With 5GC, 4G, 3G and Non-5G-RAN (radio access networks other than 5G) such as public Wi-Fi will be able to connect to 5GC via a common interface.
Using the N3IWF (non-3GPP Inter-Working Function), which is a function newly introduced from 5G, RANs other than 5G-RAN can also be connected to 5GC. It is called Multi-RAT (Radio Access Technology), which connects to 5GC from multiple wireless accesses.
The N3IWF acts as a gateway for the 5GCN with support for N2 and N3 interface towards the 5GCN. Additionally, N3IWF provides a secure connection for the UE accessing the 5GCN over non-3GPP access network with support for IPsec between the UE and the N3IWF.
N3IWF mainly provides a secure gateway to operator’s 5G network for non-3GPP access.