braidio: an integrated active-passive radio for mobile ...panhu.me/pdf/old/sigcomm2016.pdf ·...
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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
CICS@UMass Amherst 4
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
CICS@UMass Amherst 5
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
CICS@UMass Amherst 6
Diversity of radio architectures
WiFi/ Bluetooth
Backscatter: Low power transmitter
Passive: Low power
receiver
RFID Tag AM receiver
Active: Symmetric
Radio
CICS@UMass Amherst 7
Diversity of radio architectures
WiFi/ Bluetooth
Backscatter: Low power transmitter
Passive: Low power
receiver
RFID Tag AM receiver
Active: Symmetric
Radio
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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
CICS@UMass Amherst 9
Diversity of radio architectures
WiFi/ Bluetooth
Backscatter: Low power transmitter
Passive: Low power
receiver
RFID Tag AM receiver
Active: Symmetric
Radio
CICS@UMass Amherst 10
Backscatter reader architecture
Backscatter transmitter
Antenna
Baseband
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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
CICS@UMass Amherst 12
Diversity of radio architectures
WiFi/ Bluetooth
Backscatter: Low power transmitter
Passive: Low power
receiver
RFID Tag AM receiver
Active: Symmetric
Radio
CICS@UMass Amherst 13
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
CICS@UMass Amherst 14
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
CICS@UMass Amherst 17
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
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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
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Bradio Backscatter RX: Design Tradeoffs
Passive receiver with SAW filter
Antenna diversity
Reduced sensitivity
Reduced robustness
Reduced range
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Active radio as a safety net
What if the Braidio backscatter mode fails?
Active radio as safety net
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Challenge #2: different working ranges
Distance
Available-links
Active link
Passive link
Backscatterlink
RegimeA
RegimeB
RegimeC
TX Power
RX
pow
er
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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.
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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
CICS@UMass Amherst 24
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
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Braidio: Operating distance
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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
CICS@UMass Amherst 27
Conclusion
ActiveBackscatterPassive
Braidio: A novel power-proportional radio that can deal with asymmetric energy budgets on mobile devices.
Thank you
CICS@UMass Amherst 28
Conclusion
ActiveBackscatterPassive
Braidio: A novel power-proportional radio that can deal with asymmetric energy budgets on mobile devices.
Thank you
CICS@UMass Amherst 29
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
CICS@UMass Amherst 30
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