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

3

– 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

5

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

6

• 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

7

– 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?)

8

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

9

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.

12

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

13

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

14

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

16

• 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

18

• Flip-chip interface to ANT.

Indoor Radio Experiment

sensor

19

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)

21

q ( ) q ( )

2-D Localization (M/F output)

Sweep 15.6 degStep= 0.6 deg

th

Single sensor

collectorradial

azim

utradial

Two sensors

22

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

23

-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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