5 ms·

This is such a cool problem. We already have a ton of Geo sat which can do this kind of communication but they are super expensive and have a limited bandwidth

by bargl 8y ago

This is such a cool problem. We already have a ton of Geo sat which can do this kind of communication but they are super expensive and have a limited bandwidth. These satellites will actually have a ton of limitations in how much data they can send around and how they'll have to balance out their signals. Geo are easier to point to because, well they don't move. But these are going to be moving and changing all the time so you'll have to connect to multiple satellites every day. I'm spit balling here but they'll probably be overhead for 10 minutes? Think about switching your router every 10 minutes. Or you get a rainy day and your signal clarity goes down. Or you are over the equator in a band that is used strictly for GEO. This is going to be a super cool problem to solve. And I'm sure I don't even understand the half of it. Edit: Sorry example of router is pretty bad. It's more like running your phone but you have to specifically aim your antenna at each tower that you're passing while driving. The complexity is moving nature of the network and the targeting nature of the antennas. I have 0 clue if phone signals are targeted but I believe they are radial signals and more like a beacon than a laser. Load balancing these can be a pain as well because if you get too much signal on an antenna it can actually block all signal.

reaperducer 8y ago
Or you are over the equator in a band that is used strictly for GEO. It's my understanding that this constellation is going to be significantly lower than GEO, so that's not a problem. Also, the dead zones are toward the poles, but those are mitigated in phase two.
- bargl 8y ago
  There is another constellation system (I forget the name) and they're going to have a partnership with GEO to beam signals for customers as the satellites pass over the equator.
tgtweak 8y ago
With about a thousand being in your horizon at any given time I don't think it'll be an issue to roam between them. In a Metropolitan area it's not rare to be around dozens of cell sites. Likewise cellular roaming is quite transparent.
- dr_orpheus 8y ago
  Yes, but your cell tower aren't moving around relative to each other. And in order to get the data rates that they need at the speed they need, the signals between the satellites will be more focused rf or laser communication. So all of the satellites have to constantly know which satellite is closest to them and how to point antennas and/or lasers.
  - ryanmarsh 8y ago
    Yes, but your cell tower aren't moving around relative to each other. Depends on the observer. If you move in a circle around a set of radios (driving around town) either you're stationary and the other radios are spinning or vice versa. Also, many satellites will share the same orbit, they will be stationary as far as each other are concerned.
    - dr_orpheus 8y ago
      True, the satellites within the orbital plane will remain close to stationary to each other. There will be some perturbations, but generally will be stationary relative to each other. In one of the plans I saw floating around the inter-satellite links within the orbital plane will basically be stationary laser links between the satellites. And the cross-links between the orbital planes will be done with phased array antennas so they can be electrically steered instead of physically steered.
phkahler 8y ago
>> Think about switching your router every 10 minutes. Your cell phone switches towers all the time while you're on the road. My cellphone (republic) switches from WiFi to cellular network mid-call if I'm on it when I leave a building. This is not a new problem.
- elteto 8y ago
  Satellites shooting lasers to talk to each other and create a global network in space is not a new problem? Damn, I guess we ran out of interesting problems to solve then /s.
- bargl 8y ago
  Well dang. That's a really good point. I remember early cell phones that would drop signal when running between towers. The hard part here is that you have to target the beam at the satellite. It's not a wide angle beam that's used it's a focused beam. (This might not be true based on what they implement) But for Geo it's a targeted beam. So this isn't a perfect corollary, and my example was pretty bad lol.
  - shaklee3 8y ago
    Geo satellites also do beamforming. See epic ng or quantum.
- gsich 8y ago
  >My cellphone (republic) switches from WiFi to cellular network mid-call if I'm on it when I leave a building. This is not a new problem. Networking technology switching is unrelated to a call, which always uses cellular.
  - throwahey 8y ago
    His network probably allows Wi-Fi calling and text messaging. So it would be switching.
  - thatfunkymunki 8y ago
TimTheTinker 8y ago
> Think about switching your router every 10 minutes. Cellular and WiFi AP roaming are solved problems. For SpaceX, this will be rather straightforward as the design specifies fixed ground stations that will handle negotiating/maintaining upstream connection(s). > Or you get a rainy day and your signal clarity goes down. That's more likely to be an issue, but having multiple satellites overhead, plus the fact that the constellation will be located in LEO (thus higher signal strength due to proximity) will help mitigate signal attenuation due to clouds/precipitation.
- bargl 8y ago
  Bleh - the router example was bad. Sorry I didn't think that one through too much. I did an update though. You're right on the signal degradation being significantly lower. But the LEO aspect means that there might be a higher percent of total loss due to rain (and probably adjacent signal interference). Either way it's a cool problem.
- kartickv 8y ago
  > Cellular and WiFi AP roaming are solved problems. While you may be right regarding the context in which you said this — satellites — as a blanket statement, that's not true: my smartphone loses Internet connectivity when I leave my house, and takes a few seconds before it connects to the cellular data network. I'm surprised that phones don't establish a backup 4G connection when Wifi signal strength decreases suddenly, but before it disconnects. This has been talked about for years, but for whatever reason it hasn't been deployed or doesn't work well, at least with Android P.
  - TimTheTinker 8y ago
    Sorry that wasn't clear. I meant cellular roaming between towers, and WiFi roaming between access points -- not roaming between the two technologies. It's currently possible to maintain a single connection (including IP address, open sockets, ip tables, etc.) while roaming between cell towers and WiFi APs. That's not true when switching carriers/providers/technologies, although I agree that would be a great next step for cell phones.
ryanmarsh 8y ago
My knowledge of satellite internet is circa 2004 when I was in the desert of Iraq. For the client premises equipment it's a hard problem but entirely solvable. Frequency hoping radios have been around a long time. Link bonding has been around a long time. Which satellites will be in view, where, and when is knowable. I think the harder part will be the backhaul... in space. I'm curious if they'll use beam shaping antennas for CPE. Surely they won't ship antennas with moving parts right? Also I'm curious about the power requirements of the CPE. Another problem will be security. This is a known problem with satellite uplinks. They basically spray everyone's traffic all over God's green Earth and if you listen in you used to be able to grab lots of data right out of the sky. These days it should all be encrypted, even then some of the encryption was easily cracked.
- bargl 8y ago
  There is a startup called... googling... Kymeta. That is creating shape changing satellites for cars, planes, and ships. Encryption might be handled by default with the https nature of the web now. But it'll just make https even more important going forward. It would also leave a lot of meta data open to sniffing which I don't think people would want either.
  - shaklee3 8y ago
    Kymeta is not really a startup. They have been around for a very long time.
gsich 8y ago
>We already have a ton of Geo sat which can do this kind of communication but they are super expensive and have a limited bandwidth. And high delay, which is the main problem.
tortarga 8y ago
There was recently a video posted theorizing this here: https://www.youtube.com/watch?v=AdKNCBrkZQ4 https://www.youtube.com/watch?v=AdKNCBrkZQ4 Very interesting watch. Based off the paper: https://twitter.com/awm22/status/1044512585599602688 https://twitter.com/awm22/status/1044512585599602688
- bargl 8y ago
  This is awesome thanks.
jandrese 8y ago
Motorola solved this problem with its Iridium constellation back in the 90s. Handoff between satellites isn't really that hard. Your phone knows where it is and what birds are overhead (and which are about to appear/disappear) so they can adjust automatically. Routing through the satellite constellation gets kind of hairy, but is also solvable via orbital mapping and some arcane routing algorithms. The real trick is getting enough link margin with omni antennas to get good bandwidth. As fun as they would look, nobody wants a cell phone with a little cartoon satellite dish on top that whirls around to track birds passing overhead.
- stcredzero 8y ago
  The real trick is getting enough link margin with omni antennas to get good bandwidth. What about phased arrays? Also, why not have a completely different scale of ISPs? How about something the size of a soda vending machine or something the size of a suitcase which contains all the hardware for a very small scale internet service provider?
  - space_fountain 8y ago
    The latest rumors I'd heard was that was exactly the plan though still not at phone scale. The modem was supposed to be a pizza box sized piece of hardware with a phased array.
  - jandrese 8y ago
    Phased arrays are nice, but have a slight problem with being stupendously expensive. It's going to be hard to convince people to jump on board if the starter hardware pack is $20k.
- bargl 8y ago
  Kymeta is coming out with a directional flat antenna. It wouldn't suit for a phone but I don't think these are meant for phones. I was not saying cell phone would have spinny disks on the top. The last part is, where I think the real fun will emerge. Doing everything above but optimized based on the load of each satellite with a link budget computation involved will be cool. It may prove out that the optimization isn't needed but I think that kinda stuff is fun. https://www.kymetacorp.com/markets/connected-car/kalo-trek/ https://www.kymetacorp.com/markets/connected-car/kalo-trek/
axus 8y ago
A GPS receiver is constantly switching between the satellites in the GPS constellation. This sounds like that, on a bigger scale.
- isatty 8y ago
  Actually without proper filtering you do see large jumps in pose when you reacquaire satellites. Solved problem and the routing example is not ideal, but yeah.
Scoundreller 8y ago
The bandwidth of geosats can be vastly improved with spotbeams: https://www.montanasatellite.com/support/satellite-footprints-ka-band/ https://www.montanasatellite.com/support/satellite-footprint...

by bargl 8y ago

reaperducer 8y ago

Or you are over the equator in a band that is used strictly for GEO. It's my understanding that this constellation is going to be significantly lower than GEO, so that's not a problem. Also, the dead zones are toward the poles, but those are mitigated in phase two.

bargl 8y ago
There is another constellation system (I forget the name) and they're going to have a partnership with GEO to beam signals for customers as the satellites pass over the equator.

tgtweak 8y ago

With about a thousand being in your horizon at any given time I don't think it'll be an issue to roam between them. In a Metropolitan area it's not rare to be around dozens of cell sites. Likewise cellular roaming is quite transparent.

dr_orpheus 8y ago
Yes, but your cell tower aren't moving around relative to each other. And in order to get the data rates that they need at the speed they need, the signals between the satellites will be more focused rf or laser communication. So all of the satellites have to constantly know which satellite is closest to them and how to point antennas and/or lasers.
- ryanmarsh 8y ago
  Yes, but your cell tower aren't moving around relative to each other. Depends on the observer. If you move in a circle around a set of radios (driving around town) either you're stationary and the other radios are spinning or vice versa. Also, many satellites will share the same orbit, they will be stationary as far as each other are concerned.
  - dr_orpheus 8y ago
    True, the satellites within the orbital plane will remain close to stationary to each other. There will be some perturbations, but generally will be stationary relative to each other. In one of the plans I saw floating around the inter-satellite links within the orbital plane will basically be stationary laser links between the satellites. And the cross-links between the orbital planes will be done with phased array antennas so they can be electrically steered instead of physically steered.

phkahler 8y ago

>> Think about switching your router every 10 minutes. Your cell phone switches towers all the time while you're on the road. My cellphone (republic) switches from WiFi to cellular network mid-call if I'm on it when I leave a building. This is not a new problem.

elteto 8y ago
Satellites shooting lasers to talk to each other and create a global network in space is not a new problem? Damn, I guess we ran out of interesting problems to solve then /s.
bargl 8y ago
Well dang. That's a really good point. I remember early cell phones that would drop signal when running between towers. The hard part here is that you have to target the beam at the satellite. It's not a wide angle beam that's used it's a focused beam. (This might not be true based on what they implement) But for Geo it's a targeted beam. So this isn't a perfect corollary, and my example was pretty bad lol.
- shaklee3 8y ago
  Geo satellites also do beamforming. See epic ng or quantum.
gsich 8y ago
>My cellphone (republic) switches from WiFi to cellular network mid-call if I'm on it when I leave a building. This is not a new problem. Networking technology switching is unrelated to a call, which always uses cellular.
- throwahey 8y ago
  His network probably allows Wi-Fi calling and text messaging. So it would be switching.
- thatfunkymunki 8y ago

TimTheTinker 8y ago

> Think about switching your router every 10 minutes. Cellular and WiFi AP roaming are solved problems. For SpaceX, this will be rather straightforward as the design specifies fixed ground stations that will handle negotiating/maintaining upstream connection(s). > Or you get a rainy day and your signal clarity goes down. That's more likely to be an issue, but having multiple satellites overhead, plus the fact that the constellation will be located in LEO (thus higher signal strength due to proximity) will help mitigate signal attenuation due to clouds/precipitation.

bargl 8y ago
Bleh - the router example was bad. Sorry I didn't think that one through too much. I did an update though. You're right on the signal degradation being significantly lower. But the LEO aspect means that there might be a higher percent of total loss due to rain (and probably adjacent signal interference). Either way it's a cool problem.
kartickv 8y ago
> Cellular and WiFi AP roaming are solved problems. While you may be right regarding the context in which you said this — satellites — as a blanket statement, that's not true: my smartphone loses Internet connectivity when I leave my house, and takes a few seconds before it connects to the cellular data network. I'm surprised that phones don't establish a backup 4G connection when Wifi signal strength decreases suddenly, but before it disconnects. This has been talked about for years, but for whatever reason it hasn't been deployed or doesn't work well, at least with Android P.
- TimTheTinker 8y ago
  Sorry that wasn't clear. I meant cellular roaming between towers, and WiFi roaming between access points -- not roaming between the two technologies. It's currently possible to maintain a single connection (including IP address, open sockets, ip tables, etc.) while roaming between cell towers and WiFi APs. That's not true when switching carriers/providers/technologies, although I agree that would be a great next step for cell phones.

ryanmarsh 8y ago

My knowledge of satellite internet is circa 2004 when I was in the desert of Iraq. For the client premises equipment it's a hard problem but entirely solvable. Frequency hoping radios have been around a long time. Link bonding has been around a long time. Which satellites will be in view, where, and when is knowable. I think the harder part will be the backhaul... in space. I'm curious if they'll use beam shaping antennas for CPE. Surely they won't ship antennas with moving parts right? Also I'm curious about the power requirements of the CPE. Another problem will be security. This is a known problem with satellite uplinks. They basically spray everyone's traffic all over God's green Earth and if you listen in you used to be able to grab lots of data right out of the sky. These days it should all be encrypted, even then some of the encryption was easily cracked.

bargl 8y ago
There is a startup called... googling... Kymeta. That is creating shape changing satellites for cars, planes, and ships. Encryption might be handled by default with the https nature of the web now. But it'll just make https even more important going forward. It would also leave a lot of meta data open to sniffing which I don't think people would want either.
- shaklee3 8y ago
  Kymeta is not really a startup. They have been around for a very long time.

gsich 8y ago

>We already have a ton of Geo sat which can do this kind of communication but they are super expensive and have a limited bandwidth. And high delay, which is the main problem.

tortarga 8y ago

There was recently a video posted theorizing this here: https://www.youtube.com/watch?v=AdKNCBrkZQ4 https://www.youtube.com/watch?v=AdKNCBrkZQ4 Very interesting watch. Based off the paper: https://twitter.com/awm22/status/1044512585599602688 https://twitter.com/awm22/status/1044512585599602688

bargl 8y ago
This is awesome thanks.

jandrese 8y ago

Motorola solved this problem with its Iridium constellation back in the 90s. Handoff between satellites isn't really that hard. Your phone knows where it is and what birds are overhead (and which are about to appear/disappear) so they can adjust automatically. Routing through the satellite constellation gets kind of hairy, but is also solvable via orbital mapping and some arcane routing algorithms. The real trick is getting enough link margin with omni antennas to get good bandwidth. As fun as they would look, nobody wants a cell phone with a little cartoon satellite dish on top that whirls around to track birds passing overhead.

stcredzero 8y ago
The real trick is getting enough link margin with omni antennas to get good bandwidth. What about phased arrays? Also, why not have a completely different scale of ISPs? How about something the size of a soda vending machine or something the size of a suitcase which contains all the hardware for a very small scale internet service provider?
- space_fountain 8y ago
  The latest rumors I'd heard was that was exactly the plan though still not at phone scale. The modem was supposed to be a pizza box sized piece of hardware with a phased array.
- jandrese 8y ago
  Phased arrays are nice, but have a slight problem with being stupendously expensive. It's going to be hard to convince people to jump on board if the starter hardware pack is $20k.
bargl 8y ago
Kymeta is coming out with a directional flat antenna. It wouldn't suit for a phone but I don't think these are meant for phones. I was not saying cell phone would have spinny disks on the top. The last part is, where I think the real fun will emerge. Doing everything above but optimized based on the load of each satellite with a link budget computation involved will be cool. It may prove out that the optimization isn't needed but I think that kinda stuff is fun. https://www.kymetacorp.com/markets/connected-car/kalo-trek/ https://www.kymetacorp.com/markets/connected-car/kalo-trek/

axus 8y ago

A GPS receiver is constantly switching between the satellites in the GPS constellation. This sounds like that, on a bigger scale.

isatty 8y ago
Actually without proper filtering you do see large jumps in pose when you reacquaire satellites. Solved problem and the routing example is not ideal, but yeah.

Scoundreller 8y ago

The bandwidth of geosats can be vastly improved with spotbeams: https://www.montanasatellite.com/support/satellite-footprints-ka-band/ https://www.montanasatellite.com/support/satellite-footprint...