4.3 Radio Protocol architecture

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

4.3.0 General

In this clause, the radio protocol architecture of E-UTRAN is given for the user plane and the control plane.

4.3.1 User plane

The figure below shows the protocol stack for the user-plane, where PDCP, RLC and MAC sublayers (terminated in eNB on the network side) perform the functions listed for the user plane in clause 6, e.g. header compression, ciphering, scheduling, ARQ and HARQ.

Figure 4.3.1-1: User-plane protocol stack

For NB-IoT, the user plane is not used when transfering data over NAS.

4.3.2 Control plane

The figure below shows the protocol stack for the control-plane, where:

– PDCP sublayer (terminated in eNB on the network side) performs the functions listed for the control plane in clause 6, e.g. ciphering and integrity protection;

– RLC and MAC sublayers (terminated in eNB on the network side) perform the same functions as for the user plane;

– RRC (terminated in eNB on the network side) performs the functions listed in clause 7, e.g.:

– Broadcast;

– Paging;

– RRC connection management;

– RB control;

– Mobility functions;

– UE measurement reporting and control, except for NB-IoT.

– NAS control protocol (terminated in MME on the network side) performs among other things:

– EPS bearer management;

– Authentication;

– ECM-IDLE mobility handling;

– Paging origination in ECM-IDLE;

– Security control.

NOTE 1: The NAS control protocol is not covered by the scope of this TS and is only mentioned for information.

Figure 4.3.2-1: Control-plane protocol stack

NOTE 2: For a NB-IoT UE that only supports Control Plane CIoT EPS optimisation, as defined in TS 24.301 [20], PDCP is bypassed. For a NB-IoT UE that supports Control Plane CIoT EPS optimisation and S1-U data transfer or User Plane CIoT EPS optimisation, as defined in TS 24.301 [20], PDCP is also bypassed (i.e. not used) until AS security is activated.