TR-30/02-01-009
UIT - Secteur de la normalisation des télécommunications
ITU - Telecommunication Standardization Sector
UIT - Sector de Normalización de las Telecomunicaciones
Study Period 2001-2004
Commission d' études 

Study Group
 16
Comisión de Estudio 

Contributi on tardive 

Delayed Contributi on  D.___ (WP 1/16)
Contribuci ón tardía 

Geneva, 5 – 15 February, 2002
Texte disponible seulement en 

Text available only in
 E
Texto disponible solamente en 

Question(s): Q11/16
SOURCE:
Conexant Systems Inc.
TITLE:
Universal Modem Relay Gateways: Definition and Call Flow
___________________
Abstract
This document defines the capabilities of a universal gateway and provides several call flow diagrams that
illustrate recommended practices.
* Contact:
Michael Beadle
Conexant Systems
Tel:
+1 949 579 4940
FAX:
+1 949 579 3667
E-mail:
[email protected]
Attention: This is not an ITU publication made available to the public, but an internal ITU Document intended only for use by the
Member States of the ITU and by its Sector Members and their respective staff and collaborators in their ITU related work. It shall
not be made available to, and used by, any other persons or entities without the prior written consent of the ITU.
1.
Introduction
V.MoIP has classified gateways into two categories, either V.8 or Universal, based on their
demodulation/re-modulation capabilities. This paper provides a formal definition of the
universal gateway in terms of the gateways demodulation/re-modulation feature requirements.
Call flow diagrams illustrating the call flow procedure used by universal gateways are also
provided. These charts are an extension of compatible call flow charts shown in D.___.
2.
Universal Gateway Definition
A Universal gateway is a gateway that shall:
 At a minimum be capable of demodulation/re-modulation for the following modulations:
V92, V.90, V34, V.32bis, V.32, V.22bis, V.22, V.23 and V.21.
 For the Universal-to-Universal connection scenario, detection of any of these
modulations will result in the universal gateways transitioning to MR mode.
3.
Universal Gateway Call Flow Procedures
The capabilities of each gateway are identified at call setup time through external signaling
techniques. The gateway can be either a V.8 or Universal type gateway. The call flow
procedures described within this document are limited to the cases where both gateways are the
Universal type since the other combinations have been addressed in other documents.
Universal gateways are designed to maximize the use of demodulation/re-modulation techniques
for modem over IP networks. The standard Remote Access Server modem modulations are all
terminated locally.
During the period beginning with the detection of answer tone and ending with a decision on the
appropriate mode of operation IP packets may be discarded. Discarding these packets improves
reliability by allowing the gateway to completely control the transition from voice to modem
relay mode.
Either gateway may request a change to Modem Relay. This request is initiated when the
gateway has determined that the modulation being used can be terminated successfully by the
gateway. Gateways receiving a request to switch to Modem Relay mode must accept the
request.
Optionally if a Universal Gateway Modem recognizes that it can not terminate a particular
modem modulation it may choose to either send a SSE-Voice or SSE-VBD.
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4.
Diagrams
M1
G1 (Universal)
M2
G2 (Universal)
Capabilities Negotiation
ANS
CALL SETUP
PHASE
(1) ANS detection
<50 ms
leakage
ANS verification
(TBD ms).
ANS is blocked
during this
period.
(3) ANS RFC-2833
ANS
(2) ANS tone detected
(4) Regenerate ANS.
VOIP
PHASE
Voice data
packets to
G2 may
be blocked
ANS
(6) Change State to MR
(5) SSE: MR
(4) V.22 USc. 1's 2250Hz
Detected.
State Change to MR
V.22
USc. 1's
2250Hz
Sc. 1's
MODEM RELAY
PHASE
Figure 1: V.22 modem calling V.22 modem
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M1
G1 (Universal)
M2
G2 (Universal)
Capabilities Negotiation
ANS
CALL SETUP
PHASE
(1) ANS detection
<50 ms
leakage
ANS verification
(TBD ms).
ANS is blocked
during this
period.
(3) ANS RFC-2833
ANS
(2) ANS tone detected
(4) Regenerate ANS.
VOIP
PHASE
Voice data
packets to
G2 may
be blocked
ANS
(6) Change State to MR
(5) SSE: MR
(4) V.23 1300Hz tone
Detected.
State Change to MR
V.23
1300Hz
390Hz
MODEM RELAY
PHASE
Figure 2 Universal: V23 modem calling V.23 modem
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M1
G1 (Universal)
M2
G2 (Universal)
Capabilities Negotiation
ANS
CALL SETUP
PHASE
(1) ANS detection
<50 ms
leakage
ANS verification
(TBD ms).
ANS is blocked
during this
period.
(3) ANS RFC-2833
ANS
(2) ANS tone detected
(4) Regenerate ANS.
VOIP
PHASE
Voice data
packets to
G2 may
be blocked
ANS
(6) Change State to MR
(5) SSE: MR
(4) V.21 1650Hz
Mark Detected.
State Change to MR
1650Hz
Mark
980Hz
Mark
MODEM RELAY
PHASE
Figure 3: V21 modem calling V.21 modem
5.
Summary
Universal gateways use demodulation/re-modulation to terminate the standard V-series modem
modulations. The call flow procedures are very simple and reliable. It is recommended that the
definitions and procedures described within this draft be adopted into the V.MoIP standard.
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