Section: 8.18.4 MT-SDT
Content: The procedure for mobile terminated small data transmission in RRC Inactive is shown in Figure 8.18.4-1. Figure 8.18.4-1: Mobile Terminated Small Data Transmission in RRC Inactive state. 1. During the setup or modification of the bearer context as specified in 8.9.2, the gNB-CU-CP requests the gNB-CU-UP to provide MT-SDT information. 2a-0. The gNB-CU-UP receives DL data for the UE in RRC Inactive on NG-U interface. 2a-1. The gNB-CU-UP sends DL DATA NOTIFICATION message to the gNB-CU-CP. If determining that DL data packets are only mapped to SDT bearers, as requested in step 1, the gNB-CU-UP includes the MT-SDT information in the DL DATA NOTIFICATION message. 2b. The gNB-CU-CP receives DL NAS signalling over NGAP. 3. After 2a or 2b, the gNB-CU-CP sends PAGING message to the gNB-DU. The MT-SDT indication may be included in the PAGING message. 4. The gNB-DU sends the Paging message to the UE. In case the MT-SDT indication is received in step 3, the gNB-DU includes the MT-SDT indicator in the Paging message. 5. If the UE has been successfully reached, it initiates the RRC connection resume procedure as described in 8.6.2 or 8.9.6.2, or initiates the SDT procedure as described from step 1 in 8.18.1 or from step 9 in 8.18.2 or from step 1 in 8.18.3 with the following difference: - In case SDT procedure is initiated, the UE may indicate MT-SDT in the RRCResumeRequest, which may be without UL data.