7112009 1 An Introduction to Sensor Networks Content Reference by rebeccaGerritY



An Introduction to Sensor                                    Content
Networks                                                      Definition
                                                              Applications
                                                              Challenges
    Wireless Intelligent Networks Center, Nile University
                     Alexandria University

Reference                                                    Sensor Networks Definition
   Wireless sensor networks: a survey                        A sensor network is composed of a large
    I.F. Akyildiz, W. Su,Y. Sankarasubramaniam,                number of sensor nodes, which are
    E. Cayirci, Computer Networks 2002.                        densely deployed either inside the
                                                               phenomenon or very close to it
                                                              Random deployment
                                                              Self-organizing capabilities
                                                              Cooperative capabilities

Sensor Networks Applications                                 Communication Architecture
   Sensors can sense                                         The sensor nodes are usually scattered in
     ◦   Temperature
     ◦   Humidity                                              a sensor field
     ◦   Vehicular movement                                   Each of these scattered sensor nodes has
     ◦   Lightning condition
     ◦   Pressure
                                                               the capabilities to collect data and route
     ◦   Soil makeup                                           data back to the sink
     ◦   Noise levels                                         Data are routed back to the sink by a
     ◦   Presence or absence of certain kinds of objects
     ◦   Mechanical stress levels on attached objects          multi-hop infrastructureless architecture
     ◦   Current characteristics such as speed, direction,    The sink may communicate with the task
         and size of an object
                                                               manager node via Internet or satellite


Example of Sensor Networks                           Data Delivery Models
                                                      Continuous: sensors communicate their
                                                       data continuously at a prespecified rate
                                                      Event driven: sensors report information
                                                       only when the event of interest occurs
                                                      Observer initiated (request-reply):
                                                       sensors only reports their results in
                                                       response to an explicit request from the
                                                      Hybrid: all three approaches coexist

Sensor Networks Applications                         Sensor Networks Applications
   Military                                            Environmental applications
    ◦ Monitoring friendly forces, equipment and          ◦   Forest fire detection
      ammunition                                         ◦   Biocomplexity mapping of the environment
    ◦ Reconnaissance of opposing forces and              ◦   Flood detection
      terrain                                            ◦   Precision agriculture
    ◦ Battlefield surveillance
    ◦ Battle damage assessment
    ◦ Nuclear, biological and chemical attack

Sensor Networks Applications                         Sensor Networks Applications
   Health applications                                 Home and other commercial applications
    ◦ Tele-monitoring of human physiological data        ◦   Home automation and Smart environment
    ◦ Tracking and monitoring patients and doctors       ◦   Interactive museums
      inside a hospital                                  ◦   Managing inventory control
    ◦ Drug administration in hospitals                   ◦   Vehicle tracking and detection
                                                         ◦   Detecting and monitoring car thefts


        Sensor Devices and Applications                                                      Berkeley Motes
          Berkeley Motes                                                                       Small (under 1” square) microcontroller
          iBadge - UCLA                                                                        It consists of:
          MIT d'Arbeloff Lab – The ring sensor                                                    ◦ Microprocessor
          Nose-on-a-chip                                                                          ◦ A set of sensors for temperature, light,
                                                                                                     acceleration and motion
          Zilog’s eZ80
                                                                                                   ◦ A low power radio for communicating with
          iButton                                                                                   other motes
                                                                                                  C compiler inclusion

        Berkeley Motes                                                               MIT d'Arbeloff Lab – The Ring Sensor
                                                                                      An ambulatory, telemetric,
                                                                                       continuous health monitoring
                                                                                       device developed by d'Arbeloff
                                                                                       Laboratory for Information
                                                                                       Systems and Technology at MIT
                                                                                      Monitor the physiological status
                                                                                       of the wearer and transmit the
                                                                                       information to the medical
                                                                                       professional over the Internet

                                                                                     Clinical trials have been done in conjunction with Massachusetts General Hospital's
                                                                                         Emergency Room, and researchers are now working on commercialization of
                                                                                         the ring-sized device.

 Nose-on-a-chip is a
  MEMS-based sensor,
  developed at Oak Ridge
  National Laboratory                                                                       A 16mm computer chip armored in a stainless
 Can detect 400 species of                                                                  steel can
  gases and transmit a signal                                                               Up-to-date information can travel with a person or
  indicating the level to a                                                                  object
  central control station
                                                                                            Types of i-Button
                                                                                               ◦ Memory Button
Consists of an array of tiny sensors on one integrated circuit and electronics on
   another.                                                                                    ◦ Java Powered Cryptographic iButton
The chip can be customized to detect virtually any chemical or biological species.
                                                                                               ◦ Thermochron iButton



iButton Applications
                                                               iBadge - UCLA
                                                                  Investigate behavior of children/patient
   Caregivers Assistance
    ◦ Do not need to keep a bunch of keys. Only one
                                                                  Features:
      iButton will do the work                                     ◦   Speech recording / replaying
   Elder Assistance                                               ◦   Position detection
    ◦ They do not need to enter all their personal                 ◦   Direction detection / estimation(compass)
      information again and again. Only one touch of
      iButton is sufficient                                        ◦   Weather data: Temperature, Humidity, Pressure,
    ◦ They can enter their ATM card information and PIN                Light
      with iButton
    ◦ Vending Machine Operation Assistance
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    iBadge - UCLA                                                  Content
                                                                    Definition
                                                                    Applications
                                                                    Challenges


                                                                   Factors Influencing Sensor Network
    Differences from Adhoc Networks
     Number of nodes                                               Fault Tolerance
     Densely deployed
     Prone to failures
                                                                    Scalability
     Topology changes frequently                                   Hardware Constrains
     Mainly use broadcast communication                            Sensor Network Topology
     Limited in power, computational capacities,                   Environment
      and memory
     May not have global identification (ID)                       Transmission Media
      because of the large amount of overhead                       Power Consumption
      and large number of sensors
     Task oriented



     Factors Influencing Sensor Network
                                                                   Depending on the application, the number
                                                                    may reach an extreme value of millions.
Fault tolerance                                                     New schemes must be able to work with
      Fault tolerance is the ability to sustain sensor
                                                                    this number of nodes.
       network functionalities without any interruption            Basically, the density gives the number of

       due to sensor node failures                                  nodes within the transmission radius of
                                                                    each node in a region.
      The fault tolerance level depends on the application
                                                                   Must also utilize the high density of the
       of the sensor networks
                                                                    sensor networks.

Factors Influencing Sensor                                        Factors Influencing Sensor Network
Network Design                                                    Design

Scalability                                                   Production costs
                                                                 The cost of a single node is very important to
   Density = (R) =(NR2)/A                                      justify the overall cost of the networks
    R – Radio Transmission Range
                                                                 The cost of a sensor node is a very challenging
                                                                  issue given the amount of functionalities with a
                                                                  price of much less than a dollar


     Factors Influencing Sensor Network
                                                                  Sensor Network Topology
                                                                   Pre-deployment and deployment phase,
                                                                    either thrown in as a mass or placed one
    Hardware constraints                                            by one
                                                                   Post-deployment phase, topology changes
                                                                    are due to change in sensor nodes’
                                                                    position, reachability, available energy,
                                                                    malfunctioning, and task details
                                                                   Re-deployment of additional nodes phase,
                                                                    additional sensor nodes can be
                                                                    redeployed at any time to replace
                                                                    malfunctioning nodes or due to changes
                                                                    in task dynamics



    Factors Influencing Sensor Network                                    Factors Influencing Sensor Network
    Design                                                                Design

Environment                                                               Transmission media
    Busy intersections
                                                                            In a multihop sensor network, communicating
    Interior of a large machinery
                                                                             nodes are linked by a wireless medium. To enable
    Bottom of an ocean
    Surface of an ocean during a tornado
                                                                             global operation, the chosen transmission
    Biologically or chemically contaminated field
                                                                             medium must be available worldwide.
    Battlefield beyond the enemy lines                                    Radio
    Home or a large building                                              infrared
    Large warehouse
    Animals
    Fast moving vehicles
    Drain or river moving with current
                                                                     31                                                                        32

    Factors Influencing Sensor Network
                                                                            Definition
Power Consumption                                                           Applications
                                                                            Challenges
   Sensing
   Communication
   Data processing
   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)


    Communication Architecture of
                                                                          Five Layers
    Sensor Networks
                                                                              The physical layer addresses the needs of simple but robust
                                                                               modulation, transmission, and receiving techniques
                                    Combine power and                        The MAC protocol must be power-aware and able to
                                     routing awareness                         minimize collision with neighbors’ broadcasts
                                    Integrates date with                     The network layer takes care of routing the data supplied by
                                     networking protocols                      the transport layer
                                    Communicates power                       The transport layer helps to maintain the flow of data if the
                                     efficiently through the                   sensor networks application requires it
                                     wireless medium                          Different types of application software can be built and used
                                    Promotes cooperative                      on the application layer
                                     efforts among sensor nodes



                                                                   Communication Architecture of
        Three Plans
                                                                   Sensor Networks
         The power management plane manages how
          a sensor node uses its power
         The mobility management plane detects and               Physical layer:
          registers the movement of sensor nodes, so                Address the needs of simple but robust
          a route back to the user is always maintained,            modulation, transmission, and receiving
          and the sensor nodes can keep track of who                techniques.
          their neighbor sensor nodes are                          Frequency selection
         The task management plane balances and
                                                                   Carrier frequency generation
          schedules the sensing tasks given to a
                                                                   Signal detection and propagation
          specific region
                                                                   Signal modulation and data encryption


        Communication Architecture of                              Communication Architecture of
        Sensor Networks                                            Sensor Networks
                                                                    Open research issues
     Propagation Effects                                            Modulation schemes
       Minimum output power
                                                                     Strategies to overcome signal propagation
          (dn 2=<n<4)
       Ground reflect – Multihop in dense
       sensor net work                                               Hardware design: transceiver
     Power Efficiency Modulation Scheme
      M-ary Modulation scheme
      Ultra wideband(impulse radio)

                                                         39                                                    40

        Communication Architecture of                              Communication Architecture of
        Sensor Networks                                            Sensor Networks

Data link layer:                                              Medium access control
    The data link layer is responsible for the multiplexing    Creation of the network infrastructure
    of data stream, data frame detection, the medium           Fairly and efficiently share communication
    access and error control                                    resources between sensor nodes
                                                               Existing MAC protocols (Cellular System,
   Medium Access Control
                                                                Bluetooth and mobile ad hoc network)
   Power Saving Modes of Operation
   Error Control

                                                         41                                                    42


             Communication Architecture of                                          Communication Architecture of
             Sensor Networks                                                        Sensor Networks
MAC for Sensor Networks
                                                                               Power Saving Modes of Operation
   Self-organizing medium access control for sensor networks and
                                                                                  Sensor nodes communicate using short data
    Eaves-drop-and-register Algorithm
   CSMA-Based Medium Access
   Hybrid TDMA/FDMA-Based                                                        The shorter the packets, the more dominance of
                                                                                   startup energy
                                                                                  Operation in a power saving mode is energy
                                                                                   efficient only if the time spent in that mode is
                                                                                   greater than a certain threshold

                                                                       43                                                                              44

             Communication Architecture of                                          Communication Architecture of
             Sensor Networks                                                        Sensor Networks
                                                                                     Open research issues
                                                                                      MAC for mobile sensor networks
     Error Control
                                                                                      Determination of lower bounds on the
        Error control modes in Communication Networks (additional
         retransmission energy cost)
                                                                                       energy required for sensor network self-
          Forward Error Correction (FEC)                                               organization
          Automatic repeat request (ARQ)                                              Error control coding schemes
        Simple error control codes with low-complexity encoding and
         decoding might present the best solutions for sensor networks                Power saving modes of operation

                                                                       45                                                                              46

             Communication Architecture of                                          Communication Architecture of
             Sensor Networks                                                        Sensor Networks

         Network layer:                                                     Energy Efficient Routes
            Power efficiency is always an important consideration
            Sensor networks are mostly data centric
            Data aggregation is useful only when it does not hinder
             the collaborative effort of the sensor nodes                                                 •Maximum available power (PA) route: Route
            An ideal sensor network has attribute-based addressing                                       •Minimum energy (ME) route: Route 1
             and location awareness                                                                       •Minimum hop (MH) route: Route 3
                                                                                                          •Maximum minimum PA node route: Route 3
                                                                                                          •Minimum longest edge route: Route 1

                                                                       47                                                                              48


         Communication Architecture of                                      Communication Architecture of
         Sensor Networks                                                    Sensor Networks

    Interest Dissemination                                            Data aggregation

       Sinks broadcast the interest                                                              Solve implosion and overlap
       Sensor nodes broadcast the advertisements                                                  Problem
                                                                                                  Aggregation based on same
       Attribute-based naming
                                                                                                   attribute of phenomenon
        “The areas where the temperature is over70oF   ”
                                                                                                  Specifics (the locations of
        “The temperature read by a certain node ”
                                                                                                   reporting sensor nodes) should
                                                                                                   not be left out

                                                                 49                                                                  50

         Communication Architecture of                                      Communication Architecture of
         Sensor Networks                                                    Sensor Networks

Several Network Layer Schemes for Sensor Networks                       Open research issues
                                                                           New protocols need to be developed to address higher
                                                                            topology changes and higher scalability
                                                                           New internetworking schemes should be developed to
                                                                            allow easy communication between the sensor networks
                                                                            and external networks

                                                                 51                                                                  52

         Communication Architecture of                                      Communication Architecture of
         Sensor Networks                                                    Sensor Networks

    Transport layer:                                                    Open research issues
       This layer is especially needed when the system is
        planned to be accessed through Internet or other                   Because acknowledgments are too costly, new
        external networks.                                                  schemes that split the end-to-end
       TCP/UDP type protocols meet most requirements                       communication probably at the sinks may be
        (not based on global addressing)
       Little attempt thus far to propose a scheme or to
        discuss the issues related to the transport layer of a
        sensor network in literature

                                                                 53                                                                  54


  Communication Architecture of                              Communication Architecture of
  Sensor Networks                                            Sensor Networks

Application layer:                                       Sensor management protocol (SMP)
  Management protocol makes the hardware and                Introducing the rules related to data aggregation, attribute-based
  software of the lower layers transparent to the            naming, and clustering to the sensor nodes
  sensor network management applications.                   Exchanging data related to the location
                                                            finding algorithms
 Sensor management protocol (SMP)                          Time synchronization of the sensor nodes
 Task assignment and data advertisement protocol           Moving sensor nodes
  (TADAP)                                                   Turning sensor nodes on and off
                                                            Querying the sensor network configuration and the status of
 Sensor query and data dissemination protocol               nodes, and reconfiguring the sensor network
  (SQDDP)                                                   Authentication, key distribution, and security in data

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