate of the full-duplex D2D link while fulfilling the minimum rate requirement of the cellular link under the maximum transmit power constraint of the cellular user and D2D users. Two algorithms are proposed to solve the optimization problem. For the first algorithm, we convert the objective function into a concave function based on difference of convex (D. C.) structure and propose an iterative algorithm to solve the optimization problem. For the second algorithm, we consider the received signal-to-interference-plus-noise ratios (SINRs) at the D2D users are high. Based on high-SINR approximation, closed-form optimal solutions are obtained for different boundaries of the feasible region. Numerical results are presented to illustrate the effect of the channel gains and SI cancellation ability on the optimal transmit power and the achievable sum-rate of the full-duplex D2D link.