Mobile and Vehicular Network Lab
Vehicular
Visible Light Communications
Hsin-Mu (Michael) Tsai (蔡欣穆)
Computer Science and Information Engineering National Taiwan University
2014 APEC Cooperative Forum on Internet of Vehicles
2014/5/20
Mobile and Vehicular Network Lab
http://www.forcegt.com/wp-‐content/uploads/2012/09/volvo_road_train-‐11.jpg 2
IoV: Cooperation between Vehicles
Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved. 2
Mobile and Vehicular Network Lab
Building Roads: No Moore’s Law Here
Wugu-Yangmei Overpass (completed in 2013) (for Freeway No. 1 in Taiwan)"
– Cost: 3B USD for 40 km of elevated road
- The most expensive (per unit length) in the history"
– Divert approximately 25% of traffic from the original highway"
– Improve rush hour average speed:
- 40-50 kmph à 80-90 kmph"
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Hsin-Mu Tsai (c) 2010-2014 All rights reserved.
Mobile and Vehicular Network Lab
Increase Road and Energy Efficiency
• At 100 km/h, the road surface utilization = 5%!
• Reduce the gap - Longitudinal control
" " " " "(adaptive cruise control) !
• Reduce lane width - Automatic steering"
• Reduce aerodynamic drag - Close-formation
automated platoons can save 10% to 20% of total energy use"
• Only possible through cooperation with communications!
– Drivers’ response delays cause stop and go disturbances"
45.5 m
5 m
3. 5 m 1.8 m
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Hsin-Mu Tsai (c) 2010-2014 All rights reserved.
Mobile and Vehicular Network Lab
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Challenges: V2V Communications
http://img.autonet.com.tw/news/img/2012/8/bb20802621.jpg Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved. 5
Mobile and Vehicular Network Lab
Challenge 1: Density and Speed
• Range à reaction time"
• 200 km/h relative speed
100 m = 1.8 s @ 200 km/h"
• A 100-m road segment can have:"
– More than 600 scooters"
– More than 120 cars"
• Heavy Interference"
• The need for
reliable communications"
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Hsin-Mu Tsai (c) 2010-2014 All rights reserved.
Mobile and Vehicular Network Lab
Challenge 2:
My loca(on is (X3, Y3) and my speed is 98 mph, and I am braking.
My loca(on is (X2, Y2) and my speed is 101 mph.
My loca(on is (X1, Y1) and my speed is 106 mph.
GPS Uncertainty = 5 -‐10 m
Who is Speaking?
Is the car in front of me braking?
Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved. 7
Mobile and Vehicular Network Lab
Challenge 3: Cost and Benefit
• DSRC (IEEE 802.11p) – the current dominant standard for vehicular communications"
• NOT in vehicle products today"
• Low adoption incentive:
where is the (day 1) benefit?!
– Minimum market penetration rate: 10%
(All new cars have it à have to wait for 2 years)"
• Low adoption incentive: high initial cost!
– Complexity similar to a WiFi radio"
– But with much lower quantity,
when bootstrapping the market"
Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved. 8Mobile and Vehicular Network Lab
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Vehicular
Visible Light Communications
EE Times: Top 10 Automotive Agendas for 2014 & Beyond 7. Time to act on V2V,V2I
Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved. 9
Mobile and Vehicular Network Lab
Vehicular Visible Light Communications
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1 0
1010
1 0 1 0
Time
Receiver Transmitter
Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved.
Mobile and Vehicular Network Lab
Keep the Light’s Original Function
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Human eyes can’t perceive LED’s high frequency flickering (persistence of vision)
Light
1 0 1 0
Time
Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved.
Mobile and Vehicular Network Lab
Receiver Options
Data Rate Number
of pixels Cost
Photodiode
module Up to
several Mb/s 1 Extra
Camera
sensor A few Bytes/s Millions Use
existing cameras
Photodiode module Camera Sensor
Transmitter LED Lights
Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved. 12
Mobile and Vehicular Network Lab
Video: http://goo.gl/lo1f9 13
V2LC for Scooter Safety
S.-‐H. You, S.-‐H. Chang, H.-‐M. Lin, H.-‐M. Tsai, "Demo: Visible Light
Communications for Scooter Safety,“ ACM MobiSys, Taipei, Taiwan, June 2013 Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved. 13
Mobile and Vehicular Network Lab
Your Car
Automatic Interference Filtering
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• Visible light cannot penetrate obstacles = line-of-sight only"
• VLC communication coverage = immediate neighbors only"
"à only those that could immediately collide with you!
• Comparison: RF coverage includes a lot more irrelevant vehicles à additional interference à less reliable
RF Coverage
VLC Coverage
Automatic interference filtering with VLC à Zero delay + zero overhead
à
Always scalable to density & speed*!
*S.-‐H. You, O. Shih, N. Wisitpongphan, H.-‐M. Tsai, and R. D. Roberts, “Smart Automotive Lighting for Vehicle
Safety,” IEEE Communications, vol.51, no.12, pp. 50-‐59, December 2013. Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved.
Challenge 1
Mobile and Vehicular Network Lab
Highly Directional Transmission
Easily regulated output radiation pattern
àHighly directional transmission with minimal leakage"
x location (m)
y location (m)
0 2 4 6 8 10
0 1 2 3 4 5 6
-120 -100 -80
Scooter Tail Light -60
Radiation Pattern
Tà
Safety regulation specifies the minimum light intensity (at 30.48 m) within 20 degrees of irradiance angle.
W. Viriyasitavat, S.-‐H. Yu, and H.-‐M. Tsai, “Short Paper: Channel Model for Visible Light Communications using Off-‐the-‐shelf Scooter Taillight,” in Proc. IEEE Vehicular Networking
Conference, pp. 170-‐173, Boston, United States, December 2013. Hsin-Mu Tsai (c) 2010-2014 All rights reserved. 15
Challenge 1
Mobile and Vehicular Network Lab
Simultaneous Transmissions
• Lights occupy disjoint sets of pixels
" " "(except when very far away: > 1km)"
• Simultaneous transmissions
"with no collision, interference, and access delay"
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Hsin-Mu Tsai (c) 2010-2014 All rights reserved.
Challenge 1
Mobile and Vehicular Network Lab
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Talking Pixels
• Computer vision:
associate pixels with information (distance) and context"
• V2LC: direct association -
Information directly comes from the pixels!"
• Photogrammetry: sub-meter accuracy for positioning"
www.ionroad.com
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Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved.
Challenge 2
Mobile and Vehicular Network Lab
• Low Cost: LED lights already used extensively for vehicles"
• Extremely simple driver circuit: USD$2 microcontroller"
• Aftermarket product is feasible:
" "driver module and/or light module"
Low-Cost Transmitter:
Pervasive Existence of Automotive LED lights
Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved. 18
Challenge 3
Mobile and Vehicular Network Lab
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Luxgen’s Eagle View+
360 degree vision coverage
• Low cost: cameras already exist in many cars"
• Aftermarket product is feasible: "
• App download for mobile devices"
• WiFi/Bluetooth link to light module"
" 19
Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved.
Challenge 3
Low-Cost Receiver:
Cameras Everywhere
Mobile and Vehicular Network Lab
Conclusion
• IoV creates new opportunities for both new
applications and huge performance improvements
• New challenges need to be addressed:
– Vehicle density and speed
– Association of information and identity – Market penetration
• V2LC: new solution for vehicular communications
– Reliable “point-‐to-‐point” V2V communications – Direct association of information and pixels
– Low-‐cost system design with aftermarket product options
Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved. 20
Mobile and Vehicular Network Lab
Thank you!
Please feel free to contact me for questions:
Prof. Hsin-‐Mu (Michael) Tsai (蔡欣穆)
hsinmu@csie.ntu.edu.tw
http://www.csie.ntu.edu.tw/~hsinmu/
Computer Science and Information Engineering National Taiwan University
Hsin-‐Mu Tsai (c) 2010-‐2014 All rights reserved. 21