Content for TS 38.401 Word version: 18.0.0
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8.4 Multi-Connectivity operation
8.4.1 Secondary Node Addition
8.4.1.1 EN-DC
8.4.2 Secondary Node Release (MN/SN initiated)
8.4.2.1 EN-DC
8.4.3 SCG suspend/resume in RRC_INACTIVE
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8.4 Multi-Connectivity operation p. 55
8.4.1 Secondary Node Addition p. 55
8.4.1.1 EN-DC p. 55
This clause gives the SgNB addition procedure in EN-DC given that en-gNB consists of gNB-CU and gNB-DU(s), as shown in Figure 8.4.1.1-1.
Step 1~8.
refer to TS 37.340.
Step a1.
After receiving the SGNB ADDITION REQUEST message from MeNB, the gNB-CU sends the UE CONTEXT SETUP REQUEST message to the gNB-DU to create a UE context. As specified in TS 37.340, in the course of a Secondary Node Change, the UE CONTEXT SETUP REQUEST message may contain source cell group configuration to allow gNB-DU to perform delta configuration.
Step a2.
The gNB-DU responds to the gNB-CU with the UE CONTEXT SETUP RESPONSE message. In case the gNB-DU receives the UE CONTEXT SETUP REQUEST message without the source cell group configuration or in the course of a Secondary Node Change as specified in TS 37.340 or if the gNB-DU decides to perform full configuration after receiving the source cell group configuration, it shall perform full configuration and indicate that it has applied full configuration in the UE CONTEXT SETUP RESPONSE message.
8.4.2 Secondary Node Release (MN/SN initiated) p. 56
8.4.2.1 EN-DC p. 56
This clause gives the SgNB release procedure in EN-DC given that the en-gNB consists of a gNB-CU and gNB-DU(s).
MN initiated SN Release
Step 1~8.
refer to TS 37.340.
Step a1.
After receiving SGNB RELEASE REQUEST message from MeNB, gNB-CU sends the UE CONTEXT MODIFICATION REQUEST message to gNB-DU to stop the data transmission for the UE. It is up to gNB-DU implementation when to stop the UE scheduling.
Step a2.
gNB-DU responds to gNB-CU with UE CONTEXT MODIFICATION RESPONSE message.
Step a3.
After receiving the UE CONTEXT RELEASE message from MeNB, the gNB-CU sends the UE CONTEXT RELEASE COMMAND message to the gNB-DU to release the UE context.
Step a4.
The gNB-DU responds to the gNB-CU with the UE CONTEXT RELEASE COMPLETE message.
SN initiated SN Release
Step 1~8.
refer to TS 37.340.
Step a1.
gNB-CU sends the UE CONTEXT MODIFICATION REQUEST message to gNB-DU to stop the data transmission for the UE. It is up to gNB-DU implementation when to stop the UE scheduling. This step may occur before step 1.
Step a2.
gNB-DU responds to gNB-CU with UE CONTEXT MODIFICATION RESPONSE message.
Step a3.
After receiving the UE CONTEXT RELEASE message from MeNB, the gNB-CU sends the UE CONTEXT RELEASE COMMAND message to the gNB-DU to release the UE context.
Step a4.
The gNB-DU responds to the gNB-CU with the UE CONTEXT RELEASE COMPLETE message.
8.4.3 SCG suspend/resume in RRC_INACTIVE |R16| p. 57
In the following, the procedure for SCG resume in RRC_INACTIVE is described.
Step 1.
The CU of SN sends the UE CONTEXT MODIFICATION REQUEST message to the DU of SN to suspend the SCG of the UE before the UE enters into RRC_INACTIVE state from RRC_CONNECTED state.
Step 2.
The DU of SN sends the UE CONTEXT MODIFICATION RESPONSE to the CU of SN, and keeps all lower layer configuration for UEs without transmitting or receiving data from UE.
Step 3~4.
refer to TS 37.340.
Step 5.
The CU of SN sends the UE CONTEXT MODIFICATION REQUEST message to the DU of SN to resume the SCG of the UE before the UE enters into RRC_CONNECTED state from RRC_INACTIVE state.
Step 6.
The DU of SN sends the UE CONTEXT MODIFICATION RESPONSE message to the CU of SN, and uses the previously stored lower layer configuration for the UE.
Step 7~11.
refer to TS 37.340.
