by Wireless Sensor Networks

flangeeasyMobile - Wireless

Nov 21, 2013 (3 years and 8 months ago)

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1

Emergency Navigation

by 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


Introduction


System overview


Environment setting


Regular report


Emergency navigation service


Simulation results


Demonstration


Conclusion

11

Deployment of Sensors


Plan locations of sensors


Define the roles of sensors


Sink


Exit sensors


Normal sensors


Decide navigation links

navigation

links

(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

ACK

ACK

ACK

Link table

1

0

2

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
BEACON.


Else, drops it


BEACON

REG

BEACON

14


communication

links

(for packets)

15

Outline


Introduction


System overview


Environment setting


Regular report


Emergency navigation service


Simulation results


Demonstration


Conclusion

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


A
emg


A large constant which represents the
maximum altitude


A
i

The altitude of sensor
i


I
i

The altitude obtained in the initialization phase


e
j,i

The hop count from emergency sensor
j

to
sensor
i



22

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
0
Initial Packet
0


















0

0
Initial Packet
Sender ID
Exit ID
Hop Count
23

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
0
Initial Packet
0
0
1
Initial Packet
3
0
1
Initial Packet
1
2

2

2

3

3

0
2
Initial Packet
2
0
3
Initial Packet
5
4

0
24

Navigation phase



When a sensor
x

detects an emergency, it will set its altitude to the
maximum altitude A
emg

(let it be 200).


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







seq

sequence number


x

emergency ID


w


sender ID


A
w

altitude of sender


h

hop count to emg. location

23
24
25
26
28
29
30
31
27
27
27
EMG
0
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 e
x,y
to h+1.


Else, compare the h and e
x,y
. If h is smaller than e
x,y

, set e
x,y

to h+1.


Record the altitude (A
w
) in the navigation link table.

Emg Table
EmgID
e
x
,
y
23
24
25
26
28
29
30
31
27
10

11

12

12

13

13

14

11

200

Emg Table
27
EmgID
e
x
,
y
1
26

Navigation phase (cont.)


Step 2:



If e
X,Y
was changed in step1 and e
X,Y

D, y considers itself
within hazardous region. Then it re
-
calculates its altitude as
follows





Emg Table
27
EmgID
e
x
,
y
1
Safety Factor D
:
1
e
x
,
y
<
D

?
23
24
25
26
28
29
30
31
27
10

11

12

12

13

13

14

11

200



2
,
1
max,
1
y y emg y
x y
A A A I
e
 
 
  
 

 
 




2
,
2
1
1
1
200 11 61
1 1
emg y
x y
A I
e
  

  

61

63

63

61

27

Navigation phase (cont.)


Step 3
:


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.


|N
y
| = number of neighbors of y.


A smaller | N
y

| means less escape ways. So we need to adjust the altitude faster.


δis a small constant.



1
( ) min
y y
y N N
y
A STA A A
N

   
y
N
A
23
24
25
26
28
29
30
31
27
200

61

63

63

61

12

12

10

14

Local minimum
?
1
0 63 0.1 63.1
2
   
63.1

Static adjustment

Our scheme

Five iterations

Three iterations

28

Navigation phase (cont.)


Step 4:


y has to broadcast an EMG(seq, x, y, A
y
, e
x,y
) packet if any of
the following conditions matches.


It’s a new emergency


y has changes its altitude or e
x,y

in the previous steps.


Step 5:


If y is in hazardous regions and it sees an exit sensor which is
in N
y

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.

29

Example


Altitude after initial phase

1
4
7
10
S1
S4
S7
S10
Exit

10x10 Grid Network

30

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


Introduction


System overview


Environment setting


Regular report


Emergency navigation service


Simulation results


Demonstration


Conclusion

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
Path
Pkt
.
count
Method of Li et al
.
Our method
(
D
=
2
)
3
No
Path
Pkt
.
count
A
A
979
252
1
1254
408
2
37

Outline


Introduction


System overview


Environment setting


Regular report


Emergency navigation service


Simulation results


Demonstration


Conclusion

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)

40

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
emergencies will disturb altitudes


altitude adjustment is designed for
quicker convergence


navigation in emergency applications requires
safer paths
, but
not 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

room

room

room

room

room

43

System Architecture

Controller
Sink
Control host
3
F
room
room
room
room
2
F
room
room
room
room
1
F
room
room
4
F
room
room
room
room
exit sensor
stair sensor
normal sensor
guidance direction
room
room
to rooftop
to rooftop
B
A
C
C
A
A
A
A
A
D
D
A
:
floor gateway
B
:
stair gateway
C
:
floor
/
stair gateway
D
:
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
)
(
l
emg
,
-
(
l
I
y
+
1
))
(
l
emg
,
-
(
l
I
y
+
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

3

F

room

room

room

room

2

F

room

room

room

room

1

F

room

room

4

F

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
hazardous 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
downstairs


47

Simulation results

1
F
3
F
2
F
4
F
1
F
3
F
2
F
4
F
1
F
3
F
2
F
4
F
1
F
3
F
2
F
4
F
1
F
3
F
2
F
4
F
1
F
3
F
2
F
4
F
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
Tree
Reconstruction
Deployment
GUI
Network
initialization
Guidance
initialization
Query
Sensor task
Guidance
service
Symmetric link
detection
Tree
maintenance
HELLO
Report
EMG
Application
-
level UI
Application
layer
Network
layer
Sensors part
Users part
Physical layer and Data link layer
Tree
Reconstruction
Sensor task
Guidance
service
Symmetric link
detection
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
EMG
stair
stair
stair


21
(
in dec
.)
50

Guidance UI

51

Demonstration


Environment


A virtual 2
-
store
building


Sink
Control
host
Exit
Exit
Exit
Exit
Stair
Stair
Stair
Stair
52

Demonstration


Vedio

53

More Results

2
F
1
F
Stair sensor
Exit sensor
Emergency
Guidance pkt
.
count
151
.
8
Tree Reconstruction pkt
.
count
7
.
6
Guidance pkt
.
count
237
.
8
Tree Reconstruction pkt
.
count
16
.
5
Guidance pkt
.
count
78
.
8
Tree Reconstruction pkt
.
count
4
.
8
(
a
)
(
b
)
(
c
)
3
F
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.