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1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 4 Network architecture | The network architecture applicable to this Teleservice is shown in figure 1/03.46 below.
: ββββββββββ :
: β β :
:ββ’ PLMN ββ:
: β β :
: ββββββββββ :
v v : ββββββββββ :
βββββββ ββββββββ β β βββββββββ βββββββββ : β β : βββββββ
β FAX βββ€ MT βββ βββ€ BSS βββ€MSC/IWFββ:ββ’ PSTN ββ:ββ’ FAX β
βββββββ ββββββββ βββββββββ βββββββββ : β β : βββββββ
: ββββββββββ :
: ββββββββββ :
: β β :
:ββ’ ISDN ββ:
: β β :
: ββββββββββ :
Figure 1/03.46: Network architecture
It shows the case of mobile to fixed network interworking. For mobileβtoβmobile calls, there would effectively be a loop back within the PLMN using two IWFs. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 5 Reference configuration at the mobile station | The mobile station reference configurations described in this clause are defined as per GSMΒ 04.02.
<----------------- Mobile station ----------------->
βββββββββ 2-w βββββββββββββ R βββββββ :
a) β FAX ββββΌβββ€FAX Adaptorββββ«ββββββββββββββββ€ MT2 βββ«
βββββββββ βββββββββββββ : βββββββ :
: :
βββββββββ 2-w βββββββββββββ R ββββββββ S βββββββ :
b) β FAX ββββΌβββ€FAX Adaptorββββ«βββ€ TA ββββ«βββ€ MT1 βββ«
βββββββββ βββββββββββββ : ββββββββ : βββββββ :
: :
βββββββββ 2-w βββββββββββββ¬βββββββ S βββββββ :
c) β FAX ββββΌββββββ€FAX Adaptorβ TA βββββββ«βββ€ MT1 βββ«
βββββββββ βββββββββββββ΄βββββββ : βββββββ :
: :
βββββββββ R : βββββββ :
d) β FAX ββββββββββββββββββββββ«ββββββββββββββββ€ MT2 βββ«
βββββββββ : : βββββββ :
: : :
βββββββββ R ββββββββ S βββββββ :
e) β FAX ββββββββββββββββββββββ«βββ€ TA ββββ«βββ€ MT1 βββ«
βββββββββ : ββββββββ : βββββββ :
:
βββββββ :
f) β MT0 βββ«
βββββββ :
Figure 2/03.46: Reference configurations
The teleservice definitions in GSMΒ 02.03 regard the facsimile groupΒ 3 terminal as a 2βwire analogue terminated equipment. In order to connect this to the MT2 a separate "fax adaptor" device is necessary. This configuration, shown in figure 2a/03.46, has to be considered as the standard configuration, so that all the existing facsimile groupΒ 3 terminals can be connected to the PLMN.
An alternative realization would be to combine a facsimile groupΒ 3 terminal and the fax adaptor into a special "GSM facsimile machine", directly providing a digital output. Although such a terminal must appear to the MT2 as identical as the fax adaptor (i.e. with an identical interface and protocol), it would allow for a significantly smaller and simpler facsimile machine. This configuration is shown in figure 2d/03.46.
In addition of course, it is always possible to realize an MT0, as per figure 2f/03.46, where both the facsimile and mobile 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 use is for further study.
The particular terminal adaptation functions used are those detailed in GSMΒ 07.03 for nonβtransparent bearer capability. The interface to the MT2 used is according to CCITT Recommendation V.24 with an option for support of CCITT RecommendationΒ V.25bis procedures for auto calling and auto answering. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 5.1 Fax adaptor functionality | The fax adaptor block, figure 3/03.46, is intended to specifically complement the facsimile groupΒ 3 terminal in order to be able to communicate over a GSM PLMN.
βββββββββββββββββββββ€ββββββββββββββββββββ
β β β
β Composite β β
β Modem β Control, β
2-w β β Protocol β R
βββΌβββ«ββββββββββββββββββββ€ Monitoring ββββ«ββ
β β & β
β Tone β Buffer β
β Handling β β
β β β
βββββββββββββββββββββ§ββββββββββββββββββββ
Figure 3/03.46: Fax adaptor scheme
Whether it has to be a function internal to the GSM PLMN, or an external accessory associated with the facsimile groupΒ 3 terminal, is beyond the scope of the present document, and in any case, does not affect the working of the procedure as described here.
It can be functionally partitioned in two sections:
β an analogue section, dealing with:
β the modulation and demodulation processes according to CCITT Recommendation V.21, V.27ter, and V.29 as explained in CCITT Recommendation T.4 and T.30;
β handling of the signalling on the 2βwire path to the associated facsimile terminal, including auto calling and auto answering functions where necessary (see clause 8).
β a digital section, dealing with:
β overall control of the adaptor;
β monitoring and, where necessary, manipulating the CCITT Recommendation T.30 protocol as detailed in the present document;
β connection to the MT using the interface according to CCITT Recommendation V.24 as described in GSMΒ 07.03;
β buffering of facsimile data;
β transcoding of the CCITT Recommendation T.4 document content for transmission across the radio interface as detailed in the present document;
β where necessary, auto calling and auto answering functions according to CCITT Recommendation V.25bis. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 5.2 GSM facsimile machine functionality | The special GSM facsimile machine shown in the MS configuration of figure 2d/03.46 is similar to the digital part of the fax adaptor, but without any of the analogue portions.
It appears at the CCITT Recommendation V.24 interface as identical as the fax adaptor, i.e. the MT2 needs to have no knowledge of the particular configuration used. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6 Connection types | Table 1/03.46 shows the connection elements attributes applicable to these Teleservices, extracted from GSMΒ 03.10.
Table 1/03.46: Connection elements
Protocol type
Access to TAF
Radio interface
Intermediate
BSβMSC/IWF
of fig.Β 6
of the Mobile
connection element
rate
connection
GSMΒ 03.10
Station
RA1 to RA2
element
Model 6: Speech
ββββ
Speech/GSM
ββββ
CCITT Aβlaw
Model 7:
C/D/S UDI
C/D/S UDI
C/D/S UDI
C/D/S UDI
Facsimile
β 9.6 kbit/s
β 12 kbit/s
β 16 kbit/s
β 64 kbit/s
GroupΒ 3 NT
(β 4.8 kbit/s)
(β 2.4 kbit/s)
C = circuit switched S = synchronous
D = duplex UDI = unrestricted digital information
Figure 4/03.46 shows the scheme of a typical GSM PLMN connection for these teleservices, considering R and S access, respectively, at network termination.
To support the CCITT Recommendation T.30, requiring different transmission rates, the following strategy shall be implemented:
β the channel on the radio interface shall be a full rate channel used for RLP protocol transmission (nonβtransparent network support);
β no modification procedure (Channel Mode Modify: CMM) shall be performed during the data phase of the call;
β the user rate of the MT2 is preferably set to 9Β 600 bit/s;
β the transmission rate between the fax adaptor and the associated facsimile terminal at both ends shall be the same, i.e. there will be only one common endβtoβend transmission rate at any given time;
β the negotiation of the message speed shall be endβtoβend between the two facsimile terminals; this allows also for a message speed of 7Β 200 bit/s to be used;
β the connection between the fax terminals is divided into three logical sections (fax terminal β(1)β fax adaptor β(2)β fax adaptor β(3)β fax terminal);
β flag stuffing is applied by the fax adaptor towards the associated facsimile terminal within the constraints of CCITT Recommendation T.30, to keep the data link active whenever a procedure delay occurs;
β the BCS protocol elements and the facsimile coded data are buffered at both ends of the radio interface (in the fax adaptors), if necessary, to guarantee data integrity;
β a specific fax adaptor protocol (FA protocol) is provided between both the fax adaptors to cater for the appropriate link control.
R
DTE β DCE
βββββ βββββββββββ V ββββββ< >ββββββ βββββ
β G β β β<----114-----β β β G β
β r β β β<----115-----β β β r β
β o β β β β β β o β
β u β β β-----108---->β β β u β
β p β β β<----107-----β P β β p β
β β β β β M β β β
β 3 β β β-----105---->β L S β β 3 β
β β2-wβ Fax β<----106-----β C β 2-wβ β
β t βββΌββ’ Adaptor β<----109-----β MT2 M / βββ β ββΌββ’ t β
β e β β β β I β β e β
β r β β β<----125-----β N W β β r β
β m β β β β F β β m β
β i β β β-----103---->β β β i β
β n β β β<----104-----β β β n β
β a β β β β β β a β
β l β β β<----102---->β β β l β
βββββ βββββββββββ ββββββ< >ββββββ βββββ
Figure 4a/03.46: Standard Teleservice connection
S
β
βββββ ββββββββββ€βββ V ββββββ< >ββββββ βββββ
β G β β β β---------->β β β G β
β r β β β β X bit β β β r β
β o β β β β<----------β β β o β
β u β β β β β β β u β
β p β β β β---------->β P β β p β
β β β β β SA bits β M β β β
β 3 β β β β<----------β L S β β 3 β
β β2-wβ Fax β β β C β 2-wβ β
β t βββΌββ’Adaptor βTAβ---------->β MT1 M / βββ β ββΌββ’ t β
β e β β β β SB bits β I β β e β
β r β β β β<----------β N W β β r β
β m β β β β β F β β m β
β i β β β β β β β i β
β n β β β β---------->β β β n β
β a β β β β D bits β β β a β
β l β β β β<----------β β β l β
βββββ ββββββββββ§βββ ββββββ< >ββββββ βββββ
Figure 4b/03.46: Optional Teleservice connection |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.1 Protocol model | Figure 5/03.46 depicts the protocol model for this Teleservice, deduced from model 7 of figureΒ 6/GSMΒ 03.10.
It should be noted that depending on the particular implementation the R reference point may not explicitly exist. In this case the LAPB protocol and consequently the LAPB entities operating across this interface may be omitted. The protocol stack at the radio interface, however, is not affected by this consideration, i.e. RLP and L2RBOP always apply.
The main point to be underlined is that all the protocol modules specific for this Teleservice are confined in the fax adaptor functions at both the MT and MSC/IWF ends. This includes the layer 2 entity function for LAPB to be operated towards the standard TAF for synchronous nonβtransparent bearer capability.
Mobile station Base station MSC/IWF
<------------------------------------------> <------------> <------------------------------------->
Fax adaptor R I/F Radio I/F BSS-MSC I/F Fax adaptor
-------------------->| | | |<-------------------
T.30ββββββββββ | FA protocol | ββββββββββT.30
βββββ€ β β β β β β β β β β β β β β β β β β β β β β β β β β β β β β β β β β β β β€ βββββ
βFax β | ββββββββ | L2RBOP | ββββββββ | βFax β
βAdaptor β | β L2R β β β β β β β β β β β β β β€L2R β β β β β β β β€Adaptor β
βFunctionβ | LAPB ββββ¬ββββ€ | RLP | βββββ¬βββ | βFunctionβ
β β β β β β β β β β β€L2βRLPβ β β β β β β β β β β β β β€RLPβ | β β
ββββββββββ | ββββ΄ββββ | | βββββ | ββββββββββ
\\ | // \\ | ββββββββββ | // |
\\ | // ββββββ | β\ββββ¬ββ/β | βββββ |
\\ | // βRA1'β | βRA1'βRA1β | βRA1β |
\\ | // ββββββ | ββββββ΄ββββ | βββββ |
\\ | // \ | / \ | / |
βββββββββ|βββββββββ βββββ|βββββ βββββ|βββββ |
βI/F cctβββ€I/F cctβ βFECβββ€FECβ βRA2βββ€RA2β |
βββββββββ|βββββββββ βββββ|βββββ βββββ|βββββ |
Figure 5/03.46: Protocol model for nonβtransparent support |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.2 Principles of the Facsimile Protocol Adaptation | The basic approach of the present document for facsimile groupΒ 3 is:
β to use the standard nonβtransparent network support (including e.g. standard MT) as basically defined in technical specifications GSMΒ 07.01, GSMΒ 07.03, and GSMΒ 09.07;
β to use the CCITT Recommendation T.30 procedure at both ends of the connection between the fax adaptor and the associated facsimile terminal and to pass the protocol elements according to CCITT Recommendation T.30 functionally unchanged wherever possible;
β to use a specific protocol between both the fax adaptors across the radio interface; and
β to intervene within the fax adaptors in order to concatenate the applicable connection sections.
Basically there are four problem areas:
β support of facsimile groupΒ 3 with a digital connection type;
β unpredictable delays on the radio interface due to actual RLP working conditions (ARQ);
β the need to change the transmission rate "locally" in the fax adaptors both in the MS and in the MSC/IWF and to adapt it to the constant user rate of the TAF;
β the inability to support some CCITT Recommendation T.30 features.
To overcome these problems some particular functions within the fax adaptors are necessary, such as:
β buffering of BCS frames and facsimile coded data prior to transfer;
β autonomous interventions such as BCS command inhibiting within the fax adaptors;
β autonomous interactions between any fax adaptor and the associated facsimile terminal such as BCS command/response repetition; and
β provision of a fax adaptor protocol as interchange protocol between the fax adaptors.
Following this strategy, an interchange model is defined concentrating on the facsimile relevant components. According to this model three connection sections can be distinguished:
a) between fax adaptor and associated facsimile terminal;
b) between the both fax adaptors and again;
c) between fax adaptor and associated facsimile terminal.
The fax adaptors fully relying on the standard supporting layers (e.g. TAF) will also have to cater for the correct establishment and control of these layers including traffic channel synchronization and status information exchange in particular with respect to circuit 106 and circuit 109 (according to CCITT Recommendation V.24). Once these circuits have been set to ON (traffic channel synchronization), they must be kept in the ON condition during the entire facsimile phase of a connection (refer subclauseΒ 6.3 "Procedure Interrupts").
βββββββββββ βββββββββββ βββββββββββ βββββββββββ
β β β β β β β β
β Fax ββββ’ FA ββ β β β β β β ββ’ FA ββββ’ Fax β
β β β β β β β β
βββββββββββ ββββββ€βββββ ββββββ€βββββ βββββββββββ
ββββββ΄ββββββββββββββββββββββββββ΄βββββ
β standard supporting layers β
βββββββββββββββββββββββββββββββββββββ
CCITT Recommendation T.30
ββ βββ βββ βββ βββ βββ βββ βββ βββ βββ β β€
CCITT Recommendation CCITT Recommendation
T.30 Fax adaptor protocol T.30
βββββββββββββ€βββββββββββββββββββββββββββ€βββββββββββββ€
<----> <---->
interactions interactions
<--- interventions <---------> interventions --->
Figure 6/03.46: Communication model |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.2.1 Fax Adaptor Protocol | To cater for the appropriate facsimile transmission some protocol elements and their use (procedure) are defined. These protocol elements are exchanged between both fax adaptors. They are defined as follows and are structured as outlined in annexΒ A:
β BCS element:
The BCS element is used to relay CCITT Recommendation T.30 BCS frames. It includes the possibility also to transmit parts of an entire BCS frame (segmentation). This will apply when the BCS frame content β excluding the address and control fields of the BCS frame β to be included exceeds a length of 20 octets (e.g. non standardized frames) which otherwise would cause unacceptable delays when relaying the BCS frame as a whole. For that purpose, the BCS frame element carries information on the integrity of a BCS frame element.
To guarantee the overall integrity of the BCS frames each single element includes a sequence number which is set to zero within each first BCS element carrying either a BCS command or BCS response (i.e. triggered by the preamble). It is incremented by one with each successive element belonging to the same BCS command/response transmitted across the radio interface. The counting is carried out independently for each direction of the element transmission. The number of BCS elements which can be transmitted within one sequence (BCS command/response) is limited to 256.
The fax adaptor receiving those elements checks the correct sequence of the numbers and, by this means, is able to detect loss of BCS elements and to act accordingly.
β BCS abort element:
The BCS abort element is used to indicate to the remote fax adaptor that an error occurred during the BCS frame reception and the transmission of the related BCS frame is to be aborted.
β BCS transmit request element:
The BCS transmit request element is used in two ways:
a) to request initial transmission of a BCS command or response after the preamble element preceding each BCS element sequence carrying such a command/response has been recognized;
b) to request retransmission of previously transmitted BCS elements in case of an error between both the fax adaptors. This applies e.g. if a sequence error has been recognized. The retransmission starts with the BCS element the number of which is indicated in the transmit request.
β Preamble element:
The preamble element is transmitted once for each received preamble as soon as the preamble has been recognized. It is used to switch on the fax modem and to start transmitting the preamble at the remote side of the radio interface 300 ms after the preamble element reception. The duration of the preamble must be the minimum still permitted by CCITT RecommendationΒ T.30.
β Normal data element:
The normal data element is used to relay buffered facsimile data which have been received and transcoded when not operating in error correction mode.
β Error correction data element:
The error correction data element is used to relay buffered facsimile data frames received when operating in error correcting mode. It contains the entire respective data frame excluding the address and control fields of the frame.
β End of data element:
The end of data element is used to indicate the end of the message transmission. Subsequently, a preamble element is to follow.
β TCF element:
The TCF element TCF_OK or TCF_NOK is used to inform the opposite fax adaptor function about the result of the autonomously performed TCF phase. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.2.2 Interactions and interventions within the fax adaptors | Interactions and interventions within the fax adaptors are necessary:
β where protocol elements cannot be passed due to the differences between the PSTN and the GSM system;
β where the content of protocol elements has to be aligned with the capabilities of the supporting GSM PLMN;
β where BCS commands are repeated by the facsimile terminal after a timeβout due to transmission delay across the radio interface;
β where BCS commands must be repeated autonomously by the fax adaptor after a timeβout when no response has been received from the associated facsimile terminal;
β where the retransmission of BCS commands is requested by the associated facsimile terminal sending a CRP frame due to recognized transmission errors;
β where the retransmission of BCS element(s) is requested by any fax adaptor using the BCS transmit request;
β during the transmission of facsimile coded data where the document content is transcoded to save transmission capacity at the radio interface (however, this does not apply when using the CCITT Recommendation T.30 error correction mode).
To perform the necessary interactions and interventions the fax adaptors both in the MS and in the MSC/IWF have to monitor the BCS frames and the facsimile coded data exchanged between the two facsimile terminals and to act as detailed below:
β reception of CCITT Recommendation T.30 BCS protocol elements from the associated facsimile terminal discarding BCS commands repetitively received due to timeβout in the facsimile terminal;
β transmission of CCITT Recommendation T.30 BCS protocol elements to the associated facsimile terminal autonomously repeating BCS commands towards the accepting facsimile terminal if necessary after timeβout or on request by CRP;
β control of the half duplex connections between the fax adaptor and the associated facsimile terminal;
β storage of BCS commands/responses completely received from the associated facsimile terminal;
β relay of the CCITT Recommendation T.30 protocol elements between the two facsimile terminals by using the appropriate FA protocol elements and mapping them onto the particular L2R protocol (L2RBOP) elements and vice versa as indicated below;
β changing information elements of the BCS frames indicating capabilities which cannot be supported by the PLMN;
β transmission/reception of the CCITT Recommendation T.30 training check frames (TCF) to/from the associated facsimile terminal;
β phasing/training with the associated facsimile terminal;
β transcoding of the normal facsimile coded data received from the facsimile terminal and writing them into a buffer in the fax adaptor associated with the transmitting facsimile terminal;
β reading of the facsimile coded data from the buffer for transmission across the radio interface using the appropriate FA protocol elements;
β writing of the facsimile coded data received across the radio interface into a buffer at the receiving end of the connection section between MS and MSC/IWF;
β reading and reverse transcoding of the buffered normal facsimile coded data and transmitting them to the associated facsimile terminal;
β control of a response transmission timer, to guarantee the reception of a response right in time (refer to subclauseΒ 7.2.1.1).
The algorithm for mapping the CCITT Recommendation T.30 information onto the L2R protocol elements consists of three steps:
β generation of the appropriate FA protocol element including the CCITT Recommendation T.30 protocol element (BCS frames or facsimile coded data);
β generation of a single LAPB Iβframe including the FA protocol element in the information field;
β segmentation of a particular LAPB Iβframe into L2RBOP PDUs according to GSMΒ 07.03.
To regenerate the original CCITT Recommendation T.30 protocol element the actions must be reversed at the remote fax adaptor.
The support of guard tones by the fax adaptor in the MSC/IWF is an implementation option. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.2.3 Training Check | The training check sequence (TCF) as per CCITT Recommendation T.30 is exchanged only locally between the fax adaptor and the associated facsimile terminal. However, the subsequent exchange of CFR or FTT is, in principle, endβtoβend. The training check sequence sent by the fax adaptor must have the minimum duration permitted (ref. to CCITT RecommendationΒ T.30).
As a consequence of this local procedure, the fax adaptors have to check the received TCF whether the quality requirements are satisfied. Depending on the result of that check, the fax adaptor recognizing a bad line will eventually change the CFR to be a FTT, indicating a negative training result and transmits the TCF_element (TCF_OK or TCF_NOK).
With the knowledge of the TCF check result of the opposite fax adaptor function and the received response frame (CFR or FTT) from the fax apparatus, the fax adaptor, which generated the TCF, is able to deduce the following phase.
The message transfer phase in the receiving fax adaptor function is entered upon reception of TCF element TCF_OK and CFR. The modem training at transmission speed shall start after reception of the first facsimile coded data from the opposite fax adaptor function or autonomously 5.5s after reception of CFR.
In the other cases, the transmitting fax adaptor function shall repeat the last DCS/TCF sequence 3s after reception of the response, if no new DCS frame from the opposite fax adaptor function is available.
Only in case of a mobile to mobile call (refer to subclause 6.2.4/ GSMΒ 03.46) a TCF_NOK leads to transmission of an invalid TCF.
If no TCF element was received, because of a RLP link reset, until a CFR is received from the fax apparatus, the message phase shall be entered autonomously 5.5s after reception of the CFR or the first facsimile coded data in the receiving adaptation function. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.2.4 Mobile to mobile calls | In this section, an interim solution is described. The final solution depends on the progress in the ITUβT and is expected by the end of 1995.
To get the information about the nature of the call, a GSM specific country code inside the NSF frame is used to identify an inter MSC call.
The GSM country code (refer to CCITT Recommendation T.35) is coded as follows:
bit 8 7 6 5 4 3 2 1
βββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ
β 1 β 1 β 0 β 0 β 1 β 1 β 1 β 1 β
βββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ
In case no NSF has to be transmitted, the IWF shall insert a special NSF frame defined as follows:
FCF FIF
| |
NSF, GSM country code, stuff byte (0)
After reception of an NSF frame in the IWF with a GSM country code, the IWF shall enter a specific inter MSC procedure with the following interventions:
β Insertion of NSC respectively NSS with the above mentioned coding before sending of (CIG)DTC or (TSI)DCS.
β Discarding of received NSC and NSS frames which are generated by the opposite IWF.
β The transmission of TCF sequence is triggered by the reception of the TCF Discriminator. In case of TCF_NOK, an invalid TCF is transmitted to the opposite IWF.
β To save time and to check also the quality of link between the two MSCs, a BCS frame FTT is generated by the IWF and sent to the opposite IWF after reception of an invalid TCF.
In this case the response CFR or FTT from the mobile side shall not be transferred to the other MSC. If an IWF receives an FTT from the opposite IWF the preceding DCS frame should not be automatically repeated after expiration of the command/response timer (T=3s, refer to CCITT RecommendationT.30).
β The response time supervision (Ts=1.6s, refer to subclause 7.2.1.1) within the IWFs is inactive, that means, a response shall be accepted as a valid frame by the receiving IWF when the BCS carrier is detected within 3s after transmission of the previous command.
β The message transfer phase is only entered after reception of the first facsimile coded data from the radio link.
β The facsimile coded data shall be transferred between the IWFs with minimum scan line transmission time equal to 0Β ms (refer to CCITT Recommendation T.4). |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.2.5 Facsimile Message Transfer | |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.2.5.1 Message Transcoding | To save transmission capacity at the radio interface the content of the document shall be transcoded. This applies only, when using the normal facsimile data transfer, i.e. not with the error correction mode.
The facsimile coded data received by the fax adaptor from the facsimile terminal is transcoded and transmitted to the corresponding fax adaptor across the radio interface, where it is transcoded in the reverse direction and transmitted to the receiving facsimile terminal.
The transcoding is based on the minimum line length capability of the T.30 protocol for the normal facsimile data transfer. According to this the transmitting facsimile terminal has to fill up each coded scan line with FILL information to conform to this requirement (ref. CCITT Recommendation T.4).
To take advantage from that, the fax adaptor associated with the transmitting facsimile terminal will force this to use (at least) the standard value of 20Β ms by replacing the applicable parameter value of the exchanged DIS/DTC messages. All FILL information of the facsimile coded data received from the facsimile terminal will be deleted prior to forwarding the data across the radio interface. The fax adaptor associated with the receiving facsimile terminal must recognize and store the originally requested minimum line length to be able to regenerate to correct line length.
It should be noted that the CCITT Recommendation T.4 document coding may be 1βdimensional or 2βdimensional and, in addition, uncompressed. The fax adaptors have to take care of this when transcoding the document content. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.2.5.2 Generation of the normal data element | The normal facsimile coded data which have been transcoded and buffered as described in the present document is segmented for transmission across the radio interface into blocks of max. 936 bits (afterwards constituting a sequence of max. 5 L2RBOP PDUs). Each such block is contained in the information field of a normal data element of the FA protocol (see annex A).
The facsimile message transfer is finalized by a trailing end of data element which allows the transmitting fax adaptor to switch off the message speed modem.
It may be necessary to align the content of the normal data element to octet boundary at the end of the facsimile message transmission, i.e. after the RTC. This is done by appending '0's to the RTC. This fill information may be omitted by the remote fax adaptor. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.2.5.3 Generation of the error correction data element | The content of a FCD frame, if received correctly, is stored by the fax adaptor. Each such block is contained in the information field of a error correction data element of the FA protocol (see annex A).
The facsimile message transfer is finalized by a trailing end of data element which allows the transmitting fax adaptor to switch off the message speed modem. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.3 Procedure interrupts | Procedure interrupts are only supported in Teleservices 61; in case of Teleservice 62 any attempt to invoke procedure interrupts by MMI on the MT (see subclause 6.4 below) will have no effect. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.4 Radio channel modification | This applies to Teleservice 61 only, if a change of the radio channel during the call swapping from speech to facsimile or vice versa is required. For this purpose the inβcall modification procedure (ICM) as detailed in GSMΒ 04.08 is carried out.
The change from speech to facsimile is initiated by MMI at the MS as in other data services starting the ICM procedure via MODIFY signalling . As a basic requirement for this transition, circuit 108.2 (according to CCITT Recommendation V.24) towards the MT must be in the ON condition.
Additionally the data call direction (DCD) must be known to both the FAs because of a correct tone handling. The DCD identifies the call direction from the calling to the called station according to CCITT Recommendation 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 after connecting the fax apparatus to the line the FA/MT is able to determine the DCD. If a CNG tone or nothing is detected by 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 the mobile fax station is the called station. The FA/MT indicates this towards the MT by means of CT105: CT105 in OFF condition indicates "mobile terminated", whereas CT105 ON indicates "mobile originated". The detection of the CT105 condition and subsequent triggering of the MODIFY message has to be done 3 sec after the reception of the ON condition of CT108.2.
A reverse DCD compared with the initial call setup direction is indicated to the FA/IWF by means of the "Reverse Call Setup Direction (RCSD)" IE within the MODIFY message. If the MODIFY message has contained this IE, the same IE shall be included in the MODIFY COMPLETE (ACK) message. On the basis of RCSD and additional information about the initial call setup direction (e.g. transaction identifier flag β ref.Β 04.07), the FA/IWF shall resolve the actual DCD.
At DCD condition "mobile originated" the FA/IWF has to transmit a CNG tone if neither CED nor a BCS signal has been already received, otherwise nothing. At DCD condition "mobile terminated" the FA/IWF has to transmit a CED. At the moment when CT107 goes to ON condition the FA/MT has to generate CED if CT105 was in ON condition, otherwise nothing (see subclauses 8.2.1.1 and 8.2.2.1).
If during the facsimile call the return to speech is necessary (T.30 procedure interrupt request), this must be initiated by the mobile fax machine as well as by the fixed network fax machine (ref. to the diagrams in figure II.14/15). Upon receipt of the alert operator tone the request will be accepted by manual intervention via MT (phone offβhook) and is reflected to the FA by CT106 and CT109 going to OFF condition. Upon monitoring the transit of the necessary sequence of BCS signals specific for PRI the CT108.2 goes to OFF condition causing ICM from the fax data phase to the speech phase.
In case of procedure interrupt request from the PSTN side a guard timer is necessary to protect against the possible loss of the response to the PRIβQ(PIN/PIP) sent by the MS. After the execution of ICM (MODIFY message), CT107 is set to OFF condition finishing the fax data phase. Subsequent reβselection of the data phase will be done by manual intervention via the MS causing CT108.2 going to ON condition initiating ICM.
During the speech phase of a procedure interrupt, the phone offβhook condition of the MT is reported via the FA RβI/F (CT106/109 in OFF condition) to the fax apparatus which must remain functionally connected to the FA to maintain the connection.
A subsequent reverse change to facsimile phase is also carried out by manual intervention at the MT causing ICM. This will be immediately reflected by circuit 107 going to OFF condition. The successful completion of ICM is indicated towards the fax adaptor by circuit 107 going to ON (provided circuitΒ 108/2 is still in the ON condition).
During the speech phase of a procedure interrupt, the condition of the facsimile terminal of the MS is not reported across the CCITT Recommendation V.24 interface. It may remain functionally connected to the fax adaptor, but in a suspended state.
The precise operation of the fax adaptor for the support of procedure interrupt is implementation dependent. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 6.5 Performance constraints | In order to perform the procedures described in the present document the MS and the IWF environment should be designed to be able to transmit and receive facsimile data continuously without any need to flow control the procedure by themselves. This applies specifically for the RLP, L2R, and the LAPB entities within the MT or the IWF, respectively, as well as for the fax adaptor itself.
Furthermore, the RLP entity should be able to make error recovery by using the SREJ command/response. The parameters (timers, repetition counters, etc.) should be set to appropriate values using the negotiation capability of the RLP.
The appropriate setting of parameter values applies also for the LAPB procedure.
In addition it is strongly recommended to operate at an user access rate of 9Β 600Β bit/s, even if the facsimile terminal(s) are not able to work with 9Β 600Β bit/s message speed. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7 Use of terminal adaptation functions | According to the protocol model of the connection types (figure 5/03.46) there are two classes of TAFs to be considered. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.1 Standard TAFs for synchronous services | The TAFs are those described in GSMΒ 07.03 for synchronous bearer capabilities in the nonβtransparent mode, i.e. presently for LAPB only. The rate adaptation functions shall comply with GSMΒ 04.21. The interchange signalling mapping is in accordance with GSMΒ 07.03. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2 Specific TAFs for facsimile service | Integral part of an endβtoβend connection for this Teleservice is the fax adaptor function, located at both the PLMN ends and in charge of:
β establishment and maintenance of a LAPB link between the fax adaptation function and the standard synchronous terminal adaptation function according to GSMΒ 07.03, where applicable;
β establishment and maintenance of an L2RBOP link between the fax adaptors in the MS and in the MSC/IWF according to GSMΒ 07.03;
β transcoding of the document content to be transmitted across the radio interface as described in clause 6 of the present document;
β adaptation of the CCITT Recommendation T.30 protocol procedures to the GSM PLMN environment and generation of the fax adaptor protocol elements as described in clause 6 of the present document.
The main features relevant to the CCITT Recommendation T.30 adaptation functions are detailed in the following.
For better clarification only, in the following a double configuration will be referenced:
β transmitter adaptation function, established at the PLMN side where the terminal is located actually performing document transmission;
β receiver adaptation function, established at the PLMN side where the terminal is located actually receiving the facsimile document.
The proper configuration is settled on both network sides by detecting DIS/DTC frame just at the beginning of the phase B in the CCITT Recommendation T.30 protocol procedure.
The optional error correction mode, as defined in CCITT Recommendation T.4βAnnex A and CCITT Recommendation T.30βAnnex A may be fully supported, provided some specific features are included in the fax adaptor procedure.
These features are relevant to:
β additional BCS frames to be detected;
β handling of the message phase.
The overall framework as described in clause 6 of the present document applies, i.e. also the procedures of the error correction mode are, in principle, run endβtoβend between the two facsimile terminals.
The error correction mode is entered upon detection of the relevant bits in the DIS/DTC frame.
The working principle of the present document is based on the detection, control, deletion, and generation of key messages in the endβtoβend dialogue between the facsimile terminals.
While in BCS phases, the following frames have to be detected:
β DIS/DTC, to monitor all operational parameters of the transmitting terminal;
β DCS, to realize the actual operational parameters, e.g. message transmission speed accepted by the sender terminal and the relevant message transfer direction (see table 2/CCITT Recommendation T.30);
β CFR and MCF, to trigger the message phase;
β CTC/EOR, fixing the retransmission strategy by the facsimile transmitting terminal (error correction mode);
β CTR/ERR, acting as confirmation message and so closing a BCS phase before a new message phase;
β PPR, as above, but after the fourth consecutive PPR request, the BCS phase continues with either CTC or EOR (error correction mode);
β DCN, to initiate the call release procedure.
Furthermore, all BCS command messages have to be monitored to eliminate repeated command messages at the local fax adaptation function and to initiate a repetition of those command messages, if necessary, at the remote fax adaptation function. Additionally, all BCS response messages have to be monitored to be able to clear the former condition. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.1 BCS phase | |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.1.1 BCS command/response procedures | The CCITT Recommendation T.30 procedure is segmented in sections of associated BCS commands and responses. Any command sent by a facsimile terminal must be answered by an appropriate BCS response (refer to Appendix III, CCITT Recommendation T.30). To guarantee that transmission and reception of responses take place right in time, a response transmission (including preamble) shall never be started by the fax adaptor function associated with the command sending terminal later than Ts (response time supervision =Β 1.6s) after reception of previous command. According to the command/response relationship, the fax adaptor receiving a BCS command from its associated facsimile terminal is further on designated as commanding fax adaptor. Similarly, the fax adaptor receiving a BCS response is called the responding fax adaptor. The procedure is as follows:
Prior to receiving any BCS command/response the preceding preamble is recognized and the "preamble element" is transmitted to the remote fax adaptor. There it is used to start transmission of the preamble towards the associated facsimile terminal with a delay of 300 ms. The preamble preceding a BCS response must be sent with minimum duration permitted (ref. to CCITT Recommendation T.30). If necessary, a preamble must be "aborted" and restarted after an appropriate period as indicated in CCITT Recommendation T.30.
In addition, the recognition of the "preamble element" is immediately confirmed to the other fax adaptor by sending a "BCS transmit request element" (with sequence number set to zero). As this confines a synchronization point, no further protocol transaction can take place except exchanging another "preamble element" until the "BCS transmit request element" has been recognized by the related fax adaptor.
The commanding fax adaptor when receiving the initial "BCS transmit request element" as confirmation to the "preamble element" (condition 1), starts forwarding the received BCS command using "BCS elements" and applying segmentation, if necessary (ref. to subclause 6.2.1). A BCS command which has been received correctly from the associated facsimile terminal (condition 2), is stored within the commanding fax adaptor. If both conditions 1 and 2 apply, any forwarding of BCS commands repetitively received from the facsimile terminal is further on inhibited. Any "BCS transmit request element" received from the responding fax adaptor is answered accordingly, i.e. by the requested BCS element(s), if any. If an error occurs during the reception of the BCS command from the associated facsimile terminal, the commanding fax adaptor transmits a "BCS abort element" towards the responding fax adaptor and regards the whole BCS command as not received. Any "BCS transmit request element" is ignored at this stage. The inhibit status is cleared when either an appropriate BCS response is received and forwarded to the facsimile terminal or the connection is released.
The responding fax adaptor receiving "BCS elements" checks their correct sequence (refer to subclauseΒ 6.2.1) and starts reassembling and transmitting the BCS command once either a complete BCS frame or at least the second element of a segmented BCS frame is received from the commanding fax adaptor and no sequence error has been detected. Any "BCS element" received after successful reception of a complete BCS command is ignored. If a BCS command consists of a sequence of BCS frames preceded by a single preamble each BCS frame is forwarded separately across the radio interface. The sequence has to be reconstituted at the responding fax adaptor when sending to the associated facsimile terminal. If necessary, flags are transmitted between the BCS frames.
If during a transmission any required subsequent element is not available, the responding fax adaptor aborts the BCS command transmission to the facsimile terminal, and the rest of the BCS command is not transmitted. The same applies, if due to residual errors on the radio interface (e.g. RLP link reset) "BCS elements" are missing which can be detected by a wrong sequence number. In these cases, any "BCS element" following the error event (e.g. with a number out of sequence) is ignored. The responding fax adaptor may therefore need to use a "BCS transmit request element" in order to ask for (re)transmission of outstanding elements, if any.
If a "BCS abort element" has been received by the responding fax adaptor and the transmission is aborted due to this fact, the complete BCS command including the preceding "preamble element" will be retransmitted autonomously by the commanding fax adaptor.
Contiguously received parts of a BCS command received from the radio interface are stored in the responding fax adaptor. The stored BCS command when completed, is used for autonomous retransmissions towards the associated facsimile terminal which may start at the earliest possible time according to CCITT Recommendation T.30. No repetition counter is provided.
The responding fax adaptor when receiving the initial "BCS transmit request element" as confirmation to the "preamble element" (condition 1), starts forwarding the received BCS response using "BCS elements" and applying segmentation, if necessary (ref. subclauseΒ 6.2.1). A BCS response which has been received correctly from the associated facsimile terminal (condition 2), is stored within the responding fax adaptor. Any "BCS transmit request element" received from the commanding fax adaptor is answered accordingly, i.e. by the requested BCS element(s), if any.
If an error occurs during the reception of the BCS response from the associated facsimile terminal, the responding fax adaptor transmits a "BCS abort element" towards the commanding fax adaptor and regards the whole BCS response as not received. Any "BCS transmit request element" is ignored at this stage. The autonomous command repeat status is cleared when both conditions 1 and 2 apply.
The commanding fax adaptor receiving "BCS elements" checks their correct sequence (refer to subclauseΒ 6.2.1) and starts reassembling and transmitting the BCS response once either a complete BCS frame or at least the second element of a segmented BCS frame is received from the responding fax adaptor and no sequence error has been detected. Any "BCS element" received after successful reception of a complete BCS response is ignored. If a BCS response consists of a sequence of BCS frames preceded by a single preamble each BCS frame is forwarded separately across the radio interface. The sequence has to be reconstituted at the commanding fax adaptor when sending to the associated facsimile terminal. If necessary, flags are transmitted between the BCS frames.
If during a transmission any required subsequent element is not available, the commanding fax adaptor aborts the BCS frame transmission to the facsimile terminal, and the rest of the BCS frame is not transmitted. The same applies, if due to residual errors on the radio interface (e.g. RLP link reset) "BCS elements" are missing which can be detected by a wrong sequence number. In these cases, any "BCS element" following the error event (e.g. with a number out of sequence) is ignored. The commanding fax adaptor may therefore need to use a "BCS transmit request element" in order to ask for (re)transmission of outstanding elements, if any.
If a "BCS abort element" has been received by the commanding fax adaptor and the transmission is aborted due to this fact, the complete BCS response including the preceding "preamble element" will be retransmitted autonomously by the responding fax adaptor.
Contiguously received parts of a BCS response received from the radio interface are stored in the commanding fax adaptor. The stored BCS response when completed, is used for autonomous answering towards the associated facsimile terminal which may start at the earliest possible time according to CCITT RecommendationΒ T.30.
After transmission of a response towards the fax apparatus by the fax adaptor function, after which the fax adaptor function waits for message data (CFR, CTR, MCF after MPS, PPS_MPS, PPS_NULL, ERR after EOR_MPS, EOR_NULL) a repeated BCS command shall be locally responded, without transferring a preamble element towards the radio link.
The fax adaptors have to take care of the control of the local modem. The condition is derived from the reception of certain fax adaptor protocol elements. Additionally, there must be a control of the half duplex transmission path towards the associated facsimile terminal. For that purpose, the receiver signal is monitored and the transmitter is only activated, if no receive signal is active. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.1.2 Compatibility checking | Some features cannot be supported in the GSM PLMN environment. The fax adaptor function is in charge of dealing with such compatibility checking which is carried out by monitoring certain BCS frames (DIS/DTC).
β GroupΒ 1 and groupΒ 2 equipments are not supported by the Teleservice as described in the present document.
β Error limiting mode cannot be supported.
β Only standard 300Β bit/s Binary Coded Signalling is supported. To this purpose the fax adaptor will ignore the 2400Β bit/s capability within the phase B of the CCITT Recommendation T.30 procedure by looking for DIS frames from CCITT Recommendation V.21 modem only.
β Only facsimile message speeds up to and including 9Β 600Β bit/s are supported. For this purpose the fax adaptors are responsible to carry out appropriate actions, e.g. to set the applicable fields in the DIS frame accordingly.
β It is not possible to support nonβstandard facilities since some of these contain proprietary methods of changing the modem speed, invisible to the IWF and hence impossible to track. If an NSF frame occurs, the country code has to be exchanged in the IWF to the GSM specific country code, which is not supported by a standard fax group 3 apparatus and therefore no private procedure is entered (refer to subclauseΒ 6.2.4).
However, nonβstandard BCS frames may carry information which does not affect the correct operation within the PLMN, but is essential for the user (e.g. passwords). Those elements, if any, will be passed endβtoβend by the fax adaptors unless an explicit deletion is required by the user (e.g. by specific input at the fax adaptor associated with the mobile station). |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.1.3 Message speed checking | Although it is strongly recommended to use the maximum user rate of the MT2 (9Β 600Β bit/s), a particular user may signal a lower user rate. In this case the fax adaptors have to carry out the following additional procedures:
β max speed indicated in the call setβup message is 4Β 800Β bit/s:
β if the fax adaptor receives a DIS or DTC indicating CCITT Recommendation V.29 only, the call shall be released;
β if CCITT Recommendation V.29 and V.27ter is indicated, this shall be changed to V.27ter;
β if other values are indicated, no action has to be taken;
β max speed indicated in the call setβup message is 2Β 400Β bit/s:
β if the fax adaptor receives a DIS or DTC indicating CCITT Recommendation V.29 only, the call shall be released;
β if CCITT Recommendation V.29 and V.27ter or V.27ter only is indicated, this shall be changed to V.27ter fallback;
β if CCITT Recommendation V.27ter fallback is indicated, no action shall be taken. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.1.4 Control of transmission rate | The controlling entity of the fax adaptor recognizes when a change of the transmission rate β and in conjunction with this a change of the modem function β has to commence. The transmission rate is then changed only locally, i.e. between the facsimile terminal and the fax adaptor at both the MSC/IWF and the MS ends.
The actual message speed and the modem function are derived from the content of the related BCS frames (DIS/DTC, DCS, CTC). |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.1.5 Clocking | The fax adaptor or the GSM facsimile machine will acquire received data bit timing on circuit 115 (according to CCITT Recommendation V.24). The transmitter element timing circuit 114 shall be synchronized to circuit 115.
The clock rate at the CCITT Recommendation V.24 interface will reflect the user rate of the MT2 as indicated in the setβup message. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.2 Message phase | During the message phase (phase C of CCITT Recommendation T.30) a single bit pattern has to be detected, the EOL character (see subclauseΒ 4.1.2/CCITT Recommendation T.4), a unique code word that can never be found within a valid line of facsimile coded data, and is used, as per CCITT Recommendation T.4:
β to identify the start of message phase;
β to control the buffer level;
β to mark the end of message phase (6 consecutive instances). |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.2.1 Normal facsimile data | The message phase (see figure II.6/GSMΒ 03.46 and II.7/GSMΒ 03.46, respectively) at both the PLMN ends is triggered by the transit of a frame (either the CFR or the MCF) sent by the receiving terminal to confirm a previous frame from the transmitting terminal, and marking the end of a BCS phase.
The terminal adaptation function associated with the receiving terminal after receiving facsimile coded data or autonomously 5.5s after detecting the trigger frame (CFR or MCF) will change the modem function to V.27ter or V.29 CCITT Recommendation and initiate the training at the applicable speed.
Following the training segment, 0s bits will be stuffed towards the facsimile terminal (FILL sequence, see subclauseΒ 4.1.2 of CCITT Recommendation T.4), disregarding all information received from the radio interface, until a EOL character is detected, that will mark the beginning of the real phase C (see figureΒ 1/CCITT Recommendation T.4).
If due to a preceding error the message phase cannot be entered, this training must be aborted when a new BCS element is received by the transmitting fax adaptor. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.2.2 Error correction facsimile data | As these facsimile coded data between the fax adaptor and the facsimile terminal are structured in HDLC frames, the handling of this procedure segment will exploit such formatting. The content of such an HDLC frame is further on called a block.
Each such block is included in the information field of a error correction data element of the FA protocol which is processed for transmission across the radio interface as outlined in clause 6.
The message phase (see figure II.8/GSMΒ 03.46) at both the PLMN ends is triggered by the transit of a confirmation frame (CFR, MCF, PPR, CTR or ERR) sent by the receiving terminal and marking the end of the BCS phase.
If four consecutive PPR are counted within the same "partial page", the BCS phase continues.
The transmitter adaptation function will enter the message phase as per CCITT Recommendation T.30 standard procedure.
The terminal adaptation function associated with the receiving terminal after receiving facsimile coded data or autonomously 5.5s after detecting the trigger frame will change the modem function to V.27ter or V.29 CCITT Recommendation and initiate the training at the applicable speed.
Following the training segment, HDLC flags will be stuffed towards the facsimile terminal until a FCD frame is detected, that will mark the beginning of the real phase C.
If due to a preceding error the message phase cannot be entered, this training must be aborted when a new BCS element is received by the transmitting fax adaptor. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.2.3 Buffering of facsimile coded data | The following subclauses only apply, when using the normal facsimile data transfer, i.e. not with the error correction mode. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.2.3.1 Transmitter adaptation function | In the transmitter adaptation function the facsimile coded data being received from the facsimile terminal are transcoded stripping of FILL information and written into the buffer.
If there is enough information available, this data is read out from the buffer, and a FA protocol element is generated which is processed as described in clause 6 to be transferred to the receiver adaptation function using one of the standard TAFs referred to in subclauseΒ 7.1. For that purpose the data is segmented in blocks (see subclauseΒ 6.2.5.2).
Due to the ARQ techniques of the RLP the throughput across the radio interface may be less than the message speed between the transmitting facsimile terminal and the transmitter adaptation function, i.e. the content of the buffer may increase. When a certain threshold is reached from which the fax adaptor can derive that the actual page cannot be transmitted successfully, the connection may be prematurely released.
If the throughput at the radio interface is greater than the message speed between the transmitting facsimile terminal and the transmitter adaptation function (e.g. when the endβtoβend speed is lower than 9Β 600Β bit/s), the buffer may be empty most of the time. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.2.3.2 Receiver adaptation function | In the receiver adaptation function FILL information is transmitted to the facsimile terminal at the beginning of each page, if necessary, to bridge the gap between the training sequence and the real facsimile coded data. In case of normal fax data the FILL 0's can be expanded up to 5s only and therefore after these up to two white scan lines should be inserted, if necessary.
The facsimile coded data received across the radio interface are reβgenerated from the LAPB, L2R and FA protocol elements, reversely transcoded according to the knowledge of the fax adaptor, and written into the buffer. The reverse transcoding consists of insertion of FILL information before the facsimile coded data is forwarded to the facsimile terminal to comply with the recognized minimum line length as defined in CCITT Recommendation T.4.
At the beginning of each page the facsimile coded data to be sent to the facsimile terminal is not read out from the buffer until at least 2 instances of EOL or an RTC have been received or the following buffer size limit, depending on the end to end data transfer rate, has been exceeded:
2 kByte for 2,400 bit/s;
4 kByte for 4,800 bit/s;
6 kByte for 7,200 bit/s;
8 kByte for 9,600 bit/s.
Once this procedure has been started, i.e. during the page transmission, the facsimile coded data is transmitted, however, the following EOL is delayed by inserting additional FILL information, if necessary, until the preβset threshold (2 EOLs or the buffer size limit) is reached again. If the actual coding line is going to exceed 5 s, the threshold is temporarily reduced, i.e. the following EOL is sent. However, the buffering algorithm shall try to reach the preβset threshold again as fast as possible (by inserting FILL also before following EOLs). If no EOL is available to be transmitted to the facsimile terminal for a period greater than 5Β s, the connection will be released by an ordinary receiving facsimile terminal (ref. CCITT Recommendation T.4). |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.3 Disconnect procedure | The transmitter adaptation function, upon detection of the DCN frame (see CCITT Recommendation T.30) sent by the local terminal to indicate the end of the facsimile transmission, initiates the disconnect procedure. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 7.2.4 Timeouts | The overall fax adaptation function is in principle bound to the timing constraints associated with the endβtoβend CCITT Recommendation T.30 procedure. This means that, no matter of the reference configuration used at the mobile station, either the "standard" one (figure 2a/GSMΒ 03.46) or the "GSM facsimile machine" (figure 2d/GSMΒ 03.46), the progress of the call will be mainly subject to the CCITT Recommendation T.30 typical timing protections, settled externally.
However, due to the specific conditions caused by the GSM PLMN system, there is the need for a special support with respect to BCS command repetitions as explained above. For that purpose, the fax adaptors will provide means for local timeβout. The timer will be started and stopped as described in the applicable clauses of the CCITT RecommendationΒ T.30. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 8 Signalling aspects | GSMΒ 07.03 identifies the bearer capability requirements to be supported by the terminal adaptation function in the MT (see GSMΒ 07.01 for BC and HLC coding). The specific signalling requirements are those for "speech" and "facsimile groupΒ 3" or "facsimile groupΒ 3" only, respectively. The MT indicates in the call set up request the requirements, e.g. first speech, second facsimile by sending the bearer capability information element(s) in the appropriate order. For an "auto calling" facsimile request, the facsimile groupΒ 3 bearer capability is sent as the first or the only bearer capability for TeleserviceΒ 61 or 62, respectively.
For interworking between Teleservice 61 and Teleservice 62 refer to GSMΒ 02.03 and 07.01. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 8.1 Handling of tonal signals | Because the CCITT defined service uses modems, there are some signals received from the analogue link at the MSC/IWF and (where used) the fax adaptor which do not have a direct binary representation. These signals cannot therefore be passed across the radio interface in the same way as the CCITT Recommendation T.30 and CCITT Recommendation T.4 information.
These signals are the modem called (CED) and calling (CNG) tones sent at the start of each fax data phase of the call; they are generated locally by the FA/MT and/or FA/IWF, exploiting an endβtoβend time alignment mechanism, triggered by appropriate messages on the GSM signalling channel. The procedure is detailed in the following. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 8.2 Call establishment | |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 8.2.1 Mobile terminated call | The PSTN facsimile groupΒ 3 terminal may be manually or automatically calling. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 8.2.1.1 Speech then facsimile | Refer to the diagram in figure II.1a/03.46 and II.1b/03.46. In both of the figures the initial call setup is mobile terminated. In figure I.1a/03.46 the DCD is also mobile terminated (MT), while the DCD in figureΒ I.1b/03.46 is mobile originated (MO).
In order to make the transition from the speech phase to the facsimile phase, the MODIFY command must be initiated by MMI at the MS.
In the case where a GSM facsimile machine is used, it will turn on circuitΒ 108/2 when it is connected to the line by manual intervention.
In the case where a fax adaptor at MT is used, it will turn on circuit 108/2, when the mobile fax apparatus is connected to the line by manual intervention.
After determination of the DCD and ICM (see subclause 6.4) and on completion of the synchronization process over the radio interface or the RLP establishment, CT107 shall be turned on by the MT; in case where a FA is used, on receipt of CT107 from MT, the FA will complete the tonal handshaking according to the rules in subclause 6.4.
The analogue link at the FA/IWF side will be established in accordance with the T.30 rec.; provided the synchronization process is completed (CT108.2 ON condition), the appropriate tone according to the rules in subclause 6.4 shall be transmitted. In case of DCD mobile terminated the CED tone shall be transmitted after a silence of 1.8 to 2.5 sec (see T.30, 4.3.3.2) from the call being answered; during transmission of CED tone (2.6 sec minimum duration, followed by a delay period of 75 +/β 20 ms) the FA/IWF will process data received from the GSMβTCH as usual, but relevant information (e.g. preamble of a BCS frame) shall be discarded without any buffering. Note that circuit 109 and circuit 106 (according CCITT Recommendation V.24) at the R interface of the MT must be turned on by the fax adaptor at the IWF before any further procedure can be carried out between the fax adaptors and consequently endβtoβend. Once the connection is established, both circuit 106 and circuit 109 are clamped to the ON condition by the fax adaptor at the IWF, so fixing a full duplex mode throughout the whole facsimile phase of the call. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 8.2.1.2 Auto answer | Refer to diagram in figure II.2/GSMΒ 03.46. A call received from the PSTN will cause the MT to turn on circuit 125 (according to CCITT Recommendation V.24) at the R interface.
In the case where a GSM facsimile machine is used, CCITT RecommendationΒ V.25bis auto answering process is handled directly by turning on circuit 108/2.
In the case where a fax adaptor is used, circuit 125 will cause ring current to be sent to the mobile facsimile terminal. The fax adaptor will turn on circuit 108/2, when the mobile facsimile terminal answers the call.
On receipt of circuit 108/2, the MT will answer the call and initiate the synchronization process and the establishment of the RLP across the radio interface. On completion of the synchronization process or RLP establishment, the modem at IWF will automatically be selected and send CED to PSTN facsimile terminal. Also circuit 107 shall be turned on by the MT.
In the case where a fax adaptor is used, on receipt of circuit 107 from MT, the fax adaptor will initiate the tonal handβshake by sending CNG (mandatory).
The analogue links at both the PSTN side and the mobile side (where a fax adaptor is used) will be established in accordance with the appropriate V. series recommendation.
Note that circuit 109 and circuit 106 at the R interface of the MT must be turned on by the fax adaptor at the IWF before any further procedure can be carried out between the fax adaptors and consequently endβtoβend. Once the connection is established, both circuit 106 and circuit 109 are clamped to the ON condition by the fax adaptor at the IWF, so fixing a full duplex mode throughout the whole facsimile phase of the call. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 8.2.2 Mobile originated calls | The PSTN facsimile groupΒ 3 terminal may be manually or automatically answered. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 8.2.2.1 Speech then facsimile | Refer to the diagram in figure II.3a/03.46 and figure II.3b/03.46. In both of the figures the initial call setup is mobile terminated. In figure II.3a/03.46 the DCD is also MO, while in figure II.3b/03.46 the DCD is MT.
In order to make the transition from the speech phase to the facsimile phase, the MODIFY command must be initiated by MMI at the MS, which will result in an establishment of the RLP across the radio interface and connection to line of the FA/IWF.
In the case where a fax adaptor is used, the mobile facsimile terminal must be connected to line by manual intervention at this stage, and will cause the fax adaptor to turn on circuit 108/2 (according to CCITT Recommendation V.24) towards the MT.
In the case where a GSM facsimile machine is used, circuitΒ 108/2 shall be turned on when the GSM facsimile machine is connected to line by manual intervention.
After determination of the DCD and ICM (see subclause 6.4) and on completion of the synchronization process across the radio interface or the establishment of RLP, the modem at the IWF will be automatically selected and send the appropriate modem tone according to the rules in subclause 6.4 to PSTN facsimile terminal. Also circuit 107 shall be turned on by the MT, whereupon the FA/MT will complete the tonal handshaking according to the rules in subclause 6.4.
In the case where a fax adaptor is used, the receipt of circuit 107 shall cause the fax adaptor to connect to line.
The analogue links at both the PSTN side and the mobile side (where a fax adaptor is used) will be established in accordance with the appropriate CCITT V. series recommendation.
Note that circuit 109 and circuit 106 at the R interface of the MT must be turned on by the fax adaptor at the IWF before any further procedure can be carried out between the fax adaptors and consequently endβtoβend. Once the connection is established, both circuit 106 and circuit 109 are clamped to the ON condition by the fax adaptor at the IWF, so fixing a full duplex mode throughout the whole facsimile phase of the call. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 8.2.2.2 Auto calling | Refer to diagram in figure II.4/GSMΒ 03.46. The auto calling procedure of CCITT Recommendation V.25bis is initiated at the CCITT Recommendation V.24 interface. This is done either directly from the GSM facsimile machine or, in the case where a fax adaptor is used, by loop disconnect or DTMF dialling information between the mobile facsimile terminal and the fax adaptor.
When the call is answered, the synchronization process will be started and the RLP will be established across the radio interface.
On completion of the synchronization process across the radio interface or RLP establishment, the modem at the IWF will be automatically selected and send CNG (mandatory) to PSTN facsimile terminal. Also CT107 shall be turned on by the MT.
In the case where a fax adaptor is used, the receipt of circuit 107 shall cause the fax adaptor to connect to line.
The analogue links at both the PSTN side and the mobile side (where a fax adaptor is used) will be established in accordance with the appropriate V. series recommendation.
Note that circuit 109 and circuit 106 (according to CCITT Recommendation V.24) at the R interface of the MT must be turned on by the fax adaptor at the IWF before any further procedure can be carried out between the fax adaptors and consequently endβtoβend. Once the connection is established, both circuit 106 and circuit 109 are clamped to the ON condition by the fax adaptor at the IWF, so fixing a full duplex mode throughout the whole facsimile phase of the call. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 8.2.2.3 Manual calling | Refer to diagram in figure II.5/GSMΒ 03.46. When the call is answered, the RLP will be established across the radio interface providing circuit 108/2 in ON condition.
In the case where a fax adaptor is used, the mobile facsimile terminal must be connected to line by manual intervention at this stage, and will cause the fax adaptor to turn on circuit 108/2 (according to CCITT Recommendation V.24) towards the MT.
In the case where a GSM facsimile machine is used, circuit 108/2 shall be turned on when the GSM facsimile machine is connected to line by manual intervention.
On completion of the synchronization process across the radio interface or RLP establishment, the modem at the IWF will be automatically selected and send CNG (mandatory) to PSTN facsimile terminal. Also circuit 107 shall be turned on by the MT.
In the case where a fax adaptor is used, the receipt of circuit 107 shall cause the fax adaptor to connect to line.
The analogue links at both the PSTN side and the mobile side (where a fax adaptor is used) will be established in accordance with the appropriate CCITT V. series recommendation.
Note that circuit 109 and circuit 106 at the R interface of the MT must be turned on by the fax adaptor at the IWF before any further procedure can be carried out between the fax adaptors and consequently endβtoβend. Once the connection is established, both circuit 106 and circuit 109 are clamped to the ON condition by the fax adaptor at the IWF, so fixing a full duplex mode throughout the whole facsimile phase of the call. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 9 Interworking to fixed networks | PSTN and ISDN only are considered, both used as transit networks to complement the PLMN in the endβtoβend connection between facsimile groupΒ 3 terminal, figure 7/GSMΒ 03.46.
I W F
β β β β β β β β β β β β β β
:βββββββββββββββββββββ :
:βProtocolββ V.21 β :
βββββββ :βControl ββ βββββββββ΄ββ :
β β v v :βMonitor.ββββ€ V.27ter β : ββββββββββββ2-w
ββ§ββββββ§β ββββββββββββββββββββββ ββββββββββββ:βTrans- β β βββββββββ΄ββ:ββββββββββββ’ PSTN ββββ
β TE2 ββββ’ Fax adaptor ββ’ MT ββ ββ’ BSS/MSC β:βcoding β βββ€ V.29 β: ββββββββββββ
βββββββββ βββββββββββββββββββββ βββββββββββ:βBuffers β β Modem β:
/ \ :β β βββββββββββ: βββββββ ββββββββββββ
/ \ :β β :ββ€CodecβββΌββ’ ISDN ββββ
/ \ :βL2RBOP ββββββββββββββββ: βββββββ : ββββββββββββ
/ \ :βMapping ββTone handlingβ: 3.1kHz
/ \ :βββββββββββββββββββββββββ: audio
β β β β β β β β β β β β β β β β β β β β β β β β β β β β
:βββββββββββ ββββββββββ:
:β V.21 β βProtocolβ:
:β βββββββββ΄ββ βControl β:
:βββ€ V.27ter β βMonitor.β:
: β βββββββββ΄βββTrans- β:
2-w: βββ€ V.29 ββcoding β:
ββββ: β Modem ββBuffers β:
: ββββββββββββLAPB- β:
: βHandlingβ:
:ββββββββββββββββL2RBOP β:
:βTone handlingββMapping β:
:βββββββββββββββββββββββββ:
β β β β β β β β β β β β β β
Figure 7/03.46: Network interworking |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 9.1 Interworking to PSTN | As the standard access of facsimile groupΒ 3 terminals for this Teleservice is a 2βwire analogue interface, all the technical requirements for network interworking to PSTN are identical in principle to those encountered for the terminal connection to the MT. The key functional block is the fax adaptor described in clause 6 of the present document.
As far as network interworking is concerned, the main function to be performed by such a block is the correct managing of a composite modem, in accordance with the requirements of CCITT Recommendation T.30:
β CCITT Recommendation V.21 synchronous mode, as standard facility for all BCS phases;
β CCITT Recommendation V.27ter for message speeds of 4 800 and 2 400Β bit/s;
β CCITT Recommendation V.29 for message speeds of 9 600 and 7 200Β bit/s.
The mechanism for selecting the right modem is the following:
β the actual message speed is obtained by detecting the DCS frame (see table 2/CCITT Recommendation T.30) while in BCS phase;
β on entering the message phase, there is an interchange between the V.21 modem and the actual modem agreed upon between the terminals for message transmission;
β on exiting the message phase (RTC) the CCITT Recommendation V.21 modem is selected again.
Times for settling the modem will be in accordance with the requirements of CCITT Recommendation T.30. |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 9.2 Interworking to ISDN | The use of 3.1Β kHz audio bearer capability of ISDN allows for an interworking of PLMN very similar in practice to the scheme for PSTN, figure 7/GSMΒ 03.46. The fax adaptor function is in conformance with the description given in clause 4 and subclause 7.1 of the present document.
Annex A (normative):
Structure and contents of the fax adaptor protocol elements |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 1 Principle structure of an element | Each FA protocol element consists of the element discriminator (one single octet) and the optional information field (arbitrary length).
The elements are transmitted with octet 0, bit 1 first. Received information is forwarded with the same bit sequence as received.
octet: 0 1 ..... n
βββββββββββββββββ¬βββββββββββββββββββββββββββββββββββββββββββββ
β Element β CCITT Recommendation T.30 Protocol Element β
β Discriminator β (optional) β
βββββββββββββββββ΄βββββββββββββββββββββββββββββββββββββββββββββ
β<-- 1 octet -->β<--------------- n octets ----------------->β
Figure A.1/03.46: Principle FA protocol element structure |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 2 Element discriminator coding | |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 2.1 BCS element | bit 8 7 6 5 4 3 2 1
βββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ
β X β 0 β y β y β 0 β 0 β 0 β 0 β
βββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ
β ββββ¬βββ
β 0 1 = begin of a BCS frame
β 1 0 = end of a BCS frame
β 0 0 = middle of a BCS frame
β 1 1 = entire BCS frame
0 = non-final frame
1 = final frame
Figure A.2/03.46: Element discriminator of a BCS element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 2.2 BCS abort element | bit 8 7 6 5 4 3 2 1
βββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ
β 1 β 0 β 1 β 0 β 0 β 0 β 0 β 1 β
βββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ
Figure A.3/03.46: Element discriminator of a BCS abort element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 2.3 BCS transmit request element | bit 8 7 6 5 4 3 2 1
βββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ
β 0 β 1 β 0 β 0 β 0 β 0 β 0 β 1 β
βββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ
Figure A.4/03.46: Element discriminator of a BCS transmit request element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 2.4 Preamble element | bit 8 7 6 5 4 3 2 1
βββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ
β 0 β 1 β 0 β 0 β 0 β 0 β 0 β 0 β
βββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ
Figure A.5/03.46: Element discriminator of a preamble element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 2.5 Normal fax data element | bit 8 7 6 5 4 3 2 1
βββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ
β 0 β 1 β 0 β 0 β 1 β 0 β 0 β 0 β
βββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ
Figure A.6/03.46: Element discriminator of a normal fax data element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 2.6 Error correction fax data element | bit 8 7 6 5 4 3 2 1
βββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ
β 0 β 1 β 0 β 0 β 1 β 0 β 0 β 1 β
βββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ
Figure A.7/03.46: Element discriminator of an error correction fax data element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 2.7 End of data element | bit 8 7 6 5 4 3 2 1
βββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ
β 0 β 1 β 0 β 0 β 1 β 0 β 1 β 0 β
βββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ
Figure A.8/03.46: Element discriminator of an end of data element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 2.8 TCF element | bit 8 7 6 5 4 3 2 1
βββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ
β 1 β 0 β 0 β 1 β 0 β 0 β 0 β 1 β
βββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ
Figure A.9/03.46: Element discriminator of a TCF element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 3 Information field content | |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 3.1 BCS element | CCITT Recommendation ββββββββββββββββββββββββββ
T.30 frame β FCF + [FIF] β
ββββββββββββββββββββββββββ
| |
FA protocol βββββ€βββββ€βββββββββββββββββββββββββ
element β D β SN β β
βββββ§βββββ§βββββββββββββββββββββββββ
D = discriminator octet
SN = sequence number (0 .. 255), bit 1 = LSB
Figure A.10/03.46: Information field content of a BCS element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 3.2 BCS abort element | no information field available |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 3.3 BCS transmit request element | FA protocol βββββ€βββββ
element β D β SN β
βββββ§βββββ
D = discriminator octet
SN = sequence number (0 .. 255),
bit 1 = LSB = Least significant bit |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 3.4 Preamble element | no information field available |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 3.5 Normal fax data element | transcoded ββ€ββββββββββββββββββββββββββββββββββββββββ€β
facsimile β max. 936 bits of facsimile coded data β
data ββ§ββββββββββββββββββββββββββββββββββββββββ§β
β β
FA protocol βββββ€ββββββββββββββββββββββββββββββββββββββββ
element β D β β
βββββ§ββββββββββββββββββββββββββββββββββββββββ
D = discriminator octet
Figure A.11/03.46: Information field content of a normal fax data element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 3.6 Error correction fax data element | CCITT Recommendation
T.4 frame ββββββββββββββββββββββββββ
(FCD or RCP) β FCF + [FIF] β
ββββββββββββββββββββββββββ
| |
FA protocol βββββ€βββββββββββββββββββββββββ
element β D β β
βββββ§βββββββββββββββββββββββββ
D = discriminator octet
Figure A.12/03.46: Information field content of an error correction fax data element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 3.7 End of data element | no information field available |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 3.8 TCF element | bit 8 7 6 5 4 3 2 1
βββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ¬ββββ
β 0 β 0 β 0 β 0 β 0 β 0 β 0 β X β
βββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ΄ββββ
X = 0 : TCF_OK
X = 1 : TCF_NOK
Figure A.13/03.46: Information field content of a TCF element |
1b3a41393e6b9c2d9c5a8ec454e96ca8 | 03.46 | 4 Relationship of FA protocol elements with LAPB, L2RBOP and RLP | Refer also to GSMΒ 07.03
FA protocol βββ€βββββββββββββββββββββββββ
element βDβ optional information β
βββ§βββββββββββββββββββββββββ
| |
LAPB I-frame βββ€ββ€βββββββββββββββββββββββββββ€ββββ
information βAβCβ βFCSβ
field βββ§ββ§βββββββββββββββββββββββββββ§ββββ
| |
ββββ€βββββββββββββββββββββββββββ€βββ€βββ€ββββββββββ
L2RBOP PDU βS1β βS2βS3βarbitraryβ
ββββ§βββββββββββββββββββββββββββ§βββ§βββ§ββββββββββ
| |
RLP βββ€ββββββββββββββββββββββββββββββββββββββββββββββ€ββ
block βHβ βFβ
βββ§ββββββββββββββββββββββββββββββββββββββββββββββ§ββ
D = Discriminator octet,
A = address field, C = control field,
S1, S2, S3 = status octets,
H = RLP header, F = RLP FCS
Figure A.14/03.46: Mapping for a "short" FA protocol element
FA protocol βββ€βββββββββββββββββββ ββββββββββ
element βDβ information ... β
βββ§βββββββββββββββββββ ββββββββββ
| |
LAPB I-frame βββ€ββ€βββββββββββββββββββββ ββββββββββ€ββββ
information βAβCβ β β ... β βFCSβ
field βββ§ββ§βββββββββββββββββββββ ββββββββββ§ββββ
/ / \ \ \ \
ββββ€βββββββββββββ€βββββββββ ββββ€βββββββ€βββ€βββ
L2RBOP PDUs βS0β #1 ββS0β #2 β ... βS1β #n βS2βS3β
ββββ§βββββββββββββ§βββββββββ ββββ§βββββββ§βββ§βββ
/ / \ \ \ \
RLP βββ€βββββββββββββ€βββββ€βββββββββββββ€ββ βββ€ββββββββββββββ€ββ
blocks βHβ βFββHβ βFβ.βHβ βFβ
βββ§βββββββββββββ§βββββ§βββββββββββββ§ββ βββ§ββββββββββββββ§ββ
D = Discriminator octet,
A = address field, C = control field,
S0, S1, S2, S3 = status octets,
H = RLP header, F = RLP FCS
Figure A.15/03.46: Mapping for a "long" FA protocol element
Appendix I (informative): Abbreviations from CCITT Recommendation T.30 and T.4
Table I.1/03.46: Abbreviations from CCITT Recommendation T.30
Abbreβ
Function
Signal format
T.30
T.30
viation
standard
err.corr.
CED
Called station identification
2100 Hz
X
X
CFR
Confirmation to receive
X010 0001
X
X
CRP
Command repeat
X101 1000
X
X
CIG
Calling subscriber identification
1000 1000
X
X
CNG
Calling tone
1100 Hz
X
X
CSI
Called subscriber identification
0000 0010
X
X
CTC
Continue to correct
X100 1000
X
CTR
Response to continue to correct
X010 0011
X
DCN
Disconnect
X101 1111
X
X
DCS
Digital command signal
X100 0001
X
X
DIS
Digital identification signal
0000 0001
X
X
DTC
Digital transmit command
1000 0001
X
X
EOM
End of message
X111 0001
X
EOP
End of procedure
X111 0100
X
EOR
End of retransmission
X111 0011
X
ERR
Response to end of retransmission
X011 1000
X
FCD
Facsimile coded data
0110 0000
X
FCF
Facsimile control field
βββ
X
X
FCS
Frame checking sequence
16 bits
X
X
FIF
Facsimile information field
βββ
X
X
FTT
Failure to train
X010 0010
X
X
MCF
Message confirmation
X011 0001
X
X
MPS
Multiβpage signal
X111 0010
X
NSC
Nonβstandard facilities command
1000 0100
X
X
NSF
Nonβstandard facilities
0000 0100
X
X
NSS
Nonβstandard setβup
X100 0100
X
X
PIN
Procedural interrupt negative
X011 0100
X
X
PIP
Procedural interrupt positive
X011 0101
X
X
PIS
Procedure interrupt signal
462 Hz
X
X
PPR
Partial page request
X011 1101
X
PPS
Partial page signal
X111 1101
X
PRI
Procedure interrupt
X111 XXXX
X
RCP
Return to control for partial page
0110 0001
X
RNR
Receive not ready
X011 0111
X
RR
Receive ready
X111 0110
X
RTN
Retrain negative
X011 0010
X
X
RTP
Retrain positive
X011 0011
X
X
TCF
Training check frame
0... 1.5s
X
X
TSI
Transmitting subscriber identification
X100 0010
X
X
Table I.2/03.46: Abbreviations from CCITT Recommendation T.4
Abbreβ
Function
Signal format
viation
EOL
End of line
0000 0000 0001
RTC
Return to control
6 * EOL
Appendix II (informative): Procedure examples
106, 107, 108/2, 109: circuits according to CCITT Recommendation V.24
(1) manual intervention
(2) mandatory
(3) locally generated by the fax adaptor at IWF
(4) optionally
(5) triggered by delayed CT108.2 (3 sec)
Figure II.1a/03.46: Mobile terminated call β speech then facsimile DCD mobile terminated
106, 107, 108/2, 109: circuits according to CCITT Recommendation V.24
(1) manual intervention
(2) mandatory
(3) locally generated by fax adaptor at IWF
(4) optionally
(5) triggered by delayed CT108.2 (3 sec)
(6) transmitted only if neither CED nor BCS is already received
Figure II.1b/03.46: Mobile terminated call β speech then facsimile DCD mobile originated
106, 107, 108/2, 109, 125: circuits according to CCITT Recommendation V.24
(1) manual or automatic operation
(2) mandatory
(3) either after synchronization or RLP establishment
(4) locally generated by fax adaptor at IWF
Figure II.2/03.46: Mobile terminated call β auto answer
106, 107, 108/2, 109: circuits according to CCITT Recommendation V.24
(1) manual intervention
(2) mandatory
(3) locally generated by fax adaptor at IWF
(4) optionally
(5) triggered by delayed CT108.2 (3 sec)
Figure II.3a/03.46: Mobile originated call β speech then facsimile DCD mobile terminated
106, 107, 108/2, 109: circuits according to CCITT Recommendation V.24
(1) manual intervention
(2) mandatory
(3) locally generated by fax adaptor at IWF
(4) optionally
(5) triggered by delayed CT108.2 (3 sec)
(6) transmitted only if neither CED nor BCS is already received
Figure II.3b/03.46: Mobile originated call β speech then facsimile DCD mobile originated
106, 107, 108/2, 109: circuits according to CCITT Recommendation V.24
(1) manual intervention
(2) mandatory
(3) PSTN fax terminal may be manually or automatically answered
(4) either after synchronization or RLP establishment
(5) locally generated by fax adaptor at IWF
Figure II.4/03.46: Mobile originated call β auto calling
106, 107, 108/2, 109: circuits according to CCITT Recommendation V.24
(1) manual intervention
(2) mandatory
(3) PSTN fax terminal may be manually or automatically answered
(4) either after synchronization or RLP establishment
(5) locally generated by fax adaptor at IWF
Figure II.5/03.46: Mobile originated call β manual calling
Figure II.6/03.46: Mobile originated facsimile transmission
Figure II.7/03.46: Mobile terminated facsimile transmission
Figure II.8/03.46: Mobile originated facsimile transmission (error correction mode)
Figure II.9/03.46: Mobile originated facsimile transmission β error recovery (example)
Figure II.10/03.46: Mobile terminated facsimile transmission β error recovery (example)
Figure II.11/03.46: Mobile originated facsimile transmission β error recovery (example)
Figure II.12/03.46: Mobile originated facsimile transmission β error recovery (example)
Figure II.13/03.46: Mobile originated facsimile transmission β error recovery (example)
Annex B (informative):
Change Request History
Change history
SMG No.
TDoc. No.
CR. No.
Section affected
New version
Subject/Comments
SMG#11
4.1.2
ETSI Publication
SMG#20
5.0.0
Release 1996 version
SMG#27
6.0.0
Release 1997 version
SMG#29
7.0.0
Release 1998version
TSG#06
8.0.0
Agreed to be created as a version 8 for Release 1999
History
Document history
V7.0.0
August 1999
Publication
V8.0.0
January 2000 |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 1 Scope | The present document specifies the digital test sequences for the GSM half rate speech codec. These sequences test for a bit exact implementation of the half rate speech transcoder (GSMΒ 06.20Β [2]), Voice Activity Detector (GSMΒ 06.42Β [6]), comfort noise (GSMΒ 06.22Β [4]) and the discontinuous transmission (GSMΒ 06.41Β [5]). |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 2 References | The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
β’ References are either specific (identified by date of publication, edition number, version number, etc.) or nonβspecific.
β’ For a specific reference, subsequent revisions do not apply.
β’ For a non-specific reference, the latest version applies.
β’ A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same number.
β’ For this Release 1999 document, references to GSM documents are for Release 1999 versions (version 8.x.y).
[1] GSMΒ 01.04: "Digital cellular telecommunications system (Phase 2+); Abbreviations and acronyms".
[2] GSMΒ 06.20: "Digital cellular telecommunications system (PhaseΒ 2+); Half rate speech; Half rate speech transcoding".
[3] GSMΒ 06.21: "Digital cellular telecommunications system (PhaseΒ 2+); Half rate speech; Substitution and muting of lost frame for half rate speech traffic channels".
[4] GSMΒ 06.22: "Digital cellular telecommunications system (PhaseΒ 2+); Half rate speech; Comfort noise aspects for half rate speech traffic channels".
[5] GSMΒ 06.41: "Digital cellular telecommunications system (PhaseΒ 2+); Half rate speech; Discontinuous Transmission (DTX) for half rate speech traffic channels".
[6] GSMΒ 06.42: "Digital cellular telecommunications system (PhaseΒ 2+); Half rate speech; Voice Activity Detector (VAD) for half rate speech traffic channels".
[7] GSMΒ 06.06: "Digital cellular telecommunications system (PhaseΒ 2+); Half rate speech; ANSIβC code for the GSM half rate speech codec".
[8] GSMΒ 06.02: "Digital cellular telecommunications system (PhaseΒ 2+); Half rate speech; Half rate speech coding functions". |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 3 Definitions and abbreviations | |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 3.1 Definitions | Definition of terms used in the present document can be found in GSMΒ 06.20Β [2], GSMΒ 06.21Β [3], GSMΒ 06.22 [4], GSMΒ 06.41Β [5] and GSMΒ 06.42Β [6]. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 3.2 Abbreviations | For the purposes of the present document, the following abbreviations apply:
ETS European Telecommunication Standard
GSM Global System for Mobile communications
For abbreviations not given in this clause, see GSMΒ 01.04Β [1]. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 4 General | Digital test sequences are necessary to test for a bit exact implementation of the half rate speech transcoder (GSMΒ 06.20Β [2]), Voice Activity Detector (GSMΒ 06.42Β [6]), comfort noise (GSMΒ 06.22Β [4]) and the discontinuous transmission (GSMΒ 06.41Β [5]).
The test sequences may also be used to verify installations of the ANSI C code in GSMΒ 06.06Β [7].
Clause 5 describes the format of the files which contain the digital test sequences. Clause 6 describes the test sequences for the speech transcoder. Clause 7 describes the test sequences for the VAD, comfort noise and discontinuous transmission.
Clause 8 describes the method by which synchronization is obtained between the test sequences and the speech codec under test.
Clause 9 describes the optional acceptance testing of the speech encoder and decoder in the TRAU by means of 8 bit A- or ο-law compressed test sequences on the A-Interface.
Electronic copies of the digital test sequences are provided as clause 10, these digital test sequences are contained in archive en_300968v080001p0.ZIP which accompanies the present document. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 5 Test sequence format | This clause provides information on the format of the digital test sequences for the GSM half rate speech transcoder (GSMΒ 06.20Β [2]), Voice Activity Detector (GSMΒ 06.42Β [6]), comfort noise (GSMΒ 06.22Β [4]) and the discontinuous transmission (GSMΒ 06.41Β [5]). |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 5.1 File format | The test sequence files are provided in archive en_300968v080001p0.ZIP which accompanies the present document.
Following decompression, by execution of the 11 "disk*.exe" files, four types of file are provided:
β Files for input to the GSM half rate speech encoder: *.INP
β Files for comparison with the encoder output: *.COD
β Files for input to the GSM half rate speech decoder: *.DEC
β Files for comparison with the decoder output: *.OUT
Tables 1, 2, 3 and 4 define the formats of the four types of file. Each parameter in these tables is contained in a 16 bit word except for the samples of the 8 bit PCM test sequences, which are contained in an 8 bit word each. The left or right justification is indicated in the tables. The size and location of speech parameters in the encoder output (*.COD) and decoder input files (*.DEC) are described in GSM 06.20 [2]. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 5.2 Codec homing | Each *.INP file includes two homing frames at the start of the test sequence. The function of these frames is to reset the speech encoder state variables to their initial value. In the case of a correct installation of the ANSIβC simulation (GSMΒ 06.06Β [7]), all speech encoder output frames shall be identical to the corresponding frame in the *.COD file. In the case of a correct hardware implementation undergoing type approval, the first speech encoder output frame is undefined and need not be identical to the first frame in the *.COD file, but all remaining speech encoder output frames shall be identical to the corresponding frames in the *.COD file.
Each *.DEC file includes two homing frames at the start of the test sequence. The function of these frames is to reset the speech decoder state variables to their initial value. In the case of a correct installation of the ANSIβC simulation (GSMΒ 06.06Β [7]), all speech decoder output frames shall be identical to the corresponding frame in the *.OUT file. In the case of a correct hardware implementation undergoing type approval, the first speech decoder output frame is undefined and need not be identical to first frame in the *.OUT file, but all remaining speech decoder output frames shall be identical to the corresponding frames in the *.OUT file.
Table 1: Encoder input sequence (*.INP) format
Name
Description
No. of bits
Justification
s(n)
Encoder input signal
13
Left
Table 2: Encoder output sequence (*.COD) format
Name
Description
No. of words
Justification
Speech
Speech parameters to the channel encoder
18
Right
Additional information
VAD
SP
Voice activity detection flag
SP flag
1
1
Right
Right
Table 3: Decoder input sequence (*.DEC) format
Name
Description
No. of bits/words
Justification
Speech parameters
Speech parameters to the channel encoder
18 words
Right
BFI flag
UFI flag
SID flag
TAF flag
Bad Frame Indicator
Unreliable Frame Indicator
SIlence Descriptor
Time Alignment Flag
1 bit / 1 word
1 bit / 1 word
2 bits / 1 word
1 bit / 1 word
Right
Right
Right
Right
Table 4: Decoder output sequence (*.OUT) format
Name
Description
No. of bits
Justification
s'(n)
Decoder output signal
13
Left |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 6 Speech codec test sequences | This clause describes the test sequences designed to exercise the GSM half rate speech transcoder (GSMΒ 06.20Β [2]). |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 6.1 Codec configuration | The speech encoder shall be configured to operate in the nonβDTX mode. The VAD and SP flags shall be set to 1 at the speech encoder output. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 6.2 Speech codec test sequences | Table 5 lists the location and size of the speech codec test sequences. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 6.2.1 Speech encoder test sequences | Three encoder input sequences are provided:
β SEQ01.INP β Sequence for exercising the LPC vector quantization codebooks;
β SEQ02.INP β Sequence for exercising the long term predictor codebooks;
β SEQ03.INP β Sequence for exercising the remaining excitation codebooks.
The SEQ01.INP sequence causes the GSM half rate speech encoder to select every vector in the three reflection coefficient vector quantizers at least once. In a correct implementation, the resulting speech encoder output parameters shall be identical to those specified in the SEQ01.COD sequence.
The SEQ02.INP sequence causes the encoder to select at least once every quantization level in the eight bit table of long term filter lags for the first subframe, and every quantization level in the four bit delta lag quantizer for subframes 2, 3, and 4. In a correct implementation, the resulting speech encoder output parameters shall be identical to those specified in the SEQ02.COD sequence.
The SEQ03.INP sequence causes the encoder to select each of the quantization levels at least once for the remaining GSM half rate speech coder parameters: R0 (frame energy), the soft interpolation decision for the LPC coefficients, the four voicing modes, the gain vectors (GSP0) for each of the voicing modes, and the voiced and unvoiced VSELP codebooks. The only exception to this is that two GSP0 levels in the unvoiced mode are not selected. However, these levels are exercised in the GSM half rate speech decoder as described below. In a correct implementation, the resulting speech encoder output parameters shall be identical to those specified in the SEQ03.COD sequence. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 6.2.2 Speech decoder test sequences | Four speech decoder input sequences are provided:
β SEQ01.DEC;
β SEQ02.DEC;
β SEQ03.DEC;
β SEQ04.DEC.
The SEQ01.DEC, SEQ02.DEC, and SEQ03.DEC sequences test the operation of the GSM half rate speech decoder in the absence of channel errors. They are derived from the corresponding SEQXX.INP sequences. In a correct implementation, the resulting speech decoder output shall be identical to the SEQ01.OUT, SEQ02.OUT, and SEQ03.OUT sequences, respectively. Together, these three sequences exercise every quantization level in every codebook in the decoder, with the exception of two GSP0 levels in the unvoiced mode.
The SEQ04.DEC sequence is designed to test the GSM half rate speech decoder under conditions which can result from channel errors. In particular, it is the decoding of LTP lags at the lag table boundaries, given delta lag codes which if incorrectly decoded would point outside the eight bit lag table, that is being tested. Also, the two remaining GSP0 levels in the unvoiced mode are exercised by this sequence. In a correct implementation, the resulting speech decoder output shall be identical to the SEQ04.OUT sequence. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 6.2.3 Codec homing sequence | In addition to the test sequences described above, two homing sequences are provided to assist in codec type approval testing. SEQ05.INP contains one encoderβhomingβframe. SEQ05.DEC contains one decoderβhomingβframe. The use of these sequences is described in GSMΒ 06.02Β [8].
Table 5: Location and size of speech codec test sequences
Disk No.
File Name
No. of frames
Size (bytes)
1
1
2
2
SEQ01.INP
SEQ01.COD
SEQ01.DEC
SEQ01.OUT
2 359
754 880
94 360
103 796
754 880
1
1
2
2
SEQ02.INP
SEQ02.COD
SEQ02.DEC
SEQ02.OUT
781
249 920
31 240
34 364
249 920
1
1
2
2
SEQ03.INP
SEQ03.COD
SEQ03.DEC
SEQ03.OUT
413
132 160
16 520
18 172
132 160
2
2
SEQ04.DEC
SEQ04.OUT
76
3 344
24 320
1
2
SEQ05.INP
SEQ05.DEC
1
320
44 |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 7 DTX test sequences | This clause describes the test sequences designed to exercise the VAD algorithm (GSMΒ 06.42Β [6]), comfort noise (GSMΒ 06.22Β [4]) and discontinuous transmission (GSMΒ 06.41Β [5]). |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 7.1 Codec configuration | The VAD, comfort noise and discontinuous transmission shall be tested in conjunction with the speech encoderΒ [2]). The speech encoder shall be configured to operate in the DTX mode defined in GSMΒ 06.22Β [4]. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 7.2 DTX test sequences | Each DTX test sequence consists of four files:
β Files for input to the GSM half rate speech encoder: *.INP
β Files for comparison with the encoder output *.COD
β Files for input to the GSM half rate speech decoder: *.DEC
β Files for comparison with the decoder output: *.OUT
The *.DEC files are generated from the corresponding *.COD files.
In a correct implementation, the speech encoder parameters generated by the *.INP file shall be identical to those specified in the *.COD file; and the speech decoder output generated by the *.DEC file shall be identical to that specified in the *.OUT file.
Table 6 lists the DTX test sequences and their size in frames. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 7.2.1 Predictor values computation | The computation of the predictor values described in GSMΒ 06.42Β [6] is not tested explicitly, since the results from the computation are tested many times via the spectral comparison and threshold adaptation tests. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 7.2.2 Spectral comparison | The spectral comparison algorithm described in GSMΒ 06.42Β [6] is tested by the following test sequence:
β DTX01.* |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 7.2.3 Threshold adaptation | The threshold adaptation algorithm described in GSMΒ 06.42Β [6] is tested by the following test sequence:
β DTX02.* |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 7.2.4 Periodicity detection | The periodicity detection algorithm described in GSMΒ 06.42Β [6] is tested by the following test sequence:
β DTX03.* |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 7.2.5 Tone detection | The tone detection algorithm described in GSMΒ 06.42Β [6] is tested by the following test sequence:
β DTX04.* |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 7.2.6 Safety and initialization | This sequence checks the safety paths used to prevent zero values being passed to the norm function. It checks the functions described in the adaptive filtering and energy computation, and the prediction values computation given in GSMΒ 06.42Β [6]. This sequence also checks the initialization of thvad and the rvad array:
β DTX05.* |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 7.2.7 Comfort noise test sequence | The test sequences described in subβclauses 7.2.2 to 7.2.6 are designed to exercise the VAD described in GSMΒ 06.42Β [6] and the discontinuous transmission described in GSMΒ 06.41Β [5]. The following test sequence is defined to exercise the comfort noise algorithm described in GSMΒ 06.22Β [4]:
β DTX06.* |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 7.2.8 Real speech and tones | The test sequences cannot be guaranteed to find every possible error. There is therefore a small possibility that an incorrect implementation produces the correct output for the test sequences, but fails with real signals. Consequently, an extra sequence is included, which consists of very clean speech, barely detectable speech and a swept frequency tone:
β DTX07.*
NOTE: Some of the DTX test sequences contain homing frames. The DTX test sequences are therefore only suitable for testing a single transcoding.
Table 6: Location and size of DTX test sequences
size
(bytes)
Disk No.
File Name
No. of Frames
*.INP
*.COD
*.DEC
*.OUT
3
DTX01
460
147 200
18 400
20 240
147 200
3
DTX02
886
283 520
35 440
38 984
283 520
3
DTX03
125
40 000
5 000
5 500
40 000
3
DTX04
317
101 440
12 680
13 948
101 440
3
DTX05
37
11 840
1 480
1 628
11 840
4
DTX06
240
76 800
9 600
10 560
76 800
4
DTX07
1 188
380 160
47 520
52 272
380 160 |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 8 Sequences for finding the 20 ms framing of the GSM half rate speech encoder | When testing the decoder, alignment of the test sequences used to the decoder framing is achieved by the air interface (testing of MS) or can be reached easily on the Abisβinterface (testing on network side).
When testing the encoder, usually there is no information available about where the encoder starts its 20Β ms segments of speech input to the encoder.
In the following, a procedure is described to find the 20 ms framing of the encoder using special synchronization sequences. This procedure can be used for MS as well as for network side.
Synchronization can be achieved in two steps. First, bit synchronization has to be found. In a second step, frame synchronization can be determined. This procedure takes advantage of the codec homing feature of the half rate codec, which puts the codec in a defined home state after the reception of the first homing frame. On the reception of further homing frames, the output of the codec is predefined and can be triggered to. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 8.1 Bit synchronization | The input to the speech encoder is a series of 13 bit long words (104 kbits/s, 13 bit linear PCM). When starting to test the speech encoder, no knowledge is available on bit synchronization, i.e. where the encoder expects its least significant bits, and where it expects the most significant bits.
The encoder homing frame consists of 160 samples, all set to zero with the exception of the least significant bit, which is set to one (0 0000 0000 0001 binary, or 0x0008 hex if written into 16 bit words left justified). If two such encoder homing frames are input to the encoder consecutively, the decoder homing frame is expected at the output as a reaction of the second encoder homing frame.
Since there are only 13 possibilities for bit synchronization, after a maximum of 13 trials bit synchronization can be reached. In each trial, three consecutive encoder homing frames are input to the encoder. If the decoder homing frame is not detected at the output, the relative bit position of the three input frames is shifted by one and another trial is performed. As soon as the decoder homing frame is detected at the output, bit synchronization is found, and the first step can be terminated.
The reason why three consecutive encoder homing frames are needed is that frame synchronization is not known at this stage. To be sure that the encoder reads two complete homing frames, three frames have to be input. Wherever the encoder has its 20 ms segmentation, it will always read at least two complete encoder homing frames.
An example of the 13 different frame triplets is given in sequence BITSYNC.INP (see table 7). |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 8.2 Frame synchronization | Once bit synchronization is found, frame synchronization can be found by inputting one special frame that delivers 160 different output frames, depending on the 160 different positions that this frame can possibly have with respect to the encoder framing.
This special synchronization frame was found by taking one input frame and shifting it through the positions 0 to 159. The corresponding 160 encoded speech frames were calculated and it was verified that all 160 output frames were different. When shifting the input synchronization frame, the samples at the beginning were set to 0x0008 hex, which corresponds to the samples of the encoder homing frame.
Before inputting this special synchronization frame to the encoder, again the encoder has to be reset by one encoder homing frame. A second encoder homing frame is needed to provoke a decoder homing frame at the output that can be triggered to. And since the framing of the encoder is not known at that stage, three encoder homing frames have to precede the special synchronization frame to ensure that the encoder reads at least two homing frames, and at least one decoder homing frame is produced at the output, serving as a trigger for recording.
The special synchronization frame preceded by the three encoder homing frames are given in SEQSYNC.INP. The corresponding 160 different output frames are given in SYNC000.COD through SYNC159.COD. The three digit number in the filename indicates the number of samples by which the input was retarded with respect to the encoder framing. By a corresponding shift in the opposite direction, alignment with the encoder framing can be reached. |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 8.3 Formats and sizes of the synchronization sequences | BIT SYNC.INP:
This sequence consists of 13 frame triplets. It has the format of the speech encoder input test sequences (13 bit left justified with the three least significant bits set to zero).
The size of it is therefore:
SIZE (BITSYNC.INP) = 13 * 3 * 160 * 2 bytes = 12480 bytes.
SEQSYNC.INP:
This sequence consists of 3 encoder reset frames and the special synchronization frame. It has the format of the speech encoder input test sequences (13 bit left justified with the three least significant bits set to zero).
The size of it is therefore:
SIZE (SEQSYNC.INP) = 4 * 160 * 2 bytes = 1280 bytes.
SYNCXXX.COD:
These sequences consists of 1 encoder output frame each. They have the format of the speech encoder output test sequences (16 bit words right justified). The values of the VAD and SP flags are set to one in these files.
The size of them is therefore:
SIZE (SYNCXXX.COD) = (18 + 2) * 2 bytes = 40 bytes
Table 7 summarizes this information.
Table 7: Location, size and justification of synchronization sequences
Disk No.
Purpose of Sequence
Name of Sequence
No. of Frames
Size in Bytes
Justification
5
Bit Synchronization
BITSYNC.INP
39
1 2480
Left
5
Frame Synchronization (input)
SEQSYNC.INP
4
1 280
Left
5
Frame Synchronization (output)
SYNC000.COD
SYNC001.COD
SYNC002.COD
"
"
"
SYNC159.COD
1
1
1
"
"
"
1
40
40
40
"
"
"
40
Right
Right
Right
"
"
"
Right |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 9 Trau Testing with 8 Bit A- and Β΅-law PCM Test Sequences | In the previous clauses tests for the transcoder in the TRAU are described using 13 bit linear test sequences. However, these 13 bit test sequences require a special interface in the Trau and do not allow testing in the field. In most cases the TRAU has to be set in special mode before testing.
As an option, the speech codec tests can be performed with A/ο law compressed 8 bit PCM test sequences on the A interface. These modified input test sequences (*-X.INP) are generated from the original sequences by A or ο law compression. As an input to the encoder they result in modified encoder output sequences (*-X.COD). The same *.dec decoder input sequences as in clause 6.2.2. are then used to produce the output sequences *-X.OUT, which are A- or Β΅-law compressed.
The A- and Β΅-law compression and decompression does not change the homing frames at the encoder input. The format of all A- and ο-law PCM files *-X.INP and *-X.OUT is one sample (8 bit) per byte. The format of all other files is as described in clause 5.
All files are provided in archive en_300968v080001p0.ZIP which accompanies the present document. The 'X' in the tables below with the filenames stands for A (A-law) and U (ο-law), respectively. The decoder input files *.dec are the same as in Table 5 and are not described in this clause.
Table 8: Location and size of compressed 8 bit PCM speech codec test sequences
Disk No.
File Name
No. of frames
Size (bytes)
6/7
6/7
6/7
SEQ01-X.INP
SEQ01-X.COD
SEQ01-X.OUT
2 359
377 440
94 360
377 440
6/7
6/7
6/7
SEQ02-X.INP
SEQ02-X.COD
SEQ02-X.OUT
781
124 960
31 240
124 960
6/7
6/7
6/7
SEQ03-X.INP
SEQ03-X.COD
SEQ03-X.OUT
413
66 080
16 520
66 080
6/7
SEQ04-X.OUT
76
12 160
6/7
SEQ05-X.INP
1
160
Table 9: Location and size of compressed 8 bit PCM DTX test sequences
size
(bytes)
Disk No.
File Name
No. of Frames
*.INP
*.COD
*.OUT
8/9
DTX01-X
460
73 600
18 400
73 600
8/9
DTX02-X
886
141 760
35 440
141 760
8/9
DTX03-X
125
20 000
5 000
20 000
8/9
DTX04-X
317
50 720
12 680
50 720
8/9
DTX05-X
37
5 920
1 480
5 920
8/9
DTX06-X
240
38 400
9 600
38 400
8/9
DTX07-X
1 188
190 080
47 520
190 080
In addition to the testsequences above, special input (seqsyncX.inp) and output (syncxxxX.cod) sequences for frame synchronization are provided. The X again stands for A and ο law compressed PCM. The synchronization procedure is described in clause 8.
Table 10: Location, size and justification of compressed8 bit PCM test sequences
Disk No.
Purpose of Sequence
Name of Sequence
No. of Frames
Size in Bytes
Justification
10/11
Frame Synchronization (input)
SEQSYNCX.INP
4
640
-
10/11
Frame Synchronization (output)
SYNC000X.COD
SYNC001X.COD
SYNC002X.COD
"
"
"
SYNC159X.COD
1
1
1
"
"
"
1
40
40
40
"
"
"
40
Right
Right
Right
"
"
"
Right |
8b410df87e6e8f32e6bbafe6636ff843 | 06.07 | 10 Test sequences for the GSM half rate speech codec | NOTE: This clause is contained in archive en_300968v080001p0.ZIP which accompanies the present document.
Annex A (informative):
Change Request History
Change history
SMG No.
TDoc. No.
CR. No.
Section affected
New version
Subject/Comments
SMG#16
4.0.3
ETSI Publication
SMG#20
5.0.1
Release 1996 version
SMG#23
97-737
A003
5.1.1
UAP60 and Supplementary notes on 06.06 Call Graph Changes
SMG#27
6.0.0
Release 1997 version
SMG#28
6.0.1
ETSI Publication
SMG#29
7.0.0
Release 1998 version
7.0.1
Version update to 7.0.1 for Publication
SMG#31
8.0.0
Release 1999 version
8.0.1
Update to Version 8.0.1 for Publication
History
Document history
V8.0.0
July 2000
One-step Approval Procedure OAP 20001103: 2000-07-05 to 2000-11-03
V8.0.1
November 2000
Publication |
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