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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