A Quorum-Based Energy-Saving MAC Protocol Design for Wireless Sensor NetworksChih-Min Chao, Yi-Wei Lee
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, 2010
Outline• Introduction• Preliminaries• Protocol description• Simulation results• Conclusions
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Introduction• Wireless sensors are battery powered.• It is crucial for them to efficiently use their battery resources.
• Most of the existing power-saving protocols achieve power savings by periodically putting sensor nodes to sleep.• Lower power efficiency• Higher latency.
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Introduction• Many protocols have been proposed to extend the network
lifetime of sensor networks • Deployment protocols • Power efficient medium access control protocols • Routing protocols
• Energy-hole problem• Sensor nodes that are closer to the sink deplete their power
faster.
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Problem Statement
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Host A
Host B
0 1 2 3 4 5 6 7 8 Time
Quorum Concept
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0 1 2
3 4 5
6 7 8
n
n
Ra
Rb
Ca Cb
Host A
Host B0 1 2 3 4 5 6 7 8 Time
QMACQuorum-based MAC protocol
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QMAC
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Time frame
Time
B
C
D
E
A RTS
CTS
DATA
ACK
SIFS SIFS SIFS
Sleep
Sleep
Sleep
• To reduce power consumption and determine the sleep frequency for each sensor node based on its own traffic load.
Preliminaries• Time is divided into a series of time frames.• All sensor nodes are time synchronized.• Each node has a unique ID.• Sensor nodes report their data to their common sink node.• All sensor nodes have the same transmission range.• All sensor nodes are static after deployment.
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Preliminaries• Sensor nodes are randomly and uniformly distributed in the
network area.
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Sink
C1
C2
C3
C4
Hop Count=1
Hop Count=2
Hop Count=3
Hop Count=4
Quorum-Based Wake-Up Schedule• A sensor node using an n × n grid will wake up 2n − 1 out of n2
time frames.• Grid size
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The ratio of areas for different coronas C1:C2:C3:C4=1:3:5:7
2R 222 3)2( RRR
A node in C3 is responsible for relaying traffic for 7/5 nodes in C4
Quorum-Based Wake-Up Schedule
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The traffic load in C3 is 1 + (7/5) × 1 = 2.4
The ratio of areas for different coronas C1:C2:C3:C4=1:3:5:7
The traffic load in C1 is 1 + 3 × 5 = 16
The traffic load in C2 is 1 + (5/3) × 2.4 = 5
Latency Reduction• In allowing sensor nodes to sleep longer than one time frame
to reduce energy consumption.• The price for this saved energy, though, is higher latency.• Next-hop group
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Next-hop group
Sink
C1C2 C3
C4
X
One hop neighbor boundary
Next hop group member
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Simulation results• NS2• DMAC• The shortest transmission latency
• PMAC• An adaptive energy-saving protocol
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Parameter Value Parameter Value
Number of nodes 400 Power consumptionTransmit, receive, idle, sleep
0.66,0.395,0.35, 0 W
Circular of radius 250m Node initial energy 50J
Transmission range 75m Simulation time 700s
Channel capacity 10 kb/s
First corona 2*2
Time frame 100ms
Simulation results
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Simulation results
Fig. 9. Effect of different MAC protocols on the fraction of live sensor nodes at different coronas at simulation times of (a) 100 s, (b) 200 s, and (c) 300 s.
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Simulation results
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Simulation results
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Simulation results
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Simulation results
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Simulation results
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Simulation results
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The number of nodes for networks with 3, 4, and 5 coronas is 225, 400, and 625.
Conclusions• The sensor nodes have different loads due to their different
distances to the sink• The concept of quorum to enable sensor nodes to adjust their
sleep durations based on their traffic loads.• QMAC• QMAC_LR
• Simulation results verify that our QMAC_LR reduces energy consumption and keeps the latency low.
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