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Observations on the Wireless Internet

This document explores the evolution of wireless Internet technologies, contrasting traditional internet use with mobile phone usage. It discusses various service models, architectures, and the significance of hotspots in urban environments. Key considerations include the trade-offs between power, bandwidth, and the number of base stations, as well as the differences between licensed and unlicensed spectrum. The text also covers data distribution strategies, context-aware services, and the roles of mobility and application-layer support in enhancing user experiences in today's digital landscape.

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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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