Observations on the Wireless Internet

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Observations on the Wireless Internet

• Henning Schulzrinne
• Harvard University Wireless Internet Forum
• September 28-29, 2001

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Overview

• Internet use vs. mobile phone use
• Service models
• Architectures
• Everywhere
• Hot spots
• Data distribution

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Internet vs. mobile phone use
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Service models
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Architectures

• Everywhere
• Hot spots
• Data distribution

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Ubiquitous Mobility

• Trade-off between power, per-area bandwidth and
  number of base stations
• Licensed vs. unlicensed spectrum

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Bit density

• Most technologies about 1 b/Hz
• Another metric bits/second/km²
• Roughly, 2G/3G 2 Mb/s/km²
• 802.11b about 1 Gb/km²

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Hotspot approach

• Provide localized high-bandwidth (or,
  equivalently, cheap /bit) access
• High-speed data needs not evenly distributed
• E.g., IEEE 802.11b covers 100 m radius
• NYC 8m people in 800 km²
• 500 base station, with DSL or CATV backhaul
• 80,000 base stations for NYC? 5/person

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Unlicensed spectrum

• Subject to L1 and L3 interference
• 2.4 GHz Microwave ovens, medical, cordless
  phones
• Bluetooth wireless
• Other 802.11 networks
• Thus, no guaranteed bandwidth, even with
  reservation
• Not well suited for high-speed mobility
• High delay variability due to retransmission
• Inefficient for small packets (e.g., VoIP)
• Currently, (mostly) no power control

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Data distribution

• Backhaul often most expensive part
• For distributing static objects, only need
  sporadic Internet access
• Local maps and building/mall guides
• Tourist information
• Public transit information
• News, weather, sports

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Data distribution

• InfoStations fixed data caches at traffic
  lights, gas stations, toll boths
• 7DS mobile, cooperative data carriers

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Context-aware services

• Mobile devices have context information
• Geographic location
• Time
• Environment (inside/outside, moving, talking,
  driving, )
• Use for event notification (approaching airport
  ? reminder terminal C)

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Services

• Successful mobile services are communications-cent
  ric
• Voice communications
• SMS, pagers ? even dominates I-Mode
• Email (Blackberry, IETF 802.11)
• Typically, human-to-human, but machine-to-human
  interesting

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Services events

• Notification
• your suitcase is on its way
• your flight has changed gates
• youre approaching a traffic jam
• Control
• EZPass for humans
• Access control

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Services

• Web browsing and data access
• Some is really inconvenient communications
  (check flight status)
• How many people are willing to pay to see stock
  quotes?
• Authentication vs. m-commerce

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Services

• Distribution services
• Internet radio TV
• Bandwidth cost at least 128 kb/s for video or
  10x voice
• Competition with (satellite) radio
• Congestion-based pricing only if capacity
• Software downloads
• Precursor ring tones
• Games
• Vertical applications

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Mobility support

• Application layer network layer
• Keep external identifier constant when network
  attachment point changes

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Mobility modes
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End systems

• Classical PDA, mobile phone, laptop
• Expensive part is display and radio access, bulky
  part is keyboard
• Thus, reuse ? human-area networks

GPS
LCD
camera
RF/antenna