CS 525 Advanced Distributed Systems Spring 09A Gram of Gold=How Many Processors?Sensor Networks Hype, But do we really need this technology?Slide 4Sensor NodesExample: Berkeley “Motes” or “Smart Dust”Example HardwareExamplesTypes of SensorsI2C bus – simple technologyTransmission MediumSlide 12Summary: Sensor NodeSensor-node Operating SystemTinyOS design pointProgramming TinyOSA Complete TinyOS ApplicationTinyOS component modelSteps in writing and installing your NesC appTinyOS FactsSlide 21Slide 22TinyOS: More Performance NumbersTinyOS: SizeTinyOS: SummaryDiscussionSystem RobustnessScalabilityEtceteraSummary: Distributed Protocols for Sensor Systems…Other ProjectsCivilian Mote Deployment Examples1CS 525 Advanced Distributed SystemsSpring 09Indranil GuptaLecture 6Introduction to Sensor NetworksFebruary 10, 20092A Gram of Gold=How Many Processors?•Smallest state-of-the-art transistor today is made of a single Gold atom–Still in research, not yet in industry.•Pentium P4 contains 42 M transistors•Gold atomic weight is 196 ~ 200. •1 g of Au contains 3 X 10^21 atoms => 7.5 X 10^18 P4 processors from a gram of Au => 1 billion P4’s per person3Sensor Networks Hype, But do we really need this technology?•Coal mines have always had CO/CO2 sensors•Industry has used sensors for a long timeToday…•Excessive Information–Environmentalists collecting data on an island–Army needs to know about enemy troop deployments–Humans in society face information overload•Sensor Networking technology can help filter and process this information (And then perhaps respond automatically?)4Growth of a technology requiresI. HardwareII. Operating Systems and ProtocolsIII. Killer applications–Military and Civilian5Sensor Nodes•Motivating factors for emergence: applications, Moore’s Law, wireless comm., MEMS (micro electro mechanical sensors)•Canonical Sensor Node contains1. Sensor(s) to convert a different energy form to an electrical impulse e.g., to measure temperature2. Microprocessor3. Communications link e.g., wireless4. Power source e.g., battery6Laser diodeIII-V processPassive CCR comm.MEMS/polysiliconSensorMEMS/bulk, surface, ...Analog I/O, DSP, ControlCOTS CMOSSolar cellCMOS or III-VThick film batterySol/gel V2O5Power capacitorMulti-layer ceramic1-2 mmExample: Berkeley “Motes” or “Smart Dust”Can you identify the 4 components here?7Example Hardware•Size–Golem Dust: 11.7 cu. mm–MICA motes: Few inches•Everything on one chip: micro-everything–processor, transceiver, battery, sensors, memory, bus–MICA: 4 MHz, 40 Kbps, 4 KB SRAM / 512 KB Serial Flash, lasts 7 days at full blast on 2 x AA batteries8ExamplesSpec, 3/03 • 4 KB RAM• 4 MHz clock• 19.2 Kbps, 40 feet• Supposedly $0.30MICA: xbowSimilar i-motes by Intel9Types of Sensors•Micro-sensors (MEMS, Materials, Circuits)–acceleration, vibration, gyroscope, tilt, magnetic, heat, motion, pressure, temp, light, moisture, humidity, barometric, sound•Chemical–CO, CO2, radon•Biological–pathogen detectors•[Actuators too (mirrors, motors, smart surfaces, micro-robots) ]10I2C bus – simple technology•Inter-IC connect–e.g., connect sensor to microprocessor•Simple features–Has only 2 wires –Bi-directional–serial data (SDA) and serial clock (SCL) bus •Up to 3.4 Mbps•Developed By Philips11Transmission Medium•Spec, MICA: Radio Frequency (RF)–Broadcast medium, routing is “store and forward”, links are bidirectional•Smart Dust : smaller size but RF needs high frequency => higher power consumption Optical transmission: simpler hardware, lower power–Directional antennas only, broadcast costly–Line of sight required–Switching links costly : mechanical antenna movements–Passive transmission (reflectors) => wormhole routing–Unidirectional links12Berkeley Family of Motes13Summary: Sensor Node•Small Size : few mm to a few inches•Limited processing and communication–MhZ clock, MB flash, KB RAM, 100’s Kbps (wireless) bandwidth•Limited power (MICA: 7-10 days at full blast)•Failure prone nodes and links (due to deployment, fab, wireless medium, etc.)•But easy to manufacture and deploy in large numbers•Need to offset this with scalable and fault-tolerant OS’s and protocols14Sensor-node Operating SystemIssues–Size of code and run-time memory footprint•Embedded System OS’s inapplicable: need hundreds of KB ROM–Workload characteristics•Continuous ? Bursty ?–Application diversity•Want to reuse sensor nodes–Tasks and processes•Scheduling•Hard and soft real-time–Power consumption–Communication15TinyOS design point–Bursty dataflow-driven computations–Multiple data streams => concurrency-intensive–Real-time computations (hard and soft)–Power conservation–Size–Accommodate diverse set of applications TinyOS: –Event-driven execution (reactive mote)–Modular structure (components) and clean interfaces16Programming TinyOS•Use a variant of C called NesC•NesC defines components•A component is either –A module specifying a set of methods and internal storage (~like a Java static class) A module corresponds to either a hardware element on the chip (e.g., the clock or the LED), or to a user-defined software module Modules implement and use interfaces–Or a configuration, a set of other components wired together by specifying the unimplemented methods •A complete NesC application then consists of one top level configuration17A Complete TinyOS ApplicationRFMRadio byteRadio Packeti2cTempphotoMessaging LayerclocksbitbytepacketRouting Layersensing applicationapplicationHWSWADCmessagingrouting18TinyOS component model•Component specifies:•Component invocation is event driven, arising from hardware events•Static allocation only avoids run-time overhead•Scheduling: dynamic, hard (or soft) real-time•Explicit interfaces accommodate different applicationsInternal StateInternal TasksCommands Events19Steps in writing and installing your NesC app(applies to MICA Mote)•On your PC–Write NesC program –Compile to an executable for the mote–Plug the mote into the parallel port through a connector board–Install the program•On the mote–Turn the mote on, and it’s already running your application20TinyOS Facts•Software Footprint 3.4 KB •Power Consumption on Rene PlatformTransmission Cost: 1 µJ/bitInactive State: 5 µAPeak Load: 20 mA•Concurrency support: at peak load CPU is asleep 50% of
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