20-1©2010 Raj JainCSE574sWashington University in St. LouisWireless Sensor NetworksWireless Sensor NetworksRaj Jain Washington University in Saint LouisSaint Louis, MO [email protected]/Video recordings of this lecture are available at:http://www.cse.wustl.edu/~jain/cse574-10/20-2©2010 Raj JainCSE574sWashington University in St. LouisOverviewOverview Sensor Applications IEEE 802.15.4-2006 6LowPAN WirelessHART Research Issues20-3©2010 Raj JainCSE574sWashington University in St. LouisSensor ApplicationsSensor ApplicationsBattlefield Surveillance Chemical, Biological WeaponsHabitat exploration of animals Patient heart rate, blood pressureCrops and AgricultureForest Fires and Flood Detection20-4©2010 Raj JainCSE574sWashington University in St. LouisSensor (vs. AdSensor (vs. Ad--Hoc)Hoc) Large scale Batteries may not be replaceable May not have global identifiers Queries may be data centric rather than address centric:¾ Who's temperature is more than 95 degree vs. What is your temperature?⇒ Geographical routing, Data fusion, Data aggregation20-5©2010 Raj JainCSE574sWashington University in St. LouisIEEE 802.15.4IEEE 802.15.4--20062006 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:¾ 868.0-868.6 MHz in Europe¾ 902-928 Mhz in North America¾ 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 PHYsand modulations20-6©2010 Raj JainCSE574sWashington University in St. LouisIEEE 802.15.4 TopologiesIEEE 802.15.4 Topologies Star, Peer-to-peer, Structured star Full function and reduced function devicesTwo modes: With Beacon: Coordinator sends start beacon and stop beacon to indicate active time.¾ The time is slotted. Slotted CSMA/CA. Transmissions end at second beacon. Without Beacon: Unslotted CSMA/CA protcol with random exponential backoffRef: http://en.wikipedia.org/wiki/802.15.420-7©2010 Raj JainCSE574sWashington University in St. Louis6LowPAN6LowPAN 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. ¾ Need to compress IPv6 headers. ¾ 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 Goals20-8©2010 Raj JainCSE574sWashington University in St. LouisWirelessHARTWirelessHART A commonly used sensor network protocol stack20-9©2010 Raj JainCSE574sWashington University in St. LouisHARTHART 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. Master/slave protocol with two masters (primary, secondary) Point-to-point or multi-drop configuration Full 7 layer stack Ref:http://www.hartcomm.org/protocol/about/aboutprotocol_how.htmlTimeSignalI/O Subsystem20-10©2010 Raj JainCSE574sWashington University in St. LouisHART ProtocolsHART 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 MIB¾ Specifies the functions and features of a device¾ Device description language¾ Allows manufacturer specific features¾ Can be compiled to create management screens for devicesRef:http://www.hartcomm.org/protocol/about/aboutprotocol_specs.htmlhttp://www.hartcomm.org/hcf/documents/documents_spec_list.html20-11©2010 Raj JainCSE574sWashington University in St. LouisWirelessHARTWirelessHART 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.htmlhttp://www.hartcomm.org/protocol/training/training_resources_wihart.html20-12©2010 Raj JainCSE574sWashington University in St. LouisWirelessHART WirelessHART Field DevicesField 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 wirelessHART20-13©2010 Raj JainCSE574sWashington University in St. LouisSensor NodeSensor Node A device with sensors, networking hardware, and power Small size ⇒ Dust or MotesDARPA funded Smart Dust project (Dust Network, Inc. is a Silicon valley startup for Motes) TinyOS is a public domain operating system designed for sensor nodesTransceiverSensor 1Sensor 2A/D ConverterMemoryPowerMicrocontrollerRef: http://en.wikipedia.org/wiki/Moteshttp://en.wikipedia.org/wiki/Smartdusthttp://en.wikipedia.org/wiki/TinyOShttp://en.wikipedia.org/wiki/Dust_Networks20-14©2010 Raj JainCSE574sWashington University in St. LouisResearch IssuesResearch Issues1. Location Discovery2. Quality of a Sensor Network3. Time Synchronization4. Transport Layer Issues5. Real-Time Communication20-15©2010 Raj JainCSE574sWashington University in St. LouisLocation DiscoveryLocation 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 equations20-16©2010 Raj JainCSE574sWashington
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