Adaptive resource allocation and grouping for device-to-device communications underlaying cellular networks

In this paper, a new adaptive resource allocation and grouping scheme is proposed to enhance the capacity of device-to-device (D2D) systems underlaying cellular networks. In order to increase resource utilization, we propose to divide the outer region of the cell into multiple parts and the corresponding D2D pairs located in the symmetrical parts are designed to reuse the same cellular user equipment´s (CUE´s) resources. To further improve spectrum efficiency, three grouping modes for D2D pairs reusing the same resources are devised and these three modes are proposed to be employed adaptively according to the values of the channel gains between CUEs and base station (BS). Furthermore, by considering interference powers from CUEs to D2D UEs (DUEs) and channel gains of D2D pairs together, an equivalent channel gain is proposed to be exploited to select D2D pairs in symmetrical parts to reuse the same resources of CUEs. Simulation results show that the proposed scheme can increase the capacity of D2D systems up to 3.5 times compared with random resource allocation one.