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Topology Management for Sensor Networks: Exploiting Latency and Density

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In GAF, leader election procedure uses broadcasting discovery message ... STEM is integrated with GAF in an orthogonal fashion ... – PowerPoint PPT presentation

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Title: Topology Management for Sensor Networks: Exploiting Latency and Density


1
Topology Management for Sensor NetworksExploitin
g Latency and Density
  • Curt Schurgers, Vlasios Tsiatsis,
  • Saurabh Ganeriwal, UCLA-EE
  • Mobihoc2002
  • ??? ???

2
Contents
  • Introduction
  • Sparse Topology and Energy Management
  • Theoretical Analysis
  • Setup Latency and Energy Saving
  • Combining STEM and GAF
  • Behavior of GAF
  • Performance Evaluation
  • Conclusion

3
Introduction
  • Sensor networks
  • Efficient power saving protocol
  • Topology management
  • Coordinate the sleep transitions of sensor nodes
  • Best way to save power consumption
  • Related work
  • Density dimension
  • SPIN, GAF
  • Time dimension
  • S-MAC, SMACS

4
Sparse Topology Management (1/6)
  • STEM (Sparse Topology and Energy Management)
  • Transfer state
  • Turn on the radio of sensor node
  • There is data to forward
  • Monitoring state
  • Just monitoring and turning off the radio
  • Periodically turns on radio for a short time to
    listen
  • Initiator node
  • The node that wants to communicate
  • Sends out beacons with the ID of target node
  • Target node
  • Responds to the initiator node
  • Both nodes keep their radio on during
    communication

5
Sparse Topology Management (2/6)
  • Dual frequency setup
  • In order for actual data not to interfere with
    the wakeup protocol
  • Initiator node wake up target node using radio f1
    wakeup plane
  • Both nodes turn on radio f2 data plane
  • Different frequency bands using a separate radio
  • Using one radio that switches between two
    frequencies

6
Sparse Topology Management (3/6)
  • STEM operation
  • T Time interval of periodical listen
  • TRX time of listening

7
Sparse Topology Management (4/6)
  • Minimum length of TRX
  • The worst case where the radio is turned on just
    too late to receive the first beacon
  • TRX time of listening
  • TB Beacon interval
  • B1 Beacon length

8
Sparse Topology Management (5/6)
  • Reasons of dual frequency
  • There is no interference between the wakeup and
    the transfer plane
  • One radio with one frequency
  • One radio with two frequency switching

9
Sparse Topology Management (6/6)
  • Collisions in the wakeup plane
  • A, B simultaneously wake up node C
  • C, D can detect the signal (carrier sensing)
  • Node E can receive the beacon
  • Carrier sensing node just turn on the radio
  • After time T
  • Node A, B start communication
  • Regular MAC handles collision
  • Node D turns off the data radio

10
Theoretical Analysis
  • Average Setup latency
  • Energy saving

B1 time of beacon transmission B2 time of
beacon ack. TB beacon interval TRX time of
listening T Interval of periodic listening
11
Combining STEM and GAF
  • GAF (Geographical Adaptive fidelity)
  • Leverages the network density to conserve energy,
    while leaving the data forwarding capacity
  • STEM (Sparse Topology and Energy Management)
  • Saves energy by trading it off with path setup
    latency
  • STEM and GAF are orthogonal to each other
  • Full energy gains of both techniques

12
Behavior of GAF (1/3)
  • GAF (Geographical Adaptive fidelity)
  • Virtual grid with GPS or other location
    information
  • All node in virtual grid are equivalent
  • Who will sleep and how long
  • Virtual grid
  • Divide the whole area into small virtual grid
  • For two adjacent grids A and B, all nodes in A
    can communicate with all nodes in B and vice
    versa
  • All nodes in each grid are equivalent for routing
  • Nodes exchange grid id to adjust their duty cycle
  • Grid id is determined by its location and grid
    size

13
Behavior of GAF (2/3)
r size of virtual grid R radio transmission
range
14
Behavior of GAF (3/3)
  • Three states
  • Sleeping, discovery, active

Periodically re-broadcasts its discovery message
Discovery message
Initial state
Node id Grid id Estimated node active
time (enat) Node state
15
Combining STEM and GAF
  • Hybrid scheme
  • A grid can be viewed as one virtual node
  • Virtual node runs STEM in the same way
  • Modified leader election
  • In GAF, leader election procedure uses
    broadcasting discovery message
  • If readers run STEM, they turned off data radio
  • A node that wants to be leader
  • Sets up a link to the current leader using STEM
  • Necessary information is exchanged in the data
    plane
  • Higher ranking node becomes leader
  • If a node cannot contact the any leader, it
    becomes leader

16
Performance Evaluation
  • Environment
  • Size 80m x 80m
  • Transmission range 20 m
  • Node 100 nodes
  • MAC protocol CSMA-type MAC similar to 802.11

17
Performance Evaluation (1/2)
  • E0 energy consumption without STEM
  • TS/TRX Setup latency
  • a tdata/t total time of data transmission
    (data rate)

18
Performance Evaluation (2/2)
  • ß T / TRX
  • ? node density

19
Conclusion
  • STEM
  • Topology management technique
  • Trade off power savings versus path setup latency
  • Hybrid scheme
  • STEM is integrated with GAF in an orthogonal
    fashion
  • Reduce the energy consumption to 10 or less
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