Mode selection for D2D communication underlaying a cellular network with shared relays

This paper analyzes the selection of underlay (reuse mode) or overlay (dedicated mode) for device-to-device (D2D) communication in a multi-cell scenario with shared relays. Two reuse cases that D2D communication reuses the same uplink resources or downlink resources as for cellular communication are considered. The study focuses on the location changes of cellular user, the distance changes of D2D devices, and the power changes of shared relay. Our evaluation shows that the reuse mode is optimal in most cases since the shared relay can manage the inter-cell interference very well, and whether D2D communication reuses the cellular uplink resources or the downlink resources is affected by the system parameters. Specifically the uplink resource reuse mode is preferred when the cellular user is closer to the shared relay. The simulations prove that the introduction of shared relay node enables D2D pairs to have more chances to share the resources with cellular users in underlay mode.