ETSI TS 136 304 V15.4.0 (2019-07)

LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) procedures in idle mode (3GPP TS 36.304 version 15.4.0 Release 15)

RTS/TSGR-0236304vf40

General Information

• Status: Published
• Publication Date: 24-Jul-2019
• Technical Committee: 3GPP RAN 2 - Radio layer 2 specification and Radio layer 3 RR specification
• Current Stage: 12 - Completion
• Completion Date: 25-Jul-2019

Standards Content (Sample)

TECHNICAL SPECIFICATION
LTE;
Evolved Universal Terrestrial Radio Access (E-UTRA);
User Equipment (UE) procedures in idle mode
(3GPP TS 36.304 version 15.4.0 Release 15)

3GPP TS 36.304 version 15.4.0 Release 15 1 ETSI TS 136 304 V15.4.0 (2019-07)

Reference
RTS/TSGR-0236304vf40
Keywords
LTE
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ETSI
3GPP TS 36.304 version 15.4.0 Release 15 2 ETSI TS 136 304 V15.4.0 (2019-07)
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ETSI
3GPP TS 36.304 version 15.4.0 Release 15 3 ETSI TS 136 304 V15.4.0 (2019-07)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 5
1 Scope . 6
2 References . 6
3 Definitions and abbreviations . 8
3.1 Definitions . 8
3.2 Symbols . 9
3.3 Abbreviations . 10
4 General description of Idle mode . 11
4.1 Overview . 11
4.2 Functional division between AS and NAS in Idle mode . 12
4.3 Service types in Idle Mode . 14
4.4 NB-IoT functionality in Idle Mode . 16
5 Process and procedure descriptions . 16
5.1 PLMN selection . 16
5.1.1 Void . 17
5.1.2 Support for PLMN selection . 17
5.1.2.1 General . 17
5.1.2.2 E-UTRA and NB-IoT case . 17
5.1.2.3 UTRA case . 17
5.1.2.4 GSM case . 17
5.1.2.5 CDMA2000 case . 17
5.1.2.6 NR case . 17
5.2 Cell selection and reselection . 18
5.2.1 Introduction. 18
5.2.2 States and state transitions in Idle Mode . 19
5.2.3 Cell Selection process . 20
5.2.3.1 Description . 20
5.2.3.2 Cell Selection Criterion . 21
5.2.3.2a Cell Selection Criterion for NB-IoT . 22
5.2.3.3 CSG cells and Hybrid cells in Cell Selection . 22
5.2.3.4 GSM case in Cell Selection . 23
5.2.3.5 UTRAN case in Cell Selection. 23
5.2.3.6 NR case in Cell Selection . 23
5.2.4 Cell Reselection evaluation process . 23
5.2.4.1 Reselection priorities handling . 23
5.2.4.2 Measurement rules for cell re-selection . 25
5.2.4.2a Measurement rules for cell re-selection for NB-IoT . 25
5.2.4.3 Mobility states of a UE . 25
5.2.4.3.1 Scaling rules . 26
5.2.4.4 Cells with cell reservations, access restrictions or unsuitable for normal camping. 27
5.2.4.5 E-UTRAN Inter-frequency and inter-RAT Cell Reselection criteria . 27
5.2.4.6 Intra-frequency and equal priority inter-frequency Cell Reselection criteria . 28
5.2.4.6a Reselection for enhanced coverage . 30
5.2.4.7 Cell reselection parameters in system information broadcasts . 30
5.2.4.7.1 Speed dependant reselection parameters . 32
5.2.4.8 Cell reselection with CSG cells . 33
5.2.4.8.1 Cell reselection from a non-CSG cell to a CSG cell . 33
5.2.4.8.2 Cell reselection from a CSG cell . 33
5.2.4.9 Cell reselection with Hybrid cells . 33
5.2.4.10 E-UTRAN Inter-frequency Redistribution procedure . 34
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5.2.4.10.1 Redistribution target selection . 34
5.2.4.11 Cell reselection when storing UE AS context . 35
5.2.4.12 Relaxed monitoring . 35
5.2.4.12.0 Relaxed monitoring measurement rules . 35
5.2.4.12.1 Relaxed monitoring criterion . 35
5.2.5 Void . 35
5.2.6 Camped Normally state . 35
5.2.7 Cell Selection at transition to RRC_IDLE or RRC_INACTIVE state . 36
5.2.7a Cell Selection when leaving RRC_CONNECTED state for NB-IoT . 36
5.2.8 Any Cell Selection state . 36
5.2.8a Any Cell Selection state for NB-IoT . 36
5.2.9 Camped on Any Cell state . 36
5.3 Cell Reservations and Access Restrictions . 37
5.3.1 Cell status and cell reservations . 37
5.3.2 Access control . 39
5.3.3 Emergency call . 39
5.4 Tracking Area registration . 39
5.5 Support for manual CSG selection . 40
5.5.1 E-UTRA case . 40
5.5.2 UTRA case. 40
5.6 RAN-assisted WLAN interworking . 40
5.6.1 RAN assistance parameter handling in RRC_IDLE . 40
5.6.2 Access network selection and traffic steering rules . 40
5.6.3 RAN assistance parameters definition . 41
6 Reception of broadcast information . 42
6.1 Reception of system information . 42
6.2 Reception of MBMS . 42
7 Paging . 43
7.1 Discontinuous Reception for paging . 43
7.2 Subframe Patterns. 44
7.3 Paging in extended DRX . 45
7.4 Paging with Wake Up Signal . 46
8 Logged measurements . 46
9 Accessibility measurements . 47
10 Mobility History Information . 47
11 Sidelink operation . 47
11.1 Sidelink communication and V2X sidelink communication . 47
11.2 Sidelink discovery . 47
11.3 Sidelink synchronisation . 48
11.4 Cell selection and reselection for sidelink . 48
11.4.1 Parameters used for cell selection and reselection triggered for sidelink . 48
12. General description of UE camping on E-UTRA connected to 5GC . 48
Annex A (informative): Void . 50
Annex B (informative): Example of Hashed ID Calculation using 32-bit FCS . 51
Annex C (informative): Change history . 52
History . 56

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Foreword
rd
This Technical Specification has been produced by the 3 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.
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3GPP TS 36.304 version 15.4.0 Release 15 6 ETSI TS 136 304 V15.4.0 (2019-07)
1 Scope
The present document specifies the Access Stratum (AS) part of the Idle Mode procedures applicable to a UE. The non-
access stratum (NAS) part of Idle mode procedures and processes is specified in TS 23.122 [5].
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 E-UTRA, including multi-RAT UEs as described in 3GPP
specifications, in the following cases:
- When the UE is camped on an E-UTRA 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 RAT.
The Idle Mode procedures defined in this specification are also applicable for a UE in RRC_INACTIVE state unless
specified otherwise.
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 25.990: "Vocabulary for UTRAN".
[2] 3GPP TS 36.300: "E-UTRA and E-UTRAN Overall Description; Stage 2".
[3] 3GPP TS 36.331: "E-UTRA; Radio Resource Control (RRC) - Protocol Specification".
[4] 3GPP TS 22.011: "Service accessibility".
[5] 3GPP TS 23.122: "NAS functions related to Mobile Station (MS) in idle mode".
[6] 3GPP TS 36.213: "E-UTRA; Physical layer procedures".
[7] 3GPP TS 36.214: "E-UTRA; Physical layer; Measurements".
[8] 3GPP TS 25.304: "User Equipment (UE) procedures in idle mode and procedures for cell
reselection in connected mode"
[9] 3GPP TS 43.022: "Functions related to Mobile Station in idle mode and group receive mode".
[10] 3GPP TS 36.133: "Requirements for Support of Radio Resource Management".
[11] void
[12] void
[13] void
[14] void
[15] void
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[16] 3GPP TS 24.301: "Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage
3"
[17] 3GPP2 C.S0024-C v2.0: "cdma2000 High Rate Packet Data Air Interface Specification".
[18] 3GPP2 C.S0005-F v1.0: "Upper Layer (Layer 3) Signalling Standard for cdma2000 Spread
Spectrum Systems".
[19] 3GPP TS 25.304: "User Equipment (UE) procedures in idle mode and procedures for cell
reselection in connected mode".
[20] 3GPP TS 24.008: "Mobile Radio Interface Layer 3 specification; Core Network Protocols;
Stage 3"
[21] 3GPP TS 37.320: "Universal Terrestrial Radio Access (UTRA) and Evolved Universal Terrestrial
Radio Access (E-UTRA); Radio measurement collection for Minimization of Drive Tests (MDT);
Overall description; Stage 2".
[22] 3GPP TS 26.346: "Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs".
[23] 3GPP TS 23.401: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access".
[24] 3GPP TS 23.682: "Architecture enhancements to facilitate communications with packet data
networks and applications".
[25] 3GPP TS 23.402: "Architecture enhancements for non-3GPP accesses".
[26] IEEE 802.11, Part 11: "Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY)
specifications, IEEE Std.".
[27] Wi-Fi Alliance Technical Committee, Hotspot 2.0 Technical Task Group: "Hotspot 2.0 (Release 2)
Technical Specification".
[28] 3GPP TS 24.302: "Access to the 3GPP Evolved Packet Core (EPC) via non-3GPP access
networks".
[29] 3GPP TS 23.303: "Proximity-based services (ProSe); Stage 2".
[30] 3GPP TS 36.321: "E-UTRA; Medium Access Control (MAC) protocol specification".
[31] 3GPP TS 24.105: "Application specific Congestion control for Data Communication (ACDC)
Management Object (MO)".
[32] 3GPP TS 31.102: "Characteristics of the Universal Subscriber Identity Module (USIM)
application".
[33] 3GPP TS 36.101: "Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE)
radio transmission and reception".
[34] Void
[35] 3GPP TS 23.003: "Numbering, addressing and identification".
[36] 3GPP TS 23.285: "Technical Specification Group Services and System Aspects; Architecture
enhancements for V2X services".
[37] 3GPP TS 38.331: "NR; Radio Resource Control (RRC); Protocol specification".
[38] 3GPP TS 38.304: "New Generation Radio Access Network; User Equipment (UE) procedures in
Idle mode and RRC Inactive state".
[39] 3GPP TS 23.501: "System Architecture for the 5G System; Stage 2".
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3 Definitions 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 4.3. A UE can always attempt emergency calls
on an acceptable cell, but restriction as in 5.3.3 apply.
CSG Whitelist: A list provided by NAS containing all the CSG identities and their associated PLMN IDs of the CSGs
to which the subscriber belongs.
NOTE: This list is known as Allowed CSG List in Rel-8 Access Stratum specifications.
Available PLMN(s): One or more PLMN(s) for which the UE has found at least one cell and read its PLMN
identity(ies).
Barred Cell: A cell a UE is not allowed to camp on.
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 Subscriber Group (CSG): A Closed Subscriber Group identifies subscribers of an operator who are permitted
to access one or more cells of the PLMN but which have restricted access (CSG cells).
CN type: The type of core network connectivity supported by an E-UTRA cell, either EPC or 5GC.
Commercial Mobile Alert System: Public Warning System that delivers Warning Notifications provided by Warning
Notification Providers to CMAS capable UEs.
CSG cell: A cell broadcasting a CSG indication that is set to TRUE and a specific CSG identity.
CSG identity: An identifier broadcast by a CSG or hybrid cell/cells and used by the UE to facilitate access for
authorised members of the associated Closed Subscriber Group.
CSG member cell: a cell broadcasting the identity of the selected PLMN, registered PLMN or equivalent PLMN and
for which the CSG whitelist of the UE includes an entry comprising cell's CSG ID and the respective PLMN identity.
DRX cycle: Individual time interval between monitoring Paging Occasion for a specific UE.
eDRX cycle: Time interval between the first Paging Occasions occurring after successive extended DRX periods.
eCall Only Mode: A UE configuration option that allows the UE to attach at EPS 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 [5].
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.
EU-Alert: Public Warning System that delivers Warning Notifications provided by Warning Notification Providers
using the same AS mechanisms as defined for CMAS.
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.
HNB Name: The Home eNodeB Name is a broadcast string in free text format that provides a human readable name for
the Home eNodeB CSG identity and any broadcasted PLMN identity.
HSDN cell: A cell that has higher priority than other cells for cell reselection for HSDN capable UE in a High-mobility
state.
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Hybrid cell: A cell broadcasting a CSG Indicator that is set to FALSE and a specific CSG identity.
Hyper SFN: Index broadcast in System Information that increments at every SFN wrap around (i.e every 10.24s).
Korean Public Alert System (KPAS): Public Warning System that delivers Warning Notifications provided by
Warning Notification Providers using the same AS mechanisms as defined for CMAS.
Location Registration (LR): UE registers its presence in a registration area, for instance regularly or when entering a
new tracking area.
MBMS-dedicated cell: cell dedicated to MBMS transmission.
MBMS/Unicast-mixed cell: cell supporting both unicast and MBMS transmissions.
FeMBMS/Unicast-mixed cell: cell supporting MBMS transmission and unicast transmission as SCell.
NB-IoT: NB-IoT allows access to network services via E-UTRA with a channel bandwidth limited to 200 kHz.
Paging Time Window: The period configured for a UE in extended DRX, during which the UE monitors Paging
Occasions following DRX cycle.
Power saving mode: Mode allowing the UE to reduce its power consumption, as defined in TS 24.301 [16], TS 23.401
[23], TS 23.682 [24].
Process: A local action in the UE invoked by a RRC procedure or an Idle Mode or RRC_INACTIVE state procedure.
Radio Access Technology: Type of technology used for radio access, for instance E-UTRA, UTRA, GSM,
CDMA2000 1xEV-DO (HRPD) or CDMA2000 1x (1xRTT).
Registered PLMN: This is the PLMN on which certain Location Registration outcomes have occurred TS 23.122 [5].
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.
Reserved Cell: A cell on which camping is not allowed, except for particular UEs, if so indicated in the system
information.
Restricted Cell: A cell on which camping is allowed, but access attempts are disallowed for UEs whose access classes
are indicated as barred.
Selected PLMN: This is the PLMN 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 sidelink communication, V2X sidelink communication and sidelink discovery. The
Sidelink corresponds to the PC5 interface as defined in TS 23.303 [29].
Sidelink communication: AS functionality enabling ProSe Direct Communication as defined in TS 23.303 [29],
between two or more nearby UEs, using E-UTRA technology but not traversing any network node. The terminology
"sidelink communication" without "V2X" prefix only concerns PS unless specifically stated otherwise.
Sidelink discovery: AS functionality enabling ProSe Direct Discovery as defined in TS 23.303 [29], using E-UTRA
technology but not traversing any network node.
Strongest cell: The cell on a particular carrier that is considered strongest according to the layer 1 cell search procedure
TS 36.213 [6], TS 36.214 [7].
Suitable Cell: This is a cell on which an UE may camp. For a E-UTRA cell, the criteria are defined in subclause 4.3,
for a UTRA cell in TS 25.304 [8], for a GSM cell in TS 43.022 [9], and for a NR cell in TS 38.304 [38].
V2X sidelink communication: AS functionality enabling V2X Communication as defined in TS 23.285 [36], between
nearby UEs, using E-UTRA technology but not traversing any network node.
3.2 Symbols
For the purposes of the present document, the following symbols apply:
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3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
1xRTT CDMA2000 1x Radio Transmission Technology
AS Access Stratum
AC Access Class (of the USIM)
ACDC Application specific Congestion control for Data Communication
BCCH Broadcast Control Channel
BL Bandwidth reduced Low complexity
BR-BCCH Bandwidth Reduced Broadcast Control Channel
BSS Basic Service Set
CMAS Commercial Mobile Altert System
CSG Closed Subscriber Group
DRX Discontinuous Reception
DL-SCH Downlink Shared Channel
EHPLMN Equivalent Home PLMN
EPC Evolved Packet Core
EPS Evolved Packet System
ETWS Earthquake and Tsunami Warning System
E-UTRA Evolved UMTS Terrestrial Radio Access
E-UTRAN Evolved UMTS Terrestrial Radio Access Network
FDD Frequency Division Duplex
GERAN GSM/EDGE Radio Access Network
HPLMN Home PLMN
HSDN High Speed Dedicated Network
H-SFN Hyper System Frame Number
HRPD High Rate Packet Data
IMSI International Mobile Subscriber Identity
MBMS Multimedia Broadcast-Multicast Service
MBSFN Multimedia Broadcast multicast service Single Frequency Network
MCC Mobile Country Code
MCCH Multicast Control Channel
MDT Minimization of Drive Tests
MM Mobility Management
MNC Mobile Network Code
MPDCCH MTC Physical Downlink Control Channel
MTCH Multicast Traffic Channel
NAS Non-Access Stratum
NB-IoT NarrowBand Internet of Things
NR NR Radio Access
PLMN Public Land Mobile Network
ProSe Proximity-based Services
PSM Power Saving Mode
PTW Paging Time Window
PWS Public Warning System
RAT Radio Access Technology
RNA RAN-based Notification Area
RNAU RAN-based Notification Area Update
RRC Radio Resource Control
SAP Service Access Point
SIBX SystemInformationBlockTypeX
TDD Time Division Duplex
UAC Unified Access Control
UE User Equipment
UMTS Universal Mobile Telecommunications System
USIM Universal Subscriber Identity Module
UTRA UMTS Terrestrial Radio Access
UTRAN UMTS Terrestrial Radio Access Network
V2X Vehicle-to-Everything
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WUS Wake Up Signal
4 General description of Idle mode
4.1 Overview
The idle mode tasks can be subdivided into four processes:
- PLMN selection;
- Cell selection and reselection;
- Location registration;
- Support for manual CSG selection.
The relationship between these processes is illustrated in Figure 4.1-1.

Manual Mode
Automatic mode
PLMN Selection
Indication
to user
Location PLMNs
Registration available
response Available (PLMN,
CSG ID)s to NAS
Support for manual
CSG selection
PLMN selected
(optional CSG
CSG
ID)
selected
NAS Control
Cell Selection
and Reselection
Radio measurements
Registration
Area
changes
MBMS Frequency
Prioritization
Service requests
Location
Registration
Figure 4.1-1: Overall Idle Mode process
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 TS 23.122 [5]. The NAS shall provide a list of equivalent PLMNs, if available, that the
AS shall use for cell selection and cell reselection.
With the cell selection, the UE searches for a suitable cell of the selected PLMN and chooses that cell to provide
available services, further the UE shall tune to its control channel. This choosing is known as "camping on the cell".
For E-UTRA a cell may be associated with more than one CN type (EPC and/or 5GC) and hence the selected cell can
be suitable for more than one CN type. The CN type(s) for which the selected cell is suitable are reported to NAS which
selects a CN type to be used for camping and for the NAS registration procedure (see below). Note that CN type
selection is only applicabe for UE supporting E-UTRA connected to 5GC.
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The UE shall, if necessary, then register its presence, by means of a NAS registration procedure, in the tracking area of
the chosen cell and as outcome of a successful Location Registration the selected PLMN becomes the registered PLMN
TS 23.122 [5].
If the UE finds a more suitable cell, according to the cell reselection criteria, it reselects onto that cell and camps on it.
Similar to cell selection procedure, if the reselected cell is an E-UTRA cell and the UE supports E-UTRA connected to
5GC, the CN type(s) for which the cell is suitable are reported to NAS which selects one of them. 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, a RNA update procedure is performed.
If necessary, the UE shall search for higher priority PLMNs at regular time intervals as described in TS 22.011 [4] and
search for a suitable cell if another PLMN has been selected by NAS.
Search of available CSGs may be triggered by NAS to support manual CSG selection.
If the UE loses coverage of the registered PLMN, either a new PLMN is selected automatically (automatic mode), or an
indication of which PLMNs are available is given to the user, so that a manual selection can be made (manual mode).
Registration is not performed by UEs only capable of services that need no registration.
The UE may perform sidelink communication or V2X sidelink communication or sidelink discovery while in-coverage
or out-of-coverage for sidelink, as specified in clause 11.
The purpose of camping on a cell in idle mode is fivefold:
a) It enables the UE to receive system information from the PLMN.
b) When registered and if the UE wishes to establish an 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 PLMN receives a call for the registered UE, it knows (in most cases) the set of tracking areas (in
RRC_IDLE state) or RNAs (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 this set of tracking areas. The UE will then receive
the paging message because it is tuned to the control channel of a cell in one of the registered tracking areas and
the UE can respond on that control channel.
d) It enables the UE to receive ETWS and CMAS notifications.
e) It enables the UE to receive MBMS services.
If the UE is unable to find a suitable cell to camp on or if the location registration failed (except for LR rejected with
cause #12, cause #14, cause #15 or cause #25, see TS 23.122 [5] and TS 24.301 [16]), it attempts to camp on a cell
irrespective of the PLMN identity, and enters a "limited service" state.
When NAS indicates that PSM starts, the AS configuration (e.g. priorities provided by dedicated signalling and logged
measurements) is kept, all running timers continue to run but the UE need not perform any idle mode tasks. If a timer
expires while the UE is in PSM it is up to UE implementation whether it performs the corresponding action
immediately or the latest when PSM ends. When NAS indicates that PSM ends, the UE shall perform all idle mode
tasks.
4.2 Functional division between AS and NAS in Idle mode
Table 1 presents the functional division between UE non-access stratum (NAS) and UE access stratum (AS) in idle
mode. The NAS part is specified in TS 23.122 [5] and the AS part in the present document.
ETSI
3GPP TS 36.304 version 15.4.0 Release 15 13 ETSI TS 136 304 V15.4.0 (2019-07)
Idle Mode UE Non-Access Stratum UE Access Stratum
Process
PLMN Selection Maintain a list of PLMNs in priority order according Search for available PLMNs.
to TS 23.122 [5]. Select a PLMN using automatic
or manual mode as specified in TS 23.122 [5] 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 [5].
Evaluate reports of available PLMNs and, for E- Perform measurements to support PLMN
UTRA if the UEs supports E-UTRA connected to selection.
5GC, CN type(s) from AS for PLMN selection.
Synchronise to a broadcast channel to
Maintain a list of equivalent PLMN identities. identify found PLMNs (and CN type(s).

Report available PLMNs with associated
RAT(s) and, for E-UTRA if the UE supports
E-UTRA connected to 5GC, CN type(s) to
NAS on request from NAS or
autonomously.
Cell Control cell selection for example by indicating Perform measurements needed to support
Selection RAT(s) associated with the selected PLMN to be cell selection.
used initially in the search of a cell in the cell
selection. NAS is also maintaining lists of Detect and synchronise to a broadcast
forbidden registration areas and a list of CSG IDs channel. Receive and handle broadcast
and their associated PLMN ID on which the UE is information. Forward NAS system
allowed (CSG whitelist) and provide these lists to
information to NAS.
AS.
Search for a suitable cell. The cells
NAS may indicate whether the use of coverage broadcast one or more 'PLMN identity' in
enhancements is not authorized for the selected the system information. Respond to NAS
PLMN. whether such cell is found or not.

NAS may indicate whether the CE mode B is If associated RATs is (are) set for the
restricted for the UE supporting CE mode B. PLMN, perform the search in this (these)
RAT(s) and other RATs for that PLMN as
For E-UTRA if the UE supports E-UTRA specified in TS 23.122 [5].
connected to 5GC, NAS indicates the CN type to
be used for the selected cell. If such a cell is found, the cell is selected to
camp on.
For E-UTRA if the UE supports E-UTRA
connected to 5GC, AS reports the CN
type(s) for which the selected cell is
suitable to NAS.
Cell Control cell reselection by for example, Perform measurements needed to support
Reselection maintaining lists of forbidden registration areas. cell reselection.

Maintain a list of equivalent PLMN identities and Detect and synchronise to a broadcast
provide the list to AS. channel. Receive and handle broadcast
information. Forward NAS system
Maintain a list of forbidden registration areas and information to NAS.
provide the list to AS.
Change cell if a more suitable cell is found.
Maintain a list of CSG IDs and their associated
PLMN ID on which the UE is allowed (CSG For E-UTRA if the UE supports E-UTRA
whitelist) to camp and provide the list to AS. connected to 5GC, the UE reports the CN
type(s) for which the selected cell is
For E-UTRA if the UE supports E-UTRA suitable to NAS.
connected to 5GC, NAS indicates the CN type to
be used for the selected cell.

ETSI
3GPP TS 36.304 version 15.4.0 Release 15 14 ETSI TS 136 304 V15.4.0 (2019-07)
Idle Mode UE Non-Access Stratum UE Access Stratum
Process
Location Register the UE as active after power on. Report registration area information to
registration NAS.
Register the UE's presence in a registration area,
for instance regularly or when entering a new
tracking area.
Maintain lists of forbidden registration areas.

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