Wireless Sensor Networks Raj Jain Washington University in Saint Louis Saint Louis MO 63130 Jain cse wustl edu Audio Video recordings of this lecture are available at http www cse wustl edu jain cse574 10 Washington University in St Louis CSE574s 20 1 2010 Raj Jain Overview Sensor Applications IEEE 802 15 4 2006 6LowPAN WirelessHART Research Issues Washington University in St Louis CSE574s 20 2 2010 Raj Jain Sensor Applications Battlefield Surveillance Chemical Biological Weapons Crops and Agriculture Forest Fires and Flood Detection Habitat exploration of animals Washington University in St Louis Patient heart rate blood pressure CSE574s 20 3 2010 Raj Jain Sensor vs Ad Hoc Large scale Batteries may not be replaceable May not have global identifiers Queries may be data centric rather than address centric Who s temperature is more than 95 degree vs What is your temperature Geographical routing Data fusion Data aggregation Washington University in St Louis CSE574s 20 4 2010 Raj Jain IEEE 802 15 4 2006 Low Rate Wireless Personal Area Network Physical layer used in ZigBee WirelessHART MiWi which add upper layers 10 m reach at 250 kbps 20 40 100 kbps versions Three Frequency Bands 868 0 868 6 MHz in Europe 902 928 Mhz in North America 2400 2383 5 MHs worldwide Uses Direct Sequence Spread Spectrum DSS BPSK or QPSK modulation IEEE 802 15 4a 2007 added ultra wideband and chirp spread spectrum IEEE 802 15 4c 2009 IEEE 802 15 4d 2009 adde more PHYs and modulations Washington University in St Louis CSE574s 2010 Raj Jain 20 5 IEEE 802 15 4 Topologies Star Peer to peer Structured star Full function and reduced function devices Two modes With Beacon Coordinator sends start beacon and stop beacon to indicate active time The time is slotted Slotted CSMA CA Transmissions end at second beacon Without Beacon Unslotted CSMA CA protcol with random exponential backoff Ref http en wikipedia org wiki 802 15 4 Washington University in St Louis CSE574s 20 6 2010 Raj Jain 6LowPAN IETF Working Group IPv6 over Lower Power Wireless Personal Area Networks IPv6 over IEEE 802 15 4 IEEE 802 15 4 allows 127 byte packets minus 25 byte framing overhead minus 21 bytes for AES security 81 byte IP packet IPv6 requires a min transmission unit MTU of 1280 bytes Need to compress IPv6 headers 64 bit Extended IEEE 802 addresses or 16 bit local IDs are used 6LowPAN defined an adoption layer that compresses IPv6 headers and allows PANs to be connected to regular IPv6 networks REF RFC 4944 Transmission of IPv6 Packets over IEEE 802 15 4 Networks RFC 4919 IPv6 over Low Power Wireless Personal Area Networks 6LoWPANs Overview Assumptions Problem Statement and Goals Washington University in St Louis CSE574s 20 7 2010 Raj Jain WirelessHART A commonly used sensor network protocol stack Washington University in St Louis CSE574s 20 8 2010 Raj Jain HART Highway Addressable Remote Transducer Communication between smart devices and monitoring systems 4 20 mA current loop is a commonly used analog measurement technique Low level frequency shift keying FSK over 4 20 mA analog signal 1200 bps Signal Time Master slave protocol with two masters primary secondary Point to point or multi drop configuration I O Subsystem Full 7 layer stack Ref http www hartcomm org protocol about aboutprotocol how html Washington University in St Louis CSE574s 20 9 2010 Raj Jain HART Protocols Full stack Layer 1 2 3 4 and 7 Layer 1 FSK Layer 2 Master Slave Upto 15 devices in a multi drop line Layer 3 Routing security Layer 4 end to end layer 7 Commands response data types and status Device Description Like a MIB Specifies the functions and features of a device Device description language Allows manufacturer specific features Can be compiled to create management screens for devices Ref http www hartcomm org protocol about aboutprotocol specs html http www hartcomm org hcf documents documents spec list html Washington University in St Louis CSE574s 20 10 2010 Raj Jain WirelessHART Extension of HART to Wireless Supports star and mesh topologies Self organizing and self healing Uses IEEE 802 15 4 2006 radios in 2 4GHz Frequency hopping with blacklisting to avoid used channels 128 bit AES encryption Uses multi path routing Messages alternate paths to ensure secondary paths are up Ref http www hartcomm org protocol wihart wireless how it works html http www hartcomm org protocol training training resources wihart html Washington University in St Louis CSE574s 20 11 2010 Raj Jain WirelessHART Field Devices WirelessHART adapter or builtin Gateways Connect to the backbone network Network Manager Manages routes monitors health can be integrated in to gateways or hosts Security Manager Contains list of authorized devices Distributes security keys Repeater Extends the range Adapter Attaches to devices without wirelessHART Washington University in St Louis CSE574s 20 12 2010 Raj Jain Sensor Node Power Transceiver Sensor 1 Microcontroller A D Converter Memory Sensor 2 A device with sensors networking hardware and power Small size Dust or Motes DARPA funded Smart Dust project Dust Network Inc is a Silicon valley startup for Motes TinyOS is a public domain operating system designed for sensor nodes Ref http en wikipedia org wiki Motes http en wikipedia org wiki Smartdust Washington University in St Louis http en wikipedia org wiki TinyOS http en wikipedia org wiki Dust Networks CSE574s 20 13 2010 Raj Jain Research Issues 1 2 3 4 5 Location Discovery Quality of a Sensor Network Time Synchronization Transport Layer Issues Real Time Communication Washington University in St Louis CSE574s 20 14 2010 Raj Jain Location Discovery Location Stamp on data Indoor Localization Reference nodes in each location Atomic Multi Lateration Need 3 references Iterative Multi Lateration Nodes with known location become references for others Collaborative Multi Lateration Use quadratic equations Washington University in St Louis CSE574s 20 15 2010 Raj Jain Global Positioning System GPS US Department of Defense 12B Man made stars 24 Satellites and their ground stations Triangulation Measures travel time of radio signal Distance Satellites broadcast current time and their location using a Direct Sequence Code 1023 chips per bit 3 satellites give x y z 4 satellites give x y z t Correct for any delays experienced through the atmosphere http www edu observatory org gps tutorials html Washington University in St Louis CSE574s 20 16 2010 Raj Jain Quality of a Sensor Network Quality Coverage Exposure
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