energy-efficient wake-up scheduling for data collection and aggregation yanwei wu, member, ieee,...
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Energy-Efficient Wake-Up Scheduling for Data Collection and Aggregation
Yanwei Wu, Member, IEEE, Xiang-Yang Li, Senior Member, IEEE,
YunHao Liu, Senior Member, IEEE, and Wei Lou
IEEE TPDS, vol. 21, no. 2, 2010, pp. 275-287.
Outline
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Introduction System model and assumption Homogeneous wireless sensor networks Heterogeneous wireless sensor networks Formation of data gathering tree Performance evaluation Conclusion
Introduction Wireless sensors are often powered by batteries and have
limited computing and memory resources. Schedule the nodes’ activities to reduce energy consumption.
Previous studies did not consider all possible energy consumption by wireless sensors, Wasted listening, and the state transitions.
3
Introduction
4
Traditionally, the scheduling algorithms often schedule the individual activities for each sensor one by one. Find the best time slots for sending and receiving data.
Communication and interference range. Homogeneous wireless sensor networks Heterogeneous wireless sensor networks
Introduction
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A scheduling should reduce the state transitions to increase the lifetime of a sensor.
To minimize the sensor’s wake-up times in a scheduling period. Any sensor node needs only to wake up at most twice in our
protocol. Once for continuously receiving all packets from its children nodes
and once for sending its own data to its parent node.
System model and assumption
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Network System Models Problem Description
Network System Models
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Tree-based All data will be collected and sent to the sink.
Each wireless node will use a fixed power to communicate with its neighboring sensors. The fixed power transmission by a node vi will define an
interference range. RI(vi) such that the transmission of node vi will interfere the reception of
any node vk when
The physical link <vi, vj >is reliable if vi can communicate with vj.
)( iIik vRvv
)(*)1()( iTiII vRvRR )( iI vR
)( iT vR
vk
vi
vj
Problem Description
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Energy-Efficient Scheduling Data Collection Tree Construction
Problem Description-Energy-Efficient Scheduling
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The amount of slots assigned to a node vi for transmitting should be enough.
A node vi with children nodes u1, u2, . . . , uj should be active for receiving at the time slots when these children nodes send data to vi.
T
t
itSi p
wX
1,,
1,1 ,,,, tRitSj XX tSjtRi XX ,,,,
The observed link reliability
Packets received from its children nodes
{0,1}
Problem Description-Energy-Efficient Scheduling
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Any node can only be in one of the states.
All transmissions should be interference-free.
1,,,,,,,, tLitPitRitSi XXXX
1,,,, tSjtSi XX
{0,1}
Problem Description-Energy-Efficient Scheduling
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Notice that the energy cost by a node vi in all states is
The energy cost for state transitions is
T
tsslptPilsttLircvtRitxtSi tPXPXPXPX
1,,,,,,,, *)****(
T
tLPtLitPiRPtRitPiSPtSitPi EXXEXXEXX
1,1,,,,,1,,,,,1,,,, )******(
The objective of a schedule S is to minimize the summation of these two energy costs.
Slot sizeEnergy consumption of #
{0,1}
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Problem Description-Data Collection Tree Construction Tree T is given for the data collection or aggregation.
The total energy cost of the optimum activities scheduling based on this tree is the lowest.
The objective is to find a data collection tree T that should satisfy the data requirements of all nodes. NP-hard problem.
Goals
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This paper use a TDMA for scheduling node activities to reduce the energy consumption.
Focused on the energy cost by the radio. Transmitting, receiving, listening, and sleeping.
Outline Introduction System model and assumption Homogeneous wireless sensor networks Heterogeneous wireless sensor networks Formation of data gathering tree Performance evaluation Conclusion
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Homogeneous wireless sensor networks-Centralized Activity Scheduling
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)( iTj vCvii wW
The total number of time slots that node vi should wake up toreceive the data from its children is:
6iW
6iW
4iW
Parent node
Child node
Homogeneous wireless sensor networks- Centralized Activity Scheduling
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Conflicting Cluster
Homogeneous wireless sensor networks-Centralized Activity Scheduling
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4
1-hop
4-hop
3-hop
2-hop
1/2
The node z is within the distance at most 3RI from node p. The sensors from conflicting clusters Cj,l can only be distributed inside the circle with the radius 3RI
z
q
v
p
RI(p)
RT(p)
)(*)1()( pRpRR TII
u
Homogeneous wireless sensor networks-Centralized Activity Scheduling
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Schedule the clusters in the decreasing order of their weight Wi. Then each child vj will be assigned a consecutive wj time slots
from this chunk.
Time slot
Wj,i :The clusters which conflict with cluster Ci and are scheduled before cluster Ci.
gj,i : Gaps ,non-conflicting clusters, which could be assigned to cluster Ci.
Wi
{w1,w2,w3…}
Homogeneous wireless sensor networks- Centralized Activity Scheduling
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SW
SYN
SW
SYN
SW
SYN
SW
SYN
Time slotgj,1 gj,2gj,3 gj,4wj,1 wj,2 wj,3 wj,4
7,4 iWC
6,5 iWC
4,6 iWC
3,1 iWC 3,3 iWC
4,2 iWC
4,7 iWC
C4 C5C2
....,,,, 76254 CCCCC
Homogeneous wireless sensor networks- Centralized Activity Scheduling (More discussions)
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Besides reducing the energy consumption and increasing network throughput Another important issue in WSNs is to reduce the delay.
Instead of scheduling using the available earliest time slots, this paper use the latest available time slots.
SW
SYN
SW
SYN
SW
SYN
SW
SYN
Time slotgj,1 gj,2gj,3 gj,4wj,1 wj,2 wj,3 wj,4
di ui
di,wi=3
ui,wi=4
diui
Homogeneous wireless sensor networks- Distributed Activity Scheduling (TTL)
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34 CC
7,4 iWC
6,5 iWC4,6 iWC
3,1 iWC 3,3 iWC
3,2 iWC
4,7 iWC
SW
SYN
SW
SYN
SW
SYN
SW
SYN
Time slotgj,1 gj,2gj,3 gj,4wj,1 wj,2 wj,3 wj,4
C4 C7
IamScheduled
27 CC
IamScheduled
Outline Introduction System model and assumption Homogeneous wireless sensor networks Heterogeneous wireless sensor networks Formation of data gathering tree Performance evaluation Conclusion
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Heterogeneous wireless sensor networks -Centralized Activity Scheduling
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7,4 iWC
6,5 iWC
4,6 iWC
3,1 iWC 3,3 iWC
3,2 iWC
4,7 iWC
SW
SYN
SW
SYN
SW
SYN
SW
SYN
Time slotgj,1 gj,2gj,3 gj,4wj,1 wj,2 wj,3 wj,4
C2C3
},,{ 1763 CCCB
First divide the sensors into buckets according to their interference radii.
},{ 321 CCB
},{ 452 CCB
Interference Range : B1<B2 <B3
C4
Heterogeneous wireless sensor networks -Distributed Activity Scheduling (TTL)
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7,4 iWC
6,5 iWC
4,6 iWC
3,1 iWC 3,3 iWC
3,2 iWC
4,7 iWC
SW
SYN
SW
SYN
SW
SYN
SW
SYN
Time slotgj,1 gj,2gj,3 gj,4wj,1 wj,2 wj,3 wj,4
C6C7
},,{ 1763 CCCB
First divide the sensors into buckets according to their interference radii.
C1
Formation of data gathering tree -Connected dominating set
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Energy efficiency is a critical issue in WSNs since the sensor nodes are with limited energy.
Performance evaluation
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Randomly placing 32 sensors in a square 5*5 square meters.
Transmission radius as 1m. Interference radius as 2m.
Performance evaluation
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Impact of Data Rate
Performance evaluation
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Impact of Number of Nodes
Performance evaluation
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Impact of Heterogeneous Nodes
Conclusion
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In this paper proposed an efficient centralized and distributed scheduling algorithms. Remove the unnecessary listening cost Reduce the energy cost for state switching and clock
synchronization.
Every node needs only to wake up at most twice in one scheduling period One for receiving data from its children and one for sending
data to its parent.