CenWits: A SensorBased Loosely Coupled Search and Rescue System Using Witnesses

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CenWits A Sensor-Based Loosely Coupled Search
and Rescue System Using Witnesses

• Jyh-How Huang
• Saqib Amjad
• Shivakant Mishra
• Department of Computer Science
• University of Colorado at Boulder

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Introduction

• Goal To build a search and rescue system that
  can pinpoint missing persons last seen point in
  wilderness areas
• Lost hikers, stranded climbers, injured skiers,
• Difficult because of lack of timely information
  about the current location
• Last seen point is critical for search and
  rescue actions

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A real case of last seen point
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Current Search and Rescue Technologies

• The Old School Way Ask
• Personal GPS receiver and Satellite transmitter
  Power greedy Must operate manually to send your
  location
• Localization system and GSM transmitter Need
  GSM network coverage
• Avalanche beacon/RFID reflector Limited usage

• Need a better, cheaper, reliable system

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Design Goals

• Self-Operate, long life time
• Small and light weight
• Non intrusive no infrastructure needed
• Power and memory efficient
• Cheap(2050)
• Meets security and privacy requirements

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Cenwits

• A Connection-less Sensor-Based Tracking System
  Using Witnesses
• Comprised of
• RF sensors
• GPS receivers
• Access points
• Location points
• Control center

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Cenwits How it Works (I)
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Cenwits How it Works (II)
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Cenwits How it Works (III)

• Hiker 6 is reported missing at
• 2359

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CenWits System Structure
Witness
Witness
Search Rescue Team
Control Center
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Current Loosely Coupled Systems

• ZebraNet
• At each scan for neighbors
• if node(I am) is within range of BS
• send data to BS and delete this data
• else send data to all neighbors

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Memory Management

• MAX RECORD COUNT
• Replace the old record with new one of the same
  node and keep the total records of a node less
  than MAX_RECORD_COUNT
• MAX HOP COUNT
• Dont forward a packet that has high probability
  of reaching AP already
• MIN RECORD GAP
• When 2 records are recorded in a time gap lt
  MIN_RECORD_GAP, replace the old one with new one.

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Energy Management
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More Memory Management
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Prototype Implementation

• MICA2 sensors
• 900 MHz 4 KB SDRAM 128 KB flash and 4-512 KB
  EEPROM
• Mantis OS 0.9.1b
• MTS420CA GPS module
• Successfully conducted a number of experiments in
  a indoor environment

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Experiment 1 (Direct Contact) One hiker starts
from A , goes to B and C, and returns to A
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Experiment 2 (Indirect Inference) Hiker 1 A to
B and beyond Hiker 2 Does not come in contact
with any AP Hiker 3 C to B and beyond
Path of hiker 2 is drawn successfully
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Hiker 1 to 5 walk on designated trails while
hiker 6 does a random walk. We successfully
depict path of hiker 6
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Conclusions

• CenWits has several advantages over other search
  and rescue systems
• No need for a connected network of any kind
• Power and storage efficiency
• Cost effective
• Non intrusive
• Suitable for deployment in wilderness areas
• Applications Hiking skiing wildlife
  monitoring vehicular network
• Future work
• Work with SAR team to deploy and test CenWits in
  a realistic environment
• Address security and privacy issues

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• Q?
• http//csel.cs.colorado.edu/huang/Cenwits/index.h
  tm
• huangjh,mishras_at_colorado.edu