Transmission capacity analysis of relay-assisted device-to-device communication in cellular networks

Device-to-device (D2D) communication can effectively meet the demands of high data rate by providing a direct link between two mobile users in cellular networks. In this paper, we analyze the transmission capacity of relay-assisted D2D communication coexisting with cellular networks in an underlay way. Based on stochastic geometry, cellular networks, D2D users and relay nodes (RNs) in the networks are all modeled as Poisson point process. We calculate the RN existence probability and the expectation of relay link distance to obtain the successful transmission probabilities for D2D communication. According to two relay mechanisms for enhancing D2D transmission distance and capacity, we further obtain the transmission capacity of D2D communication with the assistance of RNs, which reflects the influence from D2D density and power. Moreover, the transmission gain with variable D2D link distance is also presented. Finally, numerical results verify the D2D transmission capacity can be enhanced by relay transmission and influenced by not only the user density, power and D2D link distance, but also the mechanisms of using RNs for D2D communication in the networks.