UltraWideband communication technology for sensor network applications

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Ultra-Wideband communication technology for
sensor network applications

• Julien Ryckaert
• IMEC

Julien.Ryckaert_at_imec.be
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The vision of Ambient Intelligence
An environment where technology is embedded,
hidden in the background
Fred Boekhorst Philips Research, ISSCC 02
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Health Care of the Future
Fitness for you!
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Increase Productivity
Home of the Future
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This vision requires the massive deployment of
sensor nodes
Network
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A sensor node is a completely autonomous device
Energy
clock
Sensing
Processing
Communication
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Three major challenges in the communication module

• Ultra-low power gt2 years autonomy
• Ultra-small size non-invasive
• Ultra-low cost disposable

• Low communication performance lt100kbps

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POWER CONSUMPTION
?
PERFORMANCE
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In reality, the total Energy consumption must be
minimized
What does it cost to transfer a bit of
information?
Power consumption (Energy/time)
Energy/bit
Data rate (bits/time)
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How does it look like today?
Increasing data rate
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POWER CONSUMPTION
UWB
?
PERFORMANCE
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Traditional Communication systems use continuous
waves
NarrowBand Communication
time
frequency
Each user/application has its own spectrum band
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Impulse Radio UWB uses short pulses
Pulse-based Ultra WideBand communication
frequency
time
Emitted power must be low enough to avoid jamming
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Activate the radio only when needed
Power
Active
Active
Sleep
The active time of the radio is reduced Radio
duty-cycling
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FCC UWB communication must be done in the
3.1-10GHz band
-41dBm/MHz
FCC
3.1
10.6
1
F GHz
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IEEE standard for low data-rate sensor networks
Burst
3 Active! 97 Inactive

• Activate the transmitter only when needed to
  achieve low-power

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The standard imposes some constraints on the
signals

• Pulses are BPSK modulated

1
0
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Overall transmitter architecture
CONTROL LOOP
(ISSCC 07)
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Time-domain measurement of the output signal
Same energy efficiency as first transmitter!
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Correlation can be done either in Analog or in
Digital domain
High Sampling rate ? Power Hungry
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Full system block diagram
Analog Output
CAL
ADC
I/O bus
Digital Controller (System Configuration and
Interfacing)
LO
Timing circuit
LNA
RFin
Serial/Par Out
ADC
CAL
DL
DL
DL
DL
Clk/Rst
(ISSCC 06)
Clk
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What about power consumption?

• State-of-art narrowband solutions (Zigbee)
• TX 10mW
• RX 2mW
• UWB solutions
• TX 0.5-1mW
• RX 0.3mW

/ 10
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UWB has other advantages

• Positioning by measuring the time of arrival
• Security UWB power spectrum below the background
  noise

DL
TX
RX
TX
DT
Background noise (kT)
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Other impulse Radio implementations exist

• Example MIT (US) proposes a similar concept
• But uses a proprietary UWB communication interface

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Therefore the question should sensor networks be
standardized?

• Pros
• Interoperability (add nodes in the network)
• Market pressure decreases cost
• Cons
• Solution biased by the big ones
• Security
• Less interferences (?)
• Sandardization aspect is an old controversial
  debate for healthcare wireless systems

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Conclusions

• UWB offers today a 10x improvement on power
  consumption.
• UWB has other interesting advantages in the
  context of sensor networks security,
  positionning,
• An IEEE standard exists today (IEEE 802.15.4a),
  but its use in wireless healthcare systems is
  still a debate.