Google is bringing satellite messaging to Android 15 | Hacker News Reader

Google is bringing satellite messaging to Android 15

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35 pointsjoak29 comments

If i want to buy a smartphone that can talk to satellites, which 5G band do i need?

I don’t think there are any 5G-NTN (non-terrestrial network) devices or operators right now for “regular” 5G.

There’s the Motorola Defy 2, which can send short messages via satellite (I think using an IoT version of 5G), but the manufacturer/operator apparently just went bankrupt.

In Europe or Asia, you could get something compatible with Thuraya; they’ve been around for a while and offer satellite-connected smartphones (although it’s a proprietary standard, not 5G).

Other than that, Starlink plans to add LTE coverage in some countries on regular terrestrial frequencies, i.e. the ones your phone very likely already supports.

It's pretty likely that you need a particular frequency band for this enormous distance.

No, the frequencies used are pretty much in the middle of commonly used terrestrial bands.

The specified non-terrestrial 5G bands are in the MSS part of the radio spectrum:

Apple's solution uses Globalstar, where the phone transmits on 2.5 GHz and receives on 1.6 GHz (I think that must be the newly-specified 5G band n254). Iridium uses 1.6 GHz in both directions (no 5G band assigned); Inmarsat is on 1.5 and 1.6 GHz (band n255), and Echostar (formerly Terrestar), which is used by the Motorola Defy, uses frequences around 2.0 and 2.2 GHz (band n256).

Since there's pretty much always a line of sight to the satellite, the usual rule of "lower frequency means better propagation" doesn't really apply, and in a vacuum, all frequencies propagate equally.

The path to the satellite is mostly not in a vacuum which is why some frequencies are not suitable. For example around 2.4Ghz is an absorption frequency of water which is why this freq is popular in microwave ovens as well (and thus why they cause interference with WiFi).

This is why the 1.6Ghz band is so popular, as it's the least affected. I would imagine 2.5Ghz being not so ideal but Globalstar is a pretty basic repeater system so I imagine they had to separate the input and output frequencies a lot to avoid huge filter systems to avoid it causing interference on itself.

Is this different from the LTE functionality being deployed by Starlink et al which (to the best of my understanding) delivers cellular service using standard LTE functionality in within cellular frequency bands and thus didn't require specific {hard,firm,soft}ware support on the mobile device?

Probably, since Starlink supposedly doesn't need any modifications on the device side and uses regular LTE.

I suspect that this Google service acts as a bridge between RCS and existing and upcoming (non-3GPP or 5G-IoT) satellite messaging services that require some proprietary protocol between the baseband and satellite network.

For example, Iridium SBD is a request-response based protocol not based on SMS or IP that doesn't require large external antennas (unlike Iridium voice calls); this could be used by a phone manufacturer or operator partnering with them to hook that protocol into the default Android messaging application.

Let's be clear. When we talk 'satellite communication' I mean 'from the middle of the Sahara desert' or 'deep within Siberia' or 'remote location in Australia' etc. Absolutely no chance of regular mobile phone network around. The kind of stuff one could use when otherwise they'd be funked.

And for that I was under the impression that one needs expensive and clunky specialized phones like the Iridium ones: https://en.wikipedia.org/wiki/Iridium_Communications

Is this even possible without a hefty wattage and big directional antenna?

You would think that after apple did the same thing a couple of years ago on iphones, people on tech websites wouldn't be asking questions like "is this even physically possible?"

Try to see it from the positive side: GP is one of today's lucky 10000 :) https://xkcd.com/1053/

It is! Voice communications currently still require an external antenna today, but there's a lot of movement in this space.

Text messaging is already possible on iPhones 14 and newer, on the Motorola Defy 2, various handheld GPS messengers (Garmin InReach and others), and soon supposedly on all unmodified LTE phones when Starlink launches their "Direct-to-Cell" service: https://www.starlink.com/business/direct-to-cell

Curious: Why does SpaceX say it’ll work on the Great Lakes, but not on the ocean? Don’t the satellites cover the whole planet? Are they somehow hibernating when traversing the ocean or…

Ah. I think I know the answer. They can only serve internet as long as the satellite can see the client and a ground station at the same time. Hence the Great Lakes will work, but the Pacific won’t. Right?

> Ah. I think I know the answer. They can only serve internet as long as the satellite can see the client and a ground station at the same time.

Aren't they making a big deal about some sort of laser communications mesh networking across the entire satellite constellation, though?

A few years from now Apple will invent satellite messaging and we'll all fall in love with it.

Don't they already use it for emergency purposes on the Iphone 14 and 15? For free on the new phones but I think it is getting subscription based soon.

Yes https://support.apple.com/en-nz/105097

I believe Apple literally holds the patent on this. It's in use.

I'm not sure what the patent would be on considering satphones with texting have existed long before iphones with satellite SOS showed up.

Are you referring to US patent number 20220312182 or what?

https://patents.google.com/patent/US20220312182A1/en?oq=2022...

As usual, some generic manufacturer copies some iPhone feature and people say this stuff. Pretty amusing.

And as usual, some people believe Apple was the first to invent some feature, while it’s really been around for many years.

Iridium has offered a global satellite phone service since 1998, and the first satellite-capable “regular” mobile phones without a huge external antenna started showing up in the early 2010s (Thuraya in EMEA and Asia, Terrestar in the US).

Satellite mobile telephony is only literally rocket science these days.

Ok, but having these emergency features on a regular phone, with free service (I think for two years when you buy a phone) is a game changer.

I'm not denying that it's a very cool and useful feature!

But it is, in the end, an almost prototypical Apple feature: Making something that's been technically possible, but mostly a niche feature, mass-market accessible.

Again, very cool and I love having it on my phone, but I just wouldn't call it an Apple invention.

I wouldn’t call it an iridium invention either. The military has been using satellites to send messages before Iridium.

Definitely, but Iridium was the first constellation offering 100% global coverage using inter-satellite links, and as far as I know they also pioneered the "bulky cell phone" form factor (as opposed to briefcase- or backpack-sized terminals).

Yeah, some incremental improvements on existing technology for sure. Definitely worth that credit.

It was an absolute marvel of technology for its time, in my view.

I think they really were the first to do in-space inter-satellite routing. If you call one Iridium phone from another, the call will never touch any earth-side infrastructure (after call setup). And they've been the only ones doing that until Starlink recently launched inter-satellite links.

All of that in 1998, when everybody else was still doing "bent-pipe" style satellite communications, and putting things into space was still prohibitively expensive!

SKYPHONE is an Android and satphone https://www.tiktok.com/@techradar/video/7341099055587577120

It uses Thuraya which is two geosynchronous satellites.

I don't get why more phones don't have better antennas like SKYPHONE with Starlink (500km) coming soon vs Thuraya's 40,000km geosync.

A good antenna should help with normal old bad reception as well.

What makes you think it’s a matter of antennas? Unless you mean directional antennas, which are quite inconvenient in a smartphone, existing ones do just fine as evidenced by existing and upcoming mobile satellite services.

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