Performance of D2D Underlay and Overlay for Elastic Traffic

We explore the performance of different resource allocation schemes for transferring elastic traffic in a cellular network that is either overlaid or underlaid with D2D traffic. To this end, we model a single cell during uplink transmissions and jointly consider the presence of a randomly varying number of D2D and cellular users in the system. We use different processor sharing queueing models to characterize the performance of the overlaying and underlaying schemes and measure the performance as the mean flow level delay. In the overlaying approach, depending on the load a certain fraction of the radio resources is reserved for the D2D traffic and the cellular traffic, and hence there is no interference between the D2D and cellular users. In the underlaying approach, the D2D users are allowed to opportunistically transmit unless being interfered by a cellular user nearby. Our numerical studies reveal that the underlaying D2D traffic scheme provides a good performance compared to other methods, especially if the interference range of a cellular user is small compared with the cell dimensions. Moreover, the so-called dynamic overlay method we propose appears to perform better than the static overlay scheme.