braidio: an integrated active-passive radio for mobile ...panhu.me/pdf/old/sigcomm2016.pdf ·...

CICS@UMass Amherst

Braidio: An Integrated Active-Passive Radio for Mobile Devices with Asymmetric Energy Budgets

1

Pan Hu, Pengyu Zhang, Mohammad Rostami, Deepak Ganesan University of Massachusetts Amherst

CICS@UMass Amherst

Batte

ry C

apac

ity/W

h

0.1

1

10

100

Nike Band

Pebble Watch

Microsoft Band

Apple Watch

iPhone 6s

iPhone 6 Plus

Nexus 6P

Surface Book

MacBook Pro 13''

MacBook Pro 15''

Three orders of magnitude variation in battery capacity

2

Variability in battery capacity

CICS@UMass Amherst 3

Asymmetric battery lifetime

Devices with smaller batteries deplete far ahead of those with larger batteries

10% 90%

50mW 50mW

Sensor Data


Symmetric power consumption

Bluetooth

TX

RX

55~60mW

59~67mW

TX/RX 0.82~1.0

BLETX

RX

21~30mW

19mW

TX/RX 1.1~1.6


Can we design a power proportional radio?

Can we create a radio which consumes power proportional to battery size?

90% 90%

0.1mW 50mW

Sensor Data


Diversity of radio architectures

WiFi/ Bluetooth

Backscatter: Low power transmitter

Passive: Low power

receiver

RFID Tag AM receiver

Active: Symmetric

Radio



WiFi/ Bluetooth


Passive: Low power

receiver


Active: Symmetric

Radio


Symmetric active radio architecture

Active TX Active RX

BasebandMixer

Amplifier

Antenna

Baseband

2.4GHz Carrier

Mixer

Amplifier

Antenna

2.4GHz Carrier

Similar power consumption at TX and RX



WiFi/ Bluetooth


Passive: Low power

receiver


Active: Symmetric

Radio


Backscatter reader architecture

Backscatter transmitter

Antenna

Baseband


Backscatter reader architecture

Backscatter reader Backscatter transmitter

Baseband

2.4GHz Carrier

Mixer

Amplifier

Antenna 1

Antenna 2

Antenna

Baseband

Much less power at TX but reduced range



WiFi/ Bluetooth


Passive: Low power

receiver


Active: Symmetric

Radio


Passive receiver architecture

Active TX Passive RX

BasebandDiode

Antenna

Baseband

2.4GHz Carrier

Mixer

Amplifier

Antenna

Much less power at RX but reduced range

Capacitor Resistor


Power consumption of radios

Can we take advantage of these architectures?

Radio type TX RX TX/RXActive 20mW 20mW 1

Backscatter 20mW 0.02mW 1000:1Passive 0.02mW 20mW 1:1000

CICS@UMass Amherst

Any ratio in between 1:1000 to 1000:1

15

Architecture of radios

TX Power

RX

pow

er

TX/RX=1000:1

TX/RX=1:1000

TX/RX=1:1

Radio type TX/RX

Active 1

Backscatter 1000:1

Passive 1:1000

Achievable region

Available radio

CICS@UMass Amherst

Challenges in combining three modes

16

Backscatter RX consumes

excessive power

BLEBluetooth

Reader 1Reader 2

0 0.45 0.9Power/W

>5x gap

Distance

Available-links

Active link

Passive link

Backscatterlink

RegimeA

RegimeB

RegimeC

Different types of radios have different

working ranges


Why is a Backscatter reader power hungry?

Self-interference cancellation

Baseband

2.4GHz Carrier

Mixer

Amplifier

Antenna 1

Antenna 2

LeakageΣ-+

Est. of interference

Active IQ Receiver

In-phase

Quadrature

0

1


Reducing power of Backscatter reader

Passive receiver with SAW filter

Baseband AmplifierDiode

Antenna

Capacitor Resistor

Filter

Antenna diversity

Antenna 1 Antenna 2

path 1

1

path 2


Bradio Backscatter RX: Design Tradeoffs

Passive receiver with SAW filter

Antenna diversity

Reduced sensitivity

Reduced robustness

Reduced range


Active radio as a safety net

What if the Braidio backscatter mode fails?

Active radio as safety net


Challenge #2: different working ranges

Distance

Available-links

Active link

Passive link

Backscatterlink

RegimeA

RegimeB

RegimeC

TX Power

RX

pow

er


Challenge #2: different working ranges

Distance

Available-links

Active link

Passive link

Backscatterlink

RegimeA

RegimeB

RegimeC

TX Power

RX

pow

er Backscatter: 70% Passive: 30%

Braidio multiplexes across modes based on SNR of each link and battery levels to achieve desired power ratio.


Implementation of Braidio

Top Layer Bottom Layer

UFL Connector+ RF Cable

Receive Ant + SAW filter

Ant.Switch

PassiveReceiver

CarrierEmitter TX Ant

ActiveRadio

MicroDcontroller

Amp +Comparator

47mm/1.85in

47mm/1.85in


Braidio: Achievable power ratios

104 106 108 1010 1012104

106

108

1010

1012

A

B

C

1:2546

0.9524:1 3546:1

A: ActiveB: Passive@1MC: Backscatter@1M

TX bits per joule

RX

bits

per

joul

e


Braidio: Operating distance


Braidio: Performance gain over active radio

1.43

2.57

3.68

6.97

25.9

41.0

51.6

263

290

368

2.45

1.43

1.85

3.12

10.4

16.3

20.4

102

113

143

3.51

1.76

1.43

2.21

6.83

10.5

13.0

64.7

71.3

90.1

6.63

2.97

2.11

1.43

3.62

5.37

6.60

31.3

34.4

43.4

24.7

9.98

6.51

3.45

1.43

1.85

2.16

8.29

9.07

11.3

39.1

15.5

10.0

5.12

1.77

1.43

1.61

5.44

5.94

7.34

49.1

19.4

12.4

6.29

2.05

1.54

1.43

4.46

4.85

5.96

251

97.7

61.6

29.8

7.89

5.19

4.24

1.43

1.50

1.71

276

107

67.9

32.8

8.64

5.65

4.61

1.43

1.43

1.62

350

136

85.8

41.4

10.7

6.99

5.68

1.63

1.54

1.43

Nike Fuel Band

Pebble Watch

Apple Watch

Pivothead

iPhone 6S

iPhone 6 Plus

Nexus 6P

Surface Book

MacBook Pro 13

MacBook Pro 15

Nike Fuel Band

Pebble Watch

Apple Watch

Pivothead

iPhone 6S

iPhone 6 Plus

Nexus 6P

Surface Book

MacBook Pro 13

MacBook Pro 15

300x improvement when fitness band transmits to laptop

Transmitter

Rece

iver


Conclusion

ActiveBackscatterPassive

Braidio: A novel power-proportional radio that can deal with asymmetric energy budgets on mobile devices.

Thank you


Backup

104 106 108 1010 1012

TX bits per joule

104

106

108

1010

1012R

X bi

ts p

er jo

ule

A

BC

D

E

F

G

1:25461:4000

1:5600

0.9524:1 3546:1

5571:1

7800:1

A: ActiveB: Passive@1MC: Passive@100kD: Passive@10kE: Backscatter@1MF: Backscatter@100kG: Backscatter@10k


Backup

1 2 3 4 5 6Distance/m

100

101

102

Perfo

rman

ce g

ain

(TX/

RX)

iPhone 6s to Apple WatchApple Watch to iPhone 6sSurfaceBook to Nexus 6PNexus 6P to SurfaceBookiPhone 6s to Fuel BandFuel Band to iPhone 6s

braidio: an integrated active-passive radio for mobile ...panhu.me/pdf/old/sigcomm2016.pdf ·...

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