The present document specifies the Stage 2 of the Proximity Services (ProSe) features in EPS. ProSe features consist of: ProSe discovery (direct or EPC-level) and ProSe Direct Communication (using E-UTRAN or WLAN direct).

ProSe discovery identifies that ProSe-enabled UEs are in proximity, using E-UTRAN (with or without E-UTRAN) or EPC.

ProSe Direct Communication 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.

For Public Safety specific usage:

• ProSe-enabled Public Safety UEs can establish the communication path directly between two or more ProSeenabled Public Safety UEs, regardless of whether the ProSe-enabled Public Safety UE is served by E-UTRAN.
• ProSe Direct Communication is also facilitated by the use of a ProSe UE-to-Network Relay, which acts as a relay between E-UTRAN and UEs.

Security aspects of ProSe are defined in TS 33.303 [29].