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Overview of Wireless Sensor Networks in Smart Environments

This chapter delves into the enormous challenges of detecting, monitoring, and collecting data in Wireless Sensor Networks (WSNs), along with discussions on communication protocols, QoS, power management, and network standards. The chapter also covers topics such as sensor fusion, signal processing, and decision-making issues.

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Overview of Wireless Sensor Networks in Smart Environments

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  1. Chapter 2 Wireless Sensor Networks

  2. Smart Environments--- • Huge challenge • Detect, monitor, collect data • Asses & evaluate data • Formulate displays; make decisions • Need information –internal, external • Wireless Sensor Nets provide a possible solution

  3. Wireless Sensor Nets • Chapter includes large amount of networking information • Communication NW • Wireless Sensor nets • Smart Sensors • More….. • We will do an overview

  4. Network Communication • Quantity & Quality of Service (QoS) • Thruput & delays, time, loss, errors, power consumption • Topologies • Star, ring, bus • Mesh, tree • Fully connected

  5. Communication Protocols & Routing • Message header • Source, destination, etc. • Switching • Store--&--forward - buffer • Virtual cut through – header goes on • Worm hole – split message • Multiple access protocols – multiple nodes • Avoid collisions & lost data • Network Layers – 7 - OSI/RM • Open Systems Interconnection Reference Model

  6. Routing • Path from source to destination • Performance: QoS • throughput; average packet delay • Routing methods • Fixed • Adaptive • Minimum cost -- shortest path

  7. Routing • Deadlock: all nodes waiting, buffer full • Live lock: message continuously transmitted & never teaches destination • Flow control • Queues & buffers • To protect network from overload & speed mismatches; maintain QoS; freedom from deadlock

  8. Power Management • How do we power remote networks? • How do you “replace batteries”? • What is lifetime of a nw? • How can we conserve power? • MEMS (microelectromechanical systems) are under development

  9. Power Management • RFID -- radio frequency identification • Passive: no power source • Active: battery • Example: toll collection • Distance • RFID – ~25 feet • Power required for transmission increases as square of distance • Short hops vs. long distance

  10. History of Network Standards • Ethernet: mid 1970's, standardized 1979 • IEEE 802.3 • Official IEEE Ethernet standard--1983 • Fast Ethernet (10x) -- 1995 • Token Ring -- 1984 • IEEE standard -- 802.5 • High cost • ANSI Fiber optic standard--mid 1980's • Higher speed

  11. History of Network Standards 3. Gigabit Ethernet -- 1996 • GE standards -- 1999 • Supports (development of) • Client-server networks • Peer-to-Peer networks • All have equal authority • Peer-to-Peer computing (P2P) • Tasks are divided

  12. History of Network Standards 4. Wireless LAN (WLAN) -- 1997 • IEEE 802.11 standard • WiFi 802.11b • Bluetooth -- WPAN -- IEEE 802.15 • Short range RF

  13. Wireless Sensor Network • Key to gathering information for smart environments • Easy & fast installation • IEEE 1451 standards (1993) • Compatibility among manufacturers

  14. Sensors • Sensor: responds to signal (passive) • Smart Sensor: provides extra functions beyond those necessary for generating accurate representation of the sensed quantity • Virtual Sensor: physical sensor/transducer plus the associated signal conditionery & DSP required to obtain reliable estimates of the required sensory information (component of Smart Sensor) Omit section 2.3.2

  15. Self-Organization • Deployment: by ships or aircraft • Communication: wake-up, detect each, form communication network • Positioning • Relative: distributed signal processing • Absolute: reporting data related to detected target

  16. Relative Positioningaka Localization • For internode communication • Measure distances • Relatively Calibrated • Relative positions of all nodes in network are known

  17. Absolute Geographic Positioning • (Fully) Calibrated • Absolute (actual) position of each node is known • How? GPS, landmarks, beacons, etc. • At least 3 nodes in nw must know their location

  18. Ultra Wideband Radio -- WWB • Good for distributed sensor nets • Short range • Penetrates walls • Time-of-flight properties (distance) • Down to 1 cm • Range 40 meters • Very small

  19. Signal Processing/Decision Making Issues • SC -- Signal Conditioning • Noise, low amplitude, biased due to other factors such as temperature • Solutions: temperature, compensation, low-pass filtering

  20. Digital Signal Processing --DSP Sensor fusion: combining readings from many different types of sensors (e.g. seismic, acoustic, temperature) Kalman Filter: a DSP tool used to combine information from multiple sensors • Example: space program -- moon, distant probes • Reconstructs (estimates) full internal state of a system from a few measured outputs

  21. LabView • A software product from National Instruments • Popular, powerful, easy to use • Provides • Advanced DSP • Intelligent user interfaces (pg. 43) • Decision assistance • Alarm function

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