emergency navigation by wireless sensor networks in 2d and 3d indoor environments

1

Emergency Navigationby Wireless Sensor Networks

in 2D and 3D Indoor Environments

Yu-Chee Tseng

Deptment of Computer Science

National Chiao Tung University

2

Outline

Introduction System Overview Environment setting Regular report Emergency navigation service Simulation results Demonstration Conclusion

3

Outline

Introduction System Overview Environment setting Regular report Emergency navigation service Simulation results Demonstration Conclusion

4

Introduction

Wireless Sensor Network Each sensor has

Limited Memory 、 Limited CPU 、 Wireless Transceiver 、 Sensing Unit

Each sensor can Sense environments Communicate with others Do simple computations

5

Introduction

Traditional Navigation Devices Advantage

Cheap Easy deployment

Disadvantage Fixed direction. Can not adapt to actual emergency situations.

6

Introduction

Motivation According to the statistic report of the NFA of Taiwan(內政部消防署） , 228 people died in fire accidents in 2003.

The main reason is that people can not find “right” escaping paths to exits.

Our Goal to develop an emergency navigation system for indoor 2D and 3D environments

7

Outline

Introduction System overview Environment setting Regular report Emergency navigation service Simulation results Demonstration Conclusion

8

System Overview

Our system is composed of 3 parts Environment setting Regular reporting Emergency Navigation

Two network graphs Communication graph and guidance graph

room room

room room

room room

room room

Communication graph Guidance graph

9

Environment Setting

Deploy sensors Construct reporting tree Setup initial navigation paths

navigating

reporting

10

Outline


11

Deployment of Sensors

Plan locations of sensors Define the roles of sensors

Sink Exit sensors Normal sensors

Decide navigation links

navigationlinks

(for human)

12

Construct a Reporting Tree

Step 1. Discover symmetric links Each sensor periodically broadcasts HELLOs When receiving a HELLO, sensors reply ACKs After receiving an ACK, sensors record the sender ID in its

link table

HELLO

ACKACK

ACKLink table

1 02

3

2 3

13

Construct a reporting tree (cont.)

Step 2. Construct a spanning tree Sink floods a BEACON. For a sensor receives a BEACON, it checks if the sender is

in its link table If yes, it sends a REG(ister) to sink and rebroadcasts BEAC

ON. Else, drops it

BEACON

REG

BEACON

14

communicationlinks

(for packets)

15

Outline


16

Reporting Issues

How often a report should be sent? Will each sensor report individually? Is there any inaccuracy? False alarm? How to save energy of sensors?

17

Outline

Introduction System overview Environment setting Regular report Emergency navigation in 2D environment Simulation results Demonstration Conclusion

18

Design Principle

When a sensor detects an emergency event, it forms a hazardous region

The navigation algorithm will try to guide people as farther away from hazardous regions as possible

19

Problem Formulation

Each sensor has an altitude. Sensors in hazardous regions will raise their

altitudes. Each sensor guides people to the neighbor with the

lowest altitude After forming hazardous regions, some sensors may

become local minimum ones A partial link reversal operation is performed to solve this

problem

20

Phases of Navigation

Initialization phase Initial phase is started by Exit sensor After this phase, every sensor has a default guiding

direction.

Navigation phase This phase starts by the sensor which detects an

emergency event.

21

Terminology

D ： The radius of the hazardous region Aemg ： A large constant which represents the maxim

um altitude Ai ： The altitude of sensor i

Ii ： The altitude obtained in the initialization phase

ej,i ： The hop count from emergency sensor j to sensor i

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Initialization phase

Every exit sensor sets its altitude to 0 and broadcasts an initialization packet.

When receiving an initialization packet, a sensor adds its hop count by 1.

Then, it compares the hop count with its current altitude

1

3 4 5

6 7 8

2

0 0Initial Packet0

∞ ∞ ∞

∞ ∞ ∞

∞ ∞ ∞

00

Initial Packet

Sender ID Exit ID Hop Count

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Initialization phase (cont.) If the hop count is smaller than its altitude, it resets its altitude

and setups its initial guiding direction to that sender. Then, it rebroadcasts this packet.

1

3 4 5

6 7 8

2∞ ∞

∞ ∞ ∞

∞ ∞ ∞

0 1

1

0 0Initial Packet0

0 1Initial Packet3

0 1Initial Packet1

2

2

2

3

3

0 2Initial Packet2

0 3Initial Packet5

4

0

24

Navigation phase

When a sensor x detects an emergency, it will set its altitude to the maximum altitude Aemg (let it be 200).

Then it broadcasts an emergency packet EMG(seq, x, x, Aemg, 0)

seq ： sequence number x ： emergency ID w ： sender ID Aw ： altitude of sender h ： hop count to emg. location

23 24 25

26 28

29 30 31

2727 27

EMG0 200 0

10 11

11 12

12

12 13

13

14

200

x w

EMG

Seq Aw H

25

Navigation phase (cont.) When a sensor node y receives a EMG packet originated from

node x, it will do the following steps. Step1:

Decide that the emergency is a new one or not If it’s a new emergency, record this event and set the hop count ex,y to h+1.

Else, compare the h and ex,y. If h is smaller than ex,y , set ex,y to h+1.

Record the altitude (Aw) in the navigation link table.

Emg Table

EmgID ex,y

23 24 25

26 28

29 30 31

27

10 11 12

12 13

13

14

11 200

Emg Table

27

EmgID ex,y

1

26

Navigation phase (cont.) Step 2:

If eX,Y was changed in step1 and eX,Y D, y considers itself withi≦n hazardous region. Then it re-calculates its altitude as follows ：

Emg Table

27

EmgID ex,y

1

Safety Factor D:1

ex,y < D ?

23 24 25

26 28

29 30 31

27

10 11 12

12 13

13

14

11 200

2

,

1max ,

1y y emg y

x y

A A A Ie

2

,

2

1

1

1200 11 61

1 1

emg y

x y

A Ie

61 63

63

61

27


If y has a local minimum altitude and it’s not an exit, it must adjust its altitude as follows ：

= altitudes of y’s neighbors STA = standard deviation

A bigger value means closer to the hazardous region. So we need to adjust the altitude faster.

|Ny| = number of neighbors of y. A smaller | Ny | means less escape ways. So we need to adjust the altitude faster.

δis a small constant.

1( ) min

y yy N N

y

A STA A AN

yNA

23 24 25

26 28

29 30 31

2720061 63

63

61

12

1210

14

Local minimum?10 63 0.1 63.1

2

63.1

Static adjustment

Our scheme

Five iterations

Three iterations

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y has to broadcast an EMG(seq, x, y, Ay, ex,y) packet if any of the following conditions matches. It’s a new emergency y has changes its altitude or ex,y in the previous steps.

Step 5: If y is in hazardous regions and it sees an exit sensor which is

in Ny and which is also in hazardous regions, then y chooses this exit sensor

In all other cases, y directs users to a safer sensor first, and then gradually to a safe exit.

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Example—Altitude after initial phase

1

4

7

10

S1

S4

S7

S10

Exit

10x10 Grid Network

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One emergency event –after step 1, 2 & 4

1

4

7

10 S1

S4

S7

S10

Local minimum

31

One emergency event–final result

1

4

7

10 S1

S4

S7

S10

32

Two emergency events–after step 1, 2 & 4

1

4

7

10

S1

S3

S5

S7

S9

Local minimum

33

Two emergency events–final result

1

4

7

10

S1

S3

S5

S7

S9

34

Outline


35

Simulation results

We compare our navigation algorithm with “Distributed algorithm for guiding navigation across a sensor network” (MobiCom 03)

This algorithm guides people to the nearest exits However, nearest exits may not be good choices

36

Simulation results

Case1. Our algorithm will choose to pass hazardous region areas as farther away from emergency locations as possible.

Case2. Our algorithm will not guide people passing through the hazardous region.

Case3. Only the sensors near the exit in the hazardous region will guide people to that exit.

Exit Emergency Hazardous region

742 137

PathPkt.

count

Method of Li et al. Our method (D=2)

3

NoPath

Pkt. count

AA

979 2521

1254 4082

37

Outline


38

Demonstration

System Components MICAz sensors

Environment monitoring Navigation Sink

MIB510 serial Gateway Gateway between wireless sensor network and PC

PC Control Host

39

Demonstration

exit(normal

time)

first event(emergency

time)

second event(emergency

time)

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A Short Summary (2D)

Novel indoor monitoring and navigation services based on wireless sensor network technolgoies emergency will raise sensors’ altitudes navigation similar to TORA protocol, but different in that emergen

cies will disturb altitudes altitude adjustment is designed for quicker convergence navigation in emergency applications requires safer paths, but no

t necessarily longer paths

41

Emergency Navigation in Indoor 3D Environments by Wireless Sensor Networks

Yu-Chee Tseng

Department of Computer Science

National Chiao Tung University

42

Introduction Why 2D guiding algorithms can’t directly apply to 3D environments

room

room

room room

room room

2F

room room

room room

3F

room

room

1F

1F

room

room

2F

Rooftop

room

roomroom

room

room

room

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System Architecture

Controller

SinkControl host

3F

room

room

room

room

2F

room

room

room

room

1F

room room

4F

room

room

room

room

exit sensorstair sensornormal sensorguidance direction

room room

to rooftop

to rooftop

B

AC

C

A

A

A

A

A

D

D

A: floor gatewayB: stair gatewayC: floor/stair gatewayD: floor/roof gateway

(0, 0) (0, 1)

(1, 0)

(0, 0)

(0, 2)(0, 0) (0, 1)

(0, 1)(0, 1)

(0, 2) (0, 3) (0, 2) (0, 1)

(0, 2)(0, 1)(0, 2)

(1, 1)

(1, 0)

(1, 2)(1, 2) (1, 3)

(1, 1)(1, 1)

(1, 2) (1, 3) (1, 2) (1, 1)

(1, 2)(1, 3)(1, 2)

(2, 1)

(2, 0)

(2, 2)(2, 2) (2, 1)

(2, 1)(2, 1)

(2, 2) (2, 3) (2, 2) (2, 1)

(2, 2)(2, 3)(2, 2)

(2, 0)

(3, 1)

(3, 0)

(3, 2)(3, 1) (3, 2)

(3, 1)(3, 1)

(3, 2) (3, 2) (3, 1) (3, 1)

(3, 1)(3, 0)(3, 1)

(3, 0)

(lemg, -(lIy+1))

(lemg, -(lIy+1))

44

Guidance initialization

(0, 0) (0, 1)

(0, 2)(0, 1)

(0, 2)

(1, 0)

(0, 3)

(1, 1)

(1, 1)

1F

2F

a

b

c

d

e

f

45

Guidance initialization

3F

room

room

room

room

2F

room

room

room

room

1F

room room

4F

room

room

room

room

room room

(0, 0) (0, 1)

(1, 0)

(0, 0)

(0, 2)(0, 0) (0, 1)

(0, 1)(0, 1)

(0, 2) (0, 3) (0, 2) (0, 1)

(0, 2)(0, 1)(0, 2)

(1, 1)

(1, 0)

(1, 2)(1, 2) (1, 3)

(1, 1)(1, 1)

(1, 2) (1, 3) (1, 2) (1, 1)

(1, 2)(1, 3)(1, 2)

(2, 1)

(2, 0)

(2, 2)(2, 2) (2, 1)

(2, 1)(2, 1)

(2, 2) (2, 3) (2, 2) (2, 1)

(2, 2)(2, 3)(2, 2)

(2, 0)

(3, 1)

(3, 0)

(3, 2)(3, 1) (3, 2)

(3, 1)(3, 1)

(3, 2) (3, 2) (3, 1) (3, 1)

(3, 1)(3, 0)(3, 1)

(3, 0)

46

Principles of 3D guidance

A sensor is located in a hazardous region if it is D hop away from the emergency point or it’s a stair sensor and its downstair sensor is in a hazardou

s region

When guiding Avoid to guide people through hazardous regions Try to guide people to the exits on the ground floor Guide people to rooftop if there is no proper ways to downs

tairs

47

Simulation results

1F

3F

2F

4F

1F

3F

2F

4F

1F

3F

2F

4F

1F

3F

2F

4F

1F

3F

2F

4F

1F

3F

2F

4F

roof gateway go upstairs go downstairs

48

Prototyping

We have implemented our system using MICAz motes and MTS310 sensors on TinyOS.

Protocol stack

Physical layer and Data link layer

TreeReconstruction

Deployment GUINetworkinitialization

Guidanceinitialization

Query

Sensor taskGuidance

service

Symmetric linkdetection

Tree maintenance

HELLO Report EMG

Application-level UI

Application layer

Network layer

Sensors partUsers part

Physical layer and Data link layer

TreeReconstruction

Sensor taskGuidance

service

Symmetric linkdetection

Tree maintenance

Guidance interface

HELLO Report EMG

(a) Sink (b) Sensor

49

JAVA GUI

Building plan panel

sink

Control panel

Monitor panel

Current guidance direction

exit

EMGstair

stair

stair

→ 21 (in dec.)

50

Guidance UI

51

Demonstration

Environment A virtual 2-store

building

Sink

Control host

Exit

Exit

Exit

ExitStair

Stair

Stair

Stair

52

Demonstration

Vedio

53

More Results

2F

1F

Stair sensor Exit sensor Emergency

Guidance pkt. count 151.8

Tree Reconstruction pkt. count 7.6





(a) (b) (c)

3F

roof

roof

54

Conclusions

Extending 2D navigation to 3D navigation

on each floor, the navigation is similar to 2D

stair and gateway sensors are paid of special attention

roof is also paid of special attention

55

References

Q. Li, and et. al, “Distributed algorithm for guiding navigation across a sensor network”, MobiCom 03.

Y.-C. Tseng, M.-S. Pan, and Y.-Y. Tsai, “A Distributed Emergency Navigation Algorithm for Wireless Sensor Networks”, IEEE Computers, Vol. 39, No. 7, July 2006, pp. 55-62.

M.-S. Pan, C.-H. Tsai, and Y.-C. Tseng, “Emergency Guiding and Monitoring Applications in Indoor 3D Environments by Wireless Sensor Networks”, Int’l Journal of Sensor Networks, Vol. 1, Nos. 1/2, pp. 2-10, 2006.

emergency navigation by wireless sensor networks in 2d and 3d indoor environments

Documents

sensor guides people

symmetric linkseach

hazardous regions

energy of sensors

emergency event

reporting treestep

actual emergency situations

link tableif