SpaceX just achieved speed of 17Mb/s from satellite to stock Android phone | Hacker News Reader

SpaceX just achieved speed of 17Mb/s from satellite to stock Android phone

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173 pointsgrecy93 comments

Want to emphasize Elon's follow up that this is the peak for a beam, and the beams are very wide, so this is basically only possible in places far from ground based networks and probably also requiring the place to be sparse enough to only have the one device in the beam area.

Elon's tweet also doesn't mention upload speed. Download speed isn't very useful when your trying to send a MMS showing where your trapped and it's taking tens of minutes to upload.

This hypothetical case of sending a large multimedia message instead of 8 bytes for latitude and longitude and 3 more bytes for the letters "SOS" doesn't seem sincere.

minor fyi. Had to look up how to get lat/long on an iphone without internet access. It’s in the default compass app.

Where? Mine has zero options now - just displays the compass, with the level in the middle.

Seems it's not available everywhere, for some reason.

> Note: Your coordinates and elevation may not be available in certain countries or regions.

https://support.apple.com/en-gb/guide/iphone/iph1ac0b663/ios

some reason = GNSS: https://medium.com/@ilyakorogodin/where-is-a-navigation-chip...

Article opens iPhones of several generations since iPhone 3G to discover how they do GNSS positioning.

Thanks, this article pointed me in the right direction. Coordinates were missing for me because locations services were disabled for the Compass app.

Google Maps and Apple Maps show it when you set a marker. You don‘t need internet.

I would be less worried about bytes and more about the general TCP handshake/acks making it through. You can easily add height, heart rate, and all other kinds of information before you come close to the network overhead. You could also gamble UDP+overhead, but I assume you want some kind of assurance that your SOS made it through.

You also need to be able to get a session within the beam. If you're stuck in the middle of a desert you'll be fine, but if you're within range of a minor town you may not be able to get any signal.

Not an expert, but my understanding is that SMS text messages don't rely on TCP or UDP. Instead, they use their own protocol called SMPP with an overhead of less than 100B.

This hypothetical case, on the other hand, only require two bytes of the reply, with letters "OK".

Antennas couple the same both ways.

But power doesn’t, right? Happy to be corrected (please, educate me!) but I think this is asymmetric, in practice.

That does not guarantee two-way communication. Pick-up patterns, resonance and filtering, power and local environment makes SNR highly asymmetrical.

Imagine you focus a high gain antenna dish A at an isotropic antenna B. A will almost exclusively hear B, but B will hear things from all directions, making it harder to single out A. Now, A could use their higher gain to scream louder at B - but that's not always a viable option, and could just peak the frontend of B if done wrong.

Different antennas and radio circuits have different selectivity, dictating how they react to nearby noise. A dedicated tranceiver station is often much more selective than consumer devices meant to handle many bands and protocols using a small set of multi-purpose antennas and with space requirements limiting room for radio frontends and filters.

The power rating of a dedicated transceiver station may also be quite a bit higher than that of a portable device, adding to the asymmetry.

There are also differences in atmospheric effects - primarily reflection and refraction - which for these wavelengths happen in the troposphere. With refraction happening closer to the ground (from the perspective of orbit), that makes for another SNR asymmetry.

To achieve this kind of speed, you need at least around 600kbps at the barest minimum for TCP ACK packets (~50 bytes), assuming that downstream packets are full-frame 1500 bytes.

That’s not really true since one ACK packet can acknowledge multiple RXed data packets.

The tweet's 17 Mb/s is UDP down from satellite, so no ack replies from the phone, and 15% packet loss.

So it really doesn't say anything about upload speed.

A map for how to get out, or a video for first aid procedures, or a guide on what's safely edible around you, or other survival information until help can get there can make a big difference.

Those all could be unnecessary with advanced planning

The nuance of this news is that it is a for a standard consumer mobile device. It is not intended to replace coverage in areas where telcos exist, rather to supplement in times of spotty coverage or emergencies.

>@Elon: This service works in partnership with wireless providers, like what @SpaceX and @TMobile announced.

In your scenario you would likely be sending text/sms based communication as a primary priority (ie. coordinates, instructions) with MMS as a secondary luxury.

If you are permanently or frequently in an area without telco service you would want to make use of specialized hardware which is optimized for starlink communication. For example, here is video of Elon using starlink for video conferencing which demonstrates not only high upload speeds, but also quick swapping between satellites without disconnect.

https://youtu.be/tKqJ5-kkUGk?si=RVilCEke7J3zXoQK&t=367

If future satellites have fold out antennas that are 45 meters diameter, spot sizes of half a mile are possible. With that, service will make sense everywhere except urban areas.

45 meter fold out antennas are very possible. Imagine you screen print antenna wires onto a mylar sheet, then double up the sheet and seal the edges to make it like a large airbed. Then, when in space, inflate it.

I don't think it's very easy to find air in space, though.

Doesn't matter. An airbed will hold its shape with just 0.1 psi of pressure, and that works out to only 0.6 kg of compressed gas for the whole thing.

Once inflated, there are no forces causing it to fold up again, so it doesn't matter if the gas leaks out of holes after years.

Gravity -- it is within the earths gravity well, this force still applies.

Thrusters -- satellites have thrusters to keep it in orbit and to avoid obstacles.

Thus losing pressure will cause the inflatable to lose shape.

Gravity is effectively nil on a satellite - the satellite is within the gravity well, yes, but is constantly falling in a parabolic path, so doesn't feel any gravity. The total forces experienced due to gravity and related forces will be nano-newtons, so irrelevant. They are dwarfed by the drag force.

Thrusters are ion drive thrusters, so have typical forces of 2 milliNewtons (0.2 grams-force). I don't think 2 millinewtons will be sufficient to fold an airbed-like structure, even with 0 internal pressure. (imagine a fly lands on a plastic bag... the fly isn't heavy enough to flatten the bag, even though the bag has no internal structure - a fly is about 0.2 grams).

Inflating is such a cool idea, it'd work for any 3D shape I can think of.

If keeping air pressure is an issue, that might be resolved by making the sheet rigid once deployed. Are there UV curing resins that won't cure at all before being exposed to UV?

Speaking of sunlight, heating from the sun could be used to create the pressure for inflation. Or off-gassing from UV induced reactions.

Most plastics slightly 'cure' in UV anyway, in that they lose their plasticity and become more rigid.

I think regulators would be much more hesitant to allow thousands of 45 meter diameter antennae in low orbit.

That's a significantly increased collision risk, as well as increasing interference with astronomy and potentially increased brightness mitigation challenges.

Practicality wise, such a large antenna would add a lot of drag, such as to meaningfully shorten how long a satellite can stay in operation (which would cause an entire bunch of tradeoffs in terms of mass budget to need to be reevaluated).

> more drag

That's true - although the antenna can be oriented to be perfectly parallel to the direction of travel - therefore only experiencing drag from the edge cross sectional area.

> increasing interference with astronomy

The antenna could be painted matt black. It can also consist of ~95% holes without much loss in functionality.

> increased collision risk,

I don't think it will matter while the number of uncontrollable satellites remains low. If I were a regulator, I would put a cap on the number of uncontrollable satellites that may be in orbit at any given time, and if that cap is exceeded prevent all new launches and require active de-orbiting of existing ones.

It’s more likely you choose a higher frequency to narrow down your spot size vs growing your antenna comically large. Increased frequency also allows for increased bandwidth.

17Mbps UDP downlink to standard smartphones. Half a dozen sqkm/sqmi minimum cell size. Analog modem equivalent uplink theoretically possible.

That's DVB. That's an executive summary for a digital TV standard.

Not sure if I entire understand what you're saying.

Do you mean to suggest this would work well for digital video broadcasting (or equivalent to it)?

If so, this is what I have been theorizing as a potential future step for Starlink. Once they get the hardware costs down or offer basic versions that are good enough to receive a multicast signal and limited uplink (basic stuff like authentication, etc), they could start providing an equivalent to DirectTV or Cable TV.

I'm making the assumption that multi-casting a set of entertainment channels would be relatively inexpensive, and putting aside the question about the value of non-on-demand content for the moment...

This would create competition for incumbents and more options for the consumer.

Perhaps more importantly for Musk, this would give him the ability to create a media platform that won't be inhibited/constrained/censored by what he and his peers refer to as "legacy media". His recent actions/behavior (twitter, disney lawsuit/buyout, Murdoch/Tucker/Fox relationships, etc) suggest to me that this is his plan.

Whether or not you like him or think he and his companies deserve it, it's pretty obvious that they are being targeted by big-media and politicians, and constantly criticized and attacked. Antisemitism, Tesla shorting and "recall" news 24/7 , bankrupting Twitter, Starship failures, and so on...

He has FU money and it's obviously personal to him (Disney lawsuit), so why not?

"Give it a second! It's going to space. Can you give it a second to get back from space?"

Finally that joke is accurate.

https://youtu.be/PdFB7q89_3U?feature=shared

Classic.

I thought this joke already was accurate because they were on a plane and the WiFi on a plane usually is powered by satellite internet.

Sort of. At that point he's talking about people on their phones. He segues to planes and inflight WiFi just afterward.

While the bandwidth numbers seem terrible given this is from an entire beam at it's peak and beams are wide, this is super useful for things like sms where bandwidth is not a concern. At 17 Mb/s you can have thousands of simultaneous sms sends without issue

Yeah, it could be god sent for natural disasters and truly remote locations. But it is not replacement for regular mobile service.

For emergencies in truly remote locations. In a natural disaster, you have everybody at once refreshing news and checking in on friends and family that even undamaged networks could struggle.

When the network has broken down you'd better be prepared to have teams fixing what is fixable, and the ability to deploy pop-up cells on the ground. If you have skimped on that preparation betting on satellite cells to save the day the contribution of Starlink to disaster preparedness might end up being a net negative.

That being said, pop-up cells on a startlink as their backhaul could become huge in disaster preparedness. Some contract scheme for standby basestations might actually become a big component of the Starlink business model. The good news is that all talk to regular phones can't overlap with regular starlink frequencies, so unless it blocks some other bottlenecks like SDR DSP capacity it won't compete with regular connections (certainly won't have a meaningful impact on orbital backbone load)

I am thinking true disasters, where a simple message with your location can save lives.

I believe it should be possible to disable all communication except basic sms and emergency communication like 911 or similar can be accessed without SIM.

Surely this is an ideal usecase for IP multicast? Given that SpaceX controls effectively the entire LEO retail internet at the moment they’re in an ideal position to push a standard for multicasting emergency or regional updates.

You are talking about layer 3 while people are talking about layer 2.

Iridium should be worried.

There is a 3GPP standard for satellite to phone connectivity which Iridium is adopting:

https://www.iridium.com/project-stardust/

Their 66 satellites are going to support a much lower aggregate constellation throughput and spot beam count vs StarLink. They’re fundamentally constrained by lift costs and low constellation satellite count.

Iridium has 48 spot beams per satellite each covering 250 miles. Each StarLink cell covers ~15 miles with a similar spot beam count, with 5,442 satellites currently operational (as of this comment).

https://planet4589.org/space/con/star/stats.html

(Disclosure: StarLink customer, no other affiliation)

Most of those sats don't support direct to cell though. But more will come of course.

And are the spot beams for direct to cell the same in size and quantity?

Good question. I could not find the cell size specifically for the LTE coverage, and agree it will take time for the constellation to turn over to maximize the direct to phone capability. Regardless, SpaceX launches more StarLink satellites in three flights (~69) than Iridium has in its entire constellation.

I hope there's some broadcast stuff planned (does cellular support multicast like that?). So I can just point my phone at the sky and get some news/weather/traffic updates "off-line". Maybe a radio station or two? It's pretty impressive what can fit into 32kbps (or less!) these days.

Yes, that's how SMS emergency alerts work

https://en.wikipedia.org/wiki/Cell_Broadcast

> is part of the 2G, 3G, 4G LTE (telecommunication) and 5G standards

Interesting as Canada's system only works on LTE or higher (we still have 3G here).

I camped on 3G for a while because they kept sending out Amber Alerts at the "Presidential" level for custody disputes. Gov repeatedly denied any issue but haven't sent any for a while. Either people stopped "abducting" their own kids or they changed their threshold-to-blast.

Was your 3G on CDMA2000 rather than the 3GPP UMTS/WCDMA/HSDPA standards? That could account for the difference

One of our two big networks was, the other was not.

Viasats service supported this via USB plug in drive on the modem to load some content. Don't think it was released out of beta.

Hmm, but SMS rely on the cellular tower protocol, basically being carried on the status messages that cellphones already constantly send/receive anyway - they don't use the IP (at least until the tower).

So I'm not even sure they can be sent/received by satellite ??

Starlink is using 5G, a cellular tower protocol. The only other option would be WiFi which can not do long distance, at least without both ends being designed for it (which a cellphone is not).

One only could wonder what SpaceX Starshield [1] capabilities, are they theoretically able to sniff mobile traffic across whole planet ? FISA [2] over our heads, and not just somewhere at junction points. Fucking scary.

[1] https://en.wikipedia.org/wiki/SpaceX_Starshield

[2] https://en.wikipedia.org/wiki/Foreign_Intelligence_Surveilla...

Yes

I suppose this is download speed. what about upload speed?

Correction: It's 16 Megabits/s which is 2 MB/s.

Still impressive either way.

Did you mean to correct the number or the unit? Because a lowercase b generally refers to bits not Bytes already

The screenshot for the original tweet explicitly states that the original unit was Megabits.

The original screenshot and the titles would already be in agreement then:

Mb/s = (M)ega(b)its / (s)econd

MB/s = (M)ega(B)ytes / (s)econd

It's like how mm is (m)illi(m)eter and Mm is (M)ega(m)eter or (s)econds vs (S)iemens - case matters in units.

Thanks for the clarification. I didn't know this.

For units that are commonly used, I'd like to add:

Nm vs nm, which are (N)ewton-meter (Newton times meter, a measure of torque) or (n)anometer (10^-9 meter)

How exactly is this possible? What is the technology receiver based on? Where can I learn more about this?

What exact model of Samsung Phones have this?

It's just a regular 4G phone. They got LTE base stations up on the satellites. Actually, I'm not that surprised that they got the downlink working but I also would love to learn abut the challenges they faced while trying to receive a clean signal from a regular cellphone 600+km away.

Cellphones' transmit power is severely limited due to a) proximity to human brain b) battery considerations.

I imagine it also requires a clear view of the sky. That's how any satellite phone tech I ever laid hands on worked. I'd be astonished if they got it also working indoors. That'd be just pure magic.

https://www.starlink.com/business/direct-to-cell

https://arstechnica.com/gadgets/2023/10/spacex-details-starl...

EDIT: Just to be clear, the link says nothing about the return channel but I imagine they wouldn't have made this announcement unless they got the return channel working as well.

Nope, hype is everywhere in 2024

Unfortunately global coverage is not guaranteed. [0][1]

[0] https://www.cnbc.com/2024/02/24/house-china-committee-elon-m...

[1] https://apnews.com/article/spacex-ukraine-starlink-russia-ai...

[2] https://www.reuters.com/world/europe/russia-using-thousands-...

Unfortunately you're spreading truth mixed with disinformation.

This is a product for carriers. Not consumers. You can't buy it. Not just because you don't operate a carrier.

I was referring to the constellation itself, not any particular access method.

The US Department of Defense could easily obtain smartphone reception capability if they don't already have it. My point was that their coverage would be just as spotty either way.

Vietnam and Taiwan want 51% of starlink. South Africa 30%

The Feds still haven't issued a sanctions waiver for Crimea and 2014 occupied Donestsk and Lughansk. They bought unrestricted dishes instead.

Ukrainians think a whitelist is beyond them after asking for service beyond the frontline for over a year.

For the Feds they'll have federal Esims and the traffic will be forwarded to their cell core.

Spectrum issue disputes with other countries are a State Department & Commerce Department issue.

If they want SpaceX to transmit illegally regardless they know what to do.

Sorry my eyes are too bad to read the Image, was there a latency value or was this just a Broadcast? I found gaming and voip difficult with satellite Internet due to high latency.

How? WiFi? LTE? Is there anything else?

LTE. There's nothing we haven't seen here before.

What about stock iPhone?

0Mb/s

You must be holding it wrong...

When will we be able to watch 4k porn in remote areas?

That assumes you 'll be carrying a 4k TV with you

Applications for such type of tech are usually

military (is China's Navy moving in the Pacific).

commercial (where I my oil tanker in relation to the storm), or

post-event (let's say tsunami or tornado. Electricity might be down, where to send ambulances and search for survivors)

Those scenarios are mostly covered. Military has its own communication systems. (And satellite tracking for the navy) Weather - you can already receive precise satellite view of storms wherever you want.

Interesting. Why do you think so? That would make the whole New Space economy irrelevant.

https://professionalprograms.mit.edu/blog/technology/what-is...

I'm not sure what you're asking about. Weather satellites existed for a long time https://en.wikipedia.org/wiki/Weather_satellite

For navy movement, spy satellites already existed in the 50s and got magnitudes better since then. https://en.wikipedia.org/wiki/Reconnaissance_satellite

They want "apps" apparently.

Sounds like you already can, they just proved it, but you're going to have to watch the same video as everyone else.

I just realised that unless there's some capacity to upload, the title essentially describes.. TV.

You've been able for years, with regular starlink. Of course you need a dish antenna.

If you download it first you should be able to do it now. Streaming though... not so much. ;)

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