System Architecture Directions for Networked Sensors J Hill et al Presented By Sarah Bergbreiter EE249 Discussion Section October 15 2002 1 EE249 Discussion What are Networked Sensors Mica Mote 1mm Smart Dust Cheap plentiful low power small communication enabled radio optical etc 2 EE249 Discussion Networked Sensor Characteristics Small physical size and low power consumption Concurrency Intensive Operation sensing data forwarding packets etc Limited Physical Parallelism and Controller Hierarchy can t have one processor per sensor Diversity in Design and Usage modular components allow for application specific design Robust Operation numerous and unattended 3 EE249 Discussion Sample Hardware Design Coprocessor reprogramming Sensors Radio 1 J bit real time constraints 4 Atmel AVR power save modes memory constrained EE249 Discussion TinyOS Overview Small size and power limitations decided by the hardware platform Two Level Scheduling long running tasks processing data hardware events radio sensors etc Event Driven Design better concurrency power savings Modular Component Based Design 5 EE249 Discussion MSG SEND DONE MSG REC SEND MSG INIT Commands Events Frame POWER TinyOS Design Components static fixed 6 TX PACKET DONE INTERNAL STATE FRAME RX PACKET DONE TX PACKET Type depends on hardware connection POWER simulate concurrency MESSAGING COMPONENT INIT Tasks SEND MSG THREAD EE249 Discussion Ad hoc Routing Application 3 6 4 5 4 7 5 3 8 6 2 9 7 1 2 1 7 EE249 Discussion How Does TinyOS Perform Small Physical Size scheduler uses 178 bytes program memory 16 bytes data memory application 3k program memory 226 bytes data memory Concurrency intensive Operations context switching relatively cheap equivalent to writing 6 bytes in memory interrupt handling more expensive in software 8 EE249 Discussion How Does TinyOS Perform Efficient Modularity using function calls to propagate events and commands keeps costs low 40 s 90 s 9 EE249 Discussion How Does TinyOS Perform Limited Physical Parallelism and Controller Hierarchy make design choices about parallelism based on data Diversity in Usage and Robust Operation reconfigurable for node failure 10 EE249 Discussion Related Work Other Operating Systems These operating systems address embedded PCs Control v dataflow context switching difficult FSM Description Language New Hardware Platforms and Applications 11 EE249 Discussion Architectural Implications Physical parallelism is optional Deciding where to draw the hardware software boundary line may improve performance and or power usage Quantified effect of additional hardware support early benchmarks 12 EE249 Discussion Conclusions Questions Sample hardware software architecture presented for networked sensors Bigger is no longer better Platform based design Complexity limits 13 EE249 Discussion
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