Two types of NGAP applications in 5G (NR) systems

As the information exchange interface between the 5G core network (5GC) and the radio access network (RAN), the NG, interacts with various information through the NGAP protocol, in which signaling is divided into two main categories;

I. Interactive signaling (response required) Main messages include;

• Initial Context Setting:Establishes an initial connection between the terminal (UE) and the network to allow service access.
• PDUSession Resource Setup/Modification/Release:Manages data connections for specific services (e.g. Internet, video calls).
• Switchover preparation/resource allocation/cancellation:Ensures seamless switchover between different gNBs during mobility.
• NG Reset:Resets the UE context on the network side, typically used for network maintenance or troubleshooting.
• NG Setup:Establishes the initial connection between the gNB and the core network.
• Path Switching Request:Switches the UE data path between different gNBs to optimize performance.
• UE Context Modification:Updates UE information on the network side, such as location or service access rights.
• UE Context Release:Releases the UE context indicating that the UE is no longer connected.

The specific transfer interaction information is shown in Table 8.1-1 of the (lower) table;

II. Signaling (no response required) mainly consists of;

• AMF Configuration Updates:Notifies the gNB about AMF configuration changes that affect service delivery.
• Broadcast Session Setup/Modification/Release:Manage broadcast sessions for group communication services.
• Message Distribution Setup/Release:Establish/terminate distribution of messages to multiple UEs simultaneously.
• RAN Configuration Update:Updates the gNB configuration with new parameters or settings.
• uEContextSuspend/Resume:Temporarily suspend or resume the UE context without terminating the connection.
• uERadioCapabilityIDMapping:Associates a UE's radio capability with its identifier.

The specific information to be passed (no answer required) in the NGAP is shown in table 8.1-2 of table (below);