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Wireless Embedded Systems (0120442x) Ad hoc and Sensor Networks

Wireless Embedded Systems (0120442x) Ad hoc and Sensor Networks. Chaiporn Jaikaeo chaiporn.j@ku.ac.th Department of Computer Engineering Kasetsart University. Materials taken from lecture slides by Karl and Willig. Typical Wireless Networks. Base stations connected to wired backbone

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Wireless Embedded Systems (0120442x) Ad hoc and Sensor Networks

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  1. Wireless Embedded Systems(0120442x)Ad hoc and Sensor Networks Chaiporn Jaikaeo chaiporn.j@ku.ac.th Department of Computer EngineeringKasetsart University Materials taken from lecture slides by Karl and Willig

  2. Typical Wireless Networks • Base stations connected to wired backbone • Mobile nodes communicate wirelessly to base stations

  3. wireless wired multi-hop wireless Ad hoc Networks • Networks without pre-configured infrastructure • require no hubs, access points, base stations • are instantly deployable • can be wired or wireless • Initially targeted for military and emergency applications

  4. 802.11 Ad hoc Mode • IEEE 802.11 already provides support for ad hoc mode • Computers can be connected without an access point • Only work with single hop

  5. Possible Applications for Ad hoc Networks Factory Floor Automation Disaster recovery Car-to-car communication

  6. Characteristics of Ad hoc Networks • Heterogeneity ― sensors, PDAs, laptops • Limited resources ― CPU, bandwidth, power • Dynamic topology due to mobility and/or failure • Mobile Ad hoc Networks (MANETs) B C A

  7. Sensor Networks • Participants in the previous examples were devices close to a human user, interacting with humans • Alternative concept: Instead of focusing interaction on humans, focus on interacting with environment • Network is embedded in environment • Nodes in the network are equipped with sensing and actuation to measure/influence environment • Nodes process information and communicate

  8. sensor field Remotemonitoring Traditional Sensors Network Data loggers Localmonitoring

  9. sensor field Remotemonitoring Wireless Sensors • Sensors communicate with data logger via radio links Network radio link

  10. Gateway Internet Remotemonitoring Wireless Sensor Networks • Wireless sensors + wireless network • Sensor nodes (motes) deployed and forming an ad hoc network • Requires no hubs, access points • Instantly deployable • Targeted applications • Emergency responses • Remote data acquisition Sensor node/mote Sensor network

  11. WSN Platforms • Most are based on IEEE 802.15.4 (Wireless Low-Rate Personal Area Network) and many others…

  12. WSN Application Examples • Agriculture • Humidity/temperaturemonitoring • Civil engineering • Structural response • Disaster management • Environmental sciences • Habitat monitoring • Conservation biology

  13. Browser InformationServer GPRSNetworkor Internet Gateway WSN in Telemetry Applications sensor sensor wireless sensor node Sensor field

  14. Landslide Monitor • Real deployment scenario…

  15. Roles of Participants in WSN • Sources of data: Measure data, report them “somewhere” • Typically equip with different kinds of actual sensors • Sinks of data: Interested in receiving data from WSN • May be part of the WSN or external entity, PDA, gateway, … • Actuators (actors): Control some device based on data, usually also a sink WSN = WASN

  16. Classifying Application Types • Interaction patternsbetween sources and sinks classify application types • Event detection • Periodic measurement • Function approximation • Edge detection • Tracking

  17. Deployment Options • Dropped from aircraft • Random deployment • Well planned, fixed • Regular deployment • Mobile sensor nodes • Can move to compensate for deployment shortcomings • Can be passively moved around by some external force (wind, water) • Can actively seek out “interesting” areas

  18. Maintenance Options • Feasible and/or practical to maintain sensor nodes? • Replace batteries • Unattended operation • Impossible but not relevant • Energy supply • Limited from point of deployment • Some form of recharging / energy scavenging

  19. Characteristic Requirements • Type of service of WSN • Not simply moving bits like another network • Rather: provide answers (not just numbers) • Geographic scoping are natural requirements • Quality of service • Fault tolerance • Lifetime: node/network • Scalability • Wide range of densities • Programmability • Maintainability

  20. Required Mechanisms • 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 the edge) can greatly improve efficiency

  21. Required Mechanisms • Data centric networking • Focusing network design on data, not on node identifies (id-centric networking) • To improve efficiency • Locality • Do things locally (on node or among nearby neighbors) as much as possible • Exploit tradeoffs • E.g., between invested energy and accuracy

  22. MANET vs. WSN - Similarities • MANET – Mobile Ad hoc Network • Self-organization • Energy efficiency • (Often) Wireless multi-hop

  23. MANET vs. WSN - Differences • Equipment: MANETs more powerful • Application-specific: WSNs depend much stronger on application specifics • Environment interaction: core of WSN, absent in MANET • Scale: WSN might be much larger (although contestable) • Energy: WSN tighter requirements, maintenance issues

  24. MANET vs. WSN - Differences • Dependability/QoS: in WSN, individual node may be dispensable (network matters), QoS different because of different applications • Addressing: Data centric vs. id-centric networking

  25. Enabling Technologies for WSN • Cost reduction • For wireless communication, simple microcontroller, system on chip, sensing, batteries • Miniaturization • Some applications demand small size • “Smart dust” as the most extreme vision • Energy scavenging • Recharge batteries from ambient energy (light, vibration, …)

  26. Conclusion • MANETs and WSNs are challenging and promising system concepts • Many similarities, many differences • Both require new types of architectures & protocols compared to “traditional” wired/wireless networks • In particular, application-specificness is a new issue

  27. Demonstration

  28. Sensor Modules • IWING-MRF modules from IWING LAB • 250 kbps 2.4GHz IEEE 802.15.4 • 12MHz Atmel ATMega328P microcontroller • Additional light and temperature sensors

  29. Scenario Monitor station Sensor nodes measuring light intensity

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