WE2F-01
SMillimeterwave Imaging Sensor Nets: A Scalable 60-GHz Wireless Sensor
Network
Munkyo Seo*, B. Ananthasubramaniam, M. Rodwell and U. Madhow
El t i l d C t E i iElectrical and Computer EngineeringUniversity of California, Santa Barbara
CA 93106 USA
1
CA 93106, USA
Outline
• Motivation(1) A scalable, simplistic approach to the wireless sensor network(2) Exploit millimeter-wave frequencies
• Proposed Approach
• Collector System
• 60-GHz Passive sensors60 GHz Passive sensors
• Indoor Radio Experiment
2
Wireless Sensor Networks (WSN)
• Goal: Distributed data collection & localization to obtain an information map D[x y z t]obtain an information map, D[x,y,z,t]
• Many scientific, industrial and military applicationsEnvironmental monitoring– Environmental monitoring,
– Wildlife research,– Seismic activity detection,Seismic activity detection,– remote sensing, – battle field surveillance, – border policing, – planetary exploration,
Body area network
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– Body-area network,– …
Current WSN Practice• Data collection: Multi-hop based communication
– Low-power communication ☺– Not very suitable for large-scale networks
• Localization: Fixed ID code, GPS, acoustics, etc– Tends to make sensors costly, complex
4From Akyildiz et al, IEEE Comm. Mag., Aug. 2002
Simplistic Sensor ApproachSensor with minimal functionalityMove all complexity to the collector
DATAdeltaf
sensor(1) Collector sweeps a beam(2) Sensors receive, modulate and transmit it back.(3) C ll t j i tl d t t d t & l ti sensor(3) Collector jointly detects data & location
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Simplistic Approach• Similarities with optical imaging & radar
• ScalabilityScalability– Communication grows linearly as # of sensors
• Built-in Localization• Built-in Localization– Range resolution by a wideband range-code– Angular resolution by a narrow beam– Angular resolution by a narrow beam
• Simplistic sensors (= low-cost, low-power)No communication among sensors– No communication among sensors
– No localization capability required.• Concerns
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• Concerns– Need line-of-sight, complex collector signal processing
Exploit Millimeter-waves
NarrowBeamwidthWide Bandwidth
• Motivations:Higher angular resolution @ same antenna aperture
ooHPBWHPBW
eADφθλ
π 000,414 2 ==
– Higher angular resolution @ same antenna aperture– Higher range resolution @ same fractional BW– High data rate
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– High data rate– Unlicensed band @60GHz (BW>5GHz)
Signal Processing Principle
• Localization– Goal: Find the most likely sensor locationGoal: Find the most likely sensor location.– How? 3-D matched filtering (M/F)
(1) Range correlation (Tx Range code)( ) g ( g )(2) Azimuth correlation (w/ AGF)(3) Elevation correlation (w/ AGF)(4) Fi d k!
Maximum-likelihooddetection
(4) Find a peak!Accuracy eventually limited by the received SNR
• Data Demodulation– Goal: Retrieve the local sensing data (1? 0?)
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Goal: Retrieve the local sensing data (1? 0?)– How? Track the peak
Round-trip Radio Link
6~16dB/km @ 60-GHz band
( )2
22 eGDDDP R
dRXTXr λλ
α−
= ( )( )44 R
GDDDP downupsenssensRXTX
t πλλ
60-GHz
P D D D G 610BER@10kbps −=R
60-GHz +/- fdelta
7dBm 23dBi 40dBi 7dBi -3dB 25m (current prototype)25dBm 40dBi 40dBi 7dBi -3dB 200m (possible ext.)
tP TXD RXD sensD sensG max 10BER@10kbps, =R
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25dBm 40dBi 40dBi 7dBi 3dB 200m (possible ext.) 25dBm 40dBi 40dBi 7dBi 80dB 1,600m (“active” sensor)
60-GHz Collector Block Diagram
Range code: 20-MHz PRBS (26-1) Single-chip= 7.5m,
Directivity= 40dB (2 deg)0.4m@R=10m
Steerable(azimuth, elevation)
g p ,Max. field size= 470m 4.0m@R=100m
WaveformSynthesizer x3 BPF
TX RF
Tx ANT
TX IF
PRBS(R=20MHz) D=23dBi
P=7dBm
20.166 GHz
TX-RF60.5 GHz
Rx ANT
S/GTX-IF
20.166 GHzP 7dBm
BPFDown-conv.
I/QDemod.
RX-RFRX-IF1RX-IF2
Oscilloscope
USB port
D=40dBi
10
60.5 GHz +50MHz4.25GHzRX IF2
900MHz
S/G900MHz
S/G18.766 GHz
Computer
USB port
60-GHz Collector Transceiver
Rx Antenna (40dB)
Tx Antenna (23dB)
Remote controlledRemote-controlledPositioner (Az, El)
Transceiver board
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60-GHz Collector System
• Transceiver with all required instrumentsrequired instruments.
• Mounted on a mobile tcart.
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Measured Antenna Gain Function (AGF)
AGF = (TX ANT) (RX ANT)AGF (TX ANT) (RX ANT)= (23dB Horn) (40dB Cassegrain)
ude 1
Mag
nitu
0.5
M
-4 -3 -2 -1 0 1 2 3 40
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Azimuth, Elevation (degree)
60-GHz Passive Sensor: Block Diagram
• Receive, modulate and re-radiate the beam
• Simplicity, low cost, robustness, etc
Baseband BPSK Modulator Open-slot Antenna
XTAL MS-to-SL¼ λfdelta= 50MHz
PIN di d (MA COM)
16-bitLocal
transition
¼ λ
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PIN diode (MA-COM)data¼
60-GHz Passive Sensor: Considerations• Antenna
– Patch type? – Slot-type? – Open-slot type?
S b t t RO4003C• Substrate: RO4003C– 0.2mm, Er=3.38
Loss= 0 07dB/mm Q=20– Loss= 0.07dB/mm, Q=20• Standard low-cost PC-board
manufacturingmanufacturing– Min. line width/spacing =
5mil (125um)PIN diode(flip-chip)
15Size: 15mm x 10mm
– This favors high Z0 (=90ohm)
(flip chip)
Modulator Impedanceab
60GHz65GHz ( )
i did tmodmod aVb Γ=
Bias ON(7mA) wavereflected:b
aveindident w:a
55GHz55GHz
60GHBias OFF
• Switches between two impedance states.
60GHz
65GHz
Bias OFF• ~180 degree relative
phase shift
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• BPSK Modulation
Linearly-Tapered Open-Slot Antenna
Beam Pattern (7dBi)
HFSS
Beam Pattern (7dBi)
0dB-10dB
0Input Match
`
S(1
,1)) 0
-1020
dB(S
50 55 60 65 70
-20-30
17HPBW= 50 deg Freq (GHz)
50 55 60 65 70
CMOS Passive Sensor (under fab.)
For low-power operation, CMOS integration i
L t (1 2)
is necessary
• 3-channel sensor (90-nm CMOS)
• dc power = 0 5~3uW
Layout (1mm2)
• dc power = 0.5~3uW
• Contains a BPSK modulator and l lt t ll dlow-power, voltage-controlled ring-oscillator
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• Flip-chip interface to ANT.
Indoor Radio Experiment
sensor
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Received Power vs Range
Measured
dBm
)
MeasuredCalculated
41 R100-90-80
ower
(d
120-110-100
ved
Po
100
-120
101
Range (m)Rec
eiv
20
Range (m)
Received Spectrum (RX-IF2)
0 0
Sensor OFF Sensor ON (~3m)
m)
-30
-20
-10
-30
-20-10
r (dB
m
-40
-30
-50
-40
-30
-50Pow
er
0.90 0.95 1.000.85 1.05 0.90 0.95 1.000.85 1.05
Freq. (GHz) Freq. (GHz)
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q ( ) q ( )
2-D Localization (M/F output)
Sweep 15.6 degStep= 0.6 deg
th
Single sensor
collectorradial
azim
utradial
Two sensors
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collectorField size: 12x0.6 m2
3-D Localization (M/F output)1.5 deg
0 5 deg
1.0 deg
0 deg
0.5 deg
El ti 0 deg
-0.5 deg
Elevation
-1.0 deg
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-1.5 deg
Data Demodulation
0
0.05
Reference PRBS-0.05
0
0.2
Reference PRBS
Received signal (I)-0.2
0
4
Received signal (I)
02Cross-correlation
1111 0001 001 0 111 00
-0.20
0.2Demodulated Data(10kbps)
1111 0001 001 0 111 00
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(10kbps)
Summary
• Millimeter-wave wireless sensor networkLarge scale network w/ simplistic sensors– Large-scale network w/ simplistic sensors
• 60-GHz prototypeCollector– Collector
– PIN-diode based passive sensor– CMOS sensor (dc power: uW level)( p )
• Indoor radio experiment (<12m)– Data demodulation, 3D localization
• Next– uW CMOS sensor module
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– Large-scale radio experiment
Thank you.
Questions?
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