Hacker News Reader

Comment by jsjohnst | Hacker News Reader

Iridium flies at about 450mi above the ground, SpaceX/Starlink does a bit lower around 350mi. Both are still a VERY long way to transmit a gigahertz signal, especially unless you are standing in a wide open area with no obstructions of the sky. Iridium uses frequencies well suited for space to ground comms and has specially designed antennas on both ends with high power radios (hence the whip antenna). Even with all that, Iridium is unreliable at best, but better than nothing. So now you want to do that with standard 5G frequencies (which are more impacted by weather), using standard terrestrial phone antennas and radios on the ground, and you expect it to work?

View on HN

Well, I’ve got a garmin inreach that uses iridium and it’s been quite reliable. Inreach mini is cell phone sized… of course it’s super low bandwidth so I assume that’s what’s gonna happen with the new functionality as well. Anyway all speculation at this point.

I spend a fair amount of time in northern New England and my mini takes a while to connect and sync up (10 minutes or more in some cases) and requires more or less stabilizing it somewhere where there is no tree cover. I wonder if these various satellite/phone connections coming online will require similar steps.

If my iPhone could replace my inreach for sos/simple texting and data I’d be over the moon. That’s all I want out of sat connectivity

Iridium and Inmarsat have transponders that are much higher power and have much higher RF bandwidth that supports devices at very low speed data rates.

It's very conceivable that with an L-band or similar patch antenna some kind of low speed connectivity can be accomplished with line of sight to the sky via a mobile device. There are already devices sold for hikers etc that operate like this (simple SOS text messaging etc) and sat tracking of vehicles and trucks. A lot of it is store and forward type stuff.

As for full voice and high speed data - yeah, that ain't happening yet at the consumer level mobile device.

> There are already devices sold for hikers etc that operate like this (simple SOS text messaging etc) and sat tracking of vehicles and trucks.

Yep, I’ve owned a ton of them over the years. My first was the FollowMeSpot device coming up on two decades ago. They’ve of course gotten a lot smaller, but are still definitely “thick fugly bricks” in comparison to Apple’s designs. Looking at tear downs of them, I see absolutely no way you’ll fit the important bits of one inside an iPhone case.

T-Mobile's likely going to use their 600MhZ spectrum allocation for this, which is lower than the multi-GhZ frequency used by the other parts of the 5G frequencies, and is less impacted by weather and goes further.

They already said it’s PCS, 1900Mhz.

Iridium uses the L-band; Globalstar uses the S- and the L-band.

5G phones support frequencies in these bands, and well above and below either.

Inmarsat, Iridium, Thuraya, and Globalstar primarily use L-band.

The early PCS allocations and a few later allocations (1900, 1800, 1700) are also L-band, but there’s good reason not to use them for this, they are already heavily in use all over. Satellite cells cover a large area and you don’t want to collide with a tower using the same frequency.

The 600-800mhz allocations are not great for satellite broadcast due to limiting characteristics of those bands.

So for the 5G bands that would not already heavily be in use and/or aren’t well suited to satellite use, that leaves us C band (3-5ghz), and K/Ku band (mmWave).

Reply on news.ycombinator.com