UE-to-Network Relay Model B Discovery in ProSe-Enabled LTE Networks

In this document, we expand previous analytical models to offer a more complete representation of Model B direct discovery protocol used for Proximity Services (ProSe) User Equipment (UE) relay functionality, called UE-to-Network Relay. Using these models, we can obtain performance metrics such as the average time a given Remote UE takes to discover a Relay UE, and we can examine the sensitivity of the discovery performance to various input parameters such as the number of Remote UEs, the number of Relay UEs, and the discovery message transmission rate. We use ns-3 system-level simulations to validate our analytical model and we demonstrate the performance of the UE-to-Network Relay discovery protocol for different values of the discovery message transmission probability, which is a system parameter that the UE can use to throttle its discovery message transmission rate to reduce the probability of collisions.