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![Page 1: Ultra-low power wireless The changing landscape of WSN Kris Pister Prof. EECS, UC Berkeley (Founder & CTO, Dust Networks)](https://reader035.fdocuments.net/reader035/viewer/2022062423/56649e455503460f94b3a166/html5/thumbnails/1.jpg)
Ultra-low power wirelessThe changing landscape of WSN
Kris Pister
Prof. EECS, UC Berkeley(Founder & CTO, Dust Networks)
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Outline
• Technology status
• Standards update
• Implications
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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
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COTS DustGOAL:
• 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
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IAB Spring 2003 – Al Molnar87
5m
650mOscillator
Divider
Transmitter
Receiver (in fab)
Inductor Chip
900MHz Transmitter
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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
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2.4 GHz Transceiver Front End
• Cook et al., ISSCC 2006
• Active Area: 0.8mm2 • Zero external RF
components
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Noise Factor vs. Power Consumption
CC2420 NF, 55mW
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~2 mm^2 ASIC
Mote on a Chip? (circa 2001)
• Goals:– Standard CMOS– Low power– Minimal external components
uP SRAM
RadioADC
Temp
Ampinductor
crystal
battery
antenna
~$1
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Single-chip 802.15.4 motes
• Atmel
• Chipcon (TI)
• Ember
• Freescale
• Jennic
• Oki
• …
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System Cost, 2005
• Single-chip mote– Processor, memory
– 2.4G radio (not 802.15.4)
– Software?
Single-chip $1.50
Passives $0.20
PCB Assembly & Test $0.20
Battery $0.10
Total $2
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Radio Performance
200k Bit rate (bps)100k 300k
I RX (
mA
)
5
10
20
15
25
X cc1000
Molnar 04 (0.4mA)
X
X cc2420
XOtis 05 (0.4mA)
Cook 06 (300 W)
X
With software:10 years D cell
With software:10 years coin cell
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~4 mm^2 ASIC
Mote on a Chip
• Goals:– Standard CMOS– Low power– Minimal external components
uP SRAM
RadioADC
Temp
Ampinductor
crystal
battery
antenna
Security
Location
Time
Zero
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RF Geolocation Performance
• 1 m of measurement error = 3.3 ns
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Ranging in a Coal Mine Adit (Tunnel)
0 2 4 6 8 10 12 14 16 180
10
20
30
40
50
60
70
Distance (m)
Tim
e of
Flig
ht (n
s)
1 m Error
2 m Error
Ideal
Measured Data
Each point uses channel information derived from frequency hopping data
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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)
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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.
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Cost of Sensor Networks
Time
$
Computing Power
Sensors
Installation, Connection and Commissioning
Mesh Networking
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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
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Chevron’s Richmond Refinery
1 km
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Standards
• IEEE 802.15.4
• Zigbee
• ISA
• HART
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Low Data Rate WPAN Applications (Zigbee)
RESIDENTIAL/LIGHT
COMMERCIAL CONTROL
CONSUMER ELECTRONICS
TVVCRDVD/CDremote
securityHVAClighting controlaccess controllawn & garden irrigation
PC & PERIPHERALS
BUILDING AUTOMATION
securityHVAC
AMRlighting controlaccess control
mousekeyboardjoystick
PERSONAL HEALTH CARE
patient monitoring
fitness monitoring
INDUSTRIALCONTROL
asset mgtprocess control
environmentalenergy mgt
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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
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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
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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”
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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.
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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, …)
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Mesh, with backbone
Use powered infrastructure when you have it.Lower latencyLower power
But, if it goes away…
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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 MACMesh routing
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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
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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
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Wireless HART
• Again, still too early to tell, but…
Truth and light appear to have won
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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
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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
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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– < 10mm2
– 1A in-network average current consumption
• Baby version– 32 bit ARM; 128kB Flash; 8kB RAM– Same RF, same power– 2mm2?