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

Outline Technology status Standards update Implications

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

COTS Dust 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 IAB Spring 2000

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

UCB Hardware Results ~ 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 –Microprocessor, Brett Warneke, PhD. 8 bits, 1MIP –900 MHz radio – Al Molnar M.S. 100kbps, “bits in, bits out” 20 m indoors 3V

2.4 GHz Transceiver Front End Cook et al., ISSCC 2006 Active Area: 0.8mm 2 Zero external RF components

Noise Factor vs. Power Consumption CC2420 NF, 55mW

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

Single-chip motes Atmel Chipcon (TI) Ember Freescale Jennic Oki …

System Cost, 2005 Single-chip mote –Processor, memory –2.4G radio (not ) –Software? Single-chip$1.50 Passives$0.20 PCB Assembly & Test$0.20 Battery$0.10 Total$2

Radio Performance 200k Bit rate (bps)100k 300k I RX (mA) X cc1000 Molnar 04 (0.4mA) X cc2420 X Otis 05 (0.4mA) Cook 06 (300  W) X With software: 10 years  D cell With software: 10 years  coin cell

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

RF Geolocation Performance 1 m of measurement error = 3.3 ns

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

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 85C?  85C (circuit solutions; processes get worse)

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.

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

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

Chevron’s Richmond Refinery 1 km

Standards IEEE Zigbee ISA HART

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

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 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

ISA SP100 SP –Safety critical –Feedback control SP –Monitoring –Latency-tolerant alarming CFP Conference last week –~25 proposals –2 universities both from PRC

ISA SP-100 Proposals Still too early to call, but… –Winners 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”

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.

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

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

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

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

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 – based –Time synchronized, TDMA, channel hopping, mesh routing

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

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

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

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