VoIP%20over%20Wireless%20LANs

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VoIP over Wireless LANs

• Sangho Shin

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Why VoIP?
Service
Voice
Voice
IP
IP
Personalized Service Location-based
Service Emergency Service
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Why 802.11?

• Unlicensed Channels
• Easy to install
• High speed
• Widely Deployed

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Why 802.11?
a
y
b
w
e
v
f
IEEE 802.11 Standards
u
g
i
T
k
s
m
r
n
p
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VoIP over 802.11 WLANs
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Quality of Service ?

• Handoff

• Capacity
• Limited bandwidth
• Low utilization of VoIP traffic

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SIP Client in PDA
SIP Session Initiation Protocol (RFC 3261)
SIP
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SIP Client in PDA
Prototype
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SIP Client in PDA
Final product
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Handoff
Layer 2 (MAC layer) Handoff
Handoff Time 500 ms 1 s
4 ms 100 ms
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Selective Scanning Caching
2004 Product of the Year Award INTERNET
TELEPHONY magazine (www.itmag.com)
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Handoff

• Selective Scanning
• Caching
• Locality
• Store the scanned AP information to a cache

802.11b channels
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Handoff
Layer 3 (IP layer) Handoff
Handoff Time 1 min
20 ms 300 ms
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Handoff

• Fast L3 Handoff (Client side)
• Scan unused IPs in a new subnet
• Passive DAD (Server side)

160.123.234.31 160.123.231.32 160.123.235.35 160.1
23.232.36 160.123.238.38
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Capacity
More simultaneous calls need to be supported
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Capacity
VoIP Capacity 2530
DPCF IEEE WCNC05
APC ACM QSHINE06
PCF
DCF
802.11 MAC
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Call Admission Control
QP-CAT
Better Prediction Higher Utilization
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Experiments
NJ Rutgers University
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Experiments

• Capacity for VoIP traffic in IEEE 802.11 WLANs
• APC
• DPCF
• QP-CAT

IEEE INFOCOM07
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Applicability

• Voice Audio Video

IEEE 802.11
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Applicability

• Voice Audio Video

IEEE 802.11
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Thank you !
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Why Voice over IP ?

• Personalized service
• Location based service
• Ring sound is turned off Automatically in a
  theater
• When you arrive at home, all calls to you are
  forwarded to home.

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Why 802.11

• 802.11
• CSMA/CD
• Unlicensed channel
• Shared by many users
• High Speed
• 802.11a/g 54 Mb/s
• 802.11n (MIMO) 100Mb/s 500Mb/s
• Easy installation
• Cheap

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BOSS
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