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Self-Organizing Wireless Sensor Networks in Action A Case Study

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Wireless Sensor Networks in Action A Case Study Jack Stankovic Computer Science University of Virginia Outline Pull everything together Type of summary Emphasize ... – PowerPoint PPT presentation

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Title: Self-Organizing Wireless Sensor Networks in Action A Case Study


1
Self-Organizing Wireless Sensor Networks in
Action A Case Study
Jack Stankovic

Computer Science University of Virginia
2
Outline
  • Pull everything together
  • Type of summary
  • Emphasize various new points
  • Really must build the system in real environments
  • Simple solutions (often) might be best
  • Interactions of solutions are very important
  • Fault Tolerance and Self-Healing
  • Classification
  • Issues with speed of targets, multiple targets
  • Scaling

3
Ad Hoc Wireless Sensor Networks
  • Sensors
  • Actuators
  • CPUs/Memory
  • Radio
  • Minimal capacity
  • 1000s

Self-organize
Reliable Abstraction
4
Mica2 and Mica2Dot
  • ATMega 128L 8-bit, 8MHz, 4KB EEPROM, 4KB RAM,
    128KB flash
  • Chipcon CC100 multichannel radio (Manchester
    encoding, FSK). Up to 500-1000ft.
  • Reality 50-100 feet when on the ground!

5
Sensor Board
6
VigilNet - Power Aware Surveillance
  • Acoustic
  • Magnetometer
  • Four 90 degree motion sensors
  • XSM motes - Crossbow

7
Requirements
  • Develop an operational self-organizing sensor
    network of size 1000 for rare event area
  • Cover an area of 1000m x 100m
  • Stealthy
  • Lifetime 3-6 months (with complicated system)
  • Timely detection, track and classification
  • Large or small vehicle
  • Person, person with weapon
  • Wakeup other devices when necessary
  • Extend the lifetime of those devices as well
  • Exhibit self-healing capabilities

8
VigilNet
  • Power Aware Surveillance Application
  • Field Test Scenarios and Overall Performance
  • Technical Details
  • Power Management - performance
  • Group Management - performance
  • Three Tier Filter and Classification Scheme
    performance
  • Walking GPS - performance

9
Energy Efficient Surveillance System
1. An unmanned plane (UAV) deploys motes
Zzz...
Sentry
2. Motes establish an sensor network with power
management
3. Sensor network detects vehicles and wakes up
the sensor nodes
10
Tripwire-based Surveillance
  • Self-organize (partition) sensor network into
    multiple sections (one per base station).
  • Turn off all the nodes in dormant sections.
  • Apply sentry-based power management in tripwire
    sections
  • Flexible scheduling, sections rotate to balance
    energy.

Road
11
Architecture Overview
12
Overview
  • Code
  • About 40,000 lines of code and 600 files
  • About 30 Middleware services provided
  • Operates with a network of 200 nodes over areas
    such as 500m x 50m
  • 10 Phases
  • MacDill AFB
  • Avon Park
  • Berkeley
  • UVA
  • Congress

13
Field Test Layout
300 meters, 30 motes each line, 4 non-uniform
lines
2
0
Tent
2 0 0 M
  • 200 XSM Motes
  • 3 Bases (Tripwires)
  • 300 by 200 Meters in T-shape
  • Inter-tripwire communication Via 802.11
    wireless LAN

1
14
Field Test Scenarios
  • Phase I Initialization (self organizing)
  • Multiple stages (7)
  • Each step time based (real-time bounds)
  • No massive acknowledgements
  • Re-initialize periodically rotation
  • Self-healing
  • Power load balancing
  • Understand status of network

15
Time-Driven System Operation
16
Results of Actual Test
17
Field Test Scenarios
  • Phase II Track and Classify Persons
  • Person walking, running and walking again
  • Compute velocity
  • Phase III Tracking and Classify Vehicles at
    various speeds
  • 10 mph
  • 20 mph
  • 30 mph
  • 50 mph

18
Field Test System Layout
300 meters, 30 motes each line, 4 non-uniform
lines
A
C
B
0
Tent
2 0 0 M
  • 200 XSM Motes
  • 1 Base (Tripwire)
  • 300 by 200 Meters in T-shape

D
19
Field Test Scenarios
  • Phase IV Tracking multiple targets (people,
    vehicles, and then people and vehicles)
  • 3 crossing people
  • Vehicle followed by person
  • 2 vehicles following each other about 50 meters
    apart

20
Field Test Layout
300 meters, 30 motes each line, 4 non-uniform
lines
A
C
B
0
Tent
2 0 0 M
  • 200 XSM Motes
  • 1 Base (Tripwire)
  • 300 by 200 Meters in T-shape

D
21
Field Test Scenarios
  • Phase V Tripwire Partitions Created
  • Set system parameters
  • Activate 2 additional base stations
  • Reset system (a rotation)

22
Results of Actual Test
23
Field Test Scenarios
  • Phase VI - Activate and Deactivate tripwire
    sections
  • Phase VII Tracking with multiple tripwires
  • Person in dormant zone not detected then moves
    into active zone
  • Person first in active zone and moves into
    dormant zone
  • Vehicle at 30 mph

24
Field Test Scenarios
  • Phase VIII Fault Tolerance with base mote
    failure
  • Turn off base mote 2
  • Rotate system
  • Nodes all reconfigure into 2 zones
  • Phase IX Fault Tolerance with mote failures
  • For all above tests about 15 of nodes were dead
  • Turned off an additional 12 motes all near the T
    intersection
  • Vehicle at 30mph
  • Person
  • Phase X activate remote IR cameras and
    exfiltrate data to command and control center via
    satellites

25
High Level Performance
  • All tests worked correctly
  • False Alarms
  • No false positives
  • 1 False negative
  • A few times classified a person as a vehicle
  • High Wind

26
Technical Details
  • Two sets of motes on either side of the path.
  • One node at the end designated as the base node.

27
Neighbor Discovery
  • Every node periodically broadcasts HELLO
    messages.
  • Communication at sensing range.

Asymmetric Detection Protocol
28
Reality - Radio Irregularity
Radio Communication Range
29
Impact on Routing
  • Impact on
  • Path-Reversal technique
  • Multi-Round technique
  • Used in AODV, DSR, LAR

Route Discovery Using Multi-Round Technique
30
Asymmetric Detection Protocol
  • Explicit asymmetric communication detection and
    then use in routing protocol
  • Adapt over time and/or as conditions change
  • Such a solution in VigilNet
  • Exchange neighbor tables
  • Im in your table and your in mine -gt symmetric
    link
  • Retry multiple times for statistical result

31
Tripwire-based Surveillance
  • Create tripwires
  • Nodes attach to nearest base station based on
    distance (not hops)
  • One per base station

Road
32
Sentry-Based Power Management (SBPM)
  • Two classes of nodes sentries and non-sentries
  • Sentries are awake
  • Non-sentries can sleep
  • Sentries
  • Provide coarse monitoring backbone
    communication network
  • Sentries wake up non-sentries for finer
    sensing
  • Sentry rotation
  • Even energy distribution
  • Prolong system life

33
SBPM - Illustration
  • Sentry Declaration Phase
  • Communication at sensing range.

34
SBPM - Illustration
  • Sentry Declaration Phase
  • Other nodes send SENTRY_DECLARE message as
    backoff expires (function of remaining energy).

35
SBPM - Illustration
  • Sentry Declaration Phase
  • Other nodes send SENTRY_DECLARE message as
    backoff expires.

36
SBPM - Illustration
  • Backbone Creation
  • Flooding initiates at base.

37
SBPM - Illustration
  • Build spanning tree.

38
SBPM - Illustration
  • Final result might look like this.

Build second parent tree for robustness
39
SBPM - Illustration
  • Backbone Repair

40
Area Only Wake-Up
  • Power management non-sentries go to sleep
  • Upon detection of event all non-sentries in an
    area are awakened.

Non-sentry powered-on Non-sentry powered-off
Sentry
41
Power Management
  • Sentry
  • Tripwire
  • Area only wakeup

42
Lifetime Analysis
Network Life Time Number of Tripwires (10 regions, 30 sentry, 7 day life) Number of Tripwires (10 regions, 30 sentry, 7 day life) Number of Tripwires (10 regions, 30 sentry, 7 day life) Number of Tripwires (10 regions, 30 sentry, 7 day life)
4 3 2 1

2 AA Batteries 50 days 70 days 105 days 210 days

4 AA Batteries 100 days 140 days 210 days 420 days
43
Sentry Duty-Cycle Scheduling
  • A common period p and duty-cycle ß is chosen for
    all sentries, while starting times Tstart are
    randomly selected

Non-sentries
Sentries
A
t
B
t
Target Trace
C
A
D
t
E
D
C
t
B
E
t
p
0
2p
Sleeping
Awake
44
Lifetime Analysis
Network Life Time Number of Tripwires (10 regions, 30 sentry, 7 day life) Number of Tripwires (10 regions, 30 sentry, 7 day life) Number of Tripwires (10 regions, 30 sentry, 7 day life) Number of Tripwires (10 regions, 30 sentry, 7 day life)
10 4 2 1
2 AA Batteries Sentries Awake 21 days 50 days 105 days 210 days
2 AA Batteries Sentries with Duty Cycles 50 days 125 days 250 days 500 days
4 AA Batteries Sentries Awake 42 days 100 days 210 days 420 days
4 AA Batteries Sentries with Duty Cycles 100 days 250 days 500 days 1000 days
45
Group Management
IR Camera
  • Leader
  • Follower
  • Member
  • Node

46
Group Management
IR Camera
  • Leader
  • Follower
  • Member
  • Node

47
Detection/Classification/Velocity Delay
DETECTION DELAY (S) CLASSIFICATION DELAY (S) VELOCITY DELAY (S) REPORTED VELOCITY (MPH) ACTUAL VELOCITY (MPH)
2.7 3.2 3.2 25.0/10.9 N/A
1.8 3.2 3.2 24.6 N/A
1.7 2.7 3.2 17.6 N/A
3.8 4.8 5.3 9.3 N/A
1.7 2.7 2.8 11.1 10
2.6 3.1 3.6 18.5 20
1.9 2.4 2.4 23.0 20
2.6 2.9 3.2 12.7 12
0.9 2.5 2.5 22.1 20
4.5 8.1 8.1 6.2 N/A
48
Sensing Realities
  • Sensor fusion
  • Handle noise, missing reports, drift,
    environmental conditions, characteristics of
    sensors, etc.
  • Compute confidence
  • Minimize false alarms
  • On minimum capacity devices (but utilize multiple
    devices)

49
3 -Tier Filter Classification
50
Acoustic Sensing
Three Cars
Initial Calibration No Detection
Detection when Energy Crosses Standard Deviation
51
Second Tier Group Aggregation
DOA controls minimal aggregation degree to reduce
false alarms
Node Member Follower Leader
Awareness Range
52
System Issues False alarms
Impact of DOA on False Alarms
  • Probability of false positives
  • reduces as DOA increases
  • Probability of false negatives
  • increases as DOA increases
  • With DOA 3 we had zero false
  • alarms
  • The DOA parameter can be tuned
  • based on sensing range and the
  • density with which motes are
  • deployed

Spatial-temporal correlated data aggregation can
effectively reduce false alarms
53
THIRD TIER
  • At base station
  • Maintain history of track
  • Further reduce false alarms by checking for
    anomalies
  • Compute velocity
  • Perform classification

54
Localization Walking GPS
  • GPS Mote assembly
  • Garmin eTrex Legend GPS device (WAAS enabled)
  • MICA2 mote
  • helmet, RS232 cable, board, wristband
  • Memory size 17 Kbytes (code), 600 Bytes (data)
  • Sensor Node
  • Mica2, XSM
  • Memory 1 Kbytes (code), data 120 bytes

55
Walking GPS Evaluation
  • First deployment type sensor motes turned on at
    the place of deployment, right before being
    deployed
  • Localization error 0.8 meters
  • Standard deviation 0.5 meters
  • Second deployment type sensor motes turned on
    all the time.
  • Localization error 1.5 meters
  • Standard deviation 0.8 meters

56
Summary
  • Surveillance Application in Action
  • One message must build complete systems and use
    them in realistic settings with real world
    realities
  • 30 modules synthesized a complete system
  • Scale via tripwires
  • Robust to faults
  • Novel technology
  • Power management
  • Group management
  • Asymmetric communication detection
  • Simple localization based on manual deployment
    but it works
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