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Internet Telephony (VoIP)
Overview
new Internet services: “telephone”, “radio”, “television”
why Internet telephony?
why not already?
Internet telephony modalities
components needed:
audio coding
data transport
quality of service – resource reservation
signaling
PSTN interworking: gateway location, number translation
Name confusion
Commonly used interchangeably:
Internet telephony
Voice-over-IP (VoIP)
IP telephony (IPtel)
Also: VoP (any of ATM, IP, MPLS)
Some reserve Internet telephony for transmission across the (public) Internet
Transmission of telephone services over IP-based packet switched networks
Also includes video and other media, not just voice
New Internet services
tougher: replacing dedicated electronic media vs. new modes (web, email)
distribution media (radio, TV): hard to beat one antenna tower for millions of $30 receivers
typewriter model of development
radio, TV, telephone: a (protocol) convergence?
The phone works – why bother with VoIP
Emergency Calling
911 in North America, 112 in Europe, others elsewhere
First implemented 1968 in US, now roughly 95% of US population
Basic 911 service: route emergency call to nearest emergency call center (public safety answering point – PSAP)
Later, enhanced 911 (E-9-1-1) for selective routing and conveying caller location information to PSAP
Roughly, 150 million 911 calls per year (2000)
45 million wireless
For wireless: Phase I and Phase II
Phase I conveys call back number + Pseudo-ANI (cell face identifier) to PSAP
Phase II provides caller location (e.g., via GPS or TOA)
Wireless 911 Phase II - TDOA
Wireless 911 Phase II - EOTD
Wireless 911 Phase II
Example: Sprint PCS and Nextel use GPS
Implementation just starting
VolP has similar problems as wireless:
devices change “network attachment point”