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Ultra-low power wireless The changing landscape of WSN

Explore the transformation in WSN technology landscape from autonomous microsensor networks to single-chip motes with optimized power consumption and performance. Dive into the advancements in RF systems, software-defined radio, and network protocols. Discover the potential of sensor networks for diverse applications across industries.

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Ultra-low power wireless The changing landscape of WSN

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  1. Ultra-low power wirelessThe changing landscape of WSN Kris Pister Prof. EECS, UC Berkeley (Founder & CTO, Dust Networks)

  2. Outline • Technology status • Standards update • Implications

  3. Autonomous Microsensor Networks with Optical Communication Links IAB 1997 • PI: Kris Pister • Source: Hughes (MICRO) • Funding: $25k, $10k matching, 0% ovhd, • Duration: 1 year • Comments: Collaboration w/ Prof. Joe Kahn under separate MICRO

  4. COTS Dust IAB Spring 2000 GOAL: • Get our feet wet RESULT: • Cheap, easy, off-the-shelf RF systems • Fantastic interest in cheap, easy, RF: • Industry • Berkeley Wireless Research Center • Center for the Built Environment (IUCRC) • PC Enabled Toys (Intel) • Fantastic RF problems • Optical proof of concept

  5. IAB Spring 2003 – Al Molnar 900MHz Transmitter 650mm Oscillator Divider Transmitter Receiver (in fab) 875mm Inductor Chip

  6. UCB Hardware Results ~2003 • 2 chips fabbed in 0.25um CMOS • “Mote on a chip” worked, TX only • 900 MHz transceiver worked • Records set for low power CMOS • ADC, Mike Scott, M.S. • 8 bits, 100kS/s • 2uA@1V • Microprocessor, Brett Warneke, PhD. • 8 bits, 1MIP • 10uA@1V • 900 MHz radio – Al Molnar M.S. • 100kbps, “bits in, bits out” • 20 m indoors • 0.4mA @ 3V

  7. 2.4 GHz Transceiver Front End • Cook et al., ISSCC 2006 • Active Area: 0.8mm2 • Zero external RF components

  8. Noise Factor vs. Power Consumption CC2420 NF, 55mW

  9. Mote on a Chip? (circa 2001) antenna uP SRAM Temp inductor Amp Radio ADC ~2 mm^2 ASIC crystal battery • Goals: • Standard CMOS • Low power • Minimal external components ~$1

  10. Single-chip 802.15.4 motes • Atmel • Chipcon (TI) • Ember • Freescale • Jennic • Oki • …

  11. System Cost, 2005 • Single-chip mote • Processor, memory • 2.4G radio (not 802.15.4) • Software?

  12. Radio Performance 25 20 With software: 10 years  D cell 15 IRX (mA) 10 5 With software: 10 years  coin cell 100k Bit rate (bps) 300k 200k X cc2420 X cc1000 Cook 06 (300 mW) X Molnar 04 (0.4mA) X X Otis 05 (0.4mA)

  13. Mote on a Chip Zero antenna inductor ~4 mm^2 ASIC crystal battery • Goals: • Standard CMOS • Low power • Minimal external components uP Security SRAM Temp Location Amp Radio ADC Time

  14. RF Geolocation Performance • 1 m of measurement error = 3.3 ns

  15. Ranging in a Coal Mine Adit (Tunnel) 2 m Error Measured Data Ideal 1 m Error Each point uses channel information derived from frequency hopping data

  16. Die area, power • ADC • Zero area, zero power • Digital • 32 bit uP 1mm2 0.25mm2 • Crypto - ~ uP • Dedicated datapath? • 0.25mW/MHz  50uW/MHz • Memory • ROM & Flash 128kB/mm2 0.5MB/mm2 • RAM 16kB/mm2  64kB/mm2 • ~mW/MHz  ~ uW/MHz • RF • 2mm2  1mm2 • 10s of mW  100s of uW • Leakage • 10s uA @ 85C?  <1uA @ 85C (circuit solutions; processes get worse)

  17. Conclusion • Today’s motes have more computational horsepower than many/most(/all?) of the first machines on the internet. • Today’s motes have radios that have comparable performance to 1G cell phones. • Network protocols that take advantage of these revolutions will have roughly the same hardware cost as those that don’t.

  18. Cost of Sensor Networks Mesh Networking Computing Power Installation, Connection and Commissioning Sensors $ Time

  19. Oil Refinery – Double Coker Unit • Scope limited to Coker facility and support units spanning over 1200ft • Expanded to 27 units, implemented 14 to start • No repeaters were needed to ensure connectivity • Gateway connected via Ethernet port in control room to process control network • Electrical/Mechanical contractor installed per wired practices GW

  20. Chevron’s Richmond Refinery 1 km

  21. Standards • IEEE 802.15.4 • Zigbee • ISA • HART

  22. Low Data Rate WPAN Applications (Zigbee) PERSONAL HEALTH CARE BUILDING AUTOMATION CONSUMER ELECTRONICS security HVAC AMR lighting control accesscontrol TV VCR DVD/CD remote PC & PERIPHERALS INDUSTRIAL CONTROL asset mgt process control environmental energy mgt mouse keyboard joystick RESIDENTIAL/ LIGHT COMMERCIAL CONTROL patient monitoring fitness monitoring security HVAC lighting control access control lawn & garden irrigation

  23. Zigbee • Zigbee 1.0 ratified in 2004 • Great marketing tool, but… • Nothing interoperable yet • “Zigbee” products typically aren’t • Everything shipped to date is IEEE 802.15.4 + proprietary MAC • Lost industrial automation in 2005 • Losing building automation in 2006? • Fighting Zensys in home automation • Latest: Zigbee Pro • “The stack that works”  • Hot debate on frequency hopping

  24. ISA SP100 • http://www.ISA.org/community/SP100 • SP100.11 • Safety critical • Feedback control • SP100.14 • Monitoring • Latency-tolerant alarming • CFP Conference last week • ~25 proposals • 2 universities • both from PRC

  25. ISA SP-100 Proposals • Still too early to call, but… • Winners • 802.15.4 • TDMA • Frequency hopping • Losers • RF site surveys • Point-to-point communication • Narrow band, high power • Zigbee • Walking dead • Single-hop to wired infrastructure • Star-connected networks • Truth and light appears to be winning! • Truth: the guys running the plants • Light: time synchronized, TDMA, channel hopping, mesh routing • Tough battles • “We are at war with Dust Networks in industrial automation”

  26. Star-mesh or Star-LAN Q: Star-connectivity is known to be death for reliability, so why do it? A: Don’t trust the motes, don’t think that they have the power to be routers.

  27. Star-mesh or Star-LAN What if WiFi gets jammed (easier to do than freq-hopping 802.15.4)? What if you lose ethernet? (power failure, cable, …)

  28. Mesh, with backbone Use powered infrastructure when you have it. Lower latency Lower power But, if it goes away…

  29. Mesh, with backbone Assume that the motes are smart, and that their radios are good. Use protocols that leverage those capabilities: Time-synchronized, TDMA, Channel Hopping MAC Mesh routing

  30. Wireless Cost Profiles Reduced Wiring Costs Service Curve: Site Surveys and Expert Tuning Technology Curve: Self-Organizing and Self-Optimizing “There’s good money to be made in RF site surveys” - Name withheld to protect the guilty Cost Wired System Cost Star Wireless + Service Self-Organizing Wireless + Simple Radios New Automation Opportunities Time

  31. Wireless HART • Highway Addressable Remote Transducer • 20 years old • HART today: • Wired industrial automation protocol • 1200 bps digital communication on top of 4-20mA analog communication line • Shipping ~3Million/year • ASP ~$1k • Installation cost (wiring dominated): ~$10k? • Wireless HART group formed in 2004 • 802.15.4 based • Time synchronized, TDMA, channel hopping, mesh routing

  32. Wireless HART • Again, still too early to tell, but… Truth and light appear to have won

  33. Implicatons for Industrial Automation • Cost of installation:sensor was 10:1, going to 1:10 • Size of sensor market will increase • “New” requirement on sensors to be low energy per sample • New applications possible • Condition-based maintenance • Tracking

  34. Implications • “For several years I was a skeptic, but I now believe that wireless mesh sensor networks will have higher reliability than wired sensors.” • Refinery technologist • “Yup.” - ksjp

  35. Next generation capabilities • Coming soon: • 32 bit ARM; 1MB flash; 64kB RAM • 2.4GHz RF, bps to Mbps, ~1nJ/bit • ~ ms synchronization across network • ~ 1 meter location accuracy • < 10mm2 • 1mA in-network average current consumption • Baby version • 32 bit ARM; 128kB Flash; 8kB RAM • Same RF, same power • 2mm2?

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