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Observations on the Wireless Internet

Observations on the Wireless Internet. Henning Schulzrinne Harvard University Wireless Internet Forum September 28-29, 2001. Overview. Internet use vs. mobile phone use Service models Architectures Everywhere Hot spots Data distribution. Internet vs. mobile phone use. Service models.

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Observations on the Wireless Internet

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  1. Observations on the Wireless Internet Henning Schulzrinne Harvard University Wireless Internet Forum September 28-29, 2001

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

  3. Internet vs. mobile phone use

  4. Service models

  5. Architectures • Everywhere • Hot spots • Data distribution

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

  7. 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

  8. 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

  9. 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

  10. 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

  11. Data distribution • InfoStations: fixed data caches at traffic lights, gas stations, toll boths • 7DS: mobile, cooperative data carriers

  12. 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”)

  13. Services • Successful mobile services are communications-centric: • Voice communications • SMS, pagers  even dominates I-Mode • Email (Blackberry, IETF 802.11) • Typically, human-to-human, but machine-to-human interesting

  14. Services: events • Notification: • “your suitcase is on its way” • “your flight has changed gates” • “you’re approaching a traffic jam” • Control: • EZPass for humans • Access control

  15. 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

  16. 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

  17. Mobility support • Application layer + network layer • Keep external identifier constant when network attachment point changes

  18. Mobility modes

  19. 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

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