A new firm says it can link satellites to ordinary smartphones | Hacker News Reader

A new firm says it can link satellites to ordinary smartphones

economist.com

50 pointssohkamyung52 comments

Every time you see a claim like this, remember the Shannon–Hartley theorem[1].

If you want to get a decent bandwidth in aggregate for your mobile network, you're going to need to consider:

* Maximize transmit Power: which is hard because phones are battery powered, and power is limited by law. Satellites are also battery powered.

* Maximize bandwidth: Also limited by rules and regulations.

* Maximize Directionality: If you have physically large antennas, you can direct your transmit power towards the receiver to make best use of it.

* Minimize Distance: Received signal power goes down the the square of he distance. Double the distance, and you get one quarter of the bandwidth, all other things being the same.

This proposal uses tiny existing antennas in phones, which means it must be making other tradeoffs. My guess is it seriously sacrifices the total throughput.

[1]: https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theore...

> Satellites are also battery powered.

I thought they have solar panels.

Also, don't phones and satellites use small antenna arrays to direct power in a certain direction?

I think the panels recharge a battery. Is the satellite always within line of sight of the sun?

Solar panels when illuminated by the sun, battery power while in the Earth's shadow.

To be low latency they need to be in a low orbit, so probably on battery power for a significant fraction of the time.

The batteries are powered by solar panels. In either case the same arguments apply - space is notoriously low power.

Phones can't use directional antennas, otherwise you'd have to point them at radio towers. Using phased array antennas in which directionality is software controlled, there's a trade off between size of antenna and how much you can focus the beam - it wouldn't work in a phone (and would be too expensive anyway).

Ok, but there is a lot of power to be saved. If you can prevent the beam from going in the "opposite" general direction, you can already save 50%. I'm not convinced there is nothing to be gained by using a small array.

Its just physically not feasible. For an antenna array with 2 dimensional beamforming you need an array of NxN antennas, which all have the dimension of a fraction of a wavelength, so we are talking about a not insignificant size. Additionally, to limit mutual coupling via substrate and stray radiation, you need certain distances. Third, you need to be careful to prevent grating lobes (side emissions of unwanted radiation).

And even then, you will need individually controlled phase shifters for each array element, adding cost, complexity and mostly negating energy savings.

Edit: All of that in addition to the problem that you need to know the location of the base station and have you array antenna roughly oriented towards it.

In addition to all the above, phones move a lot during a call. You'd need very good sensors to keep track of the phone's orientation in space. If you're only shooting for 50%, the sensors in phones are probably good enough, but what happens when the user puts their head between the phone and the base station? The phone could say "please rotate your body to reconnect call" but that would be a lousy user experience.

There are neat tricks to keep phased array antennas in alignment. One for example is to just send the signal back in the same direction you're receiving from. (ie. Same phase delays in every antenna element)

Then however much the phone is tumbling, you'll always be exactly sending the data in the right direction.

Turns out the problem is moot anyway - unless you have a huge antenna to get a really narrow beam, sub-degree positional errors won't make any impact.

Saving 50% gets you 3dB. You'll need something on the order of 20dB. The inverse-square law bites hard.

Space is notoriously expensive... until it isn’t. Launch costs have reduced by an order of magnitude and may reduce by another as full reuse becomes feasible. All of a sudden, you’re using near-commodity solar cells with a higher capacity factor (and more consistency) than on the ground. Power is thus not so expensive any more.

Industry rules of thumb are only good if the industry is stagnant.

And yet SpaceX still struggles to find launch volume.

I'm not sure what you're trying to say here. That SpaceX's launch business struggles to find enough customers, or that SpaceX's satellite business struggles to get enough launches to orbit?

Ironically both are sort of true... and I'm not sure how either of them respond to the post you replied to.

SpaceX has been struggling to get enough external customers recently, the launch market has been in a bit of a slump and external customers haven't yet substantially responded to the lowering launch costs.

SpaceX's Starlink constellation needs a huge number of launches, to the point where it seems at best barely feasible in both cost and launch volume to launch it on current rockets. They hope to fix this with their in-development starship rocket which should be able to launch an order of magnitude more satellites at a time (400 vs 60), at an order of magnitude less cost as a result of full re-usability and easier construction of the rocket.

Space isn't javascript. It takes years and many millions of dollars to build a sophisticated satellite, and SpaceX's market dominance didn't happen until last year. Most those who may want the take advantage of the lowered launch costs aren't yet in a position to do so

...which is why they're creating their own megaconstellation: to produce their own demand.

This has always been a conundrum for space launch: demand is, in the short term, very inelastic and the market is small, so if you reduce prices through reuse, you might actually reduce your own revenue if you're not careful. The way around it is to create your own demand.

Anyway, this new firm is an example of a new source of demand. This will provide additional launch volume.

While the cost of putting more solar panels and batteries in space is one limiting factor, the ability to reject heat in a near vacuum is another issue to consider. This is another thing which usually limits the practical power budget of things in space.

What you mean is either achieved with conventional high-gain antennas (Dishes, mostly) or with beamforming by either a passive, or in this case more likely, active phased array. TBH, I dont know of any commercial handsets doing so (albeit I am not that deep into the consumer market). On Base Stations, on the other hand, yes they are using this technology to improve reception and to limit inter-cell interference.

They also have batteries. When their orbit takes them into Earth's shadow, the solar panels stop working.

Reading your comment I immediately thought probably enough throughput to covertly track a phone. I thought maybe this company isn’t really trying to sell to the public but rather get some attention to their new tech before they ultimately sell it off to the government.

I'm pretty sure you can already track all phones from satellites already.

Phone initial handshakes with the tower are done at high power and are always identical, meaning you can get a ridiculous coding gain to detect them.

But starlink. Seriously how are they going to make it work?

I've wondered about that too, but their satellites are close to the ground - 620 miles vs 22,236 miles.

I don't know how far away the average cellular tower is, but I imagine line of sight could be a better signal than a closer occluded signal.

Wikipedia says cell tower range on hilly terrain can be 5 miles, while on flat ground it can be 30-45 miles (which is still over the horizon).

What I wonder about is how many phones per satellite is supportable.

Having been an amateur watcher of the last 20 years of satellite ventures, I find that going into the business of satellite internet/voice is only slightly less profit making than starting an airline.

There's something exciting/sexy about launching satellites, which may be why people so easily dump money into it. But from Iridium, Globalstar, Terrestar (anyone remember that one? Seem to be quite relevant here), I don't think anyone attempting to reach a broad consumer market has ever made big money, or even survived long term. For some reason, the customer growth factors in their profit models (at the offered service pricing) are always wrong by a few hundred %, yet they keep being believed. Maybe it's because VCs think that their desire for a strong signal on their yacht correspond's to the average person's willingness to pay.

Maybe ventures like Elon Musk's may break the mold with a different cost structure (while littering our outer space), but for a run of the mill satellite, odds are you're going to fail quite soon.

The best way to make money related to satellites is to be the entity that buys the initial satellite company after it goes bankrupt.

> I don't think anyone attempting to reach a broad consumer market has ever made big money, or even survived long term

Don't follow this market closely but sirius/xm might be one exception - not sure of their leverage position, but even if healthy one could argue to your point they don't reach consumers directly, but rather via intermediaries such as car and a/v equipment manufacturers.

My take on satellite is basically it's good for important but secondary network usage - anything that needs this should be fairly stable & constant beta provided good financials but looking for 'unicorn' style growth is probably mistaken as you mention.

I think for Elon Musk, developing space technology is the real business, and if the internet service generates cash flow, it would help defray the costs. If it happens to be profitable, that is just gravy.

Your argument would be better if you had numbers to back it up. What is the capital costs for the project? How much does the capital cost per year? How many customers do you expect they will have?

If Starlink is a 5 or 10 billion dollar project, that's $250-500M to service the capital. At $80 a month for service, you'd need ~500,000 subscribers to cover that cost. I think Starlink can get at least 500k subscribers and keep customers happy with bandwidth and latency.

Anyway, that's just napkin math, but might serve as a better foundation for thinking how likely the business model is to succeed.

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

As far as I can gleam from this report, they want to revitalize the old "bent pipe" model of satellite communication, where the sat only acts as a repeater . I am still very wary of it being feasible. While the track of BS->MS is feasible, albeit with a high transmission loss, i cannot fathom how they want to receive the <1W signal of the MS. Conventional way to pick up a signal below the noise level would be decorrelation, and while 3G/4G work on that principle, there would have to be additional information exchange between BS and Satellite. Additionally, for that to work the SATs have to be in LEO, and as they describe them as "massive"(most probably the high-gain antennas), there then will be massive atmospheric drag, requiring either frequent reboosting or replacing.

What's "BS" and "MS" here?

Mobile Station and Base Station. They're used widely in the GSM specs but more general now.

https://www.ques10.com/p/5206/gsm-network-architecture-1/

Base Station -> fixed site, radio tower, top of a building... Mobile Station -> smartphone, mobile router, car...

Figured it was base station vs mobile station

Got a link to the report?

After Looking at the company FAQ all I can say: What the hell?

---

https://ast-science.com/spacemobile/faqs/

* How does the technology work?

The technology is highly proprietary, and exactly how it works cannot be disclosed. We can say that our engineers and space scientists have designed an entirely new form factor and deployment method that significantly reduce the time and costs associated with manufacturing, launching and operating satellites. Our team also has worked – and continues to work – closely with mobile network operators to ensure compatibility with today’s wireless networks, including 5G.

* Do users need a satellite phone or special antenna?

No, SpaceMobile will be the first and only space-based network to work with standard mobile phones. No separate or specialized satellite hardware is required.

* Do you need clear line of sight to SpaceMobile satellites for connectivity?

No, our proprietary technology enables access to SpaceMobile from any location — even inside — regardless of visibility to the satellites on orbit.

Nah, it is just a stock pump and dump scheme for the gullible investors.

Experimental FCC licenses for AST & Science:

https://fcc.report/ELS/AST-Science/0908-EX-ST-2019

2207.87500000-2208.52500000 MHz FX 10.000000 W

https://fcc.report/ELS/AST-Science-LLC/0047-EX-CN-2019

2033.37500000-2033.62500000 MHz FX 10.000000 W 7100.000000 W P 0.00010000 % 250KG1W GMSK

2033.50000000- MHz FX 10.000000 W 7100.000000 W P 0.00010000 % 250KG1W GMSK

2207.87500000-2208.52500000 MHz FX 10.000000 W 7100.000000 W P 0.00010000 % 500KG1W GMSK

https://fcc.report/ELS/AST-Science-LLC/0884-EX-CN-2018

New 891.50000000-894.00000000 MHz FX 3847.000000 W 3847.000000 W M 1.20000000 % 2M50FXD OFDM

New 846.50000000-849.00000000 MHz FX 3847.000000 W 3847.000000 W M 1.20000000 % 2M50FXD OFDM

I can see a satellite transmitting powerfully to reach a phone on the ground.

But how are they going to pick up the transmission from a phone, which is incredibly low power and designed to be picked up from a maximum range of 70km.

The Wikipedia article also says that timing considerations give a maximum range of 35km. Which is a lot lower than the 2,000km of Low Earth Orbit.

No, the same Wikipedia says GSM in extended range can support calls up to 120km.

That it can, but IIRC it does so by relaxing the timing constraints and halving the number of slots in each channel.

Still leaves them with the interesting problem of the satellite necessarily seeing a lot of handsets at the same time; methinks even if all other engineering issues were magically resolved, they'd run out of bandwidth real fast. (Not to mention the regulatory hurdles.)

> I can see a satellite transmitting powerfully to reach a phone on the ground.

Yes, wouldn’t this just be like GPS?

I’m also not convinced the phone->satellite is practical/feasible.

‘Calls only’ maybe possible, as we have huge bandwidth to base station and calls require really small bandwidth. Also afaik 2g doesnt have strict timing requirements.

Low Earth Orbit has an altitude UP TO 2000 km. The ISS for example is at about 400 km.

If they placed their sat at 100 km (right at the limits of "space") maybe it would be possible to be in range of a cell phone.

I don't think it's feasible to have a satellite orbit at 100 km and not fall out of the sky in a few days due to atmospheric drag.

Even ISS at 300-400 km orbit has to be regularly reboosted because it's continuously losing altitude.

I'm trying to reconcile the fact this sounds like BS with the fact they just raised 110m from Vodaphone et al.

In this vodaphone press release[0] they say it's not just an investment but also a strategic partnership.

The founder is Abel Avellan. He previously ran Emerging Markets Communications, Inc. I can't tell if they are still in operation, but it looks like they have folded.

I found some old paid press releases[1] claiming they were going to revolutionize cloud computing in Africa with SpeedNet, boasting zero latency with 100mb/s transfer speeds over existing satellite links. Best I can tell, it was just a thin client. It is "zero" latency 100mb/s because it all runs on the same servers. Very deceptive.

There is a whole slew of related companies. They all seem to make use of paid press releases and similar promotional stunts.

They tend to be located in cheap rental offices in Florida, at addresses also used by hundreds of other corps.

I'm on my phone so I didn't go deep, but there is a clear pattern. Exaggerated announcements of technology breakthroughs, which never materializes.

I guess they upped their game and managed to put on a good enough show to get a sizeable investment.

I imagine it's an easier technical problem when the weak transmitter is in space, probably with a directional antenna, with no nearby sources of interference. All very much unlike a real environment.

[0] https://investors.vodafone.com/news-releases/news-release-de...

[1] https://www.businesswire.com/news/home/20120524005227/en/Eme...

Battery life on those phones is going to be /terrible/. Max TX power all the time?

> no escaping a mobile signal

That's a bizarre phrasing. Is it meant to be ironic?

Signal is something you want to have, not escape from.

Some folks like to switch off with plausible deniability

Dead batteries seem like a plausible excuse.

They might be referring to the (potential) human health issues those signals cause.

Are there any european companies riding the current wave of trying to build satellite internet? Or is it US only?

I think China is also looking at building a starlink-type network, although I don't have a link on hand.

OneWeb are partnered with Airbus although post-brexit they are no longer headquartered within EU (London and other cities around the world).

SES, an EU firm, is developing a medium earth orbit satellite network and would be well positioned to develop a LEO network.

https://archive.md/M0b2L

A new firm lies

Reply on news.ycombinator.com