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Wireless sensor network survey
- 1. Wireless sensor networksurvey Author: Jennifer Yick, Biswanath Mukherjee, Dipak Ghosal Reported by Jiang
- 2. 2 Introduction • Subject: wireless sensornetwork (WSN) • WSN consists of spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. and to cooperatively pass their data through the network to a main location. What?
- 3. 3 Overall image A typicallyWSN consists of generic and gateway nodes.
- 4. 4 Typically WSN • A WSNtypically has little or no infrastructure. There are two types of WSNs. Structured WSN Unstructured WSN
- 5. 5 Structured WSN • Deployed ina pre-planned manner • Fewer nodes • Lower network maintenance • Lower cost • No uncovered regions
- 6. 6 Unstructured WSN • Densely deployed(many node) • Randomly Deployed • Can have uncovered regions • Left unattended to perform the task • Maintenance is difficult a . managing connectivity b. detecting failures
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- 8. 8 Requirement WSN military target tracking hazardousenvironment exploration natural disaster relief surveillance biomedical health monitoring seismic sensing
- 9. 9 Why we selectWSN ? Not traditional networks. • Power and environment constraints determine us to design a lower power, feasible, and smart network. • Sensors that are smaller, cheaper, and intelligent.
- 10. 10 About this paper • Goal:present a comprehensive review of the recent literature. a . An overview of the key issues in a WSN b. Compare different types of sensor networks c. Applications on WSN d. Internal sensor system e . Network services f. Communication protocol
- 11. 11 Key issues • Energy constraint • Qualityof service (QoS) Each sensor node is an individual system. Development should satisfy current requirement. Self-organizing Consume less power Total number and placement Address network dynamics Optimize communication and be energy efficiency
- 12. 12 Types of sensornetworks 1. terrestrial WSN • Ad Hoc (unstructured) • Preplanned (structured) 1. underground WSN • Preplanned, with additional sink nodes to relay data. • more expensive equipment, deployment, maintenance 1. underwater WSN • fewer sensor nodes( sparse deployment) • more expensive than terrestrial • acoustic wave communication – Limited bandwidth – long propagation delay – signal fading
- 13. 13 Types of sensornetworks(cont.) 4. 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 4. 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
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- 15. 15 Example: CenWits • BerkeleyMica2 sensor mote • GPS receivers • radio frequencies (RF)-based sensors • storage and processing devices
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- 17. 17 Internal sensor system • sensorplatform – radio components – processors – Storage – sensors (multiple) • OS – OS must support these sensor platforms. It’s hard to design a general platform to be applied to all applications due to requirements vary in terms computation, storage and user interface.
- 18. 18 Internal sensor system Standards • IEEE802.15.4, ZigBee • WirelessHART • ISA100.11 • IETF 6LoWPAN • IEEE 802.15.3 • Wibree
- 19. 19 Internal sensor system Standardexample: ZigBee • IEEE 802.15.4: – standard for low rate wireless personal area networks (LR-WPAN) – low cost deployment, low complexity, power consumption – topology :star and peer-to- peer – MAC layer: CSMA-CA mechanism • ZigBee – simple, low cost, and low power – embedded applications – can form mesh networks
- 20. 20 Internal sensor system Storage • problems – storagespace is limited – Communication is expensive • Solutions – Aggregation and compression – query-and-collect (selective gathering) – a storage model to satisfy storage constraints and query requirements
- 21. 21 Internal sensor system Testbeds • Providesresearchers 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
- 22. 22 Internal sensor system Testbedsexample: Orbit • a two-dimensional grid of 400 802.11 radio nodes. • dynamically interconnected into specified topologies with reproducible wireless channel models.
- 23. 23 Internal sensor system Diagnosticsand 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
- 24. 24 Network services a .Localization b. Synchronization c. Coverage d. Compression and aggregation e . Security
- 25. 25 Network services Localization • Problem: – determining thenode’s 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 • Other solutions
- 26. 26 Network services Synchronization • Time synchronizationis important for – routing – power conservation – Lifetime – Cooperation – Scheduling
- 27. 27 Network services Coverage • Is importantin 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
- 28. 28 Network services Compression andaggregation • 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
- 29. 29 Network services Security • Constraints inincorporating security into a WSN – limitations in storage – limitations in communication – limitations in computation – limitations in processing capabilities
- 30. 30 Network services Open researchissues • 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
- 31. 31 Communication protocol a .Transport layer b. Network layer c. Data-link layer d. Physical layer
- 32. 32 Communication protocol Transport layer • Packetloss – may be due to • bad radio communication, • congestion, • packet collision, • memory full, • node failures – Detection and recovering • Improve throughput • Energy expenditure
- 33. 33 Communication protocol Transport layer • Congestioncontrol/packet recovery – hop-by-hop • intermediate cache • more energy efficient (shorter retransmission) • higher reliability – end-to-end • source caches the packet • Variable reliability
- 34. 34 Communication protocol Transport layer(Openresearch 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
- 35. 35 Communication protocol Network layer • Important: – energyefficiency – 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
- 36. 36 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
- 37. 37 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
- 38. 38 Communication protocol Physical layer • Minimizingthe 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
- 39. 39 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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