September-November 2015 Intel Project Quarterly Report
Next-Generation Cooperative Vehicle Safety System
Current team members:
Champion: Dr. Richard Roberts
PI and co-PI: Prof. Hsin-Mu (Michael) Tsai and Dr. Kate Ching-Ju Lin
Students: Hsin-I Wu (full-time RA , Hua-Yen Tseng (Master, graduating in December), ChungLin Chan (Master), Jing-Yeu Chen (Master), Ai-Ling Chen (Master), You-Lin Wei (Master)
Communication with the champion:

Rick was on sabbatical until mid-September.

Javier Perez-Ramirez is a new team member at Intel Labs, who will start to get
involved with our project as well. He is a new Ph.D. graduate from New Mexico
State University, and wrote a thesis involving camera communications.

Michael and Rick exchanged quite a few emails after the F2F. Michael reported that
the presentation and the demo went well at the F2F. The two also set up the plan
to prepare for the submission to IEEE 802.15.7r1’s call for proposal and the
presentation that will take place in January’16 IEEE 802 meeting. The intent for
proposal form was submitted to the 802.15.7r1 committee in November 1st. Rick
suggested that the proposals from NTU & Intel can be merged, followed by a
possible merge with Panasonics’, if they show interests. However, so far there is no
response from them.
External activities:
1. Ford North America kicked off an international research project with our team since
October (please see the news from the center website). The goal of the project is to utilize
the V2V VLC technology to eliminate the traffic shockwave on the road, and thus reduce the
chance of a traffic congestion to happen. This is a direct application of the VLC technology
developed in the center.
2. Michael gave a talk on the use of VLC in vehicular applications at Lextar Electronics, a LED
chip, package, and system manufacturer in Hsinchu, and the third largest LED company in
Taiwan. The audience also includes representatives from other companies. This is our first
time to promote VLC to a LED manufacturer.
3. We have completed the contract signing for technology transfer to ITRI in October. The item
of interest is the TX/RX implementation of our RollingLight CamCom system (the
technology itself remains open-IP). We have also completed more than 10 hours of lectures
for ITRI engineers to learn how to use our technology.
Progress:
1. LiBeamScanner Optimization
In the last few months, we fixed the arbitrary rotation problem of LiBeamScanner and
have it demo on 2015 VLCS workshop. However, there are still some problems in this
systems which need to be addressed, listed below:
 Methods needed to assume the knowledge of the receiver’s height
 Receiver is a bit too big and hard to be deployed in wearables
In the past two months, we had investigated ways to estimate RX height, i.e., the
projecting distance, directly from the system. Possible ways include time difference of
arrival (TDOA) and angle of arrival (AoA) positioning.
In the former, TX transmits light signals at a frequency of 40 MHz or larger, which has a
wavelength of 7.5 m or less. Rx can estimate its own location, includingheight, through
observing the phase difference of the signal received from multiple light sources installed
in different spatial location. The latter method uses angle-of-arrival positioning and
triangulation. As the figure below shows, if a receiver can obtain signals from 2
transmitters respectively, knowing the angle-of-arrival of both signals allow height
estimation. We plan to take the latter approach but hope to still put everything in a single
TX component (i.e., light bulb). Prototype efforts have begun since early November.
In addition, we tried to improve the performance of LiBeamScanner by using a better TX
LCD. Because the rising/falling time of the Tx LCD contributes to a large portion of the runtime of LiBeamScanner, it will be more effective if we could reduce the rising/falling time.
So far the rising/falling time of the TX LCD in our prototype, NHD-C12864GG-RN-GBW (a TN
B&W LCD), has an average of 220 ms. Although LiBeamScanner exploits PPM to modulate
data, we can only practically reduce the “symbol duration” to 40ms.
5 alternative small LCD screens are selected for rising/falling time testing , using the
following 3 steps:
1. Code a black/white blink program.
2. Upload to the LCD screen.
3. Use an oscilloscope to measure rising/falling time.
Here is the result table.
It shows that some LCDs can have a rising/falling time an order of magnitude smaller, at
tens of milliseconds. We plan to incorporate this in the second version of the TX prototype.
One downside of using these LCDs is that they have lower transparency and thus a larger
portion of the LED light will be blocked.
2. Simulation--- Characterizing link asymmetry in V2V VLC
In the last few months, we carried out real-world experiments to collect car mobility
traces by LIDAR. We mounted LIDAR in front of one of our test car to perform scanning,
collecting the contour of the neighboring vehicles over time as we drive the car in
different scenarios. This is mainly to obtain mobility traces with high accuracy to
estimate the received power over V2V VLC links, as slight lateral movements would
create large difference in received power. The figure below shows an obtained LIDAR
frame. We developed simple detection and tracking algorithm to extract neighboring
cars’ 2-D location and bearing over time from the LIDAR traces.
After obtaining the trace, we further combined the radiation data previously measured
headlamp and taillight radiation pattern with the LIDAR traces, in order to estimate the
receive power over V2V VLC links according to the coordinates and the bearing of our
test car and the neighboring car.
Given the relative position (x,y) of a neighboring car (with our car at the origin), we do
first do bilinear interpolation of received radiation pattern data to estimate the received
power at that location, assuming that the difference in bearing of the two cars are 0.
This is usually not the case, and thus we need to perform an additional step to adjust
cos(𝜃)
the received power, given by Pr,(≠) = 𝑃𝑟,(=) × cos(𝜙) , where Pr,(≠) and Pr,(=) are the
received power assuming that the bearing difference is zero and not zero, respectively,
and θ and 𝜙 are incidence angle and the irradiance angle, respectively.
One of our obtained results is shown above. The take-home message is that the
majority of V2LC links are asymmetric, i.e., the received power of the incoming direction
and the outgoing direction are significantly different. 50% of the cases have a difference
smaller than -42 dB and 80% of the cases have a difference smaller than -22 dB. Additional
considerations at the PHY or MAC layer are required to address this issue.
This work has been summarized in a paper, which is accepted by IEEE Vehicular
Networking Conference 2016 and will be presented in December’16.