7.3c MT-EDT

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

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

7.3c.1 General

MT-EDT is intended for a single downlink data transmission during the random access procedure.

MT-EDT is initiated by the MME if the UE and the network support MT-EDT and there is a single DL data transmission for the UE.

MT-EDT for Control Plane CIoT EPS Optimisation and for User Plane CIoT EPS Optimisation, as defined in TS 23.401 [17], is characterised as below:

– Support for MT-EDT for the Control Plane CIoT EPS Optimisation and/or for the User Plane CIoT EPS Optimisation is reported by UE at NAS level;

– DL data size is included in the S1-AP Paging message for the UE;

– MT-EDT indication is included in the Paging message for the UE over the Uu interface;

– For User Plane CIoT EPS Optimisation, the UE has been provided with a NextHopChainingCount in the RRCConnectionRelease message with suspend indication;

– In response to the Paging message including MT-EDT indication, the UE triggers the MO-EDT procedure for Control Plane CIoT EPS Optimisation or for User Plane CIoT EPS Optimisation if the upper layers request the establishment or resumption of the RRC Connection for Mobile Terminated Call;

– There is no transition to RRC CONNECTED.

MT-EDT is only applicable to BL UEs, UEs in enhanced coverage and NB-IoT UEs.

7.3c.2 MT-EDT for Control Plane CIoT EPS Optimisation

The MT-EDT procedure for Control Plane CIoT EPS Optimisation is illustrated in Figure 7.3c-1.

Figure 7.3c-1: MT-EDT for Control Plane CIoT EPS Optimisation

1. Upon arrival of downlink data, the SGW may send the DL data size information to the MME for MT-EDT consideration by the MME.

2. The MME includes the DL data size information in the S1-AP PAGING message to assist eNodeB in triggering MT-EDT.

3. If the data can fit in one single downlink transmission according to the UE category included in the UE Radio Capability for Paging provided in the S1-AP Paging message, the eNB includes mt-EDT indication in the Paging message for the UE.

4. The UE initiates the MO-EDT procedure for the Control Plane CIoT EPS Optimisation as described in clause 7.3b.2 with the following differences:

– In step 1, the UE sends RRCEarlyDataRequest message with the establishment cause mt-Access and without user data.

– In step 7, in case of fallback to the RRC Connection establishment procedure, the downlink data may optionally be included in RRCConnectionSetup message.

7.3c.3 MT-EDT for User Plane CIoT EPS Optimisation

The MT-EDT procedure for User Plane CIoT EPS Optimisation is illustrated in Figure 7.3c-2.

Figure 7.3c-2: MT-EDT for User Plane CIoT EPS Optimisation

1. Upon arrival of downlink data, the SGW may send the DL data size to the MME for MT-EDT consideration by the MME.

2. The MME includes the DL data size in the S1-AP PAGING message to assist eNodeB in triggering MT- EDT.

4. The UE initiates the MO-EDT procedure for the User Plane CIoT EPS Optimisation as described in clause 7.3b.3/ figure 7.3b-2 with the following differences:

– In step 0, the UE selects a random access preamble not configured for EDT;

– In step 1, the UE sends RRCConnectionResumeRequest message with the resume cause mt-EDT and without user data.

– In step 4, the MME may include the Pending Data Indication in the S1AP UE Context Resume Response message to notify the eNB of further data traffic in excess of that initially signalled in step 2. The eNB may use this indication to decide whether to release the UE.