ETSI ETS 300 540 ed.2 (1996-01)

Digital cellular telecommunications system (Phase 2) (GSM); Transmission planning aspects of the speech service in the GSM Public Land Mobile Network (PLMN) system (GSM 03.50)

RE/SMG-020350P

Digitalni celični telekomunikacijski sistem (faza 2) – Vidiki načrtovanja prenosa govorne storitve prek GSM javnega kopenskega mobilnega omrežja (PLMN) (GSM 03.50)

General Information

• Status: Published
• Publication Date: 01-Feb-1996
• Technical Committee: SMG 2 - Radio
• Current Stage: 12 - Completion
• Due Date: 12-Jan-1996
• Completion Date: 02-Feb-1996
• Ref Project: SIST ETS 300 540 E2:2003 - Digital cellular telecommunications system (Phase 2) (GSM); Transmission planning aspects of the speech service in the GSM Public Land Mobile Network (PLMN) system (GSM 03.50)

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2003
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JRYRUQHVWRULWYHSUHN*60MDYQHJDNRSHQVNHJDPRELOQHJDRPUHåMD3/01*60

Digital cellular telecommunications system (Phase 2) (GSM); Transmission planning
aspects of the speech service in the GSM Public Land Mobile Network (PLMN) system
(GSM 03.50)
Ta slovenski standard je istoveten z: ETS 300 540 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 300 540
TELECOMMUNICATION January 1996
STANDARD Second Edition
Source: ETSI TC-SMG Reference: RE/SMG-020350P
ICS: 33.060.50
Digital cellular telecommunications system, Global System Mobile communications (GSM)
Key words:
Digital cellular telecommunications system (Phase 2);
Transmission planning aspects of the speech service in the
GSM Public Land Mobile Network (PLMN) system
(GSM 03.50)
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 1996. All rights reserved.
New presentation - see History box

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ETS 300 540: January 1996 (GSM 03.50 Version 4.2.0)
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 300 540: January 1996 (GSM 03.50 Version 4.2.0)
Contents
Foreword .7
1 General.9
1.1 Scope.9
1.2 Normative references .9
1.3 Definitions and abbreviations.11
1.4 Introduction .12
2 Network configurations.12
2.1 General .12
2.2 Model of the PLMN .12
2.3 Interfaces .12
2.4 Configurations of Connections.13
2.4.1 General Configurations of Connections .13
2.4.2 Reference configurations to illustrate delay and echo control issues.13
2.5 4-wire circuits in the PLMN .14
3 Transmission performance .14
3.1 Overall Loss/Loundness ratings .14
3.1.1 Connections with handset MSs .15
3.1.2 Connections with handsfree MSs using loudspeakers.15
3.1.3 Connections with headset MSs .16
3.2 Stability Loss.16
3.3 Delay.16
3.3.1 General.16
3.3.2 Sources of delay.17
3.3.2.1 Elements of the PLMN that cause delay.17
3.3.2.2 Elements of the PSTN that cause delay.17
3.3.3 Effects of delay.17
3.3.4 Allocation of delay to the PLMN .18
3.3.4.1 Allocation of delay to the PLMN when using a full rate
system .18
3.3.4.2 Allocation of delay to the PLMN when using a half rate
system .18
3.3.5 Delay of various network configurations.18
3.3.5.1 National and international connections with no echo
control in the PSTN (reference configurations A).18
3.3.5.2 National and international connections with echo control
in the PSTN (reference configurations B).18
3.3.5.3 Connections where re-routing leads to a significant
increase in transmission path length (reference
configurations C) .18
3.3.6 Delay related requirements on the MS.19
3.3.6.1 Full rate MS .19
3.3.6.2 Half rate MS.19
3.4 Echo.19
3.4.1 General.19
3.4.2 Electrical echo control in the PLMN (Reference configurations A) .19
3.4.3 Acoustic echo control in the PLMN .20
3.4.3.1 Acoustic echo control in a handsfree MS .20
3.4.3.2 Acoustic echo control in a handset MS .20
3.4.3.3 Acoustic echo control in a headset MS .20
3.4.4 Interaction between tandem echo control devices (reference
configurations B & C) .20
3.5 Clipping .20
3.5.1 General.20
3.5.2 Properties of voice switches in the PLMN.21

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3.5.3 Problems of tandem voice switching . 21
3.6 Idle channel noise . 21
3.6.1 Sending. 21
3.6.2 Receiving . 21
3.7 Noise contrast . 22
3.7.1 General . 22
3.7.2 Elements of a PLMN which can cause noise contrast impairment. 22
3.7.3 Reduction of noise contrast . 22
3.7.3.1 Reduction of noise contrast by limiting the noise received
by the microphone. 22
3.7.3.1.1 Headset MS. 23
3.7.3.1.2 Handset MS. 23
3.7.3.1.3 Handsfree MS . 23
3.7.3.2 Reduction of noise contrast by insertion of comfort noise . 23
3.7.4 Consequence of the introduction of high comfort noise levels on other
voice-operated devices. 23
3.8 Sensitivity/frequency characteristics . 23
3.8.1 Headset and Handset MSs. 23
3.8.1.1 Sending. 23
3.8.1.2 Receiving . 24
3.8.2 Handsfree MS. 24
3.9 Distortion . 24
3.9.1 Sending. 24
3.9.2 Receiving . 25
3.10 Sidetone . 26
3.10.1 Sidetone loss . 26
3.10.2 Sidetone distortion . 26
3.11 Out-of-band signals. 26
3.11.1 Discrimination against out-of-band input signals . 26
3.11.2 Spurious out-of-band signals. 27
3.12 Requirements for information tones. 27
3.13 Crosstalk . 27
3.13.1 Near and far end crosstalk . 27
3.13.2 Go/return crosstalk . 27
Annex A (informative): Considerations on the Acoustic Interface of the Mobile Station . 37
A.1 Handsfree MS. 37
A.2 Handset MS. 37
A.3 Headset MS. 37
A.4 Inter-reaction with DTX. 37
Annex B (normative): Transmission requirements testing. 38
B.1 Loudness ratings . 38
B.1.1 Sending Loudness Rating (SLR). 38
B.1.2 Receiving Loudness Rating (RLR). 38
B.2 Idle Channel Noise . 38
B.2.1 Sending . 38
B.2.2 Receiving. 38
B.3 Sensitivity/frequency Characteristics . 38
B.3.1 Sending . 38
B.3.2 Receiving. 39
B.4 Distortion. 39
B.4.1 Sending . 39
B.4.2 Receiving. 39

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B.5 Variation of gain with input level.39
B.5.1 Sending.39
B.5.2 Receiving .40
B.6 Sidetone .40
B.6.1 Talker sidetone (STMR).40
B.6.2 Listener sidetone (LSTR).40
B.7 Sidetone distortion.41
B.8 Out-of-band signals.41
B.8.1 Discrimination against out-of-band input signal .41
B.8.2 Spurious out-of-band signals .41
B.9 Acoustic echo loss.41
Annex C (normative): MS delay requirement definition .42
C.1 Full rate MS delay requirement definition.42
C.2 Half rate MS delay requirement definition .42
History.44

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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 describes the transmission planning aspects pertaining to the speech service within the digital
cellular telecommunications system (Phase 2). This ETS corresponds to GSM Technical Specification
(GSM-TS) GSM 03.50 version 4.2.0.
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).
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: 31 January 1996
Date of latest announcement of this ETS (doa): 30 April 1996
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 October 1996
Date of withdrawal of any conflicting National Standard (dow): 31 October 1996

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1 General
1.1 Scope
This European Telecommunication Standard (ETS) is concerned with the transmission planning aspects
pertaining to the speech service in the pan-European PLMN system. Due to technical and economic
factors, there cannot be full compliance with the general characteristics of international telephone
connections and circuits recommended by CCITT.
This ETS gives guidance as to the precautions, measures and minimum requirements needed for
successful interworking of the PLMN with the national and international PSTN. The Recommendation
identifies a number of routing and network configurations. The objective is to reach a quality as close as
possible to CCITT standards in order to safeguard the performance seen by PSTN customers.
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. Unless otherwise stated, all references to CCITT
Recommendations are from the Blue Book (1989).
[1] GSM 01.04 (ETR 100): "European digital cellular telecommunication system
(Phase 2); Abbreviations and acronyms".
[2] GSM 03.04 (ETS 300 524): "European digital cellular telecommunication system
(Phase 2); Signalling requirements relating to routing of calls to mobile
subscribers".
[3] GSM 06.01 (ETS 300 580-1): "European digital cellular telecommunication
system (Phase 2); Full rate speech processing functions".
[4] GSM 06.10 (ETS 300 580-2): "European digital cellular telecommunication
system (Phase 2); Full rate speech transcoding".
[5] GSM 06.11 (ETS 300 580-3): "European digital cellular telecommunication
system (Phase 2); Substitution and muting of lost frames for full rate speech
channels".
[6] GSM 06.12 (ETS 300 580-4): "European digital cellular telecommunication
system (Phase 2); Comfort noise aspect for full rate speech traffic channels".
[7] GSM 06.31 (ETS 300 580-5): "European digital cellular telecommunication
system (Phase 2); Discontinuous Transmission (DTX) for full rate speech traffic
channel".
[8] GSM 06.32 (ETS 300 580-6): "European digital cellular telecommunication
system (Phase 2); Voice Activity Detection (VAD)".
[9] GSM 06.02 (ETS 300 581-1): "European digital cellular telecommunication
system (Phase 2); Half rate speech processing functions".
[10] GSM 06.20 (ETS 300 581-2): "European digital cellular telecommunication
system (Phase 2); Half rate speech transcoding".
[11] GSM 06.21 (ETS 300 581-3): "European digital cellular telecommunication
system (Phase 2); Substitution and muting of lost frames for half rate speech
traffic channels".
[12] GSM 06.22 (ETS 300 581-4): "European digital cellular telecommunication
system (Phase 2); Comfort noise aspects for half rate speech traffic channels".

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[13] GSM 06.41 (ETS 300 581-5): "European digital cellular telecommunication
system (Phase 2); Discontinuous Transmission (DTX) for half rate speech traffic
channels".
[14] GSM 06.42 (ETS 300 581-6): "European digital cellular telecommunication
system (Phase 2); Voice Activity Detection (VAD) for half rate speech traffic
channels".
[15] ETS 300 085 (1990): "Integrated Services Digital Network (ISDN); 3,1 kHz
telephony teleservice; Attachment requirements for handset terminals".
[16] CCITT Recommendation G.103: "Hypothetical reference connections".
[17] CCITT recommendation G.111: "Loudness ratings (LRs) in an international
connections".
[18] CCITT Recommendation G.113: "Transmission impairments".
[19] CCITT Recommendation G.114: "Mean one-way propagation time".
[20] CCITT Recommendation G.121: "Loudness ratings (LRs) of national systems".
[21] CCITT Recommendation G.122: "Influence of national systems on stability,
talker echo, and listener echo in international connections".
[22] CCITT Recommendation G.131: "Stability and echo".
[23] CCITT Recommendation G.165: "Echo cancellers".
[24] CCITT Recommendation G.223: "Assumptions for the calculation of noise on
hypothetical reference circuits for telephony".
[25] CCITT Recommendation G.703: "Physical/electrical characteristics of
hierarchical digital interfaces".
[26] CCITT Recommendation G.711: "Pulse code modulation (PCM) of voice
frequencies".
[27] CCITT Recommendations G.712: "Transmission performance characteristics of
pulse code modulation".
[28] CCITT Recommendations G.714: "Separate performance characteristics for the
send and receive sides of PCM channels applicable to 4-wire voice frequency
interfaces".
[29] CCITT Recommendations M.1020: "Characteristics of special quality".
[30] CCITT Recommendations M.1025: "Characteristics of special quality
international leased circuits with basic bandwidth conditioning".
[31] CCITT Recommendations M.1030: "Characteristics of ordinary quality
international leased circuits forming part of private switched telephone
networks".
[32] CCITT Recommendations M.1040: "Characteristics of ordinary quality
international leased circuits".
[33] CCITT Recommendation O.132 (1988), "Specification for a quantizing distortion
measuring apparatus using a sinusoidal test signal."
[34] CCITT Recommendation P.11: "Effect of transmission impairments".

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[35] CCITT Recommendation P.34: "Transmission characteristics of hands-free
telephones".
[36] CCITT Recommendation P.38: "Transmission characteristics of operator
telephone systems (OTS)".
[37] CCITT Recommendation P.50: "Artificial voices".
[38] CCITT Recommendation P.51 (1988), "Artificial mouths and artificial ears."
[39] CCITT Recommendation P.64 (1988), "Determination of sensitivity/frequency
characteristics of local telephone systems to permit calculation of their loudness
ratings."
[40] CCITT Recommendation P.76 (1988), "Determination of loudness ratings;
fundamental principles."
[41] CCITT Recommendation P.79 (1988), "Calculation of loudness ratings."
[42] CCITT Recommendation Q.35: "Technical characteristics of tones for the
telephone service".
[43] CCITT Recommendation Q.551: "Transmission characteristics of digital
exchanges".
[44] CCITT Blue Book (1988), Volume V, Supplement 13, "Noise spectra."
[45] ISO 3 - 1973, "Preferred numbers - series of preferred numbers."
1.3 Definitions and abbreviations
In addition to those below, the definitions and abbreviations used in this specification are listed in
GSM 01.04.
ADC Analogue to Digital Converter
ADPCM Adaptive Differential Pulse Code Modulation
AEC Acoustic Echo Control
BSC' Base Station Controller (excluding transmission systems
BTS' Base Transceiver Station (excluding transmission systems)
DAC Digital to Analogue Converter
DMR Digital Mobile Radio
DSI Digital Speech Interpolation
EEC Electric Echo Control
EL Echo Loss
ERP Ear Reference Point
FDM Frequency Division Multiplex
LSTR Listener Sidetone Rating
MRP Mouth Reference Point
OLR Overall Loudness Rating
PCM Pulse Code Modulation
POI Point of Interconnection (with PSTN)
RLR Receiver Loudness Rating
SLR Send Loudness Rating
STMR Sidetone Masking Rating
UPCMI 13-bit Uniform PCM Interface

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1.4 Introduction
Since the transmission quality and the conversational quality of the PLMN will in general be lower than the
quality of the PSTN connection due to coding distortion, delay, etc., only some transmission aspects can
be brought in line with CCITT Recommendations. It is therefore necessary to improve the overall quality
as much as possible by implementing proper routing and network configurations.
It should be recognised that the transmission plan for the pan-European PLMN cannot lead to major
changes in the PSTN. However, it is important to use the improvements in the evolving PSTN (e.g.
digitalization, introduction of echo cancellers) in an effective way.
The transmission requirements are in the first place based on international connections. When the quality
is sufficient for international connections, it can be assumed that the national connections will have the
same or better quality.
In order to obtain a sufficient quality in the connection, it is preferable to have digital connectivity between
the Base Station System (BSS) and the international exchange. The PLMN requirements are based on
this assumption. When this situation cannot be provided, a lower quality must temporarily be accepted.
This Recommendation consists of two parts: one will deal with network configurations, the other with
transmission performance.
The part about network configurations gives information about the reference connections, on which the
transmission plan is based. Furthermore, some guidelines are presented for improvement of the
transmission quality in the evolving (digital) PSTN.
The part about transmission performance gives mainly characteristics of the transmission between MS
acoustic interface (MRP/ERP) and the interface between the PLMN and the PSTN (POI). For transmission
aspects where it is impossible to give overall characteristics, it is in some cases necessary to make
recommendations for individual parts of the equipment.
Unless otherwise stated, all references to CCITT Recommendations are from the Blue Book (1989).
Annex A considers the effects of the type of acoustic interfaces of the MS.
2 Network configurations
2.1 General
The basic configuration for the interworking with the PSTN is shown in figure 1.
2.2 Model of the PLMN
A more detailed model of the PLMN used for the consideration of transmission planning issues for speech
is shown in figure 2. This model represents the main functions required and does not necessarily imply
any particular physical realisation. Routing of calls is given in Recommendation GSM 03.04.
Any acoustic echo control is not specifically shown as it will be provided by analogue processing of digital
processing or a combination of both techniques.
2.3 Interfaces
The main interfaces identified within the GSM Recommendations are shown in figure 1. For the purposes
of this Recommendation, the Air Interface and the Point of Interconnect (POI) are identified along with two
other interfaces, Interface Z and a 13-bit Uniform PCM Interface (UPCMI). These interfaces are needed to
define the PLMN transmission characteristics and the overall system requirements.
The Air Interface is specified by GSM 05 series Recommendations and is required to achieve MS
transportability. Analogue measurements can be made at this point by using the appropriate radio terminal
equipment and speech transcoder. The losses and gains introduced by the test speech transcoder will
need to be specified.
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The POI with the PSTN will generally be at the 2048 kbits/s level at an interface, in accordance with
CCITT Recommendation G.703. At the point, which is considered to have a relative level of O dBr, the
analogue signals will be represented by 8-bit A-law, according to CCITT Recommendation G.711.
Analogue measurements may be made at this point using a standard send and receive side, as defined in
CCITT Recommendations G.714 and G.712.
Interface Z might be used in the case of direct MSC to MSC connections. Interface Z is of the same
nature as the POI.
The UPCMI is introduced for design purposes in order to separate the speech transcoder impairments
from the basic audio impairments of the MS.
2.4 Configurations of Connections
2.4.1 General Configurations of Connections
Figure 3 shows a variety of configurations of connections. There are a number of PSTN features which
should be avoided from such connections. These include:
- echo control devices in the international network. If present, and not disabled, these devices will be
in tandem with PLMN echo cancellers and may introduce degradation;
- satellite routings. The delay inherent in the connections when added to the PLMN delay, may result
in conversational difficulties. Double satellite links are likely to cause severe difficulties and special
precautions should be taken to avoid this situation under call forwarding arrangements;
- digital speech interpolation systems (DSI). There is likely to be an adverse interaction between DSI
and DTX;
- ADPCM. The distortion introduced by ADPCM on routes where PSTN echo control is not provided
is likely to reduce the echo cancellation provided by the PLMN electric echo canceller;
- significant differences in clock rates on non-synchronised digital network components. The resulting
phase roll and slips are likely to degrade the performance of the PLMN echo canceller;
- those analogue FDM routings which exhibit phase roll. Any phase roll due to the absence of
synchronisation between the carrier frequencies on the two directions of transmission is likely to
degrade the performance of the PLMN echo canceller;
- tandem connections of sources of quantisation distortion. The PLMN speech transcoder is
estimated to be equivalent to 7 QDUs between uniform PCM interfaces (see CCITT
Recommendation G.113).
It is recognised that on some connections it may not be feasible to avoid these features, but in many
cases, especially if taken into account at the planning stage, this should be possible.
2.4.2 Reference configurations to illustrate delay and echo control issues
Three basic reference configuration types shown in Figures 4 to 6 are defined to illustrate delay and echo
control issues. Intermediate echo control devices as shown in the figures are disabled by appropriate
signalling between the MSC and ISC or MSC and MSC.
Reference configurations A (see figure 4) represent national or international connections where there is no
echo control device in the PSTN. These reference configurations include re-routing configurations where
the overall delay of the transmission path has not been extended.
Reference configurations B (see figure 5) represent national or international connections where echo
control is provided in the PSTN. These reference configurations include re-routing configurations where
the overall delay of the transmission path has not been extended.
Reference configurations C (see figure 6) represent national or international connections where re-routing
has lead to an increase in the overall delay of the transmission path beyond recommended limits.

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2.5 4-wire circuits in the PLMN
As shown in figure 2, the PLMN will usually contain transmission systems. Where present, they should
provide 4-wire circuits.
In the case of digital circuits which do not include any speech processing devices, the overall system
requirements of the PLMN will not be affected by the presence of the link.
In the case of analogue links, the transmission characteristics (e.g. attenuation, attenuation distortion,
noise) will affect the overall system requirements of the PLMN. CCITT Recommendations M.1020,
M.1025, M.1030 and M.1040 describe several transmission characteristics for leased circuits. In cases
where the analogue link introduces loss, provision will have to be made at the interface to restore the loss.
3 Transmission performance
The overall transmission performance of connections in alternate conversation mode can be considered
as a summation of the effects of:
- the audio part between the MRP/ERP and the UPCMI interface;
- the speech transcoder part including the effects of radio transmission, and speech processing
between the UPCMI and the POI;
- the overall characteristics of the connection between POI and the other user.
There is not only a linear addition of these effects but there is also an influence from different parts of the
connection on the performance of the speech transcoder and other speech processing devices.
Where possible, the transmission performance is specified between the MRP/ERP and the POI. Where
this is not possible, the transmission aspects of the audio part mentioned above have been specified. The
transmission aspects of the speech transcoder are specified in GSM 06 series Recommendations. In the
following paragraphs, requirements are specified for the UPCMI, the Air Interface or the POI as
appropriate.
The following paragraphs are applicable to handset MSs. In some places, reference is made to headset
and hands free MSs, but further study is needed to fully extend this Recommendation to these types of
acoustic interface (see Annex A).
The transmission requirements of the MS have been derived from the requirements of digital telephones
stated in ETS 300 085 (December 1990).
MSs will have to work in a variety of environments ranging from quiet office locations to very noisy
environments as found in moving cars. In noisy conditions, different values for SLR, STMR and low
frequency response may be required. These different values may be achieved by introducing some
switch-over function (manual or automatic). This point needs further study.
The overall transmission performance in full duplex conversation mode will also greatly depend on the
performance of the echo control devices which may be included in the connection.
3.1 Overall Loss/Loundness ratings
The overall international connection involving PLMNs and the PSTN should meet the overall loundness
rating (OLR) limits in CCITT Recommendation G.111. The national parts of the connection should
therefore meet the send and receive loudness rating (SLR, RLR) limits in CCITT Recommendation G.121.
For the case where digital routings are used to connect the PLMN to the international chain of circuits, the
SLR and RLR of the national extension will be largely determined by the SLR and RLR of the PLMN. The
limits given below are consistent with the national extension limits and long term objectives in CCITT
Recommendation G.121.
The SLR and RLR values for the PLMN apply up to the POI. However, the main determining factors are
the characteristics of the MS, including the analogue to digital conversion (ADC) and digital to analogue

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ETS 300 540: January 1996 (GSM 03.50 Version 4.2.0)
conversion (DAC). Hence, in practice, it will be convenient to specify loudness ratings to the Air Interface.
For the normal case, where the PLMN introduces no additional loss between the Air Interface and the
POI, the loudness ratings to the PSTN boundary (POI) will be the same as the loudness ratings measured
at the Air Interface. However, in some cases loss adjustment may be needed for interworking situations in
individual countries.
These values are directly applicable to the case of an MS operating in a conventional non-mobile noise
environment. Studies have shown that under the PLMN noise environment, speech levels are likely to be
higher. Hence, in order to avoid clipping in the speech transcoder, the value of SLR may need to be
increased.
NOTE: Measurement of SLR and RLR using sinusoidal test frequencies may not be
sufficiently accurate because of the adaptive characteristics of the PLMN full-rate
speech transcoder. A possible method is to use the artificial voice described in CCITT
Recommendation P.50 to measure send and receive sensitivities. A method used by
one administration uses the artificial voice to measure the loudness rating according to
the Zwicker algorithm.
3.1.1 Connections with handset MSs
The nominal values of SLR/RLR to the POI shall be:
SLR = 8 +/- 3 dB;
RLR = 2 +/- 3 dB.
Where a user-controlled receiving volume control is provided, the RLR shall meet the selected nominal
value for at least one setting of the control. When the control is set to maximum, the RLR shall not be less
than (louder than) - 13 dB.
With the volume control set to the minimum position the RLR shall not be greater than (quieter than) 18
dB.
Compliance shall be checked by the tests described in Annex B, subclauses B.1.1 and B.1.2.
NOTE: The mechanical design of some MSs may make it impossible to seal the earpiece to
the knife edge of the CCITT artificial ear. Minimal additional methods may be used to
provide the seal provided that they do not affect the mounting position of the MS with
respect to the Mouth Reference Point and the Ear Reference Point.
3.1.2 Connections with handsfree MSs using loudspeakers
The SLR and RLR should be measured and computed using the methods given in CCITT
Recommendation P.34 section 6 with an artificial voice satisfying CCITT Recommendation P.50.
The values of SLR/RLR to/from the POI should be:
SLR = 13 +/- 3 dB (note 1);
RLR = 2 +/- 3 dB with the volume control set to the mid position.
A receive volume control should be provided with a range of between +/- 7.5 dB and +/- 15 dB.
The use of values towards the most sensitive end of the range may result in problems with amplifying
crosstalk from other channels (note 2).
NOTE 1: This values takes into account the CCITT Recommendation P.34; the SLR of a
handsfree telephone should be 5 dB higher than the corresponding value for a handset
instrument. The tolerance of +/- 3 dB is provisional.
NOTE 2: This procedure assumes no automatic gain control in the mobile terminal. The use of
such techniques is not recommended for mobile applications.

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NOTE 3: Further work is required to develop a practical test method using CCITT
Recommendation P.50.
3.1.3 Connections with headset MSs
The SLR and RLR should be measured and computed using methods given in CCITT Recommendation
P.38. This Recommendation currently gives a measuring technique for supra-aural earphone and insert-
type receivers. Study is continuing on other types of earpieces in CCITT SGXII.
The values of SLR/RLR to/from the POI should be:
SLR = 8 +/- 3 dB;
RLR = 2 +/- 3 dB with any volume control set to mid position.
Any receive volume control should have, provisionally, a maximum range of +/- 6 dB.
3.2 Stability Loss
The stability loss presented to the PSTN by the PLMN at the POI should meet the principles of the
requirements in Sections 2 and 3 of CCITT Recommendation G.122. These requirements will be met if
the attenuation between the digital input and digital output at the POI is at least 6 dB at all frequencies in
the range 200 Hz to 4 kHz under the worst-case acoustic conditions at the MS (any acoustic echo control
should be enabled).
For the normal case of digital connection between the Air Interface and the POI, the stability requirement
can be applied at the Air Interface. The worst-case acoustic conditions will be as follows (with any volume
control set to maximum):
Handset MS: the handset lying on, and the transducers facing, a hard surface with the earpiece
uncapped.
Handsfree MS: a representative worst-case position of microphone and loudspeaker (for further
study).
Headset MS: for further study.
NOTE: The test procedure will need to take into account the switching effects of echo control
and DTX.
3.3 Delay
3.3.1 General
A significant propagation time between the two ends of a connection causes difficulties in conversation
over the connection. This arises from two causes. Firstly, the signal is reflected back from the distant end
causing an echo to the talker (this is considered in paragraph 3.4). Secondly, even if ideal echo control
were achieved, the delay between a user talking and receiving a reply from the user at the distant end of
the connection could cause conversational difficulty.
PLMNs will be connected to the PSTN at a point where present planning rules allow for a delay of less
than 12 ms (see CCITT Recommendation G.114 paragraph 2.2a). The delay within the PLMN will greatly
exceed this. If unacceptable circuit delays are not to be experienced by users, action will have to be taken
when planning routes or during call set-up.

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3.3.2 Sources of delay
3.3.2.1 Elements of the PLMN that cause delay
The delay of the PLMN is made up of the following elements:
- speech transcoding delay;
- radio channel coding delay;
- PLMN network delay (i.e. fixed elements such as multiplexing, propagation, switching, echo
control).
3.3.2.2 Elements of the PSTN that cause delay
CCITT recommendation G.114 identifies various elements present in some PSTN connections which
cause delay. These include:
- coaxial, radio and optical fibre terrestrial transmission systems;
- geostationnary satellites;
- digital speech interpolators;
- digital exchanges (see also CCITT recommendation Q.551);
- echo cancellers.
3.3.3 Effects of delay
Some recent studies have suggested that under ideal conditions, i.e.:
- effective control of all echoes without clipping by the use of good echo cancellers;
- low background noise leading to an absence of perceptible noise contrast;
- low distortion of transmitted signals;
- ideal loudness ratings;
users can tolerate a circuit delay well in excess of 400 ms (currently the maximum delay recommended in
CCITT Recommendation G.114). Other studies indicate that the difficulty caused by circuit delay
increases when impairments, such as imperfect echo control caused by echo suppressors, clipping and
noise contrast, are present.
However, the mobile environment is very harsh, with
...