Decentralized Energy-Conserving and Coverage-Preserving Protocols

for Wireless Sensor Networks

Chi-Fu Huang, Li-Chu Lo, Yu-Chee Tseng, and Wen-Tsuen ChenDepartment of Computer Science and Information Engineering National Chiao-Tung UniversityDepartment of Computer Science National Tsing-Hua UniversityIEEE International Symposium on Circuits and System (ISCAS’05)

Outline Introduction 1-Coverage-Preserving Protocol

Basic Energy-based

Simulation Results Conclusion

Introduction This paper proposed protocols are

based on a model similar to that of [8], but improve it First, reduce the computational complexity Second, balance sensors’ energy

expenditure [8] Differentiated surveillance for

sensor networks. (SenSys 2003)

Introduction Goals

Provide an approach for nodes to decide their sleep/work mode schedules:

Guarantee Full-coverage Redundant nodes go to sleep to save

energy and extend system lifetime

Introduction -Differentiated surveillance for sensor networks Work/Sleep schedule for a single point

A B

C

Node A

Node B

Node C

0 10030 70

10 60

5 45

time

Awake Asleep

Point XPoint X

Point X

10

Introduction -Differentiated surveillance for sensor networks Work/Sleep schedule for a single point

A B

C

Node A

Node B

Node C

Awake

0 10030 70

60

5 45

time

Asleep

Point X

Point x is covered by at least one node’s sensing area at any time

tA

C

B

Introduction -Differentiated surveillance for sensor networks

Point X

t

0

100

105

20

refC

40

refA

90

refB

120

refC

100

30 655105

Tfront Tend

Reference randomly selected from [0, T)Each node broadcasts tuple (location, reference)

Introduction -Differentiated surveillance for sensor networks

frontT frontT frontTendT endT endT

Sensing PhaseInit Phase

ref ref

Round 0(Duration T) Round 1 Round n

………

Work Schedule: [n×T + ref – Tfront ﹐ n×T + ref + Tend]

ref

D

C

BA

Introduction -Differentiated surveillance for sensor networks Schedules for All Grid Points

E

Grid Points

Introduction -Differentiated surveillance for sensor networks

1-Coverage-Preserving Protocol-Assumption

Sensors Si , i = 1,…,n Location (Xi , Yi ) Sensing Range ri

Each Sensor can switch between the active mode and the sleeping mode

Two sensors Si and Sj are neighbors If they have non-empty overlapping sensing

region Sensors can communicate with his neighbors

1-Coverage-Preserving Protocol– Basic

The structure of sensors’ working cycles

1. Location (Xi ,Yi )

2. Sensing range ri

3. Reference time Refi

1-Coverage-Preserving Protocol – Basic

Initialization phase Each sensor Si broadcasts a HELLO packet after random backoff

Location (Xi , Yi ) Sensing range ri

Reference time Refi randomly selected from [0, Trnd ) Each sensor Si can calculate it own working schedule in the sensing phase

To calculate Fronti and Backi

1-Coverage-Preserving Protocol – Basic

Each sensor’s Fronti and Backi should be carefully selected to ensure that the sensing area is sufficiently covered

To achieve this goal, we use intersection points If all intersection points in the target area

A are covered by any sensor’s sensing range, the target area A is sufficiently covered

m

1-Coverage-Preserving Protocol– Basic

t

t

0 2

Ref1

9

Ref2

11

Ref3

20

5.5 16.5

Front1=5.5Back1

=3.5

20

n

q

S1

S3S5

S2S4

p

r

Schedule for p

Front1

2 11 205.5

9 2 203.5

0

1-Coverage-Preserving Protocol– Basic

1-Coverage-Preserving Protocol – Energy-base

Each sensor Si is aware of its current remaining energy, denoted as Ei

Each sensor Si broadcasts its Ei in the HELLO packet

1-Coverage-Preserving Protocol – Energy-base

Fronti and Backi of the sensor Si are chosen based on Ei

Simulation Result 100 x 100 square are 150 sensors, randomly generated Sensing range 25 A working cycle (Tw_cycle) include 5

rounds To set up sensors’ initial energies

Can active from 1 to 50 complete rounds in randomly selected manner

Simulation Result

Simulation Result

Conclusion The paper protocols improve the

results in several sense Significantly reduce the computational

complexity Use intersection points

Further balance sensors’ energy expenditure

Use sensors’ remaining energy

Thank you !!