5G: How registration management is different from connection management ?

Question

Is there any major difference between these two procedures when I compare both of these against LTE registration and mobility management ?

Answer 1

Like LTE network, 5G core network supports registration and connection management. Registration in 5G network is as similar as LTE registration while connection management of 5G network is same as LTE mobility management. I want to capture differences between these two in the following format:

5G States LTE States

RM- DEREGISTERED <--------------> EMM-DEREGISTERED
RM-REGISTERED <--------------> EMM-REGISTERED
CM-IDLE <--------------> ECM- IDLE
CM-CONNECTED <--------------> ECM-CONNECTED

One difference which I found in LTE network, RRC states were directly mapped to ECM states. I meant to say when RRC state move to IDLE state, ECM state at MME also moves to ECM-IDLE. But in the 5G network, it is not exactly same as LTE. There is one more RRC state named as RRC-Inactive has been introduced. When an user moves to RRC-inactive state (no radio connection between user and RAN), RAN still maintain ue context and also corresponding state i.e. CM-CONNECTED does not change at AMF. This is the major difference I found between LTE and 5G networks in the context of state management.