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Ultra-low power and ultra-low cost wireless sensor nodes An integrated perspective. Jan M. Rabaey EECS Dept. Univ. of California, Berkeley. PicoRadio’s ─ The Original Mission. Meso-scale low-cost radio’s for ubiquitous wireless data acquisition that are fully integrated - PowerPoint PPT Presentation
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Jan M. Rabaey
EECS Dept.
Univ. of California, Berkeley
Ultra-low power and ultra-low costUltra-low power and ultra-low costwireless sensor nodeswireless sensor nodes An integrated perspectiveAn integrated perspective
Meso-scale low-cost radio’s for ubiquitous wireless data acquisition that • are fully integrated
–Size smaller than 1 cm3
• minimize power/energy dissipation – Limiting power dissipation to 100 W enables energy scavenging
• and form self-configuring ad-hoc networks containing 100’s to 1000’s of nodes
Meso-scale low-cost radio’s for ubiquitous wireless data acquisition that • are fully integrated
–Size smaller than 1 cm3
• minimize power/energy dissipation – Limiting power dissipation to 100 W enables energy scavenging
• and form self-configuring ad-hoc networks containing 100’s to 1000’s of nodes
PicoRadio’s ─ The Original Mission PicoRadio’s ─ The Original Mission
Still valid, but pushing the limits ever further
The Incredibly Shrinking RadioThe Incredibly Shrinking Radio
RF Filter LNA
fclock
RF FilterEnvDet
fclock
RF FilterEnvDet
RF Filter LNA
fclock
RF FilterEnvDet
fclock
RF FilterEnvDet
RXOn: 3 mWOff: 0 mW
RXOn: 3 mWOff: 0 mW
MatchingNetwork
MOD1
MOD2
OSC1
OSC2 Preamp PAMatchingNetwork
MOD1
MOD2
OSC1
OSC2 Preamp PA
TXOn: 4 mW
Stby: 1 mWOff: 0 mW
TXOn: 4 mW
Stby: 1 mWOff: 0 mW
Receiver
RF Amp Test
LNATest
Diff Osc
PA Test
TX1
TX2Env Det Test
Passive Test Structures • Technology: 0.13 m CMOS
combined with off-chip FBARs• Carrier frequency: 1.9 GHz• 0 dBm OOK• Two Channels• Channel Spacing ~ 50MHz• 40 kbps/channel• Total area < 8 mm2
• Technology: 0.13 m CMOS combined with off-chip FBARs• Carrier frequency: 1.9 GHz• 0 dBm OOK• Two Channels• Channel Spacing ~ 50MHz• 40 kbps/channel• Total area < 8 mm2
4 m
m
Wireless Sensor Network Protocol ProcessorWireless Sensor Network Protocol Processor
In fab (Jan 04)
Technology 0.13μ CMOS
Chip Size 3mm x 2.75mm =8.2 mm2
Transistor Count 3.2M
Gate Count 62.5K gates
Clocks Freqs 16MHz(Main), 1MHz(BB)
On Chip memory 68Kbytes
Core Supply Voltages
1V(High) –0.3V(Low)
On_Power < 1 mW
Standby Power Ws
64Kmemory DW8051
μc
BaseBand
SerialInterface
GPIOInterface
LocationingEngine
Neighbor List
SystemSupervisor
DLL
NetworkQueues
VoltageConv
Integrates all digital protocol and applications functions of
wireless sensor node
Runs reliable and energy-optimizedprotocol stack (from application level down)
VoltageSupply
VoltageSupply
20MHzClock Source
VoltageSupply
OOKReceiver
FlashStorage
Sensor2Sensor1
PrgThresh0 PrgThresh1
OOKTransmitter
Tx0 Tx2User
Interface
SIF = sensor interface
LocalHW
MAC
DW8051
256DATA
sfrbus or membus?
ADC
4kBXDATA
16kBCODE
PHY
ChipSupervisor
SIF
SIFADC
Serial
GPIO
FlashIF
Serial
DigitalNetworkProcessor
RF Transceiver
Solar Cell
The Road towards a First Integrated PicoNodeThe Road towards a First Integrated PicoNode
PowertrainPowertrain
Board
Desig
n In P
roce
ss
Energy-Scavenging becoming a RealityEnergy-Scavenging becoming a Reality
Tx COB
Front
cap
regulator
Front
• Demonstrate a self contained 1.9GHz transmitter - powered only by Solar & Vibrational scavenged energy
• Push integration limits - limited by dimensions of solar cell
Light Level Duty CycleLow Indoor Light 0.36%
Fluorescent Indoor Light 0.53%Partly Cloudy Outdoor Light 5.6%
Bright Indoor Lamp 11%High Light Conditions 100%
Vibration Level Duty Cycle2.2m/s2
1.6%5.7m/s2
2.6%
Perspectives: Where are we heading?Perspectives: Where are we heading?• Extrapolating towards the future: how far
can we push cost, size, and power?– Ultra-dense sensor networks (“smart surfaces”)
enabled by sub 10 W nodes.– Cutting RF power by at least another factor of 5 (if
not more)– Pushing the boundaries on voltage scaling
• Focus on the application perspective– A Service-based Application Interface for Sensor
Networks– Focus on issues such as portability, universality ,
scalability, and ad-hoc deployment
An Application Perspective to Sensor NetworksAn Application Perspective to Sensor NetworksA plethora of implementation strategies emerging, some of them being translated into standards
TinyOs/TinyDB
The juggernaut is rolling … but is it the right approach?• Bottom-up definition without perspective on interoperability and portability• Little reflection on how this translates into applications
Network Layer
Service Layer
A Quest: A Universal Application Interface A Quest: A Universal Application Interface (AI) for Sensor Networks(AI) for Sensor Networks
• Supports essential services such as queries, commands, time synchronization, localization, and concepts repository
• Similar in concept to the socket interface in the internet• Provides a single point for providing interoperability• Independent of implementation architecture and hardware platform
– Allows for alternative PHY, MAC, and Network approaches and keeps the door open for innovation
ApplicationApplication Interface
Query/Command
Naming
Time/Synchronization
Location
SNSP
SNSP Status (joint project with SNSP Status (joint project with GSRC (ASV) and TU Berlin)GSRC (ASV) and TU Berlin)• White paper completed and in feedback gathering
mode (http://bwrc.eecs.berkeley.edu/research/picoradio/...)
• Very positive support so far (both from industry and academia)
• Next targets:– Further evolve document (start working group)– Demonstrate feasibility by implementation on at least two test beds– Address number of issues left open for research (e.g.
implementation approaches for naming, synchronization, localization, and concept repository services)
• Currently in process of acquiring funding (NSF, European Commission, CEC, …)
Extrapolation of the low-power theme: Extrapolation of the low-power theme: Ultra-dense sensor networks Ultra-dense sensor networks • How to get nodes substantially smaller and
cheaper (“real” mm3 nodes): get them closer, use lots of them, and make their energy consumption absolutely minimal (this is < 10 W).
• “Smart surfaces”: plane wings, smart construction materials, intelligent walls
• How to get there? Go absolutely non-traditional!– Use non-tuned mostly passive radio’s – center
carrier frequency randomly distributed – Use statistical distribution to ensure reliable data
propagation
On the Road:On the Road:Reducing RF power by another factor of 5Reducing RF power by another factor of 5• Providing gain at minimal current: The Super-regenerative
Receiver 1500m
12
00
m
• Fully Integrated
• 400A when active(~200W with 50% quench duty cycle)
Back from fab any day
Realizing sub-50 Realizing sub-50 W receiversW receivers
Supply voltage 0.5 – 1.2V
Current consumption
150μA
Oscillation frequency
1.5GHz
Differential output swing
150mV
(Vdd=500mV)
Phase noise -100dBc/Hz
@1MHz offset
Simulated PerformanceExample: sub-threshold RF oscillatorusing integrated LCs (in fab)
Next step: mostly untuned radio’s and lots of themCombine with purely statistical routing (in collaboration with Kannan)
Ultra-Low Voltage (ULV) Digital DesignUltra-Low Voltage (ULV) Digital Design• Aggressive voltage scaling the premier way of reducing
power consumption; Performance not an issue• Our goals: design at 250 mV or below• Challenges:
– Wide variation in gate performance due to variability of thresholds and device dimensions
– Sensitivity to dynamic errors due to noise and particle-caused upsets (soft errors)
Explore circuit and architecture techniques that deal with performance variations and are (somewhat) resilient to errors!
TM
TM TM
TMsynch.
asynch.
Ch
ip S
up
erviso
r
Time reference
Tcl
Tcl’
Idea: Self-adapting approach to ULVStatus: White paper