5G NSA – option 3 call flows
In this section, we will dig into details of the call flow of 5G UE connected to an option 3x-based NSA network. Let us go over the initial registration call flow step by step:
Figure 10.8 – Option 3x call flow part 1
- Consider DC-capable UE that moves into the coverage area of a 5G NR radio; the UE sends an Attach Request message to the master eNB, and the Packet Data Network (PDN) connectivity request has a UE Network Capability field with a Dual-Connectivity with New Radio (DCNR) flag on.
- Since all signaling is handled by the master eNB, it sends the S1 initial UE message to the Mobility Management Entity (MME), which contains the Attach Request and PDN Connectivity Request with the DCNR bit on.
- After a successful authentication procedure, a Diameter Update Location Answer message is sent to the Home Subscriber Server (HSS) by the MME. This message contains the NR as Secondary RAT field, which indicates...
