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