3GPP TS 38.304
3GPP TS 38.304
3GPP TS 38.304
0 (2019-03)
Technical Specification
3rd Generation Partnership Project;
Technical Specification Group Radio Access Network;
NR;
User Equipment (UE) procedures in Idle mode and RRC
Inactive state
(Release 15)
The present document has been developed within the 3rd Generation Partnership Project (3GPP TM) and may be further elaborated for the purposes of 3GPP..
The present document has not been subject to any approval process by the 3GPP Organizational Partners and shall not be implemented.
This Specification is provided for future development work within 3GPP only. The Organizational Partners accept no liability for any use of this
Specification.
Specifications and Reports for implementation of the 3GPP TM system should be obtained via the 3GPP Organizational Partners' Publications Offices.
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3GPP
Postal address
Internet
http://www.3gpp.org
Copyright Notification
© 2019, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, TTC).
All rights reserved.
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Contents
Foreword..........................................................................................................................................................5
1 Scope......................................................................................................................................................6
2 References..............................................................................................................................................6
3 Definitions, symbols and abbreviations..................................................................................................7
3.1 Definitions...........................................................................................................................................................7
3.2 Abbreviations.......................................................................................................................................................7
4 General description of RRC_IDLE state and RRC_INACTIVE state....................................................8
4.1 Overview.............................................................................................................................................................8
4.2 Functional division between AS and NAS in RRC_IDLE state and RRC_INACTIVE state.............................9
4.3 Service types in RRC_IDLE state.....................................................................................................................12
4.4 Service types in RRC_INACTIVE state...........................................................................................................12
4.5 Cell Categories..................................................................................................................................................12
5 Process and procedure descriptions......................................................................................................13
5.1 PLMN selection.................................................................................................................................................13
5.1.1 Support for PLMN selection........................................................................................................................13
5.1.1.1 General...................................................................................................................................................13
5.1.1.2 NR case..................................................................................................................................................13
5.1.1.3 E-UTRA case.........................................................................................................................................13
5.2 Cell selection and reselection............................................................................................................................13
5.2.1 Introduction..................................................................................................................................................13
5.2.2 States and state transitions in RRC_IDLE state and RRC_INACTIVE state..............................................15
5.2.3 Cell Selection process..................................................................................................................................16
5.2.3.1 Description.............................................................................................................................................16
5.2.3.2 Cell Selection Criterion..........................................................................................................................16
5.2.3.3 E-UTRAN case in Cell Selection...........................................................................................................17
5.2.4 Cell Reselection evaluation process.............................................................................................................17
5.2.4.1 Reselection priorities handling...............................................................................................................17
5.2.4.2 Measurement rules for cell re-selection.................................................................................................18
5.2.4.3 Mobility states of a UE...........................................................................................................................18
5.2.4.3.0 Introduction......................................................................................................................................18
5.2.4.3.1 Scaling rules.....................................................................................................................................19
5.2.4.4 Cells with cell reservations, access restrictions or unsuitable for normal camping...............................20
5.2.4.5 NR Inter-frequency and inter-RAT Cell Reselection criteria................................................................20
5.2.4.6 Intra-frequency and equal priority inter-frequency Cell Reselection criteria........................................21
5.2.4.7 Cell reselection parameters in system information broadcasts..............................................................21
5.2.4.7.0 General reselection parameters.........................................................................................................21
5.2.4.7.1 Speed dependent reselection parameters..........................................................................................23
5.2.4.8 Inter-RAT Cell reselection in RRC_INACTIVE state...........................................................................24
5.2.5 Camped Normally state................................................................................................................................24
5.2.6 Selection of cell at transition to RRC_IDLE or RRC_INACTIVE state.....................................................24
5.2.7 Any Cell Selection state...............................................................................................................................24
5.2.8 Camped on Any Cell state...........................................................................................................................24
5.3 Cell Reservations and Access Restrictions........................................................................................................25
5.3.0 Introduction..................................................................................................................................................25
5.3.1 Cell status and cell reservations...................................................................................................................25
5.3.2 Unified access control..................................................................................................................................26
5.4 Tracking Area registration.................................................................................................................................26
5.5 RAN Area registration.......................................................................................................................................26
6 Reception of broadcast information......................................................................................................26
6.1 Reception of system information.......................................................................................................................26
7 Paging...................................................................................................................................................27
7.1 Discontinuous Reception for paging.................................................................................................................27
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Foreword
This Technical Specification has been produced by the 3rd Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
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1 Scope
The present document specifies the Access Stratum (AS) part of the UE procedures in RRC_IDLE state (also called Idle
mode) and RRC_INACTIVE state. The non-access stratum (NAS) part of Idle mode procedures and processes is
specified in TS 23.122 [9].
The present document specifies the model for the functional division between the NAS and AS in a UE.
The present document applies to all UEs that support at least NR Radio Access, including multi-RAT UEs as described
in 3GPP specifications, in the following cases:
NOTE: When the UE is camped on or searching for a cell to camp on belonging to other RATs, the UE behaviour
is described in the specifications of the other RATs.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[3] 3GPP TS 38.331: "NR; Radio Resource Control (RRC) - Protocol Specification".
[4] 3GPP TS 38.213: "NR; Physical layer procedures for control ".
[5] Void
[6] 3GPP TS 36.331: "E-UTRA; Radio Resource Control (RRC) - Protocol Specification".
[7] 3GPP TS 36.304: "E-UTRA; User Equipment (UE) procedures in RRC_IDLE state ".
[8] 3GPP TS 38.133: "NR; Requirements for Support of Radio Resource Management".
[9] 3GPP TS 23.122: "NAS functions related to Mobile Station (MS) in RRC_IDLE state".
[10] 3GPP TS 23.501: "System Architecture for the 5G System; Stage 2".
[14] 3GPP TS 24.501: "Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3".
[15] 3GPP TS 38.101-1: "NR; User Equipment (UE) radio transmission and reception; Part 1: Range 1
Standalone".
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3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
Available PLMN(s): One or more PLMN(s) for which the UE has found at least one cell and read its PLMN
identity(ies).
Camped on a cell: UE has completed the cell selection/reselection process and has chosen a cell. The UE monitors
system information and (in most cases) paging information.
Camped on any cell: UE is in idle mode and has completed the cell selection/reselection process and has chosen a cell
irrespective of PLMN identity.
Commercial Mobile Alert System: Public Warning System that delivers Warning Notifications provided by Warning
Notification Providers to CMAS capable UEs.
EHPLMN: Any of the PLMN entries contained in the Equivalent HPLMN list TS 23.122 [9].
Equivalent PLMN list: List of PLMNs considered as equivalent by the UE for cell selection, cell reselection, and
handover according to the information provided by the NAS.
Home PLMN: A PLMN where the Mobile Country Code (MCC) and Mobile Network Code (MNC) of the PLMN
identity are the same as the MCC and MNC of the IMSI.
Process: A local action in the UE invoked by an RRC procedure or an RRC_IDLE or RRC_INACTIVE state
procedure.
Radio Access Technology: Type of technology used for radio access, for instance NR or E-UTRA.
Registration Area: (NAS) registration area is an area in which the UE may roam without a need to perform location
registration, which is a NAS procedure.
Registered PLMN: This is the PLMN on which certain Location Registration outcomes have occurred, as specified in
TS 23.122 [9].
Reserved Cell: A cell on which camping is not allowed, except for particular UEs, if so indicated in the system
information.
Selected PLMN: This is the PLMN that has been selected by the NAS, either manually or automatically.
Strongest cell: The cell on a particular frequency that is considered strongest according to the layer 1 cell search
procedure (TS 38.213 [4], TS 38.215 [11]).
Suitable Cell: This is a cell on which a UE may camp. For NR cell, the criteria are defined in subclause 4.5, for E-
UTRA cell in TS 36.304 [7].
3.2 Abbreviations
For the purposes of the present document, the abbreviations given in TR 21.905 [1] and the following apply. An
abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in
TR 21.905 [1].
AS Access Stratum
CMAS Commercial Mobile Alert System
CN Core Network
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4.1 Overview
The RRC_IDLE state and RRC_INACTIVE state tasks can be subdivided into three processes:
- PLMN selection;
PLMN selection, cell reselection procedures, and location registration are common for both RRC_IDLE state and
RRC_INACTIVE state. RNA update is only applicable for RRC_INACTIVE state. When UE selects a new PLMN, UE
transitions from RRC_INACTIVE to RRC_IDLE, as specified in TS 24.501 [14].
When a UE is switched on, a public land mobile network (PLMN) is selected by NAS. For the selected PLMN,
associated RAT(s) may be set, as specified in TS 23.122 [9]. The NAS shall provide a list of equivalent PLMNs, if
available, that the AS shall use for cell selection and cell reselection.
With cell selection, the UE searches for a suitable cell of the selected PLMN, chooses that cell to provide available
services, and monitors its control channel. This procedure is defined as "camping on the cell".
The UE shall, if necessary, then register its presence, by means of a NAS registration procedure, in the tracking area of
the chosen cell. As an outcome of a successful Location Registration, the selected PLMN then becomes the registered
PLMN, as specified in TS 23.122 [9].
If the UE finds a more suitable cell, according to the cell reselection criteria, it reselects onto that cell and camps on it.
If the new cell does not belong to at least one tracking area to which the UE is registered, location registration is
performed. In RRC_INACTIVE state, if the new cell does not belong to the configured RNA, an RNA update
procedure is performed.
If necessary, the UE shall search for higher priority PLMNs at regular time intervals as described in TS 23.122 [9] and
search for a suitable cell if another PLMN has been selected by NAS.
If the UE loses coverage of the registered PLMN, either a new PLMN is selected automatically (automatic mode), or an
indication of available PLMNs is given to the user so that a manual selection can be performed (manual mode).
Registration is not performed by UEs only capable of services that need no registration.
The purpose of camping on a cell in RRC_IDLE state and RRC_INACTIVE state is fourfold:
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b) When registered and if the UE wishes to establish an RRC connection or resume a suspended RRC connection, it
can do this by initially accessing the network on the control channel of the cell on which it is camped.
c) If the network needs to send a message or deliver data to the registered UE, it knows (in most cases) the set of
tracking areas (in RRC_IDLE state) or RNA (in RRC_INACTIVE state) in which the UE is camped. It can then
send a "paging" message for the UE on the control channels of all the cells in the corresponding set of areas. The
UE will then receive the paging message and can respond.
When the UE is in RRC_IDLE state, upper layers may deactivate AS layer when MICO mode is activated as specified
in TS 24.501 [14]. When MICO mode is activated, the AS configuration (e.g. priorities provided by dedicated
signalling) is kept and all running timers continue to run but the UE need not perform any idle mode tasks. If a timer
expires while MICO mode is activated it is up to the UE implementation whether it performs the corresponding action
immediately or the latest when MICO mode is deactivated. When MICO mode is deactivated, the UE shall perform all
idle mode tasks.
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Table 4.2-1: Functional division between AS and NAS in RRC_IDLE state and RRC_INACTIVE state
RRC_IDLE and UE Non-Access Stratum UE Access Stratum
RRC_INACTIVE
state Process
PLMN Selection Maintain a list of PLMNs in priority order according Search for available PLMNs.
to TS 23.122 [9]. Select a PLMN using automatic
or manual mode as specified in TS 23.122 [9] and If associated RAT(s) is (are) set for the
request AS to select a cell belonging to this PLMN, search in this (these) RAT(s) and
PLMN. For each PLMN, associated RAT(s) may other RAT(s) for that PLMN as specified in
be set. TS 23.122 [9].
Evaluate reports of available PLMNs from AS for Perform measurements to support PLMN
PLMN selection. selection.
Maintain a list of "Forbidden Tracking Areas" and Detect and synchronise to a broadcast
provide the list to AS. channel. Receive and handle broadcast
information. Forward NAS system
information to NAS.
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acceptable cell:
An "acceptable cell" is a cell on which the UE may camp to obtain limited service (originate emergency calls and
receive ETWS and CMAS notifications). Such a cell shall fulfil the following requirements, which is the minimum set
of requirements to initiate an emergency call and to receive ETWS and CMAS notification in an NR network:
suitable cell:
- The cell is part of either the selected PLMN or the registered PLMN or PLMN of the Equivalent PLMN list and
trackingAreaCode is provided for that PLMN;
- The cell is part of at least one TA that is not part of the list of "Forbidden Tracking Areas" (TS 22.261 [12]),
which belongs to a PLMN that fulfils the first bullet above.
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barred cell:
reserved cell:
- if a UE has an ongoing emergency call, all acceptable cells of that PLMN are treated as suitable for the duration
of the emergency call.
- camped on a cell that belongs to a registration area that is forbidden for regional provision of service; a cell that
belongs to a registration area that is forbidden for regional provision service (TS 23.122 [9], TS 24.501 [14]) is
suitable but provides only limited service.
During PLMN selection, based on the list of PLMN identities in priority order, the particular PLMN may be selected
either automatically or manually. Each PLMN in the list of PLMN identities is identified by a 'PLMN identity'. In the
system information on the broadcast channel, the UE can receive one or multiple 'PLMN identity' in a given cell. The
result of the PLMN selection performed by NAS (see TS 23.122 [9]) is an identifier of the selected PLMN.
5.1.1.1 General
On request of the NAS, the AS shall perform a search for available PLMNs and report them to NAS.
5.1.1.2 NR case
The UE shall scan all RF channels in the NR bands according to its capabilities to find available PLMNs. On each
carrier, the UE shall search for the strongest cell and read its system information, in order to find out which PLMN(s)
the cell belongs to. If the UE can read one or several PLMN identities in the strongest cell, each found PLMN (see the
PLMN reading in TS 38.331 [3]) shall be reported to the NAS as a high quality PLMN (but without the RSRP value),
provided that the following high-quality criterion is fulfilled:
1. For an NR cell, the measured RSRP value shall be greater than or equal to -110 dBm.
Found PLMNs that do not satisfy the high-quality criterion but for which the UE has been able to read the PLMN
identities are reported to the NAS together with their corresponding RSRP values. The quality measure reported by the
UE to NAS shall be the same for each PLMN found in one cell.
The search for PLMNs may be stopped on request from the NAS. The UE may optimise PLMN search by using stored
information e.g. frequencies and optionally also information on cell parameters from previously received measurement
control information elements.
Once the UE has selected a PLMN, the cell selection procedure shall be performed in order to select a suitable cell of
that PLMN to camp on.
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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 [8].
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 registration area information from the PLMN, e.g., tracking area information; and
- if registered:
For cell reselection in multi-beam operations, the measurement quantity of this cell is derived amongst the beams
corresponding to the same cell based on SS/PBCH block as follows:
- derive a cell measurement quantity as the highest beam measurement quantity value, where each beam
measurement quantity is described in TS 38.215 [11].
- else:
- derive a cell measurement quantity as the linear average of the power values of up to nrofSS-
BlocksToAverage of highest beam measurement quantity values above absThreshSS-BlocksConsolidation.
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go here whenever a
new PLMN is
selected
Stored Initial
information no suitable cell found Cell Selection
Cell Selection
no suitable
cell found suitable cell found 2 suitable cell found
no suitable
cell found
Cell selection NAS indicates that
upon leaving suitable registration on selected
Camped
connected cell found PLMN is rejected
normally
mode (except with cause
#12, #14 , #15 or #25
[9][14])
return to leave trigger
idle/inactive idle/inactive suitable
mode mode cell found
Connected Cell
mode no suitable
Reselection
cell found
Evaluation
Process
go here
when no
USIM in
the UE
Any Cell
no acceptable cell found Selection
USIM inserted
acceptable cell
found; move to
idle mode 1
suitable cell
found
Cell Selection
when leaving acceptable cell Camped on suitable
connected found any cell cell found 2
mode
Connected
mode Cell
(Emergency Reselection no acceptable
calls only) Evaluation cell found
Process
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5.2.3.1 Description
Cell selection is performed by one of the following two procedures:
a) Initial cell selection (no prior knowledge of which RF channels are NR frequencies):
1. The UE shall scan all RF channels in the NR bands according to its capabilities to find a suitable cell.
2. On each frequency, the UE need only search for the strongest cell.
1. This procedure requires stored information of frequencies and optionally also information on cell parameters
from previously received measurement control information elements or from previously detected cells.
2. Once the UE has found a suitable cell, the UE shall select it.
3. If no suitable cell is found, the initial cell selection procedure in a) shall be started.
NOTE: Priorities between different frequencies or RATs provided to the UE by system information or dedicated
signalling are not used in the cell selection process.
where:
where:
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The signalled values Qrxlevminoffset and Qqualminoffset are only applied when a cell is evaluated for cell selection as a result of a
periodic search for a higher priority PLMN while camped normally in a VPLMN (TS 23.122 [9]). During this periodic
search for higher priority PLMN, the UE may check the S criteria of a cell using parameter values stored from a
different cell of this higher priority PLMN.
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normally state, has only dedicated priorities other than for the current frequency, the UE shall consider the current
frequency to be the lowest priority frequency (i.e. lower than any of the network configured values).
The UE shall only perform cell reselection evaluation for NR frequencies and inter-RAT frequencies that are given in
system information and for which the UE has a priority provided.
In case UE receives RRCRelease with deprioritisationReq, UE shall consider current frequency and stored frequencies
due to the previously received RRCRelease with deprioritisationReq or all the frequencies of NR to be the lowest
priority frequency (i.e. lower than any of the network configured values) while T325 is running irrespective of camped
RAT. The UE shall delete the stored deprioritisation request(s) when a PLMN selection is performed on request by
NAS (TS 23.122 [9]).
NOTE: UE should search for a higher priority layer for cell reselection as soon as possible after the change of
priority. The minimum related performance requirements specified in TS 38.133 [8] are still applicable.
The UE shall not consider any black listed cells as candidate for cell reselection.
The UE shall inherit the priorities provided by dedicated signalling and the remaining validity time (i.e. T320 in NR and
E-UTRA), if configured, at inter-RAT cell (re)selection.
NOTE 3: The network may assign dedicated cell reselection priorities for frequencies not configured by system
information.
- If the serving cell fulfils Srxlev > SIntraSearchP and Squal > SIntraSearchQ, the UE may choose not to perform intra-
frequency measurements.
- The UE shall apply the following rules for NR inter-frequencies and inter-RAT frequencies which are indicated
in system information and for which the UE has priority provided as defined in 5.2.4.1:
- For a NR inter-frequency or inter-RAT frequency with a reselection priority higher than the reselection
priority of the current NR frequency, the UE shall perform measurements of higher priority NR inter-
frequency or inter-RAT frequencies according to TS 38.133 [8].
- For a NR inter-frequency with an equal or lower reselection priority than the reselection priority of the
current NR frequency and for inter-RAT frequency with lower reselection priority than the reselection
priority of the current NR frequency:
- If the serving cell fulfils Srxlev > SnonIntraSearchP and Squal > SnonIntraSearchQ, the UE may choose not to perform
measurements of NR inter-frequencies or inter-RAT frequency cells of equal or lower priority;
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5.2.4.3.0 Introduction
The UE mobility state is determined if the parameters (TCRmax, NCR_H, NCR_M and TCRmaxHyst) are broadcasted in system
information for the serving cell.
- If number of cell reselections during time period TCRmax is less than NCR_M.
- If number of cell reselections during time period TCRmax is greater than or equal to NCR_M but less than or equal to
NCR_H.
- If number of cell reselections during time period TCRmax is greater than NCR_H.
The UE shall not consider consecutive reselections where a cell is reselected again right after one reselection for
mobility state detection criteria.
State transitions:
The UE shall:
- else if criteria for either Medium- or High-mobility state is not detected during time period T CRmaxHyst:
If the UE is in High- or Medium-mobility state, the UE shall apply the speed dependent scaling rules as defined in
subclause 5.2.4.3.1.
- no scaling is applied.
- Add the sf-High of "Speed dependent ScalingFactor for Qhyst" to Qhyst if broadcasted in system information;
- For NR cells, multiply TreselectionNR by the sf-High of "Speed dependent ScalingFactor for TreselectionNR"
if broadcasted in system information;
- For EUTRA cells, multiply TreselectionEUTRA by the sf-High of "Speed dependent ScalingFactor for
TreselectionEUTRA" if broadcasted in system information.
- Add the sf-Medium of "Speed dependent ScalingFactor for Qhyst" to Qhyst if broadcasted in system
information;
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- For NR cells, multiply TreselectionNR by the sf-Medium of "Speed dependent ScalingFactor for
TreselectionNR" if broadcasted in system information;
- For EUTRA cells, multiply TreselectionEUTRA by the sf-Medium of "Speed dependent ScalingFactor for
TreselectionEUTRA" if broadcasted in system information.
In case scaling is applied to any TreselectionRAT parameter, the UE shall round up the result after all scalings to the
nearest second.
5.2.4.4 Cells with cell reservations, access restrictions or unsuitable for normal
camping
For the highest ranked cell (including serving cell) according to cell reselection criteria specified in subclause 5.2.4.6,
for the best cell according to absolute priority reselection criteria specified in subclause 5.2.4.5, the UE shall check if
the access is restricted according to the rules in subclause 5.3.1.
If that cell and other cells have to be excluded from the candidate list, as stated in subclause 5.3.1, the UE shall not
consider these as candidates for cell reselection. This limitation shall be removed when the highest ranked cell changes.
If the highest ranked cell or best cell according to absolute priority reselection rules is an intra-frequency or inter-
frequency cell which is not suitable due to being part of the "list of 5GS forbidden TAs for roaming" or belonging to a
PLMN which is not indicated as being equivalent to the registered PLMN, the UE shall not consider this cell and other
cells on the same frequency, as candidates for reselection for a maximum of 300 seconds. If the UE enters into state any
cell selection, any limitation shall be removed. If the UE is redirected under NR control to a frequency for which the
timer is running, any limitation on that frequency shall be removed.
If the highest ranked cell or best cell according to absolute priority reselection rules is an inter-RAT cell which is not
suitable due to being part of the "list of forbidden TAs for roaming" or belonging to a PLMN which is not indicated as
being equivalent to the registered PLMN, the UE shall not consider this cell and other cells on the same frequency, as
candidates for reselection for a maximum of 300 seconds. If the UE enters into state any cell selection, any limitation
shall be removed. If the UE is redirected under NR control to a frequency for which the timer is running, any limitation
on that frequency shall be removed.
- A cell of a higher priority NR or EUTRAN RAT/frequency fulfils Squal > ThreshX, HighQ during a time interval
TreselectionRAT
Otherwise, cell reselection to a cell on a higher priority NR frequency or inter-RAT frequency than the serving
frequency shall be performed if:
- A cell of a higher priority RAT/ frequency fulfils Srxlev > ThreshX, HighP during a time interval TreselectionRAT;
and
- More than 1 second has elapsed since the UE camped on the current serving cell.
Cell reselection to a cell on an equal priority NR frequency shall be based on ranking for intra-frequency cell reselection
as defined in sub-clause 5.2.4.6.
If threshServingLowQ is broadcast in system information and more than 1 second has elapsed since the UE camped on
the current serving cell, cell reselection to a cell on a lower priority NR frequency or inter-RAT frequency than the
serving frequency shall be performed if:
- The serving cell fulfils Squal < ThreshServing, LowQ and a cell of a lower priority NR or E-UTRAN RAT/ frequency
fulfils Squal > ThreshX, LowQ during a time interval TreselectionRAT.
Otherwise, cell reselection to a cell on a lower priority NR frequency or inter-RAT frequency than the serving
frequency shall be performed if:
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- The serving cell fulfils Srxlev < ThreshServing, LowP and a cell of a lower priority RAT/ frequency fulfils Srxlev >
ThreshX, LowP during a time interval TreselectionRAT; and
- More than 1 second has elapsed since the UE camped on the current serving cell.
Cell reselection to a higher priority RAT/frequency shall take precedence over a lower priority RAT/frequency if
multiple cells of different priorities fulfil the cell reselection criteria.
If more than one cell meets the above criteria, the UE shall reselect a cell as follows:
- If the highest-priority frequency is an NR frequency, the highest ranked cell among the cells on the highest
priority frequency(ies) meeting the criteria according to clause 5.2.4.6;
- If the highest-priority frequency is from another RAT, the highest ranked cell among the cells on the highest
priority frequency(ies) meeting the criteria of that RAT.
where:
The UE shall perform ranking of all cells that fulfil the cell selection criterion S, which is defined in 5.2.3.2.
The cells shall be ranked according to the R criteria specified above by deriving Qmeas,n and Qmeas,s and calculating the R
values using averaged RSRP results.
If rangeToBestCell is not configured, the UE shall perform cell reselection to the highest ranked cell. If this cell is
found to be not-suitable, the UE shall behave according to subclause 5.2.4.4.
If rangeToBestCell is configured, then the UE shall perform cell reselection to the cell with the highest number of
beams above the threshold (i.e. absThreshSS-BlocksConsolidation) among the cells whose R value is within
rangeToBestCell of the R value of the highest ranked cell. If there are multiple such cells, the UE shall perform cell
reselection to the highest ranked cell among them. If this cell is found to be not-suitable, the UE shall behave according
to subclause 5.2.4.4.
In all cases, the UE shall reselect the new cell, only if the following conditions are met:
- the new cell is better than the serving cell according to the cell reselection criteria specified above during a time
interval TreselectionRAT;
- more than 1 second has elapsed since the UE camped on the current serving cell.
absThreshSS-BlocksConsolidation
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Release 15 21 3GPP TS 38.304 V15.3.0 (2019-03)
This specifies minimum threshold of the beam which can be used for selection of the highest ranked cell, if
rangeToBestCell is configured.
cellReselectionPriority
cellReselectionSubPriority
This specifies the fractional priority value added to cellReselectionPriority for NR frequency or E-UTRAN frequency.
Qoffsets,n
Qoffsetfrequency
Qhyst
Qoffsettemp
This specifies the additional offset to be used for cell selection and re-selection. It is temporarily used in case the RRC
Connection Establishment fails on the cell as specified in TS 38.331 [3].
Qqualmin
This specifies the minimum required quality level in the cell in dB.
Qrxlevmin
Qrxlevminoffsetcell
Qqualminoffsetcell
rangeToBestCell
This specifies the R value range which the cells whose R value is within the range can be a candidate for the highest
ranked cell. It is configured in SIB2 and used for intra-frequency and equal priority inter-frequency cell reselection and
among the cells on the highest priority frequency(ies) for inter-frequency cell reselection within NR.
TreselectionRAT
This specifies the cell reselection timer value. For each target NR frequency and for each RAT other than NR, a specific
value for the cell reselection timer is defined, which is applicable when evaluating reselection within NR or towards
other RAT (i.e. TreselectionRAT for NR is TreselectionNR, for E-UTRAN TreselectionEUTRA).
NOTE: TreselectionRAT is not broadcast in system information but used in reselection rules by the UE for each
RAT.
TreselectionNR
This specifies the cell reselection timer value Treselection RAT for NR. The parameter can be set per NR frequency as
specified in TS 38.331 [3].
TreselectionEUTRA
This specifies the cell reselection timer value Treselection RAT for E-UTRAN.
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Release 15 22 3GPP TS 38.304 V15.3.0 (2019-03)
ThreshX, HighP
This specifies the Srxlev threshold (in dB) used by the UE when reselecting towards a higher priority RAT/ frequency
than the current serving frequency. Each frequency of NR and E-UTRAN might have a specific threshold.
ThreshX, HighQ
This specifies the Squal threshold (in dB) used by the UE when reselecting towards a higher priority RAT/ frequency
than the current serving frequency. Each frequency of NR and E-UTRAN might have a specific threshold.
ThreshX, LowP
This specifies the Srxlev threshold (in dB) used by the UE when reselecting towards a lower priority RAT/ frequency
than the current serving frequency. Each frequency of NR and E-UTRAN might have a specific threshold.
ThreshX, LowQ
This specifies the Squal threshold (in dB) used by the UE when reselecting towards a lower priority RAT/ frequency
than the current serving frequency. Each frequency of NR and E-UTRAN might have a specific threshold.
ThreshServing, LowP
This specifies the Srxlev threshold (in dB) used by the UE on the serving cell when reselecting towards a lower priority
RAT/ frequency.
ThreshServing, LowQ
This specifies the Squal threshold (in dB) used by the UE on the serving cell when reselecting towards a lower priority
RAT/ frequency.
SIntraSearchP
This specifies the Srxlev threshold (in dB) for intra-frequency measurements.
SIntraSearchQ
This specifies the Squal threshold (in dB) for intra-frequency measurements.
SnonIntraSearchP
This specifies the Srxlev threshold (in dB) for NR inter-frequency and inter-RAT measurements.
SnonIntraSearchQ
This specifies the Squal threshold (in dB) for NR inter-frequency and inter-RAT measurements.
TCRmax
This specifies the duration for evaluating allowed amount of cell reselection(s).
NCR_M
This specifies the maximum number of cell reselections to enter Medium-mobility state.
NCR_H
This specifies the maximum number of cell reselections to enter High-mobility state.
TCRmaxHyst
This specifies the additional time period before the UE can enter Normal-mobility state.
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Release 15 23 3GPP TS 38.304 V15.3.0 (2019-03)
This specifies scaling factor for Qhyst in sf-High for High-mobility state and sf-Medium for Medium-mobility state.
This specifies scaling factor for TreselectionNR in sf-High for High-mobility state and sf-Medium for Medium-mobility
state.
This specifies scaling factor for TreselectionEUTRA in sf-High for High-mobility state and sf-Medium for Medium-
mobility state.
- monitor the paging channel of the cell as specified in clause 7 according to information broadcast in SIB1;
- monitor Short Messages transmitted with P-RNTI over DCI as specified in clause 6.5 in TS 38.331 [3];
2) When information on the BCCH used for the cell reselection evaluation procedure has been modified.
When returning to RRC_IDLE state after UE moved to RRC_CONNECTED state from camped on any cell state, UE
shall attempt to camp on an acceptable cell according to redirectedCarrierInfo, if included in the RRCRelease message.
If the UE cannot find an acceptable cell, the UE is allowed to camp on any acceptable cell of the indicated RAT. If the
RRCRelease message does not contain redirectedCarrierInfo UE shall attempt to select an acceptable cell on an NR
frequency. If no acceptable cell is found according to the above, the UE shall continue to search for an acceptable cell
of any PLMN in state any cell selection.
The UE, which is not camped on any cell, shall stay in this state.
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Release 15 24 3GPP TS 38.304 V15.3.0 (2019-03)
- monitor Short Messages transmitted with P-RNTI over DCI as specified in clause 6.5 in TS 38.331 [3];
2) When information on the BCCH used for the cell reselection evaluation procedure has been modified.
- regularly attempt to find a suitable cell trying all frequencies of all RATs that are supported by the UE. If a
suitable cell is found, UE shall move to camped normally state.
- if the UE supports voice services and the current cell does not support IMS emergency calls as indicated by the
field ims-EmergencySupport in SIB1 as specified in TS 38.331 [3], the UE shall perform cell
selection/reselection to an acceptable cell that supports emergency calls in any supported RAT regardless of
priorities provided in system information from current cell, if no suitable cell is found.
When cell status is indicated as "not barred" and "not reserved" for operator use and not "true" for other use,
- All UEs shall treat this cell as candidate during the cell selection and cell reselection procedures.
When cell status is indicated as "not barred" and "reserved" for operator use for any PLMN and not "true" for other use,
- UEs assigned to Access Identity 11 or 15 operating in their HPLMN/EHPLMN shall treat this cell as candidate
during the cell selection and reselection procedures if the field cellReservedForOperatorUse for that PLMN set
to "reserved".
- UEs assigned to an Access Identity 1, 2 and 12 to 14 shall behave as if the cell status is "barred" in case the cell
is "reserved for operator use" for the registered PLMN or the selected PLMN.
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Release 15 25 3GPP TS 38.304 V15.3.0 (2019-03)
NOTE 1: Access Identities 11, 15 are only valid for use in the HPLMN/ EHPLMN; Access Identities 12, 13, 14 are
only valid for use in the home country as specified in TS 22.261 [12].
When cell status "barred" is indicated or to be treated as if the cell status is "barred",
- The UE is not permitted to select/reselect this cell, not even for emergency calls.
- If the cell is to be treated as if the cell status is "barred" due to being unable to acquire the MIB:
- the UE may exclude the barred cell as a candidate for cell selection/reselection for up to 300 seconds.
- the UE may select another cell on the same frequency if the selection criteria are fulfilled.
- else:
- If the cell is to be treated as if the cell status is "barred" due to being unable to acquire the SIB1:
- The UE may exclude the barred cell as a candidate for cell selection/reselection for up to 300 seconds.
- If the field intraFreqReselection in MIB message is set to "allowed", the UE may select another cell on the
same frequency if re-selection criteria are fulfilled;
- The UE shall exclude the barred cell as a candidate for cell selection/reselection for 300 seconds.
- If the field intraFreqReselection in MIB message is set to "not allowed" the UE shall not re-select a cell on
the same frequency as the barred cell;
- The UE shall exclude the barred cell and the cells on the same frequency as a candidate for cell
selection/reselection for 300 seconds.
The cell selection of another cell may also include a change of RAT.
The UE shall ignore Access Category and Identity related cell access restrictions for cell reselection. A change of the
indicated access restriction shall not trigger cell reselection by the UE.
The UE shall consider Access Category and Identity related cell access restrictions for NAS initiated access attempts
and RNAU as specified in TS 38.331 [3].
If the UE reads more than one PLMN identity in the current cell, the UE shall report the found PLMN identities that
make the cell suitable in the tracking area information to NAS.
The NAS part of the location registration process is specified in TS 23.122 [9].
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Release 15 26 3GPP TS 38.304 V15.3.0 (2019-03)
The UE shall monitor the Paging Occasions (POs) as described in chapter 7.1 to receive System Information change
notifications in RRC_IDLE and RRC_INACTIVE. The changes in the system information are notified by the network
using a Short Message as specified in TS 38.331 [3]. When the Short Message notifies system information changes,
then the UE shall acquire or re-acquire the concerned system information as specified in TS 38.331 [3].
7 Paging
In multi-beam operations, the UE assumes that the same paging message is repeated in all transmitted beams and thus
the selection of the beam(s) for the reception of the paging message is up to UE implementation. The paging message is
same for both RAN initiated paging and CN initiated paging.
The UE initiates RRC Connection Resume procedure upon receiving RAN initiated paging. If the UE receives a CN
initiated paging in RRC_INACTIVE state, the UE moves to RRC_IDLE and informs NAS.
The PDCCH monitoring occasions for paging are determined according to pagingSearchSpace as specified in TS
38.213 [4] and firstPDCCH-MonitoringOccasionOfPO if configured as specified in TS 38.331 [3]. When
SearchSpaceId = 0 is configured for pagingSearchSpace, the PDCCH monitoring occasions for paging are same as for
RMSI as defined in clause 13 in TS 38.213 [4].
When SearchSpaceId = 0 is configured for pagingSearchSpace, Ns is either 1 or 2. For Ns = 1, there is only one PO
which starts from the first PDCCH monitoring occasion for paging in the PF. For Ns = 2, PO is either in the first half
frame (i_s = 0) or the second half frame (i_s = 1) of the PF.
When SearchSpaceId other than 0 is configured for pagingSearchSpace, the UE monitors the (i_s + 1)th PO. A PO is a
set of 'S' consecutive PDCCH monitoring occasions where 'S' is the number of actual transmitted SSBs determined
according to ssb-PositionsInBurst in SIB1. The Kth PDCCH monitoring occasion for paging in the PO corresponds to
the Kth transmitted SSB. The PDCCH monitoring occasions for paging which do not overlap with UL symbols
(determined according to tdd-UL-DL-ConfigurationCommon) are sequentially numbered from zero starting from the
first PDCCH monitoring occasion for paging in the PF. When firstPDCCH-MonitoringOccasionOfPO is present, the
starting PDCCH monitoring occasion number of (i_s + 1)th PO is the (i_s + 1)th value of the firstPDCCH-
MonitoringOccasionOfPO parameter; otherwise, it is equal to i_s * S.
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Release 15 27 3GPP TS 38.304 V15.3.0 (2019-03)
NOTE 2: The PDCCH monitoring occasions for a PO can span multiple radio frames. When SearchSpaceId other
than 0 is configured for paging-SearchSpace the PDCCH monitoring occasions for a PO can span
multiple periods of the paging search space.
The following parameters are used for the calculation of PF and i_s above:
T: DRX cycle of the UE (T is determined by the shortest of the UE specific DRX value, if configured by RRC or
upper layers, and a default DRX value broadcast in system information. If UE specific DRX is not
configured by RRC or by upper layers, the default value is applied).
Parameters Ns, nAndPagingFrameOffset, and the length of default DRX Cycle are signaled in SIB1. The values of N
and PF_offset are derived from the parameter nAndPagingFrameOffset as defined in TS 38.331 [3]. The parameter
first-PDCCH-MonitoringOccasionOfPO is signalled in SIB1 for paging in initial DL BWP. For paging in a DL BWP
other than the initial DL BWP, the parameter first-PDCCH-MonitoringOccasionOfPO is signaled in the corresponding
BWP configuration.
If the UE has no 5G-S-TMSI, for instance when the UE has not yet registered onto the network, the UE shall use as
default identity UE_ID = 0 in the PF and i_s formulas above.
5G-S-TMSI is a 48 bit long bit string as defined in TS 23.501 [10]. 5G-S-TMSI shall in the formulae above be
interpreted as a binary number where the left most bit represents the most significant bit.
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Release 15 28 3GPP TS 38.304 V15.3.0 (2019-03)
Annex A (informative):
Change history
Change history
Date Meeting TDoc CR Rev Cat Subject/Comment New
version
3/2017 Initial skeleton 0.0.1
5/2017 Updated initial skeleton 0.0.2
6/2017 Updated based on RAN2#98 agreements 0.0.3
8/2017 Updated based on feedback from companies 0.0.4
10/2017 No changes 0.0.5
11/2017 No changes 0.0.6
01/2018 No changes 0.0.7
01/2018 No changes 0.1.0
02/2018 Updated based on RAN-NR-AH1801 agreements 0.1.1
02/2018 No changes 0.1.2
03/2018 Updated based on RAN#101 agreements 0.2.0
03/2018 RAN#79 RP-180451 Typo corrections; submitted to RAN#79 for information 1.0.0
04/2018 RAN2#1 R2-1805086 No changes 1.0.1
01bis
05/2018 RAN2#1 R2-1806884 Updated based on RAN2#101bis agreements 1.1.0
02
06/2018 R2-1809262 Updated based on RAN2#102 agreements 1.2.0
06/2018 RP#80 RP-180694 Submitted to RAN#80 for approval 2.0.0
06/2018 Upgraded to Rel-15 after the plenary approval 15.0.0
09/2018 RP-81 RP-181941 0024 2 F Miscellaneous Corrections based on endorsed CRs in RAN2#103 15.1.0
12/2018 RP-82 R2-1818509 0047 4 F Clarification of Paging Monitoring Occasion 15.2.0
RP-82 R2-1816301 0049 2 F Correction to description of PO for default association 15.2.0
RP-82 R2-1819196 0051 3 F Corrections on 38.304 15.2.0
RP-82 R2-1816678 0055 2 F CR on PDCCH monitoring occasions for paging 15.2.0
RP-82 R2-1817200 0056 2 F Release and Redirect in 2-step procedure 15.2.0
RP-82 R2-1818681 0062 4 F Clarification on final suitability check 15.2.0
RP-82 R2-1817261 0063 2 D Correction to Ambiguous Terminologies with respect to Cell Ranking 15.2.0
RP-82 R2-1818125 0066 2 F Correction on definition of PEMAX1, PEMAX2 15.2.0
RP-82 R2-1817662 0067 2 F Clarification of mobility state detection criteria 15.2.0
RP-82 R2-1818549 0074 2 F CR on UE behaviour upon lack of TAC in SIB1 15.2.0
RP-82 R2-1818508 0075 1 F Miscellaneous Corrections in Paging 15.2.0
RP-82 R2-1819037 0076 1 F Clarification for the UE behaviour in camped normally and camped 15.2.0
on any cell states
RP-82 R2-1818883 0079 2 F Corrections on storing and discarding UE AS context 15.2.0
RP-82 R2-1818998 0084 2 F Correction to UE behavior for barred cell 15.2.0
RP-82 R2-1817141 0087 - F Clarification on cell reselection conditions during TreselectionRAT 15.2.0
RP-82 R2-1818881 0088 2 F Introduction of MICO mode 15.2.0
RP-82 R2-1817145 0089 - F Correction to monitoring paging in Camped on Any Cell state 15.2.0
RP-82 R2-1818878 0090 1 F Minor clarifications for paging 15.2.0
RP-82 R2-1818688 0096 1 F Correction to cell access barring alleviation in cell reselection 15.2.0
RP-82 R2-1818683 0097 1 F CR on 38.304 corrections 15.2.0
RP-82 R2-1817738 0099 - F 38.304 CR on derivation of N for paging 15.2.0
RP-82 R2-1819026 0102 1 F Correction of PLMN selection in RRC_INACTIVE 15.2.0
03/2019 RP-83 RP-190540 0081 4 F CR on UE behavior if emergency call is not supported in the current 15.3.0
cell
RP-83 RP-190540 0103 2 F Correction to number of radio frames spanned by PDCCH 15.3.0
monitoring occasions of a PO
RP-83 RP-190540 0104 1 F Correction to signaling aspects of parameter first-PDCCH- 15.3.0
MonitoringOccasionOfPO
RP-83 RP-190540 0111 - F Clarification for paging and UL symbols 15.3.0
RP-83 RP-190544 0113 3 F Miscellaneous Corrections 15.3.0
RP-83 RP-190544 0117 1 F Correction on exception to cell categories for regional provision of 15.3.0
service
3GPP