1 tr41.4/00-11-061 von_text_telephony_gh2. 2 text telephony and total conversation in the ip...
TRANSCRIPT
1
TR41.4/00-11-061VON_Text_Telephony_GH2
2
Text Telephony and Total Conversation
in the IP revolution
Gunnar Hellström, Omnitor AB
[email protected]+46 8 708 204 288
3
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
4
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
5
Example of a Total Conversation Terminal
Voice
Text in videocall
Sign language
Text telephony
6
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.
7
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.
8
T.140, the common base for text conversation
• Standardised in ITU-T 1998• Extremely simple end-to-end text chat protocol• User input to Unicode UTF-8 coded transmission• UTF-8 transmission to display• Safe and easy to include everywhere
What is the street address? Alameda 34
User
T.140
Channel
T.140 text protocol• Character by character transmission• Character code for any language:
ISO 10646 (= Unicode). • Control from ISO 6429:
– Erase last character,
– New line,
– Nelect graphic rendition
– Alert in session
• Transport channel must be specified for each environment.
T.140
Channel
User application
Network
10
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
Text in IP networks
• H.323 Annex G = text in the dominating IP telephony protocol H.323
• SIP text conversation also possible without further specfikation
IP Textphone orTotal Conversation
terminal IP textphone
T.140Text
RTP
T.140Text
RTP
Text in IP networks
Audio
RTP
Audio(and
Video)
RTP
IP Network
12
Total Conversation -a complete family
V.18
Text telephony
Transparent
Equal-izers
T.140
PSTN
H.223
V.34/V.80
AL1 H.245
H.324
T.140Voice
andvideo
PSTN
H.221
Networkaccess
H.320
H.224
T.140Voice
andvideo
ISDN
H.323
Networkaccess
T.140Voice
andvideo
IP
H.324Mobile system
H.223
Mobiletransmission
Voiceand
video
AL1 H.245
T.140
MOBILE
T.124GCC
T.134
T.120 Dataconferencing
T.123
T.140
H.248 Annex F. Text - aware Gateway For decision in ITU 13 Nov. 2000
Ready Ready Ready Ready Ready Ready
RTP
DATA
TCP/ RTP
13
V.18 An automoding modem - a bridge to mono media text
Can be used in gateways and servers
USA, UKUSAHollandGermanyFranceAnywhereSweden, UK
Example of use
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 equalizers for legacy modes
T.140 ready transmission in V.18 mode
T.140
V.18 text telephone modem
15
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
PSTNTextphone
Gateway H.323Annex G
T.140 text in IP channel
RTP/Audio
Gateway example V.18 - H.323
V.18 compa-tible text V.18
/T.140 T.140
alternatingwith voice
16
Textphone gateway call between Telephone network and IP
network
IP network Telephone network
IP Gateway
Text telephone
V.18 port RTP port
T.140
H.323 or SIP IP textphone
17
Textphone call in telephone network passing through IP
network
IP transit network
IP Gateway
V.18 port
RTP port
T.140
IP Gateway
V.18 port
RTP port
T.140
RTP-Text
Textphone Text-phone
Figure: IP transit network in textphone call
18
IP gateway standardisationITU-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.
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
20
Standards support for Total Conversation and text telephony
F.MCVS Service Description
Text telephony (PSTN)
V.18
Text, video and voice
ISDN- H.320H.224
Text, video and voice (IP)
H.323 Annex GRTP-Text
Text, video and voice (PSTN)
H.324
Mobile textH.324M
GatewayH.248
Text conversation T.140
Data conferencingT.120, T.134