25-03-2011, 03:52 PM
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Telephony: history and evolution
IP Telephony: What, Why & Where?
q Adding interactive multimedia to the web
q Being able to do telephony on IP with a variety of devices
q Consumer & business markets
q Key element of convergence in carrier infrastructure
Basic IP telephony model
q Protocols: SIP, H.323, RTP, Coding schemes, Megaco
q Future: Invisible IP telephony and control of appliances
What is VoIP?
Why VoIP?
Where is VoIP Today?
What is VoIP?
q Telephony over IP standards bodies
q ITU - International Telecommunication Union
q http://itu.org
q IETF - Internet Engineering Task Force.
q http://ietf.org
q ETSI - European Telecommunications Standards Institute
q http://etsitiphon
q ANSI - American National Standards Institute
q http://ansi.org
q TIA - Telecommunications Industry Association
q http://tiaonline.org
q IEEE - Institute for Electrical and Electronics Engineers
q http://ieee.org
q Summary: Why VoIP?
Cost reduction:
q Toll by-pass
q WAN Cost Reduction
q Lowered Infrastructure Costs
Operational Improvement:
q Simplification of Routing Administration
q LAN/Campus Integration
q Policy and Directory Consolidation
Business Tool Integration:
q Voice mail, email and fax mail integration
q Mobility enabled by IP networking
q Web + Overseas Call Centers
q Collaborative applications
q New Integrated Applications
Skype: p2p VoIP over Internet
q Skype is entirely peer-to-peer and is equivalent to two H.323 terminals or 2 SIP terminals talking to each other
q Provides a namespace
q Efficient coding of voice packets
q Instant messaging with voice
q Uses Kazaa-like p2p directory + secure authentication (login server) and e2e encryption
VoIP over Wireless
q Cellular networks with 2.5G and 3G have packet services
q 1xRTT on 2.5 G
q EV-DO on 3G
q The voice on these networks is circuit switched voice…
However, …
q Combined with bluetooth or USB interfaces, a PC-based VoIP software can do VoIP anywhere there is cellular coverage.
q Or Cellphone can be a SIP terminal
q Near Future: VoIP over WiMax (802.16) and WiFi (802.11) networks
q Enterprise VoIP: Today’s networks
Toll by-pass
q Enterprise VoIP: Tomorrow’s networks
Unified/Converged Networks
History Of Telephony
q Public Telephony (PSTN) History
q 1876 invention of telephone
q 1915 first transcontinental telephone (NY–SF)
q 1920’s first automatic switches
q 1956 TAT-1 transatlantic cable (35 lines)
q 1962 digital transmission (T1)
q 1965 1ESS analog switch
q 1974 Internet packet voice
q 1977 4ESS digital switch
q 1980s Signaling System #7 (out-of-band)
q 1990s Advanced Intelligent Network (AIN)
q PSTN Evolution
q VoIP Technologies
q IP Telephony Protocols: SIP, RTP
Session Initiation Protocol - SIP
q Contact “office.com” asking for “bob”
q Locate Bob’s current phone and ring
q Bob picks up the ringing phone
Real time Transport Protocol - RTP
q Send and receive audio packets
q SIP
q SIP
q IP SIP Phones and Adaptors
q Voicemail Architecture
q Speech Coding and
Speech Coders for VoIP
q Applications of Speech Coding
q Telephony, PBX
q Wireless/Cellular Telephony
q Internet Telephony
q Speech Storage (Automated call-centers)
q High-Fidelity recordings/voice
q Speech Analysis/Synthesis
q Text-to-speech (machine generated speech)
