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T.30 OverviewAPAC FAE Training

October 2004

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Mindspeed TechnologiesPreliminary Information/Proprietary and

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Purpose of the training

This training is intend for help todebug T.30 transmit problem overMindspeed product. It is not for

debug fax terminal application. Thuswe care about external procedure,signal, timing, handshake. We do notcare much about the fax internaltheory, message contain, data

compress and etc. By understand the T.30 procedure,

help to debug Fax issue base on TDMtrace and FPT signal wave from IPtrace.

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3.1) Protocol Stack

We will focusing on T.30 and mention a littlebit of T.4 and HDLC

Image Compression T.4/T.6Image Compression T.4/T.6

Handshaking T.30Handshaking T.30

Data Link HDLCData Link HDLC

FAX APPLICATIONFAX APPLICATION

DATA PUMP V.27ter, V.29, V.17, V.34DATA PUMP V.27ter, V.29, V.17, V.34

T.30 ProtocolT.30 Protocol

StackStack

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3.3) Terms of fax device:

Originate/Caller: start thecall(Dialer)

Answer/Called/Callee: answer the

call

Sender: device send fax page data(may be not the caller)

Receiver: device receive fax page

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3.2) terms of fax signal:

Spectra and frequency analyze:

Tone: CNG, CED.

Low speed for signaling:

V.21 (300bps)

High speed for Data transmit

V.27ter - up to 4800bps

V.29 - up to 9600bps

V.17 - up to 14400bps

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4) Time sequence of afacsimile call:

A general ideal Fax procedure was been cut into 5 Phase

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facsimile call(callerautomatic operation)

. Off hook

. DialPhase A

. Device identification

Phase B

. Capability negotiation

. Channel probing

Phase C

. Fax message exchange

Phase D

. Post message handshakingPhase E

. Disconnect and

. On hook

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5.a) Phase Procedure

) i l

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6) Typical Fax: GLcomm(TDM) Trace

(Listen the signal wave)

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Trace (non-ECM mode1page)

Ph P d D il

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Phase Procedure Detail(cont.)

Ph A C ll

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Phase A Callestablishment

Call establishment can be realizedmanually and/or automatically.

(It is very few people in North

America are using Manual fax.Automatic fax are more popular)

Caller fax send CND

Called fax send CED (it is optional onmanual mode)

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CNG (Calling tone) Spec

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CNG Tone Wave

CNG spectral

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9) CED,(NSF,CSI,)DIS

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CED Signal

A continuous 2100 Hz 15 Hz tone for a duration of not less than 2.6 seconds and not morethan 4.0 seconds. A 200ms ahead and 75 20 ms silence after transmitting the CED

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Phase B Pre-message Procedure

The pre-message procedure consists of the identification of

capabilities and the commanding of the chosen conditions aswell as the confirmation of acceptable conditions.

i.e. Exchange ID; Negotiate transmit protocol and speed;Training(channel probing)

DIS-digital identification signal(capabilities identification)

DCS-digital command signal(the response of DIS, indicatewhat capability will been used in the transmit)

CFR-confirmation to receive(the training is successful)

FTT-failure to train(the training is failed) (CSI)-called subscriber identification

(NSF)-non-standard facilities

11) bl + (NSF)+

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11) preamble + (NSF)+(CSI) + DIS

Low speed data. Binary @ HDLC framestructure @ V.21:300bps(FSK).

Preamble

The preamble shall precede all binarycoded signalling whenever a new

transmission of information begins in anydirection (i.e. for each line turnaround).This preamble assures that all elements ofthe communication channel (e.g. echosuppressors) are properly conditioned so

that the subsequent data may be passedunimpaired. This preamble shall be a seriesof flag sequences for 1 s +/- 15%.

Flag sequence Format: 0111 1110

(in short: 1sec 0x7E)

11) preamble + (NSF)+

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11) preamble + (NSF)+(CSI) + DIS

(CSI) - Called Subscriber Identification

Optional frame (non-terminal) that provides thespecific identity of the called subscriber by itsinternational phone number

. FCF(Facsimile Control Field) format - 0000 0010

. FIF(Facsimile Information Field) length - 20 bytes

(NSF) -Non-Standard Facilities

Optional frame (non-terminal) that may be used toidentify specific user requirements which are notcovered by T.30 number

. FCF format - 0000 0100

. FIF length - min 3 bytes (the only standard portionof NSF)

DIS - Digital Identification Signal

Mandatory frame (terminal frame) thatcharacterizes the capabilities of the called terminal

. FCF format: 0000 0001

. FIF length - min 3 bytes (basic capabilities), 10

bytes defined as of 1996 (optional enhancements)Each bit or bit combination in the FIF maps over

preamble + (NSF)+(CSI) +

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preamble + (NSF)+(CSI) +DIS

Low speed signal spectral

Frame Structure of

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Frame Structure ofMessage

1sec 0x7E BCD

HDLC frame 1 HDLC frame 2 HDLC frame 3

0x7E 0x7E 0xC8/C0 FCF0xFF FIF FCS 0x7E

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Page Data Signal Spectral

Switch Back to Low Speed

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Switch Back to Low Speed(Defined on T.4)

Minimum 6 EOL on non-ECM; 2 EOL on ECM mode.

RTC (return to control

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RTC (return to controlfrom T.4)

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.Exchanged in Fax Session(non-ECM)

CallerCaller CalleeCalleeOff Hook, Dial, CNG, 0.5 s ON at 1100 Hz, 3 s OFFOff Hook, Dial, CNG, 0.5 s ON at 1100 Hz, 3 s OFF

Off Hook, CED, 3 s ON at 2100 HzOff Hook, CED, 3 s ON at 2100 Hz

DIS, at V.21 300 bps containing callee capabilitiesDIS, at V.21 300 bps containing callee capabilities

DCS, at V.21 300 bps containing the call settingsDCS, at V.21 300 bps containing the call settings

TCF, 1.5 s of 0s at the data rate selected by previous DCSTCF, 1.5 s of 0s at the data rate selected by previous DCS

FTT, at V.21 300 bps indicating TCF not properly receivedFTT, at V.21 300 bps indicating TCF not properly received

DCS, at V.21 300 bps containing the call settingsDCS, at V.21 300 bps containing the call settings

TCF, 1.5 s of 0s at the data rate selected by previous DCSTCF, 1.5 s of 0s at the data rate selected by previous DCS

CFR, at V.21 300 bps indicating that TCF was properly receivedCFR, at V.21 300 bps indicating that TCF was properly received

Facsimile Message, at the data rate selected by previous DCSFacsimile Message, at the data rate selected by previous DCS

MPS, at V.21 300 bps indicating more pages are to be sentMPS, at V.21 300 bps indicating more pages are to be sent

MCF, at V.21 300 bps, previous fax message was properly receivedMCF, at V.21 300 bps, previous fax message was properly received

Facsimile Message, at the data rate selected by previous DCSFacsimile Message, at the data rate selected by previous DCS

EOP, at V.21 300 bps indicating no more pages are to be sentEOP, at V.21 300 bps indicating no more pages are to be sent

MCF, at V.21 300 bps, previous fax message was properly receivedMCF, at V.21 300 bps, previous fax message was properly received

DCN, at V.21 300 bps indicating the and of the call, On HookDCN, at V.21 300 bps indicating the and of the call, On Hook

ToneTone

Low SpeedLow Speed

High SpeedHigh Speed

Phase APhase A

Phase BPhase B

Phase CPhase C

Phase DPhase D

Phase CPhase C

Phase DPhase D

Phase EPhase E

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Fax Session (Call Map,ECM no error )

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Fax Session(ProcedureDetail)

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Procedure understanding

CNG (-->Hello, I am the Calling fax terminal) CED (

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FCF index (useful forFAXSTAT)

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6) Review

Distinguish each signal and command

Automatic operation and

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Automatic operation andmanual operation

Call establishment can be realized

manually and/or automatically. (It is very few people in North America areusing Manual fax. Automatic fax are morepopular)

T.30 Call establishment operateing method1:

Manual mode on both end


Calling manual mode, Called auto mode


Calling auto mode, Called manual mode


Auto modemon both end T.30 Call establishment operateing method

T 30 Call establishment

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T.30 Call establishmentmethod 1

CED is optional when

called side in on manualmode (mode 1 and mode 3)

According to T.30, CNG

should always present at

least once (But I experiencesome Fax it will not send

CNG if it has detected CED

already)

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Timer

T2: (6s +/- 5s)

Time-out T2 makes use of the tight control between commands and

responses to detect the loss of command/response synchronization. T2is 6 +/- 1 seconds and begins when initiating a command search (e.g.the first entrance into the "command received" subroutine, referenceflow diagram in 5.2). T2 is reset when an HDLC flag is received or when

T2 times out.

(6s. The time the receiver fax wait for next command after previouscommand was received. Will disconnect if time out)

T3: (10s +/- 5s)

Time-out T3 defines the amount of time a terminal will attempt to alertthe local operator in response to a procedural interrupt. Failing toachieve operator intervention, the terminal will discontinue this attemptand shall issue other commands or responses. T3 is 10 +/- 5 seconds,begins on the first detection of a procedural interruptcommand/response signal (i.e. PIN/PIP or PRI-Q) and is reset when T3times out or when the operator initiates a line request.

(10s. The time wait for the operator to press a bottom or insert a paperor pick up handset)

T4 (3s +/- 15%)

Defines how long the receiver waits for HDLC command flags. 3s +/-15% for automatic units and 4.5s +/- 15% for manual units. Begins when

first entering in the Response Received routine Reset when an HDLCFlag is received or when it times out.

l

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T2, T4 Example

Receiver Fax will start T2 (6s) timer when

receive a command (and responds thecommand). Will time out after 6 sec if thecommand doesnt come. It will disconnectthe line.

Receiver Fax will start T4 (3s) timer after

send DIS to sender. Will time out andresend this message 3 times if time out.

Sender Fax will start T4 timer after sendcommand to receiver Fax. Will time out

after 3 sec if a response doesnt come. Itwill retry 3 times (except DIS) and sendDCN to disconnect the line.

T.30 assume the telephone line should at

least support low speed signal transmit and

T4 and RTN Example (non-

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T4 and RTN Example (non-ECM with error)

Sender resend MPS after T4 timeout and receiver return RTN

indication the page is not acceptable and ask go back to Phase B

T4 Example ( Re-send

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T4 Example ( Re-sendDIS )

ECM Error Correction

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ECM Error CorrectionMode

ECM is a transmission mode for fax

(receiver) to automaticly inform and (forsender)resend the corrupted page data.

Sender set bit 27 in DIS/DTC command toindicate ECM capability. Receiver set bit

27 in DCS command to confirm ECM mode. The method of ECM is to divide the page

data to 64 or 256 bytes a frame; packed asHDLC frame format(with sequence number

and FCS); combine 256 frame to a Block. Sender send one block every time.

Receiver receive and check the contain forthe transmit error. And send backinformation to sender to inform any errorframe. Sender resend error frame and

N C d f ECM

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New Command for ECM

By implementing this, some new message for ECM

was been added upon non-ECM mode:PPS: Partial Page Signal. End of Partial Page.

EOP, MPS, EOM have been replaced with PPS_EOP,PPS_MPS, PPS_EOM

PPS_NULL indicate next Partial Page contains a block for

the same page image

PPR: Partial Page Request. Request to resendsome error.

CTC: Continue To Correct. Request to repeaterror correction over 4 times.

RNR/RR: to buy time for the low end receiversto rebuild the image buffer, decompressand print the image

EOR/ERR signals to decide to drop thetransmission of the current block andmove to the next one

ECM Ch ll

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ECM Challenges

Low end machines used to print as the imagearrives

Low memory was needed

Lines were decompressed as they arrived

ECM, a whole block needs to be receivedbefore the device can start printing

Higher memory requirements

Faster processing and printing unit

Due to the error correction mechanism, onnoisy lines the call can take much longer dueto retransmissions

T (ECM d 2

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.Trace (ECM mode 2pageno error)When no error the procedure is almost same with non-ECM mode

PPR(Partial Page Request

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PPR(Partial Page Requestwhen error)

The FIF of PPR signal is 256 bits(32bytes), each bit corresponds to an FCD frame, bit=0:

received correctly, bit=1: received incorrectly or not received. This example is for a short page.

ECM Frame Error

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ECM Frame ErrorCorrection Mechanism

.A T (d fi d

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.Answer Tone(defined onV.8)

Tonal signal (sinewave) at 2100 Hz with phase

reversals at each 425 +/- 25 ms, amplitudemodulated with a sinewave of 15 +/- 0.1 Hz

.handshake proced re

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.handshake procedurethan T.30)

V.34 Handshake: Follow

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V.34 Handshake: FollowV.34 procedure

A V 34 procedure example

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A V.34 procedure example

Physically Similar to a V.34 Modem

call. But logically follow T.30procedure.

t 30 overview

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