Transcript TR41.4-00-11-061-VONTextTelephonyGH2

TR41.4/00-11-061
VON_Text_Telephony_GH2
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Text Telephony
and Total Conversation
in the
IP revolution
Gunnar Hellström,
Omnitor AB
[email protected]
+46 8 708 204 288
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Accessibility opportunities
in IP networks
• IP networks take over telecomm traffic
• Opportunity:
– Combine text, video and voice
– Interworking between many ways to access the network
– Next generation mobile will have IP capabilities
• Important points to consider
– Interworking with Textphones in the Telephone
Network is desired.
– IP Transit for textphones requires special consideration
– A simple IP textphone is needed
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Total Conversation standards
• Text conversation need standards as well
as video and audio.
• Work is close to completion in ITU-T and IETF
to define extension of video telephony to
Total Conversation with video, text and voice
• Subsets are possible for text telephony
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Example of a Total Conversation Terminal
Voice
Text in
video
call
Sign language
Text telephony
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Opportunities with
Total Conversation
• Deaf: sign, type or lip-read as the situation calls for.
• Adult deaf: speak and see and get text back.
• Hearing impaired – Hear and lip-read as far as possible,
revert to text when needed.
• Video relay services: Transfer phone number to call
• Speech impaired: Hear and type. Or hear and speak and
revert to typing when needed.
• Anyone: Communicate in preferred mode, type when
needed for names, phone numbers etc.
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Further opportunities with local
additions to Total Conversation
• Screen reader and Braille display makes
text conversation accessible to deaf-blind
users.
• Voice recognition can make voice
conversation convenient with adult deaf
users.
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T.140, the common base for text
conversation
•
•
•
•
•
Standardised in ITU-T 1998
Extremely simple end-to-end text chat protocol
User
User input to Unicode UTF-8 coded transmission
T.140
UTF-8 transmission to display
Channel
Safe and easy to include everywhere
What is the street
address?
Alameda 34
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T.140 text protocol
• Character by character transmission
• Character code for any language:
User application
ISO 10646 (= Unicode).
• Control from ISO 6429:
T.140
Channel
Network
–
–
–
–
Erase last character,
New line,
Nelect graphic rendition
Alert in session
• Transport channel must be specified
for each environment.
Text Telephony, a subset of Total
Conversation
• IP Telephony builds on IP Multimedia
technology.
• IP Text Telephony builds on IP Total
Conversation technology
– ITU-T H.323 Annex G Text Conversation and
Text SET. IP telephone extension with text
– IETF RFC 2793 transport for text in IP
networks
– Usable in IETF multimedia protocol SIP
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TextText
in IP
networks
in IP
networks
IP Textphone or
Total Conversation
terminal
Audio
(and
Video)
T.140
Text
RTP
RTP
• H.323 Annex G = text in
the dominating IP
telephony protocol
H.323
• SIP text conversation
also possible without
further specfikation
IP Network
IP textphone
Audio
T.140
Text
RTP
RTP
Total Conversation a complete family
Ready
Ready
Ready
Text telephony H.324
T.140
Equalizers
T.120 Data
conferencing
T.140
AL1
Voice
and
video
H.245
Trans
parent
T.140
T.134
T.124
GCC
H.223
V.18
PSTN
H.320
T.140
Ready
Voice
and
video
H.224
V.34/V.80
DATA
Network
access
Ready
H.324
H.323
Mobile system
T.140
Voice
and
video
TCP/ RTP
RTP
H.221
T.123
PSTN
Ready
T.140
AL1
Voice
and
video
H.245
H.223
Network
access
ISDN
IP
Mobile
transmission
MOBILE
H.248 Annex F. Text - aware Gateway
For decision in ITU 13 Nov. 2000
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V.18 An automoding modem
- a bridge to mono media text
Can be used in gateways andExample
servers
of use
USA, UK
USA
Holland
Germany
France
Anywhere
Sweden, UK
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Text telephone interworking
• T.140 is also used in standardised text telephony.
• V.18 enables communication with a huge number
of existing text telephones
T.140
T.140 ready
transmission
in V.18 mode
T.140 equalizers
for legacy modes
V.18 text telephone modem
PSTN Interworking
• Gateways need to have V.18 capabilities, to
connect PSTN text telephone calls with Total
Conversation or IP Text Telephone terminals
• Gateways need to be T.140 aware
V.18 compatible text
PSTN
Textphone
alternating
with voice
V.18
/T.140 T.140
Gateway
T.140 text in
IP channel
RTP/Audio
H.323
Annex G
Gateway example V.18 - H.323
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Textphone gateway call between
Telephone network and IP
network
H.323 or SIP
IP textphone
IP Gateway
T.140
IP network
RTP port
V.18 port
Telephone network
Text telephone
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Textphone call in telephone
network passing through IP
network
Textphone
IP Gateway
T.140
V.18
port
RTP
port
IP Gateway
IP transit
network
Textphone
T.140
RTP
port
V.18
port
RTP-Text
Figure: IP transit network in textphone call
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IP gateway standardisation
ITU-T H.248 and IETF Megaco
• Current hot topic – huge efforts.
• Text telephone and text conversation
additions.
• Integration of text – fax – modem additions
• Possible use – same port for voice, text, fax
and modem, automatic identification of
mode and invocation of proper
packetization.
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Conclusions
• Video telephony is complemented with text to form Total
Conversation
• Text Telephony is linked in through a standardised bridge
– V.18
• Work is centered in ITU-T SG 16 with
Q9-Accessibility as initiator
• Many companies and organisation have contributed
• Standards are in place, implementations emerge
Standards support for
Total Conversation and text telephony
F.MCVS
Service
Description
Text conversation T.140
Text telephony
(PSTN)
V.18
Text, video
and voice
ISDN- H.320
H.224
Text, video and
voice (PSTN)
H.324
Data conferencing
T.120, T.134
Gateway
H.248
Text, video and
voice (IP)
H.323 Annex G
RTP-Text
Mobile text
H.324M
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