The present document specifies the Stage 2 of the Proximity Services (ProSe) features in EPS, which consist of:
ProSe discovery (direct or EPC-level)
It identifies that ProSe-enabled UEs are in proximity, using E-UTRAN (with or without E-UTRAN) or EPC.
ProSe Direct Communication (using E-UTRAN or WLAN direct)
It enables establishment of communication paths between two or more ProSe-enabled UEs that are in direct communication range. The ProSe Direct Communication path could use E-UTRAN or WLAN.
to see the ToC for advanced Rel-15 Word version