Presentation on theme: "A System Architecture for Tiny Networked Devices"— Presentation transcript:
1 A System Architecture for Tiny Networked Devices Jason HillU.C. Berkeley9/22/2000
2 Who We Are: The Tiny OS Group Jason Hill – CS Grad StudentRobert Szewczyk – CS Grad StudentAlec Woo – CS Grad StudentSeth Hollar – EE Grad StudentDavid Culler (Prof.)Kris Pister (Prof.)
3 Goals:To develop an ultra low power networked sensor platform, including hardware and software, that enables low-cost deployment of sensor networks.To be a system level bridge that combines advances in low power RF technology with MEMS transducer technology.
4 Key Characteristics of TNDs Small physical size and low power consumption=> Limited Physical Parallelism and Controller Hierarchy=> primitive direct-to-device interfaceConcurrency-intensive operationflow-thru, not wait-command-respond=> must handle multiple inputs and outputs simultaneouslyDiverse in Design and Usageapplication specific, not general purposehuge device variation=> efficient modularity=> migration across HW/SW boundaryLargely Unattended & Numerous=> robust operation=> narrow interfaces
6 Tiny OS – The SoftwareProvides a component based model abstracting hardware specifics from application programmerUtilizes an event based programming model to allow high levels of concurrencyAllows multiple applications to be “running”Services Provided Include:Active Messages Based messaging protocolPeriodic Timer EventsAsynchronous access to UART data transfersMechanism for Static, Persistent StorageCan “Swap Out” system components to get necessary functionality.Complete applications fit in 4KB of ROM and 256B RAM.
7 Second Generation ‘Mote’ Two Board SandwichMain CPU board with Radio CommunicationSecondary Sensor BoardAllows for expansion and customizationCurrent sensors include: Acceleration, Magnetic Field, Temperature, Pressure, Humidity, Light, and RF Signal Strength.Can control RF transmission strength
8 Multi-Hop Routing Demo Sensors automatically assemble and determine routing topologyParallel Breadth First SearchShortest path to all nodes rememberedBase station broadcasts out routing informationIndividuals listen for and propagate route updateN messages sentGenerational scheme to prevent cycles in routing tableBase
9 Demo (cont.) Sensor information propagated up routing tree Statistics kept for number of readings received and number of packets forwarded by each nodeSensors transmit data when “significant” events occur or when time limit is exceededMust be continuously listening for packets to be forwarded – impacts power considerations
10 Short Term Goals: Deploy sensor net in Soda for week long trial runs Amass a collection of hundreds of first generation nodesImprove Radio communication reliabilityBring online second generation hardwareTarget Civil Engineering’s and The Center For the Built Environment’s needs to get a real world deployment.Support applications where data is “picked up” by UAV’s
11 Tiny OS Internals Scheduler and Graph of Components constrained two-level scheduling model: tasks + eventsComponent:Frame (storage)Tasks (concurrency)Commands, and Handlers (events)Constrained Storage Modelframe per component, shared stack, no heapVery lean multithreadingLayeringcomponents issue commands to lower-level componentsevent signal high-level events, or call lower-level commandsGuarantees no cycles in call chain
13 Event Based Prog. Model System composed of state machines Each State Machine is a TinyOS “component”Command and event handlers transition a component from one state to anotherQuick, low overhead, non-blocking state transmissionsAllows many independent components to share a single execution contextEmerging as design paradigm for large scale systems“Tasks” are used to perform computational workRun to completion, Atomic with respect to each other
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