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Introduction to Wireless Sensor Networks (WSNs)

Learn about wireless sensor networks (WSNs), which are distributed networks of autonomous sensor nodes that monitor physical or environmental conditions and communicate wirelessly. Explore WSN applications, challenges, and requirements.

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Introduction to Wireless Sensor Networks (WSNs)

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  1. Introduction to Wireless SensorNetworks (WSNs)

  2. What is WSN ?A wireless sensor network (WSN) is a wireless network consisting of spatially distributed (autonomous devices using sensors) nodes to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations. Sensing.....>Processing.....>Communicating

  3. What is WSN? • Wireless Sensor Networks are networks that consists of sensor nodes which are • distributed in an ad hoc manner. • These sensors work with each other to sense some physical phenomenon and then • the information gathered is processed and communicate to the user wirelessly. • Wireless sensor networks consists of protocols and algorithms with self-organizing • capabilities. Wireless Network Technology Computational WSN Power SensorTechnology

  4. WSN Node Components  Networks of typically small, battery-powered,wireless devices. On-board processing, Communication, and Sensors P Sensing capabilities. O W Storage Processor E R Radio WSN device schematics

  5. Picture of Mote (sensor node)

  6. WSN: “Motes”

  7. Objective

  8. Application Spectrum Interactive VR Game Wearable Disaster Recovery Environmental Monitoring Computing Earth Science & Exploration Context-Aware Computing Wireless Sensor Networks Transportation BiologicalMonitoring Hazard Detection Smart Environment Urban Warfare Medical Military Surveillance Domain

  9. WSN application examples  Disaster relief operations Drop sensor nodes from an aircraft over a wildfire Each node measures temperature Derive a “temperature map” Biodiversity mapping  Use sensor nodes to observe wildlife Intelligent buildings (or bridges)  Reduce energy wastage by proper humidity, ventilation, air conditioning (HVAC) control Needs measurements about room occupancy, temperature, air flow, … Monitor mechanical stress after earthquakes

  10. WSN application scenarios  Facility management Intrusion detection into industrial sites Control of leakages in chemical plants, …  Machine surveillance and preventive maintenance Embed sensing/control functions into places no cable has gone before E.g., tire pressure monitoring Precision agriculture Bring out fertilizer/pesticides/irrigation only where needed Medicine and health care Post-operative or intensive care Long-term surveillance of chronically ill patients or the elderly

  11. WSN application scenarios  Logistics Equip goods (parcels, containers) with a sensor node Track their whereabouts - total asset management Note: passive readout might suffice - compare RF IDs Telematics Provide better traffic control by obtaining finer-grainedinformation about traffic conditions Intelligent roadside Cars as the sensor nodes

  12. Types of Applications • Event Detection Eg: a temperature threshold is exceeded • Periodic Measurements Eg: in medical applications • Function approximation and edge detection Eg: to find the isothermal points in forest fire application to detect the border of the actual fire • Tracking Eg: an intruder(mobile) in surveillance

  13. Challenges  Challenges Limited battery power Limited storage and computation Lower bandwidth and high error rates Scalability to 1000s of nodes Network Protocol Design Goals Operate in self-configured mode (no infrastructurenetwork support) Limit memory footprint of protocols Limit computation needs of protocols -> simple, yetefficient protocols Conserve battery power in all ways possible

  14. Characteristic requirements for WSNs • Type of service of WSN Not simply moving bits like another network Rather: provide answers or meaningful information(not just numbers) Issues like geographic scoping are natural requirements, absent from other networks • Quality of service-type of network service Traditional QoS metrics(bandwidth,delay) do not apply Still, service of WSN must be “good”: Right answers at the right time. Reliable detection of events is important. eg.temp. map • Fault tolerance Be robust against node failure (running out of energy, physical destruction, …) • Lifetime The network should fulfill its task as long as possible - definition depends on application Lifetime of individual nodes relatively unimportant But often treated equivalently

  15. Characteristic requirements for WSNs Scalability Support large number of nodes Wide range of densities Vast or small number of nodes per unit area, very application-dependent  Programmability Re-programming of nodes in the field might be necessary, improve flexibility  Maintainability WSN has to adapt to changes(failing nodes,new tasks), self-monitoring, adapt operation Incorporate possible additional resources, e.g., newly deployed nodes

  16. Required mechanisms to meet requirements  Multi-hop wireless communication Energy-efficient operation Both for communication and computation, sensing,actuating  Auto-configuration Manual configuration just not an option Collaboration & in-network processing Nodes in the network collaborate towards a joint goal Pre-processing data in network (as opposed to at theedge) can greatly improve efficiency

  17. Required mechanisms to meet requirements  Data centric networking Focusing network design on data, not onnode identifies (id-centric networking) To improve efficiency Locality Do things locally (on node or among nearbyneighbors) as far as possible  Exploit tradeoffs E.g., between invested energy and accuracy

  18. MANET vs. WSN  Many commonalities: - Self-organization, energy efficiency, (often) wireless multi-hop  Many differences:- Applications, equipment: MANETs more powerful ( expensive) equipment assumed, often “human in the loop”-type applications, higherdata rates, more resources Application-specific: WSNs depend much stronger on application specifics; MANETs comparably uniform Environment interaction: core of WSN, absent in MANET Scale: WSN might be much larger (although contestable) Energy: WSN tighter requirements, maintenance issues Dependability/QoS: in WSN, individual node may be dispensable (network matters), QoS different because of different applications Data centric vs. id-centric networking Mobility: different mobility patterns like (in WSN, sinks might be mobile, usual nodes static)

  19. Enabling technologies for WSN  Cost reduction For wireless communication, simplemicrocontroller, sensing, batteries  Miniaturization Some applications demand small size “Smart dust” as the most extreme vision Energy scavenging Recharge batteries from ambient energy(light, vibration, …)

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