VoIP_1 - Types of Voice Calls Voice over TDM PSTN call,...

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Types of Voice Calls Voice over TDM PSTN call, 100+ years old Circuit switching High availability, constant latency Voice over Frame Relay Packet switching Large enterprise By pass toll charge Voice over ATM Multimedia transmission the promise of fully integrated voice and data service Voice over IP
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PSTN—Components Access Lines (Local Loops) Connects customer premises to the local voice switch Switches Connect access line to each other Trunks Connects voice switches to each other PBX—Private Branch Exchange Signaling—Connectionless PSTN Used for basic call set up, management, tear down and enhanced call features etc.
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Traditional Telephony - PSTN Trunk Network CO Switch CO Switch PBX Signalin g Network Voice Channel Multiplexing Residential customers Business customers Access lines
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Why VoIP ? Cost reduction Toll by-pass WAN Cost Reduction Operational Improvement Common network infrastructure Simplification of Routing Administration Business Tool Integration Voice mail, email and fax mail integration Web + call Mobility using IP New Services New Integration Applications
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Why IP ? Only single network to manage Cost savings Management Monitoring Change flexibility Runs over a variety of transports ATM Frame relay PPP (over Sonet/xDSL/…) 802.11 WLAN Ethernet Etc. ..
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Why IP ? Public standards Internet success Volume of equipment sold Application expandability video Interactive whiteboard
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Comparison Network Features PSTN Internet Switch Circuit Switched Packet Switched Connection Connection Oriented Connectionless Bit Rate Fixed and low <=64kb/s Wide variation to Gb/s Bursts Nonexistent High Error tolerance User error control Error free Info resending Can not (real time) Can be done very fast Delay Must be low and stable Can be high and vary
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Contemporary Telephony PSTN Gateway
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IP Telephony Communication Server 1000 is a server-based, full-featured IP PBX and the cornerstone of Nortel The Multimedia Communication Server 5100 is a leading unified communications solution which seamlessly integrates IP Telephony, multimedia conferencing, instant messaging
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IP Telephony Challenges I Reliability Achieved by both clustering servers and duplicating infrastructure At the end of the day, VoIP can be engineered more reliable than PSTN telephony Ease of use Migration and learning issues addressed by retaining the familiar interface (desktop telephone) while adding functionality to both the device and software on the desktop
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IP Telephony Challenges II Perceived voice quality Due to the digital nature of VoIP, quality, when riding on a well engineered network is superior to mobile telephony, very close to PSTN Public Internet not there yet, don´t confuse VoIP with Internet telephony (although they will converge) Scalability Systems must deliver scalability to thousands of subscribers on a single system
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This note was uploaded on 01/11/2011 for the course EE 5413 taught by Professor Hingcheungso during the Spring '10 term at City University of Hong Kong.

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VoIP_1 - Types of Voice Calls Voice over TDM PSTN call,...

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