ETSI EN 300 931 V6.0.1 (1999-09)

Digital cellular telecommunications system (Phase 2+) (GSM); Technical realization of facsimile group 3 transparent (GSM 03.45 version 6.0.1 Release 1997)

DEN/SMG-040345Q6

Digitalni celični telekomunikacijski sistem (faza 2+) – Tehnična realizacija faksimilne skupine 3 transparent (GSM 03.45, različica 6.0.1, izdaja 1997)

General Information

• Status: Published
• Publication Date: 31-Aug-1999
• Technical Committee: SMG 4 - Data Services
• Current Stage: 12 - Completion
• Due Date: 03-Sep-1999
• Completion Date: 01-Sep-1999
• Ref Project: SIST EN 300 931 V6.0.1:2003 - Digital cellular telecommunications system (Phase 2+) (GSM); Technical realization of facsimile group 3 transparent (GSM 03.45 version 6.0.1 Release 1997)

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.UHDOL]DFLMDDigital cellular telecommunications system (Phase 2+) (GSM); Technical realization of facsimile group 3 transparent (GSM 03.45 version 6.0.1 Release 1997)33.070.50Globalni sistem za mobilno telekomunikacijo (GSM)Global System for Mobile Communication (GSM)ICS:Ta slovenski standard je istoveten z:EN 300 931 Version 6.0.1SIST EN 300 931 V6.0.1:2003en01-december-2003SIST EN 300 931 V6.0.1:2003SLOVENSKI
STANDARD
EN 300 931 V6.0.1 (1999-09)European Standard (Telecommunications series)Digital cellular telecommunications system (Phase 2+);Technical realization of facsimile group 3 transparent(GSM 03.45 version 6.0.1 Release 1997)GLOBAL SYSTEM
FOR MOBILE COMMUNICATIONSRSIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)2(GSM 03.45 version 6.0.1 Release 1997)ReferenceDEN/SMG-040345Q6 (8mc0300o.PDF)KeywordsDigital cellular telecommunications system,Global System for Mobile communications (GSM)ETSIPostal addressF-06921 Sophia Antipolis Cedex - FRANCEOffice address650 Route des Lucioles - Sophia AntipolisValbonne - FRANCETel.: [phone]
Fax: [phone]Siret N° 348 623 562 00017 - NAF 742 CAssociation à but non lucratif enregistrée à laSous-Préfecture de Grasse (06) N° 7803/[e-mail] copies of this ETSI deliverablecan be downloaded fromhttp://www.etsi.orgIf you find errors in the present document, send yourcomment to: [e-mail] NotificationNo 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 1999.All rights reserved.SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)3(GSM 03.45 version 6.0.1 Release 1997)ContentsIntellectual Property Rights.5Foreword.50 Scope.60.1References.60.2Definitions and abbreviations.71Service definition.82Network architecture.83Reference configuration at the mobile station.93.1Fax Adaptor functionality.103.2GSM Facsimile Machine functionality.104Connection types.114.1Information transfer protocol model.124.2Interactions with T.30.134.2.1Link control strategy.134.2.1.1Message detection.144.2.2Speed conversion for BCS phases.144.2.3Compatibility checking.154.2.3.1Group 1 and Group 2 support.154.2.3.22 400 bit/s handshaking.154.2.3.3Non-standard facilities.154.2.3.412 000 and 7200 bit/s Facsimile Document Transfer.154.2.3.5Procedure interrupts.154.2.4Speed checking.154.3Radio Channel Modification Procedures.164.3.1In Call Modification (ICM).164.3.2Channel Mode Modify (CMM).175Use of terminal adaptation functions.185.1Standard TAFs for synchronous services.185.2Specific TAFs for facsimile service.185.2.1Working principle.185.2.2Basic protocol structure.195.2.2.1Frame formats.195.2.3Protocol description.205.2.3.1IDLE state.205.2.3.2BCS-REC state.205.2.3.3BCS-TRA state.205.2.3.4MSG-REC state.215.2.3.5MSG-TRA state.215.2.4DCS and TCF processing.215.2.5DCN (disconnect) frame.225.2.6Clocking.225.2.7Timeouts.225.3Specific TAFs for facsimile service (T.30/A).235.3.1Frame detection.235.3.2Message phase.235.3.3Additional CMM request.236Signalling aspects.236.1Handling of Tonal Signals.246.2Call establishment.246.2.1Mobile Terminated Call - Speech then Fax.246.2.2Mobile Terminated Call - Auto answer.246.2.3Mobile Originated Call - Speech then Fax.25SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)4(GSM 03.45 version 6.0.1 Release 1997)6.2.4Mobile Originated Call - Auto calling.256.2.5Mobile Originated Call - Manual calling.256.3Call release.267Interworking to fixed networks.267.1Interworking to PSTN.267.2Interworking to ISDN.27Annex I (informative):Protocol entities from CCITT T.30 and T.4.28Annex II (informative):Procedure examples.29Annex III (informative):Change Request History.42History.43SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)5(GSM 03.45 version 6.0.1 Release 1997)Intellectual Property RightsIPRs essential or potentially essential to the present document may have been declared to ETSI. The informationpertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be foundin SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respectof ETSI standards", which is available free of charge from the ETSI Secretariat. Latest updates are available on theETSI Web server (http://www.etsi.org/ipr).Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guaranteecan be given as to the existence of other IPRs not referenced in SR 000 314 (or the updates on the ETSI Web server)which are, or may be, or may become, essential to the present document.ForewordThis European Standard (Telecommunications series) has been produced by the Special Mobile Group (SMG).The present document defines the technical realization of facsimile group 3 using transparent network support within thedigital cellular telecommunications system.The contents of the present document is subject to continuing work within SMG and may change following formal SMGapproval. Should SMG modify the contents of the present document it will be re-released with an identifying change ofrelease date and an increase in version number as follows:Version 6.x.ywhere:6indicates Release 1997 of GSM Phase 2+xthe second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates,etc.ythe third digit is incremented when editorial only changes have been incorporated in the specification.The specification from which the present document has been derived was originally based on CEPT documentation,hence the presentation of the present document may not be entirely in accordance with the ETSI/PNE Rules.Proposed national transposition datesDate of adoption of this EN:3 September 1999Date of latest announcement of this EN (doa):31 December 1999Date of latest publication of new National Standardor endorsement of this EN (dop/e):30 June 2000Date of withdrawal of any conflicting National Standard (dow):30 June 2000SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)6(GSM 03.45 version 6.0.1 Release 1997)0ScopeThe present document deals with the procedures allowing the technical realization of the Group 3 facsimile Servicewithin the GSM PLMN using transparent Network support, according to the definition of Teleservice 61 and 62specified in the GSM 02.03 [2].0.1ReferencesThe following documents contain provisions which, through reference in this text, constitute provisions of the presentdocument.· References are either specific (identified by date of publication, edition number, version number, etc.) ornon-specific.· For a specific reference, subsequent revisions do not apply.· For a non-specific reference, the latest version applies.· A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the samenumber.· For this Release 1997 document, references to GSM documents are for Release 1997 versions (version 6.x.y).[1]GSM 01.04: "Digital cellular telecommunication system (Phase 2+): "Abbreviations andacronyms".[2]GSM 02.03: "Digital cellular telecommunication system (Phase 2+); Teleservices supported by aGSM Public Land Mobile Network (PLMN)".[3]GSM 02.34: “Digital cellular telecommunications system (Phase2+): High Speed Circuit SwitchedData (HSCSD) - Stage1”.[4]GSM 03.10: "Digital cellular telecommunication system (Phase 2+); GSM Public Land MobileNetwork (PLMN) connection types".[5]GSM 03.34: "Digital cellular telecommunications system (Phase2+): High Speed Circuit SwitchedData (HSCSD) - Stage2.[6]GSM 04.02: "Digital cellular telecommunication system (Phase 2+); GSM Public Land MobileNetwork (PLMN) access reference configuration".[7]GSM 04.08: "Digital cellular telecommunication system (Phase 2+); Mobile radio interface layer 3specification".[8]GSM 04.21: "Digital cellular telecommunication system (Phase 2+); Rate adaption on the MobileStation - Base Station System (MS - BSS) interface".[9]GSM 07.01: "Digital cellular telecommunication system (Phase 2+); General on TerminalAdaptation Functions (TAF) for Mobile Stations (MS)".[10]GSM 07.03: "Digital cellular telecommunication system (Phase 2+); Terminal AdaptationFunctions (TAF) for services using synchronous bearer capabilities".[11]GSM 09.07: "Digital cellular telecommunication system (Phase 2+); General requirements oninterworking between the Public Land Mobile Network (PLMN) and the Integrated ServicesDigital Network (ISDN) or Public Switched Telephone Network (PSTN)".[12]CCITT Recommendation T.35: "Procedure for the allocation of CCITT members' codes".[13]CCITT Recommendation F.160 Fascicle II.5: "General operational provision for the internationalpublic facsimile".SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)7(GSM 03.45 version 6.0.1 Release 1997)[14]CCITT Recommendation T.4 Fascicle VII.3: "Standardization of group 3 facsimile apparatus fordocument transmission".[15]CCITT Recommendation T.30 Fascicle VII.3: "Procedures for document facsimile transmission inthe general switched telephone network".[16]CCITT Recommendation V.21 Fascicle VIII.l: "300 bits per second duplex modem standardizedfor use in the general switched telephone network".[17]CCITT Recommendation V.24 Fascicle VIII.l: "List of definitions for interchange circuits betweendata terminal equipment (DTE) and data circuit-terminating equipment (DCE)".[18]CCITT Recommendation V.25bis Fascicle VIII.l: "Automatic calling and/or answering equipmenton the general switched telephone network (GSTN) using the 100-series interchange circuits".[19]CCITT Recommendation V.27ter Fascicle VIII.l: "4 800/2 400 bits per second modemstandardized for use in the general switched telephone network".[20]CCITT Recommendation V.29 Fascicle VIII.l: "9 600 bits per second modem standardized for useon point-to-point 4-wire leased telephone-type circuits".[21]CCITT Recommendation V.33 Fascicle VIII.l: "14 400 bits per second modem standardized foruse on point-to-point 4-wire leased telephone-type circuits".[22]CCITT Recommendation X.300 Fascicle VIII.6: "General principles for interworking betweenpublic networks, and between public networks and other networks for the provision of datatransmission services".[23]CCITT Recommendation V.17: "A 2-wire modem for facsimile applications with rates up to 14400 bit/s".0.2Definitions and abbreviationsIn addition to those below, abbreviations used in the present document are listed in GSM 01.04 [1].BCSBinary Coded Signalling phase of Facsimile transmission as per CCITT T.30CT105Interchange Circuit 105 as per CCITT V.24CT106Interchange Circuit 106 as per CCITT V.24CT107Interchange Circuit 107 as per CCITT V.24CT108.2Interchange Circuit 108/2 as per CCITT V.24CT109Interchange Circuit 109 as per CCITT V.24CT114Interchange Circuit 114 as per CCITT V.24CT115Interchange Circuit 115 as per CCITT V.24FA/MTThe Fax Adaptor specifically located at MT sideFA/IWFThe Fax Adaptor specifically located at IWF sideMSGMessage phase of Facsimile transmission as per CCITT T.30All protocol entities from CCITT Facsimile Recommendations (T.4 and T.30) apply; in the present document they arereferenced to in the same way as in the above CCITT Recommendations (see also annex I to the present document).SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)8(GSM 03.45 version 6.0.1 Release 1997)1Service definitionThe fixed network Group 3 Facsimile service, as basically defined in CCITT Recommendation F.160, is an internationaltelematic service for ISO A4 document transmission between two facsimile stations.The service specification is comprised of two parts: the control protocol described in CCITT Recommendation T.30,and the document transmission coding described in CCITT Recommendation T.4.The GSM facsimile Teleservice is intended to allow facsimile connections between group 3 apparatus using:-a GSM PLMN as a stand alone facility, for mobile to mobile communication;-a GSM PLMN to gain access to fixed networks PSTN and ISDN, for mobile to/from land communication.For this Teleservice, the document coding is as CCITT Recommendation T.4 with no modifications. The protocol usedis CCITT Recommendation T.30 modified within the PLMN as detailed in the present document.The interworking between different networks is based on CCITT Recommendation X.300.The particular features of this Teleservice are:-it uses point-point communication;-the information transfer capability is dual "Speech"/"Group 3 Facsimile" for Teleservice 61 and "Group 3Facsimile" only for Teleservice 62;-both mobile originated and terminated calls are supported;-the information transfer mode is circuit, duplex, synchronous and symmetric;-different end-to-end transfer rates are used within the same call to take advantage of the better radio path errorrate;-use of a standard synchronous terminal adaptation function (as per GSM 07.03) within the MS.2Network architectureThe network architecture applicable to this Teleservice is shown in figure 1/03.45, below.FAXBSSMSC/IWFPSTNISDNPLMNvMTvFAXFigure 1/03.45: Network architectureThis shows the case of mobile to fixed network interworking. For mobile to mobile calls, there would effectively be aloop back within the PLMN, using two IWFs.SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)9(GSM 03.45 version 6.0.1 Release 1997)3Reference configuration at the mobile stationThe mobile reference configurations described in this clause are defined as per GSM 04.02.TASTAFAX Adapt.TARf)MT0MT1MT1MT1MT2MT2UmFAX/FAX2w/FAX2wFAXR/FAX2wa)b)c)d)e)
Mobile Station FAX Adapt.FAX Adapt.FAX Adapt.FAX Adapt.Figure 2/03.45: Reference configurationsThe Teleservice definition in GSM 02.03 regards the group 3 facsimile terminal as a 2-wire analogue terminatedequipment. In order to connect this to the MT2 a separate "Fax Adaptor" device is necessary.This configuration, shown in figure 2a/03.45, has to be considered as the standard configuration, so that all the existingGroup 3 facsimile apparatus can be connected to the PLMN.An alternative realization would be to combine a standard group 3 facsimile machine and the Fax Adaptor into aspecially developed "GSM facsimile machine", directly providing a digital output. Although such a device must appearto the MT2 as identical to the Fax Adaptor (i.e. with an identical interface and protocol), it would allow for asignificantly smaller and simpler facsimile machine. This configuration is shown in figure 2d/03.45 and is regarded as adesirable alternative.In addition of course, it is always possible to realize an MT0, as per figure 2f/03.45, where both the facsimile andmobile termination functions are considered to be part of one integrated unit.The remaining configurations concern the use of an S interface and are considered as optional configurations. Their useis for further study.The particular terminal adaptation functions used are those detailed in GSM 07.03 and the interface to the MT2 used issynchronous V.24 with an option for support of V.25bis procedures for autocalling and autoanswering.SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)10(GSM 03.45 version 6.0.1 Release 1997)3.1Fax Adaptor functionalityThe Fax Adaptor block, figure 3/03.45, is intended to specifically complement the Group 3 facsimile apparatus in orderto be able to communicate over a GSM PLMN.R2WPROTOCOL MONITORING
& CONTROL COMPOSITE
MODEMTONE HANDLINGFigure 3/03.45: Fax Adaptor schemeWhether it has to be a function internal to the GSM PLMN, or an external accessory associated with the Group 3apparatus, is beyond the scope of the present document, and in any case, does not affect at all the working of theprocedure as here described.It can be functionally partitioned in two sections:-an analogue section, dealing with:-the modulation and demodulation processes according to CCITT Recommendation V.21, V.27ter, V.29 andV.17 as explained in T.4 and T.30;-handling of the signalling on the 2-wire path to the facsimile machine, including autocalling and autoanswerfunctions where necessary (see clause 6).-a digital section, dealing with:-monitoring and where necessary, manipulation of the T.30 protocol as detailed in the rest of the presentdocument;-overall control of the adaptor;-connection over the synchronous V.24 interface to the MT as described in GSM 07.03;-where necessary, autocalling and autoanswering functions according to V.25bis.In the following this specification will reference the Fax Adaptor functionality, considering the most general case whereit operates as a full-featured (see figure 3/03.45) separate block (see figure 2a/03.45), as this reference configuration isimplicitly or explicitly exhaustive of all service related technical aspects.3.2GSM Facsimile Machine functionalityThe special GSM facsimile machine shown in the MS configuration of figure 2d/03.45 has a similar functionality to thedigital part of the Fax Adaptor, but without any of the analogue portions.It appears over the V.24 interface as identical to the Fax Adaptor, i.e. the MT2 needs to have no knowledge of theparticular configuration used.When necessary this reference configuration, will be explicitly referenced to in the following; otherwise all technicalaspects relevant to the configuration implicitly apply.SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)11(GSM 03.45 version 6.0.1 Release 1997)4Connection typesTable 1/03.45 shows the connection elements attributes applicable to this Teleservice (note), adapted from GSM 03.10.NOTE:Teleservice 61 includes both speech and data connection types, but Teleservice 62 only the dataconnection type.Table 1/03.45: Elements of connection typesProtocol typeof Figure 6 of TSGSM 03.10Access to TAFof the MobileStationRadio interfaceconnection elementIntermediaterateRA1 to RA2BS-MSC/IWFconnectionelementModel 6: Speech-Speech/GSM-CCITTA-lawModel 5:FacsimileGroup 3C/D/S UDI- 14.4 kbit/s- 9.6 kbit/s- 4.8 kbit/s- 2.4 kbit/s(note)C/D/S UDI- 14.5 kbit/s- 12.0 kbit/s-
6.0
kbit/s-
3.6
kbit/s C/D/S UDI- 16 kbit/s- 16 kbit/s-
8 kbit/s-
8 kbit/sC/D/S UDI- 64 kbit/s- 64 kbit/s- 64 kbit/s- 64 kbit/sModel 5bFacsimileGroup 3C/D/S UDI- 14.4 kbit/s-
9.6 kbit/s-
4.8 kbit/s-
2.4 kbit/sC/D/S UDI14,5 or 2X12 kbit/s12
or 2X6 kbit/s6 kbit/s6 kbitsC/D/S UDI16 or 2X16 kbit/s16 or 2X8 kbits8 kbit/s8 kbit/sC/D/S UDI- 64 kbit/s- 64 kbit/s- 64 kbit/s- 64 kbit/sNOTE: The highest Access Rate actually supported in this teleservice will be consistent with the highest Access Rateof the Transparent Bearer Service provided by the Network Operator.C = Circuit switchedS = SynchronousD = Full-duplexUDI = Unrestricted Digital InformationTable 1a/03.45Fax modem ratesNo. of substreamsRadio i/f rateIntermediate RatePadding Scheme14.4 kbit/s1214,5 kbit/s12 kbit/s16 kbit/s16 kbit/s12.0 kbit/s1214,5 kbit/s12 kbit/s16 kbit/s16 kbit/sFA(5D + S)FA(5D + S)9.6 kbit/s1212 kbit/s6 kbit/s16 kbit/s8 kbit/s7.2 kbit/s1212 kbit/s6 kbit/s16 kbit/s8 kbit/sFA(3D + S)FA(3D + S)4.8 kbit/s16 kbit/s8 kbit/s2.4 kbit/s16 kbit/s8 kbit/sFA = Padding is performed in the FA(nD + mS) means that m SYNC frames will be added every n’th DATA frameThe MS must support the combinations in table 1a/03.45, restricted to what has been negotiated between the MS and thenetwork.All transitions from one combination in table 1a/03.45 to another combination in the same table, must be supported bythe MS, as long as the fax modem rate is kept constant or the transition of fax modem rate is performed in steps of 2,4kbit/s.The figure 4/03.45 shows the scheme of a typical GSM PLMN connection for this Teleservice, considering respectivelyR and S access at Network Termination.SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)12(GSM 03.45 version 6.0.1 Release 1997)To grant full support to the CCITT Recommendation T.30, requiring different transmission speeds, the followingstrategy shall be implemented:-PLMN provides for four Access Rates only, that is 14 400 bits/s, 9600 bit/s, 4800 bit/s, 2400 bit/s;-radio channel modification procedures are used for switching between Speech phase and facsimile phase, as wellas to select the suitable Access Rate (14 400,9600/4800/2400 bit/s) within the facsimile phase, as resulting fromthe preliminary end-to-end negotiation between the terminals;-to transport Binary Coded Signalling (BCS) requiring a synchronous 300 bit/s bit-rate, speed conversion will beused at both the PLMN ends.S I/F2wAdaptorMT1PLMN2wFAXAdaptorMSC/IWFFAXAdaptorDTE2wDCEMT2PLMN2wGR 3 ApparatusFAXAdaptorMSC/IWF3.1 kHz audio3.1 kHz audioR I/F (V.24)GR 3 ApparatusGR 3 ApparatusGR 3 ApparatusFAXTAFigure 4b/03.45: Optional Teleservice connection (F.F.S)4.1Information transfer protocol modelThe Figure 5/03.45 depicts the conceptual protocol model for this Teleservice, deduced from model 5 and 5b of Figure6/03.10.The main point to be underlined is that all the protocol modules specific for this Teleservice are confined in the FaxAdaptation functions at both the MT and IWF ends. Note that model
5b of figure 6/03.10 details the placing of thesplitting and combiner function for multislot configurations.SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)13(GSM 03.45 version 6.0.1 Release 1997)T.30RA2RA1'FECFECRA2RA1I/F CctI/F CctMobile StationBase StationMSC/IWFR
I/FRadio I/F
BSS-MSC
I/F
Fax Adapt.
Fax Adaptation
function
Fax Adaptation
functionT.30RA1RA1'Figure 5/03.45: Information transfer protocol model4.2Interactions with T.30The philosophy of this specification is to allow the T.30 protocol to pass transparently wherever possible, through theFax Adaptors at both ends of the PLMN channel. Manipulations are only made to the protocol where necessary toovercome problems resulting from the differences between the PSTN and the GSM system. Basically, these problemsfall into four categories:-supporting facsimile on a digital connection type;-bit errors during transfer of BCS frames;-the need to change speed to reduce the impact of bit errors during transfer of Fax encoded Messages;-inability to support some features of T.30.4.2.1Link control strategyThough the T.30 procedure is plain half-duplex, between the FAs at both the GSM PLMN ends a full-duplex modeconnection will be established. Information transfer is structured in fixed length blocks, carrying either data receivedfrom the local modem, or idle synchronization patterns.Establishment, maintenance and release of the data circuit is performed autonomously by each FA, by properly handlingthe physical interface to its local modem.Due to the rigid timeout constrains in T.30 protocol procedure, which will be actually concatenated to the proceduredefined here for the GSM connection part, a strictly forwardonly approach is adopted for data link control; that is noretransmission means are explicitly introduced to recover corrupted information blocks.Although in the majority of cases the T.30 protocol can take care of lost frames and easily recover, there are someparticularly critical points where two consecutive segments in the procedure, without any interposed acknowledgement,require different transmission speeds (BCS speed/Message speed).In these cases, to grant that a correct change-over from one modem type to another takes place at both the PLMN ends,some additional protection is necessary in the GSM environment. This protection, actually at the beginning and at theend of the Fax page transmission, is given by means of a confirmation mechanism, whereby the originating FA waitswhile transmitting a fixed pattern until an explicit acknowledgement is received from the terminating FA. In these casesan interruption of the normal T.30 information flow may eventually result.SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)14(GSM 03.45 version 6.0.1 Release 1997)Aiming at minimizing any possible delay in the end-to-end transmission between the two facsimile apparatuses, the FAswill pass on information without error control of the message integrity (note). To this regard, however, it is worthunderlining that an essential requirement in this procedure is the detection of some key messages exchanged between theterminals, carrying basic control information. Hence, in parallel to the primary information passing process, acontinuous monitoring of the information flowing across the FA is necessary, to detect these messages, fully checked intheir logical integrity.NOTE:All V.21 modems in the FAs shall use the faster response time provided by CCITT Rec. V.21 (see table2/V.21) for OFF to ON transition of CT109 and CT106.In addition, as detailed below, some fields in some frames may need to be changed.4.2.1.1Message detectionWhile in BCS, the following frames have to be detected:-DIS/DTC, to monitor all operational parameters proposed to the sender terminal by the receiver terminal;-DCS, to realize (see table 2/T.30) the actual message transmission speed accepted by the sender terminal and therelevant message transfer direction;-NSF, to inhibit Non-Standard Facilities, if explicitly required by the user Fax Adaptor configuration;-DCN, to initiate the Call release procedure.During the Message phase (C phase of T.30) a single bit pattern has to be detected, the EOL character, a uniquecodeword that can never be found within a valid line of Fax coded Data (see CCITT Recommendation T.4, subclause4.1.2), and therefore used to control the buffer level in each FA, as detailed in the following subclause 5.2.6.4.2.2Speed conversion for BCS phasesGiven the signalling load caused by the Channel Mode Modify procedure, rather than changing the radio channel speedto 300 bit/s to carry the BCS frames, a speed conversion mechanism is exploited at both the PLMN ends, allowing tomaintain the Channel rate of the Message phase (14 400/9600/4800/2400 bit/s) during BCS phases.A speed conversion factor can be defined as:Fax Message speed (14 400 or 9600 or 4800 or 2400 bit/s)---------------------------------------------------------------------Standard BCS speed (300 bit/s)which will assume the value 8 or 16 or 32 or 48, depending on the actual Message speed negotiated between theterminals.On the basis of the above speed conversion factor, in the originating FA up-conversion to Message speed will beperformed according to the repetition algorithm specified in subclause 5.2.3.2.In the terminating FA, down-conversion to the BCS speed will require a decimation algorithm (see subclause 5.2.3.3);this algorithm is assumed implementation dependent, and hence its actual definition is beyond the scope of the presentdocument.As the actual Access Rate over the GSM-TCH may change throughout the Call, speed conversion factor needs to beupdated in both FAs.The FA/IWF will update this value upon successful completion of a CMM procedure (see subclause 4.3.2).The FA/MT which does not have direct access to the GSM signalling channel (except for MT0 configuration), shallestimate the actual Access Rate established over the GSM-TCH from the effective Access Rate of the MT data interface(or any other means in case of MT0); this check shall be performed whenever a BCS frame is sent towards the Radiopath after which a change for GSM-TCH Access Rate may be expected (e.g., DIS and DCS frames for Normal Faxmode, PPR and CTC frames for Error Correction Mode).SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)15(GSM 03.45 version 6.0.1 Release 1997)4.2.3Compatibility checkingSome features of T.30 cannot be supported in the GSM PLMN environment. Fax Adaptation function is in charge ofdealing with such compatibility checking.4.2.3.1Group 1 and Group 2 supportGroup 1 and Group 2 equipments are not supported by the Teleservice as described in the present document.To this purpose, any tonal signalling specific to the above kind of Fax apparatus will be ignored by the Fax adaptationfunction at MS and IWF.4.2.3.22 400 bit/s handshakingOnly standard 300 bit/s Binary Coded Signalling is supported. To this purpose the FA will ignore this capability withinthe B segment of T.30 procedure, looking for DIS frame, by default, from V.21 modem only.4.2.3.3Non-standard facilitiesNon-standard facilities are supported in so far they are not in conflict with the standard procedure described in thepresent document. All the relevant BCS frames are passed end-to-end, unless an explicit deletion is required by the user(e.g. by a specific input at the Fax Adaptor associated with the MS). In this case, upon detection (see subclause 4.2.1.1)of the NSF frame identifier (the Facsimile Control Field octet according to T.30 terminology), the whole HDLC frameshall be stripped and replaced by a GSM specific NSF frame, containing a Country Code and a unique identification ofthe FA manufacturer, encoded as per CCITT T.35 and according to national regulations; the Information field of thisNSF frame shall have a maximum length of 6 octets, and shall not require any specific functionality in the PLMN.4.2.3.412 000 and 7200 bit/s Facsimile Document TransferEnd-to-end transfer of T.4 information at 12 000 and 7 200 bit/s can be supported, even if this Bearer Service is notprovided by a GSM PLMN.To this purpose a 14 400 bit/s or 9 600 bit/s Access Rate shall be used in the PLMN, by exploiting only part of theavailable bandwidth. The originating FA will add padding information to data received from the MSG modem, beforetransmission over the GSM-TCH; the terminating FA will remove the same information to restore the net 12 000 or 7200 bit/s continuous data stream to be transmitted over its local MSG modem.The relevant procedures are fully described in sections 5.2.3.4 and 5.2.3.5.4.2.3.5Procedure interruptsProcedure interrupts are only possible in Teleservice 61; in case of Teleservice 62 any attempt to invoke procedureinterrupts by MMI on the MT (see subclause 4.3.1 below) will be ineffective.4.2.4Speed checkingUpon receiving DIS/DTC frame, the FA/IWF shall perform a basic speed checking procedure, aiming at verifyingcompatibility between the bit-rate possibilities offered by the called Fax apparatus (bit fields 11, 12, 13, 14 in the IF)and the actual Access Rates allowed on the GSM PLMN (2 400/4 800/9 600/14400 bit/s); in addition, some of these bitrates may result inhibited during the call, if a speed lower than 9 600 bit/s has been chosen by the user in the call set upmessage (for example if a better error rate is required).The following cases may occur:-some of the bit-rates indicated in DIS/DTC are not allowed on GSM-TCH (e.g. the max speed indicated in setupis 9 600 bit/s, while DIS/DTC requests V.33); a possible strategy to cater for this case is altering the indication inDIS/DTC to a compatible value (e.g. V.29) by forcing appropriately the relevant bits (note); other strategies arepossible and allowed, as long as the same goal of supporting the progress of the call is pursued, by constrainingthe Fax apparatuses to use as message speeds the access rates actually available in the PLMN.SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)16(GSM 03.45 version 6.0.1 Release 1997)NOTE:Is beyond the scope of this specification to specify the implementation strategy adopted to recalculate theframe CRC after the manipulation; additional delays, if any, shall not have a significant impact on T.30operability.-the full set of bit-rates indicated in DIS/DTC are not compatible with the allowed Access Rates on GSM-TCH(e.g. the max speed indicated in setup is 2 400 bit/s while DIS/DTC requests V.29 only); in this case the call shallbe failed;-the full set of bit-rates indicated in DIS/DTC are compatible with the allowed Access Rates on GSM-TCH; in thiscase no action shall be taken, independently of the access rate actually established.It should be noted that the "14400 bit/s" as max speed indication in the SETUP message, does not preclude theestablishment of a Call towards a Fax GR 3 equipment supporting only 9600, 4 800 and 2 400 bit/s as Message speed.As a matter of fact, due to the multiplexing mechanism for BCS phases the initial Access Rate (14 400 bit/s) will affectonly the connection part between the called MS and the associated IWF, whilst the appropriate Message speed will beactually negotiated during the initial BCS phase, and settled upon reading the appropriate field in DCS frame (seesubclause 4.2.1.1). Therefore, if a request for MSG transmission is received, without a valid DCS frame being detectedin advance (hence the message speed is undefined), the FA/IWF shall release the call immediately.4.3Radio Channel Modification ProceduresThere are two reasons why the characteristics of the radio channel may need to be changed during a call.Firstly, for the swap from speech to data and vice versa. In this case the In Call Modification procedure as detailed inGSM 04.08 is carried out.Secondly, if a T.30 speed drop back is requested, a channel mode modify procedure as detailed in GSM 04.08 isinitiated to match the radio channel rate to the facsimile transmission speed to optimize the error rate.4.3.1In Call Modification (ICM)Applies only for Teleservice 61.The speech to facsimile change is initiated by MMI at the MS as in other data services starting the ICM procedure viaMODIFY signalling. CT108.2 ON condition towards MT is a basic requirement to allow speech/data transition takeplace.Additionally, the data call direction (DCD) must be known to both the FA's because of a correct tone handling. TheDCD identifies the call direction from the calling to the called station according to CCITT T.30 phase "A" tonal signals.The DCD is derived from the evaluation of the behaviour of the mobile Fax machine. No later than 3 sec afterconnecting the Fax apparatus to the line the FA/MT is able to determine the DCD. If a CNG tone or nothing is detectedby the FA/MT the mobile Fax station is the calling station, if a CED tone or a BCS signal is detected by the FA/MT themobile Fax station is the called station. The FA/MT indicates this towards the MT by means of CT105:
CT105 OFFcondition indicates "mobile terminated", CT105 ON condition indicates "mobile originated". The detection of CT105condition and subsequent triggering of the MODIFY message has to be done 3 sec after reception of the ON conditionof CT108.2.A reverse DCD compared with the initial call setup direction is indicated to the FA/IWF by means of the "Reverse CallSetup Direction" (RCSD) information element within the MODIFY message. If the MODIFY message had containedthis information element, the same information element shall be included in the MODIFY COMPLETE message (ACK).On the basis of RCSD and additional information about the initial call setup direction (e.g. Transaction Identifier flag asper GSM 04.07), the FA/IWF shall resolve the actual DCD.At DCD condition "mobile originated" the FA/IWF has to transmit CNG if neither CED nor a BCS signal has beenalready received, otherwise nothing. At the DCD condition "mobile terminated" the FA/IWF has to transmit CED. Atthe moment when the CT107 goes to ON condition the FA/MT has to generate CED if CT105 was in ON condition,otherwise nothing (see subclauses 6.2.1 and 6.2.3).Selection of the speech phase from the data phase (T.30 Procedure Interrupt request) may be initiated by the mobile Faxmachine as well as by the fixed network fax machine (refer to the diagrams in figure II.-10/03.45 and II.-11/03.45).SIST EN 300 931 V6.0.1:2003

ETSIEN 300 931 V6.0.1 (1999-09)17(GSM 03.45 version 6.0.1 Release 1997)Upon receipt of the "alert operator" tone request will be accepted by manual intervention via MT (phone off-hook), andis reflected to the Fax Adaptor (GSM Facsimile machine) by CT106 and CT109 going in OFF condition.Upon monitoring the transit of the necessary sequence of BCS signals specific for PRI the CT108.2 goes to OFFcondition causing ICM from the Fax data phase to the speech phase. In case of Procedure Interrupt request from thefixed network side (figure
II-10/03.45), a guard timer in the MS is necessary to protect against the possible loss of theresponse to the PRI-Q(PIN/PIP) sent from the MS. After the execution of ICM CT107 is set to OFF condition finishingthe Fax data phase.Subsequent re-selection of the data phase will be by manual intervention via the MS causing CT108.2 going to ONcondition initiating ICM.During the speech phase of a procedure interrupt, the "phone off-hook" condition of the MT is reported via the FaxAdaptor "R" interface (CT106/109 in OFF condition) to the fax apparatus which must remain functionally connected tothe Fax Adaptor to maintain the connection.The precise operation of the Fax Adaptor for the support of procedure interrupt is implementation dependent.4.3.2Channel Mode Modify (CMM)The channel mode modification procedure is only initiated by the FA/IWF. Its purpose is to adjust the radio channel bitrate to match the message speed negotiated end-to-end between the facsimile machines.The FA/IWF enters the CMM routine upon detecting the DCS frame sent either from the MS or from the PSTN.In the first case, FA/IWF being actually the receiving side in the facsimile document transmission, the CMM procedureis executed as soon as the end of frame is detected.That is, FA/IWF monitors the DCS frame and, if the requested rate
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