Looking forward to a future Starlink+Apple/Google collab.
Dunno what frequency this is running at, but if it’s in the 10s of GHz, I’m assuming licensing doesn’t get tooooo pricey given how problematic it is on land-to-land links.
It works with existing 4G/LTE phones, so it will be using the standard 4G/LTE bands, which run up to 2.6 Ghz.
Presumably that's why SpaceX needs to ride on existing mobile operators: they already own LTE spectrum and can allocate a chunk of it for satellite services. It would be a lot of work (and cost) for SpaceX to go out and buy LTE spectrum in every country they want to operate in.
Sacrificing a chunk of that precious spectrum is huge though. Is LTE flexible enough to run some form of on-demand TDM between multiple base stations on top of it? Can it operate smaller cells on the same channels within the range of the larger cell, forcing the smaller cell to make do with other parts of the spectrum while the larger calls dibs?
Afaik older cellular protocols were relying on zero overlap between base stations serving the same frequencies, leading to a nice coloring problem that would seriously suffer if someone tried to fit in LEO cells.
I'm no LTE expert, but I'm pretty sure that it handles overlap: you can run LTE diagnostic apps on Android that will display all the visible base stations - often many are visible, sometimes 3 or more on the same band. Your phone looks at what's available and picks a combination with the best signal strength (sometimes it will connect on 2 or 3 different bands simultaneously with carrier aggregation).
But even then, most carriers have many bands/channels (EARFCNs) available - and presumably only a small slice of bandwidth is needed for this service considering it's (initially) only for text messages. Finding 5 Mhz on one of the higher LTE frequencies wouldn't be so hard for many carriers, even if it does need an exclusive channel.
> Apple/Google don't hold any RF spectrum rights worldwide...
yet. Apple (and android baseband suppliers, “Google” may be the wrong name to mention here), have the ability to take relatively worthless spectrum and make it widely useful in a way nobody else can.
I wonder how spectrum allocation works for C-Band satellite broadcasters that just blast continents with their signals. Grandfathered?
Most satellite-y things don’t and Starlink’s direct to cell won’t either.
Hence why the spectrum should be pretty cheap (along with its incredible susceptibility to obstructions… which is less of an issue when you’re going roughly “up” without pesky considerations like curvature of the earth)
And you do get a ton of gain with a small antenna at those high frequencies.
Me too, but at slower data rates. At 550km above, that’s still a big signal loss by inverse square law. Problem with slow data rates is that they clog up the channels.
Phased arrays work without having to repoint, but they don't overcome lack of incidence (insolation?)
(e.g. we can't build a solar panel that works perpendicular to the sun (or nearly perpendicular) using phased array technology because there just isn't much solar radiation hitting the "dish" in the first place)
SpaceX already works with Google, where Google allows Starlink to use its datacenters' network connectivity for downlink, while Google gets to use Starlink for data transfer.
Dunno what frequency this is running at, but if it’s in the 10s of GHz, I’m assuming licensing doesn’t get tooooo pricey given how problematic it is on land-to-land links.