Paging Initiation
Paging is done in response to the network needing to communicate with a UE that is in CM-IDLE state. The first step in the process is to analyze the messages from a peer node and decide whether paging is needed or not. The operator policy can decide that paging isn’t required under certain circumstances.
When AMF receives the N1N2MsgTransfer from SMF for a UE in CM-IDLE mode, it decides whether to trigger paging or not based on the following checks:
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PPF flag set to true, which indicates mobile reachability timer isn't expired.
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Incoming request doesn’t have skipind attribute set in N1N2MsgTransferReqData IE.
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Incoming request doesn't indicate to transfer a N2 PDU Session Resource Release Command.
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Asynchronous type communication isn’t activated at AMF.
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ARP-based paging priority comparisons for the newly received N1N2Msg from SMF with the previous N1N2Msg for which paging is already in progress.
AMF updates the SMF with the appropriate cause. When AMF is satisfied with the preceding checks, it selects paging profile based on the incoming triggers.
AMF doesn't perform any check, when the paging is triggered to Deregister a UE.