Sensor Networks

1
Sensor Networks
Reference MOBICOM 2002 Tutorial T5 Wireless
Sensor Networks

• CSCI 6760
• Satya Sanket Sahoo

2
Outline

• Introduction
• Areas of Application
• The System
• Communications
• Deployment issues
• Energy
• Time Space
• Collaborations
• The Future

3
Introduction

• Chain Home - Britains Radar Network WWII
• Cold War
• SOSUS The Pacific Ocean
• NORAD Cheyenne Mountain
• National Power Grid
• Involves
• Devices with multiple sensors
• Network via wireless/physical links

4
Involved Technologies
Network Technology
Sensor Network
Computational Power
Sensor Technology
5
Application Areas

• Military
• Infrastructure security
• Environment Habitat Monitoring
• Industrial Sensing
• Traffic Control
• Seismic Studies
• Life Sciences

6
The Systems involved

• Sensor Node Internals
• Operating System
• Physical Size

7
Sensor Node Internals
CPU
INFRARED ACOUSTIC SEISMIC IMAGE MAGNETIC
POWER SUPPLY
ELECTRO-MAGNETIC INTERFACE
SENSOR
COMMUNICATION
NODE

• Some Current Node Platforms
• Sensoria WINS
• Smart Dust Dust Inc. Berkeley
• UC Berkeley mote Crossbow (www.xbow.com)

8
Operating System - TinyOS

• Custom built at UC, Berkeley for wireless sensor
  nodes
• Component-based architecture ensures minimum
  code size
• Component library includes
• Network protocols
• Sensor drivers
• Data acquisition tools
• Distributed services

9
Physical Size
WINS NG 2.0
Berkley Motes
AWAIRS I
LWIM III
AWACS
10
Communication

• Network Protocol
• Network Discovery
• Network Control Routing

11
Network Protocol

• For wireless sensor networks IEEE 802.11
  standards
• Personal Area Networks (PAN) IEEE 802.15
  standard
• Radius of 5 to 10m
• Ideal application in short-range sensors

12
Network Discovery

• Knowledge of identity and location of its
  neighbor
• For ad hoc networks
• Topology is built in real time
• Periodic updates sensors fail, new sensors
  added
• Global knowledge is generally not needed
• In the absence of GPS, relative positioning
  algorithms are used

13
Network Control Routing

• Network adapts dynamically to
• conserve resources like energy and available
  nodes
• Make optimum use of bandwidth and processing
  power
• Connectivity must emerge as needed from
  algorithms
• Directed Diffusion routing
• Data identity is separate from node identity
• Promotes adaptive, in-network processing

14
Deployment Issues

• Energy Issues
• Time and Space
• Collaboration towards Objective

15
Energy Issues

• Energy drains
• Energy Management

16
Energy Drains

• Processing
• Need for Idle sleep modes
• Variable voltage frequency
• Communications
• Currently around 150nJ/bit short range
• Sensors
• Depends on the sensing modality
• Actuators
• Power Supply

17
Energy Management

• Processor Energy management
• Shutdown
• Dynamic scaling of frequency and supply voltage
• dynamic scaling of frequency, supply voltage, and
  threshold voltage
• Communication Energy management
• Shutdown based
• Turn off sender and receiver

18
Time and Space

• Sensor node localization
• Temporal synching up
• Scale of operations

19
Localization

• Absolute position on geoid
• e.g. GPS
• Self-positioning vs. Remote-positioning
• Multiple techniques for Location sensing
• Measure proximity to landmarks
• Position relative to initialization point Dead
  reckoning
• Measure distance of landmarks - Ranging

20
Temporal Synchronization

• Reference-broadcast synchronization Very high
  precision sync with slow radios
• Post-facto synchronization syncs up only when
  needed (saves on energy)
• Peer-to-peer synchronization There are no master
  clocks
• Tiered Architecture Range of node capabilities

21
Scale Temporal and Spatial

• Sampling sampling frequency depends on
• Type of modality being measured
• Type of application
• Extent
• Density sensor nodes per footprint of input
  stimuli

22
Collaboration towards objective

• Requirements illustrative example
• CSP Collaborative Signal Processing

23
US Navy - TWMD
24
Collaborative Signal Processing

• Sensor nodes collaborate to extract and process
  information towards common objective
• Two types of collaboration
• Intra-node collaboration
• Inter-node collaboration

25
The Research Challenges

• Network deployment and organization
• Query processing and routing
• Storage management
• Increasing the longevity and robustness of the
  network
• Security issues
• Address privacy concerns

26
Reference

• Sensor networks Evolution, opportunities, and
  challenges Chee-Yee Chong S.P. Kumar
• Connecting the Physical World with Pervasive
  Networks Deborah Estrin, David Culler, and Kris
  Pister
• Sensor Networks Applications and Research
  Challenges Niki Trigoni Cornell University
• MOBICOM 2002 Tutorial T5 Wireless Sensor Networks
  Deborah Estrin Mani Srivastava
  destrin_at_cs.ucla.edu, mbs_at_ucla.edu UCLA Akbar
  Sayeed akbar_at_engr.wisc.edu University of
  Wisconsin, Madison