Relay selection of relay-assisted Device-to-Device and uplink communication underlying cellular networks

Recently, an enormous increasing number of mobile devices have changed people's life and brought huge demands for services. D2D (Device-to-Device) communication is a brand-new fashion that allows mobile stations communicating directly with each other using existing licensed band without traversing through core network, and thereby offload traffic from base stations (BS). On the other hand, relays are indispensable to the next generations of mobile communication networks. Relays can remove the coverage holes, increase system capacity, expand the coverage area of base stations and enhance transmission rate for the devices in cell edge, and thereby it also provides uniform data rate coverage in the cellular networks. This paper proposes a model that integrates the advantages of relay and D2D and proposes a method that can improve spectrum efficiency and decrease path loss or shadow fading which makes worse communication in the system. This paper also proposes a way how to choose a better relay and it can increase the system throughput. Simulation results of uplink and D2D communication show that the proposed method can increase the system throughput.