| Electronics > Projects, Designs, and Technical Stuff |
| Brainstorming about bachelor thesis project - Data transmission using car lights |
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| StillTrying:
--- Quote from: 97hilfel on October 23, 2019, 09:05:54 pm ---about the viability of a data channel for cars using their lights. --- End quote --- That's easy, it's not viable. :) |
| tunk:
I have no experience with this, but I would guess when you're going to use a camera (30fps?) and 10bps that the only way is to vary the taillight intensity. If you could make the variation small enough (maybe less than 5%) then it may appear invisible. |
| LaserSteve:
Sync the camera to the trailing edge of tbe gps second epoch. Then use Gold and Barker codes as the sync preamble as the leds will be synced as well. . Basically spread spectrum modulation. Use multiple leds or red and amber or IR for the in phase and quadrature. 5G phones can also supply an inherent clock as can the carrier of AM radio stations. Use the VIN as the sysID. Now award me my patent and my BSEE. Job Jobbed. PS you'll need dichroic filters in front of the camera to reject the jamming from street lamps and led signs. Good luck with this one. Will work fine in the lab... Not so well on the road. Exercise in why is left for the astute reader with a Thorlabs DET-10A and a cheap digital scope in the passenger seat. Then worry about hacking and jamming and older cars on the road. There is a tiny segment of the 5 Ghz band allocated world wide for car to car. Steve |
| TheUnnamedNewbie:
Ignoring the people who claim it is infeasible on practical reasons (While I agree it seems unlikely to be effective, part of research is looking at this regardless, because sometimes stuff pops up that turns out to be great after all): Figure out if you have to do it in daylight or not. If so, you will have to look at SNR constraints, but it could still be doable - esp if you look at something 'spread spectrum' or rather high-redundancy. An alternative approach to deal with low framrate issues: Is there any posibility you can look at driving the individual LEDs on a string of LEDs that make the tail light separately? You could try doing things like having low baudrate (so your camera can keep up) but high symbol depth information - if every LED can be tracked/modulated separately you could potentially encode a lot of information in one symbol. In a way, the properties of optical makes it so your lens acts like a extremely high gain antenna and you can look at it as a MIMO channel. Sure, you are limited to low symbol rates by the frame rate, but you will have much less issues with isolating one signal from another because you have such extreme directivity. I think (but this is just me thinking out loud) that if you do this spatial modulation, people will notice it far less, since you still have an overall constant brightness (esp if you select the symbols in such a way that every symbol has a same average power). Good luck with your bachelors thesis, sounds like an interesting project. |
| Someone:
--- Quote from: TheUnnamedNewbie on October 25, 2019, 08:36:10 am ---I think (but this is just me thinking out loud) that if you do this spatial modulation, people will notice it far less, since you still have an overall constant brightness (esp if you select the symbols in such a way that every symbol has a same average power). --- End quote --- The constraint of a camera (unless its running at something beyond 200Hz, which just doesn't work in automotive space/cost limits) assures it will be noticeable to a human observer. |
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