Note that a plurality of 5G-DUs may be connected to the 5G-CU. In addition, NR-DC (NR-NR Dual Connectivity) may be performed by connecting the UE to a plurality of 5G-CUs, and NR-DC may be performed by connecting the UE to a plurality of 5G-DUs and a single 5G-CU.

FIG. 2 is a drawing illustrating a configuration example of a wireless communication system according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a wireless communication system at the time of MR-DC (Multi-RAT Dual Connectivity).

As illustrated in FIG. 2, a user apparatus 20 communicates with a base station apparatus 10A provided by an NR system and a base station apparatus 10B provided by the NR system (hereafter referred to as “base station apparatus 10” if the base station apparatus 10A and the base station apparatus 10B are not distinguished). In addition, the user apparatus 20 supports NR-NR dual connectivity, i.e., NR-DC, in which the base station apparatus 10A is a master node (hereinafter referred to as “MN”) and the base station apparatus 10B is a secondary node (hereinafter referred to as “SN”). The user apparatus 20 can perform simultaneous transmission to or simultaneous reception from, the base station apparatus 10A as a master node and the base station apparatus 10B as a secondary node, by using a plurality of component carriers provided by the base station apparatus 10A as a master node and the base station apparatus 10B as a secondary node.