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.
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.
Damn, I guess we ran out of interesting problems to solve then /s.
Networking technology switching is unrelated to a call, which always uses cellular.
I've been using them for years and it works fine.
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.
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?
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.
Speak for yourself! ;)
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.
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.
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.
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.
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.
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.
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.
Very interesting watch.
Based off the paper: https://twitter.com/awm22/status/1044512585599602688
https://www.montanasatellite.com/support/satellite-footprint...
And high delay, which is the main problem.
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.
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.