Re: [ipwave] traffic lights status displayed in the car, and the latency problem

[Chris Shen <[e-mail]>]

Hi Alex,

Thanks Alex, it is good to see this experiment.

About the latency, it seems that you use a shared cloud server for both car
and traffic light to access.
That is the traffic light updates its status to the cloud server, and the
car queries the cloud server if there is any update. There is no direct
communication between the traffic light and the car.
So how do you measure the E2E latency from car to traffic light?

Thanks!
Chris.

On Fri, Aug 30, 2019 at 5:15 PM Alexandre Petrescu <
[e-mail]> wrote:

> Hi,
>
> Has someone else filmed a demo of displaying the traffic lights status in
> the car?  (a communicated status, not a camera recognized status).
>
> We filmed recently several such trials.  We noticed a systematic problem
> with latency.  This problem lies in the difference between the color
> displayed by the traffic light bulb and the color displayed in the car.
>
> Ideally, at no time should a human perceive a difference between what the
> light bulb displays and what the laptop displays in the car.
>
> https://youtu.be/RR5hpL29-vk
>
> At point 3 second, the bulb displays green whereas the laptop displays
> red.  This undesirable situation lasts for 1 second.  It is an enormous
> time lapse.  It is sufficient for the driver to loose confidence in the
> laptop display, and it is ample time for a self-driving car to do many
> undesirable things.  A typical reason for human loosing confidence in
> laptop display is that during such lapse of time (1 second) in many places
> in Paris area one gets honked (klaxonned) if one is first in line and does
> not leave at a moment's notice; because the last in line risks having to
> wait a second cycle - everyone in line knows that and at least one will
> honk (klaxon).  It is forbidden to klaxon in city.
>
> For this video, we did our best to reduce the latency.  The communication
> path between the traffic lights controller and the car was set with 4G.
> There are two 4G links in sequence: one between the traffic lights
> controller and the VPN server in the cloud, and another between the VPN
> server and the car.  The measured end-to-end latency from laptop to traffic
> lights controller averages 100ms.  The queries to obtain the status of
> lights are sent with a frequency of approx. 20 Hertz, which is approx. each
> 50ms. (DIASER on UDP on IPv4).  The laptop is a recent thinkpad with python
> doing queries and display.  The traffic lights controller is an Aximum
> Maestro with a Motorola MC-something.
>
> We could put 802.11-OCB there, to further gain on the communication
> latency.
>
> We could try recent pre-5G chipsets.
>
> We could try the ITS-G5 SPAT-EM technology which relies on DIASER still.
>
> But we are not sure the 1s delay exposed above will get any improvement by
> any of these steps.
>
> This is why I am asking if this situation of latent display of traffic
> lights in car was witnessed elsewhere, and which paths could be explored to
> improve the latency?
>
> Alex
>
>
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-- 
Yiwen (Chris) Shen, Ph.D. Candidate

Homepage: https://chrisshen.github.io
IoT Lab: *http://iotlab.skku.edu <http://iotlab.skku.edu/>*
Sungkyunkwan University, Suwon, South Korea
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Email: [e-mail]