Dialogue Systems
Dialogue Systems
SIP
Luděk Bártek
Laboratory of Searching and Dialogue, Fakulty of Informatics, Masary
University, Brno
spring 2023
Dialogue systems
User - Dialogue System Communication Methods
Dialogue Systems
Luděk Bártek
Voice:
■ mostly communicate using telephone network PSTN, VoIP).
■ Voice digitization is performed:
■ On the user side - VoIP communication.
■ On the side of PBX - DS uses VoIP, user PSTN.
■ On the DS side - As well as user and the DS uses PSTN.
■ Speech recognition is mostly performed on the DS side.
■ When to use speech recognition on the client side?
■ What can be advantages of speech recognition on the client side?
User - Dialogue System Communication Methods
Dialogue Systems
Luděk Bártek
Text:
■ User communicates either using a specialized client or using some of the common TCP/IP protocols.
■ There is no need of speech recognition
■ Used mostly at development and debugging.
Voice+Text
■ communication to DS
■ VoIP - text using a DTMF (like writing SMS).
■ special client.
VoIP
Available Protocols
Dialogue Systems
Luděk Bártek
VoIP - family of protocols to control voice communication over Internet (IP based network).
Used in VoIP.
Used protocols:
■ UDP (ISO/OSI transport layer):
■ Transmits packets over network between two end points.
■ Does not guarantee neither packet delivery nor ordering.
■ Advantages - low data transfer costs.
■ Disadvantages - possible data lost and packet deliver speed jitter.
■ RTP (ISO/OSI session Layer):
■ Used to transmit multimedia data..
■ Guarantee data delivery..
■ Allows to define transmission parameters - guarantee the packet delivery speed.
IP Telephony
Used Protocols
Dialogue Systems
Luděk Bártek
VoIP - many implementations.
Differs in:
■ used standards
■ H.323 (not commonly used, standard ITU, complex, relatively complicated)
■ SIP (simpler H.323 replacement, commonly used in present time)
■ proprietary - Skinny (Cisco), HFA (Siemens), ...
■ offered services - telephony, TV (DVB), fax, message transmission, ...
■ signalization - depends on selected standard and used protocols.
Session Initiation Protocol (SIP)
Dialogue Systems
Luděk Bártek
VoIP signalization control protocol on application ISO/OSI layer.
Client-server text protocol offering:
■ call forwarding
■ participant identification
■ personal mobility
both parties authentication
■ conference call support using multicast.
SIP
Dialogue Systems
Luděk Bártek
Participant identification - URI in the form sip:callerJd@server-address
■ callerJd - ID assigned to the user by his PBX
■ server address - PBX address (FQDN/IP), where is the user registered.
SIP session may be:
■ direct - formed by communicating parties directly
■ using SIP proxy server(s) - serves as participants registrators.
Participant localization - using his SIP ID
Checking participant state - ready to receive call vs. busy/forwarded
Checking participant communication possibilities -available codecs, bitrates, audio/video support, ...
Connection establishing - uses the SDP protocol.
■ describes formed connection,
■ references RTP/UDP data flow used to participants communication.
SIP Session Control
Dialogue Systems
Luděk Bártek
telefon Alice
SIP proxy Atlanta
SIP proxy Biloxi
telefon Boba
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	100 OK	"--►
Zvoní Zvednul
Zavěsil
Obrázek: See Wikipedia
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