4.1 Functional Split

36.3003GPPEvolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN)Overall descriptionRelease 17Stage 2TS

The eNB hosts the following functions:

– Functions for Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in uplink, downlink and sidelink (scheduling);

– IP and Ethernet header compression, uplink data decompression and encryption of user data stream;

– Selection of an MME at UE attachment when no routing to an MME can be determined from the information provided by the UE;

– Routing of User Plane data towards Serving Gateway;

– Scheduling and transmission of paging messages (originated from the MME);

– Scheduling and transmission of broadcast information (originated from the MME or O&M);

– Measurement and measurement reporting configuration for mobility and scheduling;

– Scheduling and transmission of PWS (which includes ETWS and CMAS) messages (originated from the MME);

– CSG handling;

– Transport level packet marking in the uplink;

– S-GW relocation without UE mobility, as defined in TS 23.401 [17];

– SIPTO@LN handling;

– Maintaining security and radio configuration for User Plane CIoT EPS optimisations, as defined in TS 24.301 [20];

– Optionally registering with the X2 GW (if used).

The DeNB hosts the following functions in addition to the eNB functions:

– S1/X2 proxy functionality for supporting RNs;

– S11 termination and S-GW/P-GW functionality for supporting RNs.

The MME hosts the following functions (see TS 23.401 [17]):

– NAS signalling;

– NAS signalling security;

– AS Security control;

– Selection of CIoT EPS optimisations (e.g., Control Plane CIoT EPS optimisation, as defined in TS 24.301 [20]);

– Inter CN node signalling for mobility between 3GPP access networks;

– Idle mode UE Reachability (including control and execution of paging retransmission);

– Tracking Area list management (for UE in idle and active mode);

– PDN GW and Serving GW selection;

– MME selection for handovers with MME change;

– SGSN selection for handovers to 2G or 3G 3GPP access networks;

– Roaming;

– Authentication;

– Bearer management functions including dedicated bearer establishment. The MME may include two transport layer addresses of different versions in the Transport Layer Address IE to enable that an en-gNB can select either IPv4 or IPv6 for a bearer;

– Support for PWS (which includes ETWS and CMAS) message transmission;

– Optionally performing paging optimisation;

– S-GW relocation without UE mobility, as defined in TS 23.401 [17].

NOTE 1: The MME should not filter the PAGING message based on the CSG IDs towards macro eNBs.

The Serving Gateway (S-GW) hosts the following functions (see TS 23.401 [17]):

– The local Mobility Anchor point for inter-eNB handover;

– Mobility anchoring for inter-3GPP mobility;

– E-UTRAN idle mode downlink packet buffering and initiation of network triggered service request procedure;

– Lawful Interception;

– Packet routeing and forwarding;

– Transport level packet marking in the uplink and the downlink;

– Accounting on user and QCI granularity for inter-operator charging;

– UL and DL charging per UE, PDN, and QCI.

The PDN Gateway (P-GW) hosts the following functions (see TS 23.401 [17]):

– Per-user based packet filtering (by e.g. deep packet inspection);

– Lawful Interception;

– UE IP address allocation;

– Transport level packet marking in the uplink and the downlink;

– UL and DL service level charging, gating and rate enforcement;

– DL rate enforcement based on APN-AMBR;

This is summarized on the figure below where yellow boxes depict the logical nodes, white boxes depict the functional entities of the control plane and blue boxes depict the radio protocol layers.

NOTE 2: There is no logical E-UTRAN node other than the eNB needed for RRM purposes.

NOTE 3: MBMS related functions in E-UTRAN are described separately in clause 15.

Figure 4.1-1: Functional Split between E-UTRAN and EPC