Editing My 3GPP TS 38.304 Notes (section)

==5.2	Cell selection and reselection ==

=== 5.2.1 Introduction ===
UE shall perform measurements for cell selection and reselection purposes as specified in TS 38.133.

When evaluating Srxlev and Squal of non-serving cells for reselection evaluation purposes, the UE shall use parameters provided by the serving cell and for the final check on cell selection criterion, the UE shall use parameters provided by the target cell for cell reselection.

The NAS can control the RAT(s) in which the cell selection should be performed, for instance by indicating RAT(s) associated with the selected PLMN, and by maintaining a list of forbidden registration area(s) and a list of equivalent PLMNs. The UE shall select a suitable cell based on RRC_IDLE or RRC_INACTIVE state measurements and cell selection criteria.

In order to expedite the cell selection process, stored information for several RATs, if available, may be used by the UE.

When camped on a cell, the UE shall regularly search for a better cell according to the cell reselection criteria. If a better cell is found, that cell is selected. The change of cell may imply a change of RAT. Details on performance requirements for cell reselection can be found in TS 38.133.

The NAS is informed if the cell selection and reselection result in changes in the received system information relevant for NAS.

For normal service, the UE shall camp on a suitable cell, monitor control channel(s) of that cell so that the UE can:
* receive system information from the PLMN or SNPN; and
** receive registration area information from the PLMN or SNPN, e.g., tracking area information; and
** receive other AS and NAS Information; and
* if registered:
** receive paging and notification messages from the PLMN or SNPN; and
** initiate transfer to Connected mode.

For cell selection in multi-beam operations, measurement quantity of a cell is up to UE implementation.

For cell reselection in multi-beam operations, including inter-RAT reselection from E-UTRA to NR, the measurement quantity of this cell is derived amongst the beams corresponding to the same cell based on SS/PBCH block as follows:
* if ''nrofSS-BlocksToAverage'' (''maxRS-IndexCellQual'' in E-UTRA) is not configured in ''SIB2/SIB4'' (''SIB24'' in E-UTRA); or
* if ''absThreshSS-BlocksConsolidation'' (''threshRS-Index'' in E-UTRA) is not configured in ''SIB2/SIB4'' (''SIB24'' in E-UTRA); or
* if the highest beam measurement quantity value is below or equal to ''absThreshSS-BlocksConsolidation'' (''threshRS-Index'' in E-UTRA):
** derive a cell measurement quantity as the highest beam measurement quantity value, where each beam measurement quantity is described in TS 38.215.
* else:
** derive a cell measurement quantity as the linear average of the power values of up to ''nrofSS-BlocksToAverage'' (''maxRS-IndexCellQual'' in E-UTRA) of highest beam measurement quantity values above ''absThreshSS-BlocksConsolidation'' (''threshRS-Index'' in E-UTRA).
:Editor's note: Location assisted cell reselection, with the distance between UE and the reference location of the cell (serving cell and/or neighbour cell) taken into account, is supported for quasi-earth fixed cell. FFS on how UE performs location acquisition. When UE uses location based cell reselection enhancements, it's up to UE implementation to guarantee that a valid location information is available.
:Editor's note: Distance based cell reselection criteria for quasi-earth fixed cell is supported.

===5.2.2 States and state transitions in RRC_IDLE state and RRC_INACTIVE state ===
See spec for figure 5.2.2-1 that shows the states and state transitions and procedures in RRC_IDLE and RRC_INACTIVE. Whenever a new PLMN selection or new SNPN selection is performed, it causes an exit to number 1.





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