SMART DUST B. Boser, D. Culler, J. Kahn, K. Pister Berkeley Sensor & Actuator Center Electrical...
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Transcript of SMART DUST B. Boser, D. Culler, J. Kahn, K. Pister Berkeley Sensor & Actuator Center Electrical...
SMART DUST
SMART DUST
B. Boser, D. Culler, J. Kahn, K. Pister
Berkeley Sensor & Actuator CenterElectrical Engineering & Computer Sciences
UC Berkeley
SMART DUST
Outline
• History
• Technology Ramblings
SMART DUST
Motivation
• Exponential decrease in size, power, cost• Digital computation• Analog/RF communication• Sensors
battery
Goals• Understand fundamental limits• Build working systems
SMART DUST
Moore’s Law, take 2
• Nanochips on a dime (Prof. Steve Smith, EECS)
SMART DUST
DoD Workshops
• RAND 1992• “Future Technology-Driven Revolutions in
Military Conflict”• “Smart Chaff”, “Floating Finks”• Bruno Augenstein, Seldon Crary, Noel
Macdonald, Randy Steeb, …
• Santa Fe, 1995• Xan Alexander, Ken Gabriel; Roger Howe,
George Whitesides, …
• ISAT 1995, 1996, 1997, 1998, 1999, 2000
• …
SMART DUST
University Programs (old slide)
• UCLA• Bill Kaiser (LWIM, WINS)• Greg Pottie (AWAIRS)
• U. Michigan• Ken Wise
• USC• Deborah Estrin
• UCB• K. Pister (Smart Dust)
• …
SMART DUST
Ken Wise, U. Michigan
• http://www.eecs.umich.edu/~wise/Research/Overview/wise_research.pdf
SMART DUST
Bill Kaiser, UCLA
• http://www.janet.ucla.edu/WINS
SMART DUST
August ’01 Goal
SMART DUST
COTS Dust - RF Motes
• Simple computer• Cordless phone radio• Up to 2 year battery life
N
S
EW 2 Axis Magnetic Sensor
2 Axis Accelerometer
Light Intensity Sensor
Humidity Sensor
Pressure Sensor
Temperature Sensor
SMART DUST
COTS Dust
GOALS:
• Create a network of sensors
• Explore system design issues
SMART DUST
COTS Dust
RESULTS:
• TinyOS – David Culler, UCB
• Manufactured by Crossbow ~ $150
• 100+ users, 40+ locations
• Military and civilian applications
SMART DUST
800 node demo at Intel Developers Forum
4 sensors$70,000 / 1000Concept to demo in 30 days!
SMART DUST
Structural performance due to multi-directional ground motions (Glaser & CalTech)
.
Wiring for traditional structural instrumentation+ truckload of equipment
Mote infrastructure15
13
14
6
5`
15
118
Mote Layou
t 129
Comparison of Results
SMART DUST
Cory Energy Monitoring/Mgmt System
• 50 nodes on 4th floor• 5 level ad hoc net• 30 sec sampling• 250K samples to database over 6 weeks
SMART DUST
29 Palms Sensorweb Experiment
• Goals• Deploy a sensor network onto a road from an unmanned
aerial vehicle (UAV)• Detect and track vehicles passing through the network• Transfer vehicle track information from the ground network
to the UAV• Transfer vehicle track information from the UAV to an
observer at the base camp.
SMART DUST
Flight Data
SMART DUST
Dragon WagonFrom UAV
Dragon Wagon
HMMWVFrom UAV
HMMWV
SMART DUST
Last 2 of 6 motes are dropped from UAV
• 8 packaged motes loaded on plane
Last 2 of six being dropped
SMART DUST
Detection algorithm
bAx
t
t
t
t
t
v
p
p
p
p
4
3
2
1
4
3
2
1
/1
1
1
1
1
Each vehicle V(v,t) has two parameters:1) Speed (v)2) Time at beginning of network (t)The n-node network is described by an n-entry pattern vector p:The jth entry is the time we expect that node j will see V(1,0)
Times when nodes detect V are collected in the t vector
Linear least-squares guess at v and t
SMART DUST
Room to spare!
SMART DUST
RF Sensitivity
• Pn = kBT f Nf
• Sensitivity = Pn + SNRmin
• e.g. GSM (European cell phone standard), 115kbps
kBT 200kHz ~8x SNRS = -174dBm + 53 dB + 9 dB + 10 dB = -102 dBm
RX power = ~200mWTX power = ~4W 50 uJ/bit
SMART DUST
RF Path Loss
• Isotropic radiator, /4 dipole• Pr=Pt / (4 (d/)n)
• Free space n=2
• Ground level n=2—7, average 4
SMART DUST
N=4
From Mobile Cellular
Telecommunications,
W.C.Y. Lee
Pt = 10-50W
-102dBm
SMART DUST
Path Loss
• Like to choose longer wavelength• Loss ~(d)n
• 916MHz, 30m, 92dB power loss need –92dBm receiver for 1mW xmitter power!
• Penetration of structures, foliage, …
• But…• Antenna efficiency • Size – /4 @ 1GHz = 7.5cm
SMART DUST
Output Power Efficiency
• RF• Slope Efficiency
• Linear mod. ~10%• GMSK ~50%
• Poverhead = 1-100mW
• Optical• Slope Efficiency
• lasers ~25%• LEDs ~80%
• Poverhead = 1uW-100mW
Slope Efficiency
TrueEfficiency
Pin
Pout
Poverhead
SMART DUST
Cassini
Limits to RF Communication
• 8 GHz (3.5cm)• 20 W• 1.5x109 km• 115 kbps• -130dbm Rx• 10-21 J/bit
• kT=4x 10-21 J @300K• ~5000 3.5cm photons/bit
Canberra• 4m, 70m antennas
SMART DUST
Video Semaphore Decoding
Diverged beam @ 5.2 km
In shadow in evening sun
SMART DUST
~8mm3 laser scanner
Two 4-bit mechanical DACs control mirror scan angles.
~6 degrees azimuth, 3 elevation
1Mbps
SMART DUST
Application to Microassembly
• Pattern complementary hydrophobic shapes onto parts and substrates using SAMs.• no shape constraints on parts• no bulk micromachining of
substrate• submicron, orientational
alignment
• Uthara Srinivasan, Ph.D. thesis,UC Berkeley Chem.Eng., May 2001
Courtesy: Roger Howe, UCB
SMART DUST
Mirrors in Solution
Courtesy: Roger Howe, UCB
SMART DUST
Mirrors on Microactuators
assembled mirror
Courtesy: Roger Howe, UCB
SMART DUST
CMOS Imaging Detector
Photosensor
Signal ProcessingA/D Conversion
SIPO ShiftRegister
CRC CheckLocal Bus Driver
Off ChipBus Driver
Pixel Array
SMART DUST
Power and Energy
• Sources• Solar cells ~0.1mW/mm2, ~1J/day/mm2
• Combustion/Thermopiles
• Storage• Batteries ~1 J/mm3
• Capacitors ~0.01 J/mm3
• Usage• Digital computation: nJ/instruction• Analog circuitry: nJ/sample• Communication: nJ/bit
10 pJ27 pJ/sample
11 pJ RX, 2pJ TX
SMART DUST
Smart Dust - Processes (CMOS)
13 state
FSMcontroller
ADC70kS/s, 1.8uW
ambient lightsensor
Photodiode
Sensor input
Oscillator
Power input PowerTX Drivers0-100kbpsCCR or diode
Optical Receiver1 Mbps, 11uW
1mm
330µ
m
What’s working – Oscillator, FSM, ADC, photosensor, TX drivers
What’s kind of working – Optical receiver (stability problems lead to occasional false packets)
SMART DUST
Power, sensor, motor fab
Isolation trenches are etched through an SOI wafer and backfilled with nitride and undoped polysilicon.
SMART DUST
Power, sensor, motor fab
Solar cells and circuits are created by ion implantation, drive-in, oxidation, contact etching, aluminum sputtering and etching.
SMART DUST
Actuators are deep reactive ion etched through device layer.
Power, sensor, motor fab
SMART DUST
Optional backside etch (would actually precede front side etch)
Power, sensor, motor fab
SMART DUST
Solar Cell Results
Solar Array Performance
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0 5 10 15 20 25 30
Voltage (V)
Cu
rren
t (u
A)
0.5 to 100 V demonstrated10-14% efficiency
SMART DUST
Power from MEMS CombustionPower from MEMS Combustion
Thermopiles
Nozzle(w/ igniter)
SMART DUST
Closing in on 1mm3
2.8mm2.
1mm CCR
Accelerometer
Solar Cells
CMOS IC
SMART DUST
Smart Dust - Integration
Solar Cell Array CCR
XL
CMOSIC
16 mm3 total circumscribed volume~4.8 mm3 total displaced volume
SENSORS ADC FSMRECEIVER
TRANSMITTER
SOLAR POWER1V 1V 1V 2V3-8V
PHOTO 8-bits
375 kbps
175 bps
1-2V
OPTICAL IN
OPTICAL OUT
SMART DUST
175 bps from 10 mm3
CCR Drive Voltage
Detected Transmission
Sample from XL pad(connected to Vdd)
Echo ofDownlink data
Sample fromphotosensor
SMART DUST
Mote with Micro-battery from Lee & Lin, UCB
SMART DUST
Optical Communication
0-25% 25%
Path loss
Loss = (Antenna Gain) Areceiver / (4 d2)
Antenna Gain = 4 / ½2
SMART DUST
Theoretical Performance
Ptotal = 50mWPt = 5mW½ = 1mradBR = 5 Mbps
Areceiver = 1cm2 Pr = 10nW (-50dBm)Ptotal = 50uWSNR = 15 dB~10,000 photons/bit
5km
Photosensor
Signal ProcessingA/D Conversion
SIPO ShiftRegister
CRC CheckLocal Bus Driver
Off ChipBus Driver
Pixel Array
10nJ/bit
SMART DUST
Theoretical Performance
Ptotal = 100uWPt = 10uW½ = 1mradBR = 5 Mbps
Areceiver = 0.1mm2 Pr = 10nW (-50dBm)Ptotal = 50uWSNR = 15 dB
5m
20pJ/bit!
SMART DUST
~2 mm^2 ASIC
RF mote
• CMOS ASIC• 8 bit microcontroller• Custom interface circuits
• External components
uP SRAM
RadioADC
Temp
Ampinductor
crystal
battery
antenna
~$1
SMART DUST
Radio basics
• Tuneable frequency, 900MHz +/-100 MHz
• Programmable power output• -10 – 0 dBm out, 1 – 10 mW in• 100 kbps?
Tuneable cap.
Oscillator core
Tuneable power
13 bit freq. reg.
8 bit power reg.
uP
SMART DUST
Radio basics
• Tuneable frequency, 900MHz +/-100 MHz
• Programmable sensitivity• -100 – -90 dBm, 0.1 – 10 mW in• 100 kbps?
• Many interface options• Direct memory• Low power vigilance?
Oscillator core
DMA pointer
uP SRAM
SMART DUST
Crystal-free radio?
• ~20% variation in frequency reference in CMOS
• I measure your frequency output in my coordinate system, and vice versa
• Theory of coupled oscillators
• Digital feedback between nodes
SMART DUST
Wakeup synchronization
• Watch crystals• 32kHz, 30nW• 10-100 ppm drift
• 1-10 ms/min• 1-10 sec/day• 5-50 min/year
• Temperature is primary source of drift• Compensate to sub-ppm – 100ppb?
SMART DUST
RF Mote Summary
• Available 2003• Radio
• 900 MHz• 10+ m range• 10 nJ/bit (0.3mA, 100kbps)
• 8 bit Atmel-ish uP• 10pJ/inst (0.03mA)
• 10 bit ADC• 100kS/s, 30nJ/sample (0.01mA)
• Batteries• Lithium coin cell ~ 220mAh• AA batteries 1000mAh
SMART DUST
Abstracting the Hardware
• Goal:• Provide realistic energy (and time) metrics to
drive algorithm development• Allow software/algorithms to drive hardware
design.
Rene mote Mica moteLaptops & Wavelan
Abstract representation of hardware
Diffusion routing Routing tables…
Centralizedlocalization
Distributedlocalization
SMART DUST
Abstracting the Hardware
• Too simple:• “computation” = x pJ• Comm = y nJ/bit*m^4• Sensing = z pJ/sample
• Too complex:• 16 bit add register to non-cached main
memory = x pJ, • …
SMART DUST
Abstracting the Hardware
• Need a representation(s) of• Energy cost• Latency
• Probabilistic?
SMART DUST
Example: maximize sensor net lifetime
• Given:• Costs of sensing, computation, communication• Fixed sensor locations
• Connectivity matrix• One or more base stations
• Find:• Energy-optimal routing to get data back from each
node (define it first!)
• Everyone on all the time
• Duty cycling
SMART DUST
Example: minimal coverage
• Given:• Costs of sensing, computation, communication• Sensor range, communication range• Mote weight dominated by battery
• Find:• Minimal dispersion of motes (in kg/km2 !) st.
events x,y,z can be sensed for time t
SMART DUST
Example: minimal coverage
• Workstation?
SMART DUST
Example: minimal coverage
• Smart dust?
SMART DUST
Example: minimal coverage
• Some of both?
SMART DUST
Mobility
SMART DUST
Other topics
• Simulation of big networks
• Data fusion/compression
• Information theory• Shannon for sensor networks• What is “capacity”?
• Collaborative signal processing• Definition• Existence?
SMART DUST
Summary
• Cubic-inch RF motes working in applications
• 10 mm3 optical motes demonstrated
• 10 mm3 RF motes coming
• Peer-to-peer networking
• Most communication is relay
• Energy cost to communicate 1 bit is at least 1000x greater than an 8 bit instruction
SMART DUST
Conclusion
1 mm3 or bust!!!