An Overview of Sensor Network Techniques

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An Overview of Sensor Network Techniques
EECS 600 Advanced Network Research, Spring 2005

• Shudong Jin
• January 12, 2005

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References

• I. F. Akyildiz, W. Su, Y. Sankarasubramaniam, and
  E. Cayirci. Wireless sensor networks a survey.
  Computer Networks (Elsevier), (2002)
• D. Ganesan, A. Cerpa, Y. Yu, W. Ye, J. Zhao, and
  D. Estrin. Networking Issues in Sensor Networks.
  Journal of Parallel and Distributed Computing
  (JPDC), Special Issues on Fronteirs in
  Distributed Sensor Networks, 2004.

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An Overview of Various Aspects

• Sensing tasks and potential applications
• Factors influencing the design of sensor networks
• Communication architecture for sensor networks
• Algorithms and protocols developed for each layer
  in the literature
• Open research issues

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Sensing Tasks

• Different types of sensors seismic, low sampling
  rate magnetic, thermal, visual, infrared,
  acoustic and radar, able to monitor
• temperature,
• humidity,
• vehicular movement,
• lightning condition,
• pressure,
• soil makeup,
• noise levels,
• the presence or absence of certain kinds of
  objects,
• mechanical stress levels on attached objects, and
• the current characteristics such as speed,
  direction, and size of an object.

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Military Applications

• Desirable characteristics of sensor networks
• rapid deployment,
• self-organization
• fault tolerance
• Example applications
• Monitoring friendly forces, equipment and
  ammunition
• Battlefield surveillance
• Reconnaissance of opposing forces and terrain
• Targeting
• Battle damage assessment
• Nuclear, biological and chemical attack detection
  and reconnaissance

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Environmental Applications

• Desirable characteristics of sensor networks
• untethered sensors
• No interruption to the environment
• Redundancy
• Example applications
• Forest fire detection Strategically, randomly,
  and densely deployed sensor nodes can relay the
  exact origin of the fire.
• Biocomplexity mapping of the environment
  integrating information across temporal and
  spatial scales.
• Flood detection rainfall, water level and
  weather sensors supply information to the
  centralized database system.
• Precision Agriculture the pesticides level in
  the drinking water, soil erosion, and air
  pollution.

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Home applications

• Home automation smart sensor nodes and actuators
  can be buried in appliances, such as vacuum
  cleaners, micro-wave ovens, refrigerators, and
  VCRs. They are connected to external networks.
• Smart environment Furniture and appliances (and
  servers) learn to provide the needed service.
• Smart kindergarten to provide parents and
  teachers with the abilities to comprehensively
  investigate students learning processes to
  collect, manage, and fuse the information of the
  sensors
• Many more applications

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An Overview of Various Aspects

• Sensing tasks and potential applications
• Factors influencing the design of sensor networks
• Communication architecture for sensor networks
• Algorithms and protocols developed for each layer
  in the literature
• Open research issues

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Factors Influencing Sensor Network Design

• fault tolerance
• scalability
• production costs
• operating environment
• sensor network topology
• hardware constraints
• transmission media and
• power consumption.

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Fault tolerance

• Failures
• lack of power,
• physical damage in harsh environment
• Interference by other objects (e.g. radios) and
  other sensors.
• Fault tolerance the ability to sustain sensor
  network functionalities without any interruption
  due to failures
• reliability Rk(t) or fault tolerance of a sensor
  node (using the Poisson distribution), i.e., the
  probability of not having a failure within the
  time interval (0,t)
• Rk(t) exp(-?kt)
• ?k the failure rate of sensor node k
• The environment is important to the fault
  tolerance of algorithms and protocols

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Scalability

• of sensors hundreds, thousands, to millions,
  depending on the type of applications.
• Density can be expressed as
• µ(R) (N p R2) / A
• where N is the number of scattered sensor nodes
  in region A and R, the radio transmission range.
  Basically, µ(R) gives the number of nodes within
  the transmission radius of each node in region A.
• Note often we consider 2-dimensional space.
• Density also depends on the applications.

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Costs

• Per node cost is important for large sensor
  networks. It has to be kept low.
• Bluetooth radio system 5 now, but still too
  expensive for sensors. PicoNode targeted to be lt
  50c.
• More challenging, with large amount of
  functionalities

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Hardware constraints

• All components must be contained in a matchbox
• Limited energy
• Low speed (MHz) and small OS kernel (KBs)
• Small memory (KBs)
• Transceiver (kbps, short range, feet-meters)

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Sensor network topology

• topology maintenance a challenging task due to
• of nodes, failures, dynamics etc
• Pre-deployment and deployment phase no careful
  planning. considerations
• the installation cost,
• no need for any pre-organization and
  pre-planning,
• the flexibility of arrangement, and
• better self-organization and fault tolerance.
• Post-deployment phase
• topology changes are due to change in position,
  reachability (due to jamming, noise, moving
  obstacles, etc.), available energy,
  malfunctioning, etc
• How to maintain the topology change?
• Re-deployment of additional nodes phase
• Adding new sensors

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Transmission media

• Wireless communication, formed by radio, infrared
  or optical media

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Power consumption

• Sensor node lifetime shows a strong dependence on
  battery lifetime
• sensing, communication, and data processing.
• Communication
• A sensor node expends maximum energy in data
  communication. This involves both data
  transmission and reception.
• the active power the start-up power consumption
• Data processing
• Much less, local data processing is crucial in
  minimizing power consumption in a multi-hop
  sensor network.

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An Overview of Various Aspects

• Sensing tasks and potential applications
• Factors influencing the design of sensor networks
• Communication architecture for sensor networks
• Algorithms and protocols developed for each layer
  in the literature
• Open research issues

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Typical sensor networks
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Protocol stack
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An Overview of Various Aspects

• Sensing tasks and potential applications
• Factors influencing the design of sensor networks
• Communication architecture for sensor networks
• Algorithms and protocols developed for each layer
  in the literature
• Open research issues

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Application layer current and future

• To the best of our knowledge, although many
  application areas for sensor networks are defined
  and proposed, potential application layer
  protocols for sensor networks remains a largely
  unexplored region
• Q pure application layer protocols may not be
  necessary, nor efficient. What do you think?
• Possible application layer protocols (necessary?)
• sensor management protocol (SMP),
• task assignment and data advertisement protocol
  (TADAP), and
• sensor query and data dissemination protocol
  (SQDDP),
• All of them are open research issues, and we need
  other application layer protocols to provide a
  greater level of services.

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Example Sensor management protocol

• introducing the rules on clustering sensors, e.g.
• exchanging data related to the location finding
  algorithms
• time synchronization of the sensor nodes
• moving sensor nodes
• turning sensor nodes on and off (to conserve
  energy)
• querying the sensor network configuration and the
  status of nodes, and re-configuring the sensor
  network
• authentication, key distribution and security

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Transport layer current and future

• The need for transport layer? Maybe not.
• How to address?
• Do we need reliable service at transport layer
• Congestion control
• No attempt thus far to propose a scheme or to
  discuss the issues related to the transport layer
• Open research issues
• Challenging problem due to the influencing
  factors, especially the hardware constraints such
  as the limited power and memory.
• no buffer like TCP
• acknowledgements too expensive.
• new schemes that split the end-to-end
  communication probably at the sinks may be needed
  where UDP type protocols are used in the sensor
  network and traditional TCP/UDP protocols in the
  Internet or Satellite network.

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Network layer current and future

• All about routing at this layer (unstructured
  network)
• Those ad hoc routing techniques, Like DSR? Do not
  usually fit the requirements
• Power efficiency
• Sensor networks are mostly data centric.
• Data aggregation is useful
• Both attribute-based addressing and location
  awareness.
• How to route, i.e., choice of routing metrics
• Maximum available power (PA) route
• Minimum energy (ME) route
• Minimum hop (MH) route
• Maximum minimum PA node route

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Network layer current and future

• Flooding each node receiving a packet repeats it
  by broadcasting (simple flooding versus
  TTL-based)
• Gossiping no broadcast, but send the incoming
  packets to a randomly selected neighbor.
• Sensor protocols for information via negotiation
  (SPIN)
• Low-energy adaptive clustering hierarchy (LEACH)
  clustering-based protocol
• need to be improved or new protocols need to be
  developed to address higher topology changes and
  higher scalability. Also, new internetworking
  schemes should be developed to allow easy
  communication between the sensor networks and
  external networks

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Data link layer current and future

• multiplexing of data streams, data frame
  detection, medium access and error control,
  reliable point-to-point and point-to-multipoint
  connections
• Medium access control (MAC) establish links,
  fairly and efficiently share communication
  resources, must have
• built-in power conservation,
• mobility management, and
• failure recovery strategies.
• Fixed allocation (like TDMA) and random access
  (like CSMA)

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Data link layer current and future

• Open research issues
• MAC for mobile sensor networks
• Energy requirement for sensor network
  self-organization.
• Error control coding schemes, FEC, erasure code
  etc
• Power saving modes of operation

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The active sub-areas

• Routing
• Topology control
• Data management, aggregation and query
• MAC protocols
• Target tracking, resource discovery
• Monitoring and maintenance