System Level Evaluation of UE-to-Network Relays in D2D-Enabled LTE Networks

The 3rd Generation Partnership Project (3GPP) introduced UE-to-Network Relays in Long Term Evolution (LTE) Release 13. This technology leverages Proximity Services (ProSe), i.e., the LTE Device-to-device (D2D) communication functionality, to provide user-based relays where a User Equipment (UE) accesses the LTE network by connecting directly to another UE. This functionality aims at improving cell edge capacity and extend network coverage for out-of-coverage UEs. In this paper, we present the extension of our ns-3 ProSe module to support system level simulations of the UE-to-Network Relay functionality, and we analyze the performance of different protocols involved in it. In particular, we focus on UE-to-Network Relay discovery, one-to-one direct link establishment between UEs, and end-to-end communication performance. We finally highlight some of the trade-offs to consider while configuring and deploying UE-to-Network Relay enabled UEs.