The issue you linked to is about MeshCore using channels that are too narrow. A mesh system claiming to offer 100x bandwidth is probably not violating regulations in that particular way.

▲

colanderman 5 hours ago | parent | next [-]

Correct. The LoRa configurations mentioned which offer 100× the speed of Meshtastic/Core operate at 800 kHz and 1.6 MHz bandwidth, which are permitted by the FCC in 15.247.

As far as I know there's not actually anything particular to 2.4 GHz allowing higher throughput for LoRa than that the corresponding Semtech chip happens to support wider bandwidths. (I.e. no legal barrier.)

The tradeoff is less range due to lower link budget. Doubly so because 2.4 GHz has higher free-space path loss. You're not going to get outside your house with these speeds. The primary use (as stated in the original post) is likely through clear space with a directed antenna.

(The 2.4 GHz band is better suited to this use since you can use antennas with higher than 6 dBi gain. If my math is correct, anything higher than 11 dBi is a win even accounting for FSPL and the power derating the FCC imposes.)

(Aside, I am the author of that MeshCore ticket.)

▲

nerdsniper 2 hours ago | parent [-]

What issues does it create for others to use too narrow of a bandwidth? Why “should” the FCC care if someone is only using a small portion of the spectrum that would otherwise be fine fr them to use?

Thanks for educating us!

	▲	colanderman an hour ago \| parent \| next [-]
		Spectral power density is the primary concern. The legal power limit in these bands is 1 W. If you spread that out over 500 kHz, that signal is weaker than background noise at any given frequency for anyone more than about a city block away. (Give or take many factors.) But, if you compress that 1 W into, say, 12.5 kHz (typical for FM voice), your signal is now detectable (and will interfere with other, possibly licensed, users) at over 6 times the distance. There are probably other factors. For example, it's not legally sufficient to simply reduce your power by a corresponding factor. I suspect it may simply be the FCC's goal to reduce conflict between users by mandating spread-spectrum technologies for unlicensed use. Note also that 47 CFR 15.247(e) [1] gives a spectral power limit which corresponds approximately with the 1 W max / 500 kHz min specified in (b)(3) and (a)(2). Final side note – https://docs.fcc.gov/public/attachments/FCC-02-151A1.pdf is interesting reading as to how the current form of 15.247 came to be. Specifically it changed the rule from specifically DSSS to digital modulation generally, which in turn allowed the transition from 802.11b (DSSS) to 802.11g (OFDM) on 2.4 GHz. [1] https://www.ecfr.gov/current/title-47/part-15/section-15.247...
	▲	codys an hour ago \| parent \| prev [-]
		The idea with either requiring very wide band or frequency hopping on the 900Mhz band is to make it so that usages of the 900Mhz band 1. are tolerant to some loss (ie: by temporary collision) and 2. don't collide continuously (by using wide band or frequency hopping). It's a mechanism to try to make the 900Mhz band more useful to uncoordinated users.

▲

nunobrito 8 hours ago | parent | prev [-]

There are more rules being broken. For example, overusing the frequency which effectively prevents others users from sending messages.

In the end, won't be used.

	▲	nubinetwork 7 hours ago \| parent [-]
		In the EU, the duty cycle limit is like 10% per hour. North America doesn't have that restriction...