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I am doing a pretty specific project, where I plan to connect up to 150 devices, mostly depending on ESP32 and a few ESP8266 devices.

All of them will be located in a tiny space of around 5-8 square meters.

  • Are there any research or norms (like ISO in Europe) that touches that topic?

  • Is it healthy to have so many active devices in such a small space?

  • How many wifi devices (ESP32 or ESP8266) can be “mounted” in one square meter (Ideally some researches or legal norms, not “just experience” or “commons sense” because this project aims to be a commercial one)

  • Is this a really health concern?
  • are there any research on that?
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    \$\begingroup\$ why do you need do many RF devices in such a close proximity to each other? \$\endgroup\$
    – jsotola
    Commented May 2, 2020 at 20:58
  • \$\begingroup\$ also: ISO is the international standards organization, and is adhered to world-wide, not only in Europe. \$\endgroup\$
    – Marcus Müller
    Commented May 2, 2020 at 21:56

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Ok, that system makes no sense at all. IEEE802.11a/g/n as used by these devices is collision avoidance-based. That many devices in this little space would inherently lead to congestion.

Is it healthy to have so many active devices in such a small space?

No, because doing this means you've probably been drinking heavily!

How many wifi devices (ESP32 or ESP8266) can be “mounted” in one square meter (Ideally some researches or legal norms, not “just experience” or “commons sense” because this project aims to be a commercial one)

That's not touched specifically by legal limits, because the single-device legal limit suffices: these devices will avoid interrupting each other, so there will be constant congestion, and very few devices (as in: 1, or 2 per channel pair) will be active at a time.

So, already covered. Also, this commercial project will be a total failure.

There's nothing unhealthy about this. These devices are specified to not be active at the same time, so a) your network won't work, and b) even if it did, it would be totally harmless.

Also note that wifi devices do power control, i.e. when they talk to another device they know is close, they reduce their output power.

Just a quick calculation: 150 devices on 8 m² is one device every 12.3 cm, if you used the densest possible packing (that's hexagonal packing in the 2D plane). At that distance, you're not even in the far field of the antennas with your neighbor's antenna, and thus, the thing will totally break down, I'd presume.

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so you will have about 50 cm between devices. [assuming 8meter by 8meter working area]

Assume 900MHz frequency. Quarterwave is 8 centimeters, so you COULD have a 3" vertical whip antenna on each, as part of some handle.

At 100,000 bit/second data transfer, you'll need -20dBm from each of the nodes, or about 0.0000010 watt.

Biggest issue is time-aligning the packets, to avoid interference.

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    \$\begingroup\$ 900 MHz is a false assumption, these things are 2.4 GHz ISM band \$\endgroup\$
    – Marcus Müller
    Commented May 2, 2020 at 21:47
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    \$\begingroup\$ also, hexagonal packaging occupies the 8m²/150 that each device gets to 90% with a circle, so that's \$r=\sqrt{\frac{0.9\cdot8\,\text{m}^2}{150}}\$ between these devices, and that works out to 12.3 cm for me! Your 50cm must also quite intuitively be wrong: if that was the distance, you'd fit four, maybe five into a square meter – but you need to fit nearly 20 per square meter! \$\endgroup\$
    – Marcus Müller
    Commented May 2, 2020 at 21:48

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