Device-to-Device (D2D) communications underlaying Unmanned aerial vehicle (UAV) with its mobility extend the coverage and improve the data rate of the cell-edge user equipments (CEUEs). In this paper, we propose a mode selection scheme for wireless powered D2D communications underlaying UAV to improve the energy efficiency (EE) of a network. Here, the cell-center user equipments (CCUEs) first harvest energy from the radio frequency (RF) signals of the UAV, and then communicate with the CEUEs using UAV as a relay. Also, to support the massive connectivity, the CCUEs communicate directly with the CEUEs using non-orthogonal multiple access (NOMA). We investigated the problem as a mixed-integer non-linear programming (MINLP) form, and then divide it into three sub-problems. In the first subproblem, an optimal value of time allocation for energy harvesting (EH) and information transmission (IT) in relay or D2D mode is estimated using Hessian and Lagrangian method to enhance the gain of the CCUEs and CEUEs, respectively. Second, a Golden section search is used to obtain an optimal mode selection based on their EH from the UAV. Numerical results demonstrated that the proposed scheme achieves better results as compared to the existing conventional NOMA and orthogonal multiple access (OMA) schemes.
Discussion(0)
No comments yet. Be the first to comment.