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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.
IntroductionIntroduction
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.
IntroductionIntroduction
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.
IntroductionIntroduction
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
IntroductionIntroduction
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.
Related WorkRelated Work
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
Related WorkRelated Work
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
Related WorkRelated Work
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
Related WorkRelated Work
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
Pipelined Tone Wakeup Pipelined Tone Wakeup SchemeScheme
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
Pipelined Tone Wakeup Pipelined Tone Wakeup SchemeScheme
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
Pipelined Tone Wakeup Pipelined Tone Wakeup SchemeScheme
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
Pipelined Tone Wakeup Pipelined Tone Wakeup SchemeScheme
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
Analysis for Energy Analysis for Energy ConsumptionConsumption
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 ,
Analysis for Energy Analysis for Energy ConsumptionConsumption
One Wakeup Procedure—One Wakeup Procedure—The receiver DThe receiver D
STEM—STEM—
PTW—PTW—
Compare—Compare—
)( 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
Analysis for Energy Analysis for Energy ConsumptionConsumption
One Wakeup Procedure—One Wakeup Procedure—The other neighboring nodes AThe other neighboring nodes A
STEM—STEM—
PTW—PTW—
Compare—Compare—
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
Analysis for Energy Analysis for Energy ConsumptionConsumption
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.
Analysis for Energy Analysis for Energy ConsumptionConsumption
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
Performance EvaluationPerformance Evaluation
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
Performance EvaluationPerformance Evaluation
Cluster Scenario—Cluster Scenario—Individual Energy Consumption (Joule)Individual Energy Consumption (Joule)
Source Forward node NF-Neighbor Sink
Performance EvaluationPerformance Evaluation
Cluster Scenario—Cluster Scenario—Total energy consumption & end-to-end Total energy consumption & end-to-end
delaydelay10 hops10 hops
Performance EvaluationPerformance Evaluation
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
Performance EvaluationPerformance Evaluation
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.