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Wireless Networking

Wireless Networking. David Schwab And Prof. Ralph Deters. What Is Wireless Networking?. The use of infra-red or radio frequency signals to share information and resources between devices A hot computer industry buzzword: IBM Ad Series Wireless Broadband, 3G wireless, WAP, iMode, Bluetooth

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Wireless Networking

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  1. Wireless Networking David Schwab And Prof. Ralph Deters

  2. What Is Wireless Networking? • The use of infra-red or radio frequency signals to share information and resources between devices • A hot computer industry buzzword: • IBM Ad Series • Wireless Broadband, 3G wireless, WAP, iMode, Bluetooth • Mobile Internet • Ubiquitous? • Global? • Revolutionary?

  3. Features of Wireless Networks: • Hidden Node Problem • Spread Spectrum: • Frequency Hopping Spread Spectrum • Hops distinct channels within a wide frequency band • Hopping code determines channel sequence • Different hopping patterns can co-locate • Direct Sequence Spread Spectrum (DSSS) • Modulates each bit with a chipping code • Different chipping codes form separate channels • Differences: • FHSS has shorter range, lower max. speeds • DSSS has Higher cost, power, and interference

  4. Frequencies • ISM – Industrial, Scientific, Medical • Unlicensed • Worldwide • Power, time-sharing regulated (DSSS / FHSS) • Short Range Devices (SRD) • Includes: Microwaves, Cordless Phones • Ranges: • 902 – 928 MHz • 2.4 – 2.4835 GHz • 5.725 – 5.850 GHz

  5. IEEE 802.11 Fast (11B) High Power Long range Single-purpose Ethernet replacement Easily Available Apple Airport, iBook, G4 Bluetooth Slow Low Power Short range Flexible Cable replacement “Vapourware” Anoto, Test cards, phone Two 2.4GHz Standards:

  6. IEEE 802 Working Groups: • LAN / MAN Standards Group (Ethernet) • http://standards.ieee.org/wireless/ • 802.15: Wireless Personal Area Networks (WPAN) • 802.15.1 - 1Mbit/sec WPAN/Bluetooth • 802.15.2 - Coexistence in Unlicensed Bands • 802.15.3 - 20+ Mbit/sec High Rate WPAN for Multimedia • 802.15.4 - 200kbit/sec max for interactive toys, sensor • 802.16: Broadband Wireless Access Standards • Fixed, Point-to-Point • 802.11: Wireless Local Area Networks (WLAN)

  7. IEEE 802.11 Organization Tree:

  8. Disadvantages of 802.11: • Older and newer cards are incompatible • Reinforced concrete, tinted glass block signal • No standard for hand-off between base station • High power consumption in laptops • Single hop routing • Two separate modes: • “Ad Hoc” LAN • Client – Gateway

  9. Multi-Hop Ad Hoc Wireless Networking • Routing protocols used to improve wireless connections • Infrastructure-free, dynamic • True Peer-to-Peer routing • Fault tolerant

  10. DSDV • Destination Sequenced Distance Vector • Each node maintains lookup table • Neighbours periodically exchange tables • New node detection triggers table updates

  11. TORA • Temporally Ordered Routing Alogrithm • No periodic updates • Multiple paths • Node “height” used to find path • Uses sup-optimal paths

  12. DSR • Dynamic Source Routing • Path calculated at beginning of transfer • Each packet carries the entire path • Highest delivery ratio in high-speed simulations

  13. Tools • Free, Open-Source *NIX simulation tools: • Ns2 • Network Simulator, version 2 • Emulation • CMU Wireless Extensions • Ad-Hockey • Visualization tool for NS2

  14. Ad-Hockey Screenshot

  15. Bluetooth • Think USB, not Ethernet • Created by Ericsson • PAN - Personal Area Network • 1-2 Mbps connections • 1600 hops per second DHSS • Includes synchronous, asynchronous, voice connections • Piconet routing • Small, low-power, short-range, cheap, versatile radios • Usage Models: • Three-in-one Phone • Internet connection • Ultimate headset

  16. More Bluetooth • SIG: Special Interest Group • http://www.bluetooth.com • 2164 member companies • Including 3Com, Ericsson, IBM, Intel, Lucent, Microsoft, Motorola, Nokia, Toshiba, etc. • Bluetooth Specification (v1.1) • Trouble: • Not an Ethernet replacement • Incomplete specification • Incompatible implementations • Delayed products • Low demand • Predictions still optimistic

  17. Security • Wireless sniffers • IEEE 802.11: • ESSID – Extended Services Set ID • WEP – Wired Equivalent Privacy • 40 bit RC4 (RSA) encryption • “Resurrecting Duckling” paper – April 1999 • Sleep-Deprivation Attack • “Imprinting” wireless devices • Bluetooth Security • Rapid hop sequence • Short range • Encrypted transmissions

  18. Guerrilla.net • An underground alternative to the wired Internet • A grassroots movement established in 1996 • 802.11 Wireless LAN cards • Roof mounted antennae • Free software (FreeBSD) • Multi-hop routing, Internet connectivity • About $800 per node • Other networks popping up in SF, Seattle, London

  19. Future of Wireless • Better simulations + movement models • Better security • Wider selection • Lower prices • Less configuration • More end-user focus • Better software • Less visible • More popular

  20. THE END Close

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