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911 services: wireline, wireless and VoIP. Prof. Henning Schulzrinne Dept. of Computer Science Columbia University, New York FCC Solutions Summit March 18, 2004. Overview. E911 for wireline E911 for wireless (Phase II) Short-term 911 service for VoIP Differences between PSTN and VoIP

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911 services wireline wireless and voip

911 services: wireline, wireless and VoIP

Prof. Henning Schulzrinne

Dept. of Computer Science

Columbia University, New York

FCC Solutions Summit

March 18, 2004

overview
Overview
  • E911 for wireline
  • E911 for wireless (Phase II)
  • Short-term 911 service for VoIP
  • Differences between PSTN and VoIP
  • Objectives
  • Internet standardization efforts
components of emergency calling
Components of emergency calling
  • Three core components that need to be replicated – everything else are implementation details
    • identifying emergency calls (“911”)
    • determining the right PSAP for current caller location
      • coarse-grained location
      • currently, ALI and MSAG
    • deliver caller location to PSAP
      • fine-grained location
e911 for wireline

Tandem Switch

(911 Selective Router)

CO Switch

E911 for wireline

PSAP #1

CAMA or PRI

delivers ANI

(555-1234)

CAMA or SS7

555-1234

313 Main St

LEC

network

555-1234

 PSAP #1

ANI: 555-1234

 313 Main

MSAG

ALI

private

data link

100-500 Main Street  ESN 1789

555-1234  PSAP #1, 313 Main St

provisioned

updates

verify address

validity

wireless 911
Phase I (April 1998)

Route all call to the appropriate PSAP based on call sector

Provide cell/sector location data to PSAP

Provide call back number to PSAP

Phase II (October 2001)

Phase I + latitude and longitude

Wireless 911
wireless 911 phase 2
Wireless 911: Phase 2

MSC

pANI

ISUP

y

N

e

t

r

s

i

l

r

i

t

LEC

selective router

Wireless Tower

PDE

MPC/SCP

E2

ALI

S

A-GPS, UTDOA, …

dynamic

updates

t

ESRK or ESRD 

coordinates

callback number

w

.

a

p

.

c

o

ESRK = unique for call

ESRD = unique for location

problems with existing 911 system
Problems with existing 911 system
  • 1970s technology:
    • CAMA trunks induce long call setup delays
    • limited in ability to transfer information (10 digits)
  • gets complicated if multiple providers
    • ILEC vs. CLEC
    • multiple wireless providers
  • tied to ILEC rate centers and other PSTN routing artifacts
  • hard to move PSAPs on short notice (e.g., emergency evacuation)
    • can’t just plug into any network termination
pstn vs internet telephony
PSTN vs. Internet Telephony

PSTN:

Signaling & Media

Signaling & Media

China

Internet

telephony:

Signaling

Signaling

Media

Australia

Belgian customer,

currently visiting US

how does voip differ from landline and wireless pstn
How does VoIP differ from landline and wireless PSTN?
  • All devices are nomadic
    • new location, but same identifier
  • Telephone companies are no longer needed
    • there are still carriers for DSL and cable “IP dial tone”
    • but unaware of type of data carried (voice, web, IM, …)
    • VSP may be in another state or country
  • Corporations and universities don’t have email carriers, either

voice service provider

(TCP, RTP, SIP)

Yahoo

ISP

(IP)

MCI

dark fiber

provider

(λ)

NYSERNET

the role of phone numbers and identifiers
The role of phone numbers and identifiers
  • Wireline  line, device, subscriber & location
  • Wireless  device, but not location
  • VoIP (phone number and URIs):
    • mostly identifies person, not device
      • multiple devices located in different states can share the same number
    • however, may not have a phone number
    • if it does, area code may be from different state than customer billing address
    • multiple devices
    • device can move, while number stays the same
    • not related to ISP
why is voip wireless
Why is VoIP ≠ wireless?
  • VoIP devices may not have phone numbers as lookup keys
  • Location information for devices is civil, not longitude/latitude
    • e.g., service address for VSPs
    • GPS not available (nor functional) on indoor devices
      • plus, accuracy of 50 m (67%) or 150 m spans many buildings…
      • no floor information
    • Cell phones don’t work in our building…
      • so A-GPS is unlikely to work there, either
  • Plus, wireless E911 complexity due to old signaling mechanism
    • expensive and complicated to connect to multiple wireless operators
    • proposals to use IP-based solutions

50m

objectives for ip based 911
Objectives for IP-based 911
  • International
    • devices must work anywhere
    • independent of local emergency number
  • Multimedia
    • Integrate alternate modalities such as text (TDD) and video (sign language)
  • COTS
    • avoid repeat of CAMA trunks
  • Resilient
    • easily re-route calls to any number of backup PSAPs
  • Testable
    • users can test operation without tying up operator resources
  • Secure
    • integrity, confidentiality, protection against denial-of-service attacks
  • Technology-independent
    • do not depend on (e.g.,) specific wireless or link technology
  • Pro-competitive
    • does not require carriers or gatekeepers
voip and 911 two stages
VoIP and 911 – Two stages
  • Short term:
    • work with existing PSAPs
    • may not support nomadic devices
  • Longer term:
    • upgrades in PSAP CPE
    • opportunity for improved overall architecture
    • support nomadic devices
    • support multimedia
    • provide framework for simpler & cheaper circuit-switched landline and wireless architecture
short term solutions
Short-term solutions
  • Emulate wireline
    • every subscriber has phone number
    • capture VoIP subscriber address and enter into ALI DB
    • gateway calls 10-digit number and provides ANI
  • Emulate wireless
    • VoIP provider = another wireless carrier
    • use similar dynamic updates for ALI DB
ietf standardization efforts
IETF standardization efforts
  • IETF = Internet Engineering Task Force = international open standardization body

“911”

sip:[email protected]

include

civil and/or geo

911  sos

112  sos

sip:[email protected]

provide location (civil or geo)

DHCP

cn=us, a1=nj, a2=bergen

conclusion
Conclusion
  • Existing 911 system closely tied to PSTN history
    • number as universal identifier
    • close affiliation with PSTN switches
    • incremental, constrained evolution
  • VoIP offers opportunity to increase robustness and decrease costs
  • Initial international standardization efforts in progress
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