Comment on Why don’t wireless connections (WiFi, Bluetooth, etc.) use anything between 2.4Ghz and 5Ghz?

litchralee@sh.itjust.works ⁨1⁩ ⁨week⁩ ago

Also, what if things that require very little data transmission used something lower than 2.4Ghz for longer range? (1Ghz or something?)

No one seemed to touch upon this part, so I’ll chime in. The range and throughput of a transmission depends on a lot of factors, but the most prominent are: peak and avg output power, modulation (the pattern of radio waves sent) and frequency, background noise, and bandwidth (in Hz; how much spectrum width the transmission will occupy), in no particular order.

If all else were equal, changing the frequency to a lower band wouldn’t impact range or throughput. But that’s hardly ever the case, since reducing the frequency imposes limitations to the usable modulations, which means trying to send the same payload either takes longer or uses more spectral bandwidth. Those two approaches have the side-effect that slower transmissions are more easily recovered from farther away, and using more bandwidth means partial interference has a lesser impact, as well as lower risk of interception. So in practice, a lower frequency could improve range, but the other factors would have to take up the slack to keep the same throughput.

Indeed, actual radio systems manipulate some or all of those factors when longer distance reception is the goal. Some systems are clever with their modulation, such as FT8 used by amateur radio operators, in order to use low-power transmitters in noisy radio bands. On the flip side, sometimes raw power can overcome all obstacles. Or maybe just send very infrequent, impeccably narrow messages, using an atomic clock for frequency accuracy.

To answer the question concretely though, there are LoRa devices which prefer to use the ISM band centered on 915 MHz in The Americas, as the objective is indeed long range and small payload, and that means the comparatively wider (and noisier) 2.4 GHz band is unneeded and unwanted. But this is just one example, and LoRa has many implementations that change the base parameters. Like how MeshCore and Meshtastic might use the same physical radios but the former implements actual mesh routing, while the latter floods to all nodes.

But some systems like WiFi or GSM can be tuned for longer range while still using their customary frequencies, by turning those other aforementioned knobs. Custom networks could indeed be dedicated to only sending very small amounts of data, like for telemetry. That said, GSM does have a hard cap of 35 km, for reasons having to do with how it handles multiple devices at once.

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