6 ms·

Oh, ok. But 22km is still a lot more than a typical 4G/5G urban cell. It's basically the size of a city. Whereas I can spot multiple stations in my city if I go

Oh, ok. But 22km is still a lot more than a typical 4G/5G urban cell. It's basically the size of a city. Whereas I can spot multiple stations in my city if I go for a 5-10 minute walk.

wmf 4y ago
Yes, the density of satellite is far lower than urban cellular which is why no one is pitching satellite for urban customers.
- colejohnson66 4y ago
  That, and latency. Or has that improved in the last decade?
  - Dylan16807 4y ago
    I wouldn't care about 40ms of latency for my phone. If by "last decade" you're comparing against geostationary, then yes. The satellites are roughly a hundred times closer.
  - deepdriver 4y ago
    Starlink latency is somewhere around 50ms on average according to friends, more than adequate for e.g. online multiplayer first-person shooters.
    - Faark 4y ago
      Sounds about right. Here are some other stats, in case someone wants sth more authoritative than someones friends: https://www.ookla.com/articles/starlink-hughesnet-viasat-performance-q2-2021 https://www.ookla.com/articles/starlink-hughesnet-viasat-per...
  - smoldesu 4y ago
    Starlink gets 40-150ms, more often erring on the faster side. If they can get their peak load under control, I don't think I'd ever pine for hardwired internet again.
  - krisoft 4y ago
    > Or has that improved in the last decade? Yes. Starlink satelites are at low earth orbit, much much closer than the geosyncronous orbits communication satelites a decade ago had to be at. Distance is latency because the radio waves can “only” propagate at the speed of light. The shorter the trip the faster the signals can make it.
  - PeterisP 4y ago
    Latency is big issue for geostationary satellites - the ones at which you can aim a dish at a fixed point in the sky - which have to be very far away from Earth to be geostationary, 35000 km above surface, unlike Starlink satellites which are just 550km above ground.
    - AtlasBarfed 4y ago
      Just to underline the point, starlink satellites are two orders of magnitude closer, and far more numerous.
mhandley 4y ago
In principle you've got spatial diversity at both ends - on the ground and in space. I don't mean full duplex - I mean that the same area on the ground can in principle be covered by multiple Starlink satellites simultaneously using the same frequencies, so long as the satellites are not close together. The receiving phased array can separate the multiple signals just as it could if you used a steerable parabolic dish, but in software. Of course there may not be enough satellites launched yet to take advantage of this, but eventually there should be.
- wmf 4y ago
  I don't think the FCC will ever allow that config due to interference with GSO.
  - krisoft 4y ago
    How will two starlink satelite communicating with a single ground receiver cause interference for GSO communications?
    - wmf 4y ago
      They're on the same frequency band and traditional satellite dishes can pick up some amount of off-axis interference. Assuming constant power per beam, more beams (Nco) eventually overwhelm traditional receivers.
sgtnoodle 4y ago
There's a ton of very clever stuff going on with modern RF modulations. For example, each client terminal will have a unique pseudo-randomization key, and transmissions are modulated by that key. That evenly distributes the transmission across the spectrum. To someone without the key, it appears to be random noise. Multiple transmissions can occur simultaneously on the same spectrum with different keys, without necessarily interfering with each other. Also, that 22km beam isn't going to be uniform, but rather higher gain at the center, and below some power threshold at the peripheral.
- wmf 4y ago
  CDMA doesn't increase capacity because the N codes have to each use 1/Nth the rate. It fell out of favor around 15 years ago because it doesn't allow one transmitter to temporarily use the whole channel, which is advantageous for data traffic.
- jcrawfordor 4y ago
  Spread spectrum methods are not magic, they do not manufacture new spectrum. As you get a larger number of simultaneous spread spectrum users the apparent "noise floor" (actually other spread spectrum transmissions) becomes higher and higher until the achievable data rate approaches zero. This isn't to say that the use of spread spectrum methods doesn't have benefits, but it doesn't change the fundamental concepts. Bluetooth, for example, uses FHSS but will still suffer from contention in very noisy environments.
- midoridensha 4y ago
  >That evenly distributes the transmission across the spectrum. To someone without the key, it appears to be random noise. I wonder if this is why SETI hasn't found any alien communications: they invented spread-spectrum communications and it all looks like noise to us.
  - ncmncm 4y ago
    SETI participants recognized early that we would only ever be able to pick up signals meant for us. So, those would not look like noise. It is why few take it seriously. Why would anybody be putting that much effort into trying to get our attention?

Oh, ok. But 22km is still a lot more than a typical 4G/5G urban cell. It's basically the size of a city. Whereas I can spot multiple stations in my city if I go for a 5-10 minute walk.

wmf 4y ago

Yes, the density of satellite is far lower than urban cellular which is why no one is pitching satellite for urban customers.

colejohnson66 4y ago
That, and latency. Or has that improved in the last decade?
- Dylan16807 4y ago
  I wouldn't care about 40ms of latency for my phone. If by "last decade" you're comparing against geostationary, then yes. The satellites are roughly a hundred times closer.
- deepdriver 4y ago
  Starlink latency is somewhere around 50ms on average according to friends, more than adequate for e.g. online multiplayer first-person shooters.
  - Faark 4y ago
    Sounds about right. Here are some other stats, in case someone wants sth more authoritative than someones friends: https://www.ookla.com/articles/starlink-hughesnet-viasat-performance-q2-2021 https://www.ookla.com/articles/starlink-hughesnet-viasat-per...
- smoldesu 4y ago
  Starlink gets 40-150ms, more often erring on the faster side. If they can get their peak load under control, I don't think I'd ever pine for hardwired internet again.
- krisoft 4y ago
  > Or has that improved in the last decade? Yes. Starlink satelites are at low earth orbit, much much closer than the geosyncronous orbits communication satelites a decade ago had to be at. Distance is latency because the radio waves can “only” propagate at the speed of light. The shorter the trip the faster the signals can make it.
- PeterisP 4y ago
  Latency is big issue for geostationary satellites - the ones at which you can aim a dish at a fixed point in the sky - which have to be very far away from Earth to be geostationary, 35000 km above surface, unlike Starlink satellites which are just 550km above ground.
  - AtlasBarfed 4y ago
    Just to underline the point, starlink satellites are two orders of magnitude closer, and far more numerous.

mhandley 4y ago

In principle you've got spatial diversity at both ends - on the ground and in space. I don't mean full duplex - I mean that the same area on the ground can in principle be covered by multiple Starlink satellites simultaneously using the same frequencies, so long as the satellites are not close together. The receiving phased array can separate the multiple signals just as it could if you used a steerable parabolic dish, but in software. Of course there may not be enough satellites launched yet to take advantage of this, but eventually there should be.

wmf 4y ago
I don't think the FCC will ever allow that config due to interference with GSO.
- krisoft 4y ago
  How will two starlink satelite communicating with a single ground receiver cause interference for GSO communications?
  - wmf 4y ago
    They're on the same frequency band and traditional satellite dishes can pick up some amount of off-axis interference. Assuming constant power per beam, more beams (Nco) eventually overwhelm traditional receivers.

sgtnoodle 4y ago

There's a ton of very clever stuff going on with modern RF modulations. For example, each client terminal will have a unique pseudo-randomization key, and transmissions are modulated by that key. That evenly distributes the transmission across the spectrum. To someone without the key, it appears to be random noise. Multiple transmissions can occur simultaneously on the same spectrum with different keys, without necessarily interfering with each other. Also, that 22km beam isn't going to be uniform, but rather higher gain at the center, and below some power threshold at the peripheral.

wmf 4y ago
CDMA doesn't increase capacity because the N codes have to each use 1/Nth the rate. It fell out of favor around 15 years ago because it doesn't allow one transmitter to temporarily use the whole channel, which is advantageous for data traffic.
jcrawfordor 4y ago
Spread spectrum methods are not magic, they do not manufacture new spectrum. As you get a larger number of simultaneous spread spectrum users the apparent "noise floor" (actually other spread spectrum transmissions) becomes higher and higher until the achievable data rate approaches zero. This isn't to say that the use of spread spectrum methods doesn't have benefits, but it doesn't change the fundamental concepts. Bluetooth, for example, uses FHSS but will still suffer from contention in very noisy environments.
midoridensha 4y ago
>That evenly distributes the transmission across the spectrum. To someone without the key, it appears to be random noise. I wonder if this is why SETI hasn't found any alien communications: they invented spread-spectrum communications and it all looks like noise to us.
- ncmncm 4y ago
  SETI participants recognized early that we would only ever be able to pick up signals meant for us. So, those would not look like noise. It is why few take it seriously. Why would anybody be putting that much effort into trying to get our attention?