Research On Sensor Nets

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Research On Sensor Nets

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Outline

• An Introduction
• Surveillance and Coverage
• Mobile Sensors
• Reality and Terrain
• Scalability and Heterogeneous Sensor Nets
• Multiple Sensor Nets and InterSensorNets
• Semantic Sensor Nets
• Detection and Anti-detection
• Future works

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Outline

• An Introduction
• Surveillance and Coverage
• Mobile Sensors
• Reality and Terrain
• Scalability and Heterogeneous Sensor Nets
• Multiple Sensor Nets and InterSensorNets
• Semantic Sensor Nets
• Detection and Anti-detection
• Future works

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Trend of Computers

• Mainframes
• PCs
• Laptops
• PDAs
• What is next?

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Ubiquitous Computing

• Mark Weiser
• The most profound technologies are those that
  disappear.
• They weave themselves into the fabric of
  everyday life until they are indistinguishable
  from it.

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Sensory Computing

• Sensor network (sensor net) that monitors the
  earth
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• Establishing a connection between virtual world
  and physical world

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What is a Sensor Net

• A collection of many wireless sensors
• Sensory
• Wireless communication
• Ad hoc

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Sensor Nets

Sensory data
Sensory data
Sensory data
Sensory data
Sensory data
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Enabling Technology

• Sensors
• Wireless
• Micro-fabrication and integration
• Embedded systems

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What a Sensor Net Can Do

• Monitoring
• People
• Vehicles
• Animals
• Environment
• Fabs
• Supply chains

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Advantages of Sensornet

• Energy advantage
• Short-range communication

• Trade-off of hops

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Advantages of Sensor Net

• Detection advantage
• More sensors, shorter distance to the target
• Better signal-to-noise ratio (SNR)

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Advantages of Sensor Net

• Structure advantage
• Robustness due to redundancy
• In-network processing

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Disadvantage

• Small sensors
• Limited on
• Power
• Communication range bandwidth
• Computation power
• Memory

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Power

• Short-range communication
• On-demand sensory
• Short duty cycle
• More computing,
• less communication
• Field charging

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Communication, Computation and Memory

• Scalability
• In-network processing or aggregation
• Efficient algorithms
• Less computing cycles
• Less storage requirement

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Satellite and Sensor Net

• Satellite
• Global view
• Sensor net
• Detailed view

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Applications

• Military battlefield awareness
• Rapid deployment
• Monitoring battlefield or bases

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Military Affairs
Sensor systems
Deployment
Information gathering
Enemy detection
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Applications

• Disaster situations
• Fire
• Chemical leakage
• Nuclear plant

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Disaster and Security
National key project- Sanxia embankment inspection
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Applications

• Environmental monitoring
• Pollution
• Water level

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Environmental Monitoring
Mine explosion accident scene
Sensor communication detecting in miner
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Applications

• Agriculture
• Monitor
• Temperature
• humidity
• plant disease
• insect pests

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Agriculture
Water resource management
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Applications

• Asset and warehouse management
• Tracking assets
• With RFID

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Applications

• Industrial process control
• Monitoring manufacturing processes
• Monitoring equipments, such as motors, pipes
• Monitoring servers
• Monitoring any irregular situations and failures

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Applications

• Building monitoring and control
• Low wiring cost
• Cut down energy cost
• Air control
• Biological agents or chemical pollutants

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Applications

• Security and surveillance
• Airports
• Subways
• Nuclear power plants

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Applications

• Health care
• Monitoring vital signs of patients
• In-home elder care monitoring subtler behaviors
  of an elders

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Applications

• Automotive
• Vehicle-centric sensor net
• Robot with sensors
• Non-traditional
• Mobile
• Possible long distance

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Examples

• Great Duck Island
• 190 sensors monitor the nesting petrels
• Avoid to disturb the bird

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Examples

• BP, an oil and gas giant
• Losing track of 900 railcars in 2003
• Solution to fit each railcar with a network of
  sensors --- that not only track where the
  railcars is at all times, but can monitor weight,
  internal temperature, etc.

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Examples

• BP
• Monitoring customers liquefied petroleum gas
  fuel tanks
• 25 improvement in efficiency
• The tanks have gauges but customer would forget
  to look at them until it was too late

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Examples

• BP
• Tracking lone workers
• To avoid hazardous areas where they may be at risk

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Examples

• Intel
• Now, all equipments are manually inspected once a
  quarter, found 80 of problems
• With sensor net, 95 of the problems can be found

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Examples

• In Pickberry vineyard, a sensor net monitors
• soil moisture
• rainfall
• wind velocity and direction

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Trend of Sensor Net Research

• Application-driven
• Most basics are researched
• New topics from real-world applications

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Outline

• An Introduction
• Surveillance and Coverage
• Mobile Sensors
• Reality and Terrain
• Scalability and Heterogeneous Sensor Nets
• Multiple Sensor Nets and InterSensorNets
• Semantic Sensor Nets
• Detection and Anti-detection
• Future works

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Surveillance

• Points of interest or
• areas of interest
• Deployment
• Structured or unstructured

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Coverage and Connection

• Communication-to-Coverage Ratio (CCR)
• Equivalence 2 or 1.732?

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Coverage and Connection
Sensing range
Communication
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Coverage and Connection
CCR high low
Dense Good coverage Good commu- nication
Sparse Isolated
Connected
Disjoint
Connected
Disjoint
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Coverage

• 0-1 coverage
• Coverage percentage
• Average walking distance
• Probability coverage
• Detection probability

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Coverage

• 0-1 coverage

Average walking distance
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Coverage

• Probability coverage

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Exposure

• Path-based metrics
• a start point and a destination
• Best path and worst path
• A probability approach with Voronoi diagram

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Voronoi Diagram
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Sparse Sensor Nets

• Point surveillance
• Low CCR
• How to communication
• Communicators?
• Long range communication?
• Mobile collectors?

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Holes and Islands

• Definition of holes and islands
• The effect of a hole in communication and
  coverage
• Communication island
• Use mobile sensors
• fill holes
• connect islands

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Dense Sensor Nets

• Active and sleep
• Maximum coverage
• Minimum and balanced energy dissipation

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The ACOS Algorithm

• A precise energy-aware coverage control protocol

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Outline

• An Introduction
• Surveillance and Coverage
• Mobile Sensors
• Reality and Terrain
• Scalability and Heterogeneous Sensor Nets
• Multiple Sensor Nets and InterSensorNets
• Semantic Sensor Nets
• Detection and Anti-detection
• Future works

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Mobile Sensors

• Attached or active
• Attached mobile sensors
• like mobile ad hoc networks
• vehicles
• robots
• Active mobile sensors
• move or fly?

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Active Mobile Sensors

• Between sensors and actuators
• For tasks related to sensor nets
• fill holes or connect islands
• collect sensory data
• charge sensor nodes

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Mobile Sensors

• Collect sensory data
• for sparse sensor nets
• can charge sensor nodes at the same time
• Charge sensor nodes
• distance charging
• infrequently

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Mobile Sensors
For coverage --- connect islands first then
fill holes
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Mobile Sensors

• Algorithms based on global info
• Centralized algorithm
• Algorithms based on local info
• Distributed algorithm

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Outline

• An Introduction
• Surveillance and Coverage
• Mobile Sensors
• Reality and Terrain
• Scalability and Heterogeneous Sensor Nets
• Multiple Sensor Nets and InterSensorNets
• Semantic Sensor Nets
• Detection and Anti-detection
• Future works

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Reality

• Most current solutions of sensor nets work well
  in simulation only
• We dont know how the solutions work in the real
  world
• they can work poorly in practice
• Models of communication realities to improve
  simulation tools
• New network protocols that work in real world
  environments
• Creates deployable systems

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Terrain

• One type of the reality is terrain
• Terrain effect on communication
• Terrain effect on sensor mobility

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Digital Map for Mobile Sensors

• Preprocessing
• Find a path to destination

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Digital Maps
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Path to Destination
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Outline

• An Introduction
• Surveillance and Coverage
• Mobile Sensors
• Reality and Terrain
• Scalability and Heterogeneous Sensor Nets
• Multiple Sensor Nets and InterSensorNets
• Semantic Sensor Nets
• Detection and Anti-detection
• Future works

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Scalability of Sensor Nets

• Sensor nets are ad hoc networks
• Scalability problem
• better than general ad hoc networks
• amount of nonredundant Information is
• capacity of ad hoc networks is
• but, it requires eliminating all redundant
  information

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Scalability of Sensor Nets

• In the case of an event, amount of information
  can significantly increase
• Many hops make information transmission
• large delay
• unreliable
• Reduction of number of hops makes a sensor net
  scalable
• Solutions
• heterogeneous sensor nets
• multiple communication channels
• directional antennas

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Heterogeneous Sensor Nets

• Sensor nodes of different power and communication
  ranges
• Super nodes reduce the number of hops, forwarding
  data more efficiently
• Need flexible communication scheme

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Communication

• Increasing power
• Multi-channel communication
• bandwidth increase up to 34 times
• Multiple interfaces
• Directional antennas

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Outline

• An Introduction
• Surveillance and Coverage
• Mobile Sensors
• Reality and Terrain
• Scalability and Heterogeneous Sensor Nets
• Multiple Sensor Nets and InterSensorNets
• Semantic Sensor Nets
• Detection and Anti-detection
• Future works

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Multiple Sensor Nets

• Phenomenon 1 --- battlefield
• Air Force, Army and Marine deploy their own
  sensor networks
• Each of them may also deploy different networks
  for various sensing purposes
• moving targets
• radiation
• light
• pressure

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Multiple Sensor Nets
Dynamically deployment
System scalable
Information sharing
Robustness
Army sensornet
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Multiple Sensor Nets

• Phenomenon 2 --- agriculture
• Different sensor nets could be deployed
• humidity
• temperature
• plant disease
• insect pests

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Heterogeneous Net for Agriculture
Temperature and humidity
Diseases and insect
cooperation
Basicity
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Multiple Sensor Nets

• Many sensor networks, each of different sensor
  types, may interfere each other, decreasing the
  signal-to-noise ratio (SNR)
• It is possible to change the drawback to an
  advantage
• cooperation of multiple sensor nets
• Inter-operability between sensor networks enables
  an InterSensorNet

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InterSensorNet

• An InterSensorNet is composed of multiple sensor
  networks
• Overlap or partially-overlap
• relay data for each other
• process data for each other
• possible interference reduced
• energy dissipation reduced
• connectivity and robustness improved

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InterSensorNet

• Topology control
• Localization and location service
• Synchronization
• In-network processing

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Terminology

• Local node --- node in a local sensor net
• Foreign node --- node in a foreign sensor net

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Topology Control

• Topology control can be more efficient with
  cooperation of sensor nets
• Better topology can be formed with foreign nodes
• Energy saving with help from foreign nodes

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Topology Control

• When a sensor node cannot find a neighbor in its
  local network, it may find a neighbor in another
  network
• Two nodes may be far apart and a higher
  communication power is required
• foreign nodes can help to reduce the power
  dissipation

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Localization and Location Service

• With the help of foreign nodes, a node is able to
  determine its location more accurately
• It can obtain a location service from foreign
  sensor nets

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Synchronization

• With the help of foreign nodes, time
  synchronization can be more accurate
• Sometime, a node cannot receive synchronization
  signal without help from foreign nodes

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In-network Processing

• Some foreign nodes may be in a better location to
  process data
• Some foreign nodes may have necessary information
  for data processing
• Some foreign nodes may have higher capacity to
  process data

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Interoperability and Standard

• internetworking protocols to enable the
  cooperation among multiple sensor nets
• Standard of internetworking protocols

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Incentives

• Why should a node deplete its battery doing
  something for others?
• Mechanism for incentives enables cooperation
• When a mechanism is available, nodes that serve
  as good citizens'' could be rewarded

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Outline

• An Introduction
• Surveillance and Coverage
• Mobile Sensors
• Reality and Terrain
• Scalability and Heterogeneous Sensor Nets
• Multiple Sensor Nets and InterSensorNets
• Semantic Sensor Nets
• Detection and Anti-detection
• Future works

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Interoperability

• Current trend
• interconnection of multiple sensor nets
• multiple usage
• No general scalable model for
• large-scale
• heterogeneous
• multiple sensor nets
• Only a few standards for interoperability of
  sensor nets
• 802.15.4 and ZigBee

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Semantics

• Semantics enables interoperability of multiple
  sensor nets
• Semantics is a glue of multiple sensor nets

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Semantic Tags

• The current sensor nets have some semantic tags
• location, time, type, etc.
• The problems
• fragmented semantic tags
• implicit semantics
• No standard for semantic tags to support
  semantics of sensor nets

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Semantic Sensor Nets

• A Semantic Sensor Net (SSN) is a heterogeneous
  sensor network that enables dynamic tagging of
  semantic information to sensory data and creates
  semantics in the process of aggregation and
  abstraction of sensory data to allow more
  efficient and systematic monitoring and handling
  of the environmental dynamics to provide demanded
  services.

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Types of Semantics

• Semantics in a sensor net
• Query Semantics
• Sensory Data Semantics
• Aggregated Data Semantics

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Semantic Tags for Sensory Data

• Meta data
• necessary description about the sensory data
  itself
• example temperature type, accuracy
• Context information
• the context information in which the sensory data
  was generated
• example location, ID, timestamp

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Sensory Data Model

• Provide a highly scalable method to describe
  different sensory data and its semantics. With a
  uniform framework, sensory data can achieve
  self-description.

Self-description
Semantic tag
Sensory data
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Semantics Example
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Flow of Semantics
Result
Query
Semantic layer
Synthesis data semantic layer

Sensory data semantic layer

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Semantic Sensor Nets
gateway
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Query, Parsing and Execution
SSNQL
Query
Parsing
SSNEL
Executable Program
SSN
SSNDL
SSN
Description
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Outline

• An Introduction
• Surveillance and Coverage
• Mobile Sensors
• Reality and Terrain
• Scalability and Heterogeneous Sensor Nets
• Multiple Sensor Nets and InterSensorNets
• Semantic Sensor Nets
• Detection and Anti-detection
• Future works

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Taxonomy

• Intelligent or Non-Intelligent Targets (I-target
  or NI-target)
• Moving or stationary targets
• Target-first or sensornet-first

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Detection

• Points or areas
• Structured or unstructured
• Measures of detection
• Coverage or exposure
• Coverage percentage
• Average walking distance
• Detection probability

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Detection

• Sensor net detects target
• Target detects sensor net
• Sensor net avoids targets detection
• Sensor net detects targets detection

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Anti-detection

• Sensornet-first
• look around then sneak in
• find a route with smallest probability to be
  detected
• find the Voronoi diagram at real-time
• Target-first
• keep silence
• escape
• Interfere or destroy surrounding sensor nets

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Hiding Sensor Nets

• How to reduce the probability to be detected by
  the target?
• Minimal radiation --- especially in the
  initialization phase
• Faster initialization
• Lazy report of detection results

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Other Detection Issues

• Determine I-target or NI-target
• I-target finding a good route
• NI-target brownian motion or straight line
• Intrusion detection
• When a cluster of sensors fails or interfered, it
  is possible an I-target

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Outline

• An Introduction
• Surveillance and Coverage
• Mobile Sensors
• Reality and Terrain
• Scalability and Heterogeneous Sensor Nets
• Multiple Sensor Nets and InterSensorNets
• Semantic Sensor Nets
• Detection and Anti-detection
• Future works

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Future Works

• Structured sensor networks and deployment
• Actuators
• Dual usage of sensor nets and low-energy
  communication
• Extracting info from noisy environment
• Data mining
• Applications