ETSI EN 300 945 V6.0.1 (1999-09)

Digital cellular telecommunications system (Phase 2+) (GSM); Rate adaption on the Mobile Station - Base Station System (MS - BSS) Interface (GSM 04.21 version 6.0.1 Release 1997)

DEN/SMG-040421Q6

Digitalni celični telekomunikacijski sistem (faza 2+) – Prilagoditev hitrosti na mobilno postajo – Vmesnik sistema baznih postaj (MS-BSS) (GSM 04.21, 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 300 945 V6.0.1:2003 - Digital cellular telecommunications system (Phase 2+) (GSM); Rate adaption on the Mobile Station - Base Station System (MS - BSS) Interface (GSM 04.21 version 6.0.1 Release 1997)

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Digital cellular telecommunications system (Phase 2+) (GSM); Rate adaption on the Mobile Station - Base Station System (MS - BSS) Interface (GSM 04.21 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 300 945 Version 6.0.1SIST EN 300 945 V6.0.1:2003en01-december-2003SIST EN 300 945 V6.0.1:2003SLOVENSKI
STANDARD



SIST EN 300 945 V6.0.1:2003



EN 300 945 V6.0.1 (1999-09)European Standard (Telecommunications series)Digital cellular telecommunications system (Phase 2+);Rate adaption on the Mobile Station - Base Station System(MS - BSS) Interface(GSM 04.21 version 6.0.1 Release 1997)GLOBAL SYSTEM
FOR MOBILE COMMUNICATIONSRSIST EN 300 945 V6.0.1:2003



ETSIEN 300 945 V6.0.1 (1999-09)2(GSM 04.21 version 6.0.1 Release 1997)ReferenceDEN/SMG-040421Q6 (8r00300o.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 300 945 V6.0.1:2003



ETSIEN 300 945 V6.0.1 (1999-09)3(GSM 04.21 version 6.0.1 Release 1997)ContentsIntellectual Property Rights.5Foreword.51Scope.62References.62.1Abbreviations and definitions.73General approach.73.1Overview of the multislot data rates.74The RA0 Function.94.1Asynchronous-to-Synchronous Conversion (RA0).94.2Break signal.104.3Overspeed/Underspeed.104.4Parity Bits.104.5Flow Control.105The RA1 Function.115.1Adaptation of synchronous data rates up to 38,4 kbit/s.115.1.1Network Independent Clocking.125.1.1.1Multiframe Structure.125.1.1.2Encoding and compensation.126The RA1’’ function.136.1Rate adaptation of 48 kbit/s user rates with DTE/DCE status to 64 kbit/s.136.2Rate adaptation of 56 kbit/s user rate to 64 kbit/s.137The RA2 Function.148The RA1/RA1' Function.148.1Single slot rates.148.1.1Radio interface rate of 14,5 kbit/s.158.1.1.1Multiframe structure over the radio-interface.158.1.1.2Radio-interface data block for TCH/F14.4
channel coding.168.1.2Radio Interface rate of 12 kbit/s.178.1.4Radio Interface rate of 6 kbit/s.188.1.5Radio Interface rate of 3,6 kbit/s (transparent services only).198.1.6Synchronisation.198.1.7Idle frames.198.2Multislot rates.198.2.1TCH/F14.4 multislot operation.198.2.2AIURs up to 38,4 kbit/s using TCH/F9.6 and TCH/F4.8 channel codings.208.2.3AIURs up to 38,4 kbit/s using TCH/F14.4
channel coding.208.2.4AIUR of 48 kbit/s; Intermediate rate of 64 kbit/s; Radio interface rate of 5´ 12 kbit/s.218.2.5AIUR of 48 kbit/s; Intermediate rate of 64 kbit/s; Radio interface rate of 4´ 14,5 kbit/s.218.2.6AIUR of 56 kbit/s; Intermediate rate of 64 kbit/s;.218.2.7AIUR of 56 kbit/s; Intermediate rate of 64 kbit/s; Radio interface rate of 4 ´ 14,5 kbit/s.218.2.8AIUR of 64 kbit/s; Radio interface rate of 6 ´ 12 kbit/s.228.2.9AIUR of 64 kbit/s; Radio interface rate of 5 ´ 14,5 kbit/s.229The RA1' Function.229.1Synchronous user rates up to 9,6 kbit/s.229.2Synchronous user rates from 9,6 kbit/s onward; TCH/F9.6/4.8 channel codings.239.3Synchronous user rates from 9,6 kbit/s onward; TCH/F14.4 channel coding.2310The Split/Combine and Padding-functions.2410.1Data frame distribution into the substreams/channels by the Split/Combine function.2410.1.1Data frame distribution into the substreams/channels by the Split/Combine function (TCH/F9.6 andTCH/F4.8 channel codings).24SIST EN 300 945 V6.0.1:2003



ETSIEN 300 945 V6.0.1 (1999-09)4(GSM 04.21 version 6.0.1 Release 1997)10.1.2Data block distribution into the substreams by the Split/Combine function (TCH/F14.4 channelcoding).2410.2Substream numbering in transparent operation.2510.2.1Substream numbering for TCH/F14.4 channel coding.2510.3Initial Substream Synchronisation for TCH/F9.6 and TCH/F4.8 channel codings.2610.3.1Initial Substream Synchronisation for TCH/F14.4 channel coding.2610.4Action on loss of synchronisation.2610.4.1Non-transparent services (TCH/F9.6 and TCH/F4.8 channel codings).2610.4.2Transparent services (TCH/F9.6 and TCH/F4.8 channel codings).2610.4.3Non-transparent services (TCH/F14.4 channel coding).2710.4.4Transparent services (TCH/F14.4 channel coding).2710.5Network independent clocking.2710.5.1Network Independent Clocking for TCH/F14.4 channel coding (both single- and multilinks).2710.5.1.1Negative compensation.2710.5.1.2Positive compensation.2810.6Padding TCH/F frames when the AIUR is not a multiple of 9,6 or 4,8 kbit/s.2810.6.1Padding for TCH/F14.4 channel coding.2811Support of Non-Transparent Bearer Services.2911.1Support of non-transparent operation for TCH/F9.6 and TCH/F4.8 channel codings.2911.2Support of non-transparent operation for TCH/F14.4 channel coding.3012Figures on Frame structures.30Annex A (informative):Stacks of rate adaptation.35A.1Stacks of rate adaptation for 9,6/4,8 kbit/s single slot operation.35A.2Stacks of rate adaptation for 14,4 kbit/s single slot operation.36A.3Stacks of rate adaptation for 9,6/4,8 kbit/s multi slot operation.38A.4Stacks of rate adaptation for 14,4 kbit/s multi slot operation.40Annex B (informative):An example of mapping Network Independent Clocking informationfor TCH/F14.4 when the S-interface is deployed.42Annex C (informative):Change Request History.43History.44SIST EN 300 945 V6.0.1:2003



ETSIEN 300 945 V6.0.1 (1999-09)5(GSM 04.21 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 rate adaptation functions to be used in Mobile Stations (MS) for adapting terminalinterface data rates to the Mobile Station - Base Station System (MS - BSS) interface data rates within the digitalcellular 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.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 300 945 V6.0.1:2003



ETSIEN 300 945 V6.0.1 (1999-09)6(GSM 04.21 version 6.0.1 Release 1997)1ScopeThe present document defines the rate adaptation functions to be used in GSM PLMN Mobile Stations (MS)s foradapting terminal interface data rates to the Mobile Station - Base Station System (MS-BSS) interface data rates inaccordance with GSM 03.10 [3].The provision of these functions will depend on the services a particular station is designed to support.NOTE:The present document should be considered together with GSM 08.20 [9] (Rate Adaptation on the BSS-MSC Interface) to give a complete description of PLMN rate adaptation.2ReferencesThe 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 telecommunications system (Phase 2+); Abbreviations andacronyms".[2]GSM 02.34: "Digital cellular telecommunications system (Phase 2+); High Speed Circuit SwitchedData (HSCSD) - Stage 1".[3]GSM 03.10: "Digital cellular telecommunications system (Phase 2+); GSM Public Land MobileNetwork (PLMN) connection types".[4]GSM 03.34: "Digital cellular telecommunications system (Phase 2+); High Speed Circuit SwitchedData (HSCSD) - Stage 2 Service Description".[5]GSM 05.03: "Digital cellular telecommunications system (Phase 2+); Channel coding".[6]GSM 07.01: "Digital cellular telecommunications system (Phase 2+); General on TerminalAdaptation Functions (TAF) for Mobile Stations (MS)".[7]GSM 07.02: "Digital cellular telecommunications system (Phase 2+); Terminal AdaptationFunctions (TAF) for services using asynchronous bearer capabilities".[8]GSM 07.03: "Digital cellular telecommunications system (Phase 2+); Terminal AdaptationFunctions (TAF) for services using synchronous bearer capabilities".[9]GSM 08.20: "Digital cellular telecommunications system (Phase 2+); Rate adaption on the BaseStation System - Mobile-services Switching Centre (BSS - MSC) interface".[10]CCITT Recommendation V.110: "Support of data terminal equipments (DTEs) with V-Seriesinterfaces by an integrated services digital network".[11]CCITT Recommendation X.30: "Support of X.21, X.21 bis and X.20 bis based terminalequipments (DTEs) by integrated services digital network (ISDN)".SIST EN 300 945 V6.0.1:2003



ETSIEN 300 945 V6.0.1 (1999-09)7(GSM 04.21 version 6.0.1 Release 1997)2.1Abbreviations and definitionsAbbreviations used in the present document are listed in GSM 01.04.Overall data stream: The data stream in those parts of the network where the data flow is not split into multiplechannels.Substream: Stream of data with explicit or implicit numbering between splitter and combiner functions.Channel: A physical full rate channel on the radio interface (TCH/F) independent of the contentsMultislot intermediate rate: Intermediate rate per substream in those parts of the network where the overall datastream is split into substreams.Intermediate rate: Intermediate rate in the overall data stream.Substream rate: The user rate including padding, if applicable, on one individual substream3General approachGSM 03.10 defines the PLMN connection types necessary to support the GSM PLMN data and telematic services.Within the MS there are several different data rate adaptation functions - and a Split/Combine-function in case of amultislot data configuration -
which are combined as shown in GSM 03.10 as part of the connection type.The rate adaptation
functions are RA0, RA1, RA2, RA1', RA1’’ and RA1/RA1'. The RA0, RA1 and RA2 areequivalent to those functions described in CCITT recommendation V.110 [11].The RA1' function is similar to RA1 but has a reduced bit rate output compatible with the coding scheme proposed fordata services on the radio interface.The RA1’’ function is used for converting between synchronous user rates of 48 and 56 kbit/s and the rate 64 kbit/s.The RA1/RA1' is a relay function, used as indicated in GSM 03.10.In multislot data-configurations the overall data stream is split into parallel substreams between the Split/Combine-functions.3.1Overview of the multislot data ratesFor TCH/F9.6 and TCH/F4.8 channel codings,
the multislot intermediate rates are 16 and 8 kbit/s per TCH/F,respectively.For TCH/F14.4 channel coding, the multislot intermediate rate is 16 kbit/s per TCH/F.Between the TE and the Split/Combine-function at the MS, where the overall data stream is not split, intermediate ratesof 8, 16, 32 and 64 kbit/s are applicableSIST EN 300 945 V6.0.1:2003



ETSIEN 300 945 V6.0.1 (1999-09)8(GSM 04.21 version 6.0.1 Release 1997)Table 1: AIUR/Multislot intermediate ratesAir interface userrateDTE/DCEstatusesRA0RA1/RA1’RA1’Multislot intermediaterateFrame typeRadio interfaceratePadding£ 600 bit/sXX8 kbit/s80 bit frames3,6 kbit/s1200 bit/sXX8 kbit/s80 bit frames3,6 kbit/s2,4 kbit/sXX8 kbit/s80 bit frames3,6 kbit/s4,8 kbit/sXX8 kbit/s80 bit frames6 kbit/s9,6 kbit/sXX16 kbit/s or 2´8 kbit/s80 bit frames12 kbit/s or 2´6kbit/s14,4 kbit/sXX2´16 kbit/s or 3´8 kbit/s80 bit frames2´12 kbit/s or3´6 kbit/sP(note 1)16 kbit/sNote 714,5 kbit/s19,2 kbit/sXX2´16 kbit/s or 4´8 kbit/s80 bit frames2´12 kbit/s or4´6 kbit/s28,8 kbit/sXX3´16 kbit/s80 bit frames3´12 kbit/s2 x 16 kbit/sNote 72´14,5 kbit/s38,4 kbit/sXX4´16 kbit/s80 bit frames4´12 kbit/sP(note 6)3 x 16 kbit/sNote73´14,5 kbit/s48 kbit/sXNote 2Note 25´12 kbit/sP(note 6)4 x 16 kbit/sNote74´14,5 kbit/s56 kbit/sNote 2Note 25´12 kbit/s (note3)P(note 6)4x16 kbit/sNote74´14,5 kbit/s64 kbit/sNote 2Note 26´12 kbit/s (note3)P(note 1)5´14,5 kbit/s(note 6)P=Padding usedSIST EN 300 945 V6.0.1:2003



ETSIEN 300 945 V6.0.1 (1999-09)9(GSM 04.21 version 6.0.1 Release 1997)Table 2: AIUR / Intermediate ratesAir interface userrateDTE/DCEstatusesRA0RA1RA1’Intermediate rateFrame typeRadio interfaceratePadding£ 600 bit/sXX8 kbit/s80 bit frames3,6 kbit/s1200 bit/sXX8 kbit/s80 bit frames3,6 kbit/s2,4 kbit/sXX8 kbit/s80 bit frames3,6 kbit/s4,8 kbit/sXX8 kbit/s80 bit frames6 kbit/s9,6 kbit/sXX16 kbit/s80 bit frames12 kbit/s or2´6 kbit/s14,4 kbit/sXX32 kbit/s80 bit frames2´12 kbit/s or 3´6kbit/s1x14,5 kbit/sP(note 1)19,2 kbit/sXX32 kbit/s80 bit frames2´12 kbit/s or 4´6kbit/s28,8 kbit/sXX64 kbit/s80 bit frames3´12 kbit/s2´14,5 kbit/s38,4 kbit/sXX64 kbit/s80 bit frames4´12 kbit/s3´14,5 kbit/sP(note 6)48 kbit/sXNote 4Note 45´12 kbit/s4´14,5 kbit/sP(note 6)56 kbit/sNote 4Note 45´12 kbit/s(note 3)4´14,5 kbit/sP(note 6)64 kbit/sNote 5Note 56´12 kbit/s(note 3)5´14,5 kbit/sP(note 1)(note 6)P=Padding usedNOTE 1:For information on the padding procedure, please refer to clause 10 of the present document.NOTE 2:No multislot intermediate rate; substreams combined at the BSS when TCH/F9.6/4.8 channel coding isused.NOTE 3:AIUR 11,2 kbit/s per channelNOTE 4:For this rateGSM-specific rate adaptation function RA1’’ rather than RA1is applied.NOTE 5:For this rate RA1- and RA2- adaptations are not applied.NOTE 6:Padding used as specified for TCH/F14.4
channel codingsNOTE 7:At the network side, RA1’/RA1 not applied; instead a TCH/F14,4-specific adaptation RA1’/RAA’ used(GSM 08.20)4The RA0 Function4.1Asynchronous-to-Synchronous Conversion (RA0)The RA0 Function is only used with asynchronous interfaces. Incoming asynchronous data is padded by the addition ofstop elements to fit the nearest higher rate defined by 2 to the power n ( where n£ 6) times 600 bit/s or, if applicable, toeither 14,4 or 28,8 kbit/s. Thus both 75 bit/s and 300 bit/s user data signalling rates shall be adapted to a synchronous600 bit/s stream. The resultant synchronous stream is fed to RA1 or RA1'.SIST EN 300 945 V6.0.1:2003



ETSIEN 300 945 V6.0.1 (1999-09)10(GSM 04.21 version 6.0.1 Release 1997)Asynchronous user rateSynchronous user rate£ 0.6 kbit/s0.6 kbit/s1,2 kbit/s1,2 kbit/s2,4 kbit/s2,4 kbit/s4,8 kbit/s4,8 kbit/s9,6 kbit/s9,6 kbit/s14,4 kbit/s14,4 kbit/s19,2 kbit/s19,2 kbit/s28,8 kbit/s28,8 kbit/s38,4 kbit/s38,4 kbit/s4.2Break signalThe RA0 shall detect and transmit the break signal in the following fashion:If the converter detects 2M to 2M+3 bits, all of start polarity, where M is the number of bits per character in the selectedformat including start and stops bits, the converter shall transmit 2M+3 bits of start polarity.If the converter detects more than 2M+3 bits all of start polarity, the converter shall transmit all these bits as startpolarity.The 2M+3 or more bits of start polarity received from the transmitting sides shall be output to the receiving terminal.The terminal must transmit on circuit 103 at least 2M bits stop polarity after the start polarity break signal beforesending further data character. The converter shall then regain character synchronism from the following stop to starttransition.4.3Overspeed/UnderspeedA RA0 shall insert additional stop elements when its associated terminal is transmitting with a lower than nominalcharacter rate. If the terminal is transmitting characters with an overspeed of up to 1 %, the asynchronous-to-synchronous converter may delete stop elements as often as is necessary to a maximum of one for every eight charactersat 1 % overspeed. The converter on the receiving side shall detect the deleted stop elements and reinsert them in thereceived data stream (circuit 104).The realization of overspeed handling, as described above, at the interface to the associated terminal is implementationdependent. Possible implementations are e.g. the reduction of the length of the stop elements according to V.110 [9] orincreased data rates between the TA and terminal.4.4Parity BitsPossible parity bits included in the user data are considered as data bits by the RA0 function (and RA1 function).4.5Flow ControlWhere applicable, this function is as specified in the relevant terminal adaptation function Specification (see GSM 07series).SIST EN 300 945 V6.0.1:2003



ETSIEN 300 945 V6.0.1 (1999-09)11(GSM 04.21 version 6.0.1 Release 1997)5The RA1 FunctionThis function is used to adapt between the synchronous user rates, or the output of the RA0 function and theintermediate rate of 8, 16, 32 or 64 kbit/s.5.1Adaptation of synchronous data rates up to 38,4 kbit/sSynchronous user rateIntermediate rate£ 2,4 kbit/s8 kbit/s4,8 kbit/s8 kbit/s9,6 kbit/s16 kbit/s14,4 kbit/s32 kbit/s19,2 kbit/s32 kbit/s28,8 kbit/s64 kbit/s38,4 kbit/s64 kbit/sA CCITT V.110 80 bits frame is constructed using the user data bits received (from the RA0 in the asynchronous case),the values of the S bits are deduced from the R interface.Adaptation of 600 bit/s to 8Kbit/s is performed by 8 times consecutive duplication of each user data bit. (Figure 9)Adaptation of 1200 bit/s to 8 Kbit/s is performed by 4 times consecutive duplication of each user data bit. (Figure 8)Adaptation of 2400 bit/s to 8kbit/s is performed by 2 times consecutive duplication of each user data bit. (Figure 7)Adaptation of 4800 bit/s to 8 Kbit/s is performed by transmitting the bit stream with no duplication. (Figure 3)Adaptation of 9600 bit/s to 16 Kbit/s is performed by transmitting the bit stream with no duplication (the emitting periodis halved with respect to the 4800 bit/s case). (Figure 3)Adaptation of 14400 bit/s to 32 Kbit/s is performed as for 3600 bit/s to 8 kbit/s (the emitting period is divided by fourwith respect to the 3600 bit/s case).( Adaptation of 3600 bit/s to 8 kbit/s is performed by transmitting the bit stream withno duplication.) (Figure 12)Adaptation of 19200 bit/s to 32 Kbit/s is performed as for 4800 bit/s to 8 kbit/s (the emitting period is divided by fourwith respect to the 4800 bit/s case). (Figure 3)Adaptation of 28800 bit/s to 64 Kbit/s is performed as for 3600 bit/s to 8 kbit/s (the emitting period is divided by eightwith respect to the 3600 bit/s case). (Figure 12)Adaptation of 38400 bit/s to 64 Kbit/s is performed as for 4800 bit/s 8 kbit/s (the emitting period is divided by eightwith respect to the 4800 bit/s case). (Figure 3)The CCITT V.110 80 bit frames shown in Figures 3 and 12 are used. The D bits are used to convey the user data and theS and X bits are used to convey channel control information according to the relevant terminal adapter functionSpecification.The E bits are used to convey the following information:i)User Data Rate - E1, E2, E3
(for single slot operation see Figure 4, and for multislot operation Figure 4 andsubclause 10.7)ii)Network Independent Clocking - E4, E5, E6iii)Multiframe Synchronisation - E7The order of transmission of the 80 bit frame is from left to right and top to bottom.SIST EN 300 945 V6.0.1:2003



ETSIEN 300 945 V6.0.1 (1999-09)12(GSM 04.21 version 6.0.1 Release 1997)5.1.1Network Independent ClockingSynchronous data signals received by the MT from the DTE at the MS or by IWF from the modem on the PSTN maynot be synchronized to the PLMN. The following method shall be used to enable transfer of those data signals and thecorresponding bit timing information via the V.110 frames. Such a situation would exist where the signals received fromthe modem at the IWF require its own clock or where the signals received from the DTE at the MS employs its ownnetwork independent clock. In any case, the frequency tolerance of the clocks involved is 100 ppm.5.1.1.1Multiframe StructureThe transmitting end of the GSM PLMN connection shall establish a multiframe structure utilizing bit E7 consisting offour frames by setting E7 in every fourth frame to binary 0. This structure is identical to the use of E7 in V.110 (andX.30) except that such a multiframe structure will exist for all user data rates. This frame synchronization will beachieved and maintained during the entire call so that corrections for the network independent clocking by the receivingend of the GSM PLMN connection can be easily recognized and applied based on the code words (in c1, c2, c3, c4 andc5) positioned in bits E4, E5 and E6 of two consecutive V.110 frames as illustrated in figure 1. Thus, the multiframestructure allows for one 5-bit code words to be transmitted every two V.110 frames for the purposes of networkindependent clocking. The two code-words may be different from
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