ETSI TS 123 053 V9.0.0 (2010-01)

Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); Tandem Free Operation (TFO); Service description; Stage 2 (3GPP TS 23.053 version 9.0.0 Release 9)

RTS/TSGS-0423053v900

General Information

• Status: Published
• Publication Date: 24-Jan-2010
• Technical Committee: 3GPP SA 4 - Codec
• Current Stage: 12 - Completion
• Due Date: 05-Jan-2010
• Completion Date: 25-Jan-2010

Standards Content (Sample)

ETSI TS 123 053 V9.0.0 (2010-01)
Technical Specification

Digital cellular telecommunications system (Phase 2+);
Universal Mobile Telecommunications System (UMTS);
Tandem Free Operation (TFO);
Service description;
Stage 2
(3GPP TS 23.053 version 9.0.0 Release 9)



R
GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS

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3GPP TS 23.053 version 9.0.0 Release 9 1 ETSI TS 123 053 V9.0.0 (2010-01)



Reference
RTS/TSGS-0423053v900
Keywords
GSM, UMTS
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© European Telecommunications Standards Institute 2010.
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ETSI

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3GPP TS 23.053 version 9.0.0 Release 9 2 ETSI TS 123 053 V9.0.0 (2010-01)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://webapp.etsi.org/IPR/home.asp).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
http://webapp.etsi.org/key/queryform.asp.
ETSI

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3GPP TS 23.053 version 9.0.0 Release 9 3 ETSI TS 123 053 V9.0.0 (2010-01)
Contents
Intellectual Property Rights . 2
Foreword . 2
Foreword . 4
1 Scope . 5
2 References . 5
3 Definitions and abbreviations . 6
3.1 Definitions . 6
3.2 Abbreviations . 6
4 Main Concepts . 6
5 TFO Architecture and Transmission Mechanism . 6
5.1 TFO Access Interfaces and Reference Points . 6
5.2 General In-band Transmission Mechanism for TFO . 7
5.3 High-Level Functions Required for TFO . 7
6 Model of operation . 8
6.1 Overview . 8
6.2 TFO establishment phase . 8
6.2.1 Sending of TFO_REQ message by a BSS . 8
6.2.2 Monitoring of TFO_REQ by a BSS . 9
6.3 Transparency of transmission equipments . 9
6.3.1 Local disabling . 9
6.3.2 Transparency to TFO negotiation messages . 9
6.3.3 Transparency to TFO speech frames . 9
6.4 Modification of speech codec . 10
6.4.1 Introduction. 10
6.4.2 Exchanged parameters . 10
6.4.3 Change of speech codec configuration in the BSS . 10
6.5 TFO operation . 10
6.5.1 End to end delay . 10
6.5.2 Synchronisation between TRAUs . 10
6.5.3 Monitoring in TFO operation. 11
6.5.4 DTX aspects. 11
6.5.5 Error concealment . 11
6.5.6 Management of UFE bit . 11
6.5.7 Handover management . 11
6.5.8 Other issues . 12
7 Compatibility Issues . 12
8 Interactions with Other Services . 12
8.1 General . 12
8.2 Support of DTMF . 13
9 Operational Aspects . 13
Annex A (informative): Change history . 14
History . 15

ETSI

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3GPP TS 23.053 version 9.0.0 Release 9 4 ETSI TS 123 053 V9.0.0 (2010-01)
Foreword
rd
This Technical Specification has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
ETSI

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3GPP TS 23.053 version 9.0.0 Release 9 5 ETSI TS 123 053 V9.0.0 (2010-01)
1 Scope
The present document defines the stage 2 service description for Tandem Free Operation (TFO) in and between GSM
and UMTS. Tandem Free Operation applies only to speech calls.
NOTE: The TFO principles are built so that they could be used as well by other systems other than GSM and
UMTS.
In analogy with ITU-T Recommendations I.130 [2] and with reference to ITU-T Recommendations Q.65 VI.1 (Stage 2
of the method for the characterisation of services supported by an ISDN), the second stage of the following three-level
structure is derived from a stage 1 service description.
- Stage 1 is an overall service description, from the service subscriber's and user's standpoints, that views the
network as a single entity which provides services to the user.
- Stage 2 identifies the functional capabilities and information flows needed to support the service described in
stage 1. Furthermore, it identifies various possible physical locations for the functional capabilities. The output
of Stage 2, which is signalling system independent, is used as an input to Stage 3, the design of signalling system
and switching Recommendations.
- Stage 3 defines the signalling system protocols and switching functions needed to implement the service
described in stage 2.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 01.04: "Digital cellular telecommunications system (Phase 2+); Abbreviations and
acronyms".
[2] ITU-T Recommendations I.130 (1988): "Method for the characterization of telecommunication
services supported by an ISDN and network capabilities of an ISDN".
[3] 3GPP TS 22.053: "Tandem Free Operation (TFO); Service Description - Stage 1".
[4] 3GPP TS 48.060: "Digital cellular telecommunications system (Phase 2+); In-band control of
remote transcoders and rate adaptors for full rate traffic channels".
[5] 3GPP TS 48.061: "Digital cellular telecommunications system (Phase 2+); In-band control of
remote transcoders and rate adaptors for half rate traffic channels".
ETSI

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3GPP TS 23.053 version 9.0.0 Release 9 6 ETSI TS 123 053 V9.0.0 (2010-01)
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
Tandem Free Operation: corresponds to the Mobile-to-Mobile calls for which the speech is not transcoded two times
but only one by the Mobile Stations
For simplicity the term MS is also used when UE is meant for 3G systems. The same is valid for TRAU and TC
analogously.
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
IPE: In Path Equipment
TFO: Tandem Free Operation
Further abbreviations used may be found in 3GPP TR 01.04 [1].
4 Main Concepts
In-band TFO aims to remove the speech coding and decoding done in the BSS in MS-to-MS calls in order to improve
the perceived speech quality. In-band TFO is established after call set-up using in-band signalling. This signalling is
therefore controlled by the TRAU.
Using in-band signalling implies that the link between the TRAUs is transparent in the sense that the digital content of
what is emitted by a TRAU is not modified. The so-called In Path Equipments must therefore be disabled or configured
in such a way that the information (signalling and coded speech) required for Tandem Free is not altered.
5 TFO Architecture and Transmission Mechanism
5.1 TFO Access Interfaces and Reference Points
The GSM BSS reference points for TFO are described in figure 1. GSM A interface reference point applies here with
the exception that speech is not in the standard 64 kbit/s PCM format and between TFO TRAUs in-band signalling is
used. For speech and in-band signalling the MSC is transparent.
The UMTS core network reference points for TFO are described in figure 2. The UMTS Nb interface reference point
applies here with the exception that speech is not in the standard 64 kbit/s PCM format and between TFO TRAUs in-
band signalling is used. For speech and in-band signalling the Core Network is transparent.
Additional transmission equipments are taken into account. These equipments are all those which can process the PCM
signal between the two peer BSS, e.g. echo cancellers, DCME. The BSS to BSS transmission is then considered
transparent provided no transmission equipment along the circuit do not modify the 1 or more LSB or these
transmission equipments implement a TFO "transparency mode". A specific signalling allows to remotely control in-
band these equipments.
BSS-MSC out-of-band signalling consists in this version of TFO of the normal BSSMAP signalling which carries the
list of acceptable speech codec that may be used for the TFO negotiation mechanism.
Use of TFO specific out-of-band mechanism is not foreseen in that version of the specification.
ETSI

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3GPP TS 23.053 version 9.0.0 Release 9 7 ETSI TS 123 053 V9.0.0 (2010-01)
Abis A A Abis
BTS BSC MSC MSC BSC BTS
IPE IPE
MS
MS TRAU
TRAU
64 kbit/s Speech Samples carrying
- TFO Frames on the LSB containing
- Compressed speech samples
- Control bits
- TFO Messages
- Original PCM speech samples on the MSB

Figure 1
Iu Nb Nb Iu
MSMSCC S Seerrvveerr
MSCMSC Serv Serverer
RNRNCC NNode Bode B
Node BNode B RRNNCC
IPEIPEIPE IPEIPEIPE
UEUE
UEUE
TCTC
TCTC
MGMGww
MGMGww
64 kbit/64 kbit/ss Spe Speeechch Sam Sampples cles caarryingrrying
-- TFOTFO Fram Frameses o onn th the Le LSSB B cocontntainainiingng
-- CComomprespresssed speeed speech ch ssaammpplesles
-- CControl bontrol biittss
-- TFO MTFO Meessssagesages
-- OOrigiriginanal PCMl PCM spee speech ch samplsamplees on ts on the Mhe MSSBB

Figure 2
5.2 General In-band Transmission Mechanism for TFO
In TFO establishment mode, one bit out of 16 LSB bits is regularly stolen of the 64 kbits/s circuit. This provides for a
0,5 kbits/s channel and has been selected so that the degradation on the speech quality is inaudible.
In TFO established mode bit stealing takes place on the LSB bit/s (bit 8, 7. 9-N; N>=1: number of stolen LSB bits) on
each PCM sample. The number N of stolen LSB bit/s depends on the codec type. This provides for a N*8 kbits/s
channel that allows to carry vocoded speech in TFO frames. The contents of the "unstolen" bits 1- (8-N) is normal
A/μ-law information.
5.3 High-Level Functions Required for TFO
The high level functions which apply to TFO are described hereafter. Not all these functions need necessarily to be
covered by the first description of TFO since some issues may be too complex to solve in an initial stage or at all.
ETSI

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