21 Apr 2006 IPSN / SPOTS ‘06

Towards Radar-Enabled Sensor Networks

Prabal Duttaprabal@cs.berkeley.edu

http://www.cs.berkeley.edu/~prabal

with Anish Arora and Steven Bibyk

21 Apr 2006 IPSN / SPOTS ‘06

For this Talk

Radar UWB Radar

21 Apr 2006 IPSN / SPOTS ‘06

Motivating Application – Intrusion Detection

I detecteda RadarObject

I detect a MagObject

21 Apr 2006 IPSN / SPOTS ‘06

Motivation

• Security applications that require– Personnel detection– Stealthy sensors– Low density

• The three goals of this talk– Shamelessly proselytize radar– Give you an intuitive appreciation for radar signals– Convince you to consider radar for detection applications

21 Apr 2006 IPSN / SPOTS ‘06

Lots of Sensor Options. Why Use Radar?

21 Apr 2006 IPSN / SPOTS ‘06

Simplified Theory of Operation – Doppler Sensors

• Radar transmits short (wideband) pulses with period T = 1/f

• Target with vr = v0 reflects Doppler-shifted pulse f ’

• Electronics “mix” TX and RX pulses and output

• Target radial velocity can be estimated

• Complication: Moving objects contain many surfaces

21 Apr 2006 IPSN / SPOTS ‘06

Sensor Electronics

• Dipole antenna• UWB radar sensor

– Range: 0 – 20 m– Power

• 3.4V – 6.0V @ 1mA• 5.5V 1% @ 7.5mA

– Output• LPF Doppler baseband• Bias: 1.25V (nominal)• Range: 0 – 2.5V (VPP)

– Wakeup: ~ 30 seconds!

• Mica Power Board– Input: 2.7V – 3.3V– Output: 3V – 40V– Preset: 3.6V, 5.5V

• Mica Sensor Board• Mica2 Processor Board

21 Apr 2006 IPSN / SPOTS ‘06

Antenna Considerations

• Used default dipole antenna but it has several issues– Null in radiation pattern means

a major blind spot

– Considerable energy reflected by ground

• Discone addresses– Vertical polarization

– Omni-directional

– Wideband

21 Apr 2006 IPSN / SPOTS ‘06

Enclosure Design

• Orientation issues– Gimbal mechanism

– Rotationally self-righting

– Horizontally self-righting

• Transparent body– Passes solar radiation

– Looks really cool!

• Weather Resistance– Water-tight enclosure

– O-ring seals

– Overheats in FL sun

21 Apr 2006 IPSN / SPOTS ‘06

Sensor Traces – Noise

21 Apr 2006 IPSN / SPOTS ‘06

Sensor Traces – Person Walking

21 Apr 2006 IPSN / SPOTS ‘06

Sensor Traces – Person Running

21 Apr 2006 IPSN / SPOTS ‘06

Sensor Traces – Vehicle Driving

21 Apr 2006 IPSN / SPOTS ‘06

Signal Detection – NP Detector with CFAR

21 Apr 2006 IPSN / SPOTS ‘06

Conclusions and Future Work

• We– Motivated the application of a remarkably useful sensor– Showed feasibility of integrating UWB radar with motes– Demonstrated a simple CFAR NP signal detector– Highlighted some challenges with simple SP techniques

• Current work limited to– Single (or small number of) node(s)– Simple, local detection (and classification)– UWB Doppler motion sensors

• Future work– Address false alarm rates through robust detection– Explore collaborative signal processing– Explore low-complexity classification algorithms– Incorporate UWB rangefinders

21 Apr 2006 IPSN / SPOTS ‘06

Discussion