VoIP over Wireless LANs

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VoIP over Wireless LANs

• Sangho Shin

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Outline
Why VoIP ?
Why 802.11 ?
My research
Applicability
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Why VoIP?
Voice
Service
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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VoIP over 802.11 WLANs
AP (Access Point)
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My Research

• Quality of Service
• for VoIP in 802.11 WLANs

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VoIP (SIP) Client in PDA
SIP Session Initiation Protocol (RFC 3261)
SIP
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VoIP Client in PDA
Prototype
ARM chip Linux
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VoIP Client in PDA
Final product
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Handoff
Layer 2 (MAC layer) Handoff
Handoff Time 500 ms 1 s
Selective Scanning Caching
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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Layer 2 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
Fast L3 Handoff
Passive DAD
20 ms 300 ms
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Layer 3 Handoff

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

Monitor
Collect IPs
Update IP list
Fast Response
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
Low VoIP capacity in WLANs
Low bandwidth
Low utilization of VoIP traffic
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Capacity
VoIP Capacity 2530
DPCF
APC
Fair resource distribution
Reduce polling overhead
PCF
DCF
802.11 MAC
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Call Admission Control (CAC)
QoS
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Call Admission Control (CAC)
QoS
CAC
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Call Admission Control (CAC)


90
80
QoS
Utilization
CAC
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Call Admission Control (CAC)

100
98

90
80
QoS
Utilization
QoS
Utilization
CAC with QP-CAT
CAC
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QP-CAT ?
Delay
QoS
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Experiments
NJ Rutgers University
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Experiments

• Capacity for VoIP traffic in 802.11 WLANs

DPCF
APC
QP-CAT
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Applicability
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Applicability
802.11 WLAN
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Thank you !
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Applicability
802.11
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Applicability

• Voice Audio Video

IEEE 802.11
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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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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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