9 Interworking to fixed networks

03.463GPPTechnical Realization of Facsimile Group 3 Service - non transparentTS

PSTN and ISDN only are considered, both used as transit networks to complement the PLMN in the end‑to‑end connection between facsimile group 3 terminal, figure 7/GSM 03.46.

I W F
┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
:┌────────┐┌─────────┐ :
:│Protocol││ V.21 │ :
┌─────┐ :│Control ││ ┌───────┴─┐ :
│ │ v v :│Monitor.│└─┤ V.27ter │ : ╔══════════╗2-w
╔╧═════╧╗ ╔═════════════╗╔════╗│ │╔═════════╗:│Trans- │ │ ┌───────┴─┐:───────────╢ PSTN ╟───
║ TE2 ╟──╢ Fax adaptor ╟╢ MT ╟┘ └╢ BSS/MSC ╟:│coding │ └─┤ V.29 │: ╚══════════╝
╚═══════╝ ╚═════════════╝╚════╝ ╚═════════╝:│Buffers │ │ Modem │:
/ \ :│ │ └─────────┘: ┌─────┐ ╔══════════╗
/ \ :│ │ :─┤Codec├─┼─╢ ISDN ╟───
/ \ :│L2RBOP │┌─────────────┐: └─────┘ : ╚══════════╝
/ \ :│Mapping ││Tone handling│: 3.1kHz
/ \ :└────────┘└─────────────┘: audio
┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘
:┌─────────┐ ┌────────┐:
:│ V.21 │ │Protocol│:
:│ ┌───────┴─┐ │Control │:
:└─┤ V.27ter │ │Monitor.│:
: │ ┌───────┴─┐│Trans- │:
2-w: └─┤ V.29 ││coding │:
────: │ Modem ││Buffers │:
: └─────────┘│LAPB- │:
: │Handling│:
:┌─────────────┐│L2RBOP │:
:│Tone handling││Mapping │:
:└─────────────┘└────────┘:
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘

Figure 7/03.46: Network interworking

9.1 Interworking to PSTN

As the standard access of facsimile group 3 terminals for this Teleservice is a 2‑wire 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:

‑ CCITT Recommendation V.21 synchronous mode, as standard facility for all BCS phases;

‑ CCITT Recommendation V.27ter for message speeds of 4 800 and 2 400 bit/s;

‑ CCITT Recommendation V.29 for message speeds of 9 600 and 7 200 bit/s.

The mechanism for selecting the right modem is the following:

‑ the actual message speed is obtained by detecting the DCS frame (see table 2/CCITT Recommendation T.30) while in BCS phase;

‑ 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;

‑ 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.

9.2 Interworking to ISDN

The use of 3.1 kHz audio bearer capability of ISDN allows for an interworking of PLMN very similar in practice to the scheme for PSTN, figure 7/GSM 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