a wakeup scheme for sensor networks: achieving balance between energy saving and end-to-end delay...

A Wakeup Scheme for A Wakeup Scheme for Sensor Networks: Sensor Networks: Achieving Balance Achieving Balance

between Energy Saving between Energy Saving and End-to-end Delayand End-to-end DelayXue Yang, Nitin H.VaidyaXue Yang, Nitin H.VaidyaDepartment of Electrical and Computer Engineering, and CoordinDepartment of Electrical and Computer Engineering, and Coordin

ated Science Laboratoryated Science LaboratoryUniversity of Illinois at Urbana-ChampaignUniversity of Illinois at Urbana-Champaign

IEEE Real-Time and Embedded Technology and ApplicatioIEEE Real-Time and Embedded Technology and Applications Symposium (RTAS 2004)ns Symposium (RTAS 2004)Speaker: Hao-Chun SunSpeaker: Hao-Chun Sun

OutlineOutline

IntroductionIntroductionRelated WorkRelated WorkPipelined Tone Wakeup Scheme Pipelined Tone Wakeup Scheme

(PTW)(PTW)Analysis for Energy ConsumptionAnalysis for Energy ConsumptionPerformance EvaluationPerformance EvaluationConclusionConclusion

IntroductionIntroduction

Wireless Sensor NetworkWireless Sensor Network Application scenarios—Application scenarios—

Intrusion detectionIntrusion detectionDisaster alarmingDisaster alarming

The communication is typically driven by The communication is typically driven by events and events and events occur ratherevents occur rather infrequentlyinfrequently..

Sensors spend a Sensors spend a considerable fraction of considerable fraction of lifetimelifetime to monitor the environmentto monitor the environment, said to be , said to be in the monitoring state.in the monitoring state.

Once events are detected, sensors may need Once events are detected, sensors may need to leave the monitoring state and actively to leave the monitoring state and actively communicate with each other.communicate with each other.


WSNs are characterized by the WSNs are characterized by the limited elimited energy supply.nergy supply.

It is generally desired to It is generally desired to turn offturn off a sensor a sensor’s radio when there is no need for com’s radio when there is no need for communication.munication.


Allowing radio to be turned off research Allowing radio to be turned off research directions have been taken to directions have been taken to preserve tpreserve the communication capability he communication capability of WSNs—of WSNs—Spatial redundancySpatial redundancy

Topology management schemes maintain netwTopology management schemes maintain network connectivity.ork connectivity.

Temporal potential in energy savingTemporal potential in energy savingWake up mechanism wake the radio up when coWake up mechanism wake the radio up when co

mmunication is necessary.mmunication is necessary.


Motivation of this paper—Motivation of this paper—Wakeup schemes have great potential in Wakeup schemes have great potential in

energy saving for sensor networks energy saving for sensor networks where events occur infrequently.where events occur infrequently.

Existing wakeup schemes encounter Existing wakeup schemes encounter critical tradeoffs between critical tradeoffs between energy savingenergy saving and and wakeup delay.wakeup delay.Ex: a message forward 10 hops on average.Ex: a message forward 10 hops on average.

Wakeup delay: 1.3 s Wakeup delay: 1.3 s end-to-end delay: 13 s end-to-end delay: 13 sObject Tracking: object speed—120km/hObject Tracking: object speed—120km/h

13s 13s 433 m 433 m


Motivation of this paper—Motivation of this paper—Propose a wakeup schemePropose a wakeup scheme

Helps to achieve the balance between Helps to achieve the balance between energy saving and end-to-end packet delay.energy saving and end-to-end packet delay.

Related WorkRelated Work

Wake schemesWake schemesSynchronous schemesSynchronous schemes

Ex: IEEE 802.11 power saving mechanismEx: IEEE 802.11 power saving mechanismIt is hard to be implemented in large WSNs.It is hard to be implemented in large WSNs.

Asynchronous schemesAsynchronous schemes““Power-saving protocols for IEEE 802.11-based Power-saving protocols for IEEE 802.11-based

Multi-hop Ad Hoc Networks.” IEEE Computer anMulti-hop Ad Hoc Networks.” IEEE Computer and Communication Societies, 2002.d Communication Societies, 2002.

The objective is to arrange the wakeup schedule The objective is to arrange the wakeup schedule so that any two neighboring nodes are guaranteso that any two neighboring nodes are guaranteed to detect each other in finite time.ed to detect each other in finite time.


The power saving capability and wakeup delay The power saving capability and wakeup delay can be improved by using an additional wakeucan be improved by using an additional wakeup channel.p channel. There is a There is a low powerlow power wakeup radio— wakeup radio—

The wakeup radio can stay awake for the entire time.The wakeup radio can stay awake for the entire time. Drawback:Drawback:

The low power wakeup radio usually has a smaller transmissThe low power wakeup radio usually has a smaller transmission range than the high power data radio.ion range than the high power data radio.

Two same capability radio—Two same capability radio— STEM (Sparse Topology and Energy Management)STEM (Sparse Topology and Energy Management) MobiHoc 2002MobiHoc 2002


STEM (Sparse Topology and Energy ManSTEM (Sparse Topology and Energy Management)—agement)—Two radioTwo radio

Wakeup radioWakeup radio Periodically turns on for TPeriodically turns on for Tdstemdstem every T duration every T duration is defined as the duty cycle ratio.is defined as the duty cycle ratio.

Data radioData radio Sleep until wakeup mechanism alerting.Sleep until wakeup mechanism alerting.

Wakeup radioSleepDuty Time

Tdstem

Sleep

T

dstemT

T


STEM (Sparse Topology and Energy STEM (Sparse Topology and Energy Management)—Management)—Wake OperationWake Operation

Sender

Receiver

Others

Tw

Twack

Duty TimeSleep

Tw

Turn on Data radio

Duty Time

Turn on Data radio


STEM (Sparse Topology and Energy ManSTEM (Sparse Topology and Energy Management)—agement)—Minimum duty timeMinimum duty time

Not synchronizedNot synchronized

When bit rate is low, TWhen bit rate is low, Tdstmdstm could be large. could be large.T has to be large enough to achieve the desired T has to be large enough to achieve the desired

energy saving, resulting in a large wakeup delay.energy saving, resulting in a large wakeup delay.

Sender

ReceiverSleep Sleep

Tw Twack Tw

Duty Time

Tdstem

Pipelined Tone Wakeup Pipelined Tone Wakeup SchemeScheme

PTW—PTW—Two radioTwo radio

Wakeup radioWakeup radio Periodically turns on for TPeriodically turns on for Tdtonedtone every T duration every T duration is defined as the duty cycle radio.is defined as the duty cycle radio.

Data radioData radio Sleep until wakeup mechanism alerting.Sleep until wakeup mechanism alerting.

dtoneT

T

Wakeup radioSleepDuty Time

Tdtone

Sleep

T


Using the Wakeup ToneUsing the Wakeup ToneWake Operation—Wakeup ChannelWake Operation—Wakeup Channel

Sender

Receiver

Others

Duty TimeSleep

Tp

Turn on Data radio

Duty Time

Turn on Data radio

ToneTone


Using the Wakeup ToneUsing the Wakeup ToneWake Operation—Data ChannelWake Operation—Data Channel

Sender

Receiver

Others

Data Transmission

Turn off Data radio

Data

Notification

Notification ACK


Using the Wakeup ToneUsing the Wakeup ToneTTdtonedtone ≧ t ≧ tdd + T + Ttransittransit

ttdd: tone detection time (200μs): tone detection time (200μs)TTtransittransit: sleep : sleep receive duration (518μs) receive duration (518μs)

TTpp= 2 × T= 2 × Tdtonedtone + T + Tsleepsleep = T + T = T + Tdtonedtone

Sender

ReceiverSleep Sleep

Tp

Tdtone TdtoneTsleep

False probability: 10-3 Detection

probability:99.1%

TR1000 RF Module

using ASK


PTW—PTW—

A wakes up all its neighbors

Wakeup Channel

Data Channel A notify

B

t0 t1 t2

B wakes up all its neighbors

A sends a data packet to B

B notify

C

C wakes up all its neighbors

t3 t4

A sends a data packet to B

t5

…

…

A B C D E F

Tp

Tdata

Tdata= Queuing delay + Channel access delay + transmission delay + Propagation delay

Tp ≦ Tdata10ms~hundreds of ms

Satisfy!!

Analysis for Energy Analysis for Energy ConsumptionConsumption

Analysis Model—Analysis Model—Total node: NTotal node: NNumber of neighbors of S: NNumber of neighbors of S: Nss

Monitoring state: TMonitoring state: Teventevent

Assume: TAssume: Tw w = T= Twackwack

TTdstemdstem= 2T= 2Tww+T+Twackwack= 3T= 3Tww = 3T = 3Twackwack

Power of Transmisson, Receive, Idle: PPower of Transmisson, Receive, Idle: P

S

D

A4

A3

A2

A1

T T T … t

Wakeup radio

t

Data radioSleepData

Wakeupprocedure

Tevent


One Wakeup Procedure—One Wakeup Procedure—The sender SThe sender S

STEM—STEM—

PTW—PTW—

Compare—Compare—

2wackw

avgstem

TTTT

avgstemevent

dstemSstem PTPT

T

TE

)( wackwpeventdstone

Stone TTTPPTT

TE

tonestem

tonestemevent

DutyDuty

DutyDuty

T

T11

13

121

Ex: Dutystem=10, Dutytone=100Need Tevent > 6.03T

dtonetone

dstemstem T

TDuty

T

TDuty ,


One Wakeup Procedure—One Wakeup Procedure—The receiver DThe receiver D

STEM—STEM—

PTW—PTW—


)( wackweventdstem

Rstem TTPPTT

TE

)( wackwavgtoneeventdtone

Rtone TTTPPTT

TE

T

avgtone

Tdt

T

tT

0 2

)11

(2

1

tonestem

event

DutyDutyT

T

Ex: Dutystem=10, Dutytone=100Need Tevent > 5.56T


One Wakeup Procedure—One Wakeup Procedure—The other neighboring nodes AThe other neighboring nodes A

STEM—STEM—

PTW—PTW—


PTT

TE event

dstemAstem

activeeventdtone

Atone TPPTT

TE wavgtoneactive TTT

tonestem

stemevent

DutyDuty

Duty

T

T11

31

21

Ex: Dutystem=10, Dutytone=100

Need Tevent > 5.93T


One Wakeup Procedure—One Wakeup Procedure—The Loose Bound for TThe Loose Bound for Teventevent

Taking into account that DutyTaking into account that Dutystemstem and Duty and Dutytonton

ee ≧1≧1

tonestem

tonestemevent

DutyDuty

DutyDuty

T

T11

1

3

1

2

1

tonestem

event

DutyDutyT

T11

611

Ex: wakeup and Ack packet size: 144 bits tone detection time: 100μs Bit Rate=3x144/100=4.3MbpsIn most application, It is not likely a low cost sensor will be equipped.


Multiple Wakeup Procedures—Multiple Wakeup Procedures—The Loose Bound for TThe Loose Bound for Teventevent

H: The max number of wakeup procedures a noH: The max number of wakeup procedures a node is involved upon an event.de is involved upon an event.

tonestem

event

DutyDuty

H

T

T11

611

Ex: Dutystem=10, Dutytone=100, H=5Need Tevent > 102T

Performance EvaluationPerformance Evaluation

Simulator: The modified version of ns-2Simulator: The modified version of ns-2Radio power: TR1000 (20m)Radio power: TR1000 (20m)Wakeup packet size: 144 bitsWakeup packet size: 144 bitsData packet size: 1040 bitsData packet size: 1040 bitsData Ack size: 128 bitsData Ack size: 128 bitsBits Rate: 2.4Kbps Bits Rate: 2.4Kbps

TTdstemdstem=225ms, Duty=225ms, Dutystemstem=13.33=13.33TTdtonedtone=1ms, Duty=1ms, Dutytonetone=229=229


Cluster Scenario—55 nodesCluster Scenario—55 nodes11 11 clustersclustersSource: Source: Node 0Node 0, Destination: , Destination: Node 50Node 50Path:Path:005510101515202025253030353544

0045455050 (Ten events with 100s period) (Ten events with 100s period)Extreme case: All node will be Extreme case: All node will be

awakened. Many nodes will be awakened. Many nodes will be awakened multiple times.awakened multiple times.

55


Cluster Scenario—Cluster Scenario—Individual Energy Consumption (Joule)Individual Energy Consumption (Joule)

Source Forward node NF-Neighbor Sink


Cluster Scenario—Cluster Scenario—Total energy consumption & end-to-end Total energy consumption & end-to-end

delaydelay10 hops10 hops


Random Generated Networks—Random Generated Networks— 10 random topologies are generated.10 random topologies are generated. 100 nodes100 nodes Square area: 79.25m x 79.25mSquare area: 79.25m x 79.25m Average number of neighbor each node: 20Average number of neighbor each node: 20 As different values of DutyAs different values of Dutystemstem in STEM trade off ener in STEM trade off ener

gy with delay.gy with delay. STEM1— DutySTEM1— Dutystemstem=5.33=5.33 STEM2— DutySTEM2— Dutystemstem=13.33=13.33

10 events10 events


Random Generated Networks—Random Generated Networks—

ConclusionConclusion

It has presented a It has presented a Pipelined Tone Wakeup Pipelined Tone Wakeup (PTW) scheme(PTW) scheme for sensor network, which for sensor network, which helps to achieve the balance between helps to achieve the balance between energy savingenergy saving and and end-to-end delayend-to-end delay..

The use of The use of wakeup tonewakeup tone enables a large enables a large duty cycle ratio without causing a large duty cycle ratio without causing a large wakeup delay at each hop.wakeup delay at each hop.

It helps the It helps the pipelinepipeline to hide most of the to hide most of the wakeup delaywakeup delay while achieving a major while achieving a major energy saving.energy saving.

a wakeup scheme for sensor networks: achieving balance between energy saving and end-to-end delay...

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