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Flash Flooding: Exploiting the Capture Effect for Rapid Flooding in Wireless Sensor Networks

Flash Flooding: Exploiting the Capture Effect for Rapid Flooding in Wireless Sensor Networks. Jiakang Lu and Kamin Whitehouse Department of Computer Science University of Virginia. Infocom ’ 09 Rio de Janeiro, Brazil. Classic WSN Algorithms.

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Flash Flooding: Exploiting the Capture Effect for Rapid Flooding in Wireless Sensor Networks

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  1. Flash Flooding: Exploiting the Capture Effect for Rapid Flooding in Wireless Sensor Networks Jiakang Lu and Kamin Whitehouse Department of Computer Science University of Virginia Infocom’09 Rio de Janeiro, Brazil

  2. Classic WSN Algorithms • Network floods are common and important operations at the heart of most wireless sensor network algorithms. • Routing tree creation • Time synchronization • Code and data dissemination • Node localization • Group formation • However, network floods are costly in latency due to …

  3. CCA+MAC Delay Tx A B B D A C C D …neighborhood contention E F B Rx Tx D A G Rx Tx Rx Tx C H I

  4. Minimal Interpacket Spacing A B C D … and low-duty cycle E Wake Up Tx Tx Tx Tx Tx F Sleep B … Rx D A G … Rx … Tx Rx Tx C H I

  5. Related Work • Low-duty cycle CSMA networks • High latency of an LPL flood • [Polastre 2004], [Buettner 2006] • Wireless senor networks flooding • Do not explicitly optimize for latency • [Heinzelman 1999], [Levis 2002], [Hui 2004] • Real-time communication protocols • Point-to-Point, multicast or data collection • [He 2003], [Watteyne 2006] • Rapid wakeup scheduling • Requires phase synchronization • [Lu 2004], [Li 2005], [Lu 2005], [Keshavarzian 2006]

  6. Flash Overview • The Flash flooding protocol exploits the capture effect to reduce flooding latency by eliminating neighborhood contention • Capture: a radio successfully demodulates one of multiple overlapping transmissions of the same frequency • Allow nodes to propagate the message concurrently in a flooding scenario • Propose three flooding-specific mechanisms to manage transmission concurrency

  7. Outline • Experiment Methodology • Design of Flash • Performance evaluation • Conclusions

  8. Evaluation Methodology • VineLab testbed • 48 Tmote-skys • Office environment • Trace-based Simulation • Capture-aware simulation framework • Multiple Scales and densities • Statistically verified with the testbed results

  9. Tx Tx Tx Tx Tx Tx Tx Flash-I: Complete Concurrency • Carrier sense is completely removed before transmission • No neighborhood contention • Tradeoff • Significantly reduce the flooding latency • High network coverage is not guaranteed X-MAC packet train Flash-I packet train

  10. Minimal Interpacket Spacing A B B D A C C D Flash-I flooding example E Tx Tx Tx Tx Tx F B Tx Tx Tx Rx Tx D A G Tx Tx Rx … Tx C H I

  11. Flash-II: Maintained Concurrency • Flash-II achieves low flooding latency while improving the coverage of Flash-I • Each node has two phases of flooding: 1) Flash-I flood • With no CCA or MAC delay 2) Neighborhood rebroadcast • With CCA and MAC delay (X-MAC flood) • Reach any nodes that missed the first wave

  12. A B B D A C C D Flash-II flooding example E CCA and MAC delay before local rebroadcast Phase #1 = Flash-I flood Tx Tx Tx Tx Tx … F B Tx … Tx Tx Rx Tx D A G Tx Tx Rx … Tx C H I

  13. A B B D A C C D Flash-II flooding example E Phase #2 = Local rebroadcast w/ CCA and MAC dealy Tx Tx Tx Tx Tx … F B … … D A G Tx Tx … … … Rx Tx Tx Tx C H I

  14. 75% Flash-II Scale Simulation

  15. 70% Flash-II Density Simulation

  16. Tx Tx Tx Tx Tx Tx Tx Tx Tx Tx Tx Tx Tx Tx Flash-III: Controlled Concurrency • A fine balance must be achieved to exploit the capture in a flood • Flash-III applies a new technique to sense the amount of transmission concurrency • a small interpacket spacing (IPS) • a small CCA before the packet train X-MAC packet train Flash-III packet train

  17. A B B D A C C D Flash-III flooding example E Tx Tx Tx Tx Tx F B Rx Tx Tx Tx Tx Tx D A G … Rx Tx Tx Tx Tx … Rx C H I

  18. 75% Flash-III Scale Simulation

  19. 80% Flash-III Density Simulation

  20. Conclusions • Flash is the first network flooding protocol for wireless networks that explicitly exploits the capture effect to optimize for latency. • The simplicity of Flash can bring substantial performance improvement in the existing systems and have an immediate and practical impact. • The empirical study of network-wide capture dynamics and the novel capture-aware simulation framework will inspire new studies on capture in the future.

  21. Thank you

  22. Backup slides

  23. cases where capture helps E Got B! I Got D! B Got D! D A F C H G

  24. cases where collision happens E I B Got D! D A F ??? Got B! ??? Got A! C H G

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