Ad Hoc Networks

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Wireless Sensor Network Prabhakar Dhekne Bhabha
Atomic Research Centre
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Why Talk About Wireless?

• Wireless communication is not a new technology
  but cell phones have brought revolution in
  wireless communication
• Wireless Technology has changed the way
• Organizations individuals work live today
• In less than 10 years
• World has moved from fixed to wireless networks
• Allowing people, mobile devices computers talk
  to each other, connect without a cable
• Only available option for field data acquisition
• Interconnectivity with multiple devices
• Using radio-waves, sometimes light
• Frees user from many constrains of traditional
  computer phone system

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Ubiquitous Computing

• Future State of Computing Technology?
• Mobile, many computers
• Small Processors
• Low Power Consumption
• Relatively Low Cost

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Ubiquitous Computing

• Small, mobile, inexpensive computers..everywhere!
  
• Fade into the background of everyday life
• Computers everywhere provides potential for data
  collection.sensors!
• Temperature
• Light
• Sound
• Motion
• Pressure
• Many others!!!

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Growth in Wireless Systems

• Rapid growth in cellular voice services
• Cell phones everywhere!
• Several wireless technology options have been
  available for the last 10-20 yrs
• mini cell stations using existing standards like
  CDMA or GSM
• wireless PABX using PCS standards such as DECT or
  PHS/PACS
• satellite and microwave backhaul
• Above solutions OK for voice low-speed data,
  but do not meet emerging needs for broadband
  access and mobile data

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Mobile Computing

• Identify/develop mobile computing solutions and
  effector systems integrated with existing
  wireless infrastructure
• Improve health care via enhanced training and
  more effective decision making
• To maximize the amount of medical data available
  for health surveillance

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Mobile Healthcare Technologies

• Mobile Healthcare can be regarded as the
  integration of technologies of medical sensors,
  mobile computing, and wireless communications
  into a system of medical assistance.

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Application Examples

• Monitoring of patients vital signs
• Diabetes
• Asthma
• Hypertension
• ECG
• Predictive usage in order to minimize the needs
  for medication
• Improving the quality of life

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Potential Benefits

• Increasing the physician productivity and
  efficiency.
• Wireless sensors enable the patients freedom of
  movements and therefore promote new ways of
  monitoring the patient.
• Providing clinicians remote access to patients
  information eliminates the need to manually
  locate and search through patients data.
• Enabling telemonitoring in emergency scenarios
  and making remote diagnosis possible.

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Mobile Healthcare

• The provision of Real Time patient care.
• No matter where the clinician is
• No matter where the patient is
• To apply physiological and medical knowledge,
  advanced diagnostics, simulations, and effector
  systems integrated with information and
  telecommunications for the purposes of enhancing
  operational and medical decision-making,
  improving medical training, and delivering
  medical treatment across all barriers

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Typical Demo System

• The patient is provided with a wearable wireless
  sensor. The signal from the sensor is captured in
  a Node situated in a mobile phone.
• The system allows ubiquitous access to patients
  data and medical information in real-time via the
  mobile phone.
• The medical data is stored processed in a
  server, and can be used for establishing
  diagnostics and treatments.

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Application server

• Application server centralises the received data
  and presents it to the user as
• Raw data
• Formatted as graphs

App Server
DB
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Wireless Technology

• Emerging mainstream wireless technologies provide
  powerful building blocks for next-generation
  applications
• WLAN (IEEE 802.11 WiFi) hot-spots for broadband
  access, Bluetooth
• PDAs and laptops with integrated WLANs
• Broadband Wireless access technology- MAN
  (Alternative to DSL)
• IEEE 802.16 10-30 Km 40 Mbps WiMax
• Wide area wireless data also growing
• SMS, GPRS, Edge, CDMA2000 1xEV-DO (2.4 Mbps data
  optimized)
• Variety of interesting devices (e.g. Treo,
  Sidekick)
• Networking of embedded devices
• Smart spaces, sensor networks (IEEE 802.15.4a-
  ZigBee)
• Context-aware mobile data services and web
  caching for information services
• Wireless sensor nets for monitoring and control
• VOIP for integrated voice services over wireless
  data networks

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IrDA P2P wireless

• Infra-red Data Association
• Based on Half Duplex Point-to-Point concept
• Frequency below the red end of spectrum making it
  invisible
• Eliminate the need for cables
• Clear line-of-sight
• Short-range (few meters)
• Simplest, most prevailing wireless standard
• No fixed speed 9.6 Kbps, 4Mbps
• Discovery Mode to find out data rate, size
• Token based transmission
• IrDA ports on PDA, Laptops USB sticks
• Remote Control in TV, VCR, Air-conditioner

Port costs less than Rs. 1000
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Bluetooth Wireless PAN

• Bluetooth (Named after Danish King Harold
  Bluetooth)
• Based on Master-Slave concept
• Short-range (10 meters)
• Eliminate the need for cables
• Operates in 2.4 GHz ISM band
• 720 Kbps
• Three modes of operation park/hold/sniff
• Piconet Scatternet (master7 slaves)
• Interference due to multiple piconets and IEEE
  802.15.1 home/person LAN
• To eliminate interference frequency hoping
  technique used
• Ominidirectional with both voice data

M1
S2
S1
S1
S2
M 1/S1
Piconet 1
Piconet 2
Port costs about Rs. 2000
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Wi-Fi Wireless LAN (Hot Spot)

• Wireless Fidelity based LAN
• Most popular on Laptops
• Replacement to wired LAN
• Connectivity on the move
• Short-range (100 meters)
• Ad Hoc and Base station mode
• Security provided at physical layer
• Operates in 2.4 GHz and 5 GHz
• Collection of IEEE standards 802.11a/b/g 11 Mpbs
  54 Mbps
• Low range, requires more power hence not suitable
  for PDAs
• Difficult to control access security
• Set up is expensive

Ad Hoc Net
Access Point Net
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Wi-Max Wireless MAN

• Wireless Max
• High Speed 40-70 Mbps
• Mid-range (30 Kmeters)
• Eliminate the need for cables
• Saving of wired cost
• Operates in 2.4 GHz ISM band
• IEEE standard 802.16

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Issues in Wireless Networking

• Infrastructured networks
• Handoff
• location management (mobile IP)
• channel assignment

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Issues in Wireless Networking

• Infrastructureless networks
• Wireless MAC
• Security (integrity, authentication,
  confidentiality)
• Ad Hoc Routing Protocols
• Multicasting and Broadcasting

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Indoor Environments

• Three popular technologies
• - High Speed Wireless LANs (802.11b (2.4GHz, 11
  Mbps), 802.11a (5GHz, 54 Mbps higher)
• - Wireless Personal area Networks PANs (IEEE
  804.14)
• HomeRF
• Bluetooth, 802.15
• - Wireless device networks
• Sensor networks, wirelessly networked robots

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What is an Ad hoc Network

• Collection of mobile wireless nodes forming a
  network without the aid of any infrastructure or
  centralized administration
• Nodes have limited transmission range
• Nodes act as a routers

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Ad Hoc Networks

• Disaster recovery
• Battlefield
• Smart office

• Rapidly deployable infrastructure
• Wireless cabling impractical
• Ad-Hoc no advance planning
• Backbone network wireless IP routers

• Network of access devices
• Wireless untethered
• Ad-hoc random deployment
• Edge network Sensor networks, Personal Area
  Networks (PANs), etc.

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Ad Hoc Network

• Characteristics
• Dynamic topologies
• Limited channel bandwidth
• Variable capacity links
• Energy-constrained operation
• Limited physical security
• Applications
• Military battlefield networks
• Personal Area Networks (PAN)
• Disaster and rescue operation
• Peer to peer networks

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Security Challenges in Ad Hoc Networks

• Lack of Infrastructure or centralized control
• Key management becomes difficult
• Dynamic topology
• Challenging to design sophisticated secure
  routing protocols
• Communication through Radio Waves
• Difficult to prevent eavesdropping
• Vulnerabilities of routing mechanism
• Non-cooperation of nodes
• Vulnerabilities of nodes
• Captured or Compromised

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Security

• Challenges in ad hoc network security
• The nodes are constantly mobile
• The protocols implemented are co-operative in
  nature
• There is a lack of a fixed infrastructure to
  collect audit data
• No clear distinction between normalcy and anomaly
  in ad hoc networks
• Secure the Routing Mechanism
• A mechanism that satisfies security attributes
  like authentication, confidentiality,
  non-repudiation and integrity
• Secure the Key Management Scheme
• Robust key certification and key distribution
  mechanism

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Scalable, reliable, consistent, distributed
service
Services while on move
services
Sensor services exercise monitorbiometrics
traffic information
Calendar service Integrate dynamic traffic
schedule Doctor prescription servicetrack health
indicatorsDoctor write prescription Follow me
kiosk service receive and transmit
messages Fridge shopping serviceFridge records
stockSuggests shopping based on recipeShopping
guide in store
Sensors mobile devices
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Tourist guide

• Stuttgart tourist guide
• Like MapQuest except on mobile device
• Mapping local interests
• Museums historical sites
• Shopping restaurants Sample Data
• Small text with description, operating hours
• Local map

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How it works

• Info station
• Island of wireless station
• Embedded in area
• Users have cheap low bandwidth components
• Integrated to network with high quality
  connection
• Requires some overlap to manage transition
  between stations for hand off
• Scaleable by load balancing
• Each center contains unique information
• Overhead of communication
• Initialize externally specified adjusts quickly

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Map-on-the-move

• Provide appropriate map
• County resolution driving in car
• Info stations small area high bandwidth
• Remainder lower bandwidth

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Problems in a Mobile Environment

• Variable Bandwidth
• Disconnected Operation
• Limited Power
• Implications on distributed file system support?

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Constraints in mobile computing

• PDA vs. Laptop vs. cell phones
• Cellular modem connection Failure prone
• Space office vs. city vs. county
• Not continuous connectivity required
• Data such as pictures text files not streaming
  audio and video
• Heterogeneous devices

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MANET Mobile Ad hoc Networks
A collection of wireless mobile nodes dynamically
forming a network without any existing
infrastructure and the relative position dictate
communication links (dynamically changing).
From DARPA Website
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Rapidly Deployable Networks

• Failure of communication networks is a critical
  problem faced by first responders at a disaster
  site
• major switches and routers serving the region
  often damaged
• cellular cell towers may survive, but suffer from
  traffic overload and dependence on (damaged)
  wired infrastructure for backhaul
• In addition, existing networks even if they
  survive may not be optimized for services needed
  at site
• significant increase in mobile phone traffic
  needs to be served
• first responders need access to data services
  (email, www,...)
• new requirements for peer-to-peer communication,
  sensor net or robotic control at the site
• Motivates need for rapidly deployable networks
  that meet both the above needs -gt recent advances
  in wireless technology can be harnessed to
  provide significant new capabilities

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Infostations Prototype System for Rapid
Deployment Applications

• Outdoor Infostations with radio backhaul
• for first responders to set up wireless
  communications infrastructure at a disaster site
• provides WLAN services and access to cached data
• wireless backhaul link
• includes data cache
• Project for development of
• high-speed short-range radios
• 802.11 MAC enhancements
• content caching algorithm software
• hardware integration including solar panels,
  antennas and embedded computing device with WLAN
  card

WINLABs Outdoor Infostations Prototype (2002)
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Ad-Hoc Wireless Network

• A flexible, open-architecture ad-hoc WLAN and
  sensor network testbed ...
• open-source Linux routers, APs and terminals
  (commercial hardware)
• Linux and embedded OS forwarding and sensor nodes
  (custom)
• radio link and global network monitoring/visualiza
  tion tools
• prototype ad-hoc discovery and routing protocols

802.11b PDA
Management stations
Radio Monitor
802.11b Linux PC
Forwarding Node/AP (custom)
AP
Commercial 802.11
Router network with arbitrary topology
Compute storage servers
Sensor Node (custom)
PC-based Linux router
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What is a WSN?
Observer The end user/computer
Sensor The device
Phenomenon The entity of interest to the observer

• A network that is formed when a set of small
  sensor devices that are deployed in an ad hoc
  fashion no predefined routes, cooperate for
  sensing a physical phenomenon.
• A Wireless Sensor Network (WSN) consists of base
  stations and a number of wireless sensors.
• Is simple, tiny, inexpensive, and battery-powered

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Why Wireless Sensors Now?

• Moores Law is making sufficient CPU performance
  available with low power requirements in a small
  size.
• Research in Materials Science has resulted in
  novel sensing materials for many Chemical,
  Biological, and Physical sensing tasks.
• Transceivers for wireless devices are becoming
  smaller, less expensive, and less power hungry
  (low power tiny Radio Chips).
• Power source improvements in batteries, as well
  as passive power sources such as solar or
  vibration energy, are expanding application
  options.

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Typical Sensor Node Features

• A sensor node has
• Sensing Material
• Physical Magnetic, Light, Sound
• Chemical CO, Chemical Weapons
• Biological Bacteria, Viruses, Proteins
• Integrated Circuitry (VLSI)
• A-to-D converter from sensor to circuitry
• Packaging for environmental safety
• Power Supply
• Passive Solar, Vibration
• Active Battery power, RF Inductance

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Sensor Node Hardware
Sensor Actuator ADC Microprocessor
Powering Unit Communication Unit (RF
Transceiver) GPS

• Portable and self-sustained (power,
  communication, intelligence).
• Capable of embedded complex data processing.

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Sensors and Wireless Radio

• Types of sensors
• -Pressure,
• -Temperature
• -Light
• -Biological
• -Chemical
• -Strain, fatigue
• -Tilt
• Capable to survive harsh environments (heat,
  humidity, corrosion, pollution etc).
• No source of interference to systems being
  monitored and/or surrounding systems.
• Could be deployed in large numbers.

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Wireless Sensor Networks

• ZigBee Wireless Communication Protocol
• Based on the IEEE 802.15.4 standard
• Small form factor
• Relatively Inexpensive
• Low Power Consumption
• Low Data Rate of Communication
• Self Organising, Self-Healingmulti-hop nodes
• Integrated Sensors
• Ideal for Wireless Sensor Network Applications

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WSN APPLICATIONS

• Potential for new intelligent applications
• Smart Homes
• Process monitoring and control
• Security/Surveillance
• Environmental Monitoring
• Construction
• Medical/Healthcare
• Implemented with Wireless Sensor Networks!

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Medical and Healthcare Appln
Remote Databases
Backbone Network
Net Switch
In Hospital Physician
Net Switch
Wireless Remote consultation
Possibility for Remote consulting (including
Audio Visual communication)
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Medical and Healthcare Applications
Sensors equipped with BlueTooth
Source USC Web Site
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iBadge - UCLA

• Investigate behavior of children/patient
• Features
• Speech recording / replaying
• Position detection
• Direction detection / estimation (compass)
• Weather data Temperature, Humidity, Pressure,
  Light

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Other Examples

• MIT d'Arbeloff Lab The ring sensor
• Monitors the physiological status of the wearer
  and transmits the information to the medical
  professional over the Internet
• Oak Ridge National Laboratory
• Nose-on-a-chip is a MEMS-based sensor
• It can detect 400 species of gases and transmit a
  signal indicating the level to a central control
  station
• VERICHIP Miniaturised, Implanted, Identification
  Technology

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Structural Health Monitoring
Accelerometer board prototype, Ruiz-Sandoval,
Nagayama Spencer, Civil E., U. Illinois
Urbana-Champaign
Semi-active Hydraulic Damper (SHD), Kajima
Corporation, Japan
Model bridge with attached wireless sensors, B.F.
Spencers Lab, Civil E., U. Illinois U-C
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Application in Environment Monitoring

• Measuring pollutant concentration
• Pass on information to monitoring station
• Predict current location of pollutant volume
  based on various parameters
• Take corrective action

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Vehicular Traffic Control
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VMesh Distributed Data Sensing, Relaying,
Computing via Vehicular Wireless Mesh Networks
Project at The University of California, Davis
US FCC allocated 5.850 to 5.925 GHz dedicated
short range communication (DSRC) Road side to
Vehicle Vehicle to vehicle communication
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Network characteristics of WSN

• Generally, the network
• Consists of a large number of sensors (103 to
  106)
• Spread over large geographical region (radius 1
  to 103 km)
• Spaced out in 1, 2, or 3 dimensions
• Is self-organizing
• Uses wireless media
• May use intermediate collators

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Sensor Network Topology

• Hundreds of nodes require careful handling of
  topology maintenance.
• Predeployment and deployment phase
• Numerous ways to deploy the sensors (mass,
  individual placement, dropping from plane..)
• Postdeployment phase
• Factors are sensor nodes position change,
  reachability due to jamming, noise, obstacles
  etc, available energy, malfunctioning, theft,
  sabotage
• Redeployment of additional nodes phase
• Redeployment because of malfunctioning of units

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Organization into Ad Hoc Net

• Individual sensors are quite limited.
• Full potential is realized only by using a large
  number of sensors.
• Sensors are then organized into an ad hoc
  network.
• Need efficient protocols to route and manage data
  in this network.

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Network Topologies

• Star
• Single Hop Network
• All nodes communicate directly with Gateway
• No router nodes
• Cannot self-heal
• Range 30-100m
• Consumes lowest power

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Network Topologies

• Mesh
• Multi-hopping network
• All nodes are routers
• Self-configuring network
• Node fails, network self-heals
• Re-routes data through shortest path
• Highly fault tolerant network
• Multi-hopping provides much longer range
• Higher power consumptionnodes must always
  listen!

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Network Topologies

• Star-Mesh Hybrid
• Combines of stars low power and
• meshs self-healing and longer range
• All endpoint sensor nodes can communicate with
  multiple routers
• Improves fault tolerance
• Increases network communication range
• High degree of flexibility and mobility

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Self-Organizing WLAN

• Opportunistic ad-hoc wireless networking concepts
  starting to mature
• Initial use to extend WLAN range in user-deployed
  networks
• Based on novel auto-discovery and multi-hop
  routing protocols
• extends the utility and reach of low-cost/high
  speed WiFi equipment

Wired Network Infrastructure
AP1
AP2
802.11 Access to AP
Ad-hoc radio link (w/multi-hop routing
Ad-hoc Infrastructure links
Ad-hoc access To FN
Forwarding Node (FN)
Mobile Node (MN) (end-user)
Forwarding Node (FN)
Self-organizing Ad-hoc WLAN
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How to get information from Data-centric Sensor
Networks?

• Types of Queries
• Historical Queries Analysis of data collected
  over time
• One Time Queries Snapshot view of the network
• Persistent Queries Periodic monitoring at long
  and regular intervals
• Routing required to respond to a Query
• Application specific
• Data centric
• Data aggregation capability desirable
• Need to minimize energy consumption

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Software Framework
MAC layer (Tiny OS, routing) Configuration
Table Power consumption status replacement
strategy Sensor Data Management Middleware Applica
tion (passing parameters via API)
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Technical challenges

• Sensor design
• Self-organizing network, that requires
  0-configuration of sensors
• Random or planned deployment of sensors, and
  collators
• Auto-addressing
• Auto-service discovery
• Sensor localization

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Power Consumption

• Limited Power Source
• Battery Lifetime is limited
• Each sensor node plays a dual role of data
  originator and data router (data processor)
• The malfunctioning of a few nodes consumes lot of
  energy (rerouting of packets and significant
  topological changes)

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Environmental Factors

• Wireless sensors need to operate in conditions
  that are not encountered by typical computing
  devices
• Rain, sleet, snow, hail, etc.
• Wide temperature variations
• May require separating sensor from electronics
• High humidity
• Saline or other corrosive substances
• High wind speeds

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Historical Comparison
Consider a 40 Year Old Computer
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Advances in Wireless Sensor Nodes

• Consider Multiple Generations of Berkeley Motes

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Summary

• Sensor networks will facilitate one to address
  several societal issues
• Early-warning systems
• Disaster mitigation
• Applications in other sectors
• Security, transportation, irrigation
• Technology is available today
• Research into new sensors
• Needs experimentation, pilot deployment
• Lots needs to be done in Software (OS, MAC,
  Application)
• While cost is an issue today, it will not be so
  tomorrow

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References

• Wireless Mobile Systems Prof Dharma Prakash
  Agrawal and H. Deng
• Integrating Wireless Technology in the Enterprise
  by Williams Wheeler, Elsevier Digital Press
• Circuits Systems for Wireless Communications
  Edited by Markus Helfenstein and George S.
  Moschytz, Kluwer Academic Publishers

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Any Questions?