ETSI TS 138 304 V16.6.0 (2021-10)

5G; NR; User Equipment (UE) procedures in idle mode and in RRC Inactive state (3GPP TS 38.304 version 16.6.0 Release 16)

RTS/TSGR-0238304vg60

General Information

• Status: Not Published
• Technical Committee: 3GPP RAN 2 - Radio layer 2 specification and Radio layer 3 RR specification
• Current Stage: 12 - Completion
• Completion Date: 06-Oct-2021

Standards Content (Sample)

ETSI TS 138 304 V16.6.0 (2021-10)






TECHNICAL SPECIFICATION
5G;
NR;
User Equipment (UE)
procedures in idle mode and in RRC Inactive state
(3GPP TS 38.304 version 16.6.0 Release 16)

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3GPP TS 38.304 version 16.6.0 Release 16 1 ETSI TS 138 304 V16.6.0 (2021-10)



Reference
RTS/TSGR-0238304vg60
Keywords
5G
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3GPP TS 38.304 version 16.6.0 Release 16 2 ETSI TS 138 304 V16.6.0 (2021-10)
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ETSI

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3GPP TS 38.304 version 16.6.0 Release 16 3 ETSI TS 138 304 V16.6.0 (2021-10)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 5
1 Scope . 6
2 References . 6
3 Definitions, symbols and abbreviations . 7
3.1 Definitions . 7
3.2 Abbreviations . 8
4 General description of RRC_IDLE state and RRC_INACTIVE state . 9
4.1 Overview . 9
4.2 Functional division between AS and NAS in RRC_IDLE state and RRC_INACTIVE state . 11
4.3 Service types in RRC_IDLE state . 13
4.4 Service types in RRC_INACTIVE state . 14
4.5 Cell Categories . 14
5 Process and procedure descriptions . 15
5.1 PLMN selection and SNPN selection . 15
5.1.1 Support for PLMN selection . 15
5.1.1.1 General . 15
5.1.1.2 NR case . 15
5.1.1.3 E-UTRA case . 16
5.1.2 Support for SNPN selection . 16
5.1.2.1 General . 16
5.1.2.2 NR case . 16
5.2 Cell selection and reselection . 16
5.2.1 Introduction. 16
5.2.2 States and state transitions in RRC_IDLE state and RRC_INACTIVE state . 17
5.2.3 Cell Selection process . 18
5.2.3.1 Description . 18
5.2.3.2 Cell Selection Criterion . 19
5.2.3.3 E-UTRAN case in Cell Selection . 20
5.2.4 Cell Reselection evaluation process . 20
5.2.4.1 Reselection priorities handling . 20
5.2.4.2 Measurement rules for cell re-selection . 22
5.2.4.3 Mobility states of a UE . 22
5.2.4.3.0 Introduction . 22
5.2.4.3.1 Scaling rules . 23
5.2.4.4 Cells with cell reservations, access restrictions or unsuitable for normal camping. 23
5.2.4.5 NR Inter-frequency and inter-RAT Cell Reselection criteria . 24
5.2.4.6 Intra-frequency and equal priority inter-frequency Cell Reselection criteria . 25
5.2.4.7 Cell reselection parameters in system information broadcasts . 25
5.2.4.7.0 General reselection parameters . 25
5.2.4.7.1 Speed dependent reselection parameters . 28
5.2.4.8 Inter-RAT Cell reselection in RRC_INACTIVE state . 28
5.2.4.9 Relaxed measurement . 28
5.2.4.9.0 Relaxed measurement rules . 28
5.2.4.9.1 Relaxed measurement criterion for UE with low mobility . 29
5.2.4.9.2 Relaxed measurement criterion for UE not at cell edge . 30
5.2.4.10 Cell reselection with CAG cells . 30
5.2.5 Camped Normally state . 30
5.2.6 Selection of cell at transition to RRC_IDLE or RRC_INACTIVE state . 30
5.2.7 Any Cell Selection state . 31
5.2.8 Camped on Any Cell state . 31
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3GPP TS 38.304 version 16.6.0 Release 16 4 ETSI TS 138 304 V16.6.0 (2021-10)
5.3 Cell Reservations and Access Restrictions . 31
5.3.0 Introduction. 31
5.3.1 Cell status and cell reservations . 31
5.3.2 Unified access control . 33
5.4 Tracking Area registration . 33
5.5 RAN Area registration . 34
6 Reception of broadcast information . 34
6.1 Reception of system information . 34
7 Paging . 34
7.1 Discontinuous Reception for paging . 34
8 Sidelink Operation . 35
8.1 NR sidelink communication and V2X sidelink communication . 35
8.2 Cell selection and reselection for Sidelink . 36
8.2.1 Parameters used for cell selection and reselection triggered for sidelink . 36
Annex A (informative): Change history . 37
History . 40

ETSI

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3GPP TS 38.304 version 16.6.0 Release 16 5 ETSI TS 138 304 V16.6.0 (2021-10)
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:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
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.
ETSI

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3GPP TS 38.304 version 16.6.0 Release 16 6 ETSI TS 138 304 V16.6.0 (2021-10)
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:
- When the UE is camped on a NR cell;
- When the UE is searching for a cell to camp on;
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 specific reference, subsequent revisions do not apply.
- 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.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 38.300: "NR Overall Description; Stage 2".
[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".
[11] 3GPP TS 38.215: "NR; Physical layer measurements".
[12] 3GPP TS 22.261: "Service requirements for the 5G system".
[13] 3GPP TS 24.890: "5G System – Phase 1; CT WG1 Aspects".
[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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3GPP TS 38.304 version 16.6.0 Release 16 7 ETSI TS 138 304 V16.6.0 (2021-10)
[16] 3GPP TS 23.287: "Architecture enhancements for 5G System (5GS) to support Vehicle-to-
Everything (V2X) services".
[17] 3GPP TS 23.285: "Technical Specification Group Services and System Aspects; Architecture
enhancements for V2X services".
[18] 3GPP TS 22.011: "Service accessibility".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
Acceptable Cell: A cell that satisfies certain conditions as specified in 4.5.
Allowed CAG list: A per-PLMN list of CAG Identifiers the UE is allowed to access (see TS 23.501 [10]).
Available PLMN(s): One or more PLMN(s) for which the UE has found at least one cell and read its PLMN
identity(ies).
Available SNPN(s): One or more SNPN(s) for which the UE has found at least one cell and read its SNPN
identity(ies).
Barred Cell: A cell a UE is not allowed to camp on.
CAG cell: A cell broadcasting at least one Closed Access Group Identifier.
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.
Closed Access Group Identifier: Identifier of a CAG within a PLMN.
Commercial Mobile Alert System: Public Warning System that delivers Warning Notifications provided by Warning
Notification Providers to CMAS capable UEs.
eCall Only Mode: A UE configuration option that allows the UE to register at 5GC and register in IMS to perform only
eCall Over IMS, and a non-emergency IMS call for test and/or terminal reconfiguration services.
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.
Network Identifier: Identifier of an SNPN in combination with a PLMN ID (TS 23.501 [10]).
Non-Public Network: A network deployed for non-public use, as defined in TS 22.261 [12].
NR sidelink communication: AS functionality enabling at least V2X Communication as defined in TS 23.287 [16],
between two or more nearby UEs, using NR technology but not traversing any network node.
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.
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3GPP TS 38.304 version 16.6.0 Release 16 8 ETSI TS 138 304 V16.6.0 (2021-10)
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].
Registered SNPN: This is the SNPN 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.
Selected SNPN: This is the SNPN that has been selected by the NAS, either manually or automatically.
Serving cell: The cell on which the UE is camped.
Sidelink: UE to UE interface for V2X sidelink communication defined in TS 23.287[16].
SNPN Access Mode: Mode of operation wherein UE only selects SNPNs (as defined in TS 23.501 [10]).
SNPN identity: An identifier of an SNPN comprising of a PLMN ID and an NID combination.
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 clause 4.5, for E-UTRA
cell in TS 36.304 [7].
V2X sidelink communication: AS functionality enabling V2X Communication as defined in TS 23.285 [17], between
nearby UEs, using E-UTRA technology but not traversing any network node.
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
CAG Closed Access Group
CAG-ID Closed Access Group Identifier
CMAS Commercial Mobile Alert System
CN Core Network
DCI Downlink Control Information
ETWS Earthquake and Tsunami Warning System
E-UTRA Evolved UMTS Terrestrial Radio Access
E-UTRAN Evolved UMTS Terrestrial Radio Access Network
HRNN Human-Readable Network Name
IAB Integrated Access and Backhaul
IMSI International Mobile Subscriber Identity
MCC Mobile Country Code
MICO Mobile Initiated Connection Only
NAS Non-Access Stratum
NID Network Identifier
NPN Non-Public Network
NR NR Radio Access
PLMN Public Land Mobile Network
RAT Radio Access Technology
RNA RAN-based Notification Area
RNAU RAN-based Notification Area Update
RRC Radio Resource Control
SNPN Stand-alone Non-Public Network
UAC Unified Access Control
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3GPP TS 38.304 version 16.6.0 Release 16 9 ETSI TS 138 304 V16.6.0 (2021-10)
UE User Equipment
UMTS Universal Mobile Telecommunications System
V2X Vehicle to Everything
4 General description of RRC_IDLE state and
RRC_INACTIVE state
4.1 Overview
The RRC_IDLE state and RRC_INACTIVE state tasks can be subdivided into three processes:
- PLMN selection (for UE not operating in SNPN access mode) or SNPN selection (for UE operating in SNPN
access mode);
- Cell selection and reselection;
- Location registration and RNA update.
PLMN selection, SNPN 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 or SNPN, 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) or a SNPN is selected by NAS. For the selected
PLMN/SNPN, 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 or selected SNPN, 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/SNPN then becomes the
registered PLMN/SNPN, 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.
For UE not operating in SNPN access mode, search of available CAGs may be triggered by NAS to support manual
CAG selection. The AS shall report available CAG-ID(s) together with their HRNN (if broadcast) and PLMN(s) to the
NAS.
If the UE loses coverage of the registered PLMN/SNPN, either a new PLMN/SNPN is selected automatically
(automatic mode), or an indication of available PLMNs/SNPNs is given to the user so that a manual selection can be
performed (manual mode). As part of manual SNPN selection, the AS shall report available SNPN identifiers together
with their HRNN (if broadcast) to the NAS.
Registration is not performed by UEs only capable of services that need no registration.
The UE may perform NR sidelink communication and/or V2X sidelink communication while in-coverage or out-of-
coverage for sidelink, as specified in clause 8.
The purpose of camping on a cell in RRC_IDLE state and RRC_INACTIVE state is fourfold:
a) It enables the UE to receive system information from the PLMN or the SNPN.
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.
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3GPP TS 38.304 version 16.6.0 Release 16 10 ETSI TS 138 304 V16.6.0 (2021-10)
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.
d) It enables the UE to receive ETWS and CMAS notifications.
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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3GPP TS 38.304 version 16.6.0 Release 16 11 ETSI TS 138 304 V16.6.0 (2021-10)
4.2 Functional division between AS and NAS in RRC_IDLE
state and RRC_INACTIVE state
Table 4.2-1 presents the functional division between UE non-access stratum (NAS) and UE access stratum (AS)
...