ETSI ETS 300 915 ed.4 (1998-03)

Digital cellular telecommunications system (Phase 2+) (GSM); Terminal Adaptation Functions (TAF) for services using synchronous bearer capabilities (GSM 07.03 version 5.3.1)

RE/SMG-040703QR3

Digitalni celični telekomunikacijski sistem (faza 2+) – Terminalske prilagajalne funkcije (TAF) za storitve, ki uporabljajo sinhrone nosilne zmogljivosti (GSM 07.03, različica 5.3.1)

General Information

• Status: Published
• Publication Date: 06-Apr-1998
• Technical Committee: SMG 4 - Data Services
• Current Stage: 12 - Completion
• Due Date: 20-Apr-1998
• Completion Date: 07-Apr-1998
• Ref Project: SIST ETS 300 915 E4:2003 - Digital cellular telecommunications system (Phase 2+) (GSM); Terminal Adaptation Functions (TAF) for services using synchronous bearer capabilities (GSM 07.03 version 5.3.1)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST ETS 300 915 E4:2003
01-december-2003
'LJLWDOQLFHOLþQLWHOHNRPXQLNDFLMVNLVLVWHPID]D±7HUPLQDOVNHSULODJDMDOQH
IXQNFLMH7$)]DVWRULWYHNLXSRUDEOMDMRVLQKURQHQRVLOQH]PRJOMLYRVWL*60
UD]OLþLFD
Digital cellular telecommunications system (Phase 2+) (GSM); Terminal Adaptation
Functions (TAF) for services using synchronous bearer capabilities (GSM 07.03 version
5.3.1)
Ta slovenski standard je istoveten z: ETS 300 915 Edition 4
ICS:
33.070.50 Globalni sistem za mobilno Global System for Mobile
telekomunikacijo (GSM) Communication (GSM)
SIST ETS 300 915 E4:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST ETS 300 915 E4:2003

---------------------- Page: 2 ----------------------

SIST ETS 300 915 E4:2003
EUROPEAN ETS 300 915
TELECOMMUNICATION March 1998
STANDARD Fourth Edition
Source: SMG Reference: RE/SMG-040703QR3
ICS: 33.020
Key words: Digital cellular telecommunications system, Global System for Mobile communications (GSM)
R
GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
Digital cellular telecommunications system (Phase 2+);
Terminal Adaptation Functions (TAF)
for services using synchronous bearer capabilities
(GSM 07.03 version 5.3.1)
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
Internet: [e-mail] - http://www.etsi.fr - http://www.etsi.org
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 1998. All rights reserved.

---------------------- Page: 3 ----------------------

SIST ETS 300 915 E4:2003
Page 2
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
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.

---------------------- Page: 4 ----------------------

SIST ETS 300 915 E4:2003
Page 3
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
Contents
Foreword .5
1 Scope .7
2 Normative references.7
2.1 Abbreviations .9
3 General.9
3.1 Customer access configuration .9
3.2 Terminal Adaptation Function.9
3.3 TAF Interfacing to other MT functions .10
4 Terminal Adaptation Functions for synchronous transparent services .10
4.1 Rate Adaptation .10
4.1.1 Rate adaptation - V-series.11
4.1.2 Rate adaptation - X.21 .11
4.1.3 Rate adaptation - S-interface .11
4.2 Interchange Circuit Signalling Mapping .13
4.2.1 V-series interchange circuit mapping .13
4.2.1.1 Multislot configurations (Channel coding TCH/F9.6 or
TCH/F4.8 kbit/s) .15
4.2.1.2 Channel coding TCH/F14.4 .15
4.2.2 X.21 Interchange circuit mapping.15
4.2.3 Case of S-interface.16
4.3 Call establishment signalling mapping at TE/MT interface.17
4.3.1 V-series interfaces.17
4.3.1.1 Call establishment manual operation - utilizing Alternate
Speech/Data or Speech followed by Data Capabilities .17
4.3.1.2 Call establishment manual operation - utilizing the
Unrestricted Digital Capability.17
4.3.1.3 V.25 bis auto call/auto answer.17
4.3.2 X-series interfaces .18
4.3.2.1 X.21 bis call establishment manual operation - utilizing
the Unrestricted Digital Capability.18
4.3.2.2 X.21 bis/V.25 bis call establishment signalling mapping .18
4.3.2.3 X.21 call establishment signalling mapping.18
4.3.3 S-interface (I.420) signalling mapping.18
4.3.4 X.25 procedures mapping .19
5 Terminal Adaptation Functions for synchronous non-transparent services .19
5.1 Rate Adaptation and protocol model.19
5.1.1 R-interface.19
5.1.2 S-interface.19
5.2 Signalling Mapping.19
5.2.1 Interchange circuit signalling mapping .19
5.2.2 Call establishment signalling mapping .19
5.3 Flow Control.19
5.3.1 Conditions requiring flow control towards the network.19
5.3.2 Conditional requiring flow control towards TE2 .20
5.3.3 Local flow control.20
5.4 Buffers .20
5.4.1 TX buffers.20
5.4.2 RX buffers .20
6 V- and S-series interface procedures to 04.08 mapping.21
6.1 Mobile Originated calls.21
6.2 Mobile Terminated calls.22

---------------------- Page: 5 ----------------------

SIST ETS 300 915 E4:2003
Page 4
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
7 X.21 interface procedures to 04.08 mapping. 22
7.1 X.21 procedures mapping. 22
7.1.1 Mobile originated call (see figure 10). 22
7.1.2 Mobile terminated call (see figure 10). 23
7.1.3 Mobile termination clearing (see figure 11). 23
7.1.4 Distant end terminal clearing . 23
7.1.5 Network generated clearing (see figure 11) . 23
7.2 Dm Signalling causes mapping to X.21 call progress signals. 25
7.3. X.21 FACILITIES MAPPING . 25
8 Support for packet service. 27
8.1 Terminal configurations. 27
8.2 Support for basic packet access . 28
8.3 Support for dedicated packet access. 29
Annex A (normative): L2R Functionality . 30
A.1 Introduction. 30
A.2 L2RBOP. 30
A.3 Use of the L2RBOP . 32
A.3.1 Radio Link Connection Control. 32
A.3.2 Status transfer. 33
A.3.3 LAPB connection control. 33
A.3.4 LAPB exchange identification. 33
A.3.5 Data Transfer . 33
A.3.6 Flow control. 33
History. 34

---------------------- Page: 6 ----------------------

SIST ETS 300 915 E4:2003
Page 5
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
Foreword
This fourth edition European Telecommunications Standard (ETS) has been produced by the Special
Mobile Group (SMG) of the European Telecommunications Standards Institute (ETSI).
This ETS defines the interfaces and Terminal Adaptation Functions (TAF) integral to a Mobile Termination
(MT) which enables the attachment of synchronous terminals to a MT within the digital cellular
telecommunications system (Phase 2+).
The contents of this ETS is subject to continuing work within SMG and may change following formal SMG
approval. Should SMG modify the contents of this ETS, it will be resubmitted for OAP by ETSI with an
identifying change of release date and an increase in version number as follows:
Version 5.x.y
where:
y the third digit is incremented when editorial only changes have been incorporated in the
specification;
x the second digit is incremented for all other types of changes, i.e. technical enhancements,
corrections, updates, etc.
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 drafting rules.
Transposition dates
Date of adoption of this ETS: 3 April 1998
Date of latest announcement of this ETS (doa): 30 June 1998
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 December 1998
Date of withdrawal of any conflicting National Standard (dow): 31 December 1998

---------------------- Page: 7 ----------------------

SIST ETS 300 915 E4:2003
Page 6
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
Blank page

---------------------- Page: 8 ----------------------

SIST ETS 300 915 E4:2003
Page 7
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
1 Scope
This European Telecommunications Standard (ETS) defines Terminal Adaptation Functions (TAF) which
are integrated in a Mobile Termination (MT) and which enable the attachment of Synchronous Terminals
to an MT (see GSM 04.02 [4]). The general aspects of Terminal Adaptation Functions are contained in
specification GSM 07.01 (ETS 300 913) [8]. This ETS covers support of synchronous data services (see
GSM 02.02 (ETS 300 904)[2]) for the following interfaces and procedures:
- V.22 DTE/DCE Interface
- V.22 bis DTE/DCE Interface
- V.26 ter DTE/DCE Interface
- V.32 DTE/DCE Interface
- X.21 DTE/DCE Interface
- X.21 bis DTE/DCE Interface
- X.25 Procedure
- X.32 Procedure
- V.25 bis Procedure
- I.420 Interface (S)
LAPB is the only synchronous non-transparent protocol which is considered here.
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 350): "Digital cellular telecommunication system (Phase 2+);
Abbreviations and acronyms".
[2] GSM 02.02 (ETS 300 904): "Digital cellular telecommunication system
(Phase 2+); Bearer Services (BS) supported by a GSM Public Land Mobile
Network (PLMN)".
[3] GSM 03.10: "Digital cellular telecommunication system (Phase 2+); GSM Public
Land Mobile Network (PLMN) connection types".
[4] GSM 04.02: "Digital cellular telecommunication system (Phase 2+); GSM Public
Land Mobile Network (PLMN) access reference configuration".
[5] GSM 04.08 (ETS 300 940): "Digital cellular telecommunication system
(Phase 2+); Mobile radio interface layer 3 specification".
[6] GSM 04.21 (ETS 300 945): "Digital cellular telecommunication system; Rate
adaption on the Mobile Station - Base Station System (MS - BSS) interface".
[7] GSM 04.22 (ETS 300 946): "Digital cellular telecommunication system
(Phase 2+); Radio Link Protocol (RLP) for data and telematic services on the
Mobile Station - Base Station System (MS - BSS) interface and the Base Station
System - Mobile-services Switching Centre (BSS - MSC) interface".
[8] GSM 07.01 (ETS 300 913): "Digital cellular telecommunication system
(Phase 2+); General on Terminal Adaptation Functions (TAF) for Mobile
Stations (MS)".
[9] GSM 08.20 : "Digital cellular telecommunication system; Rate adaption on the
Base Station System - Mobile-services Switching Centre (BSS - MSC)
interface".

---------------------- Page: 9 ----------------------

SIST ETS 300 915 E4:2003
Page 8
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
[10] GSM 09.06 (ETS 300 975): "Digital cellular telecommunication system
(Phase 2+); Interworking between a Public Land Mobile Network (PLMN) and a
Packet Switched Public Data Network/Integrated Services Digital Network
(PSPDN/ISDN) for the support of packet switched data transmission services".
[11] GSM 09.07 (ETS 300 976): "Digital cellular telecommunication system
(Phase 2+); General requirements on interworking between the Public Land
Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or
Public Switched Telephone Network (PSTN)".
[12] CCITT Series V Recommendations: "Data communication over the Telephone
network".
[13] CCITT Series X Recommendations: "Data communication networks".
[14] CCITT Recommendation V.10: "Electrical characteristics for unbalanced
double-current interchange circuits for general use with integrated circuit
equipment in the field of data communications".
[15] CCITT Recommendation V.11: "Electrical characteristics for balanced
double-current interchange circuits for general use with integrated circuit
equipment in the field of data communications".
[16] CCITT Recommendation V.25: "Automatic answering equipment and/or parallel
automatic calling equipment on the general switched telephone network
including procedures for disabling of echo control devices for both manually and
automatically established calls".
[17] CCITT Recommendation V.25 bis: "Automatic Calling and/or Answering
Equipment on the General Switched Telephone Network (GSTN) using the
100-series interchange circuits".
[18] CCITT Recommendation V.28: "Electrical characteristics for unbalanced
double-current interchange circuits".
[19] CCITT Recommendation V.110: "Support of data terminal equipments (DTEs)
with V-Series interfaces by an integrated services digital network".
[20] CCITT Recommendation V.24: "List of definitions for interchange circuits
between data terminal equipment (DTE) and data circuit-terminating
equipment".
[21] CCITT Recommendation X.24: "List of definitions for interchange circuits
between Data Terminal Equipment (DTE) and Data Circuit Terminating
Equipment (DCE) on Public Data Networks".
[22] CCITT Recommendation X.25: "Interface between Data Terminal Equipment
(DTE) and Data Circuit Terminating Equipment (DCE) for terminals operating in
Packet Mode and connected to Public Data Networks by dedicated Circuit".
[23] CCITT Recommendation X.21: "Interface between Data Terminal Equipment
(DTE) and Data Circuit Terminating Equipment (DCE) for synchronous
operation in public data networks".
[24] CCITT Recommendation X.21 bis: "Use on public data networks of data
terminal equipment (DTE) which is designed for interfacing to synchronous
V-Series modems".
[25] CCITT Recommendation X.26: "Electrical characteristics for unbalanced
double-current interchange circuits for general use with integrated circuit
equipment in the field of data communications".

---------------------- Page: 10 ----------------------

SIST ETS 300 915 E4:2003
Page 9
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
[26] CCITT Recommendation X.27: "Electrical characteristics for balanced
double-current interchange circuits for general use with integrated circuit
equipment in the field of data communications".
[27] CCITT Recommendation X.30: "Support of X.21, X.21 bis and X.20 bis based
Data Terminal Equipment (DTEs) by an ISDN".
[28] CCITT Recommendation X.31: "Support of Packet Mode Terminal Equipment in
ISDN".
[29] CCITT Recommendation X.32: "Interface between Data Terminal Equipment
(DTE) and Data Circuit Terminating Equipment (DCE) for terminals operating in
Packet Mode and accessing a PSPDN through a PSTN or an ISDN or a
CSPDN".
[30] CCITT Recommendation I.461: "Support of X.21, X.21 bis and X.20 bis based
data terminal equipment (DTEs) by integrated services digital network (ISDN)".
[31] CCITT Recommendation I.463: "Support of data terminal equipment (DTEs)
with V-Series type interfaces by an integrated services digital network (ISDN)".
[32] ISO Recommendation 8885: "Information technology - Telecommunication and
information exchange between systems - High-level data link control (HDLC)
procedures - General purpose XID frame information field content and format".
[33] ISO Recommendation 8886: "Information technology - Telecommunication and
information exchange between systems - Data link service definitions for Open
Systems interconnection".
[34] Personal Computer Memory Card Association: "PCMCIA 2.1 or PC-Card 3.0
electrical specification or later revisions".
[35] Infrared Data Association IrDA "IrPHY Physical layer signalling standard".
[36] TIA-617: "Data Transmission Systems and Equipment - In-Band DCE Control".
[37] GSM 02.34: “Digital cellular telecommunications system (Phase 2+); High
Speed Circuit Switched Data (HSCSD) - Stage 1”
[38] GSM 03.34 (TS 101 038): “Digital cellular telecommunications system
(Phase 2+); High Speed Circuit Switched Data (HSCSD) -Stage 2 Service
Description”
2.1 Abbreviations
In addition to those below abbreviations used in this ETS are listed in GSM 01.04 (ETR 350) [1].
AU Access Unit
PF Packet Function
3 General
3.1 Customer access configuration
The GSM PLMN access reference configuration is described in figure 1 of GSM 04.02 [4]. This
specification (GSM 07.03) specifically refers to the MTs which support terminal equipments (TE1 or TE2)
that use synchronous bearer capabilities.
3.2 Terminal Adaptation Function
The TAF is functionally part of an MT0, MT1 or MT2 (see GSM 04.02 [4]). The terminal adaptation
provides facilities to allow manual or automatic call control functions associated with alternate

---------------------- Page: 11 ----------------------

SIST ETS 300 915 E4:2003
Page 10
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
speech/data, speech followed by data and circuit switched data services, in case of V series interfaces.
The X.21 DTE/DCE interface allows only for automatic call control functions. The following functions are
included:
- Conversion of electrical, mechanical, functional and procedural characteristics of the V-series,
X-series and ISDN type interfaces to those required by a GSM PLMN.
- Bit rate adaptation of V-series and X-series data signalling rates and the ISDN 64 kbit/s to that
provided in the GSM PLMN.
- The mapping of V.25 bis AUTO CALL/AUTO ANSWER procedures and X.21 procedures to the
GSM PLMN Dm-channel signalling.
- The mapping functions necessary to convert S-interface signalling to PLMN Dm-channel signalling.
- Synchronization procedure, which means the task of synchronizing the entry to and the exit from
the data transfer phase between two subscriber terminals. This is described in the specification
GSM 07.01 (ETS 300 913) [8].
- Filtering of channel control information. This is described in the specification GSM 07.01
(ETS 300 913) [8].
- Compatibility checking (see GSM 07.01 (ETS 300 913) [8])
- Layer 2 relaying (see annex 1)
- Flow control
- In Call Modification function (see section 4)
- Splitting and combining of the data flow in case of multislot data configurations
3.3 TAF Interfacing to other MT functions
TAF interfacing is shown in figure 1.
Mobility Management
TAF RR Management
Channel Codec    FEC
Call Control
MMI
Figure 1: TAF interfacing to other MT functions
4 Terminal Adaptation Functions for synchronous transparent services
Specification GSM 03.10 [3] refers to the models for connection types supporting synchronous transparent
services.
4.1 Rate Adaptation
Rate adaptation on the MS-BS interface is described in GSM 04.21. The synchronous data services make
use of the following rate adaptation functions: RA1, RA2, RA1/RA1' and RA1'. See also Figure 6 in GSM
03.10. The D-bits of the rate adaptation frames are used to convey user data and the S- and X-bits are
used to convey channel status information associated with the data bits in the data transfer state, or to
carry substream numbering between the Split/Combine functions in case of multislot operation. For the S-
and X-bits, a ZERO corresponds to the ON condition, a ONE to the OFF condition.

---------------------- Page: 12 ----------------------

SIST ETS 300 915 E4:2003
Page 11
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
4.1.1 Rate adaptation - V-series
This is provided as indicated in specification GSM 04.21 (ETS 300 945) [6]. The functions applied in this
case are shown in figure 2 (see model 2b in figure 6 of GSM 03.10 [3]).
Interface circuits
MT2
(data and control)
TE2
V-series
RA1'
R
Figure 2: Rate adaptation for V-series terminals
4.1.2 Rate adaptation - X.21
This is provided as indicated in specification GSM 04.21 (ETS 300 945) [6]. The functions applied in this
case are shown in figure 3 (see model 2b in figure 6 of GSM 03.10 [3]).
Interface circuits
T and R for data
MT2
V and I for control
TE2
X-series RA1'
R
Figure 3: Rate adaptation for X.21 terminals
4.1.3 Rate adaptation - S-interface
The functions applied in this case are shown in figure 4 (see model 2a in figure 6 of GSM 03.10 [3]).
TA MT1
TE2
RA1 RA2 RA1 RA1'
RA2
RS
Figure 4a: Rate adaptation for S-interface
TE1 MT1
RA1 RA2 RA1 RA1'
RA1
S
Figure 4b: Rate adaptation for S-interface (continued)
There are two cases to be considered for the RA1 function:
a) V-series interface
For the V-series type of terminal equipments the rate adaptation functions are as described in
GSM 04.21 (ETS 300 945) [6].
b) X.21-interface
For terminal equipments using the X.21-interface the rate adaptation functions are identical to those
described in GSM 04.21 (ETS 300 945) [6], but the notation used is as described in CCITT
recommendation X.30/I.461.
The notation used is as follows:
The conversion of the user rates of 2.4 and 4.8 kbit/s to 8 kbit/s and user rate of 9.6 kbit/s to
16 kbit/s shall be implemented by means of the 40 bit frame structure shown in figure 5.

---------------------- Page: 13 ----------------------

SIST ETS 300 915 E4:2003
Page 12
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
Figure 5 shows that in addition to the basic frame, a two frame multiframe is employed. In odd
frames, octet 0 contains all zeros, whilst in even frames octet 0 consists of a one followed by seven
E bits. The order of bit transmission of the 40 bit frame is from left-to-right and top-to-bottom.
This two frame multiframe corresponds to the 80 bit frame structure presented in GSM 04.21
(ETS 300 945) [6] as shown in figure 6. The 24 information bits P1,.,P8, Q1,.Q8, R1,.,R8 of odd
frames correspond with D1,.,D24 and those of even frames correspond with D25,.,D48
respectively. For the status bits there is the following correspondence: odd frame
SQ,X,SR,SP = S1,X,S3,S4 and even frame SQ,X,SR,SP = S6,X,S8,S9.
Option for a manufacturer of mobile stations:
In transparent mode support of a packet mode TE1 or TE2/TA, which uses flag stuffing.
Bit number
12 34 56 78
Octet 0 Odd frames 0 0 0 0 0 0 0 0
Even frames 1 E1 E2 E3 E4 E5 E6 E7
Octet 1 1 P1 P2 P3 P4 P5 P6 SQ
Octet 2 1 P7 P8 Q1 Q2 Q3 Q4 X
Octet 3 1 Q5 Q6 Q7 Q8 R1 R2 SR
Octet 4 1 R3 R4 R5 R6 R7 R8 SP
NOTE: Bit X, if not used for the optional flow control or for the indication of the far end
synchronization, shall be set to 0 (see CCITT Recommendation I.463/V.110).
Figure 5: 40 bit frame structure of CCITT X.30
X.30 Two frame multifr. V.110 80-bit frame

00000000 00000000
odd 1 P1P2P3P4P5P6SQ 1 D1 D2 D3 D4 D5 D6 S1
frame 1 P7 P8 Q1 Q2 Q3 Q4 X 1 D7 D8 D9 D10 D11 D12 X
1 Q5Q6Q7Q8R1 R2 SR 1 D13 D14 D15 D16 D17 D18 S3
1 R3R4R5R6R7R8SP 1 D19 D20 D21 D22 D23 D24 S4

1 E1 E2 E3 E4 E5 E6 E7 1 E1 E2 E3 E4 E5 E6 E7
even 1 P1 P2 P3 P4 P5 P6 SQ 1 D25 D26 D27 D28 D29 D30 S6
frame 1 P7 P8 Q1 Q2 Q3 Q4 X 1 D31 D32 D33 D34 D35 D36 X
1 Q5Q6Q7Q8R1 R2 SR 1 D37 D38 D39 D40 D41 D42 S8
1 R3R4R5R6R7R8SP 1 D43 D44 D45 D46 D47 D48 S9
Figure 6: Correspondence of X.30 and V.110 frames

---------------------- Page: 14 ----------------------

SIST ETS 300 915 E4:2003
Page 13
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
4.2 Interchange Circuit Signalling Mapping
4.2.1 V-series interchange circuit mapping
The interchange circuit signalling mapping at the interface between the TE2 and the MT shall conform to
CCITT recommendation V.24; while the signal levels at the interface shall conform either to CCITT
recommendation V.28, or to IrDA IrPHY Physical signalling standard specification, or to PCMCIA 2.1, or to
PC-Card 3.0 electrical specifications or to later revisions.
The signals required at this interface are shown in table 2.
Specification 04.21 refers to the frame structure and identifies the use of status bits for the carriage
of signalling information.
Status bits
The bits S and X are used to convey channel status information associated with the data bits in the data
transfer stage as shown below. The S-bits are put into two groups SA and SB to carry the condition of two
interchange circuits. The X-bit is used to control the condition of circuit 106.
The mechanism for proper assignment of the control information from the transmitting signal rate adapter
interface via these bits to the receiving signal rate adapter interface is shown below in table 1.
For the S and X bits, a ZERO corresponds to the ON condition, a ONE to the OFF condition.
General mapping scheme
Table 1: General mapping scheme for V-series interchange circuits
108
S1, S3, S6, S8 = SA 107
105
S4, S9 = SB
109
Frame synch
X
and 106/IWF 106
TE IWF
IWF TE

---------------------- Page: 15 ----------------------

SIST ETS 300 915 E4:2003
Page 14
ETS 300 915 (GSM 07.03 version 5.3.1): March 1998
Table 2: Minimum set of V-series interchange circuits
Circuit Number Circuit Name Ground Data Control
to from to from
TE2 TE2 TE2 TE2
CT102 Common Return X
CT103 Transmitted
data X
CT104 Received data X
CT105 Request to
send X
CT106 Ready for
se
...