Sensor Networks: The Vision • Push connect ivit y out of t he PC and int o t he real world Wireless Sensor Networks • Billions of sensors and act uat ors EVERYWHERE !!! • Zero conf igurat ion Lecture 8 – CS252 • Build everyt hing out of CMOS so t hat each device costs pennies • Enable wild new sensing paradigms C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 1 Lec 8. 2 Why Now? Real World Apps… Combination of : • Breakthroughs in MEMS technology • Development of low power radio technologies • Advances in low - power embedded microcontrollers C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 3 Lec 8. 4 Cory Energy Monitoring/ Mgmt Vehicle Tracking Syst em • 50 nodes on 4 th f loor • 5 level ad hoc net • 30 sec sampling • 250K samples to database over 6 weeks C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 5 Lec 8. 6 1
St ruct ural perf ormance due t o mult i - direct ional ground mot ions (Glaser & Node Localization CalTech) Mot e inf rast ruct ure Mote 1 Layout 5 1 1 1 4 6 ` 1 5 5 3 29 “Best Fit” 1 8 1 Regression Noise Error Error Error Error • Reducing Noise • Reducing Error 60 60 • Results Regression Comparison of Results RSSI Calibration Noise Localization 50 cm 50 cm 20 cm 40 cm 60 c m 80 cm 100 c m Distance Kamin Whitehouse. Nest Retreat 2/13/2002 4 Wir ing f or t r adit ional st ruct ural inst rument at ion + t r uckload of equipment C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 7 Lec 8. 8 Sensor Network Algorithms Recipe For Architectural Research • Direct ed Dif f usion – Dat a cent ric rout ing 1. Take known workload (Est rin, UCLA) 2. Analyze perf ormance on current syst ems • Sensor Net work Query Processing (Madden, 3. Form hypothesis on ways of improving UCB) “perf ormance” • Dist ribut ed Dat a Aggregat ion 4. Build new syst em based on hypot hesis • Localizat ion in sensor net works (UCLA, UW, 5. Re- analyze same workload on new system USC, UCB) 6. Publish results • Multi- object t racking/ Pursuer Evader (UCB, NEST) • Security C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 9 Lec 8. 10 Our Approach… . Sensor Node Requirements 1. Hypothesize about requirements based on potential • Low Power, Low Power, Low Power… applications • Support Multi- hop Wireless Communicat ion 2. Explore design space based on these requirements • Self Conf iguring 3. Develop hardware platf orm f or experimentation • Small Physical Size 4. Build test applications on top of hardware platf orm 5. Evaluate perf ormance characteristics of applications • Can Reprogram over Net work 6. GOTO step 1 (hopef ully you’ll come up with a better • Meet s Research Goals set of requirements) – Operating system exploration – Enables exploration of algorithm space – I nstrumentation – Network architecture exploration C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 11 Lec 8. 12 2
First Decision: The central Major Axes of Microcontroller controller Diversity • Flash based vs. SRAM based • What will control the device? – Combinat ion of FLASH and CMOS logic is dif f icult • I nternal vs. External Memory • Modern Microcontroller Sidebar • Memory Size – What ’s inside a microcont roller t oday? • Digital Only vs. On- chip ADC – What peripheral equipment do you need • Operating Voltage Range t o support one? • Operating Current, Power States and wake- up times • P hysical Size – How do you program one? • Support Circuitry Required – External Clocks, Voltage Ref erences, RAM • Peripheral Support – SPI , USART, I 2C, One- wire • Cycle Counters • Capture and Analog Compare C S252/ Hill • Tool Chain C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 13 Lec 8. 14 C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 15 Lec 8. 16 Second Decision: Radio What is in your cell phone? Technologies • Texas I nst rument ’s TCS2500 Chipset • Major RF Devices – Cordless Phones Digit al/ Analog » Single Channel – Cellular Phones » Multi- channel, Base st at ion cont rolled – 802. 11 » “wireless Ethernet” – Bluetooth ARM9, 120Mhz » Emerging, low- power f requency >> 270.833 + DSP hopping kbps C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 17 Lec 8. 18 3
RFM TR1000 Radio TR 1000 internals • 916. 5 Mhz f ixed carrier f requency • No bit timing provided by radio • 5 mA RX, 10 mA TX • Receive signal digitized based on analog thresholds • Able to operate in OOK (10 kb/ s) or ASK (115 kb/ s) mode • 10 Kbps design using programmed I / O • Design SPI - based circuit to drive radio at f ull speed – f ull speed on TI MSP, 50 kb/ s on ATMEGA • I mproved Digitally controlled TX strength DS1804 – 1 f t to 300 f t transmission range, 100 steps • Receive signal strength detector C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 19 Lec 8. 20 Why not use f ederation of Can you do this with a single CPUs? CPU? • Divide App, RF, Storage and Sensing • Reproduce PC I / O hierarchy • Dedicated communications processor could greatly reduce protocol stack overhead and complexity • Providing physical parallelism would create a partition between applications and communication protocols • I solating applications f rom protocols can prove costly Apps CPU Flexibility is Key to success Sensing CPU St orage CPU RF CPU Radio Sensors St orage C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 21 Lec 8. 22 What is the sof tware The RENE architecture environment? • Atmel AT90LS8535 51-Pin I/O Expansion Connector 8 Programming Digital I/O 8 Analog I/O Lines – 4 Mhz 8- bit CPU • Do I run JI NI ? Java? – 8KB I nstruction Memory – 512B RAM AT90LS8535 Microcontroller • What about a real time OS? – 5mA active, 3mA idle, SPI Bus <5uA powered down Transmission Coprocessor Power Control • I P ? Sockets? Threads? • 32 KB EEPROM TR 1000 Radio Transceiver 32 KB External EEPROM – 1- 4 uj/ bit r/ w • RFM TR1000 radio – Programmed I / O • Why not? – 10 kb/ s – OOK • Network programmable • 51- pin expansion connector • GCC based tool/ programming chain 1.5”x1” form factor C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 23 Lec 8. 24 4
TinyOS Key Sof tware Requirements • OS/ Runt ime model designed t o manage t he • Capable of f ine grained high levels of concurrency required concurrency • Gives up I P, sockets, threads • Small physical size • Uses state- machine based programming • Ef f icient Resource Utilization concept s t o allow f or f ine grained concurrency • Highly Modular • Provides the primitive of low- level message • Self Conf iguring delivery and dispat ching as building block f or all dist ribut ed algorit hms C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 25 Lec 8. 26 State Machine Programming Tiny OS Concepts Model • Scheduler + Graph of Component s Events Commands – constrained two- level scheduling model: _rec(type, data) • System composed of state machines threads + events power(mode) type, data) g s send_m • Command and event handlers • Component : (addr, _sen d_done) init transition modules f rom one state to – Commands, msg msg – Event Handlers another Messaging Component – Frame (storage) – Quick, low overhead, non- blocking state Internal – Tasks (concurrency) TX_packet(buf) internal thread transitions Power(mode) State • Const rained St orage Model • Many independent modules allowed to – f rame per component, shared stack, no init et_done et_done TX_pack (success RX_pack ef f iciently share a single execution (buffer) heap cont ext ) • Very lean mult it hreading • Ef f icient Layering C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 27 Lec 8. 28 Application = Graph of Components System Analysis application Route map router sensor appln • Af ter building apps, system is highly memory constrained Active Messages • Communication bandwidth is limited by packet CPU overhead at key times. Radio Packet Serial Packet Temp photo SW Communication has bursty phases. Example: ad hoc, multi-hop routing of photo sensor • Where did the Energy/ Time go? byte UART HW Radio byte readings ADC – 50% of CPU used when searching f or packets 3450 B code 226 B data – With 1 packet per second, >90% of energy goes bit clocks RFM to RX! Graph of cooperating state machines on shared stack C S252/ Hill C S252/ Hill 2/ 14/ 02 2/ 14/ 02 Lec 8. 29 Lec 8. 30 5
Recommend
More recommend
