Energy Efficient D2D Communications in Dynamic TDD Systems
Abstract: Device-to-device device (D2D) communication is a promising technology for improving the performance of proximity proximity-based based services. This paper demonstrates how the integration of D2D communication in cellular systems operating under dynamic time division duplex (TDD) (TDD can improve energy efficiency. We perform joint optimization of mode selection, uplink/downlink transmission period, and power allocation to minimize the transmission energy consumption while satisfying a traffic requirement. Solutions are developed for two scenarios: with and without interference among D2D communications. Both formulations are expressed as mixed mixed-integer integer nonlinear programming problems, which are NP-hard hard in general. We exploit problem structure to develop efficient solutions for both scena scenarios. For the interference-free free case, we design algorithms that find the optimal solution in polynomial time. When considering interference, we propose a customized solver based on branch-and-bound bound that reduces the search complexity by taking advantage of the problem problem-specific specific proprieties. We complement this solver by a more practical heuristic algorithm. Simulation results demonstrate that D2D communications in dynamic TDD systems can