electionel ecti on election: energy-efficient and low- latency scheduling technique for wireless...
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ELECTIONELECTION: EEnergy-efficient and LLow-latEEncy sCCheduling TTechnique for wIIreless sensOOr NNetworks
Shamim Begum, Shao-Cheng Wang, Bhaskar Krishnamachari, and Ahmed Helmy
Department of Electrical Engineering-Systems,
University of Southern California
IEEE Local Computer Networks (LCN’04)
Outline
Introduction Proposed Protocol Simulation Results Conclusion and Future Work
Introduction
Research challenge Energy efficiency
Energy efficient protocols MAC, topology control, data aggregation, etc
Main concern Design of sleep scheduling scheme
Introduction
Performance metrics Energy efficiency Latency Responsiveness
The difference between reported data value and the data threshold
Focuses in different scenarios Normal operation: energy efficiency Abnormalities happed: low latency or high
responsiveness
Introduction
Motivation Dynamic requirements of different metrics
Main idea Spatial-temporal correlation
Spatial: At any point of time, all sensors in a small area in the sensor field measure the same phenomenon
Temporal: When some abnormal reaction causes the phenomenon, all sensors read this increasing phenomenon and perceive the increase
Protocol --- Network Model and Assumptions
Sensor field
Reaction area
assumption• both communication radio and the
sensor can be turned off independently
to save energy• threshold tolerance is specified
model
Protocol --- Timing Diagram
Phase 0: Synchronization --- using existing synchronization schemes
Phase 1: Periodic sleep and monitor
Phase 2: CH formation, data aggregation, and report
Protocol --- State Transition Diagram
Protocol --- Phase 2
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• Initial (Dth) = 30)
Protocol --- Phase 2
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• Neighborhood advertisement message exchange
Protocol --- Phase 2
• Cluster head election
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Protocol --- Phase 2
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• Cluster head advertisement message broadcast
Protocol --- Phase 2
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• Cluster membership message reply
Message from node X has higher signal strength
Protocol --- Phase 2
• Cluster formation
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Protocol --- Phase 2
• TDMA schedule creation in cluster heads
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Protocol --- Phase 2
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• TDMA schedule announcement
Protocol --- Phase 2
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• Data aggregation and data transmission
?Does the cluster always directly transmit data packets to its nearby base station ?
Sleep Cycle Adaptation
ELECTION vs. other protocols ELECTION turns sensors off during sleep
Sleep cycle reduction function Fsr is a function of current sleep cycle and gradient of the environment
s(t): sleep cycle duration at time t g(t): gradient at time t s(t+1)=Fsr(s(t), g(t))
Exponential Fsr
• Good for latency• Aggressive sleep cycle reduction causes small sleep cycle
energy expensive
Geared Fsr
Simulation Results --- Compared Approaches
TEEN [12] Nodes sleep periodically instead of staying awake During sleep
Nodes turn their communication radios off leaving the sensors on
Nodes sense the environment continuously and wake up only when the event threshold is detected
Hybrid Mix of TEEN and ELECTION Fixed sleep cycle, on-demand cluster formation
Simulation Results --- Parameters and Phenomenon
Parameters
Phenomena P1: Changes 100 times during the entire simulation P2: Changes 20 times during the entire simulation
Simulation Results --- Remaining Energy (P1)
Major energy costs are sensing and cluster formation
Save energy of cluster formation, but waste energy for continuous sensing
Simulation Results --- Remaining Energy (P2)
Sleep duration become large (Change slower than P1), significant energy saving
Fixed sleep duration no significant energy saving
Simulation Results --- Number of Alive Nodes
Simulation Results --- Delay
• Hybrid/TEEN: fixed sleep cycle (delay 25 sec)• ELECTION: depends on the sensing phenomenon
Simulation Results --- Responsiveness
Conclusion and Future Work
Proposed ELECTION scheme Consider the spatial-temporal correlation of underlying
physical phenomenon Three phases Perform well in comparison with TEEN and hybrid
protocol Future work
Hierarchical organization of cluster heads Load balance