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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

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
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 …
neighborhood contention

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

and low duty cycle

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

related work
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]
flash overview
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
outline
Outline
  • Experiment Methodology
  • Design of Flash
  • Performance evaluation
  • Conclusions
evaluation methodology
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
flash i complete concurrency

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

flash i flooding example

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

flash ii maintained concurrency
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
flash ii flooding example

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

flash ii flooding example13

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

flash iii controlled concurrency

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

flash iii flooding example

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

conclusions
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.
cases where capture helps
cases where capture helps

E

Got B!

I

Got D!

B

Got D!

D

A

F

C

H

G

cases where collision happens
cases where collision happens

E

I

B

Got D!

D

A

F

???

Got B!

???

Got A!

C

H

G