ETSI ETS 300 578 ed.7 (1996-11)
Digital cellular telecommunications system (Phase 2) (GSM); Radio subsystem link control (GSM 05.08)
Digital cellular telecommunications system (Phase 2) (GSM); Radio subsystem link control (GSM 05.08)
RE/SMG-020508PR6
Digitalni celični telekomunikacijski sistem (faza 2) – Krmiljenje povezave radijskega podsistema (GSM 05.08)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2003
'LJLWDOQLFHOLþQLWHOHNRPXQLNDFLMVNLVLVWHP ID]D ±.UPLOMHQMHSRYH]DYH
UDGLMVNHJDSRGVLVWHPD *60
Digital cellular telecommunications system (Phase 2) (GSM); Radio subsystem link
control (GSM 05.08)
Ta slovenski standard je istoveten z: ETS 300 578 Edition 7
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 300 578
TELECOMMUNICATION November 1996
STANDARD Seventh Edition
Source: ETSI TC-SMG Reference: RE/SMG-020508PR6
ICS: 33.060.50
Key words: Digital telecommunications system, Global System for Mobile communications (GSM)
R
GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
Digital cellular telecommunications system (Phase 2);
Radio subsystem link control
(GSM 05.08)
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: secretariat@etsi.fr
Tel.: +33 4 92 94 42 00 - Fax: +33 4 93 65 47 16
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 1996. All rights reserved.
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ETS 300 578: November 1996 (GSM 05.08 version 4.17.0)
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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ETS 300 578: November 1996 (GSM 05.08 version 4.17.0)
Contents
Foreword .5
1 Scope .7
1.1 Normative references .7
1.2 Abbreviations .8
2 General.8
3 Handover.8
3.1 Overall process.8
3.2 MS measurement procedure .9
3.3 BSS measurement procedure .9
3.4 Strategy.9
4 RF power control.9
4.1 Overall process.9
4.2 MS implementation .9
4.3 MS power control range.10
4.4 BSS implementation .10
4.5 BSS power control range.10
4.6 Strategy.10
4.7 Timing .10
5 Radio link failure.10
5.1 Criterion .10
5.2 MS procedure .11
5.3 BSS procedure.11
6 Idle mode tasks .11
6.1 Introduction .11
6.2 Measurements for normal cell selection .12
6.3 Measurements for stored list cell selection.12
6.4 Criteria for cell selection and reselection .13
6.5 Downlink signalling failure.14
6.6 Measurements for Cell Reselection.14
6.6.1 Monitoring of received level and BCCH data .14
6.6.2 Path loss criteria and timings for cell re-selection .15
6.7 Release of TCH and SDCCH .16
6.7.1 Normal case .16
6.7.2 Call re-establishment.16
6.8 Abnormal cases and emergency calls.17
7 Network pre-requisites .17
7.1 BCCH carriers.17
7.2 Identification of surrounding BSS for handover measurements .17
8 Radio link measurements.18
8.1 Signal strength.19
8.1.1 General.19
8.1.2 Physical parameter.19
8.1.3 Statistical parameters.20
8.1.4 Range of parameter .20
8.2 Signal quality.20
8.2.1 General.20
8.2.2 Physical parameter.20
8.2.3 Statistical parameters.20
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8.2.4 Range of parameter. 21
8.3 Aspects of discontinuous transmission (DTX) . 22
8.4 Measurement reporting . 22
8.5 Absolute MS-BTS distance . 25
8.5.1 General . 25
8.5.2 Physical parameter . 25
9 Control parameters. 26
Annex A (informative): Definition of a basic GSM or DCS 1 800 handover and RF power control
algorithm . 29
A.1 Scope. 29
A.2 Functional requirement. 29
A.3 BSS pre-processing and threshold comparisons . 29
A.3.1 Measurement averaging process. 30
A.3.2 Threshold comparison process. 31
A.3.2.1 RF power control process. 31
A.3.2.2 Handover Process . 32
A.4 BSS decision algorithm. 32
A.4.1 Internal intracell handover according to radio criteria: (Interference problems). 33
A.4.2 Internal handover according to other criteria. 33
A.4.3 General considerations .34
A.5 Channel allocation . 34
A.6 Handover decision algorithm in the MSC . 34
History. 37
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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 specifies the Radio sub system link control implemented in the Mobile Station (MS), Base
Station System (BSS) and Mobile Switching Centre (MSC) of the GSM and DCS 1 800 systems of the
Digital cellular telecommunications system (Phase 2). Unless stated, references to GSM also include
DCS 1 800.
This seven edition is a result of further work carried out by TC-SMG and corresponds to GSM technical
specification, GSM 05.08 version 4.17.0.
The specification from which this ETS has been derived was originally based on CEPT documentation,
hence the presentation of this ETS is not in accordance with the ETSI/PNE rules.
Reference is made within this ETS to GSM Technical Specifications (GSM-TS) (See note).
Reference is also made within this ETS to GSM 0x.xx. series. The specifications in the series can be
identified, with their full title, within the normative reference Clause of this 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 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: 18 October 1996
Date of latest announcement of this ETS (doa): 28 February 1997
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 August 1997
Date of withdrawal of any conflicting National Standard (dow): 31 August 1997
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1 Scope
This European Telecommunication Standard (ETS) specifies the Radio sub-system link control
implemented in the Mobile Station (MS), Base Station System (BSS) and Mobile Switching Centre (MSC)
of the GSM and DCS 1 800 systems.
Unless otherwise specified, references to GSM also include DCS 1 800.
1.1 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): "Digital cellular telecommunication system (Phase 2);
Abbreviations and acronyms".
[2] GSM 03.03 (ETS 300 523): "Digital cellular telecommunication system
(Phase 2); Numbering, addressing and identification".
[3] GSM 03.09 (ETS 300 527): "Digital cellular telecommunication system
(Phase 2); Handover procedures".
[4] GSM 03.22 (ETS 300 535): "Digital cellular telecommunication system
(Phase 2); Functions related to Mobile Station (MS) in idle mode".
[5] GSM 04.04 (ETS 300 553): "Digital cellular telecommunication system
(Phase 2); Layer 1 General requirements".
[6] GSM 04.06 (ETS 300 555): "Digital cellular telecommunication system
(Phase 2); Mobile Station - Base Station System (MS - BSS) interface Data Link
(DL) layer specification".
[7] GSM 04.08 (ETS 300 557): "Digital cellular telecommunication system
(Phase 2); Mobile radio interface layer 3 specification".
[8] GSM 05.02 (ETS 300 574): "Digital cellular telecommunication system
(Phase 2); Multiplexing and multiple access on the radio path".
[9] GSM 05.05 (ETS 300 577): "Digital cellular telecommunication system
(Phase 2); Radio transmission and reception".
[10] GSM 05.10 (ETS 300 579): "Digital cellular telecommunication system
(Phase 2); Radio subsystem synchronization".
[11] GSM 06.11 (ETS 300 580-3): "Digital cellular telecommunication system
(Phase 2); Substitution and muting of lost frames for full rate speech channels".
[12] GSM 08.08 (ETS 300 590): "Digital cellular telecommunication system
(Phase 2); Mobile Switching Centre - Base Station System (MSC - BSS)
interface Layer 3 specification".
[13] GSM 08.58 (ETS 300 596): "Digital cellular telecommunication system
(Phase 2); Base Station Controller - Base Transceiver Station (BSC - BTS)
interface Layer 3 specification".
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[14] GSM 11.10 (ETS 300 607): "Digital cellular telecommunication system
(Phase 2); Mobile Station (MS) conformity specification".
[15] GSM 11.20 (ETS 300 609): "Digital cellular telecommunication system
(Phase 2); The GSM Base Station System (BSS) equipment specification".
1.2 Abbreviations
Abbreviations used in this ETS are listed in GSM 01.04.
2 General
The radio sub-system link control aspects that are addressed are as follows:
- Handover;
- RF Power control;
- Radio link Failure;
- Cell selection and re-selection in Idle mode.
Handover is required to maintain a call in progress as a MS passes from one cell coverage area to
another and may also be employed to meet network management requirements, e.g. relief of congestion.
Handover may occur during a call from TCH to TCH, it may also occur from DCCH to DCCH or from
DCCH to TCH, e.g. during the initial signalling period at call set-up.
The handover may be either from a channel on one cell to another channel on a surrounding cell, or
between channels on the same cell which are carried on the same frequency band. Examples are given of
handover strategies, however, these will be determined in detail by the network operator.
For a multiband MS, specified in GSM 02.06, the handover described is also allowed between any
channels on different cells which are carried on different frequency bands, e.g. between a GSM 900/TCH
and a DCS 1 800/TCH. Handover between two co-located cells, carried on different frequency bands, is
considered as inter-cell handover irrespective of the handover procedures used.
Adaptive control of the RF transmit power from an MS and optionally from the BSS is implemented in
order to optimize the uplink and downlink performance and minimize the effects of co-channel interference
in the system.
The criteria for determining radio link failure are specified in order to ensure that calls which fail either
from loss of radio coverage or unacceptable interference are satisfactorily handled by the network. Radio
link failure may result in either re-establishment or release of the call in progress.
Procedures for cell selection and re-selection whilst in Idle mode (i.e. not actively processing a call), are
specified in order to ensure that a mobile is camped on a cell with which it can reliably communicate on
both the radio uplink and downlink. The operations of an MS in Idle Mode are specified in GSM 03.22.
Information signalled between the MS and BSS is summarized in tables 1 and 2. A full specification of the
Layer 1 header is given in GSM 04.04, and of the Layer 3 fields in GSM 04.08.
3 Handover
3.1 Overall process
The overall handover process is implemented in the MS, BSS and MSC. Measurement of radio
subsystem downlink performance and signal strengths received from surrounding cells, is made in the
MS. These measurements are signalled to the BSS for assessment. The BSS measures the uplink
performance for the MS being served and also assesses the signal strength of interference on its idle
traffic channels. Initial assessment of the measurements in conjunction with defined thresholds and
handover strategy may be performed in the BSS. Assessment requiring measurement results from other
BTS or other information resident in the MSC, may be performed in the MSC.
GSM 03.09 describes the handover procedures to be used in PLMNs.
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3.2 MS measurement procedure
A procedure shall be implemented in the MS by which it monitors the downlink RX signal level and quality
from its serving cell and the downlink RX signal level and BSIC of surrounding BTS. The method of
identification of surrounding BTS is described in section 7.2. The requirements for the MS measurements
are given in section 8.1.
3.3 BSS measurement procedure
A procedure shall be implemented in the BSS by which it monitors the uplink RX signal level and quality
from each MS being served by the cell. A procedure shall be implemented by which the BSS monitors the
levels of interference on its idle traffic channels.
3.4 Strategy
The handover strategy employed by the network for radio link control determines the handover decision
that will be made based on the measurement results reported by the MS/BSS and various parameters set
for each cell. Network directed handover may also occur for reasons other than radio link control, e.g. to
control traffic distribution between cells. The exact handover strategies will be determined by the network
operator, a detailed example of a basic overall algorithm appears in annex A. Possible types of handover
are as follows:
Inter-cell handover:
Intercell handover from the serving cell to a surrounding cell will normally occur either when the
handover measurements show low RXLEV and/or RXQUAL on the current serving cell and a better
RXLEV available from a surrounding cell, or when a surrounding cell allows communication with a
lower TX power level. This typically indicates that an MS is on the border of the cell area.
Intercell handover may also occur from the DCCH on the serving cell to a TCH on another cell
during call establishment. This may be used as a means of providing successful call establishment
when no TCH resource is available on the current serving cell.
Inter-cell handover between cells using different frequency bands is allowed for a multi band MS.
Intra-cell handover:
Intra-cell handover from one channel/timeslot in the serving cell to another channel/timeslot in the
same cell will normally be performed if the handover measurements show a low RXQUAL, but a
high RXLEV on the serving cell. This indicates a degradation of quality caused by interference even
though the MS is situated within the serving cell. The intra-cell handover should provide a channel
with a lower level of interference. Intra-cell handover can occur either to a timeslot on a new carrier
or to a different timeslot on the same carrier.
GSM 08.08 defines the causes for handover that may be signalled from BSS to MSC.
4 RF power control
4.1 Overall process
RF power control is employed to minimize the transmit power required by MS or BSS whilst maintaining
the quality of the radio links. By minimizing the transmit power levels, interference to co-channel users is
reduced.
4.2 MS implementation
RF power control shall be implemented in the MS.
The power control level to be employed by the MS is indicated by means of the power control information
sent either in the layer 1 header of each downlink SACCH message block (see GSM 04.04), or in a
dedicated signalling block (see GSM 04.08).
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The MS shall employ the most recently commanded power control level appropriate to the channel for all
transmitted bursts on either a TCH (including handover access burst), FACCH, SACCH or SDCCH. If the
commanded power control level is not supported by the MS as defined by its power class in GSM 05.05,
the MS shall act as though the closest supported power control level had been broadcast.
The MS shall confirm the power control level that it is currently employing in the uplink SACCH L1 header.
The indicated value shall be the power control level actually used by the mobile for the last burst of the
previous SACCH period.
When accessing a cell on the RACH (random access) and before receiving the first power command
during a communication on a DCCH or TCH (after an IMMEDIATE ASSIGNMENT), all GSM and class 1
and class 2 DCS 1 800 MS shall use the power level defined by the MS_TXPWR_MAX_CCH parameter
broadcast on the BCCH of the cell, or if MS_TXPWR_MAX_CCH corresponds to a power control level not
supported by the MS as defined by its power class in GSM 05.05, the MS shall act as though the closest
supported power control level had been broadcast. The class 3 DCS 1 800 MS shall use the power level
defined by MS TXPWR MAX CCH plus the value POWER OFFSET also broadcast on the BCCH of the
cell.
4.3 MS power control range
The range over which a MS shall be capable of varying its RF output power shall be from its maximum
output down to its minimum, in steps of nominally 2 dB.
GSM 05.05 gives a detailed definition of the RF power level step size and tolerances.
4.4 BSS implementation
RF power control may optionally be implemented in the BSS.
4.5 BSS power control range
The range over which the BSS shall be capable of reducing its RF output power from its maximum level
shall be nominally 30 dB, in 15 steps of nominally 2 dB.
GSM 05.05 gives a detailed definition of the RF power level step size and tolerances.
4.6 Strategy
The RF power control strategy employed by the network determines the ordered power level that is
signalled to the MS, and the power level that is employed by the BSS.
The power level to be employed in each case will be based on the measurement results reported by the
MS/BTS and various parameters set for each cell. The exact strategies will be determined by the network
operator. A detailed example of a basic algorithm appears in annex A.
4.7 Timing
Upon receipt of a command from the SACCH to change its power level, the MS shall change to the new
level at a rate of one nominal 2 dB power control step every 60 ms (13 TDMA frames), i.e. a range change
of 15 steps should take about 900 ms. The change shall commence at the first TDMA frame belonging to
the next reporting period (as specified in 8.4). The MS shall change the power one nominal 2 dB step at a
time, at a rate of one step every 60 ms following the initial change, irrespective of whether actual
transmission takes place or not.
In case of channel change, the commanded power level shall be applied on the new channel immediately.
5 Radio link failure
5.1 Criterion
The criterion for determining Radio Link Failure in the MS shall be based on the success rate of decoding
messages on the downlink SACCH.
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5.2 MS procedure
The aim of determining radio link failure in the MS is to ensure that calls with unacceptable voice/data
quality, which cannot be improved either by RF power control or handover, are either re-established or
released in a defined manner. In general the parameters that control the forced release should be set
such that the forced release will not normally occur until the call has degraded to a quality below that at
which the majority of subscribers would have manually released. This ensures that, for example, a call on
the edge of a radio coverage area, although of bad quality, can usually be completed if the subscriber
wishes.
The radio link failure criterion is based on the radio link counter S. If the MS is unable to decode a SACCH
message (BFI=1),S is decreased by 1. In the case of a successful reception of a SACCH message
(BFI=0) S is increased by 2. In any case S shall not exceed the value of RADIO_LINK_TIMEOUT. If
S reaches 0 a radio link failure shall be declared. The action to be taken is specified in GSM 04.08. The
RADIO_LINK_TIMEOUT parameter is transmitted by each BSS in the BCCH data (see table 1).
The MS shall continue transmitting as normal on the uplink until S reaches 0.
The algorithm shall start after the assignment of a dedicated channel and S shall be initialized to
RADIO_LINK_TIMEOUT.
The detailed operation shall be as follows:
- The radio link time-out algorithm shall be stopped at the reception of a channel change command.
- (Re-)initialization and start of the algorithm shall be done whenever the MS switches to a new
channel (this includes the old channel in assignment and handover failure cases), at the latest when
the main signalling link (see GSM 04.08) has been established.
- The RADIO_LINK_TIMEOUT value used at (re-)initialization shall be that used on the previous
channel (in the Immediate Assignment case the value received on the BCCH), or the value received
on SACCH if the MS has received a RADIO_LINK_TIMEOUT value on the new channel before the
initialization.
- If the first RADIO_LINK_TIMEOUT value on the SACCH is received on the new channel after the
initialization, the counter shall be re-initialized with the new value.
5.3 BSS procedure
The criteria for determining radio link failure in the BSS should be based upon either the error rate on the
uplink SACCH or on RXLEV/RXQUAL measurements of the MS. The exact criteria to be employed shall
be determined by the network operator.
6 Idle mode tasks
6.1 Introduction
Whilst in idle mode, an MS shall implement the cell selection and re-selection procedures described in
GSM 03.22. These procedures make use of measurements and sub-procedures described in this section.
The procedures ensure that the MS is camped on a cell from which it can reliably decode downlink data
and with which it has a high probability of communications on the uplink. Once the MS is camped on a
cell, access to the network is allowed.
This section makes use of terms defined in GSM 03.22.
The MS shall not use the discontinuous reception (DRX) mode of operation (i.e. powering itself down
when it is not expecting paging messages from the network) while performing the cell selection algorithm
defined in GSM 03.22. However use of powering down is permitted at all other times in idle mode.
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For the purpose of cell selection and reselection, the MS shall be capable of detecting and synchronizing
to a BCCH carrier and read the BCCH data at reference sensitivity level and reference interference levels
as specified in GSM 05.05. An MS in idle mode shall always fulfil the performance requirement specified
in GSM 05.05 at levels down to reference sensitivity level or reference interference level. The allowed
error rates (see GSM 05.05) might impact the cell selection and reselection procedure, e.g. trigger cell
reselection. Moreover, one consequence of the allowed error rates is that in the case of no frequency
hopping and a TU3 (TU1.5 for DCS 1 800) propagation profile it can not be expected that an MS will
respond to paging unless the received level is 2 dB higher than the specified reference level.
For the purposes of cell selection and reselection, the MS is required to maintain an average of received
signal strengths for all monitored frequencies. These quantities termed the "receive level averages", shall
be unweighted averages of the received signal strengths measured in dBm. The accuracy of the signal
strength measurements for idle mode tasks shall be the same as for radio link measurements (see
section 8.1.2).
The times given in sections 6.2, 6.3 and 6.6 refer to internal processes in the MS required to ensure that
the MS camps as quickly as possible to the most appropriate cell.
For the cell selection, the MS shall be able to select the correct (fourth strongest) cell and be able to
respond to paging on that cell within 30 seconds of switch on, when the three strongest cells are not
suitable. This assumes a valid SIM with PIN disabled and ideal radio conditions.
The tolerance on all the timing requirements in section 6 is ± 10 %, except for PENALTY_TIME where it is
± 2 s.
6.2 Measurements for normal cell selection
The measurements of this section shall be performed by an MS which has no prior knowledge of which
GSM or DCS 1 800 RF channels are BCCH carriers.
The MS shall search all RF channels in the system (124 for P-GSM, 174 for E-GSM and 374 for
DCS 1 800), take readings of received RF signal strength on each RF channel, and calculate the received
level average for each. The averaging is based on at least five measurement samples per RF carrier
spread over 3 to 5 s, the measurement samples from the different RF carriers being spread evenly during
this period.
A multi band MS shall search all channels within its bands of operation as specified above. The number of
channels searched will be the sum of channels on each band of operation.
BCCH carriers can be identified by, for example, searching for frequency correction bursts. On finding a
BCCH carrier, the MS shall attempt to synchronize to it and read the BCCH data.
The maximum time allowed for synchronization to a BCCH carrier is 0.5 s, and the maximum time allowed
to read the BCCH data, when being synchronized to a BCCH carrier, is 1.9 s.
6.3 Measurements for stored list cell selection
The MS may include optional storage of BCCH carrier information when switched off as detailed in
GSM 03.22. For example, the MS may store the BCCH carriers in use by the PLMN selected when it was
last active in the GSM 900 or DCS 1 800 network. The BCCH list may include BCCH carriers from more
than one band in a multi band operation PLMN. A MS may also store BCCH carriers for more than one
PLMN which it has selected previously (e.g. at national borders or when more than one PLMN serves a
country), in which case the BCCH carrier lists must be kept quite separate.
The stored BCCH carrier information used by the MS may be derived by a variety of different methods.
The MS may use the BA_RANGE information element, which, if transmitted in the channel release
message (see GSM 04.08), indicates ranges of carriers which include the BCCH carriers in use over a
wide area or even the whole PLMN. It should be noted that the BA(BCCH) list might only contain carriers
in use in the vicinity of the cell on which it was broadcast, and therefore might not be appropriate if the MS
is switched off and moved to a new location.
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The BA_RANGE information element contains the Number of Ranges parameter (defined as NR) as well
as NR sets of parameters RANGEi_LOWER and RANGEi_HIGHER. The MS should interpret these to
mean that all the BCCH carriers of the network have ARFCNs in the following ranges:
Range1 = ARFCN(RANGE1_LOWER) to ARFCN(RANGE1_HIGHER);
Range2 = ARFCN(RANGE2_LOWER) to ARFCN(RANGE2_HIGHER);
RangeNR = ARFCN(RANGENR_LOWER) to ARFCN(RANGENR_HIGHER).
If RANGEi_LOWER is greater than RANGEi_HIGHER, the range shall be considered cyclic and
encompasses carriers with ARFCN from range RANGEi_LOWER to 1023 and from 0 to
RANGEi_HIGHER. If RANGEi_LOWER equals RANGEi_HIGHER then the range shall only consist of the
carrier whose ARFCN is RANGEi_LOWER.
If an MS includes a stored BCCH carrier list of the selected PLMN it shall perform the same
measurements as in section 6.2 except that only the BCCH carriers in the list need to be measured.
If stored list cell selection is not successful, then as defined in GSM 03.22, normal cell selection shall take
place. Since information concerning a number of channels is already known to the MS, it may assign high
priority to measurements on the strongest carriers from which it has not previously made attempts to
obtain BCCH information, and omit repeated measurements on the known ones.
6.4 Criteria for cell selection and reselection
The path loss criterion parameter C1 used for cell selection and reselection is defined by:
C1 = (A - Max(B,0))
where
A = Received Level Average - RXLEV_ACCESS_MIN
B = MS_TXPWR_MAX_CCH - P
except for the class 3 DCS 1 800 MS where:
B = MS_TXPWR_MAX_CCH + POWER OFFSET - P
RXLEV_ACCESS_MIN = Minimum received level at the MS required for access
to the system.
MS_TXPWR_MAX_CCH = Maximum TX power level an MS may use when
accessing the system until otherwise commanded.
POWER OFFSET = The power offset to be used in conjunction with the
MS TXPWR MAX CCH parameter by the class 3
DCS 1 800 MS.
P = Maximum RF output power of the MS.
All values are expressed in dBm.
The path loss criterion (GSM 03.22) is satisfied if C1 > 0.
The reselection criterion C2 is used for cell reselection only and is defined by:
C2 = C1 + CELL_RESELECT_OFFSET - TEMPORARY OFFSET * H(PENALTY_TIME - T)
for PENALTY_TIME <> 11111
C2 = C1 - CELL_RESELECT_OFFSET for PENALTY_TIME = 11111
where
For non-serving cells:
H(x) = 0 for x < 0
= 1 for x ≥ 0
For serving cells:
H(x) = 0
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T is a timer implemented for each cell in the list of strongest carriers (see section 6.6.1). T shall be
started from zero at the time the cell is placed by the MS on the list of strongest carriers, except
when the previous serving cell is placed on the list of strongest carriers at cell reselection. In this,
case, T shall be set to the value of PENALTY_TIME (i.e. expired).
CELL_RESELECT_OFFSET applies an offset to the C2 reselection criterion for that cell.
NOTE: CELL_RESELECT_OFFSET may be used to give different priorities to different bands
when multiband operation is used.
TEMPORARY_OFFSET applies a negative offset to C2 for the duration of PENALTY_TIME after
the timer T has started for that cell.
PENALTY_TIME is the duration for which TEMPORARY_OFFSET applies The all ones bit pattern
on the PENALTY_TIME parameter is reserved to change the sign of CELL_RESELECT_OFFSET
and the value of TEMPORARY_OFFSET is ignored as indicated by the equation defining C2.
CELL_RESELECT_OFFSET, TEMPORARY_OFFSET and PENALTY_TIME are cell reselection
parameters which are broadcast on the BCCH of the cell when CELL_RESELECT_PARAM_IND
(see table 1) is set to 1. If CELL_RESELECT_PARAM_IND is set not received or received and set
to 0, then the MS should take CELL_BAR_QUALIFY as 0, also in this case the cell reselection
parameters take a value of 0 and therefore C2 = C1. The use of C2 is described in GSM 03.22.
These parameters are used to ensure that the MS is camped on the cell with which it has the highest
probability of successful communication on uplink and downlink.
6.5 Downlink signalling failure
The downlink signalling failure criterion is based on the downlink signalling failure counter DSC. When the
MS camps on a cell, DSC shall be initialized to a value equal to the nearest integer to 90/N where N is the
BS_PA_MFRMS parameter for that cell (see GSM 05.02). Thereafter, whenever the MS attempts to
decode a message in its paging subchannel; if a message is successfully decoded (BFI=0) DSC is
increased by 1, (however never beyond the nearest integer to 90/N), otherwise DSC is decreased by 4.
When DSC reaches 0, a downlink signalling failure shall be declared.
NOTE: The network sends the paging subchannel for a given MS every BS_PA_MFRMS
multiframes. The requirement for network transmission on the paging subchannel is
specified in GSM 04.08. The MS is required to attempt to decode a message every
time its paging subchannel is sent.
A downlink signalling failure shall result in cell reselection.
6.6 Measurements for Cell Reselection
Upon completion of cell selection and when starting the cell reselection tasks, the MS shall synchronize to
and read the BCCH information for the 6 strongest non-serving carriers (in the BA) as quickly as possible
within the times specified in section 6.6.1. For multi band mobile stations the strongest non-serving
carriers may belong to different frequency bands.
6.6.1 Monitoring of received level and BCCH data
Whilst in idle mode an MS shall continue to monitor all BCCH carriers as indicated by the BCCH allocation
(BA - See table 1). A running average of received level in the preceding 5 to:
Max {5 , ((5 * N + 6) DIV 7) * BS_PA_MFRMS / 4}
seconds shall be maintained for each carrier in the BCCH allocation. N is the number of non-serving cell
BCCH carriers in BA and the parameter BS_PA_MFRMS is defined in GSM 05.02.
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ETS 300 578: November 1996 (GSM 05.08 version 4.17.0)
The same number of measurement samples shall be taken for all non-serving cell BCCH carriers of the
BA list, and the samples allocated to each carrier shall as far as possible be uniformly distributed over
each evaluation period. At least 5 received level measurement samples are required per receive level
average value. New sets of receive level average values shall be calculated as often as possible.
For the serving cell, receive level measurement samples shall be taken at least for each paging block of
the MS. The receive level average shall be a running average determined using samples collected over a
period of 5 s or five consecutive paging blocks of that MS, whichever is the greater period. New receiving
level average value shall be calculated as often as possible.
The list of the 6 strongest non-serving carriers shall be updated at least as often as the duration of the
running average defined for measurements on the BCCH allocation and may be updated more frequently.
In order to minimize power consumption, MS that employ DRX (i.e. power down when paging blocks are
not due) should monitor the signal strengths of non-serving cell BCCH carriers during the frames of the
paging block that they are required to listen to. The MS shall include the BCCH carrier of the current
serving cell (i.e. the cell the MS is camped on) in this measurement routine. Received level measurement
samples can thus be taken on several non-serving cell BCCH carriers and on the serving carrier during
each paging block.
The MS shall attempt to decode the full BCCH data of the serving cell at least every 30 seconds.
The MS shall attempt to decode the BCCH data block that contains the parameters affecting cell
reselection for each of the 6 strongest non-serving cell BCCH carriers at least every 5 minutes. When the
MS recognizes that a new BCCH carrier has become one of the 6 strongest, the BCCH data shall be
decoded for the new carrier within 30 seconds.
The MS shall attempt to check the BSIC for each of the 6 strongest non-serving cell BCCH carriers at
least every 30 seconds, to confirm that it is monitoring the same cell. If a change of BSIC is detected then
the carrier shall be treated as a new carrier and the BCCH data redetermined.
When requested by the user, the MS shall determine which PLMNs are available (Manual Mode) or
available and allowable (Automatic Mode) (see GSM 03.22) within 15 seconds (for GSM 900) or
20 seconds (for DCS 1 800). A multi band MS shall perform the same procedures in all bands of operation
within the sum of time constraints in the respective band of operation.
In both cases, this monitoring shall be done so as to minimize interruptions to the monitoring of the PCH.
The maximum time allowed for synchronization to a BCCH carrier is 0.5 s, and the maximum time allowed
to read the BCCH data, when being synchronized to a BCCH carrier, is 1.9 s.
6.6.2 Path loss criteria and timings for cell re-selection
The MS is required to perform the following measurements (see GSM 03.22) to ensure that the path loss
criterion to the serving cell is acceptable.
At least every 5 s the MS shall calculate the value of C1 and C2 for the serving cell and re-calculate C1
and C2 values for non serving cells (if necessary). The MS shall then check whether:
i) The path loss criterion (C1) for current serving cell falls below zero for a period of 5 seconds. This
indicates that the path loss to the cell has become too high.
ii) The calculated value of C2 for a non-serving suitable cell exceeds the value of C2 for the serving
cell for a period of 5 seconds, except in the case of the new cell being in a different location area in
which case the C2 value for the new cell shall exceed the C2 value of the serving cell by at least
CELL_RESELECT_HYSTERESIS dB as defined by the BCCH data from the current serving cell,
for a period of 5 seconds. This indicates that it is a better cell.
In case ii) above, cell reselection shall not take place if there was a cell reselection within the previous
15 seconds. Cell reselection for any other reason (see GSM 03.22) shall take place imme
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