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Wireless Ad Hoc/Sensor Networks

Wireless Ad Hoc/Sensor Networks. Ten-Hwang Lai Ohio State University. Outline. Wireless LANs Ad Hoc Networks IEEE 802.11 Bluetooth Berkeley Motes Smart Dust. Wireless LANs. IEEE 802.11 Bluetooth HiperLan (Europe). History of IEEE 802.11. 802.11 standard first ratified in 1997

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Wireless Ad Hoc/Sensor Networks

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  1. Wireless Ad Hoc/Sensor Networks Ten-Hwang Lai Ohio State University

  2. Outline Wireless LANs Ad Hoc Networks IEEE 802.11 Bluetooth Berkeley Motes Smart Dust

  3. Wireless LANs IEEE 802.11 Bluetooth HiperLan (Europe)

  4. History of IEEE 802.11 • 802.11 standard first ratified in 1997 • 802.3 LAN emulation • 1 & 2 Mbps in the 2.4 GHz band • Two high rate PHY’s ratified in 1999 • 802.11a: 6 to 54 Mbps in the 5 GHz band • 802.11b: 5.5 and 11 Mbps in the 2.4 GHz band

  5. The Beat Goes On • 802.11c: support for 802.11 frames • 802.11d: new support for 802.11 frames • 802.11e: QoS enhancement in MAC • 802.11f: Inter Access Point Protocol • 802.11g: 2.4 GHz extension to 22 Mbps • 802.11h: channel selection and power control • 802.11i: security enhancement in MAC • 802.11j: 5 GHz globalization

  6. 802.11 BSS Basic Service Set (BSS) --- a basic LAN Infrastructure BSS Independent BSS (Ad Hoc LAN) Access point

  7. 802.11 ESS Extended Service Set (ESS) Distributed System

  8. Bluetooth Piconet & Scatternet Master Master Slaves Slaves S M Piconet Master Slaves Scatternet

  9. Comparison of Bluetooth to 802.11b Bluetooth 802.11b Bandwidth 1 Mbps 11 Mbps Range 10 meters 100 meters Profiles Almost unlimited AP, STA Current consumption 60mA 300mA Cable replacement Serial, USB, Audio 802.3 Circuit cost (9/2001) $11.00 $46.00 Ad hoc networking multi-hop single-hop

  10. Bluetooth or 802.11? Why do we need MAC?

  11. Can Bluetooth Compete with 802.11? • IEEE 802.11 already has been widely accepted. • What are Bluetooth’s chances of success stacking against 802.11? Answer: ? 802.11 --- WLAN Bluetooth-- WPAN

  12. Ad Hoc Networking • BT Scatternet --- multihop? • 802.11 --- single hop? Master Slaves S M Master Slaves

  13. BT Scatternet Formation • Problem: design a protocol that given a set of bluetooth nodes organizes the nodes into a scatternet. • Still an interesting research problem.

  14. A Sensor Node Memory (Application) Processor Network Interface Actuator Sensor

  15. Berkeley Mote: a sensor device prototype • Atmel ATMEGA103 • 4 Mhz 8-bit CPU • 128KB Instruction Memory • 4KB RAM • RFM TR1000 radio • 50 kb/s • Network programming • 51-pin connector

  16. Berkeley DOT Mote • Atmel AVR 8535 • 4MHz • 8KB of Memory • 0.5KB of RAM • Low power radio • Power consumption • Active 5mA • Standby 5μA

  17. Tightly-Coupled Sensor Array

  18. Artificial Retina

  19. Smart Clothing & Wearable Computing • Smart Underwear • Smart Eyeglasses • Smart Shoes • …

  20. Berkeley Smart Dust • bi-directional communications • sensor: acceleration and ambient light • 11.7 mm3 total circumscribed volume • 4.8 mm3 total displaced volume

  21. Speckled Computing • 愛丁堡大學（University of Edinburgh）科學家即將研發出大小跟灰塵差不多的超微型晶片, 這些晶片可以分散或噴灑到物體上彼此溝通、傳遞資訊。 這種名為斑點運算（speckled computing）的技術可望在三年內成為事實。 • 將晶片噴到患者的衣物上, 可監控其心跳 、呼吸與體溫。 • Source: Silicon Glen R&D Update, April, 2003  

  22. What need to be done? • Interdisciplinary • A few sample problems

  23. Sensor Deployment • How to deploy sensors over a field? • Planned deployment • Random deployment + improvement • What are desired properties of a “good” deployment?

  24. Coverage, Connectivity, Density • Every point is covered by a sensor • The network is connected • No area is too dense

  25. Unreliable Sensor Grid: Coverage and Connectivity • INFOCOM 2003 • Active • Dead • Be dead with a prob p • transmission and sense range r • A necessary and sufficient condition for the network to remain covered and connected N nodes

  26. Connected Sensor Coverage • Mobihoc’03 • Given a sensor network • Given a query • Find a smallest connected subset of sensors that can serve the query.

  27. Localization from Mere Connectivity • Mobihoc’03 • Find geographic positions of sensors • Not using GPS • But using only connectivity information of the net + a few nodes with known positions.

  28. Reliable Transport • Mobihoc’03 • What is reliable transport in sensor networks? Data center event

  29. Energy Efficiency • Done at every level from physical to application. • Energy-efficient routing. • Energy-efficient MAC. • Energy-efficient everything.

  30. S-MAC: an energy-efficient MAC • In IEEE INFOCOM 2002, • By Ye, Heidemann, Estrin • IEEE 802.11-like • RTS/CTS/Data/Ack • Go to sleep on hearing a RTS or CTS

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