ETSI ETS 300 535 ed.2 (1995-10)

European digital cellular telecommunications system (Phase 2); Functions related to Mobile Station (MS) in idle mode (GSM 03.22)

RE/SMG-030322P

Evropski digitalni celični telekomunikacijski sistem (faza 2) – Funkcije v zvezi z mobilno postajo (MS) v stanju mirovanja (GSM 03.22)

General Information

• Status: Published
• Publication Date: 05-Oct-1995
• Technical Committee: SMG 3 - Network Aspects
• Current Stage: 12 - Completion
• Due Date: 13-Oct-1995
• Completion Date: 06-Oct-1995
• Ref Project: SIST ETS 300 535 E2:2003 - European digital cellular telecommunications system (Phase 2); Functions related to Mobile Station (MS) in idle mode (GSM 03.22)

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2003
(YURSVNLGLJLWDOQLFHOLþQLWHOHNRPXQLNDFLMVNLVLVWHPID]D±)XQNFLMHY]YH]L]
PRELOQRSRVWDMR06YVWDQMXPLURYDQMD*60
European digital cellular telecommunications system (Phase 2); Functions related to
Mobile Station (MS) in idle mode (GSM 03.22)
Ta slovenski standard je istoveten z: ETS 300 535 Edition 2
ICS:
33.070.50 Globalni sistem za mobilno Global System for Mobile
telekomunikacijo (GSM) Communication (GSM)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 535
TELECOMMUNICATION September 1995
STANDARD Second Edition
Source: ETSI TC-SMG Reference: RE/SMG-030322P
ICS: 33.060.30
European digital cellular telecommunications system, Global System for Mobile communications
Key words:
(GSM)
European digital cellular telecommunications system (Phase 2);
Functions related to Mobile Station (MS) in idle mode
(GSM 03.22)
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - [e-mail]
X.400: Internet:
Tel.: [phone] - Fax: [phone]
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1995. All rights reserved.
New presentation - see History box

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ETS 300 535: September 1995 (GSM 03.22 version 4.9.0)
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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Contents
Foreword .5
1 General.7
1.1 Scope.7
1.2 Normative references .7
1.3 Definitons and abbreviations.9
2 General description of idle mode .10
3 Requirements and technical solutions .10
3.1 PLMN selection and roaming.10
3.2 Camping on a cell .11
3.2.1 Normal camping .11
3.2.2 "Camp on any cell" .12
3.3 Regional provision of service.12
3.4 Borders between location areas .12
3.5 Barred cells and access control.12
3.5.1 Barred cells .12
3.5.2 Prioritising cells .12
3.5.2.1 For cell selection.12
3.5.2.2 For cell reselection.13
3.5.3 Access control.13
3.5.4 Forbidden LA for regional provision of service.13
3.6 Radio constraints .13
3.7 No suitable cell (limited service state) .14
4 Overall process structure .14
4.1 Process goal .14
4.2 States description .15
4.3 List of states.15
4.3.1 List of states for the PLMN selection process.15
4.3.1.1 List of states for automatic mode (Figure 2a).15
4.3.1.2 List of states for manual mode (Figure 2b).16
4.3.2 List of States for the cell selection process (Figure 3) .16
4.3.3 List of states for location updating (Figure 4) .17
4.4 PLMN selection process .18
4.4.1 Introduction.18
4.4.2 Registration on a PLMN .18
4.4.3 PLMN selection .18
4.4.3.1 At switch-on or recovery from lack of coverage.18
4.4.3.2 User reselection.19
4.4.3.3 In VPLMN of home country.19
4.4.4 Abnormal cases.20
4.4.5 National roaming not allowed in this LA .20
4.5 Cell selection process.20
4.6 Location updating process.22
4.6.1 General.22
4.6.2 Initiation of Location Updating .23
4.6.3 Periodic Location Updating .23
4.6.4 IMSI attach/detach operation .24
4.7 Service indication.24
4.8 BCCH allocation broadcasting and storage.24
4.9 Pageability of the mobile subscriber .25
History.33

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ETS 300 535: September 1995 (GSM 03.22 version 4.9.0)
Foreword
This European Telecommunication Standard (ETS) has been produced by the Special Mobile Group
(SMG) Technical Committee (TC) of the European Telecommunications Standards Institute (ETSI).
This ETS defines the functions related to Mobile Station (MS) in idle mode for the European digital cellular
telecommunications system (Phase 2). This ETS corresponds to GSM Technical Specification (GSM-TS)
GSM 03.22 version 4.9.0.
The specification from which this ETS has been derived was originally based on CEPT documentation,
hence the presentation of this ETS may not be entirely in accordance with the ETSI/PNE rules.
Reference is made within this ETS to GSM-TSs (NOTE).
Reference is also made within this ETS to GSM xx.xx. series. The specifications in the series can be
identified, with their full title, within the normative reference clause of this final draft ETS by the first two
digits of their GSM reference number e.g. GSM 09.xx series, refers to GSM 09.01, GSM 09.02, etc.
NOTE: TC-SMG has produced documents which give the technical specifications for the
implementation of the European digital cellular telecommunications system.
Historically, these documents have been identified as GSM Technical Specifications
(GSM-TSs). These TSs may have subsequently become I-ETSs (Phase 1), or ETSs
(Phase 2), whilst others may become ETSI Technical Reports (ETRs). GSM-TSs are,
for editorial reasons, still referred to in current GSM ETSs.
Transposition dates
Date of adoption of this ETS: 30 September 1995
Date of latest announcement of this ETS (doa): 31 December 1995
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 30 June 1996
Date of withdrawal of any conflicting National Standard (dow): 30 June 1996

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ETS 300 535: September 1995 (GSM 03.22 version 4.9.0)
1 General
1.1 Scope
This European Telecommunication Standard (ETS) gives an overview of the tasks undertaken by a
GSM900 or DCS1800 mobile station (MS) when in idle mode, that is, switched on but not having a
dedicated channel allocated, e.g. not making or receiving a call. It also describes the corresponding
network functions.
This ETS outlines how the requirements of the GSM 02 series Technical Specifications (especially TS
GSM 02.11) on idle mode operation shall be implemented. Further details are given in Technical
Specifications GSM 04.08 and GSM 05.08.
Clause 2 of this ETS gives a general description of the idle mode process. Clause 3 outlines the main
requirements and technical solutions of those requirements. Clause 4 describes the processes used in
idle mode. There is inevitably some overlap between these clauses.
1.2 Normative references
This ETS incorporates by dated and undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references, the
latest edition of the publication referred to applies.
[1] GSM 01.04 (ETR 100): "European digital cellular telecommunications system
(Phase 2); Abbreviations and acronyms".
[2] GSM 02.01 (ETS 300 500): "European digital cellular telecommunications
system (Phase 2); Principles of telecommunications services supported by a
GSM Public Land Mobile Network (PLMN)".
[3] GSM 02.02 (ETS 300 501): "European digital cellular telecommunications
system (Phase 2); Bearer Services (BS) supported by a GSM Public Land
Mobile Network (PLMN)".
[4] GSM 02.03 (ETS 300 502): "European digital cellular telecommunications
system (Phase 2); Teleservices supported by a GSM Public Land Mobile
Network (PLMN)".
[5] GSM 02.04 (ETS 300 503): "European digital cellular telecommunications
system (Phase 2); General on supplementary services".
[6] GSM 02.06 (ETS 300 504): "European digital cellular telecommunications
system (Phase 2); Types of Mobile Stations (MS)".
[7] GSM 02.07 (ETS 300 505): "European digital cellular telecommunications
system (Phase 2); Mobile Station (MS) features".
[8] GSM 02.08 (ETR 101): "European digital cellular telecommunications system
(Phase 2); Quality of service".
[9] GSM 02.09 (ETS 300 506): "European digital cellular telecommunications
system (Phase 2); Security aspects".
[10] GSM 02.11 (ETS 300 507): "European digital cellular telecommunications
system (Phase 2); Service accessibility".
[11] GSM 02.16 (ETS 300 508): "European digital cellular telecommunications
system (Phase 2); International Mobile station Equipment Identities (IMEI)".

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[12] GSM 02.17 (ETS 300 509): "European digital cellular telecommunications
system (Phase 2); Subscriber identity modules Functional characteristics".
[13] GSM 02.24 (ETS 300 510): "European digital cellular telecommunications
system (Phase 2); Description of Charge Advice Information (CAI)".
[14] GSM 02.30 (ETS 300 511): "European digital cellular telecommunications
system (Phase 2); Man-Machine Interface (MMI) of the Mobile Station (MS)".
[15] GSM 02.40 (ETS 300 512): "European digital cellular telecommunications
system (Phase 2); Procedures for call progress indications".
[16] GSM 02.41 (ETS 300 513): "European digital cellular telecommunications
system (Phase 2); Operator determined barring".
[17] GSM 02.81 (ETS 300 514): "European digital cellular telecommunications
system (Phase 2); Line identification supplementary services - Stage 1".
[18] GSM 02.82 (ETS 300 515): "European digital cellular telecommunications
system (Phase 2); Call Forwarding (CF) supplementary services - Stage 1".
[19] GSM 02.83 (ETS 300 516): "European digital cellular telecommunications
system (Phase 2); Call Waiting (CW) and Call Hold (HOLD) supplementary
services - Stage 1".
[20] GSM 02.84 (ETS 300 517): "European digital cellular telecommunications
system (Phase 2); MultiParty (MPTY) supplementary services - Stage 1".
[21] GSM 02.85 (ETS 300 518): "European digital cellular telecommunications
system (Phase 2); Closed User Group (CUG) supplementary services -
Stage 1".
[22] GSM 02.86 (ETS 300 519): "European digital cellular telecommunications
system (Phase 2); Advice of charge (AoC) supplementary services - Stage 1".
[23] GSM 02.88 (ETS 300 520): "European digital cellular telecommunications
system (Phase 2); Call Barring (CB) supplementary services - Stage 1".
[24] GSM 04.08 (ETS 300 557): "European digital cellular telecommunications
system (Phase 2); Mobile radio interface layer 3 specification".
[25] GSM 05.02 (ETS 300 574): "European digital cellular telecommunications
system (Phase 2); Multiplexing and multiple access on the radio path".
[26] GSM 05.08 (ETS 300 578): "European digital cellular telecommunications
system (Phase 2); Radio subsystem link control".

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1.3 Definitons and abbreviations
Abbreviations used in this ETS are listed in GSM 01.04.
Selected PLMN This is the PLMN that has been selected according to subclause 3.1, either
manually or automatically.
Available PLMN This is a PLMN where the MS has found a cell that satisfies conditions (ii) and
subclause
(iv) of 3.2.1.
Registered PLMN (RPLMN) This is the PLMN on which certain LU outcomes have occurred (see table
1).
Allowable PLMN This is a PLMN which is not in the list of forbidden PLMNs in the SIM.
Registration This is the process of camping on a cell of the PLMN and doing any necessary
LUs.
Camped on a cell The MS (ME if there is no SIM) has completed the cell selection/reselection
process and has chosen a cell from which it plans to receive all available
services. Note that the services may be limited, and that the PLMN may not be
aware of the existence of the MS (ME) within the chosen cell.
Current serving cell This is the cell on which the MS is camped.
Suitable Cell This is a cell on which an MS may camp. It must satisfy criteria (i) to (iv) of
subclause 3.2.1.
Acceptable Cell This is a cell that the MS may camp on to make emergency calls. It must satisfy
subclause
criteria (ii) and (iv) of 3.2.1.
The PLMN to which a cell belongs (PLMN identity) is given in the system information transmitted on the
BCCH (MCC + MNC part of LAI).
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2 General description of idle mode
When an MS is switched on, it attempts to make contact with a GSM public land mobile network (PLMN).
The particular PLMN to be contacted may be selected either automatically or manually. The MS looks for
a suitable cell of the chosen PLMN and chooses that cell to provide available services, and tunes to its
control channel (BCCH plus CCCH). This choosing is known as "camping on the cell". The MS will then
register its presence in the location area (LA) of the chosen cell if necessary, by means of a location
updating (LU) or IMSI attach procedure. If the MS loses coverage of a cell, it reselects onto the most
suitable alternative cell of the selected PLMN and camps on that cell. If the new cell is in a different LA, an
LU request is performed. If the MS loses coverage of a PLMN, either a new PLMN is selected
automatically, or an indication of which PLMNs are available is given to the user, so that a manual
selection can be made.
The purpose of camping on a cell in idle mode is threefold:
a) It enables the MS to receive system information from the PLMN.
b) If the MS wishes to initiate a call, it can do this by initially accessing the network on the CCCH of the
cell on which it is camped (with the exceptions defined in subclauses 3.5.3 and 3.5.4).
c) If the PLMN receives a call for the MS, it knows (in most cases) the LA of the cell in which the MS is
camped. It can then send a "paging" message for the MS on CCCHs of all the cells in the LA. The
MS will then receive the paging message because it is tuned to the CCCH of a cell in that LA, and
the MS can respond on that CCCH.
If the MS is unable to find a suitable cell to camp on, or the SIM is not inserted, or if it receives certain
responses to an LU request (e.g., "illegal MS"), it attempts to camp on a cell irrespective of the PLMN
identity, and enters a "limited service" state in which it can only attempt to make emergency calls.
The idle mode tasks can be subdivided into 3 processes:
- PLMN selection;
- Cell selection and reselection;
- Location updating.
The relationship between these processes is illustrated in Figure 1. The states and state transitions within
each process are shown in figures 2 to 4.
3 Requirements and technical solutions
The following subclauses list the main requirements of idle mode operation and give an outline of the
technical solution.
3.1 PLMN selection and roaming
The MS normally operates on its home PLMN (HPLMN). However a visited PLMN (VPLMN) may be
selected, e.g., if the MS loses coverage. There are two modes for PLMN selection:
i) Automatic mode - This mode utilises a list of PLMNs in priority order. The highest priority PLMN
which is available and allowable is selected.
ii) Manual mode - Here the MS indicates to the user which PLMNs are available. Only when the user
makes a manual selection does the MS try to obtain normal service on the VPLMN.

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There are two cases:
- International Roaming - This is where the MS receives service on a PLMN of a different country
than that of the HPLMN.
- National Roaming - This is where the MS receives service from a PLMN of the same country as
that of the HPLMN, either anywhere or on a regional basis. The MS makes a periodic search for the
HPLMN while national roaming.
To prevent repeated attempts to have national roaming service on a not allowed LA, when the MS is
informed that an LA is forbidden, the LA is added to a list of "forbidden LAs for national roaming" which is
stored in the MS. This list is deleted when the MS is switched off or when the SIM is removed.
If a "PLMN not allowed" message is received by an MS in response to an LU request from a VPLMN, that
VPLMN is added to a list of "forbidden PLMNs" in the SIM and thereafter that VPLMN will not be accessed
by the MS when in automatic mode. A PLMN is removed from the "forbidden" list if, after a subsequent
manual selection of that PLMN, there is a successful LU. This list is retained when the MS is switched off
or the SIM is removed. The HPLMN shall not be stored on the list of "forbidden PLMNs".
3.2 Camping on a cell
3.2.1 Normal camping
For normal service, the MS has to camp on a suitable cell, tune to that cell's BCCH + CCCH, and possibly
register within the PLMN so that the MS can:
a) Receive system information from the PLMN (on the BCCH), e.g., the cell options;
b) Receive paging messages from the PLMN, e.g., when there is an incoming call for the MS;
subclause
c) Initiate call setup for outgoing calls or other actions from the MS (where possible, see s
3.5.3 and 3.5.4).
The choice of such a suitable cell for the purpose of receiving normal service is referred to as "normal
camping". There are various requirements that a cell must satisfy before an MS can perform normal
camping on it:
i) It should be a cell of the selected PLMN;
ii) It should not be "barred" (see subclause 3.5.1);
iii) It should not be in an LA which is in the list of "forbidden LAs for national roaming";
iv) The radio path loss between MS and BTS must be below a threshold set by the PLMN operator.
This is estimated as shown in subclause 3.6.
Initially the MS looks for a cell which satisfies these 4 constraints ("suitable cell") by checking cells in
descending order of received signal strength. If a suitable cell is found, the MS camps on it and performs
any registration necessary. Cells can have two levels of priority, suitable cells which are of low priority are
only camped on if there are no other suitable cells of normal priority. (This is called "cell selection").
When camped on a cell the MS regularly looks to see if there is a better cell in terms of a cell re-selection
criterion, and if there is, the better cell is selected. Also if one of the other criteria changes, (e.g., the
current serving cell becomes barred), or there is a downlink signalling failure (see subclause 3.6), a new
cell is selected. (This is called "cell reselection").

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In order to speed up these processes, a list of the RF channels containing BCCH carriers of the same
PLMN is broadcast on the BCCH, see subclause 4.8. Also, the MS does not need to search all possible
RF channels to find a suitable cell. If, after searching the 30 (GSM900) or 40 (DCS1800) RF channels with
strongest received signal level, a BCCH carrier has been found but no suitable cell of the selected PLMN
has been found, the MS can stop the attempt to find a suitable cell of the selected PLMN.
3.2.2 "Camp on any cell"
If the MS cannot find a suitable cell, it attempts to camp on any acceptable cell and enter a "limited service
state", as defined in subclause 3.7.
3.3 Regional provision of service
An MS may have a "regionally restricted service" where it can only obtain service on certain LAs. If such
an MS attempts to camp on a cell of an LA for which it does not have service entitlement, when it does an
LU request, it will receive an "LA not allowed" message. In this case:
- The MS stores the forbidden LA identity (LAI) in a list of "forbidden LAIs for regional provision of
service", to prevent repeated access attempts on a cell of the forbidden LA. This list is deleted when
the MS is switched off or the SIM is removed. If the MS cannot find a suitable cell, the MS performs
the PLMN selection procedure starting at subclause 4.4.3.1 A or B.
3.4 Borders between location areas
If the MS is moving in a border area between LAs, it might repeatedly change between cells of different
LAs. Each change of LA would require an LU, which would cause a heavy signalling load and increase the
risk of a paging message being lost. To prevent this, a "CELL_RESELECT_HYSTERESIS" (CRH)
parameter is used. A cell in a different LA is only selected if it is "better", in terms of the path loss criterion
(see subclause 3.6), than all the cells in the current LA by at least the value of CRH. The CRH parameter
is broadcast on the BCCH. As the value of CRH broadcast may be different on different cells, the CRH
parameter to be used is that broadcast on the current serving cell. There is also a lower limit on the time
interval between reselection of cells on different LAs.
3.5 Barred cells and access control
3.5.1 Barred cells
The PLMN operator may decide not to allow MSs to camp on certain cells. (These cells may, for example,
only be used for handover traffic, i.e. calls which need to be handed over to other cells). Barred cell
information is broadcast on the BCCH to instruct MSs not to camp on these cells. The barred cell status
may in fact change dynamically; hence the MS needs to regularly check the BCCH system information for
this parameter.
The barred status of a cell depends both on CELL_BAR_ACCESS and on the cell's priority indicated by
CELL_BAR_QUALIFY. The effect of these two parameters is further described in TS GSM 05.08.
If a cell is barred this applies both for cell selection and reselection.
3.5.2 Prioritising cells
In general, cell prioritisation is a means of encouraging MSs to select some suitable cells in preference to
others. Since the priority comparison is only between suitable cells, prioritisation does not affect coverage.
Operators may prefer a certain type of cell not to be selected unless it is the only suitable type. For
example, umbrella cells due to their large frequency reuse distance, or microcells because the MS could
be travelling too fast for them.
3.5.2.1 For cell selection
During cell selection (see subclause 3.2.1), a cell with low priority indication will only be selected if a
suitable cell of normal priority cannot be found.

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3.5.2.2 For cell reselection
Cell prioritisation can also be achieved during cell reselection by the use of the reselection parameters
optionally broadcast. Cells are reselected on the basis of a parameter called C2 and the C2 value for each
cell is given a positive or negative offset to encourage or discourage MSs to reselect that cell. A full range
of positive and negative offsets is provided to allow the incorporation of this feature into already
operational networks.
3.5.3 Access control
Due to problems in certain areas, Network Operators may decide to restrict access from some MSs (e.g.,
in case of congestion on the AGCH), and for this reason the access control mechanism is provided.
At subscription one or more access control classes are allocated to the subscriber and stored in the SIM.
The information providing all authorised classes is broadcast on the BCCH (together with a bit indicating
whether emergency calls may be made). This information is modified dynamically and therefore the MS
has to check the BCCH before each attempt to access.
The MS ignores the Access Control information when selecting a cell to camp on, i.e. it shall not reject a
cell for camping on because access on that cell is not allowed.
3.5.4 Forbidden LA for regional provision of service
When the MS is camped on a cell, the LA of which belongs to the list of forbidden LA for regional provision
of service, the MS is not allowed to initiate establishment of a CM connection except for an emergency
call; it may respond to paging.
If the MS has received the cause 'LA not allowed', it shall ignore this fact when selecting a cell to camp on,
i.e. it shall not reject a cell for camping on because that cell is part of a LA where this cause has been
received.
3.6 Radio constraints
The MS uses a "path loss criterion" parameter C1 to determine whether a cell is suitable to camp on. C1
depends on 4 parameters:
i) The received signal level (suitably averaged);
ii) The parameter RXLEV_ACCESS_MIN, which is broadcast on the BCCH, and is related to the
minimum signal that the operator wants the network to receive when being initially accessed by an
MS;
iii) The parameter MS_TXPWR_MAX_CCH, which is also broadcast on the BCCH, and is the
maximum power that an MS may use when initially accessing the network;
iv) The maximum power of the MS.
The formula for determining C1 is given in GSM Rec 05.08.
Use of the parameter C1 enables the MS to determine whether communication is possible with the
network in the absence of interference. However because of the possibility of interference degrading the
communications, an additional safeguard is used. This is to monitor the success rate of the MS in
decoding signalling blocks of the paging subchannel. If there is a downlink signalling failure, i.e. the
success rate drops too low, this indicates probable interference on the downlink, and the MS attempts to
find another suitable cell. Downlink signalling failure monitoring is specified in GSM 05.08.
In order to optimise cell reselection, additional cell reselection parameters can be broadcast on the BCCH
of each cell. The cell reselection process employs a parameter C2 which depends on these parameters.

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The parameters used to calculate C2 are as follows:
i) CELL_RESELECT_OFFSET (see subclause 3.5.2.2);
ii) PENALTY_TIME;
When the MS places the cell on the list of the strongest carriers as specified in GSM 05.08, it starts
a timer which expires after the PENALTY_TIME. This timer will be reset when the cell is taken off
the list. For the duration of this timer, C2 is given a negative offset. This will tend to prevent fast
moving MSs from selecting the cell.
iii) TEMPORARY_OFFSET;
This is the amount of the negative offset described in (ii) above. An infinite value can be applied, but
a number of finite values are also possible.
The permitted values of these parameters and the way in which they are combined to calculate C2 are
defined in GSM 05.08.
3.7 No suitable cell (limited service state)
There are a number of situations in which the MS is unable to obtain normal service from a PLMN. These
include:
a) Failure to find a suitable cell of the selected PLMN;
b) No SIM in the MS;
c) A "PLMN not allowed" response to an LU;
d) An "illegal MS", "illegal ME" or "IMSI unknown in HLR" response to an LU. (Any SIM in the ME is
then considered 'invalid'.)
(In automatic PLMN selection mode, events (a) and (c) would normally cause a new PLMN selection, but
even here, the situation may arise when no PLMNs are available and allowable for use).
Under any of these conditions, the MS attempts to camp on an acceptable cell, irrespective of its PLMN
identity, so that emergency calls can be made if necessary. When in the limited service state with a valid
SIM, the MS shall search for available and allowable PLMNs in the manner described in subclause
4.4.3.1. To minimise the time taken to find new available PLMNs while maintaining battery life,
discontinuous search schemes may be used, see TS GSM 02.11. No LU requests are made until a valid
SIM is present and either a suitable cell is found or a manual network reselection is performed. In the
limited service state the presence of the MS need not be known to the PLMN on whose cell it has
camped. Cell reselection takes place as normal, except that a zero dB value of CRH will be used.
There are also other conditions under which only emergency calls may be made. These are shown in
table 2.
4 Overall process structure
4.1 Process goal
The aim of the idle mode processes is to achieve the following conditions ("normal service state"):
a) The registered PLMN is the selected PLMN;
b) The MS is camped on a suitable cell of the LA on which the last successful LU was performed, and
that cell has the highest value of C2 for any unbarred cell in that LA;
c) The value of C2 for the MS is not lower than the value of C2 for any suitable cell in another LA of
the selected PLMN by more than the hysteresis value CRH.

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There may be temporary conditions under which not all these are fully satisfied, e.g., during cell selection
on a PLMN or while in the process of reselecting another cell. However if the above cannot be satisfied for
a certain period of time, the MS will normally enter a "limited service state" in which it will try to camp on
an acceptable cell. In this state, only emergency calls are possible.
4.2 States description
Each of the processes of PLMN selection, cell selection and location updating can be described by a set
of states. The overall state of the mobile is thus a composite of the states of the three processes. In some
cases, an event which causes a change of state in one process may trigger a change of state in another
process, e.g., camping on a cell in a new LA triggers an LU request. The relationship between the
processes is illustrated in figure 1.
The states in which the MS may be, for each of the processes, are described below and illustrated in
figures 2 to 4. For many of the states, a fuller description can be found in other GSM Technical
Specifications, and a reference to the GSM Technical Specification and the relevant section within it, are
given after the state description.
In the event of any conflict between the diagrams and the text in this ETS, the text takes precedence.
4.3 List of states
4.3.1 List of states for the PLMN selection process
4.3.1.1 List of states for automatic mode (Figure 2a)
A1 Trying RPLMN - The MS is trying to perform a Location Update on the registered PLMN.
A2 On PLMN - The MS has successfully registered on a PLMN.
A3 Trying PLMN - The MS is trying to register on a PLMN in the ordered list of PLMNs.
A4 Wait for PLMNs to appear - There are no allowable and available PLMNs at present and the MS is
waiting for one to appear.
A5 HPLMN search in progress - The MS is trying to find if the HPLMN is available.
A6 No SIM - There is no SIM in the MS, or certain LU responses have been received.

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4.3.1.2 List of states for manual mode (Figure 2b)
M1 Trying registered PLMN - The MS is trying to perform a Location Update on the registered PLMN.
M2 On PLMN - The MS has successfully registered on a PLMN.
M3 Not on PLMN - The MS has failed to register on the selected PLMN.
M4 Trying PLMN - The MS is trying to register on a user selected PLMN.
M5 No SIM - There is no SIM in the MS, or certain LU responses have been received.
4.3.2 List of States for the cell selection process (Figure 3)
C1 Normal Cell Selection - This is the process of initial cell selection, searching all GSM or DCS RF
channels.
C2 Stored List Cell Selection - This is the process of initial cell selection where BCCH carrier
information (e.g. a BA list) for the selected PLMN is stored in the MS.
C3 Camped Normally - This is where the MS is camped on a cell of the selected PLMN and may be
able to make and receive calls. (Whether or not the MS can make and receive calls depends on the
state within the location updating process). The MS monitors received level and BCCH data and
checks whether cell reselection is needed.
C4 Normal Cell Reselection - This is where the MS has determined that cell reselection is needed and
an attempt is being made to reselect a new cell.
C5 Choose Cell - This is where the MS has returned to idle mode from "connected mode" and is
choosing a suitable cell to camp on.
C6 Any Cell Selection - This is where the MS is unable to camp normally on any cell of the selected
PLMN, or cannot obtain service because of certain responses to a location updating (LU) attempt. It
is searching for a cell of any PLMN to camp on (so that emergency calls can be made).
C7 Camped on any Cell - This is where the MS has camped on a cell irrespective of its PLMN identity,
so that emergency calls can be made.
C8 Any Cell Reselection - This is where the MS is attempting to reselect a cell, irrespective of PLMN
identity.
C9 Choose Any Cell - This is where the MS is returning to idle mode, after having entered "connected
mode" from the "camped on any cell" state to make an emergency call. It is attempting to find an
acceptable cell to camp on.
For detailed description of the behaviour in the above states see GSM 05.08.

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4.3.3 List of states for location updating (Figure 4)
The states are entered depending on responses to location update (LU) requests.
L1 Updated - The MS enters this state if an LU request is accepted. The update status on the SIM is
set to "updated".
L2 Idle, No IMSI - The MS enters this state if an LU request is rejected with cause:
a) IMSI unknown in HLR;
b) illegal ME;
c) illegal MS;
or if there is no SIM.
If a SIM is present, the update status of the SIM is set to "Roaming not allowed".
L3 Roaming not allowed - The MS enters this state if it receives an LU reject message with the cause:
a) PLMN not allowed;
b) Location area not allowed;
c) National Roaming not allowed in this location area.
The update status on the SIM is set to "Roaming not allowed".
The behaviour of the MS in the roaming not allowed state is dependent on the LU reject cause as
shown in Table 2. Additionally:
- in automatic mode, "PLMN not allowed" and "national roaming not allowed in this location
area" cause the Automatic Network Selection procedure of subclause 4.4.3.1A to be started
- in manual mode, "PLMN not allowed" and "national roaming not allowed" cause the Manual
Network Selection procedure of subclause 4.4.3.1B to be started.
L4 Not updated - The MS enters this state if any LU failure not specified for states L2 or L3 occurs, in
which cases the MS is not certain whether or not the network has received and accepted the LU
attempt. The update status on the SIM is set to "not updated".

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4.4 PLMN selection process
4.4.1 Introduction
subclause
There are two modes for PLMN selection, automatic and manual. These are described in s
4.4.3 below and illustrated in figures 2a to 2b.
4.4.2 Registration on a PLMN
In both automatic and manual modes, the concept of registration on a PLMN is used. An MS successfully
registers on a PLMN if:
a) The MS has found a suitable cell of the PLMN to camp on; and
b) An LU request from the MS has been accepted in the LA of the cell on which the MS is camped
(see table 1).
It should be noted that if registration is unsuccessful because no suitable cell could be found, the MS will
have had to search at least the 30 (GSM) or 40 (DCS) strongest RF channels (see subclause 3.2) and
therefore all the available PLMNs will potentially have been detected. If registration is unsuccessful
because of an LU failure or an LU rejection, the MS need not necessarily have already searched the 30 or
40 strongest RF channels, and would need to do so before being in a position to display to the user all
available PLMNs (see below).
4.4.3 PLMN selection
4.4.3.1 At switch-on or recovery from lack of coverage
At switch on, the MS selects and attempts to perform a Location Update on the registered PLMN, if it
exists. On recovery from lack of coverage, the MS selects the registered PLMN (if it exists) and, if
necessary (see subclause 4.6.2) attempts to perform a Location Update.
If successful registration is achieved, the MS indicates the selected PLMN.
If there is no registered PLMN, or if registration is not possible due to the PLMN being unavailable or
registration failure, the MS follows one of the following two procedures depending on its operating mode.
A) Automatic Network Selection Mode Procedure
The MS selects and attempts registration on other PLMNs, if available and allowable, in the following
order:
i) HPLMN (if not previously selected);
ii) each PLMN in the "PLMN Selector" data field in the SIM (in priority order);
iii) other PLMNs with received signal level above -85 dBm in random order;
iv) all other PLMNs in order of decreasing signal strength.
If successful registration is achieved, the MS indicates the selected PLMN.
If registration cannot be achieved because no PLMNs are available and allowable, the MS indicates "no
service" to the user, waits until a new PLMN is available and allowable and then repeats the procedure. If
there were one or more PLMNs which were available and allowable, but an LU failure made registration
on those PLMNs unsuccessful or an entry in a forbidden LAI list prevented a registration attempt, the MS
selects the first such PLMN again and enters a limited service state.
B) Manual Network Selection Mode Procedure
The MS indicates whether there are any PLMNs which are available. This includes "Forbidden PLMNs"

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If displayed, PLMNs meeting the criteria above are presented in the following order:
i) HPLMN;
ii) PLMNs contained in the "PLMN Selector" data field in the SIM (in priority order);
iii) other PLMNs with received signal level above -85 dBm in random order;
iv) all other PLMNs in order of decreasing signal strength.
The user may select his desired PLMN and the MS then initiates registration on this PLMN. (This may
take place at any time during the presentation of PLMNs). For such a registration, the MS shall ignore the
contents of the forbidden LAI and PLMN lists.
If the user does not select a PLMN, the selected PLMN shall be the one that was selected before the
PLMN selection procedure started. If no such PLMN was selected or that PLMN is no longer available,
then the MS shall attempt to camp on any acceptable cell and enter the limited service state.
4.4.3.2 User reselection
At any time the user may request the MS to initiate reselection and registration onto an alternative
available PLMN, according to the following procedures, dependent upon the operating mode.
A) Automatic Network Selection Mode
The MS selects and attempts registration on PLMNs, if available and allowable, in accordance with the
following order:
i) HPLMN;
ii) PLMNs contained in the "PLMN Selector" data field in the SIM (in priority order);
iii) Other PLMNs with the received signal level above -85 dBm in random order;
iv) All other PLMNs in order of decreasing signal strength.
The PLMN which the MS had selected prior to the start of this reselection procedure is not reselected,
unless no other PLMNs are available, allowable and have higher received signal level, in which case it is
reselected at the end of the procedure.
B) Manual Network Selection Mode
The Manual Network Selection Mode Procedure of subclause 4.4.3.1 is followed.
4.4.3.3 In VPLMN of home country
The MS shall periodically attempt to obtain service on its HPLMN. For this purpose, a value T minutes
may be stored in the SIM, T is either in the range 6 minutes to 8 hours in 6 minute steps or
...