Polymorphic Radios: A new design paradigm for ultra-low ...

PolymorphicRadios:Anewdesignparadigmforultra-lowpowercommunication

MohammadRostami,JeremyGummeson,AliKiaghadi,DeepakGanesan,UniversityofMassachusettsAmherst

Why do we need a new low-power radio?

Evolving communication needs

Cloud

Gateway

Connectivity(circa1995)

Streaming(circa2015)

Evolving communication needs

Cloud

Connectivity(circa1995)

EdgeCloud

Streaming(circa2015)

What about radio power consumption?

Challenge:Low-powerradiosoptimizedforsporadicratherthanstreamingcommunication.

cloudoffload

What about radio power consumption?

Goal:Designalow-powerstreamingradiothatprovideslow-latencyconnectivityandisreliableunderdynamics.

cloudoffload

How can we optimize a streaming radio?

RXsensitivity

RSS

(dB

m)

-92

-62

30dBgap

How do radios leverage the gap?

Transmitquickly(akaduty-cycling)

sleep

active

Transmitsoftly(akapowercontrol)

RXsensitivity

RSS

(dB

m)

-92

-62

30dBgap

0dBm

-30dBm



Oscillator

LNA/PA

Mixer

lowefficiencyatlowoutputpower

0dBm

-30dBm




State-of-artlow-poweractiveradio(NordicnRF5):- 16mW@0dBm- 8mW@-40dBm

0dBm

-30dBm





0dBm

-30dBm

State-of-artBLE(NordicnRF5):- 16mW@0dBm- 8mW@-40dBm


Transmitquickly(akaduty-cycling)- Faster⇒higheron-offoverhead- Shorter⇒lesschannelvisibility


0dBm

-30dBm

State-of-artBLE(NordicnRF5):- 16mW@0dBm- 8mW@-40dBm

Can we use passive radios?Active Radios Passive Radios

Oscillator

LNA/PA

Mixer

BackscatterTX

EnvelopeDetectorRX

Can we use passive radios?

Active Radios Passive Radios

Oscillator

LNA/PA

Mixer

BackscatterTX

EnvelopeDetectorRX

powerefficiency

reliability

How about passive radios?


powerefficiency

reliabilityCar

rier W

ave

Car

rier W

ave

Refle

cted

Sig

nal

How about passive radios?

powerefficiency

reliability

LNARX

Active Rx Passive Rx

Sensitivity=-92dBm Sensitivity=-50dBm


Key Challenge

reliablebutinefficient

Active RF

efficientbutunreliable

Passive RF

Polymorphic Radios

Active RF Passive RF

Reliability

Power

Late

ncy Polymorphicradios:Combineactiveandpassivebuildingblockstodesignlow-

powerstreamingradios.

Two modes of operation


active-assistedpassive

Mode 1: Active-assisted Backscatter

ActiveRadio

PassiveRadioReceiveSensitivity

@100kbpsRec

eive

d Si

gnal

Str

engt

h

Mode 1: Active-assisted Backscatter

ActiveRadio

PassiveRadio

Rec

eive

d Si

gnal

Str

engt

h

Two modes of operation


active-assistedpassive

passive-assistedactive

Mode 2: Backscatter-assisted Active

ActiveRadio

PassiveRadio

RSS

RSS

@100kbps

@3kbps

@100kbps

Rxsensitivitydependsonenergy-per-bit

Mode 2: Backscatter-assisted Active

ActiveRadio

PassiveRadio

RSS

RSS

@100kbps

@3kbps

Near-ZeroPowerChannelMeasurement

Polymorphic radio in a nutshell


Whenpassiveworkswell,useactivesparinglyforreliability

Whenpassiveworkspoorly,usetomonitorchannelandoptimizeactiveduty-cycling.

Roadmap: Network Stack

Application

MAC

PHY PolymorphicRadioHW

RadioSelection/Switching

StreamingVideo/Audio

Hardware Overview

~PA

LNA

Fast Envelope Detector

Slow Envelope Detector

Tx Baseband

Rx Baseband

Backscatter SwitchChannel Meas. Shift Reg.

Splitter

~PA

LNA



Tx Baseband

Rx Baseband


Splitter

Hardware Overview

ActiveRadio

~PA

LNA



Tx Baseband

Rx Baseband


Splitter

Hardware Overview

Passive-Backscatter

~PA

LNA



Tx Baseband

Rx Baseband


Splitter

Hardware Overview

Passive-EnvelopeDetector

Hardware Benchmarks

ModeSwitching-Latency 30µs

ActiveMode [email protected],900MHz

BackscatterMode10µW(measurement)50µW(data)

RF Osc.ASK Mod

ASK Demod

Ant.

Envelope detectors

Splitter

~PA

LNA



Tx Baseband

Rx Baseband


Splitter

MAC - Decision Engine

Imputed RSS

Decision Engine

TX mode

RX modeTX bitrate

RX bitrate

RSSmeasuredinactivemode

RSSmeasuredinpassivemode

P(RSS > RSStinnextkslots |RSSt, . . . , RSSt−10)

MAC Evaluation - DatasetsWristIMU StreamingIMUdata@100samples/secfromaSmartwatch

LapelAudio Streamingaudio@4kHzsamplingratefromaLapelaccessory(dialog)

Eyeglasscamera Streamingvideo@30fpsfromlowpowercameraonaneyeglass

Packet loss rate (%)0 10 20 30 40 50

Ener

gy e

ffici

ency

(bits

/nJ)

0.1

1

10

100

T1

T1

T1

T2

T2

T2

T3

T3

T3

Energy-efficiency vs. Reliability

Backscatter

Duty-cycledActive

Packet loss rate (%)0 10 20 30 40 50

Ener

gy e

ffici

ency

(bits

/nJ)

0.1

1

10

100

T1

T1

T1

T2

T2

T2

T3

T3

T3

Energy-efficiency vs. Reliability

Polymorphic(5xbetterefficiencythanactive)

Application: Audio Streaming

~"

900"

Q"

Bit"to"IQ"m

apping"

+"

RF"sp

li5er/com

bine

r"

RF"out"

…"

I"

Tx"mode"

Data"bits" On/Off"

Passive

Active

Goal:Demonstratelow-poweryethighqualityaudiostreamingusingapolymorphicradio

Application: Audio Streaming

0.1

1

10

100 Passive

Polymorphic(6xbetterefficiencythanactive)

Duty-cycledActive

Bad

Poor Fair

Good

Excellent

MeanOpinionScore(MOS)

EnergyEfficien

cy(b

its/nJ)

Application: Video Streaming

Goal:Demonstratetradeoffbetweensensingcostandcommunicationcostusingapolymorphicradio


+

Sub-sample

Goal:Demonstratetradeoffbetweensensingcostandcommunicationcostusingapolymorphicradio

Gaze


~"

900"

Q"

Bit"to"IQ"m

apping"

+"

RF"sp

li5er/com

bine

r"

RF"out"

…"

I"

Tx"mode"

Data"bits" On/Off"

Passive

Densesampling

Active

Sparsesampling

+

Passiveradiohaslowcost,hencemoreenergyisavailableforsampling,andvice-versaforactiveradio


Acgve

Backscaher

Polymorphic

PupilTrackingError(pixels)

0 5 10 15 20 25 30

~"

900"

Q"

Bit"to"IQ"m

apping"

+"

RF"sp

li5er/com

bine

r"

RF"out"

…"

I"

Tx"mode"

Data"bits" On/Off"

Passive

Densesampling

Active

Sparsesampling

+

Conclusions

Combiningactiveandpassivearchitecturesallowsustodesignlow-powerstreamingradios.

Reliability

Power

Late

ncy

Backscatter radio

+

Active radio

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