Paging in 5G is a mechanism used to notify idle User Equipment (UE) about incoming data, call requests, or network updates.
1. UE Idle Mode 💤: When a UE is not actively involved in data transfer, it goes into idle mode to conserve power. In idle mode, the UE monitors the Paging Occasion (PO) for incoming paging messages.
2. Paging Trigger 🚨: When there’s incoming data or a call request for the idle UE, the network needs to notify the UE. The trigger can be a voice call 📞, SMS 📧, or data session 🌐.
3. Paging Message ✉️: The 5G network, through the Access and Mobility Management Function (AMF) and the gNodeB (gNB), sends a paging message containing key information elements (IEs), such as the Paging Identity (Paging-ID) and the UE’s Temporary Mobile Subscriber Identity (TMSI).
4. Paging Occasion (PO) 🕒: The PO is a specific time interval when the UE listens for paging messages. It is determined by the UE’s Paging Frame Index (PF) and Paging Occasion Index (POI).
5. UE Response 🔄: Upon receiving the paging message, the UE initiates a Service Request Procedure to establish a connection with the network. This may involve RRC Connection Establishment, Authentication, and NAS Security Setup.
Example: Alice’s UE is in idle mode 💤. Bob calls Alice 📞, triggering a paging message ✉️ from the 5G network. Alice’s UE listens for the paging message during the Paging Occasion 🕒. Upon receiving the message, Alice’s UE initiates the Service Request Procedure 🔄, allowing the call to be connected.
In summary, the paging concept in 5G enables the network to notify idle UEs about incoming data or call requests. The process involves triggering a paging message containing essential IEs, listening for the message during the Paging Occasion, and responding with a Service Request Procedure to establish a connection with the network.