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Latency's not going to be a problem. What is going to be a problem is what nobody is talking about: LEO satellites move. This means the downlink antenna has to

Latency's not going to be a problem. What is going to be a problem is what nobody is talking about: LEO satellites move. This means the downlink antenna has to have motors and move too, or it has to be a phased array and be expensive.

diminoten 8y ago
That's the innovation this is taking advantage of -- the downlink antenna will be tiny and can be embedded. This is a new market, not entering into an existing market.
- dreamcompiler 8y ago
  I'm sorry but you are incorrect. You cannot innovate your way around the laws of physics. Do you want 5 Mbps from a LEOSAT? Fine, you need a pointable antenna. An Iridium-style omni antenna cannot accomplish this. The S/N ratio is simply too low.
  - diminoten 8y ago
    Sorry, but there are no laws of physics preventing innovation in the antenna space.
    - dreamcompiler 8y ago
      I suggest you study information theory and antenna theory. What you are suggesting is theoretically impossible. If a satellite could paint the continent with a megawatt, it might work. But satellites transmit with tens of watts, which gets spread over a large geographic area. The ground antenna must be pointed for decent bandwidth, either physically (with motors) or virtually (phased array) to achieve the requisite S/N ratio.
      - shaklee3 8y ago
        This is correct. Basic antenna theory covers C/N and how it relates to antenna size. There's no magic allowed.
      - diminoten 8y ago
        > What you are suggesting is theoretically impossible But then... > it might work Are you an expert in this field? I'm guessing no based on this exchange...
        dragonwriter 8y ago
        Your deceptive edits are...deceptive. The “it might work” was preceded with a hypothetical condition and then followed with the real condition. It wasn't “its theoretically impossible but it might work”, but, “its theoretically impossible; if satellites could carry transmitters two orders of magnitude more powerful than they actually can, it might work.”
        diminoten 8y ago
        That's not what "theoretically impossible" means. You literally just described a scenario where what I said would be theoretically possible, based on your own understanding of the technology, which is decidedly incomplete. You also didn't answer the question about your expertise, I'm assuming because your answer is, "No". Maybe leave the correcting of others to the actual experts...
        dragonwriter 8y ago
        > That's not what "theoretically impossible" means. Sure it is, if the hypothetical is pointing out a constraint on the boundaries of theoretical impossibility (or, in theory, if the hypothetical is itself possible to describe but theoretically impossible because of physical limits, though that doesn't appear to be the case here; there might be a theoretical lower limit on the size of a transmitter of the require power output or the supporting power system, but in theory there is no limit to the size of a satellite except the bound at which it becomes the primary because it's larger than the thing it is supposed to orbit.) > You also didn't answer the question about your expertise A careful examination of the thread will find that no such question was previously raised. There are more than two people on HN, so just because you get a response that doesn't make the person responding necessarily the person to whom you were responding. HN shows comment authors handles in case you ever need to know to whom it is you are responding, which you might want to do before attacking them based on assumptions about their identity.
- maccam94 8y ago
  It will not be tiny, but they are designing a pizza box sized phased array antenna with a target price of $100-300.
topspin 8y ago
> phased array and be expensive There isn't any question about the type of antenna. The details have been filed with the FCC. The antenna will be phased array. Obviously there is a high front loaded capital cost to developing a phased array transceiver for this system. The scale of the market, however, is vast; hundreds of millions of units. I believe the per unit cost of manufacturing these transceivers will be low due to this scale. I can't know that however, so we'll have to wait and see.
- dreamcompiler 8y ago
  Thanks. I suspected it would be PA, but I have not read the filing.
- shaklee3 8y ago
  Why hundreds of millions? At most this service will have a couple million people on the entire constellation if you want the speeds musk is saying. Otherwise, you have much lower speeds and cram more people, which is a trade-off all satellite technology has.
  - topspin 8y ago
    We can't compute credible figures at this point because a lot of the technical information is proprietary and the business model isn't known. I don't believe Elon has committed to any specific bandwidth; searching yields claims of "up to" 1 Gbps. Given the rates cited here[1] (20 Gbps/satellite) I seriously doubt that 1 Gbps is going to be offered at a price level that allows it to be widespread. More likely we'll see service offered in the 10s of Mbps. So the best we may achieve is some napkin level estimates. Let us assume 100 Mbps as a realistic subscriber rate. 12000 satellites[2] * 20 Gbps/satellite * 100/1 over-subscription (typical, see here[2]) / 100 Mbps = 240 million theoretical subscribers. Obviously every figure here is open to endless dispute, but we're in the right order of magnitude. I believe this is the scale Elon is thinking at; he's trying to fund interplanetary space travel with this. In any case there will need to be a couple mountains worth of transceivers for the plan to work, and making fixed function electronics at that scale is typically highly cost effective. [1] https://www.reddit.com/r/Starlink/comments/7xzkl5/starlink_satellite_bandwidth https://www.reddit.com/r/Starlink/comments/7xzkl5/starlink_s... [2] https://en.wikipedia.org/wiki/Starlink_(satellite_constellation) https://en.wikipedia.org/wiki/Starlink_(satellite_constellat... [3] http://www.ctcnet.us/wp-content/uploads/2014/02/CTC-ConnectivityPerformanceFactorsBrief0213141.pdf http://www.ctcnet.us/wp-content/uploads/2014/02/CTC-Connecti... "Cable modem and DSL providers often have a 100:1 or greater oversubscription ratio for residential users and a 50:1 ratio for business users."

diminoten 8y ago

That's the innovation this is taking advantage of -- the downlink antenna will be tiny and can be embedded. This is a new market, not entering into an existing market.

dreamcompiler 8y ago
I'm sorry but you are incorrect. You cannot innovate your way around the laws of physics. Do you want 5 Mbps from a LEOSAT? Fine, you need a pointable antenna. An Iridium-style omni antenna cannot accomplish this. The S/N ratio is simply too low.
- diminoten 8y ago
  Sorry, but there are no laws of physics preventing innovation in the antenna space.
  - dreamcompiler 8y ago
    I suggest you study information theory and antenna theory. What you are suggesting is theoretically impossible. If a satellite could paint the continent with a megawatt, it might work. But satellites transmit with tens of watts, which gets spread over a large geographic area. The ground antenna must be pointed for decent bandwidth, either physically (with motors) or virtually (phased array) to achieve the requisite S/N ratio.
    - shaklee3 8y ago
      This is correct. Basic antenna theory covers C/N and how it relates to antenna size. There's no magic allowed.
    - diminoten 8y ago
      > What you are suggesting is theoretically impossible But then... > it might work Are you an expert in this field? I'm guessing no based on this exchange...
      - dragonwriter 8y ago
        Your deceptive edits are...deceptive. The “it might work” was preceded with a hypothetical condition and then followed with the real condition. It wasn't “its theoretically impossible but it might work”, but, “its theoretically impossible; if satellites could carry transmitters two orders of magnitude more powerful than they actually can, it might work.”
        diminoten 8y ago
        That's not what "theoretically impossible" means. You literally just described a scenario where what I said would be theoretically possible, based on your own understanding of the technology, which is decidedly incomplete. You also didn't answer the question about your expertise, I'm assuming because your answer is, "No". Maybe leave the correcting of others to the actual experts...
        dragonwriter 8y ago
        > That's not what "theoretically impossible" means. Sure it is, if the hypothetical is pointing out a constraint on the boundaries of theoretical impossibility (or, in theory, if the hypothetical is itself possible to describe but theoretically impossible because of physical limits, though that doesn't appear to be the case here; there might be a theoretical lower limit on the size of a transmitter of the require power output or the supporting power system, but in theory there is no limit to the size of a satellite except the bound at which it becomes the primary because it's larger than the thing it is supposed to orbit.) > You also didn't answer the question about your expertise A careful examination of the thread will find that no such question was previously raised. There are more than two people on HN, so just because you get a response that doesn't make the person responding necessarily the person to whom you were responding. HN shows comment authors handles in case you ever need to know to whom it is you are responding, which you might want to do before attacking them based on assumptions about their identity.
maccam94 8y ago
It will not be tiny, but they are designing a pizza box sized phased array antenna with a target price of $100-300.

topspin 8y ago

> phased array and be expensive There isn't any question about the type of antenna. The details have been filed with the FCC. The antenna will be phased array. Obviously there is a high front loaded capital cost to developing a phased array transceiver for this system. The scale of the market, however, is vast; hundreds of millions of units. I believe the per unit cost of manufacturing these transceivers will be low due to this scale. I can't know that however, so we'll have to wait and see.

dreamcompiler 8y ago
Thanks. I suspected it would be PA, but I have not read the filing.
shaklee3 8y ago
Why hundreds of millions? At most this service will have a couple million people on the entire constellation if you want the speeds musk is saying. Otherwise, you have much lower speeds and cram more people, which is a trade-off all satellite technology has.
- topspin 8y ago
  We can't compute credible figures at this point because a lot of the technical information is proprietary and the business model isn't known. I don't believe Elon has committed to any specific bandwidth; searching yields claims of "up to" 1 Gbps. Given the rates cited here[1] (20 Gbps/satellite) I seriously doubt that 1 Gbps is going to be offered at a price level that allows it to be widespread. More likely we'll see service offered in the 10s of Mbps. So the best we may achieve is some napkin level estimates. Let us assume 100 Mbps as a realistic subscriber rate. 12000 satellites[2] * 20 Gbps/satellite * 100/1 over-subscription (typical, see here[2]) / 100 Mbps = 240 million theoretical subscribers. Obviously every figure here is open to endless dispute, but we're in the right order of magnitude. I believe this is the scale Elon is thinking at; he's trying to fund interplanetary space travel with this. In any case there will need to be a couple mountains worth of transceivers for the plan to work, and making fixed function electronics at that scale is typically highly cost effective. [1] https://www.reddit.com/r/Starlink/comments/7xzkl5/starlink_satellite_bandwidth https://www.reddit.com/r/Starlink/comments/7xzkl5/starlink_s... [2] https://en.wikipedia.org/wiki/Starlink_(satellite_constellation) https://en.wikipedia.org/wiki/Starlink_(satellite_constellat... [3] http://www.ctcnet.us/wp-content/uploads/2014/02/CTC-ConnectivityPerformanceFactorsBrief0213141.pdf http://www.ctcnet.us/wp-content/uploads/2014/02/CTC-Connecti... "Cable modem and DSL providers often have a 100:1 or greater oversubscription ratio for residential users and a 50:1 ratio for business users."