Section: 5.4.12 Paging Early Indication with Paging Subgrouping Assistance 5.4.12.1 General
Content: The RAN and UE may use a Paging Early Indication with Paging Subgrouping (PEIPS) to reduce the UE's power consumption in RRC_IDLE and RRC_INACTIVE over NR (see TS 38.304[ NR; User Equipment (UE) procedures in Idle mode and in RRC Inactive state ]  [50]). The paging subgrouping can be based on either the UE's temporary ID or a Paging Subgroup ID allocated by the AMF. Paging subgrouping based on the UE's temporary ID is implemented within the NG-RAN. For paging subgrouping based on UE's temporary ID, the UE's support is included in the UE Radio Capability for Paging, either derived by the NG-RAN from UE provided UE radio capability (see clause 5.4.4) or based on UE Radio Capability ID if UE radio capability signalling optimisation is used (see clause 5.4.4.1a). The AMF, when determining its paging strategy (see clause 5.4.3), should take into consideration whether a gNB is using Paging subgrouping based on the UE's temporary ID. NOTE: Paging messages sent to that gNB can increase UE power consumption for other UEs that support Paging Subgrouping based on the UE's temporary ID. If paging subgroups are being allocated by the AMF, then all AMFs connected to one gNB (including the AMFs in different PLMNs using 5G MOCN network sharing) shall use a consistent policy in allocating UEs to the paging subgroups. The AMF may configure up to 8 different Paging Subgroup IDs. NOTE: Because the UE uses the AMF allocated paging subgroup across all cells in its TAI-list, and, different, overlapping TAI lists can be allocated to different UEs, then to avoid UE power consumption increasing, it is likely to be necessary that all AMFs with an overlapping coverage area use a consistent policy in allocating UEs to the paging subgroups. The NG-RAN node and the UE determine per cell which paging subgrouping method to use as defined in TS 38.304[ NR; User Equipment (UE) procedures in Idle mode and in RRC Inactive state ]  [50] and TS 38.331[ NR; Radio Resource Control (RRC); Protocol specification ]  [28].