Utilization Based Duty Cycle Tuning MAC

Protocol for Wireless Sensor Networks

Shih-Hsien Yang, Hung-Wei Tseng, Eric Hsiao-Kuang Wu, and Gen-Huey Chen

Computer Science and Information Engineering, National Taiwan University, Taipei, Taiwan, R.O.C.Computer Science and Information Engineering, National Central University, Chung-Li, Taiwan, R.O.C.

Global Telecommunications Conference, 2005. GLOBECOM '05. IEEE

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Outline Introduction Related Work U-MAC Design Simulation Conclusion

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Introduction Wireless sensor network are formed by

a great quantity of sensor nodes. Battery-powered and not recharge easily

Prolong the lifetime of the nodes is an important issue. Lowering energy consumption may result in

higher latency

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Related work-DSMAC

A

B

listen sleep listen

listensleep

listensleep listen

sleeplisten

(My queue is empty || avg delay < Dmin && duty cycle > 10%)

HalveHalve

20% 80%

10% 90%

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Related work-DSMAC

A

B

listen sleep listen

listen sleep

listensleep

listen

(0 < current energy consumption level < TE &&avg delay > Dmax && my duty cycle < 40%)

DoubleDouble

10% 90%

20% 80%

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U-MAC Design Several problems arise from the adoption of S-MAC

Uniform duty cycle Different tasks assign a fixed duty cycle

Latency:Sleep delay Idle listening after transmission

A node will keep idle listening until next frame after data transmission if ends inside the sleep period

DSMAC tunes duty cycle by doubling or halving According to delay and the emptiness of packet queue.

Source node: 0,1Sink : 3,4Intermediate node: 2

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1 4

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U-MAC Design A. Various Duty Cycle B. Utilization Based Tuning of Duty Cycle C. Selective Sleeping After Transmission

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U-MAC Design-Various Duty Cycle

Each node can be assigned different periodically listen and sleep schedules

As in S-MAC Nodes exchange schedules and synchronize

clock with their neighbors with a fixed period Nodes receiving SYNC packets will not adopt the

same schedule from their neighbors

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U-MAC Design-Utilization Based Tuning of Duty Cycle Every nodes in a sensor network have their

own different traffic loads According to what tasks they take and locations

Sending node: compute the suffered sleep delay (d) during the current transmission, and attach d in the following data packets

Receiving node: extracts d from data packet and adds d to the total sleep delay D, and refresh the packet count

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U-MAC Design-Utilization Based Tuning of Duty Cycle

Sleep delayTotal delay

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Threshold of high traffic load

Upper limitof duty cycle

Threshold of low traffic load

Lower bound of duty cycle

Average sleep delay

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U-MAC Design-Utilization Based Tuning of Duty Cycle

A’

A

listen sleep listen

listen sleep

listensleep

listen

U >Uhigh and duty cycle < DCmax

Increase n%Increase n%

10% 90%

15% 85%

listen

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U-MAC Design-Utilization Based Tuning of Duty Cycle

A’

A

listen sleep listen

listensleep

listensleep listen

sleeplisten

U <Ulow and duty cycle > DCminand D <Dmax

Decrease n%Decrease n%

20% 80%

15%85%

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U-MAC Design-Selective Sleeping After Transmission

Idle listening after transmission

Idle: waste energy

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U-MAC Design-Selective Sleeping After Transmission

Selective Sleeping When transmission is finished, a node checks if it

is at scheduled sleep time It goes to sleep if it’s at scheduled sleep time

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Simulation NS-2 Initial duty cycle: 20% Bandwidth:20kbps Data packet size:400Bytes (10Bytes for SYNC,RTS,CTS)

Transmissionpower

Receiving power

Idlepower

Sleepingpower

24.75 mW24.75 mW 13.5 mW13.5 mW 13.5 mW13.5 mW 15 15 μWW

DCmax DCmin Uhigh Ulow Dmax

40%40% 10%10% 0.30.3 0.150.15 2 seconds2 seconds

± ± n% (2%)

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SimulationTopology 1

Energy consumption Latency

UMAC w/o SS:UMAC w/o SS:Without selective sleepWithout selective sleep

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SimulationTopology 1

The duty cycle for all nodes

node2

node4

Node 1

node3

node0

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Topology 2

Simulation

Energy consumption Latency

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Conclusion U-MAC balance between energy consumption

and latency Assign proper duty cycles for nodes with different

tasks and network locations U-MAC includes several schemes

Various duty cycle Utilization based tuning of duty cycles Selective sleeping after transmission

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