CoCoon

1. CoCoon
A Conductive Substrate-based
Coupled Oscillator Network for
Wireless Communication
Xingda Chen
MOSAIC Lab, UMass Amherst

2. IoT deployment is expensive in large
sensing environments
0%
10%
20%
30%
40%
Survey: what hinders
IoT Deployment?
Problem

3. Can we leverage conductive substrates
(paint, tape, wallpaper, ink…)
Existing work focuses on user interaction and sensing (eg:
touch inputs)
Lilypad, Leah et al. Living Wall, Buechley et al. BARE Conductive
Problem

4. How can we design novel IoT systems that leverages
ubiquitous conductive substrates?
Our work use the substrate to optimize
wireless system performance
Sync
Signal Process
Reflect
Beamform
• Synchronization
• Beamforming
• Reflection
• Unconventional signal
processing
• ….
Substrate
Idea

5. • Multi-static RFID
• OFDM for IoT communication
• Distributed beamforming
• Radio Interferometry
…
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$100
$200
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Price
Accuracy (parts per million)
TXCO
OXCO
Carrier synchronization is required in many
wireless networks, but there is always a trade off
VXCO
Price
Accuracy
Overhead
The more accurate
oscillators are expensive
Challenge

6. CoCoon in a nutshell: one high precision oscillator +
multiple low precision(cheap) oscillators
Idea
0 ppm
Substrate
…... Cheap OSCs
High precision OSC
Price Accuracy Overhead

7. Carrier synchronization using frequency locking
System overview of CoCoon
1: Freq Pulled
2: Ref Control
3: Quasi-Lock
Achieved carrier
synchronization through:
1. Frequency pulling at the
reference oscillator
2. Micro adjustment of PLL
frequency output through
reference source
3. Quasi-Lock to reduce the
power of the system

8. Carrier synchronization using frequency
locking
Reactive components in an
oscillator auto-adjust when it
experience a phase difference
injected from outside (Adler,
Kuramoto, Razavi…)
• High power pulls
low power
• The lower the Q, the
larger the pulled
range
• Coupled with high Q
High Q source pulls low Q ceramic resonator
High Power
Low Power

9. PLL frequency output controlled by reference input
PLL RF output increases as black dotted reference input
• Exists a small frequency
perturbation of PLL output
due to reference input
• Correct RF output depends
on correct reference input
• RF output can be
controlled by reference
input– approximately
linear

10. 7X+ power saving using quasi-lock instead of fully-lock
• Quasi lock
produce a super
slow beat and can
be treated as
frequency locked
• Significantly less
power required
to maintain quasi
lock than fully
locked
Razavi
Power consumption comparison
Power to pull 3 oscillators:

11. CoCoon stays intact against CFO in BPSK
One of the comm benefit we
shown:
CoCoon can offset CFO by
adjusting the high precision
OSC
Substrate
High precision OSC
Tx Rx
CFO
…... Cheap OSCs

12. Use conductive substrate to distribute RFID
readers
• Distributed
RFID
• Spatial
Diversity
• Blind
Beamforming

13. Large Warehouses/hospitals appreciate a
better WSN system assisted by substrates
Environment centric wireless system
integrates existing technology, and make it
work even more efficiently
• Distributed RFID
• Better Bluetooth
Frequency hopping
• Synchronized Acoustic
Sampling
• ….