Thread by @ErrataRob

1/ No, the iPhone 13 will not talk to satellites.

Instead, the iPhone will (according to rumors) now support another radio band for 4G/5G that was previously assigned to satellite service but which now can be used for terrestrial service.

2/ That band is 2.4835-GHz to 2.4950-GHz.

If that looks too you suspiciously like 2.4-GHz WiFi range, then you'd be right: it's the upper half of Channel 14 in WiFi.

Most countries (except Japan) don't use Channel 14 for WiFi, though. U.S. WiFi goes to 11.

3/ Instead of WiFi, most countries assign it to GlobalStar for use with their "Mobile Satellite Service" (MSS). It's the downlink channel to their satphones, "SPOT" watches, data to oil platforms, satellite messengers, and similar things.

4/ It's long been popular among hikers for their SPOT watches. If you get in trouble, like falling off a mountain, then press a button, the watch communicates to the satellite, and rescuers will come get you.

But of course, phone/data are their biggest earners.

5/ GlobalStar spen5 $5 billion putting up its first satellites (and buying spectrum) then promptly went bankrupt (like their competitor Iridium). But spectrum licenses are valuable, so no investors grabbed their assets.

6/ Their strategy: take this 11.5-MHz wide band that's been licensed for satellite services and seek permission to use it for terrestrial services. They've so far convinced the US, Canada, Brazil, and Kenya, and applications are still pending in Europe.

7/ The obvious problem is that if there is a nearby TERRESTRIAL (on land) transmitter, it'll overwhelm the signal from SATELLITE (in space) transmitters. The way around this is to have the terrestrial devices support the same services.

8/ In other words, if a terrestrial transmitter is nearby, your SPOT watch will talk to it instead of a satellite. Only as you walk away will the watch switch to the satellite.

I have questions whether this will actually work. So do many others.

9/ Part of the compromise is that these terrestrial transmitters will only work at really low power, meaning, often only within buildings.

Also, 11.5-MHz is pretty narrow. And the entire service must fit within the band (instead of normal LTE which uses multiple bands).

10/ But apparently that is ok, because of the LAA ("Licensed Assisted Spectrum") trick. What you do is used the licensed spectrum, which is guaranteed free of interference, for critical stuff, and then normal WiFi spectrum for non-critical data.

11/ Presumably, then, you buy WiFi access-points that work as they currently do but then also work as a microcell for this LTE radio service. You get the best of both worlds: reliable phone calls, and high-bandwidth downloads.

12/ BTW, this is FCC document that describes all the concerns the FCC had. It's a fun read, as it includes concerns from their competitors who oppose granting this terrestrial addition to their spectrum license.
globalstar.com/Globalstar/med…

13/ This band, the upper half of WiFi channel 14, is designated as band n53 in the 5G specifications.
en.wikipedia.org/wiki/5G_NR_fre…

14/ Qualcomm added support for band n53 in their X65 modem. The iPhone 13 will use the X60 modem according to reports. It sounds like may a hacked version of the X60 modem instead.
investors.globalstar.com/news-releases/…

15/ An important part of this discussion is the difference between LICENSED vs. UNLICENSED bands.

Everything from 2.4 GHz to 2.4835 GHz is UNLICENSED, useable by almost anyone for anything.

But 2.835 to 2.5 GHz is licensed only for GlobalStar's use.

16/ This WIRED article explains why: microwave ovens can work at frequencies around 915 MHz, 2.45 GHz, and 5.8 GHz. They generate a lot of interference. So those bands were set aside for unlicensed use.
wired.com/2010/09/wirele…

17/ In other words, if some device causes interference in licensed spectrum, you can complain, and the FCC will shut them down. They have vans in every major city dedicated to finding violators and stopping them.

18/ But in the unlicensed area, the rules change. It's up to you to deal with interference. If your neighbor's devices are interfering with your WiFi, well, it's your problem (generally), not your neighbors.

19/ There are still rules -- it's just that they are very relaxed for the unlicensed parts of the spectrum. Moreover, the key difference is that spectrum doesn't belong to anybody in particular.

20/ Okay, the FCC aren't constantly prowling the streets, and some constituencies matter more than others. I hear they get very uptight about any mobile phone interference, but at the same time, are relaxed for things like law enforcement.

https://twitter.com/mattblaze/status/1432199440144678912

21/ God I hate typos deep in my thread. That's "new investors" not "no investors". The word "spen5" is, in retrospect, spelled correctly.

https://twitter.com/ErrataRob/status/1432189447462924289