21–30 of 41 posts
Have you tried the Google Nearby library? Do you think that sound modems still have a place now that Bluetooth LE is more of an option?
edit: Also, do you have a browser version I can try?
Awesome library! I feel like sound modems don’t get enough attention and carry some “old-tech” stigma from the dialup days, even though they’re fairly different. Have you tried the Google Nearby library? Do you think that sound modems still have a place now that Bluetooth LE is more of an option? edit: Also, do you have a browser version I can try?
I didn't try Google Nearby, since I was developing the modem to run on a desktop machine (but later I've created a simple Android app [1], supporting the lowest bit-rate).
Unfortunately, I don't have a working web-based version of my modem...
[1] https://play.google.com/store/apps/details?id=bit.zeyde.audi...
Earlier quoted context omitted.
~3 meters is indeed quite a challenging scenario. I've tested it with the lowest bit-rate supported (1 kbps), but it doesn't work reliably. You can try my Android app [1] to reproduce the experiments for short transmissions. [1] https://play.google.com/store/apps/details?id=bit.zeyde.audi...
Nicely done, I'll note for the readership here that a similar technique works fine at 300 baud across the room using FSK. Something you might consider is to write a web camera backend for it and use the screen/webcam. That has a lot more bandwidth and has higher SNR as the selector effect of the web camera is so much better than that of a microphone.
Earlier quoted context omitted.
Nicely done, I'll note for the readership here that a similar technique works fine at 300 baud across the room using FSK. Something you might consider is to write a web camera backend for it and use the screen/webcam. That has a lot more bandwidth and has higher SNR as the selector effect of the web camera is so much better than that of a microphone.
FSK across the room? Does that have noise restrictions? I’ve found all the phase modulation schemes work poorly across the room. DSSS works ok but is very slow. I would be curious how reliable FSK is in that situation.
Earlier quoted context omitted.
Nicely done, I'll note for the readership here that a similar technique works fine at 300 baud across the room using FSK. Something you might consider is to write a web camera backend for it and use the screen/webcam. That has a lot more bandwidth and has higher SNR as the selector effect of the web camera is so much better than that of a microphone.
hmm, if you where using a screen/webcam, could you do something horribly crude like flash QR codes and leverage their EC?.
Earlier quoted context omitted.
Nicely done, I'll note for the readership here that a similar technique works fine at 300 baud across the room using FSK. Something you might consider is to write a web camera backend for it and use the screen/webcam. That has a lot more bandwidth and has higher SNR as the selector effect of the web camera is so much better than that of a microphone.
FSK across the room? Does that have noise restrictions? I’ve found all the phase modulation schemes work poorly across the room. DSSS works ok but is very slow. I would be curious how reliable FSK is in that situation.
Earlier quoted context omitted.
FSK across the room? Does that have noise restrictions? I’ve found all the phase modulation schemes work poorly across the room. DSSS works ok but is very slow. I would be curious how reliable FSK is in that situation.
With 1270Hz/1070Hz you've got over 3 complete cycles to identify the tone at 300 baud, at higher frequency pairs it gets better. The person who wrote it was Tom Lyon at Sun but I bet I could reproduce it with a gnuradio-companion flow graph. That would make it pretty easy for anyone to play with it.
Author here, thanks for posting this :) Would be happy to answer any question.
Earlier quoted context omitted.
FSK across the room? Does that have noise restrictions? I’ve found all the phase modulation schemes work poorly across the room. DSSS works ok but is very slow. I would be curious how reliable FSK is in that situation.
I don't have first hand experience but I believe a big problem with sound channels is multipath propagation/challenging frequency response. FSK naturally deals quite well with those; it's similar to OFDM but more robust due to single carried symbols. You can extend the symbol period as long as you like while using an adequate number. Finally in challenging environments it'd a good idea to use error correction, not ju…
[1] https://ggerganov.github.io/jekyll/update/2018/05/31/data-ov...