Transcript Ad Hoc Networks - SASTRA University

Wireless Sensor Network
Prabhakar Dhekne
Bhabha Atomic Research Centre
August 24, 2006
Talk at SASTRA
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Why Talk About Wireless?
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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
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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
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Using radio-waves, sometimes light
Frees user from many constrains of traditional computer & phone system
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Ubiquitous Computing
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Future State of Computing Technology?
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Mobile, many computers
Small Processors
Low Power Consumption
Relatively Low Cost
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Ubiquitous Computing
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Small, mobile, inexpensive computers…..everywhere!
Fade into the background of everyday life
Computers everywhere provides potential for data
collection….sensors!
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Temperature
Light
Sound
Motion
Pressure
Many others!!!
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Growth in Wireless Systems
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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 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
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Monitoring of patient’s vital signs
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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
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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 patient’s
information eliminates the need to manually
locate and search through patient’s data.
Enabling
telemonitoring
in
emergency
scenarios and making remote diagnosis
possible.
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Mobile Healthcare
The provision of Real Time patient care.
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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
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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
patient’s 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
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Application
server
centralises
the
received data and presents it to the user
as:
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Raw data
Formatted as graphs
App Server
DB
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Wireless Technology
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Emerging mainstream wireless technologies provide powerful building blocks for
next-generation applications
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WLAN (IEEE 802.11 “WiFi”) hot-spots for broadband access, Bluetooth
 PDAs and laptops with integrated WLANs
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Broadband Wireless access technology- MAN (Alternative to DSL)
 IEEE 802.16 10-30 Km 40 Mbps WiMax
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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
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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
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Infra-red Data Association
Based on Half Duplex Point-to-Point concept
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Frequency below the red end of spectrum
making it invisible
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Eliminate the need for cables
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Clear line-of-sight
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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
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Port costs less than Rs. 1000
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Bluetooth: Wireless PAN
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Bluetooth (Named after Danish King
Harold Bluetooth)
Based on Master-Slave concept
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Short-range (10 meters)
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Eliminate the need for cables
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Operates in 2.4 GHz ISM band
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720 Kbps
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Three modes of operation park/hold/sniff
Piconet & Scatternet (master+7 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
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M1
S1
S1
S2
M 1/S1
Piconet 1
S2
Piconet 2
Port costs about Rs. 2000
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Wi-Fi: Wireless LAN (Hot Spot)
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Wireless Fidelity based LAN
Most popular on Laptops
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Replacement to wired LAN
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Connectivity on the move
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Short-range (100 meters)
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Ad Hoc and Base station mode
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Security provided at physical layer
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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 PDA’s
Difficult to control access & security
Set up is expensive
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Ad Hoc
Net
Access
Point Net
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Wi-Max: Wireless MAN
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Wireless Max
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High Speed 40-70 Mbps
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Mid-range (30 Kmeters)
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Eliminate the need for cables
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Saving of wired cost
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Operates in 2.4 GHz ISM band
IEEE standard 802.16
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Issues in Wireless Networking
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Infrastructured networks
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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
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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
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Sensor networks, wirelessly networked robots
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What is an Ad hoc Network
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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
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Disaster recovery
Battlefield
‘Smart’ office
Rapidly deployable
infrastructure
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Wireless: cabling
impractical
Ad-Hoc: no advance
planning
Backbone network:
wireless IP routers
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Network of access devices
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Wireless: untethered
Ad-hoc: random deployment
Edge network: Sensor networks,
Personal Area Networks (PANs), etc.
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Ad Hoc Network
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Characteristics
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Dynamic topologies
Limited channel bandwidth
Variable capacity links
Energy-constrained operation
Limited physical security
Applications
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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
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Lack of Infrastructure or centralized control
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Dynamic topology
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Difficult to prevent eavesdropping
Vulnerabilities of routing mechanism
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Challenging to design sophisticated & secure routing
protocols
Communication through Radio Waves
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Key management becomes difficult
Non-cooperation of nodes
Vulnerabilities of nodes
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Captured or Compromised
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Security
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Challenges in ad hoc network security
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Secure the Routing Mechanism
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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
A mechanism that satisfies security attributes like authentication,
confidentiality, non-repudiation and integrity
Secure the Key Management Scheme
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Robust key certification and key distribution mechanism
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Services while on move
services
Sensor services
exercise monitor
biometrics
traffic information
Calendar+ service
Integrate dynamic traffic & schedule
Doctor prescription service
track health indicators
Doctor write prescription
Sensors
mobile devices
Scalable, reliable, consistent,
Follow me kiosk service
receive and transmit messages
Fridge & shopping service
Fridge records stock
Suggests shopping based on recipe
Shopping guide in store
distributed service
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Tourist guide
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Stuttgart tourist guide
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Like MapQuest except on mobile
device
Mapping local interests
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Museums historical sites
Shopping & restaurants Sample Data
Small text with description, operating
hours
Local map
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How it works
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Info station
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Scaleable by load balancing
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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
Each center contains unique information
Overhead of communication
Initialize externally specified; adjusts quickly
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Map-on-the-move
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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
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Variable Bandwidth
Disconnected Operation
Limited Power
Implications on distributed file
system support?
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Constraints in mobile
computing
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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
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Failure of communication networks is a critical problem
faced by first responders at a disaster site
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In addition, existing networks even if they survive may not
be optimized for services needed at site
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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
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 -> recent advances in wireless technology
can be harnessed to provide significant new capabilities
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Infostations Prototype: System for
Rapid Deployment Applications
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Outdoor Infostations with
radio backhaul
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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:
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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
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WINLAB’s Outdoor Infostations Prototype (2002)
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Ad-Hoc Wireless Network
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A flexible, open-architecture ad-hoc WLAN and sensor network
testbed ...
 open-source Linux routers, AP’s and terminals (commercial
hardware)
 Linux and embedded OS forwarding and sensor nodes (custom)
 radio link and global network monitoring/visualization tools
 prototype ad-hoc discovery and routing protocols
802.11b
PDA
Management
stations
Radio Monitor
AP
Forwarding Node/AP
(custom)
802.11b
Linux PC
Commercial
802.11
Router network
with arbitrary topology
Compute
& storage
servers
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PC
PC-based
Linux router
Sensor Node
(custom)
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What is a WSN?
Sensor: The device
Observer: The end user/computer
Phenomenon: The entity of interest to the observer
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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?
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Moore’s 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
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A sensor node has:
 Sensing Material
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Integrated Circuitry (VLSI)
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Physical – Magnetic, Light, Sound
Chemical – CO, Chemical Weapons
Biological – Bacteria, Viruses, Proteins
A-to-D converter from sensor to circuitry
Packaging for environmental safety
Power Supply
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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
Transceiver
128Kb-1Mb
Limited Storage
1Kbps- 1Mbps
3m-300m
Lossy Transmission
Memory
Embedded
Processor
Requires
Supervision
Multiple sensors
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8 bit, 10 MHz
Slow Computation
Sensor
Battery
Limited Lifetime
Portable and self-sustained (power, communication,
intelligence).
Capable of embedded complex data processing.
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Sensors and Wireless Radio
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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.
Talk at SASTRA
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Wireless Sensor Networks
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ZigBee Wireless Communication
Protocol
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Based on the IEEE 802.15.4 standard
Small form factor
Relatively Inexpensive
Low Power Consumption
Low Data Rate of Communication
Self Organising, Self-Healing…multihop nodes
Integrated Sensors
Ideal for Wireless Sensor Network
Applications
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WSN APPLICATIONS
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Potential for new intelligent applications:
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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
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Source: USC Web Site
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iBadge - UCLA
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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
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MIT d'Arbeloff Lab – The ring sensor
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Oak Ridge National Laboratory
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Monitors the physiological status of the
wearer and transmits the information to
the medical professional over the Internet
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
Model bridge with attached wireless sensors,
B.F. Spencer’s Lab, Civil E., U. Illinois U-C
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Semi-active Hydraulic Damper
(SHD), Kajima Corporation, Japan
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Application in Environment
Monitoring
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Measuring pollutant
concentration
Pollutants monitored by sensors in
the river
Pass on information
to monitoring station
Predict current
location of pollutant
volume based on
various parameters
ST
Sensors report to the base
monitoring station
Take corrective action
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Vehicular Traffic Control
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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
VMesh: Distributed Data Sensing, Relaying,
& Computing via Vehicular Wireless Mesh
Networks
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Network characteristics of WSN
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Generally, the network:
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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
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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
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Individual sensors are quite limited.
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Full potential is realized only by using a
large number of sensors.
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Sensors are then organized into an ad
hoc network.
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Need efficient protocols to route and
manage data in this network.
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Network Topologies
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Star
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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
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Mesh
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Multi-hopping network
All nodes are routers
Self-configuring network
Node fails, network selfheals
Re-routes data through
shortest path
Highly fault tolerant network
Multi-hopping provides
much longer range
Higher power
consumption…nodes must
always listen!
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Network Topologies
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Star-Mesh Hybrid
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Combines of star’s low
power and…
…mesh’s 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
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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
AP1
Wired Network
Infrastructure
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)
Self-organizing
Ad-hoc WLAN
August 24, 2006
Forwarding Node (FN)
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How to get information
from Data-centric Sensor Networks?
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Types of Queries:
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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:
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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
Application (passing parameters via API)
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Technical challenges
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Sensor design
Self-organizing network, that requires 0configuration of sensors
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Random or planned deployment of sensors,
and collators
Auto-addressing
Auto-service discovery
Sensor localization
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Power Consumption
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Limited Power Source
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Battery Lifetime is limited
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Each sensor node plays a dual role of data
originator and data router (data processor)
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The malfunctioning of a few nodes
consumes lot of energy (rerouting of
packets and significant topological changes)
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Environmental Factors
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Wireless sensors need to operate in
conditions that are not encountered by
typical computing devices:
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Rain, sleet, snow, hail, etc.
Wide temperature variations
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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
Model
Honeywell H-300
Mica 2
Date
6/1964
7/2003
CPU
2 MHz
4 MHz
Memory
32 KB
128 KB
SRAM
???
512 KB
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Advances in Wireless Sensor
Nodes
Consider Multiple Generations of Berkeley Motes
Model
Rene 2
Rene 2
Date
10/2000 6/2001
Mica
Mica 2
2/2002
7/2003
CPU
4 MHz
8 MHz
4 MHz
4 MHz
Flash
Memory
8 KB
16 KB
128 KB
128 KB
SRAM
32 KB
32 KB
512 KB
512 KB
Radio
10 Kbps 10 Kbps 40 Kbps 40 Kbps
August 24, 2006
Talk at SASTRA
65
Summary

Sensor networks will facilitate one to address
several societal issues:



Applications in other sectors


Early-warning systems
Disaster mitigation
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
August 24, 2006
Talk at SASTRA
66
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
August 24, 2006
Talk at SASTRA
67
Any
Questions?
August 24, 2006
Talk at SASTRA
68