Overcoming the Challenges of Wireless in the Classroom

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Overcoming the Challenges of Wireless in the
Classroom

• Patrick Bristow
• Software Engineer, ConferenceXP
• External Research Programs, Microsoft Research
• Thursday, July 21th, 2005
• Tablet PC Workshop

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Outline

• What is multicast?
• Why use multicast over wireless?
• Great! Whats the problem?
• So what do we do?

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What Is Multicast?

• Multicast is a type of traffic destined to a
  group of users (one-to-many type of traffic)

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If Multicast Is Not Used
source
The Source cant afford the bandwidth!
The same traffic is going over one link multiple
times.
Thank you Sauleh Eetemadi for the animations!
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IP Multicast
source
Was born with WWW in early 90s, butdeployment
is far behind expectation!
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Unicast Over Wireless
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Multicast Over Wireless
Wireless is already multicast
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Multicast and Unicast Throughput over 802.11b
7.9 Mbps
460 Kbps
Data source Performance of Reliable Transport
Protocol over IEEE 802.11 Wireless LAN
Analysis and Enhancement Haitao Wu,
et al IEEE InfoCom 2002
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Unicast It Gets Worse

• Wireless MAC contention
• The x factor TCP contention
• Wireless signal strength
• Competing signals / uses

Result? It usually takes an act of God to get
20 laptops in the same room to have usable
wireless.
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Multicast Is My New Best Friend?

• Multicast doesnt guarantee reception
• Data loss is bursty
• (Ink packets are lost when slides arent)
• Hardware problems
• Intel Centrino issue / PSP
• Latest firmware for AP important
• Unusual problems seen on g networks

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ConferenceXP

• Research platform / RDK
• Free download for non-commercial use
• Shared Source
• Two-part strategy
• High-quality A/V conferencing
• In-class learning technology platform
• No perfect solution
• General upward trend technology is still early
• Early adopter Classroom Presenter

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Looking Forward

• Reliable multicast (Wenjun Zeng)
• CXP 4.0
• New wifi technologies
• Share your experiences
• http//www.conferencexp.net/
• Message Boards
• e-Mail Distribution Lists
• Soon to come Wiki!