Note that, the architecture shown in FIG. 1 is merely one of the 5G architecture options or deployment scenarios (see Annex J of Non-Patent Literature 1 and see Non-Patent Literature 2). The architecture shown in FIG. 1 is referred to as “Standalone NR (in NextGen System)” or “Option 2”. In contrast, FIGS. 2 and 3 show architecture Options 3 and 3A, which are referred to as “Non-standalone NR in EPS”. In FIGS. 2 and 3, control interfaces are shown as dashed lines, while user plane interfaces are shown as solid lines. Architecture Options 3 and 3A are Dual connectivity (DC) deployments including E-UTRA as the anchor RAT (or the primary RAT or the master RAT) and NR as a secondary RAT. In Options 3 and 3A, E-UTRA (LTE eNB) and NR (gNB) are connected to the EPC. The NR user plane connection to the EPC goes through the LTE eNB in Option 3, whereas in Option 3A, it passes directly through a user plane interface between the gNB and the EPC.

Non-Patent Literature 3 has suggested that in Architecture Options 3 and 3A, which are DC architecture where E-UTRA and NR are connected to the EPC, the NR gNB supports the LTE DC functionalities and procedures. Non-Patent Literature 3 has also suggested that in the DC architecture where E-UTRA and NR are connected to the EPC, the NR gNB applies the LTE QoS framework (i.e., bearer based QoS) to the EPC, the LTE eNB and the UE. Further, Non-Patent Literature 3 has suggested the following proposals:

• LTE DC procedures (e.g., SeNB addition) are applied when adding NR gNB as secondary node, in which necessary QoS service (i.e., bearer) are configured;