gNB-CU-Control Plane (gNB-CU-CP): a logical node hosting the RRC and the control plane part of the PDCP protocol of the gNB-CU for an en-gNB or a gNB. The gNB-CU-CP terminates the E1 interface connected with the gNB-CU-UP and the F1-C interface connected with the gNB-DU.

gNB-CU-User Plane (gNB-CU-UP): a logical node hosting the user plane part of the PDCP protocol of the gNB-CU for an en-gNB, and the user plane part of the PDCP protocol and the SDAP protocol of the gNB-CU for a gNB. The gNB-CU-UP terminates the E1 interface connected with the gNB-CU-CP and the F1-U interface connected with the gNB-DU.

A gNB may consist of a gNB-CU-CP, multiple gNB-CU-UPs and multiple gNB-DUs;

-The gNB-CU-CP is connected to the gNB-DU through the F1-C interface;

-The gNB-CU-UP is connected to the gNB-DU through the F1-U interface;

-The gNB-CU-UP is connected to the gNB-CU-CP through the E1 interface;

-One gNB-DU is connected to only one gNB-CU-CP;

-One gNB-CU-UP is connected to only one gNB-CU-CP;

-One gNB-DU can be connected to multiple gNB-CU-UPs under the control of the same gNB-CU-CP;

-One gNB-CU-UP can be connected to multiple DUs under the control of the same gNB-CU-CP;