Research And Implement On Device-to-Device Communication Technologies Underlaying LTE Networks

D2D communication in cellular networks is defined as direct communication between two mobile users without traversing the base station or core network. D2 D communications can enhance the performance of cellular networks, such as improve spectral efficiency, increase overall network throughput, and reduce communication delay.D2D communications can enhance network performance, but it may generate interference to the cellular networks at the same time. The impact of D2 D communications is not only seen on the cellular throughput, but also on the decision-making of the cellular scheduling policy. D2 D communications may undermine the overall fairness of cellular system. The improving proportional fairness(IPF) scheme is proposed to optimize resource allocation and power control between cellular and D2 D connections which share the same resources.IPF scheme first performs admission control to guarantee the quality-of-service requirements for both D2 D users and regular cellular users. Then it allocates powers for each admissible D2 D pair and its potential CU partners. Last, a minimum weight bipartite matching based scheme is developed to select a suitable CU partner for each admissible D2 D pair. It can minimize the overall variation of cellular network schedule metric. IPF scheme can reduce the damage to the fairness of cellular systems, thus it can improve the performance of the cellular system. Simulation results show the IPF scheme can significantly improve the fairness and the throughput of the cellular system, especially the throughput of the cell edge users.