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Comment by arbuge | Hacker News Reader

More detail here: https://www.cnbc.com/2022/08/25/spacex-and-t-mobile-team-up-...

"T-Mobile users will be able to use messaging, MMS and certain messaging apps, from remote points across the lower 48 states, Alaska, Puerto Rico and Hawaii and even some remote points in the water.

Eventually, the service will work with voice, Sievert said. T-Mobile plans to include the service in its most popular mobile plans but did not disclose specific pricing.

Musk said the service will work with Starlink’s second generation satellites, which have very large antennae and will be able to transmit directly to a cell or mobile phone.

The service won’t require mobile users to get a new phone. Musk said in or after a natural disaster, even if all the cell towers are taken out, the planned service should work."

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Interesting. Is there no distance limit? I don't know how 5G works, but in 2G there was a limit of about 30km, since that's as much as the timing advance would allow for (sending the signal early so that it arrives in its timeslot despite the speed-of-light delay).

I'm also pretty out of date, but I believe in LTE (4G) the max distance was closer to 100km, with the timing advance controlled in the radio protocol. As I understand it, the 5G radio protocol should be fairly similar to 4G, it wasn't completely reinvented for once.

Based on my read of the summary of a couple Mbps per cell and focusing more on low bandwidth services like texting makes me suspect they're right at the limits of what the tech will allow. Since they're advertising compatibility with existing hardware, makes me suspect there is an extension somewhere in the standards that allows the timing window to be increased, or maybe there's some clever hackery going on, like only scheduling every other timing window and cutting bandwidth in half.

Which might work on the uplink, but on the downlink I think it's more complicated to support something like paging, where the UE is mostly idle, and only wakes up occasionally, that things don't get out of sync with the moving satellite.

Yes indeed, LTE max cell size is 100 km.

There's a system using LTE to backhaul Internet traffic from planes (WiFi in cabin, with a LTE to the ground), working with larger cells of up to ~900 km from memory, but it doesn't use standard LTE for example. It uses a modified variant made to support the possibly larger propagation delay coming with larger cells.

For 5G (NR), the max cell size has been increased and depends on the OFDM subcarrier spacing. For a 15 kHz SC, same as LTE, the max cell size is 300 km. This value is halved each time the SC doubles.

There's work on-going to extend NR to non-terrestrial networks. I don't know where it stands right now, but it'll likely add larger cells support. But it's not there yet for sure.

I'd think that the distance limit for _terrestrial_ mobile networks comes from the guard interval of the OFDM modulation [1]. I.e. on longer distances the time-offset between different different reception paths (due to reflections) of the signal becomes so long that you cannot compensate those with just a complex gain-factor of the OFDM vectors.

AFAIR LTE (4G) even uses different guard intervals depending on rural vs. city setting because that time-offset is larger in rural areas (less base station density).

I would not expect those problems to be relevant for satellite communication as ground<->satellite does not suffer much of the multi-path signal propagation of terrestrial systems. (IIRC DVB-c sat-TV broadcasts did not even use OFDM, at least not for the older "v1" DVB-c standard).

[1] https://en.wikipedia.org/wiki/Orthogonal_frequency-division_...

Nitpick: You probably mean DVB-S (and S2, S2X..) rather than DVB-C, and you're correct that they don't employ OFDM (they're just a straightforward single wideband channel mostly employing variations on phase-shift keying), and aren't particularly concerned with multipath interference.

In 2G GSM there was this limit, because GSM used very strictly managed timeslots for each call. If a phone was too far away, its signal would arrive out of bounds of the timeslot and this was the reason. The protocol didn't have any compensation built in.

However 3G and onwards were based on CDMA tech (which was the competing 2G tech to GSM), which is very different. CDMA doesn't have strictly managed cells, but rather the basestation picks the signals out of a cacaphony (very simplified). So the same issue doesn't apply.

2G was much more static than CDMA, it had a strict capacity of a number of calls per cell. But the range (up to this 30km) was pretty good because when a phone transmitted the air was clear. CDMA cells used to 'breathe': Have much lower reach during busy times (because weak signals could no longer be identified) so gaps could drop in the network. ON the other hand, 2G got busy with a fixed capacity.

2G did have prioritisation though when the network was full. If you called 112 (the international emergency number) it would kick someone else off to make space for you.

Certain messaging apps...

All bets are on centralized and/or proprietary ones that can afford to pay for the privilege. I have been saying from day one that Starlink is well poised to end net neutrality.

Net neutrality is not a good thing in and of itself. It is one value among many.

If you're a firefighter trying to call for assistance from base camp, you don't care about net neutrality. You want your emergency phone call to have priority over everything else. You want the net to be extremely non-neutral.

On the general internet, where bandwidth is plentiful, net neutrality can keep certain pathological things from being a thing. On a specialized network where bandwidth is very scarce, it can be the cause of pathology.

> All bets are on centralized and/or proprietary ones that can afford to pay for the privilege

Or not.

App like Silence (https://silence.im/) have been able to do secure e2e messaging using SMS as transport layer for almost one decade now.

SMS makes it very hard to be anonymous. Not a good option IMO.

> SMS makes it very hard to be anonymous. Not a good option IMO.

How is that even related ?

Silence is the equivalent of Signal over SMS instead of the usual Mobile Data: There is nothing by design in Signal to stay anonymous.

E2E encryption are mainly there to prevent eyes dropping, not to provide anonymity.

I was simply pointing out Starlink supporting SMS is not good enough, even with layers like Silence on top.

Good enough for what? If you have SMS where you didn't before you're still equally free to not use it. Personally I like the idea of always having a simple channel for emergencies.

Not good enough to be the only standard form of communication permitted other than a handful of centralized proprietary apps.

A journalist or a dissident may wish to get critical communications out from a remote area without exposing their identity or location.

Then this isn't the solution for them. You keep assuming this is an internet service when it's not. Internet protocols are massively inefficient and have latency constraints that would choke narrow channels while offering almost no utility. This will be a modified SMS service, not a not an IRC service. Don't like it? Go buy an actual satphone with a data plan.

Whose goal is to solve this? Not T-Mobile or SpaceX

When you are the only source of a critical service in an area, you become a utility and should shoulder the responsibilities that come with that.

They don't have a responsibility to help you stay anonymous if they don't promise it. Follow your logic and we wouldn't have remote schooling or medical services over HF radio either. It extends the capabilities of normal phones to provide a feature we didn't have before, so you can't expect the capabilities of full fat, dedicated hardware. It's better than nothing, so why complain? You want net neutrality for a non-Internet service?

A major use case is in emergency situations or catastrophes when no classical cell service is available. If you are hoping to message someone to rescue you, I don't think anonymity is your concern.

Unless you are a journalist or a dissident and need to relay information that will save human lives, but cannot risk exposing your identity, location, or the message content to anyone but the recipients.

Not all emergencies are the same.

At the event they addressed this, and said they would work with anyone, and that the real issue is making sure that the data is correctly identified as messages and not generic data. This apparently would require back-end work between T-Mobile and the messaging app to identify the data in some way.

This is a net neutrality killer any way you look at it as whitelisting apps in any way will by design mean blocking legitimate privacy focused messaging solutions that do not have fixed IP addresses or identifiable traffic patterns.

I somehow doubt for instance they would have a way to allow a federated and often self-hosted messaging protocol like Matrix over an anonymization networking layer like Tor, which is the only chat solution I use.

Breaking net neutrality even a little bit has consequences like creating network effects further favoring centralized solutions forcing vulnerable people like journalists, dissidents, female healthcare seekers, etc, to take on a lot more risk.

If SpaceX has bandwidth limitations they should cap everyone to dialup speeds and keep it neutral.

If they insist on breaking net neutrality, people like me will be forced to do stupid nonsense like piping arbitrary TCP/IP as base64 blobs via chatbots over some whitelisted app like Whatsapp. Or masquerade traffic as port 53 DNS queries like dnstunnel.

Protocol/app whitelisting will most discriminate against those with low technical ability.

We have been down this road.

How? Net neutrality applies to the internet. You could run a private mobile network and allow or disallow anything you want on it. The reason it's bandwidth limited is probably because they're using dedicated SMS/MMS channels, as was field tested and proven earlier. T-mobile will likely write or allow modified chat apps that use these channels. So there's nothing to indicate this would be a limited Internet service. And if you didn't want it your options would be no worse than they are now.

https://techcrunch.com/2020/03/18/lynk-sends-the-first-text-...

I mean, sort of?

I believe they have some sort of similar solution in place for free messaging on in-flight wifi. Having a look at how they've done that might give a better idea for what this will look like than speculation.

Still, it's a hard problem. They want to prioritise connectivity on an extremely low bit-rate channel that covers an extremely large geographic region. Messaging apps needs to be a part of that connectivity solution, but you can't have one user making the entire cell unusable by everybody else. I don't know if there is a 'net neutral' way to do that, but would love to hear your ideas.

I think it is quite simple. Just apply net neutrality rules to this like any other internet connection.

If they can afford to support whitelisted messengers at a very limited data rate of 1k/s then they can afford to simply give people 1k/s of neutral internet access to use to communicate whatever data they feel is high value enough to fit over those constraints using any protocol they wish.

We already have internet access over HAM radio via net44. Highly bandwidth restrictive because of physics, but you can get a permanent IP assigned to your callsign and use whatever software you want with your tiny bandwidth pipe even in the middle of the ocean.

I don't think the speed of text messaging allows for many other meaningful data types. Someone encoding video into the GSM-7 format used by SMS will still consume more data than the typical person typing and sending text messages (which is what, 140 bytes each way per minute on average?).

There is also the difference between free and paid. Sure, if you're paying, you should be able to do whatever you want at the advertised speed and data limits. But for a free feature, I think it's alright to limit to SMS and other texting apps (already done on inflight wifi and it works just fine).

Why not just limit to SMS? Because travelers' home carriers might levy roaming charges on SMS, and WhatsApp / Telegram / iMessage is already de facto in most of the world.

This is exactly why net neutrality rules were a bad idea, because of insane proposals like this that would kill legitimate innovation. If you are lost in the woods without a cell signal, you don't want someone downloading a podcast episode at 1k/s sucking up all the bandwidth.

Maybe they are downloading a low res video demonstrating an emergency field medicine procedure to save a life far from hospitals. Maybe they are a journalist or a whistleblower uploading a picture that may change the outcome of a war.

A central party trying to decide what data is most important is going to be wrong when it counts most.

If a single user is monopolizing all bandwidth and a new user joins, throttle the existing user in half to make room.

There might also need to be a way to signal a need for emergency bandwidth, 911 style, that can give you priority access for a short time window, with the option for a carrier to cut off your device IMEI entirely if it is used too frequently.

In practice though they want to offer bursty throughput. For example, if you want to allow sending photos in messages, but not videos, you don't want to send a photo at 1k/s. It's not a trivial problem.

This is probably just a temporary solution to give everyone SMS capability after the fact - why would you assume this is permanent? Obviously the goal is to get everyone global internet. What happens at that point will determine net neutrality but that is far off into the future.

> T-Mobile plans to include the service in its most popular mobile plans but did not disclose specific pricing.

No, he said that it would "most likely" be included with the most popular mobile plans for free.

"I would expect our pricing for this service to be the un-carrier's favorite price: we expect, on our most popular plans, for this service to be included for free"

https://youtu.be/Qzli-Ww26Qs?t=851

Yes, that's what I said.

Edit: Downvotes are happening for some reason. "most likely" and "I would expect" mean basically the same thing unless we're playing grammar police.

The entire point of my above post was to deny the fact that they "did not disclose specific pricing". That was the part that was incorrect that I was correcting, as shown in the long form direct quote.

> "most likely" and "I would expect" mean basically the same thing

And so does just saying the claim with no qualifiers. Of course when you’re making a claim you’re expressing that you expect it to be the case with high likelihood. That’s what making a claim is.

I have no idea what you're saying. My ONLY point was that it wasn't unknown pricing data, it was stated to be free.

The direct quote is more descriptive as it claims "we expect" instead of "most likely". The quote implies that it's based on preliminary cost data and could change, while "most likely" almost sounds like it's based on a dice roll and is vague about exactly what is contributing to the uncertainty of the statement. He chose his words carefully.

> to transmit directly to a cell or mobile phone.

If it could talk directly with mobile phones it's a game changer.

But I don't understand how it could be physically possible without phased array and satellite tracking for a phone to transmit anything back to satellite. If achieved, even a few bytes per minute would already be big.

You could also just have the recipient in the first part of the message block so that the devices that aren't the recipient either just ignore the message or can't decode it.

My biggest question is how do you send a signal to a satellite with your mobile phone. And they're even saying without additional hardware which makes it even more difficult.

Or are they just hoping that there would be no obstructions from your device and the satellite, no roof and a good sunny weather?

Although my knowledge is lacking, my understanding is that 2G has good range at the expense of low data rate. But I have a feeling that many modern phones no longer support 2G, since (at least here in Slovenia, Europe) many providers have over the years lowered or totally removed the number of 2G towers.

It's supposedly already been demonstrated by a different company: https://techcrunch.com/2021/09/29/lynk-demos-global-satellit...

The quotes here are only about transmitting to cellphones, not about receiving from cellphones. Is uplink also a part of the plan?

If it's TCP then there's an uplink implied.

> Musk said the service will work with Starlink’s second generation satellites, which have very large antennae and will be able to transmit directly to a cell or mobile phone.

This has far greater implications than dead zones, yacht's (or) Oil rigs; 'Telecommunication during natural disasters'!

With increasing number of extreme weather events, Our conventional telecommunication systems(especially base stations) cannot stand a chance against natural(man made?) disasters. Yet, Apart from few nerd group projects like disaster.radio I see no real work in building disaster resilient telecommunication network.

P.S. If you live in India, Especially in south-western India and are interested in https://disaster.radio project for your region then give me a ping. I've been trying to get it started for ages.

>T-Mobile plans to include the service in its most popular mobile plans but did not disclose specific pricing.

Hopefully this includes $20 Kickstart!

does this extend to TMobile based mvno’s like Mint Mobile? cant tell

Doesn't seem logical as this feels like a premium service. We'll find out soon enough though.

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