5.1 Control and user plane stacks

23.3033GPPProximity-based services (ProSe)Release 17Stage 2TS

5.1.1 Control Plane

5.1.1.1 General

The control plane stack consists of protocols for control and support of the user plane functions:

– controlling the configuration of the ProSe-enabled UE;

– controlling ProSe Direct Discovery;

– controlling the set-up of the connection between the Remote UE and the ProSe UE-to-Network Relay; and

– controlling the attributes of an established network access connection, such as activation of an IP address.

The following control planes are used in E-UTRAN mode.

5.1.1.2 UE – ProSe Function

Legend:

– ProSe Control Signalling between UE and ProSe Function is carried over the user plane and is specified in TS 24.334 [24].

NOTE: PC3 may be realized with one or more protocols.

Figure 5.1.1.2-1: Control Plane for PC3 Interface

5.1.1.3 HSS – ProSe Function

Legend:

– Diameter: This protocol supports the transfer of subscription and authentication data for authenticating/authorizing user access to ProSe between ProSe Function and HSS (PC4a). Diameter is defined in RFC 3588 [18].

– Stream Control Transmission Protocol (SCTP): This protocol transfers signalling messages. SCTP is defined in RFC 4960 [19].

– PC4a between the ProSe Function and the HSS is specified in TS 29.344 [22].

Figure 5.1.1.3-1: Control Plane for PC4a Interface

5.1.1.4 SLP – ProSe Function

Legend:

– Mobile Location Protocol (MLP) is specified in OMA LIF MLP [20].

Figure 5.1.1.4-1: Control Plane for PC4b Interface

5.1.1.5 UE – UE

5.1.1.5.1 Discovery plane PC5 interface

Legend:

– PC5-D: The MAC/PHY functionality for E-UTRA based PC5 is specified in TS 36.300 [17].

– The "ProSe protocol" is used for handling ProSe Direct Discovery specified in TS 24.334 [24].

Figure 5.1.1.5.1-1: Discovery Plane PC5 Interface

5.1.1.5.2 PC5 Signalling Protocol

Legend:

– The PDCP/RLC/MAC/PHY functionality is specified in TS 36.300 [17].

– PC5 Signalling Protocol" is used for control plane signalling over PC5 (e.g. establishment, maintenance and release of secure layer-2 link over PC5, TMGI monitoring requests, Cell ID announcement requests etc. as described elsewhere in this specification).

– The SDU Type field (3 bits) in the PDCP header is used to discriminate between IP, ARP and PC5 Signalling Protocol. ARP is not supported for one-to-one communication.

– PC5 Signalling Protocol messages are sent on a unicast Destination Layer-2 ID.

Figure 5.1.1.5.2-1: PC5 Signalling Protocol stack

5.1.1.6 ProSe Function – ProSe Function

Legend:

– PC6 is an inter-PLMN interface between the ProSe Functions in different PLMNs (EPC-level ProSe Discovery) and between the ProSe function in the HPLMN and the ProSe function in Local PLMN (ProSe Direct Discovery). PC7 is a roaming interface between the ProSe function in the HPLMN and the ProSe function in VPLMN. PC6 and PC7 are specified in TS 29.345 [23]

– Diameter: This protocol supports the transfer of subscriber location related information between ProSe Functions (PC6/PC7). Diameter is defined in RFC 3588 [18].

– Stream Control Transmission Protocol (SCTP): This protocol transfers signalling messages. SCTP is defined in RFC 4960 [19].

Figure 5.1.1.6-1: Control Plane for PC6 and PC7 interface

5.1.1.7 ProSe Function – ProSe Application Server

Legend:

– PC2-AP is the PC2 Application Protocol and is specified in TS 29.343 [21].

Figure 5.1.1.7-1: Control Plane for PC2 interface

5.1.2 User Plane

5.1.2.1 UE – UE

Legend:

– PC5-U: The PDCP/RLC/MAC/PHY functionality is specified in TS 36.300 [17].

– For PDCP SDU type "Non-IP", a "Non-IP Type" header is included in the SDU by upper layer to indicate the type of non-IP messages carried as specified in TS 24.334 [24].

NOTE: In this Release of the specification, "Non-IP" SDU type is not used by ProSe Direct Communication.

Figure 5.1.2.1-1: User Plane for PC5 interface

5.1.2.2 UE – UE-to-Network Relay

Legend:

– GPRS Tunnelling Protocol for the user plane (GTP‑U): This protocol tunnels user data between eNodeB and the S‑GW as well as between the S‑GW and the P‑GW in the backbone network. GTP shall encapsulate all end user IP packets.

– MME controls the user plane tunnel establishment and establishes User Plane Bearers between eNodeB and S‑GW.

– UDP/IP: These are the backbone network protocols used for routing user data and control signalling.

– LTE-Uu: The radio protocols of E-UTRAN between the UE and the eNodeB are specified in TS 36.300 [17].

– PC5-U: The radio protocols of E-UTRAN between the UE and the UE-to-Network Relay are specified in clause 5.1.2.1.

Figure 5.1.2.2-1: User Plane for UE-to-Network Relay