Wireless Sensor networks survey and research challenges

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Wireless Sensor networkssurvey and research
challenges
University of Tehran Dept. Electrical and
Computer Engineering

• Presented by
• Hosein Sabaghian-Bidgoli
• hsabaghianb_at_gmail.com
• January 11, 2009

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Outlines

• Main references
• Introduction
• Definition
• Communication Architecture
• Protocol stack
• WSN Characteristics
• WSN Design factors
• WSANs
• WSN Structures
• WSN Constraints
• WSN Applications
• WSN types
• .

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Outlines (cont.)

• Task classification
• Internal sensor system
• Standard
• Storage
• Testbed
• Diagnostic and debugging support
• Network services
• Localization
• Synchronization
• Coverage
• Compression and aggregation
• Security
• Communication protocol
• Transport
• Network
• Data link
• Physical
• Cross-layer
• Conclusion

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Main references

• Ian F. Akyildiz, Weilian Su, Yogesh
  Sankarasubramaniam, and Erdal Cayirci, A Survey
  on Sensor Networks, IEEE Communications Magazine,
  August 2002
• Ian F. Akyildiz, Ismail H. Kasimoglu, Wireless
  sensor and actor networks research challenges,
  Elsevier Ad Hoc Networks 2 (2004) 351367
• Jennifer Yick, Biswanath Mukherjee, Dipak Ghosal,
  Wireless sensor network survey, Elsevier Computer
  Networks 52 (2008) 22922330

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IntroductionWSN Definition

• A sensor network is composed of a large number of
  sensor nodes that are densely deployed inside or
  very close to the phenomenon
• random deployment
• self-organizing capabilities

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IntroductionWSN communication Architecture
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IntroductionComponents of Sensor Node
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IntroductionProtocol Stack

• Protocols should be
• Power aware
• Location aware
• Application aware

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IntroductionWSN Characteristics

• Major differences between sensor and ad-hoc
  network
• Number of nodes is higher
• Densely deployment
• Sensor nodes are prone to failure.
• Frequent topology changes
• Broadcast communication paradigm
• Limited processing and power capabilities.
• Possible absence of unique global ID

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IntroductionWSN Design Factors

• Fault Tolerance
• Scalability
• Production Costs
• Hardware Constraints
• Sensor Network Topology
• Environment
• Transmission Media
• Power Consumption

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WSN Design Factors Fault Tolerance

• Each Nodes are prone to unexpected failure (more
  than other network)
• Fault tolerance is the ability to sustain sensor
  network functionalities without any interruption
  due to sensor node failures.

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WSN Design Factors Scalability

• Size Number of node (100 1000)
• Density µ(R)(N?R2)/A
• Protocol should
• be able to scale to such high degree
• take advantage of the high density of such
  networks

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WSN Design Factors Production Costs

• The cost of a single node must be low given the
  amount of functionalities
• Much less than 1

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WSN Design Factors Hardware Constraints

• All these units combined together must
• Extremely low power
• Extremely small volume

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WSN Design Factors Topology

• Must be maintained specially in very high
  densities
• Pre-deployment and deployment phase
• Post-deployment phase
• Re-deployment of additional nodes phase

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WSN Design Factors Environment

• May be inaccessible
• either because of hostile environment
• or because they are embedded in a structure
• Impact of environment condition
• Temperature
• Humidity
• Movement
• Underwater
• Underground

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WSN Design Factors Environment

• Busy intersections
• Interior of a large machinery
• Bottom of an ocean
• Surface of an ocean during a tornado
• Biologically or chemically contaminated field
• Battlefield beyond the enemy lines
• Home or a large building
• Large warehouse
• Animals
• Fast moving vehicles
• Drain or river moving with current

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WSN Design Factors Transmission Media

• RF
• Infrared
• Optical
• Acoustic 3

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WSN Design Factors Power Consumption

• Power conservation
• Sensing
• Communication
• Data processing

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Some Research Projects
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wireless sensor and actornetworks (WSANs)

• WSAN Capabilities
• Observing the physical world
• Processing the data
• Making decisions
• Performing appropriate actions
• WSAN applications
• battlefield surveillance
• microclimate control in buildings
• nuclear, biological and chemical attack detection
  
• Home automation
• environmental monitoring

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WSANs unique characteristics

• Real-time requirement
• Coordination
• Sensor-Actor Coordination
• Actor-Actor Coordination

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WSN structure

• A WSN typically has little or no infrastructure
• There are two types of WSNs
• Structured model
• Unstructured model

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Unstructured model

• Densely deployed (many node)
• Randomly Deployed
• Can have uncovered regions
• Left unattended to perform the task
• Maintenance is difficult
• managing connectivity
• detecting failures

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Structured model

• Deployed in a pre-planned manner
• Fewer nodes
• Lower network maintenance
• Lower cost
• No uncovered regions

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WSN constraints

• Resource constraints
• limited energy
• short communication range
• low bandwidth
• limited processing
• limited storage
• Design constraints
• application dependent
• environment dependent
• size of the network / number of node
• deployment scheme
• network topology (obstacle)

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Available sensors in the market

• Generic nodes (take measurements)
• Light, Temperature, Humidity, barometric
  pressure, velocity, Acceleration, Acoustics,
  magnetic field
• Gateway (bridge) node
• gather data from generic sensors and relay them
  to the base station
• higher processing capability
• higher battery power
• higher transmission (radio) range

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Types of sensor network

• Depending on the environment
• terrestrial WSN
• Ad Hoc (unstructured)
• Preplanned (structured)
• underground WSN
• Preplanned
• more expensive equipment, deployment, maintenance
• underwater WSN
• fewer sensor nodes( sparse deployment)
• more expensive than terrestrial
• acoustic wave communication
• Limited bandwidth
• long propagation delay
• signal fading

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Types of sensor network (cont.)

• Depending on the environment
• multi-media WSN
• sensor nodes equipped with cameras and
  microphones
• pre-planned to guarantee coverage
• High bandwidth/low energy, QoS, filtering, data
  processing and compressing techniques
• mobile WSN
• ability to reposition and organize itself in the
  network
• Start with Initial deployment and spread out to
  gather information
• deployment, localization, self-organization,
  navigation and control, coverage, energy,
  maintenance, data process

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WSN applications
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WSN applications (Open research issues)

• application-specific characteristics and
  requirements of
• environmental monitoring
• health monitoring
• industrial monitoring
• Military tracking
• Coupled with todays technology
• Lead to different hardware platforms and software
  development
• more experimental work is necessary to make these
  applications more reliable and robust in the real
  world
• Applying sensor technology to industrial
  applications will improve business

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Tasks Classification

• Systems
• Each sensor node is an individual system
• Development of new platforms, operating systems,
  and storage schemes
• Communication protocols
• Between sensors
• In different layer(app, trspt, net, DLink, phy)
• services
• which are developed
• to enhance the application
• to improve system performance
• and network efficiency

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Internal sensor system

• sensor platform
• radio components
• processors
• Storage
• sensors (multiple)
• OS
• OS must support these sensor platforms
• researches
• Designing platforms that support
• automatic management
• optimizing network longevity,
• distributed programming

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Platform Sample 1(Bluetooth-based sensor
networks)

• WSN typically uses single freq (Share channel)
• BTnodes use spread-spectrum transmission
• A special version of TinyOS is used
• Two radio communication
• Master (up to 7 connection)
• Slave
• Note
• Bluetooth is connection oriented
• New node enables its slave radio
• Topology connected tree
• high throughput, high energy consumption

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Platform Sample 2VigilNet(Detection-and-classifi
cation system)

• detection and classification
• vehicles
• persons
• persons carrying ferrous objects
• 200 sensor nodes with
• Magnetometer
• motion sensor,
• and a microphone
• deployed in a preplanned manner
• four tiers hierarchical architecture
• sensor-level,
• node-level,
• group-level,
• and base-level

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Internal sensor system Standards

• IEEE 802.15.4
• standard for low rate wireless personal area
  networks (LR-WPAN)
• low cost deployment
• low complexity
• low power consumption
• topology star and peer-to-peer
• physical layer 868/915 MHz 2.4 GHz
• MAC layer CSMA-CA mechanism

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Internal sensor system Standards

• ZigBee
• higher layer communication protocols built on the
  IEEE 802.15.4 standards for LR-PANs.
• simple, low cost, and low power
• embedded applications
• can form mesh networks connecting hundreds to
  thousands of devices together.
• types of ZigBee devices
• ZigBee coordinator stores information, bridge
• ZigBee router link groups of devices
• ZigBee end device sensors, actuators communicate
  only to routers

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Internal sensor system Standards

• IEEE 802.15.3
• physical and MAC layer standard high data rate
  WPAN.
• support real-time multi-media streaming
• data rates (11 Mbps to 55 Mbps)
• time division multiple access (TDMA) gtQoS
• synchronous and asynchronous data transfer
• wireless speakers, portable video, wireless
  connectivity for gaming, cordless phones,
  printers, and televisions

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Internal sensor system Standards

• WirelessHART (released in September 2007)
• Process measurement and control applications
• based on IEEE 802.15.4
• supports channel hopping, and time-synchronized
  messaging
• Security with encryption, verification,
  authentication and key management
• support mesh, star, and combined network
  topologies
• manages the routing and network traffic

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Internal sensor system Standards

• ISA100.11a
• defines the specifications for the OSI layer,
  security, and system management
• low energy consumption, scalability,
  infrastructure, robustness
• interoperability with other wireless devices
• use only 2.4 GHz radio and channel hopping to
  minimize interference
• provides simple, flexible, and scaleable security
  functionality.

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Internal sensor system Standards

• 6LoWPAN
• IPv6-based Low power Wireless Personal Area
  Networks
• over an IEEE 802.15.4 based network.
• Low power device can communicate directly with IP
  devices using IPbased protocols
• Wibree
• designed for low power consumption, short-range
  communication, and low cost devices
• is designed to work with Bluetooth
• operates on 2.4 GHz
• data rate of 1 Mbps
• linking distance is 510 m.
• was released publicly in October 2006.

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Internal sensor system Storage

• problems
• storage space is limited
• Communication is expensive
• Solutions
• Aggregation and compression
• query-and-collect (selective gathering)
• a storage model to satisfy storage constraints
  and query requirements
• GEM Graph Embedding
• provides an infrastructure for routing and
  data-centric storage
• choosing a labeled guest graph
• embed the guest graph onto the actual sensor
  topology
• Each node has a label encoded with its position
• each data item has a name that can be mapped to a
  label
• TSAR Two-tier sensor storage architecture
• Multi-resolution storage provides storage and
  long-term querying of the data for data-intensive
  applications

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Internal sensor system Testbeds

• Provides researchers a way to test their
  protocols, algorithms, network issues and
  applications in real world setting
• Controlled environment to deploy, configure, run,
  and monitoring of sensor remotely
• Some testbeds
• ORBIT Open access research testbed for next
  generation wireless networks
• 64 nodes, 1 GHZ
• MoteLab web-based WSN testbed
• central server handles scheduling, reprogramming
  and data logging of the nodes
• Emulab remotely accessible mobile and wireless
  sensor (such as a robot)

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Internal sensor system Diagnostics and debugging
support

• Measure and monitor the sensor node performance
  of the overall network
• to guarantee the success of the sensor network in
  the real environment
• Sympathy
• is a diagnosis tool for detecting and debugging
  failures in sensor networks
• designed for data-collection applications
• detects failures in a system by selecting metrics
  such as
• Connectivity
• data flow
• nodes neighbor
• can identify three types of failures self, path
  and sink
• Analysis of data packet delivery
• packet delivery performance at the physical and
  MAC layers

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Internal sensor system Open research issues

• optimization of (HW, SW, HW/SW) to make a WSN
  efficient
• more practical platform solution for problems in
  new applications
• data structure
• Performance
• energy-efficient storage
• Performance
• communication throughput when network size
  increases
• Scalability issues can degrade system performance
• Optimizing protocols at different layers
• services to handle node before and after failures

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Network services

• Localization
• Synchronization
• Coverage
• Compression and aggregation
• Security

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Network services Localization

• Problem
• determining the nodes location (position)
• Solutions
• global positioning system (GPS)
• Simple
• Expensive
• outdoor
• beacon (or anchor) nodes
• does not scale well in large networks
• problems may arise due to environmental
  conditions
• proximity-based
• Make use of neighbor nodes to determine their
  position
• then act as beacons for other nodes

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Network services Localization

• Other solutions
• Moores algorithm
• distributed algorithm for location estimation
  without the use of GPS or fixed beacon (anchor)
  nodes
• algorithm has three phases
• cluster localization phase
• cluster optimization phase
• cluster transformation phase

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Network services Localization

• Other solutions
• RIPS Radio Interferometric Positioning System
• Two radio transmitters create an interference
  signal at slightly different frequencies
• At least two receivers are needed to measure
  relative phase of two signal
• The relative phase offset is a function of the
  relative positions

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Network services Localization

• Other solutions
• Secure localization
• goal is to prevent malicious beacon nodes from
  providing false location to sensors
• Sensors must only accept information from
  authenticated beacon nodes
• Sensors should be able to request location
  information at anytime
• Upon a location request, information exchange
  must take place immediately and not at a later
  time.
• SeRloc, Beacon Suite, DRBTS, SPINE, ROPE

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Network services Localization

• Other solutions
• MAL Mobile-assisted localization
• Mobile node collects distance information between
  itself and static sensor nodes for node
  localization
• given a graph with measured distance edges

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Network services Synchronization

• Time synchronization is important for
• routing
• power conservation
• Lifetime
• Cooperation
• Scheduling

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Network services Synchronization

• Uncertainty-driven approach
• Lucarellis algorithm
• Reachback firefly algorithm (RFA)
• Timing-sync protocol for sensor network (TPSN)
• CSMNS
• Time synchronization (TSync)
• Global synchronization

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Network services Synchronization

• Synchronization protocol classification
• application-dependent features approaches
• single-hop vs. multi-hop networks
• stationary vs. mobile networks
• MAC layer-based vs. standard-based
• synchronization issues
• adjusting their local clocks to a common time
  scale
• masterslave synchronization
• peer-to-peer synchronization
• clock correction
• untethered clocks
• internal synchronization,
• external synchronization,
• Probabilistic synchronization,
• deterministic synchronization,
• sender to receiver synchronization,
• and receiver-to-receiver synchronization.

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Network services Coverage

• Is important in evaluating effectiveness
• Degree of coverage is application dependent
• Impacts on energy conservation
• Techniques
• selecting minimal set of active nodes to be awake
  to maintain coverage
• sensor deployment strategies

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Network services Compression and aggregation

• Both of them
• reduce communication cost
• increase reliability of data transfer
• Data-compression
• compressing data before transmission to base
• Decompression occurs at the base station
• no information should be lost
• data aggregation
• data is collected from multiple sensors
• combined together to transmit to base station
• Is used in cluster base architectures

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Network services Security

• Constraints in incorporating security into a WSN
• limitations in storage
• limitations in communication
• limitations in computation
• limitations in processing capabilities

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Network services Open research issues

• localization
• efficient algorithms
• minimum energy
• minimum cost
• minimum localization errors
• Coverage optimizing for better energy
  conservation
• time synchronization minimizing uncertainty
  errors over long periods of time and dealing with
  precision
• compression and aggregation Development of
  various scheme
• event-based data collection
• continuous data collection
• Secure monitoring protocols have to monitor,
  detect, and respond to attacks
• It has done for network and data-link layer (can
  be improved)
• Should be done for different layers of the
  protocol stack
• Cross-layer secure monitoring is another research
  area

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Communication protocol

• Transport layer
• Network layer
• Data-link layer
• Physical layer

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Communication protocol Transport layer

• Packet loss
• may be due to
• bad radio communication,
• congestion,
• packet collision,
• memory full,
• node failures
• Detection and recovering
• Improve throughput
• Energy expenditure

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Communication protocol Transport layer

• Congestion control/packet recovery
• hop-by-hop
• intermediate cache
• more energy efficient (shorter retransmission)
• higher reliability
• end-to-end
• source caches the packet
• Variable reliability

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Communication protocol Transport layer

• Sensor transmission control protocol (STCP)
• Price-oriented reliable transport protocol (PORT)
• GARUDA
• Delay sensitive transport (DST)
• Pump slowly, fetch quickly (PSFQ)
• Event-to-sink reliable transport (ESRT)
• Congestion detection and avoidance (CODA)

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Communication protocol Transport layer (Open
research issues)

• cross-layer optimization
• selecting better paths for retransmission
• getting error reports from the link layer
• Fairness
• assign packets with priority
• frequently-changing topology
• Congestion control with active queue management

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Communication protocol Transport layer
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Communication protocol Network layer

• Important
• energy efficiency
• traffic flows
• Routing protocols
• location-based considers node location to route
  data
• cluster-based employs cluster heads to do data
  aggregation and relay to base station

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Communication protocol Network layer (Open
research issues)

• Future research issues should address
• Security
• Experimental studies regarding security applied
  to different routing protocols in WSNs should be
  examined
• QoS
• guarantees end-to-end delay and energy efficient
  routing
• node mobility
• handle frequent topology changes and reliable
  delivery

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Communication protocol Network layer
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Communication protocol Data-link layer (Open
research issues)

• system performance optimization
• Cross-layer optimization
• Cross-layer interaction can
• reduce packet overhead on each layer
• reduce energy consumption
• Interaction with the MAC layer provide
• congestion control information
• enhance route selection
• Comparing performance of existing protocols of
  static network in a mobile network
• improve communication reliability and energy
  efficiency

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Communication protocol Data-link layer
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Communication protocol Physical layer

• Bandwidth choices
• Radio architecture
• Modulation schemes

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Communication protocol Physical layer (Open
research issues)

• Minimizing the energy consumption
• Optimizing of circuitry energy
• reduction of wakeup and startup times
• Optimizing of transmission energy
• Modulation schemes
• Future work
• new innovations in low power radio design with
  emerging technologies
• exploring ultra-wideband techniques as an
  alternative for communication
• creating simple modulation schemes to reduce
  synchronization and transmission power
• building more energy-efficient protocols and
  algorithms

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Communication protocol Physical layer
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Communication protocol Cross-layer interactions
(Open research issues)

• Collaboration between all the layers to achieve
  higher
• energy saving
• network performance
• network lifetime

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Communication protocol Cross-layer interactions
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Conclusion

• Large number of application is exist regarding to
  WSN
• Large number of work has done on WSN
• There are still many open issue research in WSN
• Open research area
• Application-specific characteristic
• Power efficient algorithm
• Cross-layer optimization
• more experimental work to reach more reliability
• Improvement of existing protocol
• Security
• Error reduction in localization

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Main references

• Ian F. Akyildiz, Weilian Su, Yogesh
  Sankarasubramaniam, and Erdal Cayirci, A Survey
  on Sensor Networks, IEEE Communications Magazine,
  August 2002
• Ian F. Akyildiz, Ismail H. Kasimoglu, Wireless
  sensor and actor networks research challenges,
  Elsevier Ad Hoc Networks 2 (2004) 351367
• Jennifer Yick, Biswanath Mukherjee, Dipak Ghosal,
  Wireless sensor network survey, Elsevier Computer
  Networks 52 (2008) 22922330